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Constructed wetlands (CWs) are a promising approach for treating acid mine drainage (AMD). However, the extreme acidity and high loads of heavy metals in AMD can easily lead to the collapse of CWs without proper pre-treatment. Therefore, it is considered essential to maintain efficient and stable performance for AMD treatment in CWs. In this study, pre-prepared attapulgite-soda residue (ASR) composites were used to improve the substrate of CWs. Compared with CWs filled with gravel (CWs-G), the removal efficiencies of sulfate and Fe, Mn, Cu, Zn Cd and Pb in CWs filled with ASR composites (CWs-ASR) were increased by 30% and 10–70%, respectively. These metals were mainly retained in the substrate in stable forms, such as carbonate-, Fe/Mn (oxide)hydroxide-, and sulfide-bound forms. Additionally, higher levels of photosynthetic pigments and antioxidant enzyme activities in plants, along with a richer microbial community, were observed in CWs-ASR than in CWs-G. The application of ASR composites alleviated the adverse effects of AMD stresses on wetland plants and microorganisms. In return, the increased bacteria abundance, particularly SRB genera (e.g., Thermodesulfovibrionia and Desulfobacca), promoted the formation of metal sulfides, enabling the saturated ASR adsorbed with metals to regenerate and continuously capture heavy metals. The synergistic adsorption of ASR composites and microbial sulfate reduction maintained the stable and efficient operation of CWs. This study contributes to the resource utilization of industrial alkaline by-products and promotes the breakthrough of new techniques for low-cost and passive treatment systems such as CWs. [Display omitted] • ASR composites were used to improve the substrate of constructed wetlands (CWs). • Application of ASR composites enhanced the removal of sulfate and metals in CWs. • ASR composites alleviated the AMD stresses on plants and microorganisms. • ASR composites increased the relative abundance of SRB genera in CWs. • Synergistic adsorption by ASR composites and microbial sulfate reduction controls successful operation of CWs. [ABSTRACT FROM AUTHOR]

Mercury (Hg) pollution poses a significant environmental challenge. One promising method for its removal is the sorption of mercuric ions using biochar. FeS-doped biochar (FBC) exhibits effective mercury adsorption, however may release excess iron into the surrounding water. To address this issue, a novel magnetic pyrrhotite/magnetite-doped biochar with a core-shell structure was synthesized for the adsorption of 2-valent mercury (Hg(II)). The proposed synthesis process involved the use of algae powder and ferric sulfate in a one-step method. By varying the ratio of ferric sulfate and alga powder (within the range of 0.18 - 2.5) had a notable impact on the composition of FBC. As the ferric sulfate content increased, the FBC exhibited a higher concentration of oxygen-containing groups. To assess the adsorption capacity, Langmuir and Freundlich adsorption models were applied to the experimental data. The most effective adsorption was achieved with FBC-4, reaching a maximum capacity (Q m) of 95.51 mg/g. In particular, at low Hg(II) concentrations, FBC-5 demonstrated the ability to reduce Hg(II) concentrations to less than 0.05 mg/L within 30 min. Additionally, the stability of FBC was confirmed within the pH range of 3.8 - 7.2. The study also introduced a model to analyze the adsorption preference for different Hg(II) species. Calomel was identified in the mercury saturated FBC, whereas the core-shell structure exhibited excellent conductivity, which most likely contributed to the minimal release of iron. In summary, this research presents a novel and promising method for synthesizing core-shell structured biochar and provides a novel approach to explore the adsorption contribution of different metal species. [Display omitted] • Pyrrhotite/magnetite and biochar formed core-shell structure in FBC. • High sorption effective at low Hg(II) concentration by FBC-5. • Sorption preference of different Hg(II) species investigated by a new model. • FBCs have almost no iron release within pH range of 3.8-7.2. • FBCs can adsorb multiple heavy metals. [ABSTRACT FROM AUTHOR]

Co-contaminants and complex subsurface conditions pose great challenges to site remediation. This study demonstrates the potential of electrokinetic bioremediation (EK-BIO) in treating co-contaminants of chlorinated solvents and heavy metals in low-permeability soils with elevated sulfate. EK-BIO columns were filled with field soils, and were fed by the electrolyte containing 20 mg/L trichloroethylene (TCE), 250 μM Cr(VI), 25 μM As(III), 10 mM lactate, and 10 mM sulfate. A dechlorinating consortium containing Dehalococcoides (Dhc) was injected several times during a 199-d treatment at ∼1 V/cm. Sulfate reduction, Cr/As immobilization, and complete TCE biodechlorination were observed sequentially. EK-BIO facilitated the delivery of lactate, Cr(VI)/As(III), and sulfate to the soils, creating favorable reductive conditions for contaminant removal. Supplementary batch experiments and metagenomic/transcriptomic analysis suggested that sulfate promoted the reductive immobilization of Cr(VI) by generating sulfide species, which subsequently enhanced TCE biodechlorination by alleviating Cr(VI) toxicity. The dechlorinating community displayed a high As(III) tolerance. Metagenomic binning analysis revealed the dechlorinating activity of Dhc and the potential synergistic effects from other bacteria in mitigating heavy metal toxicity. This study justified the feasibility of EK-BIO for co-contaminant treatment and provided mechanistic insights into EK-BIO treatment. [Display omitted] • Feasibility of EK-BIO in treating TCE-Cr/As-contaminated soils was justified. • EK-BIO constructed suitable conditions for removing aqueous Cr/As and TCE. • Sulfate enhanced Cr immobilization and subsequent TCE biodechlorination. • Aqueous Cr(VI) inhibited sulfate reduction and TCE biodechlorination. • Dhc was the essential OHRB with dechlorinating activity. [ABSTRACT FROM AUTHOR]

Electrochemical methods can help manage sulfide in wastewater, which poses environmental and health concerns due to its toxicity, malodor, and corrosiveness. In addition, sulfur could be recovered as fertilizer and commodity chemicals from sulfide-containing wastewaters. Wastewater characteristics vary widely among wastewaters; however, it remains unclear how these characteristics affect electrochemical sulfate production. In this study, we evaluated how four characteristics of influent wastewaters (electrolyte pH, composition, sulfide concentration, and buffer strength) affect sulfide removal (sulfide removal rate, sulfide removal efficiency) and sulfate production metrics (sulfate production rate, sulfate production selectivity). We identified that electrolyte pH (3 × difference, i.e., 25.1 to 84.9 μM h−1 in average removal rate within the studied pH range) and sulfide concentration (16 × difference, i.e., 82.1 to 1347.2 μM h−1 in average removal rate) were the most influential factors for electrochemical sulfide removal. Sulfate production was most sensitive to buffer strength (6 × difference, i.e., 4.4 to 27.4 μM h−1 in average production rate) and insensitive to electrolyte composition. Together, these results provide recommendations for the design of wastewater treatment trains and the feasibility of applying electrochemical methods to varying sulfide-containing wastewaters. In addition, we investigated a simultaneous multi-nutrient (sulfur and nitrogen) process that leverages electrochemical stripping to further enhance the versatility and compatibility of electrochemical nutrient recovery. [Display omitted] • Electrochemical sulfide removal is robust to varying wastewater compositions. • pH and sulfide concentration affected electrochemical sulfide removal most. • pH values between pKa of sulfide and bicarbonate could improve sulfate production. • Buffer strength and pH were most influential to electrochemical sulfate production. • Sulfate production and nitrogen recovery were integrated in electrochemical stripping. [ABSTRACT FROM AUTHOR]

