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Herein, five N, S-co-doped carbocatalysts were prepared from different carbonaceous precursors, namely sawdust (SD), biochar (BC), carbon-nanotubes (CNTs), graphite (GP), and graphene oxide (GO) and compared. Generally, as the graphitization degree increased, the extent of N and S doping decreased, graphitic N configuration is preferred, and S configuration is unaltered. As peroxymonosulfate (PMS) activator for ciprofloxacin (CIP) removal, the catalytic performance was in order: NS-CNTs (0.037 min-1) > NS-BC (0.032 min-1) > NS-rGO (0.024 min-1) > NS-SD (0.010 min-1) > NS-GP (0.006 min-1), with the carbonaceous properties, rather than the heteroatoms content and textural properties, being the major factor affecting the catalytic performance. NS-CNTs was found to have the supreme catalytic activity due to its remarkable conductivity (3.38 S m-1) and defective sites (ID/IG = 1.28) with high anti-interference effect against organic and inorganic matter and varying water matrixes. The PMS activation pathway was dominated by singlet oxygen (1O2) generation and electron transfer regime between CIP and PMS activated complexes. The CIP degradation intermediates were identified, and a degradation pathway is proposed. Overall, this study provides a better understanding of the importance of selecting a suitable carbonaceous platform for heteroatoms doping to produce superior PMS activator for antibiotics decontamination. This work was supported by the Universiti Sains Malaysia, Research University Team (RUTeam) Grant Scheme (Grant Number: 1001/PJKIMIA/8580061).

Chemical recycling of poly (ethylene terephthalate) (PET) by depolymerization into monomers to recreate virgin-grade plastics is desirable; however, the energy inefficient separation and purification steps needed to obtain high-purity monomers result in poor overall economic feasibility at present. Herein, we present a one-step integrated process for partial depolymerization and upcycling of PET oligomers directly in to high-value product without any need for solvent recovery and purification. The key strategy for our approach is using multifunctional cleaving agents such as glycerol in the presence of ionic liquid as a catalyst for controlled partial depolymerization of PET via transesterification using N-Methyl-2-pyrrolidone (NMP) as solvent. The obtained depolymerized, oligomeric PET (DOPET) recyclate together with NMP and IL is a gel-like, ionic-conductive material, also termed as an “ionogel”, that has the potential to be used in energy storage applications or as mechanically robust electrical conductors. This is a one-step process requiring no extensive separation and purification of PET oligomers or distillation of solvent for recovery which further simplifies the recycling process while simultaneously increasing the value of the waste product. We have further investigated the effects of the choice and amount of cleaving agent on the molecular weight and branching of the DOPET oligomers and hence the properties of the upcycled end products. Moreover, we have also shown the versatility of the abovementioned process for controlled depolymerization of other condensation polymers such as polyamides, polyurethane, and even mixed polymer products to obtain high value functional materials. Submitted/Accepted version

Membrane technology is a key enabler for a circular pharmaceutical industry, but chemically resistant polymeric membranes for organic solvent nanofiltration (OSN) often suffer from lower-than-required performances. Recently, graphene-based laminated membranes using small-flake graphene oxide (SFGO) nanosheets open up new avenues for high-performance OSN, but their permeance toward high viscosity solvents is below expectation. To address this issue, we design hyperlooping channels using multiwalled carbon nanotubes (MWCNTs) intercalated within lanthanum(III) (La3+)-cross-linked SFGO nanochannels to form a ternary nanoarchitecture for low-resistant transport toward high viscosity solvents. At optimized MWCNT loading, the defect-free membrane exhibits 138 L m-2 h-1 bar-1 ethanol permeance at >99% rejections toward organic dyes, outperforming state-of-the-art graphene oxide (GO)-based membranes to date. Even butanol─with twice the viscosity of ethanol─exhibits a permeance no less than 60 L m-2 h-1 bar-1 at comparable rejection rates. Theoretical simulation suggests that La3+ cross-linking is critical and can create an intact architecture that brings size exclusion into play as the dominant separation mechanism. Also, MWCNT nanochannel offers at least 1.5-fold lower ethanol transport resistance than that of the GO nanochannel, owing to greater bulk freedom in orientating ethanol molecules. Overall, the hyperlooping architecture demonstrates ∼3-fold higher permeance than neat SFGO membrane for elevating OSN performances. Economic Development Board (EDB) Nanyang Technological University This work was supported by GSK-EDB Trust Fund (T.-H.B. and J.-M.L.) and the National Research Foundation of Korea (NRF) grant funded by the Korea government MSIT (T.-H.B.; Reference number: NRF-2021R1A2C3008570). K.Z. and Y.W. would like to acknowledge financial support from the Nanyang Environment and Water Research Institute (Core Fund), Nanyang Technological University, Singapore. K.G. would also like to acknowledge funding support from the Economic Development Board (EDB) of Singapore to the Singapore Membrane Technology Centre.

Organic electrochemical transistors (OECTs) have recently attracted attention due to their high transconductance and low operating voltage, which makes them ideal for a wide range of biosensing applications. Poly-3,4-ethylenedioxythiophene:poly-4-styrenesulfonate (PEDOT:PSS) is a typical material used as the active channel layer in OECTs. Pristine PEDOT:PSS has poor electrical conductivity and additives are typically introduced to improve its conductivity and OECT performance. However, these additives are mostly either toxic or not proved to be biocompatible. Herein, a biocompatible ionic liquid [MTEOA][MeOSO3] is demonstrated to be an effective additive to enhance the performance of PEDOT:PSS based OECTs. The influence of [MTEOA][MeOSO3] on the conductivity, morphology and the redox process of PEDOT:PSS are investigated. The PEDOT:PSS/[MTEOA][MeOSO3] based OECT exhibits high transconductance (22.3 ± 4.5 mS μm-1), high μC* (the product of mobility μ and volumetric capacitance C*) (283.80 ± 29.66 F cm-1 V-1 s-1), fast response time (~40.57 μs) and excellent switching cyclical stability. Next, the integration of sodium (Na+) and potassium (K+) ion-selective membranes with the OECTs is demonstrated, enabling selective ions detection in the physiological range. In addition, flexible OECTs are designed for electrophysiological (ECG) signals acquisition. These OECTs have shown robust performance against physical deformation and successfully recorded high quality ECG signals. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version W.L.L. would like to acknowledge funding support from Ministry of Education (MOE) under AcRF Tier 2 Grant (MOE2019-T2-2-106) and National Robotics Programme (W1925d0106). We would like to acknowledge the Facility for Analysis, Characterization, Testing and Simulation (FACTS) and the School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, for use of their GIWAXS, XPS and AFM facilities.

Although activated carbon is generally hydrophobic, water can adsorb on its surface due to the presence of functional groups. During the initial interactions between functional groups and water molecules, atoms of the functional groups rotate around the sigma bonds to maximise the electrostatic interactions. This physical process was simulated within the framework of kinetic Monte Carlo (kMC). We extended kMC to account for the rotation of the atoms of functional groups around the sigma bonds by entropic sampling of the orientation space, and tested the modified kMC scheme for adsorption of water on graphite functionalised with either hydroxyl groups or carboxyl groups. Results show that the amount adsorbed is greater when the rotation of atoms around the sigma bonds is allowed. The interspacing of functional groups also affects the adsorbed density. It was found that the optimum distances between hydroxyl groups and carboxyl groups to initiate water cluster are 0.4 and 0.7 nm, respectively, because of the synergistic effect of electrostatic interactions between water molecule and adjacent functional groups. This effect is reduced when the spatial distance is either decreased (because of the increasing importance of the repulsion) or increased (because of the loss of the synergetic effect). Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) This study was supported by A*STAR (Singapore) Advanced Manufacturing and Engineering (AME) under its Pharma Innovation Programme Singapore (PIPS) [A20B3a0070]; A*STAR (Singapore) Advanced Manufacturing and Engineering (AME) under its Individual Research Grant (IRG) program [A2083c0049]; the Singapore Ministry of Education Academic Research Tier 1 [grant numbers 2019-T1-002-065; RG100/19] and the Singapore Ministry of Education Academic Research Tier 2 [grant number MOE-MOET2EP10120-0001].

The wind field over an urban lake may exhibit considerable variability resulting from wind-shielding effects from surrounding structures. Field measurements at an urban reservoir in Singapore were augmented by computational fluid dynamics (CFD) model results to develop a wind model over the reservoir surface via a data assimilation approach. The field measurements identified, depending on structure alignment with the prevailing wind direction, wind shielding that impacted wind direction and velocity over the reservoir surface. The wind model integrated the temporal response of the measurements and spatial distribution produced by the CFD modeling. The wind model was used to predict the spatiotemporal pattern of the wind field over the reservoir surface for a full year. The modeling results showed good agreement with measured wind data at three measurement locations on the reservoir surface. The wind model has been incorporated with a hydrodynamics and water quality model to provide the spatiotemporal wind forcing over the reservoir surface. National Research Foundation (NRF) Public Utilities Board (PUB) Published version This work is supported by the Singapore National Research Foundation, under its Environment and Water Technologies Strategic Research Programme and administered by the Environment and Water Industry Programme Office, and PUB, Singapore’s National Water Agency, under project 1002-IRIS-09.

