Sulfation Reaction Research Articles

Investigation of BiVO4-based advanced oxidation system for decomposition of organic compounds and production of reactive sulfate species

Growth of population and expansion of industries lead to increasing contamination of environment with various organic pollutants. If not properly cleaned, wastewater contaminates freshwater resources, aquatic environment and has huge negative impact on ecosystems, quality of drinking water and human health, therefore new and effective purification systems are in demand. In this work bismuth vanadate-based advanced oxidation system (AOS) for the decomposition of organic compounds and production of reactive sulfate species (RSS) was investigated. Pure and Mo-doped BiVO4 coatings were synthesized using sol-gel process. Composition and morphology of coatings were characterized using X-ray diffraction and scanning electron microscopy techniques. Optical properties were analyzed using UV–vis spectrometry. Photoelectrochemical performance was studied using linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. It was shown that increase in Mo content affects the morphology of BiVO4 films, reduces charge transfer resistance and enhances the photocurrent in the solutions of sodium borate buffer (with and without glucose) and Na2SO4. Mo-doping of 5–10 at.% leads to 2- to 3-fold increase in photocurrents. Faradaic efficiencies of RSS formation ranged between 70 and 90 % for all samples irrespective of Mo content. All studied coatings demonstrated high stability in long-lasting photoelectrolysis. In addition, effective light-assisted bactericidal performance of the films in deactivation of Gram positive Bacillus sp. bacteria was demonstrated. Advanced oxidation system designed in this work can be applied in sustainable and environmentally friendly water purification systems.

Partial sulfation of gellan gum produces cytocompatible, body temperature-responsive hydrogels

Gellan gum (GG) is a biodegradable polysaccharide and forms thermosensitive hydrogels by a helix-mediated mechanism. Unfortunately, the wide use of GG in tissue engineering has been restricted due to its dramatically higher gelation temperature than normal body temperature. Here, we show that partial sulfation of GG affords a cytocompatible body temperature-responsive hydrogel with an interesting thermoreversibility at 42 °C. The partial sulfation of GG was confirmed by FTIR, EDX and elemental analyses. The sulfated GGs (SGGs) had a higher swelling ratio and degradation in PBS compared to the neat GG. Based on the results of rheometry analysis, the SGG with a degree of sulfation of 0.27 (H3 sample) showed a gelation temperature close to the physiological temperature. In addition, the drop in mechanical properties of SGGs was compensated by a further calcium-mediated ionic crosslinking, where Young's modulus of H3 increased from 10.6 ± 1.9 kPa up to 38.4 ± 5.5 kPa. Finally, we showed that the partial sulfation reaction of GG is a simple and mild strategy to modify chemical structure of GG, and to produce a cytocompatible, body temperature-responsive hydrogel compared to other modifying reactions such as oxidation reaction.

Sulfation of Birch Wood Microcrystalline Cellulose with Sulfamic Acid Using Ion-Exchange Resins as Catalysts

Cellulose sulfates are important biologically active substances with a wide range of useful properties. The development of new methods for the production of cellulose sulfates is an urgent task. In this work, we investigated ion-exchange resins as catalysts for the sulfation of cellulose with sulfamic acid. It has been shown that water-insoluble sulfated reaction products are formed in high yield in the presence of anion exchangers, while water-soluble products are formed in the presence of cation exchangers. The most effective catalyst is Amberlite IR 120. According to gel permeation chromatography, it was shown that the samples sulfated in the presence of the catalysts KU-2-8, Purolit s390 plus, and AN-31 SO42- underwent the greatest degradation. The molecular weight destribution profiles of these samples are noticeably shifted to the left towards low-molecular-weight compounds with an increase in fractions in the regions Mw ~2.100 g/mol and ~3.500 g/mol, indicating the growth of microcrystalline cellulose depolymerization products. The introduction of a sulfate group into the cellulose molecule is confirmed using FTIR spectroscopy by the appearance of absorption bands at 1245-1252 cm-1 and 800-809 cm-1, which correspond to the vibrations of the sulfate group. According to X-ray diffraction data, amorphization of the crystalline structure of cellulose is observed during sulfation. Thermal analysis has shown that with an increase in the content of sulfate groups in cellulose derivatives, thermal stability decreases.