The transportation of dissolved sulfate (SO 4 2-) to the ocean via river systems plays a critical role in the global sulfur cycle. However, the increasing anthropogenic input has made it challenging to quantify the various pristine contributions accurately. The riverine sulfur and oxygen isotopes of sulfates (δ 34S SO4 and δ 18O SO4) and the advantages of the Markov-Chain Monte Carlo model were used to distinguish the anthropogenic input in Fenhe River, a tributary of the Yellow River. The SO 4 2- concentrations and δ 34S SO4 and δ 18O SO4 values of the mainstream river were normally distributed with minor seasonal variations (P > 0.05). However, the upstream riverine SO 4 2- concentrations were significantly altered by the water diversion from the Yellow River. The midstream and downstream sections exhibited a continuous increase in the riverine SO 4 2- concentration and δ 34S SO4 and δ 18O SO4 values during both seasons. The coal mining drainage significantly impacted the tributaries near coal mining activities, and chemical fertilizers and sewage contributed more sulfate in the midstream and downstream sections. The yearly sulfate flux of the Fenhe River accounted for 4.2% of that of Yellow River, among which over 60% was from anthropogenic sources. The average δ 34S SO4 and δ 18O SO4 values had elevated to 11.0‰ and 6.0‰, respectively, due to the extensive input of anthropogenic sulfate. Our findings confirm the utility of δ 34S SO4 and δ 18O SO4 for tracing anthropogenic input and underscore its impacts on river systems and the global sulfur cycle. [Display omitted] • SO 4 2- in the upstream of Fenhe River was significantly altered by water diversion. • Sewage and chemical fertilizer impact mainly occurred in midstream and downstream. • Over 60% of sulfate in the Fenhe River was originated from anthropogenic sources. • Fenhe River contributes 4.2% of annual SO 4 2- flux to the Yellow River. • Sulfur and oxygen isotopes of sulfate are useful for tracing anthropogenic input. [ABSTRACT FROM AUTHOR]

Sulfate radical-based advanced oxidation processes (AOPs) combined biological system was a promising technology for treating antibiotic wastewater. However, how pretreatment influence antibiotic resistance genes (ARGs) propagation remains largely elusive, especially the produced by-products (antibiotic residues and sulfate) are often ignored. Herein, we investigated the effects of zero valent iron/persulfate pretreatment on ARGs in bioreactors treating sulfadiazine wastewater. Results showed absolute and relative abundance of ARGs reduced by 59.8%− 81.9% and 9.1%− 52.9% after pretreatments. The effect of 90-min pretreatment was better than that of the 30-min. The ARGs reduction was due to decreased antibiotic residues and stimulated sulfate assimilation. Reduced antibiotic residues was a major factor in ARGs attenuation, which could suppress oxidative stress, inhibit mobile genetic elements emergence and resistant strains proliferation. The presence of sulfate in influent supplemented microbial sulfur sources and facilitated the in-situ synthesis of antioxidant cysteine through sulfate assimilation, which drove ARGs attenuation by alleviating oxidative stress. This is the first detailed analysis about the regulatory mechanism of how sulfate radical-based AOPs mediate in ARGs attenuation, which is expected to provide theoretical basis for solving concerns about by-products and developing practical methods to hinder ARGs propagation. [Display omitted] • ZVI/PDS pretreatment alleviated occurrence ricks of ARGs during anaerobic treatment. • The mechanisms of ARGs attenuation in combined system were revealed firstly. • In-situ biosynthesized cysteine regulated oxidative stress, further restrained HGT. • Reduced antibiotic residues weakened oxidative stress, inhibited HGT emergence and ARB enrichment. [ABSTRACT FROM AUTHOR]

• OsSultr1;1 complements yeast mutant, YSD1, and enhances arsenic tolerance. • Overexpression of OsSultr1;1 in A. thaliana improves growth under limiting Sulphur. • Transgenic A. thaliana plants show tolerance towards arsenic and abiotic stresses. • Transgenic lines possess enhanced antioxidant activity compared to wild type plants. In this study, the role of a rice high-affinity sulphate transporter, OsSultr1;1 , in maintaining sulphur demand under arsenic (As) stress has been investigated. Saccharomyces cerevisiae mutant, YSD1, deficient in sulphur transport and Arabidopsis thaliana plants expressing OsSultr1;1 , were used to analyze different parameters. Complementation of YSD1 using OsSultr1;1 showed tolerance towards heavy metals. Transgenic Arabidopsis lines expressing OsSultr1;1 developed a significant tolerance towards different abiotic stresses including heavy metals under sulphur limiting conditions. Transgenic lines showed 75–76% and 60-68% reduction in root length compared to 82% and 76% in wild type plants under arsenite [As(III); 10 μM] and arsenate [As(V); 100 μM] stress respectively. The analysis of superoxide radicals and hydrogen peroxide indicated reduced oxidative burst in transgenic as compared to wild type plants under As stress. Real-time PCR analysis showed differential expression of the genes associated with sulphur metabolism in the transgenic lines. A significant decrease (up to 50%) in malondialdehyde (MDA) levels and increased glutathione (GSH) content in transgenic lines demonstrated better detoxification mechanism compared to wild type plants under As stress. We conclude that over-expression of high-affinity sulphate transporters may provide tolerance towards different abiotic stresses under limiting sulphur environment. [ABSTRACT FROM AUTHOR]