Osmotically assisted reverse osmosis (OARO) has shown great potential for low-cost and energy-efficient brine management. However, its performance can be significantly limited by membrane fouling. Here, we performed for the first time a comprehensive study on OARO membrane fouling, explored the associated fouling mechanisms, and evaluated fouling reversibility via simple physical cleaning strategies. First, internal membrane fouling at the draw (permeate) side was shown to be insignificant. Flux behavior in short-term operation was correlated to both the evolution of fouling and the change of internal concentration polarization. In long-term operation, membrane fouling constrained the OARO water flux to a singular, common upper limit, in terms of limiting flux, which was demonstrated to be independent of operating pressures and membrane properties. Generally, once the limiting flux was exceeded, the OARO process performance could not be improved by higher-pressure operation or by utilizing more permeable and selective membranes. Instead, different cyclic cleaning strategies were shown to be more promising alternatives for improving performance. While both surface flushing and osmotic backwashing (OB) were found to be highly effective when using pure water, a full flux recovery could not be achieved when a nonpure solution was used during OB due to severe internal clogging during OB. All in all, the presented findings provided significant implications for OARO operation and fouling control. Nanyang Technological University This research was supported by the Start-up Grant (SUG #002195-00001) for Q.S. from Nanyang Technological University. Furthermore, C.D. Peters and N.P. Hankins are grateful to the University of Bahrain (in the Kingdom of Bahrain) for granting a full scholarship to C.D. Peters.

To exploit the benefits of membrane-based separation for the pharmaceutical and chemical industries, the understanding of membrane fouling in organic solvents is crucial. Specifically for the separation of biocatalysts in the manufacture of pharmaceuticals, this study investigated membrane fouling by bovine serum albumin (BSA) in 10% v/v isopropanol (IPA), 10% v/v dimethyl sulfoxide (DMSO), 30% v/v IPA, and 30% v/v DMSO, benchmarked against that in water. The presence of either IPA or DMSO worsened fouling, with the latter comparatively worse. To understand the fouling mechanisms, Field Emission Scanning Electron Microscopy (FESEM) images were taken to assess external fouling, Evapoporometry (EP) was used to measure the pore-size distributions of the fouled membranes to examine internal fouling, a fouling model was applied to extract the fouling parameters, and the interfacial interaction energies were derived. Results indicate that the worst fouling in 30% v/v DMSO was due to both significant external fouling and internal fouling, whereas the second-worst fouling by 30% v/v IPA was caused predominantly by internal fouling. The magnitudes of the total DLVO- and XDLVO-based interaction energies were found to be poorly related to the relative flux declines. This study provides valuable insights into membrane fouling in different solvent environments. Agency for Science, Technology and Research (A*STAR) Economic Development Board (EDB) Ministry of Education (MOE) We acknowledge funding from the Singapore GSK (GlaxoSmithKline) – EDB (Economic Development Board, Singapore) Trust Fund, A*STAR (Singapore) Advanced Manufacturing and Engineering (AME) under its Pharma Innovation Programme Singapore (PIPS) program (A20B3a0070) and A*STAR (Singapore) Advanced Manufacturing and Engineering (AME) under its Individual Research Grant (IRG) program (A2083c0049), the Singapore Ministry of Education Academic Research Fund Tier 1 Grant (2019-T1-002-065; RG100/19) and the Singapore Ministry of Education Academic Research Fund Tier 2 Grant (MOEMOET2EP10120-0001).

In recent years, brine management in seawater reverse osmosis (SWRO) desalination has been more emphasized to reduce environmental hazards and recover valuable resources. However, current brine treatment methods are often hindered by the high brine concentration and energy consumption. To mitigate these challenges, this work applies a diafiltration-nanofiltration-reverse osmosis (DiaNF-RO) process, which aims to achieve divalent-monovalent ion separation in the pre-treatment step prior to RO. The diafiltration process is to enhance the separation performance of NF stage, while the RO stage is to produce the desalinated water and the diluent required by the diafiltration process. This study would justify the benefits of pre-treatment method (i.e., DiaNF-RO) over post-treatment method (i.e., RO-DiaNF), Fig. 1, in brine management by comparing the processes in 3 aspects (i.e., performance, operation, economic) via practical simulations, including pressure drop within module and concentration polarization (CP) effect, at the same number of stages and system water recovery, under similar input conditions such as NF/RO pressures and NF recovery rates. As shown in Table 1, compared to RO-DiaNF, the DiaNF-RO has better Mg-Na ion separation factor (SF) in both NF and RO brines; higher Na dilution in NF brine; lower RO area requirement; larger potential to operate at higher pressure and recovery due to lower osmotic pressure difference at membrane stages; less total operating cost especially with more stages due to more RO area saving. Overall, the pre-treatment DiaNF-RO achieves better results in performance, operation, and economic than the conventional post-treatment RO-DiaNF. National Research Foundation (NRF) Public Utilities Board (PUB) This research is supported by the National Research Foundation, Singapore, and PUB, Singapore’s National Water Agency under its RIE2025 Urban Solutions and Sustainability (USS) (Water) Centre of Excellence (CoE) Programme which provides funding to the Nanyang Environment & Water Research Institute (NEWRI) of the Nanyang Technological University, Singapore (NTU).

Conventional organic solvent recovery is energy intensive and challenged by large footprint and complex operation and maintenance. To enable a more circular and sustainable pharmaceutical production, we amalgamate adsorption and membrane processes to address current Achilles heels in organic solvent recovery. In this work, we have successfully designed a polyacrylonitrile (PAN) electrospun membrane as scaffold to incorporate nanomaterial adsorbents in a layer-by-layer hierarchical structure. The porous nanofibrous morphology and layer-by-layer design, which deconstructs the adsorbent layers, help reduce the transport resistance of the isopropyl alcohol (IPA), leading to higher processing capacity at lower applied pressure, while maintaining the removal rates. To bring about versatility for different contaminants, we incorporated two different nanomaterials, namely positively charged metal-organic frameworks (MOFs), particularly MIL-101(Cr), and negatively charged functionalized multi-walled carbon nanotubes (MWCNTs) as powdered adsorbents, for the extraction of anionic and cationic dyes, respectively. Our results show that the MOF-based membrane scaffold can achieve 99% and 95% rose Bengal and methyl orange removal rates in IPA, respectively, while operating at a low operating pressure of 0.04 bar and delivering a processing capacity of 60 L m−2 h−1 of IPA, with good regeneration and recyclability of up to three cycles of removal process. On the other hand, the MWCNT-based membrane scaffold displays up to 90% methylene blue dye in IPA at 0.07 bar pressure and delivering a 40 L m−2 h−1 of IPA processing capacity in a single-cycle removal process. The promising recovery performance and facile tailoring of adsorbents to target contaminants of different charges render our adsorptive membrane scaffold process less energy intensive and highly versatile to meet various needs for solvent recovery in the pharmaceutical industry. National Research Foundation (NRF) Public Utilities Board (PUB) Submitted/Accepted version This research is supported by the National Research Foundation, Singapore, and implemented by the Public Utilities Board (PUB), Singapore’s National Water Agency, under its Competitive Funding for Water Research Funding Initiative (Grant Award CWR-2101-0010).

Liquid crystal monomers (LCMs) are a large family of artificial ingredients that have been widely used in global liquid crystal display (LCD) industries. As a major constituent in LCDs as well as the end products of e-waste dismantling, LCMs are of growing research interest with regard to their environmental occurrences and biochemical consequences. Many studies have analyzed LCMs in multiple environmental matrices, yet limited research has investigated the toxic effects upon exposure to them. In this study, we combined in silico simulation and in vitro assay validation along with omics integration analysis to achieve a comprehensive toxicity elucidation as well as a systematic mechanism interpretation of LCMs for the first time. Briefly, the high-throughput virtual screen and reporter gene assay revealed that peroxisome proliferator-activated receptor gamma (PPARγ) was significantly antagonized by certain LCMs. Besides, LCMs induced global metabolome and transcriptome dysregulation in HK2 cells. Notably, fatty acid β-oxidation was conspicuously dysregulated, which might be mediated through multiple pathways (IL-17, TNF, and NF-kB), whereas the activation of AMPK and ligand-dependent PPARγ antagonism may play particularly important parts. This study illustrated LCMs as a potential PPARγ antagonist and explored their toxicological mode of action on the trans-omics level, which provided an insightful overview in future chemical risk assessment. Ministry of Education (MOE) This work is supported by the Singapore Ministry of Education Academic Research Fund Tier 1 (04MNP000567C120), MOE-T2EP30220-0008, MOE-MOET32020-0004, a Startup Grant of Fudan University (JIH 1829010Y), and the National Natural Science Foundation of China (21976088).