Lead single atoms anchored on reduced graphene oxide as multifunctional additive for lead–carbon battery

The application of lead–carbon batteries (LCBs) in hybrid electric vehicles and large-scale energy storage was limited by gradual sulfation and parasitic hydrogen evolution reaction (HER) of negative plates. Here, Pb single atoms anchored on reduced graphene oxide (PbSAs@rGO) were prepared through electrostatic adsorption and thermal reduction method, and confirmed by two aberration-corrected transmission electron microscopy (TEM and STEM) and synchrotron-based X-ray absorption fine structure spectroscopy (XAFS). By anchoring PbSAs on rGO surfaces where HER is prone to occur, the HER rate was greatly reduced. Moreover, PbSAs could serve as seeds to induce three-dimensional growth of Pb branches, which endows the NAM containing PbSAs@rGO additives with a specific surface areas (SSA) about 2.3 times than that of control one. The increased SSA can help to delay the sulfation of negative plate. Meanwhile, PbSAs can help enhance the affinity of rGO towards negative active material (NAM), which enable electrochemical reduction reaction proceeds at a higher rate. Thanks to the coordination of various functions from multifunctional additives, service life of LCBs under high-rate partial-state-of-charge (HRPSoC) have been extend from 3529 to 16,097 cycles, and from 4692 to 22,606 cycles, in 50% state of charge (SoC) and 75% SoC, respectively.

One-Pot Synthesis of Monofunctionalized Oligoethylene Glycols through Ring-Opening and Heterogeneous Hydrolysis of Macrocyclic Sulfates.

The one-pot nucleophilic ring-opening reaction of oligoethylene glycol macrocyclic sulfates provides an efficient strategy for the monofunctionalization of oligoethylene glycols without protecting or activating group manipulation. In this strategy, the hydrolysis process is generally promoted by sulfuric acid, which is hazardous, difficult to handle, environmentally unfriendly, and unfit for industrial operation. Here, we explored a convenient handling solid acid, Amberlyst-15, as a replacement for sulfuric acid to accomplish the hydrolysis of sulfate salt intermediates. With this method, 18 valuable oligoethylene glycol derivatives were prepared with high efficiency, and gram-scale applicability of this method has been successfully demonstrated to afford a clickable oligoethylene glycol derivative 1b and a valuable building block 1g for F-19 magnetic resonance imaging traceable biomaterial construction.

EFFECT OF PARTICLE SIZE ON SIMULTANEOUS CALCINATION AND SULFATION OF LIMESTONE

The simultaneous calcination and sulfation characteristics of limestone in simulative CFB flue gas atmosphere is examined using a slidable tube furnace system combined with X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) with a focus on the effect of particle size. The effect mechanism of particle size on simultaneous calcination and sulfation of limestone is further analyzed based on the effect of temperature and CO<sub>2</sub> concentration. The qualitative and quantitative results show that calcination reaction dominates in the early simultaneous calcination and sulfation reaction of limestone and the predominant effect transforms from calcination to sulfation reaction in the late simultaneous reaction of limestone. Compared with small particle size limestone, the big particle size limestone slows the weight loss rate and weight gain rate and needs more time to achieve the lowest weight point. This is related to lower mole fraction loss rate of CaCO<sub>3</sub> and mole fraction gain rate of CaSO<sub>4</sub> during simultaneous calcination and sulfation of limestone with big particle size. The effect mechanism of particle size on simultaneous calcination and sulfation of limestone is mainly due to the change of reaction specific surface area, heat transfer, and mass transfer from the surface to the inside of limestone with different particle sizes.

