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In recent years, there has been a marked increase in the production of excess sludge. Chain-elongation (CE) fermentation presents a promising approach for carbon resource recovery from sludge, enabling the transformation of carbon into medium-chain fatty acids (MCFAs). However, the impact of sulfate, commonly presents in sludge, on the CE process remains largely unexplored. In this study, batch tests for CE process of sludge anaerobic fermentation liquid (SAFL) under different SCOD/SO 4 2− ratios were performed. The moderate sulfate reduction under the optimum SCOD/SO 4 2− of 20:1 enhanced the n-caproate production, giving the maximum n-caproate concentration, selectivity and production rate of 5.49 g COD/L, 21.4% and 4.87 g COD/L/d, respectively. The excessive sulfate reduction under SCOD/SO 4 2− ≤ 5 completely inhibited the CE process, resulting in almost no n-caproate generation. The variations in n-caproate production under different conditions of SCOD/SO 4 2− were all well fitted with the modified Gompertz kinetic model. Alcaligenes and Ruminococcaceae_UCG-014 were the dominant genus-level biomarkers under moderate sulfate reduction (SCOD/SO 4 2− = 20), which enhanced the n-caproate production by increasing the generation of acetyl-CoA and the hydrolysis of difficult biodegradable substances in SAFL. The findings presented in this work elucidate a strategy and provide a theoretical framework for the further enhancement of MCFAs production from excess sludge. [Display omitted] • Moderate sulfate reduction enhanced n-caproate production from SAFL in CE. • Excessive sulfate reduction resulted in almost no n-caproate generation. • The kinetics of n-caproate production well fitted the modified Gompertz model. • Moderate sulfate reduction optimized the microbial community composition. • Multiple metabolic pathways were enhanced under moderate sulfate reduction. [ABSTRACT FROM AUTHOR]

During the long-term stabilization process of landfills, the pressure field undergoes constant changes. This study constructed dynamic pressure changes scenarios of high-pressure differentials (0.6 MPa) and low-pressure differentials (0.2 MPa) in the landfill pressure field at 25 °C and 50 °C, and investigated the sulfate reduction behavior in response to landfill dynamic pressure changes. The results showed that the pressurization or depressurization of high-pressure differentials caused more significant differences in sulfate reduction behavior than that of low-pressure differentials. The lowest hydrogen sulfide (H 2 S) release peak concentration under pressurization was only 29.67% of that under initial pressure condition; under depressurization, the highest peak concentration of H 2 S was up to 21,828 mg m−3, posing a serious risk of H 2 S pollution. Microbial community and correlation analysis showed that pressure had a negative impact on the sulfate-reducing bacteria (SRB) community, and the SRB community adjusted its structure to adapt to pressure changes. Specific SRBs were further enriched with pressure changes. Differential H 2 S release behavior under pressure changes in the 25 °C pressure environments were mediated by Desulfofarcimen (ASV343) and Desulfosporosinus (ASV1336), while Candidatus Desulforudis (ASV24) and Desulfohalotomaculum (ASV94) played a key role at 50 °C. This study is helpful in the formulation of control strategies for the source of odor pollution in landfills. [Display omitted] • H 2 S release behavior varies under dynamic pressure change. • DOC consumption differs with pressure dynamic changes at 25 °C and 50 °C. • Pressure dynamic change triggers specific SRB enrichment. • H 2 S release behavior under pressure change is dominated by specific SRB. [ABSTRACT FROM AUTHOR]

Methane-driven hexavalent chromium (Cr(VI)) reduction in a microbial fuel cell (MFC) has attracted much attention. However, whether the presence of sulfate (SO 4 2−) affects the reduction of Cr(VI) is still lacking in systematic studies. This study involved constructing a MFC-granular sludge (MFC-GS) coupling system with dissolved methane (CH 4) was used as the electron donor to investigate the effect of SO 4 2− on Cr(VI) bioreduction, sludge characteristic, and functional metabolic mechanisms. When the SO 4 2− concentration was 10 mg/L, the average removal rate of Cr(VI) in the anaerobic stage decreased to the lowest value (22.25 ± 2.06%). Adding 10 mg/L SO 4 2− obviously inhibited the electrochemical performance of the system. Increasing SO 4 2− concentration weakened the fluorescence peaks of tryptophan and aromatic proteins in the extracellular polymeric substance of sludge. Under the influence of SO 4 2−, Methanothrix_soehngenii decreased from 14.44% to 5.89%. The relative abundance of methane metabolic was down-regulated from 1.47% to 0.98%, while the sulfur metabolic was up-regulated from 0.09% to 0.21% when SO 4 2− was added. These findings provided some reference for the treatment of wastewater containing Cr(VI) and SO 4 2− complex pollutants in the MFC-GS coupling system. • Effect of sulfate on Cr(VI) bioreduction in the MFC-GS system was explored. • Removal rate of Cr(VI) in the MFC-GS system decreased in presence of sulfate. • Sat , aprAB and dsrAB remained up-regulated after increasing SO 4 2− concentration. [ABSTRACT FROM AUTHOR]

