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Abstract: Fabricating materials with nacre-like structure have received considerable attention as it shows an excellent combination of mechanical strength and toughness. A considerable number of researchers have reported the preparation method of bionic structure, such as layer-by-layer assembly, vacuum filtration, coextrusion assembly, electrophoresis deposition, water-evaporation-induced assembly, 3D printing, and freeze casting. Compared with other techniques, freeze casting, known as ice templating, is an environmentally friendly, prolongable, and potential method, so it has been rapidly developing and widely researched in recent decades. In this review, the front six methods with their benefits and limitations are briefly introduced. Then, the freeze casting technique with the preparation process and modified technique is emphatically analyzed. Finally, the future tendencies of materials application and technique application are discussed. Freeze casting consists of suspension preparation, solidification, sublimation, and post-treatment processes. The mechanism and influence of parameters during suspension preparation and solidification processes are principally discussed. It must be pointed out that the performance and structure of samples are closely related to the model and external force. Besides, the adjustable process parameters of freezing casting are a strong guarantee of obtaining the target product. The purpose of this review is to promote freeze casting workers to understand the influence of parameters and enlighten them in new experimental designs.

Biochar as an absorbent is used to remove heavy metals from industrial wastewater, while the disposal of the residual has received little attention. This study attempted to convert the waste Ni-laden biochar into the pseudo-capacitive materials by hydrothermal treatment, investigated the optimal temperature (90–180 °C) and Ni content (100 and 500 mg g− 1), and explored the role of Ni-C interactions in the formation of the pseudo-capacitive materials. The highest pseudo-capacitance of 386.7 F g− 1 was obtained with the highest Ni content and the lowest temperature. The high temperature (180 °C) induced thicker lamellar crystal Ni(OH)2, while thinner flower-like Ni(OH)2 crystal was observed at 90 °C. Low temperature enabled the Ni(OH)2 crystals to disperse homogeneously on the carbon surface. The infrared spectroscopy showed that Ni promoted the disappearance of functional groups, indicating the catalytic effect of Ni on carbon structure, which also benefited their recrystallization and mutual encapsulation. Moreover, a combination of X-ray diffraction and thermogravimetry verified that Ni inserted into biochar graphite layer and enlarged the layer distance. This study provides a strategy for transforming hazardous nickel-laden biochar into the capacitive material and reveals that nickel can amplify the graphite layer and improve the stability of biochar-based pseudo-capacitive material during the hydrothermal treatment. Graphical Abstract

Microplastics (MPs) are ubiquitous in aquatic ecosystems and can significantly influence the growth, aggregation and functions of phytoplankton biomass. However, variations in the extracellular polymeric substances (EPS) of phytoplankton in terms of compositions and structures in response to MPs were still not reported. In this study, EPS matrix of Microsystis aeruginosa was applied and fractionated into loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) fractions, with the time-dependent changes in response to different concentrations (10, 100 and 500 mg/L) of MPs being explored via using the fluorescence excitation emission matrix coupled with parallel factor (EEM-PARAFAC) and two-dimensional Fourier transform infrared correlation spectroscopy (2D-FTIR-COS) analysis. Results showed that 500 mg/L of MP concentration significantly inhibited Microcystis growth by 30.5% but enhanced EPS secretion. In addition, organic composition in LB-EPS and TB-EPS varied differently in response to increased MP exposure, as the ratio of polysaccharide/protein increased in the TB-EPS but decreased in LB-EPS. Further analysis revealed obvious heterogeneities in organic component variations in response to MPs, as the C-O functional groups and glycosidic bonds in the TB-EPS preferentially responded, which lead to the domination of polysaccharides and humus substances; while the carbonyl, carboxyl and amino functional groups in the LB-EPS exhibited a preferential response, which caused the enhanced percentage of the tryptophan-like proteins. In addition to organic compositions, the aromaticity, hydrophobicity and humification in the LB-EPS fraction increased with enhanced MP exposure, which, as a result, may influence the ecotoxicological risk of MPs. Therefore, Microcystis can dynamically adjust not only the EPS contents but also the compositions in response to MPs exposure. The results can improve our understanding on the eco-physiological impact of phytoplankton-MP interaction in aquatic environment, and indicate that the dose-dependent and long-term effects of MPs on phytoplankton should be considered in future study.

