Enriching surface-ordered defects on WO3 for photocatalytic CO2-to-CH4 conversion by water.

Defect engineering has been widely applied in semiconductors to improve photocatalytic properties by altering the surface structures. This study is about the transformation of inactive WO3 nanosheets to a highly effective CO2-to-CH4 conversion photocatalyst by introducing surface-ordered defects in abundance. The nonstoichiometric WO3-x samples were examined by using aberration-corrected electron microscopy. Results unveil abundant surface-ordered terminations derived from the periodic {013} stacking faults with a defect density of 20.2%. The {002} surface-ordered line defects are the active sites for fixation CO2, transforming the inactive WO3 nanosheets into a highly active catalyst (CH4: O2 = 8.2: 16.7 µmol h-1). We believe that the formation of the W-O-C-W-O species is a critical step in the catalytic pathways. This work provides an atomic-level comprehension of the structural defects of catalysts for activating small molecules.

Establishing Multiple-Order Built-In Electric Fields Within Heterojunctions to Achieve Photocarrier Spatial Separation.

Hybridizing two heterocomponents to construct a built-in electric field (BIEF) at the interface represents a significant strategy for facilitating charge separation in carbon dioxide (CO2)-photoreduction. However, the unidirectional nature of BIEFs formed by various low-dimensional materials poses challenges in adequately segregating the photogenerated carriers produced in bulk. In this study, leveraging zinc oxide (ZnO) nanodisks, a sulfurization reaction is employed to fabricate Z-scheme ZnO/zinc sulfide (ZnS) heterojunctions featuring a multiple-order BIEF. These heterojunctions reveal distinctive interfacial structures characterized by two semicoherent phase boundaries. The cathodoluminescence 2D maps and density functional theory calculation results demonstrate that the direction of the multiple-order BIEF spans from ZnS to ZnO. This directional alignment significantly fosters the spatial separation of photogenerated electrons and holes within ZnS nanoparticles and enhances CO2-to-carbon monoxide photoreduction performance (3811.7 µmol h-1 g-1). The findings present a novel pathway for structurally designing BIEFs within heterojunctions, while providing fresh insights into the migratory behavior of photogenerated carriers across interfaces.

Ionic liquid recovery and recycling via electrodialysis in biomass processing: An economical assessment.

Extravagant price and lack of high-efficiency recovery technology limited scale-up utilization of ionic liquids. Ionic liquids recovery with electrodialysis-based techniques has caught wide concern due to membrane-based characteristic. Economical assessment for electrodialysis-based ionic liquid recovery and recycling in biomass processing was performed by determining influence of equipment-related and financial-related factors with sensitivity analysis for each factor. Overall recovery cost of 1-ethyl-3-methylimidazolium acetate, choline acetate, 1-butyl-3-methylimidazolium hydrogen sulphate and 1-ethyl-3-methylimidazolium hydrogen sulfate varied within 0.75-1.96 $/Kg, 0.99-3.00 $/Kg, 1.37-2.74 $/Kg and 1.15-2.89 $/Kg when factors changed within investigated range. Fold of membrane cost, factor of membrane stack cost, factor of auxiliary equipment cost, factor of annual maintenance cost and annual interest rate of loan were positively related with recovery cost. While percentage of annual elapsed time and loan period were negatively correlated with recovery cost. Economical assessment confirmed economic efficiency of electrodialysis for ionic liquids recovery and recycling in biomass processing.

Rh/Cr2 O3 and CoOx Cocatalysts for Efficient Photocatalytic Water Splitting by Poly (Triazine Imide) Crystals.