In our previous study, quorum quenching (QQ) bacteria can effectively enhance methane production in an anaerobic membrane bioreactor (AnMBR) while mitigating membrane biofouling. However, the mechanism of such enhancement is unclear. In this study, we analyzed the potential effects from separated hydrolysis, acidogenesis, acetogenesis and methanogenesis steps. The cumulative methane production improved by 26.13%, 22.54%, 48.70% and 44.93% at QQ bacteria dosage of 0.5, 1, 5 and 10 mg strain/g beads, respectively. It was found that the presence of QQ bacteria enhanced acidogenesis step resulting in higher volatile fatty acids (VFA) production, while it had no obvious influence on hydrolysis, acetogenesis and methanogenesis steps. The substrate (glucose) conversion efficiency in acidogenesis step was also accelerated (1.45 folds vs control within first eight hours). The abundance of hydrolytic fermentation gram-positive bacteria and several acidogenic bacteria, such as Hungateiclostridiaceae, was promoted in QQ amended culture, which enhanced VFA production and accumulation. Although the abundance of acetoclastic methanogen Methanosaeta reduced by 54.2% on the 1st day of QQ beads addition, the overall performance of methane production was not affected. This study revealed that QQ had a greater impact on the acidogenesis step in the anaerobic digestion process, though the microbial community in acetogenesis and methanogenesis steps was altered. This work can provide a theoretical basis for using QQ technology to slow down the rate of membrane biofouling in anaerobic membrane bioreactors while increasing methane production and maximizing economic benefits. Nanyang Technological University The authors acknowledge the financial support of Advanced Environmental Biotechnology centre, Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, Singapore.

Boron-doped diamond and titanium suboxides have been proposed as electrode materials for use as anodes in future electrochemical devices, most likely in remote locations for potable water purification, or for specialized disinfection applications in decentralized systems. A comparison is made between electrochemical purification strategies that do not require added chemicals and systems that do, with emphasis given toward Magnéli electrode-based electrochemical disinfection and iodine-based electrochemical disinfection systems. Both systems with and without added chemicals come with advantages and disadvantages. The outlook of these emerging processes concludes this review.

Designing robust electrocatalysts for water-splitting is essential for sustainable hydrogen generation, yet difficult to accomplish. In this study, a fast and facile two-step technique to synthesize Ru/RuO2 aerogels for catalyzing overall water-splitting under alkaline conditions is reported. Benefiting from the synergistic combination of high porosity, heterointerface, and tensile strain effects, the Ru/RuO2 aerogel exhibits low overpotential for oxygen evolution reaction (189 mV) and hydrogen evolution reaction (34 mV) at 10 mA cm-2 , surpassing RuO2 (338 mV) and Pt/C (53 mV), respectively. Notably, when the Ru/RuO2 aerogels are applied at the anode and cathode, the resultant water-splitting cell reflected a low potential of 1.47 V at 10 mA cm-2 , exceeding the commercial Pt/C||RuO2 standard (1.63 V). X-ray adsorption spectroscopy and theoretical studies demonstrate that the heterointerface of Ru/RuO2 optimizes charge redistribution, which reduces the energy barriers for hydrogen and oxygen intermediates, thereby enhancing oxygen and hydrogen evolution reaction kinetics. Ministry of Education (MOE) This work was funded by the AcRF Tier 1 (grant RG105/19) provided by the Ministry of Education in Singapore.

Water quality monitoring plays an essential role in water resource management and water governance. At present, the monitoring is commonly conducted via in-situ sampling and/or by setting up gauging stations, which can be labour intensive and costly. Recently, the possibility of monitoring water quality through remote sensing with Unmanned Aerial Vehicles (UAVs) and hyperspectral sensors has shown great promise, with the key advantages of larger spatial coverage and possibly higher accuracy enabled by higher spectral resolution and more extensive data. Correspondingly, more advanced methods need to be established for hyperspectral analysis for water quality determination to capitalize on this wealth of information. In this study, a new method called Hierarchical Bayesian Model Aggregation for Optimal Multiple Band Ratio Analysis (HBMA-OMBRA) has been developed as a proof-of-concept for estimating Total Suspended Solids (TSS) concentrations from the hyperspectral data. The method leverages on the Bayesian ensembling of competing models because there is not a single best working model for all situations. It also encompasses a new approach called Ensemble Band Ratio Selection (ENBRAS) for the identification of best candidate band ratios (BBRs) via a set of ensembling and “bagging” procedures, followed by a modified Batchelor Wilkin's algorithm to cluster the candidate band ratios. A laboratory investigation was conducted in the present study to measure the hyperspectral reflectance in different experiments under various environmental conditions to verify the robustness of HBMA-OMBRA. From the experimental results, six distinct clusters of candidate BBRs were identified using ENBRAS. In particular, two clusters in the red, green, and near infrared spectrum showed the largest contribution. The significance of multi-clusters provides an explanation for previously contrasting results reported in the literature and some evidence for reconciling these findings. Public Utilities Board (PUB) Submitted/Accepted version We would like to thank Public Utilities of Singapore (PUB) – Singapore’s National Water Agency, for granting the scholarship and providing support to the first author.

A variety of sludge-based waste materials with distinctive physical and chemical characteristics are co-treated with municipal solid waste (MSW) in a demonstration-scale high-temperature slagging gasifier. The waste materials tested include dewatered sewage sludge (originated from industrial and municipal wastewater treatment processes, respectively), dried sewage sludge, sludge incineration ashes, and waterworks sludge (originated from freshwater treatment process). Up to 49.5% by mass of dried sewage sludge is successfully co-gasified with MSW and up to 89.5% of the solid residues from the gasification process is recovered as reusable slag and recyclable metals. Despite feeding of various waste mixtures, stable operation of the slagging gasifier is achieved with the proper control of the temperature profiles inside the gasifier, the melting of inorganic residues, smooth discharge of the molten slag, and effective flue gas emissions control. Various types of waste-derived slag are characterized to evaluate their potentials to be applied as sustainable construction materials. Toxicity characteristic leaching procedure (TCLP) and compliance batch leaching test results indicate that the sludge-derived slag is environmentally safe with very low pollution potential. In addition, life cycle assessment (LCA) is performed to comprehensively evaluate the treatment of sludge-based waste materials via slagging co-gasification technology. These findings reveal the promising potentials of converting sludge to slag through the high temperature slagging gasification process based on both engineering and environmental aspects, as well as the possible areas for further advancement in the future. National Research Foundation (NRF) Public Utilities Board (PUB) Submitted/Accepted version The authors would like to acknowledge the Public Utilities Board (PUB) of Singapore for the financial support to the project, and National Research Foundation (NRF) of Singapore, National Environmental Agency (NEA) and Economic Development Board (EDB) of Singapore for supporting the construction and operation of Waste-to-Energy Research Facility. Additionally, this research is supported by the National Research Foundation, Singapore, and PUB, Singapore’s National Water Agency under its RIE2025 Urban Solutions and Sustainability (USS) (Water) Centre of Excellence (CoE) Programme which provides funding to the Nanyang Environment & Water Research Institute (NEWRI) of the Nanyang Technological University, Singapore (NTU).

The co-location of offshore wind and floating solar farms is an attractive hybrid option that optimizes the areal power density for the renewable power production. However, an important consideration remains whether the strong waves expected in the high-wind environment would cause large displacement of the floating solar panels and therefore significantly affect the solar power output. The present study addresses this research question by simulating the power output of a floating solar array under various high wind and wave conditions at three offshore locations, considering the effects of temperature, humidity, wind speed and wave characteristics on the system electrical behavior. The wave-platform interaction is solved with fully developed sea states to predict the fluctuating tilt angles of the solar panels. Subsequently, the total solar power output is obtained considering the solar irradiation and the estimated operating temperature. The results show that the relative changes are small in all cases, implying that the solar power output would remain stable even under high wind and wave conditions. The optimal tilt angle of the floating PV panels is also examined for the three offshore locations. The study validates the feasibility of hybrid offshore wind-solar farms, provided that structural safety has been properly considered. Submitted/Accepted version

In this work, a positively charged hollow fiber nanofiltration (NF) membrane based on twice interfacial polymerization (IP) reactions was developed for water soften and heavy metal ions removal. The first IP reaction was conducted on the polyethersulfone (PES) hollow fiber substrate using a mixture of branched polyethyleneimine (PEI) and piperazine (PIP) as the aqueous phase monomers in the aqueous phase reacting with trimesoyl chloride (TMC) in the cyclohexane solution. Then, a secondary IP reaction was performed between tris(2-aminoethyl) amine (TAEA) solution and the residual acyl chloride groups on the membrane to increase the positive charge density on the membrane surface. Consequently, a NF membrane with intensified positive surface charge density was successfully fabricated. The optimized membranes achieved a high rejection of MgCl2 of 97.6% while maintaining a pure water permeability (PWP) of 16.0 L m−2 h−1 bar−1. Meanwhile, the membranes exhibit high rejection values of 99.8% to Cu2+ and 99.7% to Zn2+, respectively. In conclusion, this work provides a facile way to prepare a positively charged membrane for efficient water softening and metal ions removal. Submitted/Accepted version

Utilization of renewable raw materials as feedstock defossilizes industrial manufacturing while subsequent carbon capture reduces carbon footprint. We applied this concept to design a new pyrolysis-based process for synthesis of biogenic multi-walled carbon nanotubes (MWCNTs) and H2 from biomass. It was demonstrated that the conversion of hydrocarbon compounds in pyrolysis gas into MWCNTs and H2 is detrimentally influenced by accompanied CO2 released from biomass decomposition. Capturing CO2 with a calcium sorbent upgraded the pyrolysis gas into a suitable gaseous precursor for downstream production of MWCNTs and H2 -rich gas. Furthermore, the results suggest that CO2 capture with the sorbent has a potential to outperform a liquid alkaline scrubber owing to avoided liquid organic waste generation, sorbent regenerability and higher H2 recovery from biomass pyrolysis gas. National Research Foundation (NRF) Public Utilities Board (PUB) Submitted/Accepted version This research/projectis supported by the National Research Foundation, Singapore, and PUB, Singapore’s National Water Agency under its RIE2025 Urban Solutions and Sustainability (USS) (Water) Centre of Excellence (CoE) Programme, awarded to Nanyang Environment & Water Research Institute (NEWRI), Nanyang Technological University, Singapore (NTU).