Heavy metals were typical contaminants in aquatic ecosystems, while their effects on the biotoxicity and metabolism of algal cells in the presence of organic ligands were still unclear. In this study, the contrasting effects of Cu and humic acids (HA) on the growth inhibition, oxidative stress and extracellular secretion of microalga Chlorella vulgaris were studied at environmentally relevant concentrations of Cu (0~2 mg/L) and HA (0~20 mg/L). Results showed that, with increased Cu addition, the algal growth rate decreased while concentrations of superoxide dismutase and malondialdehyde increased showing evident growth inhibition and oxidative damage in the sole presence of Cu. However, the presence of HA could significantly alleviate the Cu-induced toxicity damage, and higher concentrations of HA exhibited greater alleviation efficiencies. Fluorescence spectroscopy combined with flow field flow fractionation revealed that secretion of 50 kDa~0.45 μm of extracellular protein-like substances was the critical fractions responsible for the biotoxicity alleviation. Analysis of Cu contents within extracellular polymeric substance (EPS) matrix showed that not only the secretion amounts but also the acquisition capacities of EPS matrix decreased due to the addition of HA. This study benefited an in-depth understanding toward the toxicity of heavy metals to aquatic microorganisms in natural waters that contained abundant organic ligands.

Nitrogen (N) is one of the nutrients embedded in biowastes and its speciation in solid–liquid–gas pyrolysis products is closely related to environmental issues such as the greenhouse effect, acid r...

N,O-Bis(tert-butoxycarbonyl)hydroxylamines are readily accessible as imine surrogates, which are bench stable and could quantitatively generate the corresponding imines for in situ applications. An unpresented catalytic asymmetric method for the synthesis of α-amino esters and ketones from novel imine surrogates, N,O-bis(tert-butoxycarbonyl)hydroxylamines, as well as its preliminary mechanistic studies are reported. A variety of optically enriched products were obtained in excellent yields and enantioselectivities (up to 99% yield and >99% ee).

As a porous and carbon material, biochar is focused on respectively in sequestrating carbon and stabilizing metals in soil, while few studies attempted to design biochar for simultaneously achieving these two targets. This study proposed to produce phosphorus-composite biochar for synchronously enhancing carbon sequestration and heavy metals immobilization. Two phosphorus materials from tailings, Ca(H

Dissolved organic matter (DOM) is ubiquitous in natural waters which exhibits obvious effects on the toxicity of heavy metals. However, information on the toxicity of heavy metals in the presence of DOMs with different molecular weights (MWs) was still unclear. In this study, Suwannee river humic acid (SRHA) and algae-derived organic matter (ADOM) were selected as typical terrestrial and microbial DOMs, with the bulk DOMs fractionating into high MW (HMW-, 1 kDa ~ 0.45 μm) and low MW (LMW-, 1 kDa) fractions to explore the MW-dependent heterogeneities in the bioaccumulation of Pb to Chlorella vulgaris. Results showed that, regardless of DOM types, the LMW fraction exhibited more acidic groups and humic-like substances than the HMW counterparts. Presence of bulk DOM can decrease the bioaccumulation of Pb, while the specific effects were MW- and type-dependent. The LMW-SRHA enhanced the bioaccumulation of Pb while the HMW counterpart alleviated the effects. However, both the HMW- and LMW-ADOM can reduce the bioaccumulation of Pb to C. vulgaris. Moreover, the correlation analysis showed a significant positive correlation between the content of phenolic-OH and the adsorbed/internalized amounts of Pb, demonstrating that the phenolic-OH played a critical role in altering the bioaccumulation of Pb. The results obtained in this study suggest that distribution of MWs, number of acidic functional groups, and metal complexation capacity within DOM pool should be considered for the eco-environmental risk assessment of heavy metals in aquatic environments.

