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Through the addition of a solid-state precursor, a large-scale, transparent, and free-standing film of 1-D rutile/anatase TiO2 nanorod arrays can be fabricated by dynamically changing the acidity and concentrations of titanium and chloride ions, and creating anatase growth-friendly conditions. [ABSTRACT FROM AUTHOR]

Geochemical variations of sedimentary records contain vital information for understanding paleoenvironment and paleoclimate. However, to obtain quantitative data in the laboratory is laborious, which ultimately restricts the temporal and spatial resolution. Quantification based on fast-acquisition and high-resolution provides a potential solution but is restricted to qualitative X-ray fluorescence (XRF) core scanning data. Here, we apply machine learning (ML) to advance the quantification progress and target calcium carbonate (CaCO3) and total organic carbon (TOC) for quantification to test the potential of such an XRF-ML approach. Raw XRF spectra are used as input data instead of software-based extraction of elemental intensities to avoid bias and increase information. Our dataset comprises Pacific and Southern Ocean marine sediment cores from high- to mid-latitudes to extend the applicability of quantification models from a site-specific to a multi-regional scale. ML-built models are carefully evaluated with a training set, a test set and a case study. The acquired ML-models provide better results with R2 of 0.96 for CaCO3 and 0.78 for TOC than conventional methods. In our case study, the ML-performance for TOC is comparably lower but still provides potential for future optimization. Altogether, this study allows to conveniently generate high-resolution bulk chemistry records without losing accuracy. [ABSTRACT FROM AUTHOR]

• The sorbent with improved amine molecules dispersion was fabricated. • The capture capacity loss was insignificant after 20 cycles capture-regeneration test. • The outstanding selectivity toward CO 2 under CO 2 /N 2 mixture was presented. The modification of ordered mesoporous carbon (OMC) via NH 3 heat treatment and subsequent amine refluxing at increased temperature was investigated to improve their performances for cyclic CO 2 /N 2 separation stability and kinetics. Characterizations conducted with nitrogen adsorption/desorption isotherm, Fourier transform infrared spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy demonstrated that the porosity and surface chemistry of the OMCs were tuned by modification. Adsorption evaluation with volumetric and gravimetric methods under various conditions indicated that the resulting amine-introduced N-doped OMC presented a high CO 2 adsorption capacity with fast kinetics, outstanding selectivity at 50 °C and maintained superior separation performance after 20 cycles. The presence of accessible amino groups in considerable amounts renders the modified mesoporous carbon a promising candidate for CO 2 capture from flue gas by using the temperature swing adsorption. [ABSTRACT FROM AUTHOR]

A single-pass-mode capacitive deionization (CDI) reactor was used to remove arsenic from groundwater in the presence of multiple ions. The CDI reactor involved an applied voltage of 1.2 V and six cell pairs of activated carbon electrodes, each of which was 20 × 30 cm 2 . The results indicate that this method achieved an effluent arsenic concentration of 0.03 mg L −1 , which is lower than the arsenic concentration standard for drinking water and irrigation sources in Taiwan, during the charging stage. Additionally, the ability of the CDI to remove other coexisting ions was studied. The presence of other ions has a significant influence on the removal of arsenic from groundwater. From the analysis of the electrosorption selectivity, the preference for anion removal could be ordered as follows: NO 3 − > SO 4 2− > F − > Cl − >As. The electrosorption selectivity for cations could be ordered as follows: Ca 2+ > Mg 2+ > Na + ∼ K + . Moreover, monovalent cations can be replaced by divalent cations at the electrode surface in the later period of the electrosorption stage. Consequently, activated carbon-based capacitive deionization is demonstrated to be a high-potential technology for remediation of arsenic-contaminated groundwater. [ABSTRACT FROM AUTHOR]