• The transformation of iodide by Fe(II)/PDS is a two-step process. • The step of transforming I− to HOI in Fe(II)/PDS is mainly driven by SO 4 •-. • The step of transforming HOI to IO 3 − in Fe(II)/PDS is mainly driven by Fe(IV). • NOM leads to the transformation of I− to Iodinated organic compounds in Fe(II)/PDS. This work investigates the transformation of iodide (I−) by Fe(II)-activated peroxydisulfate (PDS). The transformation of I− into iodate (IO 3 −) is a two-step process, involving reactive iodine species, such as hypoiodous acid (HOI), as a key intermediate, and IO 3 − as the final product. In the first step, SO 4 •- produced by Fe(II)-activated PDS is mainly responsible for the transformation of I− into HOI. In the second step, Fe(IV) formed by the reaction of Fe(III) with PDS is required, to facilitate the further oxidation of HOI to IO 3 −. The disproportionation of HOI and the oxidation by PDS alone contribute negligibly to IO 3 − formation. The IO 3 − yield increases to a maximum, before decreasing gradually, with increased PDS and Fe(II) dosages. The transformation of I− into IO 3 − is favored by lower pH and higher temperature, due to the greater SO 4 •- production by the reaction of Fe(II) with PDS under these conditions. Humic acid, as a representative natural organic matter, scavenges the formed HOI to form iodinated disinfection byproducts, which largely inhibit the transformation of I− into IO 3 −. In addition, the transformation of I− into IO 3 − and iodinated disinfection byproducts by Fe(II) activated PDS was confirmed in the natural waters. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • UV/PS AOP showed the highest tyrosol degradation and mineralization efficiencies. • Degradation of tyrosol followed pseudo-first-order kinetics in all conditions. • Degradation kinetics were enhanced in acidic medium. • Cl−, SO 4 2− and NO 3 − and phosphate buffer did not affect tyrosol removal efficiency. • Maximum TOC reduction of ∼35% was obtained by UV/PS at 640 mJ/cm2. Abstract The photochemical degradation and mineralization of tyrosol (TSL), a model phenolic compound present in olive mill wastewater, were studied by UV-254 nm irradiated peroxymonosulfate (PMS), hydrogen peroxide (H 2 O 2) and persulfate (PS). Effects of initial TSL concentration, UV fluence, pH, phosphate buffer and presence of inorganic anions (i.e., Cl−, SO 4 2− and NO 3 −) were also investigated. Sulfate and hydroxyl radicals were demonstrated to be responsible for TSL degradation and mineralization. Regardless of the treatment conditions, pseudo-first-order kinetics could be obtained, with the efficiencies following UV/PS > UV/H 2 O 2 > UV/PMS. The better removal of TSL by UV/PS correlated with the quantum yield and concentration of sulfate radical in the system. Albeit acidic condition slightly enhanced the performance of the AOPs, complete oxidation of TSL was achieved at pH 6.8 by both UV/PS and UV/H 2 O 2. Though, inorganic anions or different concentrations of phosphate buffer did not affect TSL degradation kinetics, presence of inorganic ions decreased significantly the TOC removal for both UV/PMS and UV/H 2 O 2 processes. Meanwhile, UV/PS process was the least influenced by inorganic ions and showed the highest TOC removal of ∼35%. Overall, UV/PS process was the most effective for TSL degradation and mineralization in the presence or absence of common water constituents. [ABSTRACT FROM AUTHOR]

Highlights • In-situ Cu(II) doped in framework of mesoporous MnO 2 , Cu-MnO 2 was prepared. • Cu-MnO 2 had good catalytic activity and stability for phenol degradation by PMS. • Exposed surface oxygen defect was responsible to the enhancement of PMS activation. Abstract Cu(II) doped mesoporous MnO 2 (Cu-MnO 2) was prepared to establish an intimate functional link between the structure substitution and catalytic peroxymonosulfate (PMS) activation. Based on the characterization of powder X-ray diffraction (XRD), N 2 adsorption-desorption measurement, scanning electron microscope (FE-SEM) and transmission electron microscope (TEM), Cu-MnO 2 had a typical long range ordered mesoporous structure and Cu was successfully introduced in octahedral framework. It exhibited excellent catalytic activity and stability for the phenol degradation by PMS. Phenol was always efficiently degraded over Cu-MnO 2 at a pH range of 3.5–9.0. For example, the reaction rate constant at pH 7.0 was 0.073 min−1, which was two times higher than that of MnO 2 (0.039 min−1). Importantly, 1O 2 was identified as the primary reactive species in Cu-MnO 2 /PMS system. X-ray photoelectron spectroscopy (XPS) confirmed that more exposed surface oxygen defects due to Cu doping were responsible to the enhancement of PMS activation for phenol degradation. The results of PMS decomposition and oxygen evolution indicated that surface oxygen defects lower the reaction energy barrier of PMS decomposition by generating 1O 2 via the energy trapping by oxygen. Finally, the heterogeneous PMS activation mechanism over Cu-MnO 2 was proposed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Investigation of sulfate radical generating oxidants with TiO 2 photocatalysis. • HSO 5 − coupled with UVA/TiO 2 was the most energy efficient system. • Addition of oxidants prolonged the life-time of the formed radicals. • New intermediates based on consecutive hydroxyl substitutions of MC-LR were detected. • Toxicity studies on the treated samples indicated loss of MC-LR toxic properties. Abstract This study investigated the coupling of sulfate radical generating oxidants, (persulfate, PS and peroxymonosulfate, PMS) with TiO 2 photocatalysis for the degradation of microcystin-LR (MC-LR). Treatment efficiency was evaluated by estimating the electrical energy per order (E EO). Oxidant addition at 4 mg/L reduced the energy requirements of the treatment by 60% and 12% for PMS and PS, respectively compared with conventional photocatalysis. Quenching studies indicated that both sulfate and hydroxyl radicals contributed towards the degradation of MC-LR for both oxidants, while Electron Paramagnetic Resonance (EPR) studies confirmed that the oxidants prolonged that lifetime of both radicals (concentration maxima shifted from 10 to 20 min), allowing for bulk diffusion and enhancing cyanotoxin removal. Structural identification of transformation products (TPs) formed during all treatments, indicated that early stage degradation of MC-LR occurred mainly on the aromatic ring and conjugated carbon double bonds of the ADDA amino acid. In addition, simultaneous hydroxyl substitution of the aromatic ring and the conjugated double carbon bonds of ADDA (m/z = 1027.5) are reported for the first time. Oxidant addition also increased the rates of formation/degradation of TPs and affected the overall toxicity of the treated samples. The detoxification and degradation order of the treatments was UVA/TiO 2 /PMS > UVA/TiO 2 /PS>> UVA/TiO 2. [ABSTRACT FROM AUTHOR]

Highlights • Reduced graphene oxide-activated oxidation to degrade BPA. • Higher performance with activated PS than with activated PMS. • SO 4 − rather than HO was the main ROS. • Negative effect of real wastewater matrix on BPA removal. • Poor performance after catalyst reuse. Abstract In the present study, novel metal-free activation of persulfate (PS) and peroxymonosulfate with reduced graphene oxide (rGO) was investigated to degrade Bisphenol A (BPA), one of the most important endocrine disrupting compounds, from different aqueous matrices, namely distilled water (DW) and municipal wastewater treatment plant effluent (TWW). The home-made rGO was characterize and the effect of oxidant (PS and PMS) and catalyst (rGO) concentrations on BPA degradation rates in DW and TWW samples was examined. Complete BPA degradation occurred in DW and TWW with the PS/rGO treatment system after 10 min and 30 min, respectively, whereas 94% (DW) and 83% (TWW) BPA removals were obtained with PMS/rGO for the same treatment period (BPA = 2 mg/L; rGO = 0.02 g/L; PS = 0.25 mM; PMS = 0.5 mM). The radical quenching experiments demonstrated that the SO 4 − predominated in the activation of PS and PMS with rGO for BPA removal, however, HO contributed to the catalytic oxidation process but to a lower extend. The reusability test results, where the catalyst was deactivated seriously just after second cycle, highlighted the need for further studies to enhance the stability of rGO. This study represented an environmentally benign and efficient oxidative treatment of BPA along with insights into the rGO activated PS or PMS processes. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • PMS enhances the removal efficiency of slow-ozone reacting compounds. • PMS reduces the impact of OH scavenging on micropollutant removal. • SO 4 − contribute for more than 50% to the overall removal of most compounds. • O 3 /PMS is up to 3x more efficient than O 3 /H 2 O 2 in the presence of a OH scavenger. • Low PMS doses have still a large positive effect on micropollutant removal. Abstract Given the need for innovations in advanced oxidation processes to deal with challenges such as OH scavenging, this paper addresses the removal of pharmaceuticals with a large variety in ozone reactivity (k O3 = 0.15–3 × 105 M−1s−1) by use of the novel ozone-activated peroxymonosulfate (O 3 /PMS) process. A clear improvement in removal efficiency (up to 5 times higher) is noticed as a result of the generation of SO 4 - radicals, mainly for slow-ozone reacting compounds (k O3 ≤ 250 M−1s−1) and in the presence of a OH scavenger. Depending on the target compound, SO 4 - are assessed to contribute for 50–90% to the overall removal of the micropollutants, both in single-compound and mixture experiments. Ozone-based PMS activation occurs at neutral to alkaline pH and, in the presence of a OH scavenger, removal efficiencies during O 3 /PMS are up to 3 times higher than with the O 3 /H 2 O 2 process. In optimizing the O 3 /PMS process, a trade-off has to made between the desired removal and the PMS:O 3 ratio. A molar ratio of 1:10 already results in a clear benefit compared to the ozonation process. Further increase of the PMS content up to a 1:1 ratio improved the removal by an additional factor of 1.3–1.5. [ABSTRACT FROM AUTHOR]