Modification of pristine biochars has received increasing attentions due to the significant potential in enhancing adsorption performance. In this work, the co-modification of KOH and KMnO

The oxygenation of Fe(II)-bearing minerals for hydroxyl radicals (HO

Reactive oxygen species (ROS) are omnipresent in natural aquatic environments, and play an important role in biogeochemical cycles. One of the dominant sources of ROS in surface waters was thought to be from dissolved organic matter (DOM) interacting with photochemical process. The properties of DOM were different between the flood and drought periods in lakes; yet, information on how these variations influence ROS photoproduction is unknown. Through a three-year study, the photochemical properties of DOM and the resultant ROS photoproduction between the flood and drought period were determined in the largest freshwater lake in China (Lake Poyang). Results found that quantum yield coefficients of excited triplets (

Colloidal particles in lake waters interact inevitably with cyanobacterial extracellular polymeric substance (EPS), which will change their behavior and fate. Quantitative prediction of the effects of cyanobacterial EPS on colloidal behavior is difficult due to its variability and heterogeneity. To explore the effects of molecular weight (MW) fractions and chemical properties of cyanobacterial EPS on aggregation kinetics of colloidal particles, time-series cyanobacterial samples were collected in Lake Taihu, China, from April to November (during blooming and maintenance period), with the bulk EPS matrix fractionating into low MW (LMW-,1 nm) and high MW (HMW-, 1 nm-0.45 μm) fractions. HMW-EPS was generally characterized with higher absorbance and predominant distribution of protein-like substances, while LMW-EPS contained mainly the humic- and fulvic-like substances. The absorbance, molecular size, and humification degree for each MW fraction consistently increased from April to November, showing obvious temporal variations from blooming period to maintenance period. As for the MW-dependent aggregation behaviors, the HMW-EPS provided better stability against aggregation than the LMW-EPS, and the bulk EPS matrix that consisted of HMW- and LMW-fractions exhibited the effects intermediate between that of each fraction alone. Regardless of MW fractions, the effects of EPS-induced stability enhancement were more evident in maintenance period than in blooming period. Further analysis showed that the colloidal stability was correlated positively with SUVA

Lignocellulose is a promising sustainable alternative fuel and its decomposition is critical for the formation of sediment organic matter. The lignin of lignocellulose limits the access of enzymes to cellulose and slows down the decomposition. Therefore, the development of efficient microbial consortia to deconstruct lignin is of great interest. In this study, a 715-day in situ experiment was performed to investigate the degradation process of macrophyte Phragmites australis debris at different depths of sediments (up to 38 cm) in a eutrophic lake. Although litter mass degradation showed an obvious decreasing tendency as the depth increased, the efficiency of lignin degradation in subsurface sediments was significance higher than that in surface sediments (p

This study proposed a scheme for drinking water treatment residue (DWTR) pretreatment to eliminate concerns about potential unfavorable effects caused by excessive release of nutrients (typically N) during recycling in restoration of a water environment with relatively low pollution (e.g., eutrophic surface water). Inspired by soil washing, the pretreatment scheme was based on washing processes; correspondingly, the N desorption characteristics, possibility of recycling solutions for subsequent desorption, and variations in DWTR adsorption capabilities were investigated. The results showed that N, mainly as ammonia N (NH4+-N), was quickly desorbed from DWTR; the concentrations of desorbed NH4+-N were an order of magnitude higher than those of nitrate N (NO3−-N). After six rounds of desorption, most ion-exchangeable NH4+-N was desorbed, and NH4+-N released from the DWTR (after the desorption test) declined markedly from 11.1 to

The metal binding potential of dissolved organic matter (DOM) is highly related with its inherent properties such as molecular weight (MW). Here sediment DOMs with different origins, i.e., algae- and macrophyte-dominated sediment DOM (named as ASDOM and MSDOM, respectively), were size-fractionated into low MW (LMW-,1 kDa) and high MW (HMW-, 1 kDa~0.45 μm) fractions, with the spectral and metal binding properties in different MW fractions exploring via total organic carbon, absorption spectroscopy, fluorescence parallel factor (PARAFAC) analysis, and Cu(II) titration techniques. The MSDOM contained more organic carbon, lower specific UV absorbance, lower fluorescence index, higher humification index, and lower biological index compared to the ASDOM. As for the MW-fractionated samples, the humic- and fulvic-like fluorophores were mainly distributed in the LMW-DOM, while the protein-like ones were located richly in the HMW-DOM. Thus, obvious MW- and origin-dependent heterogeneities in abundance and spectral properties were observed for sediment DOMs. One humic-like, one fulvic-like, and two protein-like fluorescent components were identified by PARAFAC analysis, with different components exhibiting different variable patterns in response to Cu(II) addition. Irrespective of sample sources, humic- and fulvic-like components had higher condition stability constants (logK