In situ photo-deposition of both Pt and CoOx cocatalysts on the facets of poly (triazine imide) (PTI) crystals has been developed for photocatalytic overall water splitting. However, the undesired backward reaction (i.e., water formation) on the noble Pt surface is a spontaneously down-hill process, which restricts their efficiency to run the overall water splitting reaction. Herein, we demonstrate that the efficiency for photocatalytic overall water splitting could be largely promoted by the decoration of Rh/Cr2 O3 and CoOx as H2 and O2 evolution cocatalysts, respectively. Results reveal that the dual cocatalysts greatly extract charges from bulk to surface, while the Rh/Cr2 O3 cocatalyst dramatically restrains the backward reaction, achieving an apparent quantum efficiency (AQE) of 20.2 % for the photocatalytic overall water splitting reaction.

The Directional Crystallization Process of Poly (triazine imide) Single Crystals in Molten Salts.

Poly (triazine imide) photocatalysts prepared via molten salt methods emerge as promising polymer semiconductors with one-step excitation capacity of overall water splitting. Unveiling the molecular conjugation, nucleation, and crystallization processes of PTI crystals is crucial for their controllable structure design. Herein, microscopy characterization was conducted at the PTI crystallization front from meso to nano scales. The heptazine-based precursor was found to depolymerize to triazine monomers within molten salts and KCl cubes precipitate as the leading cores that guide the directional stacking of PTI molecular units to form aggregated crystals. Upon this discovery, PTI crystals with improved dispersibility and enhanced photocatalytic performance were obtained by tailoring the crystallization fronts. This study advances insights into the directional assembling of PTI monomers on salt templates, placing a theoretical foundation for the ordered condensation of polymer crystals.

Controllable recovery and recycling of carboxylic acid-polyalcohol deep eutectic solvent for biomass pretreatment with electronically-controlled chemical methodology.

Pretreatment of lignocellulosic biomass using deep eutectic solvent (DES) has been demonstrated environmental and valid. Co-existing of donor and acceptor of hydrogen bond makes DES composition more complicated than traditional solvents, which limits their further scale-up utilization. Advances in biomass pretreatment using green solvent DES should excogitate efficient methodology for DES recycling. Electronically-controlled chemical methodology was first put forward to resolve recovery and recycling issue of DES lactic acid-ethylene glycol after biomass pretreatment. The methodology worked based on selectively migrating of lactate Lac- and reserving of ethylene glycol using BP-A-BP bipolar membrane electrodialysis (BMED). Impact of primary factors on DES recovery was carefully studied. Lowest energy consumption for specific DES recovery reached 10.4 kw·h/kg and highest DES recovery rate approached 97.6 %. Cognition acquired from this research indicated a promising and efficient strategy for carboxylic acid-polyalcohol DES recovery with novel electronically-controlled chemical methodology.

Pd-Sb Rhombohedra with an Unconventional Rhombohedral Phase as a Trifunctional Electrocatalyst.

Crystal phase engineering is an important strategy for designing noble-metal-based catalysts with optimized activity and stability. From the thermodynamic point of view, it remains a great challenge to synthesize unconventional phases of noble metals. Here, a new class of Pd-based nanostructure with unconventional rhombohedral Pd20 Sb7 phase is successfully synthesized. Benefiting from the high proportion of the unique exposed Pd20 Sb7 (003) surface, Pd20 Sb7 rhombohedra display much enhanced ethanol oxidation reaction (EOR) and oxygen reduction reaction performance compared with commercial Pd/C. Moreover, Pd20 Sb7 rhombohedra are also demonstrated as an effective air cathode in non-aqueous Li-air batteries with an overpotential of only 0.24 V. Density functional theory calculations reveal that the unique exposed facets of Pd20 Sb7 rhombohedra can not only reduce the excessive adsorption of CH3 CO* to CH3 COOH on Pd for promoting EOR process, but also weaken CO binding and CO poisoning. This work provides a new class of unconventional intermetallic nanomaterials with enhanced electrocatalytic activity.

Improved Charge Separation in Poly(heptazine-triazine) Imides with Semi-coherent Interfaces for Photocatalytic Hydrogen Evolution.