Removal of toxic organics and bacterial disinfection are important tasks in wastewater treatment. Most heavy metal-based catalysts for degradation of aqueous organic pollutants in heterogeneous Fenton-like processes suffer from the toxicity of leached metals. The present work reports environmentally benign systems for both degradation of organics and bacterial disinfection. Calcium substituted LaFeO 3- δ perovskite was demonstrated as an efficient catalyst to activate peroxymonosulfate (PMS) for degradation of phenol, methylene blue and rhodamine 6 G. Compared to LaFeO 3- δ and nanocrystal Fe 3 O 4 , the lattice oxygen vacancies in B-site cation-deficient perovskite of La 0.8 Ca 0.2 Fe 0.94 O 3 - δ (LaCaFeO 3- δ ) particles renders this material a greatly improved catalytic performance. Electron paramagnetic resonance (EPR) suggested that both sulfate (SO 4 –) and hydroxyl radicals ( OH) played critical roles in the advanced oxidation processes. Moreover, silver doped perovskite (Ag-LaCaFeO 3- δ )/PMS successfully inhibited the growth of waterborne pathogen Escherichia coli and Methicillin-resistant Staphylococcus aureus (MRSA) at a lower dose than silver ions, proving a synergetic effect between free radicals and Ag + in killing the bacteria. Therefore, Ag-LaCaFeO 3- δ /PMS would be promising for practical wastewater treatment. [ABSTRACT FROM AUTHOR]

Recently cobalt-based heterogeneous catalysts have been widely investigated for peroxymonosulfate (PMS) activation in sulfate radical-based advanced oxidation processes. However, the improvement of the catalytic performance for PMS activation remains to be a challenge. As the limiting step, the rapid transformation of Co II /Co III redox pairs is crucial for PMS activation. Perovskites attract increasing attention due to their controllable oxidation state of B-site metal and formation of oxygen vacancies, which accelerates the cycle of redox pairs. LaCo 1-x M x O 3 (M = Cu, Fe and Mn) perovskites as heterogeneous catalysts of PMS were synthesized for the degradation of phenol. The results showed that LaCo 0.4 Cu 0.6 O 3 exhibited the highest catalytic activity. The pseudo first-order kinetic constant of phenol degradation on LaCo 0.4 Cu 0.6 O 3 is 0.302 min −1 , being about 5 times as high as Co 2+ with same molar concentration of cobalt in LaCo 0.4 Cu 0.6 O 3 . XPS analysis confirmed that substitution of copper could promote the cycle of Co II /Co III , thus enhance the catalytic efficiency for PMS activation. The facilitated cycle of Co II /Co III played a crucial role in the generation of sulfate radicals, hydroxyl radicals and singlet oxygen. And sulfate radical was the primary radical responsible for pollutants degradation. The results provide insights into constructing novel perovskite catalysts for the removal of organic pollutants in water. [ABSTRACT FROM AUTHOR]

To activate persulfate to generate reactive species such as sulfate radical (SO 4 •−) for micropollutants abatement, external energy or chemicals are often needed. In this study, a novel SO 4 •− formation pathway was reported during the oxidation of neonicotinoids by peroxydisulfate (S 2 O 8 2−, PDS) without any other chemical additions. Thiamethoxam (TMX) was used as a representative neonicotinoid and SO 4 •− was the dominant specie contributing to its degradation during PDS oxidation at neutral pH. TMX anion radical (TMX•−) was found to activate PDS to generate SO 4 •− with the second-order reaction rate constant determined to be (1.44 ± 0.47)× 106 M−1s−1 at pH 7.0 by using laser flash photolysis. TMX•− was generated from the TMX reactions with superoxide radical (O 2 •−), which was formed from the hydrolysis of PDS. This indirect PDS activation pathway via anion radicals was also applicable to other neonicotinoids. The formation rates of SO 4 •− were found to negatively linearly correlated with E gap (LUMO-HOMO). The DFT calculations indicated the energy barrier of anion radicals to activate PDS was greatly reduced compared to the parent neonicotinoids. The pathway of anion radicals' activation of PDS to form SO 4 •− improved the understanding of PDS oxidation chemistry and provided some guidance to enhance oxidation efficiency in field applications. [Display omitted] • SO 4 •− and HO• are formed during PDS oxidation of thiamethoxam (TMX) at neutral pH. • O 2 •− formed from PDS hydrolysis reduces TMX to form TMX•−. • TMX•− is able to activate PDS to form SO 4 •− at a rate constant of 1.44 × 106 M−1s−1. • The activation of PDS to form SO 4 •− via anion radicals is popular for neonicotinoids. • Indirect PDS activation allows for sufficient contaminant degradation efficiency. [ABSTRACT FROM AUTHOR]

The biotreatment of recalcitrant wastes in microbial fuel cells (MFCs) rather than chemical, physical, and advanced oxidation processes is a low-cost and eco-friendly process. In this study, sulfate-reducing mixed communities in MFC anodic chamber were employed for simultaneous electricity generation, dye degradation, and sulfate reduction. A power generation of 258 ± 10 mW/m 2 was achieved under stable operating conditions in the presence of electroactive sulfate-reducing bacteria (SRB). The SRBs dominant anodic chambers result in dye, chemical oxygen demand (COD), and sulfate removal of greater than 85% at an initial COD (as lactate)/SO 4 2− mass ratio of 2.0 and dye concentration of 100 mg/L. The effects of the COD/SO 4 2− ratio (5.0:1.0–0.5:1.0) and initial diazo dye concentration (100–1000 mg/L) were studied to evaluate and optimize the MFC performance. Illumina Miseq technology for bacterial community analysis showed that Proteobacteria (89.4%) , Deltaproteobacteria (52.7%) , and Desulfovibrio (48.2%) were most dominant at phylum, class, and genus levels, respectively, at the MFC anode. Integration of anaerobic SRB culture in MFC bioanode for recalcitrant chemical removal and bioenergy generation may lead to feasible option than the currently used technologies in terms of overall pollutant treatment. [ABSTRACT FROM AUTHOR]