Natural organic matter (NOM), a heterogeneous mixture with various organic components and continuous molecular weight (MW) distribution, is omnipresent in natural waters. To date, understanding of the MW-dependent adsorption fractionation of NOM samples on colloids is limited due to the lack of NOM fractionation and characterization methods. In this study, the ultrafiltration technique was applied to fractionate the bulk NOM samples into low MW (LMW

Anaerobic ammonium oxidation coupled to ferric iron reduction (Feammox) has been assumed to play an important role in nitrogen removal from ecosystems. This study assessed the potential role of Feammox in nitrogen transformation in eutrophic lake sediment using an isotope tracing technique in sediment slurry incubation experiments. Feammox was discovered in eutrophic lake sediment. A significant correlation was found between Feammox rates and iron-reducing rates. Furthermore, the positive correlations between the abundance of iron-reducing bacteria (FeRB), such as Geobacteraceae spp. and Shewanella spp., and Feammox rates indicate that Feammox was mediated by FeRB. The potential rate of Feammox in the isotopic tracer incubation treatment was 0.23-0.43 mg N kg-1 day-1. The estimated nitrogen loss caused by Feammox accounts for 5.0-9.2% of the human-induced N input annually into the eutrophic lake. Feammox alone or coupled with anaerobic ammonium oxidation (anammox) and/or denitrification may have an essential role in the nitrogen cycle within eutrophic lake sediment.

Colloidal particles are omnipresent in lake sediments and substantially influence the retention, transportation, and fate of contaminants in lake ecosystems. In this study, the abundance, chemical composition and adsorption behavior of sedimentary colloids (including total and inorganic colloids) from different ecological regions, were for the first time investigated via ultrasonic extraction, spectral analysis and batch absorption experiments. Results showed that the extraction efficiencies of sedimentary colloids showed an ultrasonic energy-dependent enhancement, and the algae-dominated area contained comparable colloidal abundance with the macrophyte-dominated area (i.e., 198.5 vs. 183.3 mg/g). Despite the different ecosystems, these sedimentary colloids usually had a wide size distribution of 30-200 nm, and were characterized with montmorillonite-, kaolin-, volkonskoite-, and quartz-rich chemical compositions. Batch experiment showed that the total pristine colloids exhibited higher adsorption capacity for Pb(II) than the inorganic colloids both for the macrophyte- and algae-dominated sediments, and the adsorption process followed pseudo-second-order kinetics and Langmuir isotherm, irrespective of different colloidal types. Thus, sedimentary colloids can immobilize the heavy metals in sediment and decrease their release into the water column, which can be considered as a sink for contaminants. This study highlighted the significance of sedimentary colloids in determining the physicochemical properties of lake sediments and in evaluating the environmental behavior and fate of contaminants in lake ecosystems.

The typical harm effect of algal bloom sedimentation is to increase sulfides level in surroundings, threatening aquatic organisms and human health; whereas, P inactivating materials containing sulfate are commonly attempted to be used to immobilize reactive P or to flocculate excessive algae in water columns for eutrophication control. In this study, variations in sulfate reduction during algal bloom sedimentation with the addition of sulfate based inactivating materials was comprehensively assessed based on using Al

Abstract: Rifamycins are considered a milestone for tuberculosis (TB) treatment because of their proficient sterilizing ability. Currently, available TB treatments are complicated and need a long duration, which ultimately leads to failure of patient compliance. Some new rifamycin derivatives, i.e., rifametane, TNP-2092 (rifamycin-quinolizinonehybrid), and TNP-2198 (rifamycin-nitromidazole hybrid) are under clinical trials, which are attempting to overcome the problems associated with TB treatment. The undertaken review is intended to compare the pharmacokinetics, pharmacodynamics and safety profiles of these rifamycins, including rifalazil, another derivative terminated in phase II trials, and already approved rifamycins. The emerging resistance of microbes is an imperative consideration associated with antibiotics. Resistance development potential of microbial strains against rifamycins and an overview of chemistry, as well as structure-activity relationship (SAR) of rifamycins, are briefly described. Moreover, issues associated with rifamycins are discussed as well. We expect that newly emerging rifamycins shall appear as potential tools for TB treatment in the near future.