Secondary PM2.5 dominates aerosol pollution in the Yangtze River Delta region: Environmental and health effects of the Clean air Plan

The Clean Air Plan has been active in China since 2013 to mitigate severe PM2.5 pollution. In this study, we applied the air quality model WRF-Chem to simulate PM2.5 in the Yangtze River Delta (YRD) region of China in 2017, with the aim of assessing the air quality improvement and its associated health burden in the final year of the Clean Air Plan. To better describe the fate of various PM2.5 compositions, we updated the chemical mechanisms in the model beforehand, including heterogeneous sulfate reactions, aqueous secondary organic aerosol (SOA) uptake, and volatility basis set (VBS) based SOA production. Both the observation and simulation results agreed that the stringent clear air action effectively reduced the PM2.5 pollution levels by ∼ 30 %. The primary PM2.5 (−6 ∼ − 16 % yr−1) showed a more significant decreasing trend than the secondary PM2.5 (−2 ∼ − 8 % yr−1), which was mainly caused by the directivity of the clear air actions and the worsening ozone pollution in the recent years. The inconsistent decreasing trends of PM2.5 components subsequently led to an increasing proportion of secondary PM2.5. Nitrate particles, higher in the central and western YRD region, have replaced sulfate and have become the largest component of secondary inorganic aerosols year-round, except in summer, when strong ammonium nitrate evaporation occurs. In addition, SOA remains an important component (21 ∼ 22 %) especially in summer, most of which is produced from the oxidation and ageing of semi/intermediate volatile organic compounds (S/IVOC). Furthermore, we quantified the associated health impacts and found that the Clean Air Plan has largely reduced premature mortality due to PM2.5 exposure in the YRD region from 399.1 thousand to 295.7 thousand. Our study highlights the benefits of the Clean Air Plan and suggests that subsequent PM2.5 improvement should be geared more towards controlling secondary pollutants.

Crystal structure of adenosine 5ʹ-phosphosulfate kinase isolated from Archaeoglobus fulgidus

The 3′-phosphoadenosine-5′-phosphosulfate (PAPS) molecule is essential during enzyme-catalyzed sulfation reactions as a sulfate donor and is an intermediate in the reduction of sulfate to sulfite in the sulfur assimilation pathway. PAPS is produced through a two-step reaction involving ATP sulfurylase and adenosine 5′-phosphosulfate (APS) kinase enzymes/domains. However, archaeal APS kinases have not yet been characterized and their mechanism of action remains unclear. Here, we first structurally characterized APS kinase from the hyperthermophilic archaeon Archaeoglobus fulgidus, (AfAPSK). We demonstrated the PAPS production activity of AfAPSK at the optimal growth temperature (83 °C). Furthermore, we determined the two crystal structures of AfAPSK: ADP complex and ATP analog adenylyl-imidodiphosphate (AMP-PNP)/Mg2+/APS complex. Structural and complementary mutational analyses revealed the catalytic and substrate recognition mechanisms of AfAPSK. This study also hints at the molecular basis behind the thermal stability of AfAPSK.

UPLC-QTOF-MS Based Comparison of Rotundic Acid Metabolic Profiles in Normal and NAFLD Rats.

Rotundic acid, the principal bioactive constituent of the herbal remedy "Jiubiying", has been considered as a candidate compound for treating non-alcoholic fatty liver disease (NAFLD). However, the in vivo and in vitro metabolism of rotundic acid has remained unclear. With the aim of elucidating its metabolic profile, a reliable approach that used ultra-high performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) was applied for screening and identifying rotundic acid in vivo (plasma, feces, urine, and liver tissue of normal and NAFLD model rats) and in vitro (rat liver microsomes) metabolites. Herein, 26 metabolites of rotundic acid were identified, including 22 metabolites in normal rats, 20 metabolites in NAFLD model rats, and eight metabolites in rat liver microsomes. Among them, 17 metabolites were identified for the first time. These data illustrate that the pathological status of NAFLD affects the metabolism of rotundic acid. Furthermore, the major pathways of metabolism included phase Ⅰ (demethylation, desaturation, etc.) and phase Ⅱ (sulfation and glucuronidation) reactions, as well as a combined multiple-step metabolism. This work provides important information on the metabolism of rotundic acid and lays the foundation for its future clinical application.