This study employs in-situ X-ray absorption spectroscopy (XAS) and operando Raman to explore the reaction mechanism of copper/titanium dioxide microspheres (CuTMS) in CO oxidation. A temperature-dependent hysteresis behavior was observed during catalytic CO oxidation, which can be divided into two distinct regions. In the low-temperature region, the transformation of CuO → Cu 2 O → Cu 2 O/Cu on the surface of CuTMS is detected via in-situ XAS, highlighting the pivotal role of surface-adsorbed oxygen in initiating this conversion process. Conversely, in the high-temperature region, analysis of Raman peak areas suggests a variation in the {001} and {101} facets of anatase. Specifically, a decrease in the {001} facets from 17% to 10% indicates TiO 2 -mediated oxygen transportation, which facilitates the reoxidization of reduced Cu species. This integrated approach showcases significant potential for unraveling the mechanistic studies of catalytic reaction mechanisms in copper/titanium systems, including surface copper valence state changes, oxygen replenishment, and crystal structure distortion. [Display omitted] • Oxygen replenishment behaviors relate to conversion temperature. • Observation of CuO → Cu 2 O → Cu 2 O/Cu transformation at low-temperature region. • Anatase E g(1) mode changes highly related to CO oxidation performance in operando Raman monitoring. • CuTMS structural distortion leads to crystal facets ratio of {001} slightly decrease from 17% to 10%. [ABSTRACT FROM AUTHOR]

Rational design of nanocomposite electrode materials with high conductivity, activity, and mechanical strength is critical in electrocatalysis. Herein, freestanding, flexible heteronanocomposites were fabricated in situ by carbonizing electrospun fibers with TiO 2 nanoparticles on the surface for electrocatalytic degradation of water pollutants. The carbonization temperature was observed as a dominant parameter affecting the characteristics of the electrodes. As the carbonization temperature increased to 1000 °C, the conductivity of the electrode was significantly enhanced due to the high degree of graphitization (I D /I G ratio 1.10) and the dominant rutile phase. Additionally, the formation of TiO 2 protrusions and the C-Ti heterostructure were observed at 1000 °C, which contributed to increasing the electrocatalytic activity. When 1.5 V (vs. Ag/AgCl) was employed, electrocatalytic experiments using the electrode achieved 90% degradation of crystal violet and 10.9–87.5% for an array of micropollutants. The electrical energy-per-order (EEO) for the removal of crystal violet was 0.7 kWh/m3/order, indicative of low-energy requirement. The efficient electrocatalytic activity can be ascribed to the fast electron transfer and the strong ability to generate hydroxyl radicals. Our findings expand efforts for the design of highly conductive heteronanocomposites in a facile in situ approach, providing a promising perspective for the energy-efficient electrocatalytic degradation of water pollutants. [Display omitted] • Flexible electrode was prepared by carbonizing TiO 2 decorated electrospun fibers. • The nanocomposite has high conductivity and a C-Ti heterostructure. • The highest electrocatalytic activity was obtained at a low voltage of 1.5 V. • Pollutant degradation by the electrogeneration of hydroxyl radicals was studied. • The electrocatalytic process can be powered by a solar PV system. [ABSTRACT FROM AUTHOR]