The ability of persulfate (PS) and peroxymonosulfate (PMS) activated by micron or nanoscale zero-valent copper (ZVC or nZVC) to degrade 2,4-dichlorophenol (2,4-DCP) was quantified under various conditions. Mechanism investigation revealed that PS and PMS accelerated the corrosion of ZVC or nZVC to release Cu + under acidic conditions. The in-situ generated Cu + further decomposed PS or PMS to produce SO 4 − and OH, which then dramatically degraded 2,4-DCP. The k obs for 2,4-DCP removal followed pseudo-first-order kinetics, k obs of ZVC/PMS and nZVC/PMS systems were 10 ∼ 30 times greater than these in ZVC/PS and nZVC/PS systems. The nZVC/PMS system was most effective to remove 2,4-DCP which even did better than the nZVI/PMS system, with rate constant values ranging from 0.041 to 1.855 min −1 . At higher pH ZVC is ineffective, but nZVC can activate PS and PMS to significantly degrade 2,4-DCP at pH up to 7.3. The 2,4-DCP degradation pathway was found to involve dechloridation, dehydrogenation, hydroxylation, ring open and mineralization. 56.7% and 45.3% of TOC removals were respectively obtained in the ZVC/PMS and nZVC/PMS systems within 120 min. This study helps to comprehend the application of zero-valent metals in reactive radicals-based oxidation processes and the reactivity of Cu + as an activator of PS and PMS. [ABSTRACT FROM AUTHOR]

Fluoroquinolones (FQs) are among the most potent antimicrobial agents, which have seen their increasing use as human and veterinary medicines to control bacterial infections. FQs have been extensively found in surface water and municipal wastewaters, which has raised great concerns due to their negative impacts to humans and ecological health. It is of utmost importance that FQs are treated before their release into the environment. This paper reviews oxidative removal of FQs using reactive oxygen (O 3 and OH), sulfate radicals (SO 4 − ), and high-valent transition metal (Mn VII and Fe VI ) species. The role of metals in enhancing the performance of reactive oxygen and sulfur species is presented. The catalysts can significantly enhance the production of OH and/or SO 4 − radicals. At neutral pH, the second-order rate constants ( k , M −1 s −1 ) of the reactions between FQs and oxidants follow the order as k ( OH) > k (O 3 ) > k (Fe VI ) > k (Mn VII ). Moieties involved to transform target FQs to oxidized products and participation of the catalysts in the reaction pathways are discussed. Generally, the piperazinyl ring of FQs was found as the preferential attack site by each oxidant. Meanwhile, evaluation of aquatic ecotoxicity of the transformation products of FQs by these treatments is summarized. [ABSTRACT FROM AUTHOR]

Sulfate radical anion ( S O 4 • − ) and hydroxyl radical ( OH) based advanced oxidation technologies has been extensively used for removal of aromatic contaminants (ACs) in waters. In this study, we investigated the Gibbs free energy ( Δ G SET ∘ ) of the single electron transfer (SET) reactions for 76 ACs with S O 4 • − and OH, respectively. The result reveals that S O 4 • − possesses greater propensity to react with ACs through the SET channel than OH. We hypothesized that the electron distribution within the molecule plays an essential role in determining the Δ G SET ∘ and subsequent SET reactions. To test the hypothesis, a quantitative structure−activity relationship (QSAR) model was developed for predicting Δ G SET ∘ using the highest occupied molecular orbital energies ( E HOMO ), a measure of electron distribution and donating ability. The standardized QSAR models are reported to be Δ G ° SET = −0.97 × E HOMO – 181 and Δ G ° SET = −0.97 × E HOMO − 164 for S O 4 • − and OH, respectively. The models were internally and externally validated to ensure robustness and predictability, and the application domain and limitations were discussed. The single–descriptor based models account for 95% of the variability for S O 4 • − and OH. These results provide the mechanistic insight into the SET reaction pathway of radical and non–radical bimolecular reactions, and have important applications for radical based oxidation technologies to remove target ACs in different waters. [ABSTRACT FROM AUTHOR]

Day and night PM 2.5 samples were collected at coastal and inland stations in a megacity in China. Temporal, spatial, and directional characteristics of PM 2.5 concentrations and compositions were investigated. Average PM 2.5 concentration was higher at inland (153.28 μg/m 3 ) than at coastal (114.46 μg/m 3 ). PM 2.5 were significantly influenced by season and site but insignificantly by diurnal pattern. Sources were quantified by a two-way and a newly developed three-way receptor models conducted using ME2. Secondary sulfate and SOC (SS&SOC, 25% and 23%), coal and biomass burning (CC&BB, 20% and 21%), crustal and cement dust (CRD&CED, 19% and 21%), secondary nitrate (SN, 13% and 18%), vehicular exhaust (VE, 14% and 17%), and sea salt (SEA, 6% and 2%) were major sources for coastal and inland. Different mechanisms of heavy pollution were observed: heavy PM 2.5 caused by primary sources and secondary sources showed similar frequency at coast, while most of heavy pollutions at inland site might be associated with the elevation of secondary particles. For spatial characteristics, SS&SOC, CRD&CED contributions were higher at coastal; SN and VE presented higher fractions at inland. Higher SS&SOC, SN and CC&BB in winter might be attributed to intensive coal combustion for residential warming and to stable meteorological conditions. [ABSTRACT FROM AUTHOR]

The priority pollutant antimony (Sb) exists primarily as Sb(V) and Sb(III) in natural waters, and Sb(III) is generally with greater mobility and toxicity than Sb(V). The bio-reduction of Sb(V) would not become a meaningful Sb-removal process unless the accumulation of produced dissolved Sb(III) could be controlled. Here, we examined the dissimilatory antimonate bio-reduction with or without the coexistence of sulfate using Sb-acclimated biomass. Results demonstrated that 0.8 mM Sb(V) was almost completely bio-reduced within 20 h along with 48.6% Sb(III) recovery. Kinetic parameters q max and K s calculated were 0.54 mg-Sb mg-DW −1 h −1 and 41.96 mg L −1 , respectively. When the concentrations of coexisting sulfate were 0.8 mM, 1.6 mM, and 4 mM, the reduction of 0.8 mM Sb(V) was accomplished within 17, 9, and 5 h, respectively, along with no final Sb(III) recovery. Also, the bio-reduction of sulfate occurred synchronously. The precipitated Sb 2 O 3 and Sb 2 S 3 were characterized by scanning electron microscopy coupled with energy dispersive spectrometer, X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with bacterial compositions of the seed sludge obtained from anaerobic digestion tank in a wastewater treatment plant, new genera of Pseudomonas and Geobacter emerged with large proportions in both Sb-fed and Sb-sulfate-fed sludge, and a small portion of sulfate reduction bacteria emerged only in Sb-sulfate-fed culture. [ABSTRACT FROM AUTHOR]