Al-fumarate metal-organic frameworks adsorbent for removal of organic compound and gas storage

Abstract Metal-organic frameworks (MOFs) have attracted a great amount of attention due to their unique properties, including high porosity, large surface area, and flexible frameworks. These special properties are desirable in many applications such as adsorption, catalysis, drug delivery, and gas storage. Herein, Al-fumarate MOFs were synthesised from the reaction of aluminium sulphate with fumaric acid at 65 °C for 1 h. X-ray diffraction (XRD), N2-adsorption, scanning electronic microscope (SEM), thermogravimetric analysis (TGA), and UV–vis spectrometer were used to characterise the physicochemical properties of the prepared adsorbent materials. The obtained results indicated that the Al-fumarate MOFs possess good water stability and can adsorb/remove over 70% of Rose Bengal under UV–light irradiation. Gas adsorption/storage experiments revealed that Al-fumarate MOFs also exhibited high CO2 and CH4 uptakes of ∼59 cm3 g−1 and 17 cm3 g−1 at 303 K and ∼805 Torr (∼1 bar), respectively. The synthesised Al-fumarate MOFs obtained both excellent photocatalytic activity and high gas adsorption/storage that are due to the large surface area (∼1100 m2 g)−1 and high porosity (0.65 cm3 g)−1. Thus, these Al-fumarate MOFs are very promising in the fields of photocatalysis for wastewater treatment and of gas adsorption/storage.

Inhibition and recovery of ANAMMOX with Na2SO3: From performance to microbial community analysis

In this study, three concentrations of Na2SO3 solution were used to remove dissolved oxygen in the influent water and enter the up-flow anaerobic sludge bed reactor (UASB). This study investigated the effects of three concentrations of Na2SO3 on the inhibition and performance recovery of the ANAMMOX system and the structure of the microbial community. The results showed that although Na2SO3 had a deoxidizing function, the ANAMMOX system underwent a sulfate reduction reaction after adding Na2SO3, and the reduction product was mainly H2S, which caused the AnAOB to be inhibited by sulfide. The denitrification performance was less than 1/2 of that under normal conditions. The ANAMMOX system was restored by immediately removing Na2SO3 and reducing nitrogen load. After 11, 20, and 34 days, the performance of the ANAMMOX system returned to normal, but low concentrations(45 mg/L) required a long recovery time. High-throughput sequencing analysis showed that the community of the ANAMMOX system changed significantly. Before and after the experiment, the relative abundance of ANAMMOX functional bacteria Candidatus Brocadia decreased from 32.66% to 21.4%, and Candidatus Kuenenia decreased from 7.3% to 4.06%. However, the relative abundances of Armatimonadetes and Ignavibacteriae increased from below 2% to about 20%. At the same time, Thiobacillus and Desulfuromonadales were observed. This paper explores and summarizes the cause of Na2SO3's inhibition of AnAOB, highlights the recovery of AnAOB after inhibition for the stable operation and deepens the understanding of the environmental conditions regulating the ANAMMOX process.

The introduction of sulfates to suppress Cr(III) oxidation during incineration of tannery sludge and reduce leachability toxicity of incineration residue

Incineration is an alternative approach to disposal of tannery sludge due to the significant volume reduction. But the Cr(III) oxidation caused by Ca hydrates or carbonates in the incineration process could lead to incineration residue exceeding the required standard in the leaching toxicity of Cr(VI) and being listed in hazardous waste. A novel method of suppressing Cr(III) oxidation by introducing sulfates during the incineration of tannery sludge is proposed in this study. Cr(III) oxidation can be effectively inhibited with the introduction of NH2SO3H, NH4HSO4 and NaHSO4 at n(S)/n(Ca) over 1.2. The combination reaction of sulfates and CaO prevents the Cr(III) oxidation. The inhibition of Cr(III) oxidation by sulfates is the most effective at 700–900 °C because almost all Ca is incorporated into CaSO4 phase. NH2SO3H and NH4HSO4 perform better in inhibiting Cr(III) oxidation than NaHSO4. The intermediate product of Cr2(SO4)3, which is formed below 500 °C, would decompose into Cr2O3 with the temperature of over 600 °C. However, part of Cr2O3 is still oxidized into CaCrO4 aroused by CaSO4 at a temperature of over 900 °C. Kinetic study showed Cr(III) oxidation could be effectively suppressed even if the heating time extends to 2 h at 800 °C. Toxicity Characteristic Leaching Procedure showed that the leaching concentrations of Cr(VI) from incineration residues with the introduction of NH2SO3H and NH4HSO4 at n(S)/n(Ca) of over 1.2 satisfied the requirement, and resultant residues could not be classified as hazardous waste. Due to inhibiting Cr(III) oxidation with high efficiency at 700–900 °C, the introduction of sulfates can be considered as a potential approach to prevent Cr(VI) formation during the incineration of tannery sludge by fluidized bed incinerator.