Coagulation with inorganic Mg-based coagulants is an efficient technology for dyes removal. However, the promising poly-magnesium-silicate (PMS) coagulant with better aggregation abilities can only be used in a very limited pH range. In this study, poly-magnesium-titanium-silicate (PMTS) was prepared by using titanium sulfate modified PMS. For the treatment of Congo red dye wastewater, PMTS(S), PMTS(Cl) and PMTS(N) synthesized under different acid media (H 2 SO 4 , HCl and HNO 3) were used. PMTSs had the highest coagulation efficiency at Ti/Mg molar ratio of 0.75 and B value of 1.5. PMTSs outperformed PMS in the initial pH range of 5.50–9.00, with a dye removal efficiency of over 90% at 17.1 mg/L. Under optimal conditions, PMTS(S) had higher coagulation efficiency than that of PMTS(Cl) and PMTS(N), and the settling rate of the four Mg-based coagulants followed an order of PMTS(S) > PMS > PMTS(Cl) > PMTS(N). The coagulation mechanisms of PMTSs on Congo red dye were elucidated by further analysis of coagulation precipitates using UV, FT-IR, SEM and EDS. These results showed that the basis mechanism for floc formation was charge neutralization, while the key to floc formation was chemical combination. Based on the SEM and FTIR results, PMTSs could be found to have special shapes and chain structures, such as Si–O–Ti, Si–O–Mg, Ti–O–Ti, Mg–OH and Ti–OH. Combined with the results of zeta potential, the dominant mechanisms of PMTSs were more likely to be adsorption-interparticle bridging and net-sweeping. In a word, this study provided a highly efficient coagulant with a wide range of applicable pH for the control of dye contamination, and shed light on the potential application of PMTS in the removal of dye pollutants. • PMTS is prepared by modifying poly-magnesium-silicate with titanium sulfate. • PMTSs outperform PMS over the initial pH range of 5.50–9.00. • PMTSs coagulation process occur the absorption-bridging and net-sweeping. • PMTS (S) presents highly efficient coagulation performance and has the fastest settling rate. [ABSTRACT FROM AUTHOR]

The rapid increase in urbanization and intensive coal mining activities have accelerated the deterioration of surface water quality. Environmental problems caused by the accumulation of nitrate and sulfate from natural, urban, and agricultural sources have attracted extensive attention. Information on nitrate and sulfate sources and their transformations is crucial for understanding the nitrogen and sulfur cycles in surface water. In this study, we monitored nitrate and sulfate in three representative rivers in mining cities in northern China. The main pollution sources and biogeochemical processes were identified by using stable isotopes (δD, δ18O H2O , δ15N, δ18O NO3 , δ34S and δ18O SO4) and hydrochemistry. The contribution of natural and anthropogenic sources was quantitatively estimated based on a Bayesian mixed model. The results indicated a large variation in sulfate and nitrate sources between the different rivers. Nitrate in the Tuohe River mainly derived from manure/sewage (57.9%) and soil N (26.9%), while sulfate mainly derived from manure/sewage (41.7%) and evaporite dissolution (26.8%). For the Suihe River, nitrate was primarily sourced from chemical fertilizer (37.9%) and soil nitrogen (34.8%), while sulfate was mainly sourced from manure/sewage (33.1%) and chemical fertilizer (21.4%). For the Huihe River, nitrate mainly derived from mine drainage (56.6%) and manure/sewage (30.6%), while sulfate predominantly originated from mine drainage (58.3%) and evaporite dissolution (12.9%). Microbial nitrification was the major pathway for the migration and transformation of nitrate in the surface water. However, denitrification and bacterial sulfate reduction (BSR) did not play a significant role as aerobic conditions prevailed. In this study, we elucidated the sources and transformation mechanisms of nitrate and sulfate. Additionally, we provided a reference for formulating a comprehensive strategy for effective management and remediation of surface water contaminated with nitrate and sulfate in mining cities. [Display omitted] • Natural and anthropogenic sources of nitrates and sulfates were quantified. • Water from the Tuohe, Suihe, and Huihe Rivers and a subsidence zone were studied. • Nitrification was the major pathway for nitrate transformation in surface water. • Multiple sources of pollutants could be identified simultaneously. • Denitrification and bacterial sulfate reduction (BSR) were not observed. [ABSTRACT FROM AUTHOR]