Dissolved organic matter (DOM) is ubiquitous in aquatic environments, whose behaviors and fate are highly related to the chemical compositions and size distribution. In this study, the UV-induced photodegradation properties of DOMs with different origins (i.e., macrophyte- and algae-derived) were investigated using absorption and fluorescence spectroscopy as well as flow field-flow fractionation (FlFFF). Results showed that, irrespective of DOM origins, the chromophoric components could be more effectively photo-degraded than the non-chromophoric ones. Though the two DOMs were characterized with similar fluorophores, the photodegradation properties showed obvious heterogeneities in DOM origins and molecular weights (MWs). Compared to macrophyte-derived DOM (MDOM), the algae-derived DOM (ADOM) exhibited a higher degradation rate and efficiency due to the abundance of labile components like newborn protein-like substances. The FlFFF results revealed a high photo-preferability of 100 kDa-0.45 μm protein-like MDOM and same photo-sensitivity of the size-fractionated humic-like moieties, testifying the reduction of molecular sizes during the photodegradation. However, the increase in relative percentage for 100 kDa-0.45 μm protein-like components and 5–15 kDa humic-like moieties implied a possible enhancement of molecular sizes for ADOM during the early period (i.e., the first hour) of photodegradation. This study provides new insights into the origin-related heterogeneities in compositions and size distribution for DOM transformation.

Tetracycline (TC) adsorption capacity on pristine biochar was limited. Biochar modification can greatly improve its adsorption amount. In this study, rice straw was mixed with FeCl3·6H2O and urea to prepare a Fe–N modified biochar via a one-pot pyrolysis method at 700 °C. Meanwhile, pristine biochar (RSBC), urea modified biochar (N–RSBC), FeCl3·6H2O-modified biochar (Fe–RSBC) were produced as control. More functional groups, more graphited carbon structure, and magnetic components were observed in Fe–N–RSBC. Compared with RSBC, the surface area, total pore and micropore volume of Fe–N–RSBC increased 3.4-fold, 3.0-fold and 2.3-fold, respectively. The maximum capacity of TC adsorption on Fe-N-RSBC reached 156 mg·g−1, which was 5.4 − fold, 8.2 − fold and 1.9 − fold increase to that of RSBC, N-RSBC, Fe-RSBC, respectively. The mechanism of TC adsorption on Fe-N-RSBC involved pore filling, hydrogen-bond interaction, surface complexation, and π–π interaction. Therefore, Fe-N-RSBC can be used as an effective adsorbent for TC removal from aqueous solution.

As an inevitable by-product of potable water production, drinking water treatment residue (DWTR) recycling to make ceramsite can provide both environmental and economic benefits in constructing filtration treatment system for water environment remediation. Given the varied properties of DWTR from different waterworks, this study aims to identify the key factors affecting ceramsite production from DWTR as main ingredient based on five different DWTR with using clay as the auxiliary material. The results showed that of sintering temperature (500-1000 °C), DWTR:clay ratio (5:5 to 9:1), sintering time (5-60 min), and granule diameter (5-15 mm), the sintering temperature was the key parameter. Increasing temperatures from 500 to 1000 °C gradually promoted DWTR sintering by enhancing Si and Al crystallization, which typically increased the formation of SiO

Pyrolysis process significantly influences the physicochemical properties and potential application of magnetic porous biochars (MPBCs). However, the effects of pyrolysis temperature on the properties of MPBCs as well as substantial adsorption are still unclear. This study reported a facile method to obtain the MPBC from tea waste via pyrolysis of a mixture of hydrochar, KHCO3, and FeCl3·6H2O under different temperatures (500–800 °C), and explored further the adsorption toward tetracycline (TC). Results showed pyrolysis temperature obviously influenced the physicochemical properties of MPBCs, and MPBC pyrolyzed at 700 °C (MPBC-700) has a highest specific surface area (1066 m2 g−1) and pore volume (2.693 cm3 g−1). However, the adsorption potential increased consistently from 59.35 mg g−1 for MPBC-500 to 333.22 mg g−1 for MPBC-800, suggesting that the surface area and pore volume were not the only factors determining TC adsorption. Further analysis showed that the pore-filling, π-π interaction, complexation, and hydrogen bonding contributed together to TC adsorption. Moreover, all MPBCs possessed a high saturation magnetization, indicating the easy separation by an external magnet. Therefore, MPBCs (especially at 700 °C) can act as the excellent adsorbents for contaminant removal due to their high separation, adsorption, and reuse performance.