The construction of heterojunctions is a promising manner to accelerate the separation and transfer of the charge carriers at the interface. Herein, a binary poly(heptazine-triazine) imides (PHI/PTI) with semi-coherent interfaces was fabricated via a facile two-step salt-melt synthetic process. The built-in electric fields at the semi-coherent interface endow prompt exciton splitting and charge carrier separation. Hence, the optimized PHI/PTI-based copolymer presents a high apparent quantum yield (AQY=64 %) for visible-light driven hydrogen production, by the aids of K2 HPO4 as charge transfer mediator. This study provides physical insights for the rational promotion of the photocatalytic performance from the viewpoint of interfacial engineering of photocatalytic junctions on crystalline carbon nitride based semiconductors.

High-efficiency recovery and regeneration of choline-polyol deep eutectic solvent for biorefinery via bipolar membrane electrodialysis and ultrafiltration.

Deep eutectic solvents (DES) have been widely studied for interesting solvent properties in resources utilization and green conversion of energy. Complex composition of DES and lack of recovery techniques restricts their further scale-up application. Exploring efficient recovery and regeneration methodology of DES in biorefinery could be beneficial for low-carbon circular bioeconomy. Recovery and regeneration of choline-polyol DES (choline chloride-ethylene glycol, ChCl-EG) after biomass pretreatment was studied using bipolar membrane electrodialysis (BMED) with ultrafiltration (UF). UF-BMED treatment worked based on the interception of macromolecular degradation products in pretreatment liquor and regional recovery of Ch+, Cl- with EG. Influence of major parameters on DES recovery performance was studied with emphasis. Maximum recovery ratio of DES reached 97.4% and minimum specific energy consumption of DES recovery approached 6.0 kW·h/kg. Cognition gained from this research revealed an efficient technique for DES recycling after biorefinery.

Atomistic Observation of Temperature-Dependent Defect Evolution within Sub-stoichiometric WO3-x Catalysts.

Tunable crystalline defects endow WO3-x catalysts with extended functionalities for a broad range of photo- and electric-related applications. However, direct visualization of the defect structures and their evolution mechanism is lacking. Herein, aberration-corrected and in situ transmission electron microscopy was complemented by theoretical calculations to investigate the effect of temperature on the defect evolution behavior during hydrogenation treatment. Low processing temperature (100-300 °C) leads to the occurrence of randomly distributed oxygen vacancies within WO3-x nanosheets. At higher temperatures, oxygen vacancies become highly mobile and aggregate into stacking faults. Planar defects are prone to nucleate at the surface and develop in a zigzag form at 400 °C, while treating at 500 °C promotes the growth of {200}-type stacking faults. Our work clearly establishes that the atomic configuration of the defects in WO3-x samples could be manipulated by regulating the hydrogenation temperature. This study not only expands our understanding of the structure-function relationships of sub-stoichiometric tungsten oxides but also unlocks their full potential as advanced catalysts by tuning stoichiometry in a controlled manner.

[Pollution status and exposure assessment of lead, cadmium, total mercury and total arsenic in grains on sale from Shaanxi Province, 2002-2018].

OBJECTIVE: To investigate the pollution status of lead, cadmium, total mercury and total arsenic in grains sold in Shaanxi Province, and to analyze the potential risk of dietary exposure. METHODS: A total of 1873 samples of wheat, wheat flour, rice, maize and their products were randomly collected in circulation. The contents of lead and cadmium were determined by atomic absorption spectrophotometry and inductively coupled plasma mass spectrometry, and total mercury and arsenic were determined by atomic fluorescence spectrometry. The pollution status of four elements in grains was evaluated by single factor pollution index method, margin of exposure(MOE) was used to assess lead exposure, cadmium exposure was assessed by the ratio of estimated monthly intake(EMI) to provisional tolerable monthly intake(PTMI), and exposure to mercury and arsenic was assessed using the ratio of estimated weekly intake(EWI) to provisional tolerable weekly intake(PTWI). RESULTS: The average values of lead, cadmium, total mercury and total arsenic in grains sold in Shaanxi Province were 0.070, 0.022, 0.0079 and 0.030 mg/kg. The over-standard rates of lead, cadmium and total mercury were 6.30%, 1.39% and 4.43%. The average single factor pollution index of lead, cadmium, total mercury and total arsenic was less than 0.7; The MOE value of lead in grains was 0.99-18.41, the intake of cadmium in grains accounted for 19.08% of PTMI, and the intake of mercury and arsenic accounted for 10.28% and 10.67% of PTWI. CONCLUSION: Lead, cadmium, total mercury and total arsenic in all kinds of cereals sold in Shaanxi Province from 2002 to 2018 were less polluted and their intake was within the safe range.