[Display omitted] • The NF/Cu x Pd y electrodes were tailored using the electrodeposition method. • The NF/Cu 63 Pd 37 electrode showed superior performance in the NO 3 − electroreduction. • The flow-through electrode system for nitrate electroreduction was established. • This study compared NO 3 − electroreduction in the flow-through and flow-by systems. • Enhanced reactivity of NO 3 − removal was observed in the flow-through system. NO 3 − pollution in water and wastewater is a pressing global environmental issue, leading to the deterioration of water quality and an increased risk to human health. Herein, we present a three-dimensional (3D) flow-through electrode composed of electrodeposited Cu-Pd bimetallic catalysts on a nickel foam. The Cu-Pd bimetallic particles exhibited cluster-like shapes on the surface of the nickel foam. This electrode design enhanced the electrochemical activity of the NF/Cu 63 Pd 37 electrode for NO 3 − reduction, as evidenced by linear sweep voltammetry (LSV) measurements. By tailoring the Cu-Pd ratio (Cu:Pd 0.63:0.37), the NF/Cu 63 Pd 37 electrode showed the highest reactivity of NO 3 − reduction and selectivity (43.1 %) toward N 2. Importantly, the NF/Cu 63 Pd 37 electrode not only achieved over 99 % NO 3 − removal but also exhibited a higher kinetic rate constant of 1.44 h−1 in the flow-through mode. In contrast, in the flow-by mode, NO 3 − removal was 67.5 % with a lower reaction rate constant of 0.30 h−1. Furthermore, the NF/Cu 63 Pd 37 electrode exhibited a reduced energy consumption (E EO) of 6.86 kWh m−3 order−1 in the flow-through mode, contrasting with 13.66 kWh m−3 order−1 in the flow-by mode. Moreover, the results also demonstrated successful NO 3 − remediation across various initial pH values (pH 3, 6, 9, and 11) and NO 3 − concentrations (100, 200, and 300 mg L−1). The results of this study highlight that the 3D Cu-Pd bimetallic flow-through electrode, with its high reactivity in reducing NO 3 −, marks a significant advancement in efficiently treating nitrate-contaminated water. [ABSTRACT FROM AUTHOR]

An integrated process of filtration and electrosorption was first applied to enable high-performance arsenic removal for groundwater remediation. An active manganese dioxide-rice husk biochar composite (active BC) filter was utilized for oxidization of As(III) to As(V) and initial removal of As(III, V). Subsequently, electrosorption by capacitive deionization (CDI) was applied as a posttreatment to improve arsenic removal. The active BC approach exhibited fast removal rates of 0.75 and 0.63 g mg–1 h–1 and high maximum removal capacities of 40.76 and 48.15 mg g–1 for As(III) and As(V), respectively. Importantly, column experiments demonstrated that the arsenic removal capacity in the active BC filter was 2.88 mg g–1, which was 72 times higher than that of BC. The results were due to the high efficiency (94%) of redox transformation of As(III) to As(V). The electrosorptive removal of arsenic was further controlled by changing the voltage in CDI. With a charging step of 1.2 V, the total arsenic concentration can be reduced to 0.001 mg L–1 with a low energy consumption of 0.0066 kW h m−3. Furthermore, the integrated system can remove As from real groundwater to achieve the World Health Organization guideline value for drinking water quality. [Display omitted] • An active BC filter and CDI were first integrated. • As removal was critically controlled through the integrated system. • The active BC filter exhibited outstanding preoxidation and removal of As(III). • CDI can further remove As to meet drinking water standards. [ABSTRACT FROM AUTHOR]

• The silica supported niobium oxide possessed abundant acid active sites. • The relationship between synthesis parameters and acid properties was investigated. • In-situ experimental trials were introduced to understand the catalytic mechanism. The silica supported niobium oxide catalysts with abundant acid active sites were successfully fabricated and demonstrated catalytic activity in the acetalization of glycerol with acetone to produce solketal. Although Niobium pentachloride which was used as the niobium precursor preferred to aggregate on the surface, the chemical vapor deposition method was introduced to remove the surface chloride. The synthesis parameter of the material affects the structure and the type of the supported niobium oxide on the carrier, and directly changes the amounts of catalytic sites. The effect of calcination temperature/time and loading amount of hydrated niobium oxide on the catalytic performance was investigated. The properties of acid sites on catalysts were characterized, and the catalytic process was directly observed by operando Raman. These in-situ experimental trials could provide deep insight to understand the catalytic mechanism. [ABSTRACT FROM AUTHOR]