Compressibility is one of the important engineering properties of municipal solid waste (MSW) affecting the stability and functionality of a landfill. Although the correlations between MSW properties and compression parameters have been established, they either have low accuracy and small datasets or are only limited to a few specific landfills in a region. In this study, a new method using the initial global void ratio (e0*) of MSW to estimate the compression indices is developed based on a comprehensive MSW dataset. The dataset consists of 124 sets (91 laboratory and 33 field) of MSW compression results obtained from 44 studies in 13 countries with different income levels and climate conditions. We categorized MSW as a ternary mixture with biodegradable (B), reinforcing (R), and inert (I) fractions, and suggested average specific gravity values (Gs,B = 1.20, Gs,R = 1.07, and Gs,I = 2.64), respectively. The e0* values were calculated using the initial dry unit weight (γd,0) and ternary composition of MSW. The correlations between the e0* and the immediate compression index, secondary compression index induced by mechanical creep, and secondary compression index induced by bio-compression of MSW were evidently established. The results are applicable to the MSW with B = 0-79.2 %, R = 0-54.0 %, I = 2.8-100.0 %, and γd,0 = 2.0-14.2 kN/m3. A simple flowchart was established to estimate the compression indices and strains of MSW disposed on in landfills and dumpsites in countries with different income levels.

The soil–water characteristic curve (SWCC) is one of the most crucial and fundamental soil properties in unsaturated soil mechanics. Many theories and equations have been developed to describe and best fit SWCC with unimodal or bimodal characteristics. In this study, a general best-fitting equation for SWCC with multimodal characteristics (bimodal and trimodal SWCC) is proposed. The parameters in the proposed equation are closely related to the properties of soil and variables in the SWCC. To evaluate the performance of the proposed equation in best-fitting multimodal SWCC that has more than two modalities, a trimodal SWCC soil mixture that consists of sand, kaolin and activated carbon has been prepared and tested in the laboratory in this study. The proposed equation has been evaluated with data from published literature and the newly developed soil mixture of trimodal SWCC. The proposed equation has shown high accuracy for best-fitting bimodal SWCC and trimodal SWCC. Nanyang Technological University Submitted/Accepted version This study was supported by a research scholarship from the Nanyang Environment & Water Research Institute (NEWRI) and Nanyang Technological University, Singapore.

Waste-to-Energy (WtE) through municipal solid waste (MSW) incineration is a key waste management strategy to reduce the mass and volume of landfilled wastes, especially for land-constrained areas such as urban centres. However, this process releases large amounts of CO2 into the atmosphere and the ash that remains after burning, which contains a variety of metals and minerals, is often sent to the landfill after some metal recovery. In this study, the CaO containing ash is used to derive sorbents for the calcium looping (CaL) process for post-combustion CO2 capture and storage (CCS), and a techno-economic assessment was performed to preliminarily probe the feasibility of retrofitting a CaL plant using ash-derived sorbents to capture CO2 from a 200MWth WtE plant, as a possible means to decarbonise WtE plants. The analysis was performed through process modelling of the CaL plant using 4 different supplementary fuels in the calciner, namely, biomass charcoal (BC), solid recovered fuel (SRF), coal, and natural gas (NG). At the base purge ratio of 5%, all the cases show increases in the levelised cost of electricity (LCOE) over the base WtE, ranging from 184 (NG) to 246 (BC) USD/MWhe. The sale of additional electricity generated from the heat recovery steam cycle could slightly mitigates the capital intensiveness of the process, resulting in a levelised cost of carbon abatement (LCCA) range of USD 89 (SRF) to 184 (coal)/tCO2, which is competitive with other bioenergy with CO2 capture and storage (BECCS) technologies. The biogenic fuels also result in lower specific primary energy consumption per CO2 avoided (SPECCA) of 5.6 (BC) and 6.8 (SRF) MJLHV/tCO2, which are comparable to values from other CCS technologies and CaL implementation studies. Sensitivity analysis of 14 economic and process parameters reveals that further improvements can be achieved through optimisation of the energy intensive sub-processes, such as cryogenic air separation and CO2 compression and purification. Tighter solid heat integration (SHI) concepts were also modelled and are shown to effectively reduce fuel and O2 requirements by up to 22.2%, thereby lowering annualised costs by up to 11.9%. In addition, this paper highlights the importance of regulatory support through favourable policies such as higher carbon pricing and CO2 credit trading to push the development and adoption of negative emission technologies to meet global decarbonisation targets. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Public Utilities Board (PUB) Submitted/Accepted version The research team is thankful to the financial support by Singapore Energy Centre (SgEC-Core2019-34) and Agency for Science, Technology and Research (A*STAR) of Singapore under its Low Carbon Energy Research Funding Initiative (LCER-FI, project number: U2102d2007). This research/project is supported by the National Research Foundation, Singapore, and PUB, Singapore’s National Water Agency under its RIE2025 Urban Solutions and Sustainability (USS) (Water) Centre of Excellence (CoE) Programme, awarded to Nanyang Environment & Water Research Institute (NEWRI), Nanyang Technological University, Singapore (NTU).

Polymer foam that provides good support with high energy return (low energy loss) is desirable for sport footwear to improve running performance. Ethylene-vinyl acetate copolymer (EVA) foam is commonly used in the midsole of running shoes. However, EVA foam exhibits low mechanical properties. Conventional mineral fillers are usually employed to improve EVA's mechanical performance, but the energy return is sacrificed. Here, we produced nanocomposite foams from EVA and multi-walled carbon nanotubes (CNT) using a chemical foaming process. Two kinds of CNT derived from the upcycling of commodity plastics were prepared through a catalytic chemical vapor deposition process and used as reinforcing and nucleating agents. Our results show that EVA foam incorporated with oxygenated CNT (O-CNT) demonstrated a more pronounced improvement of physical, mechanical, and dynamic impact response properties than acid-purified CNT (A-CNT). When CNT with weight percentage as low as 0.5 wt% was added to the nanocomposites, the physical properties, abrasion resistance, compressive strength, dynamic stiffness, and rebound performance of the EVA foams were improved significantly. Unlike the conventional EVA formulation filled with talc mineral fillers, the incorporation of CNT does not compromise the energy return of the EVA foam. From the long-cycle dynamic fatigue test, the CNT/EVA foam displays greater properties retention as compared to the talc/EVA foam. This work demonstrates a good balanced of mechanical-energy return properties of EVA nanocomposite foam with very low CNT content, which presents promising opportunities for lightweight-high rebound midsoles for running shoes. Published version

Recent advances in nanotechnology have brought great opportunities to the developing next-generation nanofiltration membranes for addressing the concern of global water scarcity and energy crisis. Carbon dots have been deemed as a promising nanomaterial for enhancing the nanofiltration performance of polymeric membranes. Herein, carbon dots with cationic amine groups (PEI-CDs) and those with anionic sulfonate groups (PS-CDs) are incorporated into the polyamide selective layer of thin-film nanocomposite (TFN) membranes to create charged nanovoids (free volume) between the carbon dots and the surrounding polyamide network for high-efficiency nanofiltration. The positively charged amine group-based and negatively charged sulfonate group-based nanovoids in the resultant TFN-PEI-CDs and TFN-PS-CDs membranes, respectively, provide alternative pathways for efficient water permeation while effectively rejecting divalent ions via the Donnan and dielectric exclusion effects, thereby overcoming the recurring trade-off between permeability and selectivity encountered by dense polymeric membranes. In particular, the creation of negatively charged nanovoids enables the TFN-PS-CDs membrane to achieve one of the best performances among the recently reported nanofiltration membranes, by showing a nearly tripled pure water permeability of 30.9 L m−2 h−1 bar−1 as well as a higher Na2SO4 rejection rate of 99.4% than the membrane with a pristine polyamide selective layer. Moreover, the TFN membranes demonstrate greater resistance to foulants with charges of the same sign as the nanovoids. This work provides insights into the design of nanovoids with desired properties in other polymeric membranes for high-efficiency filtration processes. Nanyang Technological University The authors acknowledge the financial support from the Nanyang Environment and Water Research Institute (Core Funding), Nanyang Technological University, Singapore.