High-efficiency recovery, regeneration and recycling of 1-ethyl-3-methylimidazolium hydrogen sulfate for levulinic acid production from sugarcane bagasse with membrane-based techniques.

Ionic liquids have been proven efficient and environmental medium for producing platform chemical levulinic acid. Lack of high-efficiency, stable and low-cost recovery strategy with complex electrolyte form restricts the further scale-up of ionic liquids for platform chemicals production. Membrane-based techniques including ultrafiltration (UF) and bipolar membrane electrodialysis (BMED) were employed for the high-efficiency recovery, regeneration and recycling of 1-ethyl-3-methylimidazolium hydrogen sulfate [Emim][HSO4] for levulinic acid production from sugarcane bagasse. UF-BMED treatment works based on the interception of macromolecule biomass degradation products by UF treatment with regional recovery of Emim+ and SO42- by BMED treatment. Effect of major parameters on [Emim][HSO4] recovery performance was determined. Recovery ratio for Emim+ and SO42- approached 95.4% and 95.9%. Energy consumption of specific [Emim][HSO4] recovery was closed to 5.8 kWh/kg. Insight gained from this study suggests a high-efficiency and economical strategy for platform chemicals production with green solvent ionic liquids.

Quantitative recovery and regeneration of acidic ionic liquid 1-butyl-3-methylimidazolium hydrogen sulphate via industrial strategy for sustainable biomass processing.

Quantitative recovery is necessary for scale-up application of acidic ionic liquids (AILs). Ultrafiltration and bipolar membrane electrodialysis (BMED) was employed for the recovery and regeneration of acidic ionic liquid 1-butyl-3-methylimidazolium hydrogen sulphate (Bmim[HSO4]) after biomass pretreatment. Ultrafiltration was designed for the purification of BMED feed solution. During BMED treatment, Bmim+ retention with OH- generation occurred in mixing section and SO42- immigration with H+ generation occurred in aciding section. Resulting aqueous Bmim[OH] in mixing section and H2SO4 in aciding section could be utilized for quantitative synthesis of Bmim[HSO4]. Influence of BMED operating mode and major parameters including BMED feed concentration and current density of BMED module were studied in detail. The highest recovery ratio for Bmim+ and SO42- reached 96.2% and 96.0%. And the lowest energy consumption of specific Bmim[HSO4] recovery approached 9.0 kw∙h/kg. Insight gained from this study suggested a sustainable biomass processing methodology using AILs.

Accurately-controlled recovery and regeneration of protic ionic liquid after Ionosolv pretreatment via bipolar membrane electrodialysis with ultrafiltration.

Efficient recovery and regeneration of ionic liquid is significant for industrial Ionosolv pretreatment. Complicated electrolyte composition restricts the scale-up recovery and application of protic ionic liquid such as triethylammonium hydrogen sulfate [TEA][HSO4] in biomass-related research. Recovery of [TEA][HSO4] after Ionosolv pretreatment for miscanthus powder was studied using bipolar membrane electrodialysis (BMED) assisted with ultrafiltration (UF) by the divisional recovery of TEA+ as TEA and recovery of SO42- as H2SO4 in different BMED compartments. Hence accurately-controlled regeneration of [TEA][HSO4] could be realized. Influence of current density and feed concentration of BMED module was studied in detail. In this study, the highest recovery ratio for TEA+ and SO42- reached 93.7% and 96.4%. The lowest energy consumption of specific [TEA][HSO4] recovery was about 6.2 kwh/kg. Insight gained from this study suggests a potentially industrial methodology for complicated protic ionic liquid recovery after biomass processing.