This study presents a proof-of-concept data reduction and analysis protocol that can be applied to the study of polluted sediments. Sediment cores from the Nankan River estuary are used as an example of how the protocol can be employed to quantify temporal heavy metal variability. The measurement protocol produces more detailed elemental profiles than conventional techniques using a combination of data transformation techniques and multivariate analysis. Conventional sediment analyses are used to confirm the robustness of the protocol by comparisons of heavy metal concentrations. X-ray fluorescence (XRF) core scanning provides rapid, high-resolution elemental profiles from sediment cores. The technique relies on a variety of calibration methods (ratio, additive and centred log-ratio) to transform the raw data and reduce bias caused by matrix and closed-sum effects. We further test all these calibration approaches since the transformation process is an essential step for the follow up multivariate analyses. The combination of principal component and cluster analysis objectively assesses the information implicit in the dataset. The settings in each procedure are optimized to account for the variance of the dataset. This optimization protocol explains the heavy metal trends using the sediment characteristics of the cores. Heavy metal pollution is characterized by three periods and classified by their oxidation states. We show that heavy metals have an affinity with fine-grained sediments and Mn. The interpretation is confirmed by grain size analysis and inductively coupled plasma optical emission spectrometry (ICP-OES) measurements. This study provides an impartial, cost- and time-effective protocol suitable for the analysis of other heavy metal polluted sites and further studies using sediment cores as archives. [ABSTRACT FROM AUTHOR]

Hollow core-shell mesoporous TiO 2 microspheres were synthesized by a template-free solvothermal route for efficient photocatalytic degradation of acetaminophen. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Barrett–Joyner–Halenda data revealed a micrometer-sized mesoporous anatase TiO 2 hollow sphere with large surface area and efficient light harvesting. For the photocatalytic degradation of acetaminophen in 60 min, the conversion fraction of the drug increased from 88% over commercial Degussa P25 TiO 2 to 94% over hollow spheres with about 25% increase in the initial reaction rate. Even after 10 repeated runs, the recycled hollow spheres showed good photodegradation activity. The intermediates generated in the photocatalytic reactions were eventually converted into molecules that are easier to handle. The simple fabrication route would facilitate the development of photocatalysts for the decomposition of environmental contaminants. [ABSTRACT FROM AUTHOR]

Hierarchical branched ZnO nanorod (B-ZnR) arrays as an electrode for efficient photoelectrocatalytic degradation of paracetamol were grown on fluorine-doped tin oxide substrates using a solution route. The morphologic and structural studies show the ZnO trunks are single-crystalline hexagonal wurtzite ZnO with a [0001] growth direction and are densely covered by c -axis-oriented ZnO branches. The obvious enhancement in photocurrent response of the B-ZnR electrode was obtained than that in the ZnO nanoparticle (ZnO NP) electrode. For the photoelectrocatalytic degradation of paracetamol in 20 h, the conversion fraction of the drug increased from 32% over ZnO NP electrode to 62% over B-ZnR arrays with about 3-fold increase in initial reaction rate. The light intensity-dependent photoelectrocatalytic experiment indicated that the superior performance over the B-ZnR electrode was mainly ascribed to the increased specific surface area without significantly sacrificing the charge transport and pollutant diffusion efficiencies. Two aromatic intermediate compounds were observed and eventually converted into harmless carboxylic acids and ammonia. Hierarchical tree-like ZnO arrays can be considered effective alternatives to improve photoelectro degradation rates without the need for expensive additives. [ABSTRACT FROM AUTHOR]

A modified successive ionic layer adsorption and reaction (SILAR) process was used for deposition of coupled CdS and CdSe quantum dots (QDs) on the surface of orientated ZnO nanorod arrays. This solution-based process provides a conformal and homogeneous QDs deposition along the ZnO nanorod arrays with no entry clogging. The prepared multi-heterojunction CdSe/CdS/ZnO nanorod-arrayed photoanodes are highly visible-light-sensitive and show improved ion diffusion and effective suppression of electron–hole pair recombination. For photoeletrochemical solar water splitting, the photoanode prepared using the modified SILAR outperformed that using the conventional SILAR by >15% improvement in solar-to-hydrogen conversion efficiency. [ABSTRACT FROM AUTHOR]