A magnetic cobalt ferrite (CoFe 2 O 4 ) catalyst was prepared by sol-gel method, and characterized by a X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller (BET) and hysteresis loop method. The chemical states on surface of the fresh and spent catalysts were analyzed by a X-ray photoelectron spectroscopy (XPS). The experiments of elemental mercury (Hg 0 ) removal from flue gas were conducted in a laboratory scale using activated peroxymonosulfate (PMS) catalyzed by CoFe 2 O 4 , and the effects of the dosage of catalyst, the concentration of PMS, initial solution pH and reaction temperature on mercury removal efficiency were investigated. The average removal efficiency of Hg 0 could maintain steady at 85% in 45 min when the concentrations of CoFe 2 O 4 and PMS were 0.288 g/L and 3.5 mmol/l respectively, solution pH was 7 and reaction temperature was 55 °C. In order to speculate the reaction mechanism, ethyl alcohol and isopropyl alcohol were used as the quenching agents to indirectly prove the existence of SO 4 − and OH. [ABSTRACT FROM AUTHOR]

Soil attenuation of off-site leaching potential of metallic elements at the two abandoned mine sites was investigated using batch sorption and layered column studies. In batch study, the leachate concentration-specific sorption ( K d * ) by downgradient clean soils was in the order of Pb > Cu > Cd > Zn > As for DY site and Pb > As > Cu > Cd > Zn for BS site. In the layered (mine + clean) soil column, element elution was significantly reduced (e.g., no initial flush, retarded peak arrival, and lower peak concentration) while sulfate elution can be an indicator of the dissolution of sulfur-bearing minerals in mine soils. The greatest reduction was observed for Pb and Cu while the lowest was for Cd (2–19%) and Zn (6–51%), consistent with the batch data. Both the reduced elution at slow seepage and concentration drop after flow interruption support the time-limited propensity. In column segments, the sorptive elements (Cu, Pb, and As) were dominantly found in the inlet while less sorptive ones (Zn and Cd) in the outlet. Both batch and column data suggest that the element leaching with mine leachate movement can be greatly attenuated by the interactions with the surrounding downgradient soil during the seepage process. [ABSTRACT FROM AUTHOR]

Dissimilatory arsenate-respiring prokaryotes (DARPs) play key roles in the mobilization and release of arsenic from mineral phase into groundwater; however, little is known about how environmental factors influence these processes. This study aimed to explore the effects of sulfate on the dissolution and release of insoluble arsenic. We collected high-arsenic sediment samples from different depths in Jianghan Plain. Microcosm assays indicated that the microbial communities from the samples significantly catalyzed the dissolution, reduction and release of arsenic and iron from the sediments. Remarkably, when sulfate was added into the microcosms, the microorganisms-mediated release of arsenic and iron was significantly increased. To further explore the mechanism of this finding, we isolated a novel DARP, Citrobacter sp. JH001, from the samples. Arsenic release assays showed that JH001 can catalyze the dissolution, reduction and release of arsenic and iron from the sediments, and the presence of sulfate in the microcosms also caused a significant increase in the JH001-mediated dissolution and release of arsenic and iron. Quantitative PCR analysis for the functional gene abundances showed that sulfate significantly increased the arsenate-respiring reductase gene abundances in the microcosms. Thus, it can be concluded that sulfate significantly enhances the arsenate-respiring bacteria-mediated arsenic contamination in groundwater. [ABSTRACT FROM AUTHOR]

High arsenic concentrations have been detected in alluvial aquifers of arid and semi-arid zones in Mexico. This work describes the potential of microbial arsenate reduction of the indigenous community present in sediments from an arsenic contaminated aquifer. Microcosms assays were conducted to evaluate arsenate and sulfate-reducing activities of the native microbiota. Two different sediments were used as inoculum in the assays amended with lactate (10 mM) as electron donor and with sulfate and arsenate (10 mM each) as electron acceptors. Sediments were distinguished by their concentration of total arsenic 238.3 ± 4.1 mg/kg or 2263.1 ± 167.7 mg/kg, which may be considered as highly contaminated sediments with arsenic. Microbial communities present in both sediments were able to carry out arsenate reduction, accomplished within 4 days, with the corresponding formation of arsenite; sulfate reduction took place as well. Both reducing activities occurred without previous acclimation period or enrichment, even at potential inhibitory concentrations of arsenate as high as 750 mg/L (10 mM). The formation of a yellowish colloidal precipitate was evident when both reducing processes occurred in the microcosm, which contributed to remove between 52 and 90.9% of As(III) from the liquid phase by bioprecipitation of arsenic as arsenic sulfide. [ABSTRACT FROM AUTHOR]

Electro-assisted Fenton-like (EAFL) system based on sulfate radicals (SO 4 − ) has been extensively explored for the degradation of recalcitrant organic contaminant. Nevertheless, external power supply should be provided uninterruptedly in the EAFL process and thus the high energy consumption is ineluctable. Recently, microbial fuel cell (MFC), a bio-electrochemical system where exoelectricigens are used to catalyze fuels into electricity energy has gained popularity mainly due to its renewability. Herein, a novel heterogeneous EAFL system, hydronium jarosite (HJ) activation of peroxymonosulfate (PMS) in an electrochemical reactor driven by an uncoated single-chamber MFC (MFC/HJ/PMS), was employed to decolorize acid orange 7 (AO7). The results suggest that the MFC/HJ/PMS system can remove AO7 efficiently in a wide pH range (3–9). The concentration of total iron leached could meet European Union discharge standards and hydronium jarosite could be used at least three circles. The results of electron paramagnetic resonance analysis and radical scavenging experiments indicate SO 4 − is the major active species responsible for the AO7 elimination. The work provides an efficient, energy-saving and cost-effective approach to treat organic wastewater and develops the conceivable utilization of hydronium jarosite, precipitates produced in hydrometallurgical process. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation is considered to be an attractive alternative to chemical oxidation for the treatment of polluted water. Given the of ability of boron-doped diamond (BDD) electrodes to generate hydroxyl radicals ( OH), they are often selected for the degradation of persistent organic contaminants. Recently, BDD anodes have been demonstrated to form strong oxidants, sulfate radicals (SO 4 − ), directly from sulfate ions. In this study, electrochemical activation of sulfate to SO 4 − at BDD anodes enhanced the removal of an antibiotic sulfamethoxazole (SMX). The rate of SMX oxidation was 6 times higher in sulfate anolyte compared to inert nitrate anolyte. Addition of chloride accelerated the disappearance of SMX in both anolytes due to electrochlorination. Yet, mineralization efficiency was decreased, particularly in Na 2 SO 4 anolyte due to the scavenging of SO 4 − by Cl − . Electrogenerated SO 4 − yielded nitroso- and nitro-derivatives, which were not observed in the absence of sulfate. The peak intensities of chlorinated TPs were three orders of magnitude lower in Na 2 SO 4 than in NaNO 3 anolyte, suggesting that addition of sulfate may lower the formation of chlorinated organics. However, attention should be paid to the formation of inorganic byproducts, as the formation rates of toxic chlorate and in particular perchlorate were higher in Na 2 SO 4 anolyte. [ABSTRACT FROM AUTHOR]