The properties of biochars and their adsorption performance are highly dependent on the carbonation methods. In this study, five carbonation methods, namely, hydrothermal treatment (HT), direct carbonization (BC), carbonization of hydrochar (HBC), KHCO3 activation carbonation (KBC), and KHCO3 activation carbonation of hydrochar (KHBC), were adopted to prepare tea waste biochars. Adsorption behaviors and mechanisms toward tetracycline (TC) by biochar in the aquatic environment were investigated. The results showed that carbonation methods significantly influence the morphology, carbon structure, chemical composition, and functional groups of the biochars based on the characterization of surface area and pore volume analysis, Fourier Transform Infrared Spectroscopy, Raman spectrum, Scanning Electron Microscope, Transmission Electron Microscope, X-ray photoelectron spectroscopy, X-Ray Diffraction, and elemental analysis. Combination of hydrothermal treatment with KHCO3 activation can significantly increase the surface area and enlarge the pore structure of biochar (KHBC and KBC). The BET of KHCO3-activated BCs nearly increased 280 times (KHBC: 1350.80 m2 g−1; KBC: 1405.06 m2 g−1). BET, total pore volume and micropores volume of biochar has a positive influence on TC adsorption capacity. In addition, all adsorption processes can be well fitted by Langmuir and pseudo-second-order kinetic models. The maximum adsorption capacity of KHCO3-activated BCs nearly increased approximately 40 times (KHBC: 451.45 mg g−1; KBC: 425.17 mg g−1). The dominant mechanisms of biochar-adsorbed TC were pore-filling effect and π–π interactions, followed by hydrogen bonds and electrostatic interactions. Therefore, KHBC has the potential to act as sorbents for TC removal from aquatic environment.

Eutrophication and metal pollution are global environmental problems. The risk of metal pollution is high in the eutrophic lakes because of high mobility of metal in sediments. However, the mechanism of cadmium (Cd) mobility in sediments is still unclear. Here we study the mobilization of Cd in sediments from the eutrophic Lake Taihu via monthly field monitoring of mobile Cd using diffusive gradient in thin films (DGT) and high resolution dialysis (HR-Peeper) techniques. We found a high mobility of Cd in sediments in February and March, resulting from reductive dissolution of Mn oxide mediation by high microbial activities, as shown by the similarities in distribution patterns of DGT-labile Cd and Mn. A two orders of magnitude increase in dissolved Cd concentrations (about 28 μg L−1) was observed in May and June, with dissolved Cd concentrations in overlying water about 110 times higher than the criteria continuous concentration set by Environmental Protection Agency. Hourly changes were found to coincide and correlate between dissolved Cd and dissolved organic matter (DOM) under simulated anaerobic conditions, strongly suggesting that the sudden outbreak of Cd pollution observed in the field resulted from the complexation of DOM with Cd in sediments. This was further supported by the NICA-Donnan model that more than 71% of dissolved Cd in the pore water in May and June was present as Cd-DOM complexes. Three components of DOM including humic-, tryptophan-, and tyrosine-like components in the sediments in June was identified using the fluorescence excitation emission matrix-parallel factor analysis. We found that Cd was stable complexed with tyrosine-like component. The Fourier transform infrared and two-dimensional correlation spectroscopy further revealed that Cd was bound to phenolic O H, alkene C C, alcoholic C O, aromatic C H, and alkene CH groups. Our study effectively promotes the understanding of Cd mobilization in sediments and highlights the risk of sudden Cd pollution events in the eutrophic lakes.