In treating mine-impacted waters using sulfate-reducing bacteria (SRB), metal inhibition and substrate selection are important factors affecting the efficiency of the bioprocess. This work investigated the role of the substrate (i.e. lactate, formate, glycerol and glucose) on Ni inhibition to SRB with sulfate-reducing activity tests at initial pH 5, 7 and 9 and 100 mg/L of Ni. Results indicated that the type of substrate was a significant factor affecting Ni inhibition in SRB, which was the most negligible in the lactate system, followed by glycerol, glucose, and formate. Although less significant, Ni inhibition also varied with the pH, leading for instance, to a reduction of 77% in the sulfate reducing activity for the formate system, but only of 28% for lactate at pH 5. The added substrate also influenced the precipitation kinetics and the characteristics of the precipitates, reaching Ni precipitation extents above 95%, except for glucose (83.2%). [Display omitted] • Different digestion pathways of substrates strongly affected Ni inhibition to SRB. • Ni inhibition to SRB was enhanced by lower pH. • Ni supplement enhanced the activity of non-SRB in lactate and formate systems. • The first-order kinetic model was able to describe the Ni precipitation rate. [ABSTRACT FROM AUTHOR]

The large amount of trace organic contaminants (TrOCs) in wastewater has caused serious impacts on human health. In the past few years, Sulfate radical (SO 4 •-) based advanced oxidation processes (SR-AOPs) are widely recognized for their high removal rates of recalcitrant TrOCs from water. Peroxymonosulfate (PMS) and persulfate (PS) are stable and non-toxic strong oxidizing oxidants and can act as excellent SO 4 •- precursors. Compared with hydroxyl radicals(·OH)-based methods , SR-AOPs have a series of advantages, such as long half-life and wide pH range, the oxidation capacity of SO 4 •- approaches or even exceeds that of ·OH under suitable conditions. In this review, we present the progress of activating PS/PMS to remove TrOCs by different methods. These methods include activation by transition metal, ultrasound, UV, etc. Possible activation mechanisms and influencing factors such as pH during the activation are discussed. Finally, future activation studies of PS/PMS are summarized and prospected. This review summarizes previous experiences and presents the current status of SR-AOPs application for TrOCs removal. Misconceptions in research are avoided and a research basis for the removal of TrOCs is provided. • Different methods of PS/PMS activation for the removal of TrOCs are reviewed. • Short summary of free radical generation mechanisms. • The influence of different factors on the SR-AOPs process is presented. • SO 4 •- is the main reactive radical in SR-AOPs. [ABSTRACT FROM AUTHOR]

Solvent extraction separation of molybdenum (Mo) from the sulphate mediated leach solution bearing Aluminium (Al) and Nickel (Ni) was carried out using N-Methyl-N, N, N-tri-octyl-ammonium chloride. Extensive investigation for extraction study molybdenum in the function of time, Eq.pH, extractant concentration, diluents, temperature, strip solution concentration and phase ratio(A:O) for both extraction and stripping was examined to attain a suitable condition on its selective and enriched extraction. As per the equilibrium study and increasing trend of Eq. pH (pH e) at the correspondence initial pH, it was apparent about association of 1 mol of H+ ion during extraction which with was further supported on extraction of Mo as HMO 4 - at the pH e of 3.48. The association of 1 mol of exrractant during the extraction of Mo was also well evident from the slope analysis study. This indicates about anion exchange phenomenon due to Cl− ion of the N-Methyl-N, N, N-tri-octyl-ammonium chloride (extractant) with HMo 4 − from aqueous phase during complex formation reaction. The FTIR of the organic sample before and after extraction further confirms in support of the complex formation of the molybdenum with the extractant during extraction. The extraction isotherm was constructed at optmum extraction condition: pH e of 3.48 with 0.08M N-Methyl-N, N, N-tri-octyl-ammonium chloride predicts on need of 2-counter current stages for quantitative extraction of Mo at A:O = 3:1. To investigate the regeneration behaviour of adopted extractant along with enriched stripping of molybdenum, ammoniacal reagents were used in stripping study. The stripping of Mo showed promising and efficient using the mixture of the ammoniacal reagents (NH 4 OH + NH 4 Cl) over the either of the solo reagents. The stripping Mc-Cabe Thiele diagram was plotted using 2M NH 4 OH + NH 4 Cl ensures on quantitative stripping of Mo at SO: SS = 2:1 at 2 no. of stages. Both extraction and stripping isotherm results are validated at predicted isotherm conditions by 6-cycles counter current simulation (CCS) study leading to obtain 6-fold enrichment of Mo in stripped solution phase. The subsequent enriched content of Mo (∼60 g/L) in stripped solution phase was precipitated out followed by calcinations 400 °C to obtain a high pure MoO 3. The recovered calcined product as MoO 3 resulted through the proposed processing approach was as ascertained from XRD analysis. [Display omitted] • Trioctylmethylammoniumchloride(TOMAC) exhibits high selectivity to Molybdenum ion. • TOMAC is reusable with high regeneration ability & efficient on extraction Mo. • Proposed liquid-liquid extraction is promising & cost effective on recycling of Mo. [ABSTRACT FROM AUTHOR]