Hydroponic experiments were performed to examine the effect of prolonged sulfate limitation combined with cadmium (Cd) exposure in Arabidopsis thaliana and a potential Cd hyperaccumulator, Nicotiana tabacum. Low sulfate treatments (20 and 40 µM MgSO 4) and Cd stress (4 µM CdCl 2) showed adverse effects on morphology, photosynthetic and biochemical parameters and the nutritional status of both species. For example, Cd stress decreased NO 3 - root content under 20 µM MgSO 4 to approximately 50% compared with respective controls. Interestingly, changes in many measured parameters, such as chlorophyll and carotenoid contents, the concentrations of anions, nutrients and Cd, induced by low sulfate supply, Cd exposure or a combination of both factors, were species-specific. Our data showed opposing effects of Cd exposure on Ca, Fe, Mn, Cu and Zn levels in roots of the studied plants. In A. thaliana, levels of glutathione, phytochelatins and glucosinolates demonstrated their distinct involvement in response to sub-optimal growth conditions and Cd stress. In shoot, the levels of phytochelatins and glucosinolates in the organic sulfur fraction were not dependent on sulfate supply under Cd stress. Altogether, our data showed both common and species-specific features of the complex plant response to prolonged sulfate deprivation and/or Cd exposure. [Display omitted] • Effects of low S and Cd stress on nutrient composition are mostly species specific. • Under restricted S, Cd does not negatively affect GLS content in A. thaliana shoot. • Cd affects chlorophyll a/b ratio in A. thaliana , but not in N. tabacum. • S supply interacts with Cd stress in inhibition of photosynthetic processes at PSII. [ABSTRACT FROM AUTHOR]

In this study the feasibility of treating dyeing wastewater with sulfate reducing granular sludge was explored, focusing on decolorization/degradation of azo dye (Procion Red HE-7B) and the performance of microbial consortia under alkaline conditions (pH = 11). Efficiency of HE-7B degradation was influenced strongly by the chemical oxygen demand (COD) concentration which was examined in the range of 500–3000 mg/L. COD removal efficiency was reduced at high COD concentration, while specific removal rate was enhanced to 17.5 mg-COD/g VSS h −1 . HE-7B removal was also improved at higher organic strength with more than 90% removal efficiency and a first-rate removal constant of 5.57 h −1 for dye degradation. Three dye-degradation metabolites were identified by HPLC–MS. The granular structure provided enhanced removal performance for HE-7B and COD in comparison to a near-identical floc SRB system and the key functional organisms were identified by high throughput sequencing. This study demonstrates an example of a niche application where SRB granules can be applied for high efficient and cost-effective treatment of a wastewater under adverse environmental conditions. [ABSTRACT FROM AUTHOR]

The development of transition metal based heterogeneous catalysts with efficient reactivity and intensive stability is of great demand in peroxymonosulfate based AOPs in water treatment. Herein, we present a novel approach of creating stable and effective nano-rod catalyst of CuCo@MnO 2 with tetragonal structure. A remarkable synergetic effect was found between bi-metallic oxides of Cu and Co: 0.5%Cu-2%Co-MnO 2 can efficiently degrade 100% of 30 ppm phenol, while 0.5%Cu@MnO 2 or 2%Co@MnO 2 alone is apparently sluggish for the degradation of organic contaminants. The nanocatalyst retained good stability in recycling tests, during which little leaching of Co and Cu ions can be detected and crystallinity of support α˗MnO 2 remained unchanged. Mechanism study indicated that SO 4 − and OH are accounted to participate the degradation, and the generation of radicals is originated from the interaction of CuCo@MnO 2 and PMS through metal site with peroxo species bond. The redox cycle among the active metals (M 2+ ↔ M 3+ ↔ M 2+ ) and Cu enhanced generation of Co(II)–OH complex are critical for the remarkable performance in CuCo@MnO 2 /PMS system. Both the synergetic acceleration of catalyst activity and instinct mechanism are highly suggestive to the design of heterogeneous catalysts for the degradation of organic contaminants in PMS based advanced oxidation processes. [ABSTRACT FROM AUTHOR]

A new catalyst system of CoP/peroxymonosulfate (PMS) is presented, which achieved significant improvement in catalytic activity. Nanostructured CoP, obtained by a simple solid-state reaction, exhibited dramatic catalytic activity with 97.2% degradation of orange II of 100 ppm within 4 min. Moreover, the high efficiency could be reached for other phenolic pollutants, i.e., phenol and 4-chlorophenol. The reaction rate is much higher than the most reported catalysts. Effect of parameters on catalytic activity of the catalyst was studied in detail. Notably, initial pH of the solution had a slight negative effect on the catalytic performance over the pH range 4.07–10.92, suggesting that CoP has the great adaptability of pH. CoP/PMS demonstrated excellent anti-interference performance toward anions (Cl − , NO 3 − , and HCO 3 − ). In addition, the pathway of degradation of orange II is proposed by analyzing its intermediates. Based on the XPS spectra of CoP, the identification of the reactive species ( OH and SO 4 − ) by electron paramagnetic resonance (EPR) analysis and quenching tests, a possible mechanism for activation of PMS by CoP was proposed. Considering the dramatic catalytic activity, a wide range of pH catalyst suited, CoP is believed to provide robust support for the promising industrial application of AOPs. [ABSTRACT FROM AUTHOR]

A surface–active Bi 2 Fe 4 O 9 nanoplates (BF–nP) was prepared using a facile hydrothermal protocol for sulfamethoxazole (SMX) removal via peroxymonosulfate (PMS). The catalytic activity of BF–nP was superior to other catalysts with the following order of performance: BF–nP > Bi 2 Fe 4 O 9 (nanocubes) >> Co 3 O 4 > Fe 2 O 3 (low temperature co–precipitation method) > Fe 2 O 3 (hydrothermal method) ∼ Bi 2 O 3 ∼ Bi 3+ ∼ Fe 3+ . The empirical relationship of the apparent rate constant ( k app ), BF–nP loading and PMS dosage can be described as follows: k app = 0.69[BF–nP] 0.6 [PMS] 0.4 (R 2 = 0.98). The GC–MS study suggests that the SMX degradation proceed mainly through electron transfer reaction. The XPS study reveals that the interconversion of Fe 3+ /Fe 2+ and Bi 3+ /Bi 5+ couples are responsible for the enhanced PMS activation. The radical scavenging study indicates that SO 4 − is the dominant reactive radical (>92% of the total SMX degradation). A method to quantify SO 4 − in the heterogeneous Bi 2 Fe 4 O 9 /PMS systems based on the quantitation of benzoquinone, which is the degradation byproduct of p –hydroxybenzoic acid and SO 4 − , is proposed. It was found that at least 7.8 ± 0.1 μM of SO 4 − was generated from PMS during the BF–nP/PMS process (0.1 g L −1 , 0.40 mM PMS, natural pH). The Bi 2 Fe 4 O 9 nanoplates has a remarkable potential for use as a reusable, nontoxic, highly–efficient and stable PMS activator. [ABSTRACT FROM AUTHOR]