Many antibiotics are ineffective in killing Gram-negative bacteria due to the permeability barrier of the outer-membrane LPS. Infections caused by multi-drug-resistant Gram-negative pathogens require new antibiotics, which are often difficult to develop. Antibiotic potentiators disrupt outer-membrane LPS and can assist the entry of large-scaffold antibiotics to the bacterial targets. In this work, we designed a backbone-cyclized ultra-short, six-amino-acid-long (WKRKRY) peptide, termed cWY6 from LPS binding motif of β-boomerang bactericidal peptides. The cWY6 peptide does not exhibit any antimicrobial activity; however, it is able to permeabilize the LPS outer membrane. Our results demonstrate the antibiotic potentiator activity in the designed cWY6 peptide for several conventional antibiotics (vancomycin, rifampicin, erythromycin, novobiocin and azithromycin). Remarkably, the short cWY6 peptide exhibits wound-healing activity in in vitro assays. NMR, computational docking and biophysical studies describe the atomic-resolution structure of the peptide in complex with LPS and mode of action in disrupting the outer membrane. The dual activities of cWY6 peptide hold high promise for further translation to therapeutics. Published version S.B. acknowledges funding support from Singapore-MIT Alliance for Research and Technology (SMART) ING-000834 BIO IGN, Singapore.

Soil-water characteristic curve (SWCC) correlates the water content of a soil to its soil suction, which is a very important property of unsaturated soils. Osmotic tensiometers (OTs) have shown their capability in high soil suction measurement. This study tried to use OT combined with a pressure plate and WP4C dewpoint potentiometer to determine the SWCC of a residual soil. Three OTs with different measuring ranges (900 kPa, 1200 kPa, 2300 kPa) were prepared for soil suction measurement. The temperature effect on the pressure variations of OTs was illustrated based on Flory-Huggins polymer theories and an appropriate calibration equation was proposed to eliminate the temperature effect on the accuracy of soil suction measurement using OT. The OT showed a fast response in soil suction measurement and the equilibrium can be established in 10–15 min during SWCC measurement. Comparison of the SWCC data obtained from the pressure plate, OT, and WP4C dewpoint potentiometer proves that the OT had good performance in the determination of SWCC, especially for the transition zone (i.e., 10–1500 kPa suction range), by providing more data points to define the SWCC in a shorter period. The results show that the usage of OT will shorten the time required for the determination of SWCC and could be considered as a new and reliable technique in SWCC measurement. Submitted/Accepted version

A multiphase CFD-DEM model was built to simulate the waste-to-energy gasifying and direct melting furnace in a pilot demonstration facility. The characterizations of feedstocks, waste pyrolysis kinetics, and charcoal combustion kinetics were first obtained in the laboratory and used as model inputs. The density and heat capacity of waste and charcoal particles were then modelled dynamically under different status, composition, and temperature. A simplified ash melting model was developed to track the final fate of waste particles. The simulation results were in good agreement with the site observations in both temperature and slag/fly-ash generations, verifying the CFD-DEM model settings and gas-particle dynamics. More importantly, the 3-D simulations quantified and visualized the individual functioning zones in the direct-melting gasifier as well as the dynamic changes throughout the whole lifetime of waste particles, which is otherwise technically unachievable for direct plant observations. Hence, the study demonstrates that the established CFD-DEM model together with the developed simulation procedures can be used as a tool for the optimisation of operating conditions and scaled-up design for future prototype waste-to-energy gasifying and direct melting furnace. National Research Foundation (NRF) Public Utilities Board (PUB) This research is supported by the National Research Foundation, Singapore, and PUB, Singapore’s National Water Agency under its RIE2025 Urban Solutions and Sustainability (USS) (Water) Centre of Excellence (CoE) Programme which provides funding to the Nanyang Environment & Water Research Institute (NEWRI) of the Nanyang Technological University, Singapore (NTU).

Volatile organic compounds (VOCs) can lead to environmental pollution and threaten human health due to their toxic and carcinogenic nature. The emission of VOCs increases dramatically with the accelerated industrialization and economic growth. Adsorption is identified as one of the most promising recovery technologies owing to its cost-effectiveness, flexible operation, and low energy consumption. In particular, adsorption-based technologies have a high potential to recycle both adsorbents and adsorbates, typically to capture valuable aromatic VOCs from industrial exhaust. Porous materials such as carbon-based materials, zeolite-based materials, and organic polymers and their composites have been extensively developed for VOCs adsorption focusing in adsorption capacity, hydrophobic property, thermal stability and regenerability. Among them, porous carbons as VOCs adsorbents have attracted increasingly attention, because they can be regulated by tuning the pore structure for VOCs accessibility during the adsorption process. Moreover, porous carbons can adsorb target VOCs by controlling the pore structure and surface functional groups. Significantly, the pore size distribution of porous carbons mostly controls the VOCs sorption process. Micropores provide the main adsorption sites, while mesopores enhance the diffusion of VOCs. In this review, the adsorption mechanism of VOCs onto porous carbons was generally concluded. Porous carbons can be designed as a specific structure for adsorption of aromatic VOCs by controlling the pore structure, hydrophobic sites, π-electronic structure, and surface functional groups. Since there are limited review literatures on porous carbons derived from renewable resources for VOCs adsorption, this paper will provide an overview on the synthesis of porous carbons from biomass and other organic wastes for VOCs adsorption or integrated oxidation processes (e.g., photocatalysis, non-thermal plasma catalysis, chemical catalysis) under ambient conditions with the objective of guiding future works on the VOCs abatement technologies towards a sustainable direction. This work is supported by the National Natural Science Foundation of China (Grant 21607079) and “333 talent” project of Jiangsu Province.

The in situ and laboratory MSW biodegradation is a long-term process, thus the assessment of its performance can be arduous. A sand-salt mixture is often used to replace an MSW specimen for simplification or approximation, with dissolution representing biodegradation. However, the effectiveness of this approximation still needs to be confirmed, and the effects of the initial properties and test conditions such as unstable fraction, size ratio, initial compaction, and vertical stress on the accuracy of this approximation are unknown. In this study, supplementary dissolution tests of sand-salt mixtures are first conducted to construct a dataset for sand-salt mixtures and MSW specimens. Then, the settlement, one of the most important characteristics in practice, is chosen to be the indicator to compare the suitability of this approximation based on test groups with different unstable fractions, while the effects of other initial properties and conditions are also investigated. Overall, the effectiveness of the approximation largely depends on the biodegradable fraction and salt fraction, while other properties only pose limited effects. Nanyang Technological University Submitted/Accepted version The authors would like to acknowledge Nanyang Technological University (NTU, Singapore) and Interdisciplinary Graduate Programme (IGP) for the financial support and scholarships of this research.

Ca/Fe-rich antibiotic fermentation residues (AFRs), a type of hazardous waste, can be regarded as recyclable biomass and metal resources. However, concurrent detoxification and reutilization of biomass and metals resources from AFRs have never been reported before. In this study, Ca/Fe-rich vancomycin fermentation residues were pyrolyzed into biochar to adsorb phosphate for the first time. The residual vancomycin and antibiotic resistance genes were completely decomposed during pyrolysis. The resultant Ca/Fe-rich biochar exhibited excellent performance at adsorbing phosphate without further modifications. The process had rapid kinetics and a maximum adsorption capacity of 102 mg P/g. Ca and Fe were the active sites, whereas different mechanisms were observed under acidic and alkaline conditions. Surprisingly, HCO3- enhanced phosphate adsorption with an increase of adsorption capacity from 43.9 to 71.0 mg/g when HCO3- concentration increased from 1 to 10 mM. Furthermore, actual wastewater could be effectively treated by the biochar. The phosphate-rich spent biochar significantly promoted seed germination (germination rate: 96.7 % vs. 80.0 % in control group, p < 0.01) and seedling growth (shoot length was increased by 57.9 %, p < 0.01) due to the slow release of bioavailable phosphate, and thus could be potentially used as a phosphorous fertilizer. Consequently, the hazardous waste was turned into phosphorous fertilizer, with the additional benefits of detoxifying AFRs, reutilizing biomass and metal resources from AFRs, controlling phosphate pollution, and recovering phosphate from wastewater. The work was supported by the Fuzhou Institute of Oceanography (Grant No. 2021F10).

Sanitary landfills and uncontrolled dumpsites are plastic wastes (PWs) reservoirs containing ∼60% of all the plastics ever made, amounting to 5,000 × 106 tons as of 2017. The distribution, long-term behavior, and release of macro- and microplastics (MPs) from disposal sites are critical to global plastics pollution, but are poorly understood and lack systematic assessments. We review comprehensively the available knowledge in the three aspects herein. The spatial and temporal distribution of PW in 616 municipal solid waste (MSW) samples retrieved from 275 disposal sites in 56 countries are summarized. The weight percentages of PW (%PW) generally decrease with increasing year of disposal and disposal depth. Other influential factors are disposal duration and country income level. The %PW values in different disposal sites show high regionality and spatial variability and heterogeneity. Disposal sites mostly have harsh temperature and stress, reactive liquids, and microbial activities, which are conducive to long-term processes of PW and MPs. The major processes are chemical degradation, dissolution, leaching and adsorption, biological degradation, mechanical wearing, pneumatic and hydrological transport and deposition, and conglomeration. PW leaves disposal sites via recycling, scavenging, mining, wind and surface runoff, coastal erosion and flooding, and slope failure. The release and removal pathways of PW from disposal sites have been recognized only qualitatively. In addition, the sources, presences, and secondary generation of MPs in disposal sites have been studied occasionally, whereas the transport and fate of MPs within and from disposal sites remain largely unstudied. Economic Development Board (EDB) Nanyang Technological University The authors would like to acknowledge Nanyang Technological University (NTU, Singapore), Nanyang Environment and Water Research Institute (Singapore), and Economic Development Board (Singapore) for the financial support and scholarships of this research. Xunchang Fei thanks the supports from Debris of the Anthropocene to Resources (DotA2) Lab at NTU. Jun Ma was supported by the China Scholarship Council (Grant No. 201904910309).