Mechanisms of the Ammonium Sulfate Roasting of Spent Lithium-Ion Batteries.

Ammonium sulfate ((NH4)2SO4) assisted roasting has been proven to be an effective way to convert spent lithium-ion battery cathodes to water-soluble salts. Herein, thermogravimetric (TG) experiments are performed to analyze the mechanism of the sulfation conversion process. First, the reaction activation energies of the sulfate-assisted roasting are 88.87 and 95.27kJ mol-1, which are calculated by Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods, respectively. Then, nucleation and growth are determined and verified as the sulfation reaction model by the Šatava-Šesták method. Finally, sub-reactions of the sulfation process are investigated and reaction controlling mechanisms are determined by the contribution of sub-reaction. Based on the thermogravimetric analysis, the phase boundary reaction is found to dominate in the initial step of the roasting process (α< 0.6) while the nucleation reaction controlls the following step (α> 0.6), agreeing well with changing trend of activation energy. Overall, thermogravimetric analysis is a general way to study the mechanism of the various roasting processes.

Monitoring the Dissolution and Hydrolysis of Pyrosulfate by Electrochemistry at a Liquid‐Liquid Microinterface Array

AbstractDissolution and hydrolysis processes are important in a variety of settings, including industrial and environmental applications. In this work, the hydrolysis of pyrosulfate (disulfate) was investigated by ion‐transfer electrochemistry at an array of microinterfaces between two immiscible electrolyte solutions (μITIES). Current associated with pyrosulfate transfer was observed, but it decreased with time. This is due to the hydrolysis of pyrosulfate to hydrogen sulfate and sulfate. Corroborating data for the hydrolysis was obtained from pH measurements (acidification of the aqueous solution) and Raman spectroscopy (formation of sulfate and hydrogen sulfate). Measurement of the ion‐transfer potential from the voltammograms enabled estimation of pyrosulfate's Gibbs energy of transfer between the phases. Quantum mechanical calculations were employed to estimate the thermodynamics for the reactions of pyrosulfate, hydrogen sulfate and sulfate, which supported the experimentally observed trends. Altogether, these results illustrate the use of electrochemistry at the μITIES to characterise dissolution and hydrolysis processes.

Degradation and fragmentation behavior of polypropylene and polystyrene in water

The polystyrene (PS) retrieved from the beach exhibited no change in surface texture. In contrast to it, the retrieved polypropylene (PP) had a rumpled surface texture. Highly reactive sulfate radical generated by K2S2O8 was employed as degradation initiator of PP and PS, and their degradation behavior was studied in water. The PS carbonyl index value gradually went up down, and its molecular weight (MW) curve discontinuously shifted to a lower MW with the increase of the degradation time unlike the PP. It was found that the PP microplastic production rate was approximately three time higher than the PS from weight ratio dependence on degradation time. The higher microplastic production rate of PP arose from its crystallizability. The voids were produced by change in specific volume occurring by chemi-crystallization and then provoked the cracks leading to quick fragmentation. The SEM photographs suggested that the PP microplastic size facilely reached nm order by the cracking around lamella.