[Investigation of pesticides residues in vegetables in the central Shaanxi area, 2012-2018].

OBJECTIVE: To investigate the status of pesticides residues in vegetables in the central Shaanxi area. METHODS: The vegetables collected from central Shaanxi area and the pesticides residues in vegetables were detected by gas chromatography-mass spectrometry during 2012 to 2018. RESULTS: In 1049 samples, the total detection rate of 50 kinds of pesticides residues was 14. 11%, the over standard rate was 1. 91%. The detection rates of pyrethroid, organophosphate, carbamate, organochlorine were 7. 98%, 5. 89%, 3. 30% and 0. 68%, and the over standard rates were 0. 66%, 0. 90%, 0. 70% and 0. 00%, respectively. The highest detection of pyrethroid was cyhalothrin(3. 61%), the highest detection of organophosphate was chlorpyrifos(2. 70%), the highest detection of carbamate was carbofuran(1. 80%), the highest detection rate of organochlorine was endosulfan(0. 68%). The vegetables with higher detection rates were bulbs, fresh beans and stems. The vegetables with higher over standard rates were Chinese chives, cowpeas and celery. CONCLUSION: The pesticides in vegetables are detected in the central Shaanxi area, but the total of exceeding standard is low.

[Contamination and dietary exposure assessment of fatty acid esters of chloropropanediols in vegetable oil and fat-rich food in Shaanxi Province].

OBJECTIVE: To investigate the contamination of chloropropanediols in fat-rich food in Shaanxi Province, and to assess the dietary chloropropanediols exposure and the health risk of intaking chloropropanediols from fat-rich food for Shaanxi residents. METHODS: In 2015-2016, three kinds of food including vegetable oil, fried food and baked food were collected randomly from ten cities of Shaanxi Province, and determined by gas chromatography. Dietary intake assessment of human exposure to 3-monochloropropane-1, 2-diol ester(3-MCPD ester) was carried out in combination of food consumption data with concentration of chloropropanediols. RESULTS: A total of 203 samples were detected, the total detection rates of 3-MCPD ester and 2-monochloropropane-1, 3-diol ester(2-MCPD ester) were 31.53% and 12.30%, respectively, with the mean values of 0.22 and 0.02 mg/kg.Among all food samples, baked food were more seriously polluted than other kinds of foods with 3-MCPD ester, its detection rate was 47.06%. The highest detection rate of 2-MCPD ester was fried food with 20.00% detection rate. Getting rid of rapeseed oil, olive oil, pastries and biscuits, and 2-MCPD esters were detected in the rest. The ratio of the average exposure and high-end exposure to the maximum daily tolerance of 3-MCPD ester in the three fatty foods were less than 100%. CONCLUSION: The overall level of 3-MCPD esters contamination in fat-rich food is common in Shaanxi Province. The risk assessment result suggests that the current dietary intake of 3-MCPD esters from fried food in Shaanxi Province has acceptable effect on health.

[Investigation on the level of dioxin-like compounds in different animal-derived foods from Shaanxi Province].

OBJECTIVE: To investigate the pollution level of dioxin-like compounds in animal-derived foods from 10 cities of Shaanxi Province. METHODS: Collect four representative food samples( pork, beef, fish and eggs) to determine the concentrations of29 types of dioxin-like compounds by high-resolution gas chromatographs/high-resolution mass spectrometers( HRGC-HRMS). RESULTS: The result showed that the toxic equivalent quantity( TEQ) value of dioxin-like compounds in fish was 0. 085 pg TEQ/g, which was the biggest among the 4 food samples. The TEQ values for pork, beef and eggs were 0. 049, 0. 034 and 0. 040 pg TEQ/g, respectively. The TEQ values of dioxin-like compounds were higher in the fish meat of Ankang and the pork of Hanzhoung, but were lower than the max limit of commission regulation European Union. The total dietary intake of the above four foods was 2. 01 pg/( kg·BW·month), which was much lower than the provisional tolerable monthly intake( PTMI) of Joint FAO/WHO Expert Committee on Food Additives 70 pg/( kg·BW·month). CONCLUSION: The residents in the 10 cities of Shaanxi Province are at a low health risk caused by the intake of dioxin-like compounds.