Multi Jet Fusion (MJF) has gradually been utilised for the commercial fabrication of final products. In particular, the mechanical properties of MJF-printed polyamide 12 (MJF PA12) parts have been widely investigated by manipulating the process parameters such as the printing orientation and the cooling rate. In this work, the effects of build positions on the thermal history, crystallization, and mechanical properties of MJF PA12 parts were investigated. The thermal history of printed parts was obtained using the MJF Thermal Prediction Engine software developed by Hewlett-Packard HP Labs (HP Inc.). As compared to the parts printed at the boundaries, those in the centre region experienced a slower cooling rate, which was favourable for crystal growth. Both the crystallite size and crystallinity of the parts in the centre region were larger than those of the parts at the boundaries. The parts printed in the centre region had slightly higher tensile modulus and significantly smaller elongation at break and strain energy density than those printed at the boundaries. The tensile strength of the parts at different locations was comparable. This work serves as a guide to selecting the build position of MJF-printed parts to achieve desirable mechanical properties. Published version This work was supported by Industry Alignment Fund-Industry Collaboration Projects Grant: [Grant Number I1801E0028].

Non-hemolytic antimicrobial peptides (AMPs) are vital lead molecules for the designing and development of peptide-based antibiotics. Thanatin a 21-amino acid long single disulfide bonded AMP is known to be highly non-hemolytic with a limited toxicity to human cells and model animals. Thanatin demonstrates a potent antibacterial activity against multidrug-resistant Gram-negative pathogens. A single mutated variant of thanatin replaced last residue Met21 to Phe or thanatin M21F has recently been found to be more active compared to the native peptide. In order to gain mechanistic insights toward bacterial cell lysis versus non-hemolysis, here, we report atomic resolution structure and mode insertion of thanatinM21F reconstituted into zwitterionic detergent micelle by use of solution NMR spectroscopy. The 3D structure of thanatinM21F in DPC micelle is defined by an anti-parallel β-sheet between residues I9-F21 with a central cationic loop, residues N12-R14. PRE NMR studies revealed hydrophobic core residues of thanatinM21F are deeply inserted in the DPC micelle, while residues at the extended N-terminal half of the peptide are appeared to be mostly surface localized. Marked structural differences of thanatin and thanatinM21F in negatively charged LPS and DPC micelle could be correlated with non-hemolytic and antibacterial activity. Ministry of Education (MOE) This work has been supported by the Ministry of Education (MOE), Singapore.

As low as 1 ppm concentration of ammonia is sufficient to pose a threat to fish cultured in the fish farm, and therefore effective ammonia removal method is necessary to minimize the ammonia concentration. In this study, cellulose, which is one of the low-cost and highly versatile green polymers, has been modified by TEMPO-mediated oxidation and first applied for ammonia removal from water. For the TEMPO-oxidized cellulose of 0.78 mmol/g carboxylate group content, the adsorption capacity was measured to be 8.21 mg/g (empirically, 9.465 mg/g derived from Langmuir isotherm model) from water at pH around 7.0, which is comparable with the existing carbon-based sorbent for the reduction of ammonia. This also indicates close to 100% utilization of the carboxylate adsorption sites. In addition, equilibrium adsorption can be achieved within 5 min. The ammonium adsorption data fit the Langmuir model very well, indicating a monolayer chemical adsorption process. The adsorption performance of the material was minimally influenced by a pH range of 5.0-9.0 but substantially affected by the presence of competing ions. Despite a slight decrease in adsorption performance, the material can be regenerated and applied in a real water sample. Electrostatic interaction and hydrogen bonding between the introduced carboxylate groups and ammonium ions appear to be the adsorption mechanisms governing the material performance in ammonia removal. Further discussion on performance comparison, alternative modification methods, production cost, and potential usage of the postadsorption material is also included. Nanyang Technological University This work was partially supported by NTU-Harvard Joint Programme on Sustainable Nanotechnology (SusNano) (Grant 002054-00001).

The ubiquitous presence of per- and polyfluoroalkyl substances (PFAS) in various environments has led to increasing concern, and these chemicals have been confirmed as global contaminants. Following the chemical regulatory restrictions imposed, PFAS alternatives that are presumed to be less toxic have been manufactured to replace the traditional ones in the market. However, owing to the original release and alternative usage, continuous accumulation of PFAS has been reported in environmental and human samples, with uncertain consequences for ecosystem and human health. It is crucial to promote and improve existing analytical techniques to facilitate the detection of trace amounts of PFAS in diverse environmental matrices. This review summarizes analytical methods that have been applied to and advanced for targeted detection and suspect screening of PFAS, which mainly include (i) sampling and sample preparation methods for various environment matrices and organisms, and quality assurance/quality control during the analysis process, and (ii) quantitative methods for targeted analysis and automated suspect screening strategies for non-targeted PFAS analysis, together with their applications, advantages, shortcomings, and need for new method development.

Organic-inorganic hybrid Ruddlesden-Popper perovskites (HRPPs) have gained much attention for optoelectronic applications due to their high moisture resistance, good processability under ambient conditions, and long functional lifetimes. Recent success in isolating molecularly thin hybrid perovskite nanosheets and their intriguing edge phenomena have raised the need for understanding the role of edges and the properties that dictate their fundamental behaviors. In this work, we perform a prototypical study on the edge effects in ultrathin hybrid perovskites by considering monolayer (BA)2PbI4 as a representative system. On the basis of first-principles simulations of nanoribbon models, we show that in addition to significant distortions of the octahedra network at the edges, strong edge stresses are also present in the material. Structural instabilities that arise from the edge stress could drive the relaxation process and dominate the morphological response of edges in practice. A clear downward shift of the bands at the narrower ribbons, as indicative of the edge effect, facilitates the separation of photoexcited carriers (electrons move toward the edge and holes move toward the interior part of the nanosheet). Moreover, the desorption energy of the organic molecule can also be much lower at the free edges, making it easier for functionalization and/or substitution events to take place. The findings reported in this work elucidate the underlying mechanisms responsible for edge states in HRPPs and will be important in guiding the rational design and development of high-performance layer-edge devices. We acknowledge the financial support received from the Nanyang Environment and Water Research Institute (Core Funding), Nanyang Technological University, Singapore. Y. Cai acknowledges the support provided by the University of Macau (SRG2019-00179-IAPME), the Science and Technology Development Fund from Macau SAR (FDCT-0163/2019/A3), the Natural Science Foundation of China (grant 22022309), and the Natural Science Foundation of Guangdong Province, China (2021A1515010024). Nanyang Technological University We acknowledge the financial support received from the Nanyang Environment and Water Research Institute (Core Funding), Nanyang Technological University, Singapore. Y. Cai acknowledges the support provided by the University of Macau (SRG2019-00179-IAPME), the Science and Technology Development Fund from Macau SAR (FDCT-0163/2019/A3), the Natural Science Foundation of China (grant 22022309), and the Natural Science Foundation of Guangdong Province, China (2021A1515010024).