Preparation, chemical structure and α-glucosidase inhibitory activity of sulfated polysaccharide from Grifola frondosa

• Sulfated Grifola frondosa polysaccharide was prepared and characterized. • Sulfation and degradation could exist concurrently during the sulfation reaction. • S-GFP is a noncompetitive inhibitor of α-glucosidase. • S-GFP could significantly quench the endogenous fluorescence of α-glucosidase. Sufalted modification of Grifola frondosa polysaccharide (GFP) was performed using the chlorosulfonic acid-pyridine (CSA-Pyr) method. The chemical structure and α-glucosidase inhibitory activity of sulfated Grifola frondosa polysaccharide (S-GFP) were investigated. FT-IR and NMR spectra both revealed C-6 as the main substituted position owing to steric hindrance. Molecular weight ( Mw ) analysis indicated that sulfation and degradation could exist concurrently during the sulfation reaction given that the Mw of S-GFP was different from that of natural GFP. Inhibition test of α-glucosidase activity implied that S-GFP is a noncompetitive inhibitor of α-glucosidase. S-GFP effectively inhibited the activity of α-glucosidase with an IC 50 value of 3.353 µg mL −1 . The results of inhibitory mechanism indicated that S-GFP quenched the endogenous fluorescence of α-glucosidase and changed the backbone structure of the protein. Circular dichroism (CD) analysis showed that treatment with S-GFP changed the conformation of α-glucosidase, increased the content of the α-helix structure, and destroyed the hydrogen bond system of the enzyme. This experiment aims to elucidate the potential α-glucosidase inhibitory activity of sulfated polysaccharides and to provide new insights into the targets of their bioactivities.

Recovery of lithium from LiAlO2 in waste box sagger through sulfation to produce Li2SO4 and sequential wet conversion to Li3PO4, LiCl and Li2CO3

To supplement the increasing demand for lithium (Li) resources dictated by the growing market for lithium-ion batteries (LIBs), this study aimed to secure lithium carbonate (Li2CO3) using a waste box sagger generated from the process of manufacturing cathode materials for LIBs. Lithium was recovered through sulfation and subsequent wet conversion into high-purity Li2CO3. Lithium extractability (93%) from the waste box sagger powder was determined by the sulfation reaction using 5 M sulfuric acid (H2SO4) and distilled water (H2O) leaching of the resultant. The precipitation efficiency (85%) of Li into lithium phosphate (Li3PO4) in extracted Li solution was established using a sodium hydroxide (NaOH) and phosphoric acid (H3PO4) mixture. The maximum conversion efficiency (99%) of Li3PO4 to lithium chloride (LiCl) solution was calculated using a reflux method with calcium chloride (CaCl2) solution at a solid (g)/liquid (L) ratio of 100. The highest Li+ concentration reached 50,800 mg/L at a solid/liquid ratio of 400 and Cl/Li molar ratio of 0.95 in the range of tested conditions. Finally, high-purity Li2CO3 (99.8% in metal basis) was produced from the obtained Li solution through purification using NaOH, followed by carbonation using sodium carbonate (Na2CO3). The proposed method demonstrates the feasibility of securing a Li resource by recycling waste box sagger instead of disposing them as a designated waste.

Optical in-situ measurements and modeling of post-flame sulfation of NaOH(g) and NaCl(g)

Post-flame sulfation of gaseous sodium hydroxide (NaOH) and sodium chloride (NaCl) was investigated with optical in situ measurements at 850 to 1475 °C. A multi-jet burner was used to generate well-controlled combustion environments. The multi-jet burner also enabled the separate feeding of the sodium species and SO2 to the combustion environment where the sulfation reactions occurred. Concentrations of NaOH(g) and NaCl(g) were measured in the product gas using broadband UV absorption spectroscopy to follow the degree of sulfation. At 1475 and 1275 °C almost no sulfation occurred with an initial NaOH(g) concentration of 20 ppm and SO2 concentrations between 0 and 150 ppm. At 985 °C, the NaOH(g) concentration decreased to less than 5 ppm with SO2 concentrations above 50 ppm and at 850 °C almost all NaOH(g) was sulfated under these conditions. The experimental results for the gas-phase sulfation of NaOH were compared to previous results for the sulfation of KOH under the same conditions and the results were shown to be similar for NaOH and KOH under these conditions. Sulfation of NaOH(g) generally occurred to a more significant extent than the sulfation of NaCl(g). At 1115 to 1475 °C, no sulfation of NaCl(g) was observed. At the lowest investigated temperature, 850 °C, the NaCl(g) concentration decreased from 20 ppm to 12 ppm after the addition of 150 ppm SO2. Chemical equilibrium calculations and kinetic modeling using an updated kinetic model for the detailed Na-Cl-S chemistry were compared to the experimental results. Above 1100 °C, the system can be described by chemical equilibrium, implying that equilibrium is reached in less than 100 ms. At temperatures below 1100 °C, the measured concentration indicated kinetic control. Under these conditions, the kinetic model was in good agreement with the experimental results for NaOH(g) but over-predicted the sulfation of NaCl(g). The combined experimental data, chemical equilibrium calculations and kinetic modeling of the present study support that sulfation of alkali species can occur in the gas phase through homogeneous reactions.