Ultrasonication has been mechanically applied widely in the recycling of spent lithium-ion (SLI) batteries while its influence on chemical pathways has barely been reported. In this study, ultrasonication and sulfate radicals were used in a coupling system to obtain efficient recoveries of Co and Li from SLI batteries. The synergistic effect of ultrasonication and sulfate radicals on recycling was quantitatively analysed by significance analysis and surface responses in a central composite design. The employment of persulfate significantly affected the whole recycling process during the sonication. Factors including acoustic time, operating powers, and temperature all had a significant effect on the recoveries of Co and Li. The maximum recovery efficiencies of Co and Li of 97.33% and 99.25%, respectively, and the minimum loss rate of Al of 4.13% were simultaneously obtained by the fitting predictor. The optimal combination of factors for the sonication system included an acoustic time (min) of 5.5, an operating power (W) of 168, a temperature (°C) of 86, and a ratio of cathode foil to S-solution (mg/mL) of 1:60. A moiety of cathode active material was directly separated from the aluminium collector by sulfate radical-related reactions. Co and Li cations dissolved from LiCoO 2 by carbon dioxide radicals were reprecipitated by excess oxalate. The research demonstrated the positively synergistic influence caused by ultrasonication and sulfate radicals on achieving efficient recoveries of Co and Li from SLI batteries, explicitly expanding the technical choices for the recycling procedure. [Display omitted] • Sonication and sulfate radicals were employed to recover Co and Li from SLI batteries. • The separation and purification of CAMs from SLI were simplified synergistically. • Sulfate radical-related reactions facilitated CAM separation from the Al collector. • Ratios and concentration of PS significantly affected the recycling process of CAMs. • The loss of Al collector was effectively controlled in the hydrometallurgical process. [ABSTRACT FROM AUTHOR]

Microalgae are known as renewable, potential, and sustainable feedstocks for biofuel production. The present work investigated the efficient valorization of green microalgae Chlorella sp. to produce sugars and 5-hydroxymethylfurfural (5-HMF) using thermochemical conversion with a metal-salt (ferric sulfate) as catalyst using a statistical approach and two-step conversion. A statistical approach with a Box–Behnken design was introduced to optimize the conversion for producing sugars. As a result of optimization, 86.46% sugar yield (68.32% glucose yield) was achieved under the condition of 5% biomass and 0.6 g-catalyst/g-biomass at 155 °C and 40 min. Two-step thermochemical conversion was introduced to produce 5-HMF from microalgae. In the first step, sugars were produced from the above optimum condition; in the second step, sugar hydrolysates were converted into 5-HMF by thermochemical conversion without an additional catalyst. In two-step conversion, the maximum 5-HMF yield (37.23%) was achieved at 170 °C and 60 min from the sugar hydrolysate of microalgae obtained from the first-step thermochemical conversion with ferric sulfate. In conclusion, the microalgae as biomass and ferric sulfate as catalyst have availability and the potential to produce biosugars and platform chemicals. • Efficient valorization of C hlorella sp. to sugars and 5-HMF using thermochemical conversion with ferric sulfate. • 86.46% sugar (68.32% glucose) yields were under 5% biomass and 0.6 g-catalyst/g-biomass at 155 °C and 40 min. • In two-step conversion, the maximum 5-HMF yield (37.23%) was achieved at 170 °C and 60 min from the sugar hydrolysate. • Microalgae and ferric sulfate have availability and the potential to produce biosugars and platform chemicals. [ABSTRACT FROM AUTHOR]