The widespread use of engineered nanomaterials (ENMs) in food products necessitates the understanding of their impact on the gastrointestinal tract (GIT). Herein, we screened several representative food-borne comparator ENMs (i.e. ZnO, SiO2 and TiO2 nanoparticles (NPs)) and report that human colon cancer cells can insidiously exploit ZnO NP-induced adaptive response to acquire resistance against several chemotherapeutic drugs. By employing a conditioning and challenge treatment regime, we demonstrate that repeated exposure to a non-toxic dose of ZnO NPs (20 μM) could dampen the efficacy of cisplatin, paclitaxel and doxorubicin by 10-50% in monolayer culture and 3D spheroids of human colon adenocarcinoma cells. Structure-activity relationship studies revealed a complex interplay between nanoparticle surface chemistry and cell type in determining the chemoresistance-inducing effect, with silica coated ZnO NPs having a negligible influence on the anticancer treatment. Mechanistically, we showed that the pro-survival paracrine signaling was potentiated and propagated by a subset of ZnO NP "stressed" (Zn2++/ROS+) cells to the surrounding "bystander" (Zn2++/ROS-) cells. Transcriptome profiling, bioinformatics analysis and siRNA gene knockdown experiments revealed the nuclear factor erythroid 2-related factor 2 (Nrf2) as the key modulator of the ZnO NP-induced drug resistance. Our findings suggest that a ROS-inducing ENM can emerge as a nano-stressor, capable of regulating the chemosensitivity of colon cancer cells. Nanyang Technological University Published version Nanyang Technological University—Harvard School of Public Health Initiative for Sustainable Nanotechnology (NTU‐Harvard SusNano; NTU-HSPH-18002)

As a class of endocrine disrupting compounds (EDCs), corticosteroids (CSs) have attracted increasing attention due to their large excretion masses and toxic effects. However, compared to the very well-studied estrogens and androgens, few studies have been made dealing with the removal of CSs at environmentally relevant concentrations using advanced water and wastewater treatment processes. In this study, degradation performances of 26 natural and synthetic CSs in secondary effluent at environmentally relevant concentrations were comparatively investigated during UV/free chlorine (UV/Cl2), UV/monochloramine (UV/NH2Cl) and UV/hydrogen peroxide (UV/H2O2) treatments. The 26 CSs could be divided into two groups: UV sensitive CSs, which have two double bonds in ring A (Δ1,4), and UV insensitive CSs, which have only one double bond in ring A (Δ4). The UV sensitive CSs could be effectively removed (removal efficiency >60%) by a UV dose of 100 mJ cm−2 while the UV insensitive CSs could be removed (removal efficiency >40%) by a UV dose of 800 mJ cm−2. The removal efficiencies of UV insensitive CSs increased with the increase of UV dose. Most of the CSs were poorly removed by sole Cl2, NH2Cl, or H2O2 treatment (removal efficiency

Cruciferous vegetables such as kale contain various health-promoting phytochemicals, and leaves rejected from harvesting could be a valuable source of phytochemicals. Conventional organic solvents used for the recovery of these bioactive metabolites are hazardous, and therefore more benign equivalents are sought. This work explores the use of natural deep eutectic solvents (NADESs) with different hydrophilicity/hydrophobicity to recover polyphenols, carotenoids and chlorophylls from kale waste. Enhanced extraction of polyphenols was achieved by the aqueous solutions of hydrophilic glycerol-based NADESs, with yields of up to 2.2-fold higher than just using methanol. The antioxidant capacity of the aqueous extracts showed a strong correlation with their total phenolic contents. The best solvent in extracting polyphenols (glycerol:betaine at a molar ratio of 3:1) was further investigated to optimise its process conditions. The optimised extract provided the greatest stability of the bioactive polyphenols by retaining 91.7 and 88.6% of the original contents after 30 days of storage at 4 and 25 °C, respectively. Furthermore, this extraction approach was integrated with ethyl acetate, a bio-based solvent, to promote the simultaneous recovery of polyphenols (16.83 mg GAE (gallic acid equivalents) g-1 DW (dry weight)), carotenoids (0.91 mg g-1 DW) and chlorophylls (7.86 mg g-1 DW) from kale waste. After extraction, the immiscible aqueous NADES- and ethyl acetate-phases rich in polyphenols and carotenoids/chlorophylls, respectively, can be easily separated for different applications. National Research Foundation (NRF) Submitted/Accepted version This work was supported by the Singapore National Research Foundation (NRF) and the Ministry of Education under the Research Centre of Excellence Program and the NRF Competitive Research Programme (NRF-CRP21-2018-0006).

This study aims to illustrate the effect of hydraulic retention time (HRT) on reactor performance and biofilm characteristics in the gravity-driven membrane (GDM) reactor pretreating seawater. Three GDM reactors were operated in parallel for ~62 days under HRTs of 22 h, 54 h, and 102 h, respectively. The results indicated that the GDM reactors at HRTs of 22 h and 102 h had relatively higher permeate flux and superior permeate quality (especially assimilable organic carbon, AOC) compared to that at HRT of 54 h. Extending HRT benefited to reduce irreversible fouling, but cake layer fouling was maximized at HRT of 54 h. As different HRTs led to significantly dissimilar microbial community structure and cake layer composition, such higher cake layer resistance at HRT of 54 h was attributed to homogenous nature of the biofilm, which contained greater amount of organics and less abundance of Nematoda (dominant predator). Lastly, as increasing ~5-time of HRT (from 22 h to 102 h) improved ~1.5 of permeate flux, a shorter HRT of 22 h was preferable for the GDM reactor in pretreating seawater with regard to treatment productivity and footprint. National Research Foundation (NRF) Public Utilities Board (PUB) This research is supported by the National Research Foundation, Singapore, and PUB, Singapore's National Water Agency under its RIE2025 Urban Solutions and Sustainability (USS) (Water) Centre of Excellence (CoE) Programme, awarded to Nanyang Environment & Water Research Institute (NEWRI), Nanyang Technological University, Singapore (NTU).

This work reported the development, performance and microbial community of microalgal-bacterial biofilms cultivated in a continuous-flow photoreactor for municipal wastewater treatment under various conditions. Results showed that microalgal-bacterial biofilms were successfully developed at a HRT of 9 h without external aeration, with a biofilm concentration of around 4690 mg/L being achieved in the steady-state. It was found that further increase of HRT to 12 h did not improve the overall accumulation of biofilm, whereas the growth of microalgae in biofilms was faster than bacteria in the initial stage, indicated by an increased chlorophyll-a&b content in biofilms. After which, the chlorophyll-a&b content in biofilms gradually stabilized at the level comparable with the seed, suggesting that there was a balanced distribution of microalgae and bacteria in biofilms. About 90% of TOC, 71.4% of total nitrogen and 72.6% of phosphorus were removed by microalgal-bacterial biofilms mainly through assimilation in the steady-state photoreactor run at the HRT of 12 h with external aeration. The community analysis further revealed that Cyanobacteria and Chloroflexi were the main components, while Chlorophyta appeared to be the dominant eukaryotic algal community in biofilms. This study could offer new insights into the development of microalgal-bacterial biofilms in a continuous-flow photoreactor for sustainable low-carbon municipal wastewater treatment.

This study presents a numerical model for the thermal-elastohydrodynamic lubrication of heterogeneous materials in impact motion, in which a rigid ball bounces on a starved non-Newtonian oil-covered plane surface of an elastic semi-infinite heterogeneous solid with inhomogeneous inclusions. The impact–rebound process and the microscopic response of the subsurface inhomogeneous inclusions are investigated. The inclusions are homogenized according to Eshelby’s equivalent inclusion method. The Elrod algorithm is adopted to determine the lubrication starvation based on the solutions of pressure and film thickness, while the lubricant velocity and shear rate of the non-Newtonian lubricant are derived by using the separation flow method. The dynamic response of the cases subjected to constant impact mass, momentum, and energy is discussed to reveal the influence of the initial drop height on the impact–rebound process. The results imply that the inclusion disturbs the subsurface stress field and affects the dynamic response of the contact system when the surface pressure is high. The impact energy is the decisive factor for the stress peak, maximum hydrodynamic force, and restitution coefficient, while the dynamic response during the early approaching process is controlled by the drop height. Nanyang Technological University National Research Foundation (NRF) Published version This research work was conducted in the SMRT-NTU Smart Urban Rail Corporate Laboratory with funding support from the National Research Foundation (NRF), Singapore, SMRT, Singapore and Nanyang Technological University, Singapore. Q.B. also acknowledges the support from National Natural Science Foundation of China, China (Grant No. 51905051).

Hierarchically porous-structured materials show tremendous potential for catalytic applications. In this work, a facile method through the combination of three-dimensional (3D) printing and chemical dealloying was employed to synthesize a nanoporous-copper-encapsulating microporous-diamond-cellular-structure (NPC@DCS) catalyst. The developed NPC@DCS catalyst was utilized as a heterogeneous photo-Fenton-like catalyst where its catalytic applications in the remediation of organic wastewater were exemplified. The experimental results demonstrated that the NPC@DCS catalyst possessed a remarkable degradation efficiency in the removal of rhodamine B with a reaction rate of 8.24 × 10-2 min-1 and displayed attractive stability, durability, mineralization capability, and versatility. This work not only manifests the applicability of the proposed NPC@DCS catalyst for wastewater purification in practical applications but also is anticipated to inspire the incorporation of the 3D printing technology and chemical synthesis to design high-performance metal catalysts with tunable hierarchical micro- and nanopores for functional applications. National Research Foundation (NRF) The authors acknowledge the financial support from the National Natural Science Foundation of China (nos. 51775207 and 51905192), Fundamental Research Funds for the Central Universities (no. 2020kfyXJJS088), and National Research Foundation, Prime Minister’s Office, Singapore under its Medium-Sized Centre funding scheme through the Marine and Offshore Program.