Promoted Sb removal with hydrogen production in microbial electrolysis cell by ZIF-67-derived modified sulfate-reducing bacteria bio-cathode

Bio-cathode Microbial electrolysis cell (MEC) has been widely discovered for heavy metals removal and hydrogen production. However, low electron transfer efficiency and heavy metal toxicity limit MEC treatment efficiency. In this study, ZIF-67 was introduced to modify Sulfate-reducing bacteria (SRB) bio-cathode to enhance the bioreduction of sulfate and Antimony (Sb) with hydrogen production in the MEC. ZIF-67 modified bio-cathode was developed from a bio-anode microbial fuel cell (MFC) by operating with an applied voltage of 0.8 V to reverse the polarity. Cyclic voltammetry, linear sweep voltammetry and electrochemical impedance were done to confirm the performance of the ZIF-67 modified SRB bio-cathode. The synergy reduction of sulfate and Sb was accomplished by sulfide metal precipitation reaction from SRB itself. Maximum sulfate reduction rate approached 93.37 % and Sb removal efficiency could reach 92 %, which relies on the amount of sulfide concentration generated by sulfate reduction reaction, with 0.923 ± 0.04 m3 H2/m3 of hydrogen before adding Sb and 0.857 m3 H2/m3 of hydrogen after adding Sb. The hydrogen was mainly produced in this system and the result of gas chromatography (GC) indicated that 73.27 % of hydrogen was produced. Meanwhile the precipitates were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy to confirm Sb2S3 was generated from Sb (V).

Last piece in the puzzle of bisphenols BPA, BPS and BPF metabolism: Kinetics of the in vitro sulfation reaction.

Bisphenols are endocrine-disrupting chemicals ubiquitously present in the environment, with the consequent exposure to humans. In humans, bisphenols are metabolized to glucuronide and sulfate conjugates. Recent studies indicate that sulfation represents an important bisphenol metabolic pathway for the most vulnerable humans, such as the growing fetus. Our aim was to evaluate sulfation kinetics of commonly detected bisphenols in biological samples: bisphenol A (BPA), bisphenol S (BPS), and bisphenol F (BPF). Furthermore, we evaluated estrogenic agonist potencies and long-term stability of these bisphenol sulfates. BPS and BPF sulfates were prepared by chemical synthesis. Sulfation kinetics of the selected bisphenols were tested in pooled human liver cytosol, as a source for soluble phase II enzymes, including liver sulfotransferases, with quantification by LC-MS/MS. A validated transactivation assay using the hERα-Hela 9903cell line was used to determine estrogenic agonist potencies. Moreover, BPA, BPS, and BPF sulfate stabilities were examined under various conditions and during storage. In vitro sulfation of BPA and BPS followed Michaelis-Menten kinetics; BPF sulfation followed a substrate inhibition model. Sulfation rates were comparable for these bisphenols, although their KM values indicated some large differences in affinities. BPA and BPS sulfates are not hERα agonists. The bisphenol sulfates can be considered stable for at least 2 days under these tested media conditions. These data indicate that bisphenol sulfation is an important route in their biotransformation. Compared to glucuronidation, these bisphenols show slower sulfation rates but similar KM values. BPA and BPS metabolic biotransformation by sulfation provides their detoxification as they are without estrogenic activities.