Fe-based materials used to adsorb P are commonly considered to be limited by the increased Fe lability, while Fe in drinking water treatment residue (DWTR) shows stable P adsorption abilities. Accordingly, this study aimed to gain insight into Fe lability in DWTR as compared to FeCl3 and Fe2(SO4)3 using Fe fractionation, EXAFS, and high-throughput sequencing technologies. The results showed that compared to Fe2(SO4)3 and FeCl3, Fe was relatively stable in the DWTR under the effects of organic matter, sulfides, and anaerobic conditions. Typically, the addition of FeCl3 and Fe2(SO4)3 enhanced Fe mobility in sediment and overlying water, promoting the formation of Fe-humin acid and ferrous sulfides (FeS and FeS2). However, the addition of DWTR, even at relatively high doses of Fe, has limited impact on Fe mobility. The addition remarkably increased oxidizable Fe in sediment (by approximately 63%), causing Fe to be dominated by oxidizable and residual fractions (like those in raw DWTR); EXAFS analysis also suggested that Fe-humin acid increased substantially with the addition of DWTR, becoming the main Fe species in sediment (with a relative abundance of 50.1%). Importantly, the Fe distributions were stable in sediment with DWTR added, which demonstrated that organic matter stabilized the Fe in the DWTR. Further analysis indicated that all materials promoted the enrichment of bacterial genera potentially related to Fe metabolism (e.g., Bacteroides, Dok59, and Methanosarcina). Fe2O3 in the FeCl3 and Fe2(SO4)3 groups and Fe-HA in the DWTR group were the key species affecting the microbial communities. Overall, the stabilizing effect of organic matter on Fe in DWTR could be used to develop Fe-based materials to enhance Fe stability for environmental remediation.

Dissolved organic matter (DOM) adsorption on colloid surface occurred ubiquitously in aquatic ecosystems, while variations in molecular weight (MW) distribution during adsorption remained poorly understood. In this study, the adsorption and MW fractionation of aquatic DOMs with different origins (e.g., macrophyte- and algae-derived, MDOM and ADOM, respectively) on colloid surface were examined using total organic carbon, absorption and fluorescence spectroscopy, and flow field flow fractionation (FlFFF) analysis. Both the total organic carbon and spectroscopic results showed the predominant adsorption of DOMs within the first 45 min, which behaved not synchronously with MW fractionation. Quantitative FlFFF analysis further indicated that the organic ligands with different MWs exhibited different adsorption affinities on colloid surface. It was found that 5–15 kDa and 50 kDa0.45 μm were preferential adsorption fraction for humic- and protein-like MDOM, respectively, while 0.3–2 kDa and 0.3–50 kDa were preferential adsorption fraction for humic- and protein-like ADOM, respectively. Therefore, the MW fractionation of DOMs upon adsorption was highly dependent on DOM origins as well as specific components. Results obtained herein can enlarge our insights into adsorption and the resultant behavior and fate of DOMs that were highly related with the MW fractionation in aquatic environments.

We report the synthesis of a series of graphene-induced self-assembly phase transformations of tetragonal β-In2S3 into cubic α-In2S3 at lower temperatures based on the principles of molecular and crystal engineering and a simple one-pot soft integration strategy based on wet chemistry. Controlled contact In2S3/G heterojunction hybrids with sizes ranging from 3D/2D to 2D/2D. In the process, the 3D petal-like In2S3 is transformed into 2D nanosheets grown on the 2D graphene "mat". Due to effective charge separation and close interfacial contact, the excellent visible catalytic purification performance for the degradation of organic pollutants, benzyl alcohol selective oxidation and reduction of Cr2O72- has been achieved. The significantly improved photocatalytic purification efficiency is mainly due to the graphene-induced phase transition which increases the number of active sites and strengthens the two-dimensional/two-dimensional contact of the interface, which promotes the effective transmission and separation of photo-excited carriers, thereby Effectively improve the photocatalytic purification ability. This research provides new insights for the preparation of high-efficiency graphene-based nano-hybrid photocatalysts with controllable structure through rational use of the structure-oriented and induced phase transition effects of graphene, and expands its visible light catalytic purification applications.