• Coexisting isolated CuO and Cu–O–Ti were synthesized via one-step AASA. • Long-term stability (250 °C, 200 h) on CO oxidation mineralization. • Estimated temperature-dependence TOF summarized the effects of active sites. • Isolated CuO contributed to the initiation of the reaction at about 50 °C. • CO oxidation was dominated by the interfacial site of Cu–O–Ti. Although the low-temperature reaction mechanism of catalytic CO oxidation reaction remains unclear, the active sites of copper play a crucial role in this mechanism. One-step aerosol-assisted self-assembly (AASA) process has been developed for the synthesis of mesoporous Cu-doped TiO 2 microspheres (CuTMS) to incorporate copper into the TiO 2 lattice. This strategy highly enhanced the dispersion of copper from 41.10 to 83.65%. Long-term stability of the as-synthesized CuTMS materials for catalytic CO oxidation reaction was monitored using real-time mass spectrum. Isolated CuO and Cu-O-Ti were formed as determined by X-ray photoelectron spectroscopy (XPS). The formation of the Cu-O-Ti bonds in the crystal lattice changes the electron densities of Ti(IV) and O, causing a subsequent change in Ti(III)/Ti(IV) and O non /O Total ratio. 20CuTMS contained the highest lattice distortion (0.44) in which the O non /O Total ratio is lowest (0.18). This finding may be attributed to the absolute formation of the Cu-O-Ti bonds in the crystal lattice. However, the decrease of Ti(III)/Ti(IV) ratio to about 0.35 of 25CuTMS was caused by the CuO cluster formation on the surface. N 2 O titration-assisted H 2 temperature-programmed reduction and in-situ Fourier transform infrared spectroscopy revealed the properties of copper and effects of active sites. [ABSTRACT FROM AUTHOR]

Conventional pollution monitoring strategies for heavy metals are often costly and unpractical. Innovative sampling and analytical approaches are therefore needed to efficiently monitor large areas. This study presents a novel, simple, fast, and inexpensive method to monitor heavy metal pollution that uses cation-exchange resin sachets and the micro-XRF core-scanning technique (XRF-CS). The resin passive samplers act as concentrators of cationic species and can be readily deployed spatially and temporally to record pollution signals. The large number of analytical tasks are then overcome by the fast and non-destructive XRF-CS to precisely assess elemental concentrations. Quantifying element loading involves direct comparison with a set of identically prepared and scanned resin reference standards containing Ca, Ti, Cr, Mn, Ni, Cu, Zn, Pb. The results show that within the test range (from 0–1000 s mg kg−1), the calibration lines have excellent regressions (R2 ≥ 0.97), even at the shortest exposure time (1 s). A pilot field survey of a suspected polluted area in central Taiwan, where 30 resin sachets had been deployed, identified a pollution hot spot in a rapid and economical manner. Therefore, this approach has the potential to become a valuable tool in environmental monitoring and forensics. [ABSTRACT FROM AUTHOR]

We investigated the ammonium removal abilities of natural and synthetic zeolites with distinct Si/Al ratios and various surface areas to study how adsorption and ion exchange processes in zeolites perform under different ammonium concentrations and different temperatures. Five zeolites—natural mordenite, chabazite, erionite, clinoptilolite, and synthetic merlinoite—were immersed in 20, 50, and 100 mg/kg ammonium solutions. The results demonstrate that zeolites under high ammonium concentrations (100 mg/kg) possess higher physical adsorption capacity (0.398–0.468 meq/g), whereas those under lower ammonium concentrations (20 mg/kg) possess greater ion exchange properties (64–99%). The ion exchange ability of zeolites is extremely dependent on the cation content of the zeolites, and the cation content is affected by the Si/Al ratio. The surface area of zeolites also has a partial influence on its physical adsorption ability. When the surface area is less than 100 m2/g, the adsorption ability of zeolite increases obviously with surface area; however, adsorption ability is saturated as the surface area becomes larger than this critical value of 100 m2/g. When we placed the zeolites in 50 mg/kg ammonium concentration at different temperatures (5–50 °C), we found that the zeolites exhibited the highest ammonium removal ability at 30 °C and the potassium release was enhanced at 30–40 °C. [ABSTRACT FROM AUTHOR]