Urban subsurface environments are often different from undisturbed subsurface environments due to the impacts of human activities. For example, deterioration of underground infrastructure can introduce elevated levels of Ca, Fe, and heavy metals into subsurface soils and groundwater. Likewise, leakage from sewer systems can lead to contamination by organic C, N, S, and P. However, the impact of these organic and inorganic compounds on biogeochemical processes including microbial redox reactions, mineral transformations, and microbial community transitions in urban subsurface environments is poorly understood. Here we conducted a microcosm experiment with soil samples from an urban construction site to investigate the possible biotic and abiotic processes impacted when sulfate and acetate or lactate were introduced into an urban subsurface environment. In the top-layer soil (0–0.3 m) microcosms, which were highly alkaline (pH > 10), the major impact was on abiotic processes such as secondary mineral precipitation. In the mid-layer (2–3 m) soil microcosms, the rate of Fe(III)-reduction and the amount of Fe(II) produced were greatly impacted by the specific organic acid added, and sulfate-reduction was not observed until after Fe(III)-reduction was complete. Near the end of the incubation, some genera related to syntrophic acetate oxidation and methanogenesis were observed in the lactate-amended microcosms. In the bottom-layer (7–8 m) soil microcosms, the rate of Fe(III)-reduction and the amount of Fe(II) produced were affected by the concentration of amended sulfate. Sulfate-reduction was concurrent with Fe(III)-reduction, suggesting that Fe(II) production was likely due to abiotic reduction of Fe(III) by sulfide produced by microbial sulfate reduction. The slightly acidic initial pH (~5.8) of the mid-soil system was a major factor controlling sequential microbial Fe(III) and sulfate reduction versus parallel Fe(III) and sulfate reduction in the bottom soil system, which had a neutral initial pH (~7.2). 16S rRNA gene-based community analysis revealed a variety of indigenous microbial groups including alkaliphiles, dissimilatory iron and sulfate reducers, syntrophes, and methanogens tightly coupled with, and impacted by, these complex abiotic and biogeochemical processes occurring in urban subsurface environments. [Display omitted] • Batch microcosm study was conducted to mimic C, Fe, and S biogeochemistry in urban subsurface environments. • Soil with concrete debris showed calcium sulfate precipitation when sulfate was introduced and abundance of Hydrogenophaga. • Organic acid and sulfate led to development of distinct communities - IRB, SRB, syntrophic acetate oxidizers, methanogens. • pH was the key factor controlling the sequence of iron reduction and sulfate reduction. [ABSTRACT FROM AUTHOR]

Pulsed light (PL) technology, which is based on photonic technology involves the application of broadband emission of light with short and high-power pulses is beginning to emerge for the treatment of wastes via advanced oxidation processes (AOP). The present work investigates the efficiency of PL as a light source for persulfate (PS) activation (PL/PS) and 4-chlorophenol)4-CP) degradation, an organic model pollutant. The influencing parameters on 4-CP degradation such as solution pH, reaction time, initial concentration of 4-CP, PS dose, pulse intensity and frequency, and distance from PL source are systematically investigated. With increasing pH from 3 to 9, the 4-CP degradation decreased from 49.79 ± 2.49 to 33.12 ± 1.66%. The 4-CP degradation followed the first order kinetics that was improved with increasing reaction time, PS dose, pulse intensity, frequency of pulse, and decreasing pH, initial 4-CP concentration and distance from the PL source. The presence of sulfate, chloride, and carbonate anions in the solution has the inhibitory effects on 4-CP degradation, while nitrate anion improved the performance of PL/PS system. In addition, presence of humic acid had an inhibitory effect on the PL/PS system, which led to a decrease of reaction rate constant and 4-CP degradation was performed in PL/PS system with OH , SO 4 − , O 2 - and 1 O2 radicals. The contributions of OH and SO 4 − radicals were 46% and 51%, respectively for the 4-CP degradation and synergistic effect of PL/PS system showed a significant influence on 4-CP degradation while using a combination of PL and PS, suggesting that PL is an effective activator of PS. • The 4-CP degradation by combined pulsed light and sulfate radicals methods was investigated. • The contributions of OH and SO 4 − radicals were 46% and 51% for the 4-CP degradation. • The presence of SO 4 2− , Cl − , and CO 3 2 − anions led to a decrease in reaction rate constant. [Display omitted] [ABSTRACT FROM AUTHOR]