Organic matters commonly exist in the subsoil within the tree rooting zones. The organic content of soil has been known to affect soil properties. In this study, the soil organic contents at various locations around trees were investigated and found to be variable due to the ground flora and tree roots. The range of soil organic content for the current study was between 0.9-12.5%. The objective of this study was to investigate the effects of the organic content on the shrinkage and Soil-Water Characteristic Curve (SWCC) of the soils during rainy and dry seasons when water content of the soil changes. Soil samples were collected from two locations on Singapore Island at depths of 0.1 m and 0.3 m, one site on the western side of the island and the other site at a coastal area along the eastern shore. Centrifuge was used to measure the water content of the specimens at suction up to 250kPa and chilled-mirror psychrometry was used for the higher suction. Shrinkage tests were also conducted to obtain the shrinkage properties. The results show that organic content influenced the shrinkage and SWCC where a higher organic content was associated with a greater shrinkage rate and a higher suction corresponding to the residual water content. For the finer soils, a higher organic content comes with a lower air-entry value. Agency for Science, Technology and Research (A*STAR) Nanyang Technological University National Environmental Agency (NEA) National Parks Board Submitted/Accepted version This research was conducted in collaboration with the National Environment Agency (NEA), National Park Board (NParks), Institute of High-Performance Computing, ASTAR* and Nanyang Environment & Water Research Institute (NEWRI), Nanyang Technological University (NTU), Singapore.

The acid leaching process is a mature technology that can recover valuable metals from the Ni-Co-Mn cathode from spent lithium-ion batteries (LIBs). This work studied the modification of activated biochar using the leaching solution. It was confirmed that the HCl leaching process had a high recovery efficiency of metals (e.g., Li, Ni, Co, Mn) than the H3PO4 leaching process. Furthermore, the modified biochar exhibited excellent catalytic performance in the cellulose-rich biomass (e.g., cardboard waste) pyrolysis. In general, the modified biochar could significantly improve the pyrolysis efficiency in terms of activation energy reduction. The Ea of cardboard waste pyrolysis was decreased from 110.61 kJ/mol to 77.46 kJ/mol. Moreover, the presence of modified biochar could remarkably enhance the transformation of anhydrosugars to hydrocarbons (e.g., long-chain alkanes). Particularly, the modified biochar rich in the transition metals (e.g., Ni) could enhance the conversion of light oxygenates (e.g., aldehydes, ketones) and furans to hydrocarbons. The modified biochar could greatly reduce the content of oxygenated components such as anhydrosugars (e.g., levoglucosenone - LGO), ketones, and aldehydes, which were transformed into light hydrocarbons (e.g., alkenes). The content of hydrocarbons was increased nearly-two times from 12 % to 24 % during pyrolysis of cardboard waste. Therefore, the modified biochar has a high potential to be used in catalytic biomass pyrolysis in the aspects of improving the pyrolysis efficiency and upgrading the pyrolysis products. This work is supported by the Startup Foundation for Introducing Talent of NUIST (2243141501046) and “333 talent” project of Jiangsu Province.

Transmembrane ion fluxes have earlier been identified as a source of potential instability in solid contact ion-selective electrodes (SC-ISEs). In this work, foamlike structures were intentionally introduced into a potassium-sensitive plasticized poly(vinyl chloride) ion-selective membrane (ISM) near the membrane|solid contact interface by controlling the temperature during membrane deposition. Foamlike structures in the ISM were shown to be effective at physically tailoring the transport of ions in the ion-selective membrane, greatly reducing the flux of interfering ions from the sample to the membrane|solid contact interface. The drifts during a conventional water layer test were hence able to be greatly mitigated, even with SC-ISEs incorporating a relatively hydrophilic poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) solid contact. In solutions with a high background concentration of interfering ions, equilibrated ion-selective electrodes with foamlike membranes were able to reproduce their initial potentials within 0.6 mV uncertainty (n = 3) from 0 to 18 h. This was achieved despite sensor exposure to solutions exceeding the selectivity limit of the ISEs in 3 h intervals, allowing improvement of the potential reproducibility of the sensors. Since the introduction of foamlike structures into ISM is linked to temperature-controlled membrane deposition, it is envisaged that the method is generally applicable to all solid contact ion-selective electrodes that are based on polymeric membranes and require membrane deposition from the cocktail solution. Economic Development Board (EDB) Nanyang Technological University Y.H.C. gratefully acknowledges funding from the Economic Development Board (EDB) of Singapore’s Industrial Postgraduate Program in support of this work. The authors thank NEWRI (Nanyang Technological University) and Singapore’s Economic Development Board (EDB) and Robert Bosch SEA for their financial support in this research.

Tuning intermediate adsorption energy by shifting the d-band center offers a powerful strategy to tailor the reactivity of metal catalysts. Here we report a potential sweep method to grow Pd layer-by-layer on Au with the capability to in situ measure the surface structure through an ethanol oxidation reaction. Spectroscopic characterizations reveal charge-transfer induced valence band restructuring in the Pd overlayer, which shifts the d-band center away from the Fermi level compared to bulk Pd. Precise overlayer control gives the optimal bimetallic surface of two monolayers (ML) Pd on Au, which exhibits more than 370-fold mass activity enhancement in oxygen reduction reaction (at 0.9 V vs. reversible hydrogen electrode) and 40 mV increase in half-wave potential compared to the Pt/C. Tested in a homemade Zn-air battery, the 2-ML-Pd/Au/C exhibits a maximum power density of 296 mW/cm2 and specific activity of 804 mAh/gZn, much higher than Pt/C with the same catalyst loading amount. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) This work was supported by the fund from the Singapore Ministry of Education Academic Research Fund (AcRF) Tier 1: RG4/20 and Tier 2: MOET2EP10120-0002, and Agency for Science, Technology, and Research (A*Star IRG: A20E5c0080).

Knowing the energetic topology of a surface is important, especially with regard to membrane fouling. In this study, molecular computations were carried out to determine the energetic topology of a polyvinylidene fluoride (PVDF) membrane with different surface wettability and three representative probe molecules (namely argon, carbon dioxide and water) of different sizes and natures. Among the probe molecules, water has the strongest interaction with the PVDF surface, followed by carbon dioxide and then argon. Argon, which only has van der Waals interactions with PVDF, is a good probing molecule to identify crevices and the molecular profile of a surface. Carbon dioxide, which is the largest probing molecule and does not have dipole moment, exhibits similar van der Waals and electrostatic interactions. As for water, the dominant attractive interactions are electrostatics with fluorine atoms of the intrinsically hydrophobic PVDF membrane, but the electrostatic interactions are much stronger for the hydroxyl and carboxyl groups on the hydrophilic PVDF due to strong dipole moment. PVDF only becomes hydrophilic when the interaction energy is approximately doubled when grafted with hydroxyl and carboxyl groups. The energetic heterogeneity and the effect of different probe molecules revealed here are expected to be valuable in guiding membrane modifications to mitigate fouling. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Published version We acknowledge funding from the A*STAR (Singapore) Advanced Manufacturing and Engineering (AME) under its Pharma Innovation Programme Singapore (PIPS) program (A20B3a0070), A*STAR (Singapore) Advanced Manufacturing and Engineering (AME) under its Individual Research Grant (IRG) program (A2083c0049), the Singapore Ministry of Education Academic Research Tier 2 Grant (MOE-MOET2EP10120-0001) and the Singapore Ministry of Education Academic Research Tier 1 Grant (2019-T1-002-065).

Underwater light availability is a crucial aspect for the ecological functioning of shallow water bodies. Light extinction from terrestrial inputs is a growing threat to these coastal habitats. The blended quasi-analytical algorithm (QAA) was extended for the derivation of colored dissolved organic matter (CDOM) absorption coefficient along with other inherent optical properties (IOPs) from satellite observations for Southeast Asian waters. The contribution of these IOPs to diffuse attenuation of light (Kd) and penetration depth (Zd) was investigated. A vulnerability assessment was performed to identify locations potentially threatened by poor light quality in Southeast Asian waters. Advection of peatland-influenced Sumatran coastal waters rich in organic matter (ag(400nm): 1.0-2.0m-1) and sediments (bbp(400nm): 0.5-1m-1) drive the spatial heterogeneity of Sunda shelf seawater. Photic zone depth, Zd(490nm), is year-round restricted to ≤5m for critically vulnerable Sumatran coastal waters (vulnerability index, VI>0.8). This critically vulnerable state is further extended towards the southern Malacca Strait, influencing the eastern Singapore Strait from June to September. The areas harbouring marine ecosystems in the shelf waters attain a higher threshold (VI=0.6-0.8), constraining the photosynthesis to depths ≤10m. A transformation of central Malacca Strait from not vulnerable (VI

The impacts of climate change and global warming have become more visible globally because of the increasing frequency of extreme weather events, abnormal heatwaves, and other climate crises. Besides the traditional survey method, it is beneficial to automatically distillate climate change opinions from social platforms to measure public reactions quickly. We investigate how to organize climate change opinions on Twitter into meaningful categories to support perspective summarizing tasks. We find that merely using the available taxonomy for this task is ineffective; hence we must consider the entire text content. We recommend five high-level categories (Root cause, Impact, Mitigation, Politics or Policy, Others) and assemble ClimateTweets, a dataset with category and polarity labels. In addition, we construct category classification and polarity detection tasks with a range of opinion mining baselines. The experimental results show that both tasks are challenging for existing models. We release the ClimateTweets dataset to facilitate investigation in public opinion mining using text content and artificial intelligent methods. We hope this study could pave the way for future studies in the climate change domain. Nanyang Technological University Submitted/Accepted version Cuc Duong is supported by Nanyang Research Scholarship.