Research on the quick and efficient recovery of 1-allyl-3-methylimidazolium chloride after biomass pretreatment with ionic liquid-aqueous alcohol system.

Membrane-based methodology electrodialysis (ED) was employed for the quick and efficient recovery of ionic liquid AmimCl from the aqueous solutions after biomass pretreatment with AmimCl-aqueous methanol/ethanol systems. IL recovery performance was relatively stable as the variation of IL-alcohol systems employed in the pretreatment process. IL recovery ratio (R) of 66%-71%, IL recovery performance of specific energy consumption (Sp) of 429-467g/kwh and IL transport rate (Tr) of 5.3-8.2g/(m2min) were obtained by single ED treatment. Enhanced IL recovery performance was resulted with the semi-continuous ED-assisted process with R reached 93% and Sp reached 482g/kwh. Based on the characteristics of IL solutions, influence of different AmimCl-based solvents pretreatment on IL recovery was discussed and feasibility of electrodialysis treatment for such IL recovery task was also analyzed. Potential gained from this study suggests a feasible methodology for the quick and efficient recovery of ionic liquid after biomass pretreatment.

[Determination of semi-volatile organic compounds in the source of drinking water by gas chromatography triple quadruples mass spectrometry with auto solid phase extraction].

OBJECTIVE: To establish a method for detecting 21 semi-volatile organic compounds in the source of drinking water by gas chromatography triple quadruples mass spectrometry( GC-MS/MS). METHODS: To process multiple samples at the same time, using large volume solid-phase extraction device for continuous injection. The water samples were extracted by C_(18) solid phase column, eluted with methylene chloride and ethylacetate, and then separated by DB-5MS capillary column. The target substance in the extractions was selected by gas chromatography triple quadruples spectrometry in selectedreaction monitoring( SRM) mode. Retention time and selected ions were used for qualitative analysis, acenaphthene-d_(10), phenanthrene-d_(10) and chrysene-d_(12) were used as internal standard for qualitative analysis of 21 semi-volatile organic compounds. RESULTS: The method was good sensitivity, stability and high selectivity, which could improve the sensitivity of target compounds by secondary mass spectrum scanning through reducing the background interference. The separate rates of 21 kinds of compounds were well, and the correlation coefficients were more than 0. 9902. The minimum detection concentration was 5. 0 × 10~(-5)mg/L, the average recovery rates were 72. 6%-127. 3% and the relativestandard deviation were 1. 05%-9. 89%. CONCLUSION: This method is simple, rapid with high accuracy and reliable, so it is suitable for detecting semi-volatile organic compounds in water.

Recovery of ionic liquid via a hybrid methodology of electrodialysis with ultrafiltration after biomass pretreatment.

Hybrid membrane-based methodology of electrodialysis (ED) with ultrafiltration (UF) was employed to recover the IL BmimBr (1-Butyl-3-methylimidazolium bromide) after biomass fractionation. Ultrafiltration was used to remove the residual lignin in IL solutions. Influence of molecular weight interception of UF treatment, initial IL concentration in dilute section, applied voltage and flow rate in each section of ED module were studied in detail. In this study, the highest overall IL recovery ratio reached 75.2% and the current efficiency of ED process approached 79.1%. Besides, the highest IL recovery performance of specific energy consumption was about 514.1g/kw·h. Insight gained from this study suggests a potential methodology for IL recovery after the pretreatment process for biomass.