The classical lake internal phosphorus (P) pollution control using P-inactivating materials is typically carried out by reducing the release of soluble P from sediments to overlying water; however, particulate P loading through sediment resuspension could also cause internal P pollution for algae breeding. Therefore, based on lanthanum modified bentonite clay (Phoslock®) and drinking water treatment residues (DWTR), the effect of P inactivating materials on sediment resuspension and settlement were comprehensively investigated to assess the variations in particulate P pollution from sediment. Results showed that both materials could effectively control soluble P pollution from sediment, while both had limited effect on the supplement of particulate P to overlying water. The reason may be that hydrodynamic disturbance was the key factor regulating sediment resuspension and settlement. The disturbance induced the resuspension of different sized sediments, especially

Knowledge of the dynamic changes in molecular size of natural colloidal organic matter (COM) along the aquatic continuum is of vital importance for a better understanding of the environmental fate and ecological role of dissolved organic matter and associated contaminants in aquatic systems. We report here the pH- and cation-dependent size variations of COMs with different sources (river and lake) quantified using flow field-flow fractionation (FIFFF), fluorescence spectroscopy and parallel factor analysis (PARAFAC), attenuated total reflectance Fourier transform infrared (ATR–FTIR) spectroscopy, and zeta potential analysis. Increasing pH caused a decline in molecular sizes and an obvious size transformation from the >10 kDa to 5–10 kDa and further to 1–5 kDa size fraction, whereas the opposite trend was observed for increasing cation (e.g., Ca2+ and Cu2+) abundance. Compared with lakewater COM, the riverwater COM exhibited a greater pH-dependent dispersion but less extent in cation-induced aggregation, demonstrating that the dispersion and aggregation dynamics were highly dependent on COM source and solution chemistry (e.g., pH and cations). Based on ATR–FTIR analysis, the extensive dissolution of C=O and C–O functional groups resulted in a greater pH-dependent dispersion for river COM. Fluorescence titration revealed that, despite their similar cation-induced aggregation behavior, the binding constants of all the PARAFAC-derived components for Cu2+ were 1–2 orders of magnitude higher than those for Ca2+ (logKM: 4.54–5.45 vs. 3.35–3.70), indicating a heterogeneous nature in cation-DOM interactions. The greater extent of decline in zeta potential for lake COM suggested a Ca-induced charge neutralization and aggregation mechanism. However, for Cu-induced aggregation, chemical complexation was the predominant pathway for the river COM, with higher binding constants, while charge neutralization and chemical complexation co-induced the aggregation of lake COM. Thus, natural COMs may have different environmental behavior along the aquatic continuum and further affect the fate and transport of contaminants in aquatic environments.

Dissolved organic matter (DOM) in aquatic environment significantly influences the behavior and fate of heavy metals via binding, complexation and thus changes the metal speciation; however detailed interfacial processes and mechanisms are still unclear. Here, differential absorbance and fluorescence spectra and two dimensional UV–FTIR heterospectral correlation analysis were applied to probe into the Pb(II)–DOM interaction at a wide range of pH and ionic strength (IS). The absorbance of DOM molecules under all conditions increased with metal addition, while the different extents of absorbance variations along the wavelength range in the differential zero-order and log-transformed absorbance spectra indicated the site heterogeneity within the DOM pool for metal binding. Spectral parameters, namely differential fluorescent components 1 and 2 (DFC1 and DFC2) and differential slopes of log-transformed absorbance in the range of wavelength 350–400 nm (DSlope350–400) were found to be highly correlated with the total amounts of DOM-bound Pb(II) predicted by the NICA-Donnan model, while the differential absorbance spectra at 235 nm (DA235) was related to the extent of Pb(II) bound by carboxylic groups. Thus, these parameters are an indicator or proxy for the in situ Pb(II)–DOM interaction extent. Aryl C–H gave the fastest response to Pb(II) binding at lower pH and IS (e.g., pH 4.7 and IS = 0.01 M), followed by carboxyl C=O and polysaccharide C–OH and then chromophoric groups at 265 nm (CDOM265). However, the CDOM265 bound to Pb(II) prior to aryl C–H and polysaccharide C–OH groups at higher pH and IS (6.0 and 0.1 M, respectively), showing that the binding sequences were highly dependent on solution chemistry. Differential spectra combined with two dimensional UV–FTIR heterospectral correlation analysis can be used as a promising approach to elucidate metal–DOM interaction processes, including site heterogeneity, binding sensitivity and sequence at the functional group level.