A series of experiments were conducted for treating heavy metals contaminated sediments sampled from Xiangjiang River, which combined polyvinyl alcohol (PVA) and immobilized sulfate reducing bacteria (SRB) into beads. The sodium lactate was served as the inner cohesive nutrient. Coupling the activity of the SRB with PVA, along with the porous structure and huge specific surface area, provided a convenient channel for the transmission of matter and protected the cells against the toxicity of metals. This paper systematically investigated the stability of Cu, Zn, Pb and Cd and its mechanisms. The results revealed the performance of leaching toxicity was lower and the removal efficiencies of Cu, Zn, Pb and Cd were 76.3%, 95.6%, 100% and 91.2%, respectively. Recycling experiments showed the beads could be reused 5 times with superbly efficiency. These results were also confirmed by continuous extraction at the optimal conditions. Furthermore, X-ray diffraction (XRD) and energy-dispersive spectra (EDS) analysis indicated the heavy metals could be transformed into stable crystal texture. The stabilization of heavy metals was attributed to the carbonyl and acyl amino groups. Results presented that immobilized bacteria with inner nutrient were potentially and practically applied to multi-heavy-metal-contamination sediment. [ABSTRACT FROM AUTHOR]

Heterogeneous catalytic activation is important for potential application of new sulfate-radical-based advanced oxidation process using sulfite as source of sulfate radical. We report herein a heterogeneous system for sulfite activation by CoFe 2 O 4 nanocatalyst for metoprolol removal. Factors that influence metoprolol removal were investigated, including pH and initial concentrations of components. The CoFe 2 O 4 nanocatalyst was characterized by X-ray diffractometry (XRD) and transmission electron microscopy (TEM), and the catalytic stability was tested by consecutive runs. Radicals generated in the CoFe 2 O 4 S(IV) O 2 system were identified through radical quenching experiments and by electron spin resonance (ESR). The catalytic mechanism was elucidated further by X-ray photoelectron spectroscopy (XPS). The catalytic process was dependent on initial pH, and more than 80% of the metoprolol can be removed at pH 10.0 following the Langmubir-Hinshelwood equation. The generation of Co-OH complexes on the CoFe 2 O 4 surface was crucial for sulfite activation. SO 4 − was verified to be the main oxidative species responsible for metoprolol degradation. Other organic pollutants, such as sulfanilamide, sulfasalazine, 2-nitroaniline, sulfapyridine, aniline, azo dye X-3B and 4-chloroaniline, could also be removed in this CoFe 2 O 4 S(IV) O 2 system. The results suggest that the CoFe 2 O 4 S(IV) O 2 system has good application prospects in alkaline organic wastewater treatment. [ABSTRACT FROM AUTHOR]

A heterogeneous manganese/magnetite/graphene oxide (Mn-MGO) hybrid catalyst was fabricated through the reduction of KMnO 4 by ethylene glycol in the presence of magnetite/GO (MGO) particles. The Mn-MGO catalyst exhibited high efficacy and long-term stability in activating peroxymonosulfate (PMS) to generate sulfate radicals for the removal of bisphenol A (BPA) from water. The results of the batch experiments indicated that an increase in the catalyst dose and solution pH could enhance BPA degradation in the coupled Mn-MGO/PMS system. Regardless of the initial pH, the solution pH significantly dropped after the reaction, which was caused by catalytic PMS activation. The production of sulfate radicals and hydroxyl radicals was validated through radical quenching and electron paramagnetic resonances (EPR) tests. BPA degradation pathways were proposed on the basis of LC–MS and GC–MS analyses. Finally, a possible mechanism of catalytic PMS activation was proposed that involved electron transfer from MnO or Mn 2 O 3 to PMS with the generation of sulfate radicals, protons and MnO 2 , as well as the simultaneous reduction of MnO 2 by PMS. [ABSTRACT FROM AUTHOR]

In this study, an earth-mimetic method was proposed for the direct removal of As(III) by the formation of tooeleite, a ferric arsenite sulfate mineral. A series of batch experiments was used to study the relationship between the formation of tooeleite and the removal of As(III). The results indicate that As(III) removal efficiency reached up to 99% under the treatment condition of pH 1.8–4.5, initial As(III) concentration higher than 0.75 g/L, and Fe/As ranged from 0.8 to 2 at room temperature. Various characterizations confirm that the precipitate obtained by this treatment was tooeleite with relatively high stability. In addition, it is assumed that ferrihydrite exists as a precursor, which is vital to the formation of tooeleite and the removal of As(III). This study suggests that tooeleite formation may be an alternative method in the direct removal of As(III) from high-arsenic acid wastewater. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) has been shown to effectively activate peroxymonosulfate (PMS) to remove contaminants, whereas controversial activation mechanisms (radical vs non-radical mechanism) were previously proposed. Here we report that radical-induced decolorization of acid orange 7 (AO7) dominated in the CNT activated PMS system, but non-radical mechanism was also involved at high Cl − concentration. CNT exhibited high activity in activating PMS to decolorize AO7. The decolorization rate of AO7 increased with increasing PMS dosages and CNT loadings, rising temperature and higher pH. Radical quenching and photoluminescence techniques confirmed the decolorization of AO7 in the CNT/PMS system was caused by the radical oxidation, which dominantly took place on the surface of CNT, rather than the bulk solution. The presence of Cl − exhibited a dual effect on AO7 decolorization. Low concentration of Cl − slightly inhibited AO7 decolorization, but further raising the concentration to above 0.1 M significantly accelerated its decolorizaition. Cl − was confirmed to react with PMS to generate HClO, which effectively bleached AO7 through non-radical process rather than radical process. The decolorization of AO7 induced from the non-radical process exhibited different degradation products and less mineralization in comparison to that derived from radical process. [ABSTRACT FROM AUTHOR]

In this work, a new effective and relatively stable heterogeneous catalyst of Metal-Organic Framework Co 3 (BTC) 2 ·12H 2 O (Co-BTC) has been synthesized and tested to activate peroxymonosulfate (PMS) for removal of refractory dibutyl phthalate (DBP). Co-BTC(A) and Co-BTC(B) were synthesized by different methods, which resulted in different activity towards PMS. The results indicated that Co-BTC(A) showed better performance on DBP degradation. The highest degradation rate of 100% was obtained within 30 min. The initial pH showed respective level on DBP degradation with a rank of 5.0 > 2.75 > 9.0 > 7.0 > 11.0 in PMS/Co-BTC(A) system. No remarkable reduction of DBP was observed in the catalytic activity of Co-BTC(A) at 2nd run as demonstrated by recycling. However, the DBP degradation efficiency decreased by 8.26%, 10.9% and 25.6% in the 3rd, 4th, and 5th runs, respectively. The loss of active catalytic sites of Co(II) from Co-BTC(A) is responsible for the activity decay. Sulfate radicals (SO 4 − ) and hydroxyl radicals ( OH) were found at pH 2.75. Here, we propose the possible mechanism for activation of PMS by Co-BTC(A), which is involved in homogeneous and heterogeneous reactions in the solutions and the surface of Co-BTC(A), respectively. [ABSTRACT FROM AUTHOR]

Microscaled CuFeO 2 particles (micro-CuFeO 2 ) were rapidly prepared via a microwave-assisted hydrothermal method and characterized by scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy. It was found that the micro-CuFeO 2 was of pure phase and a rhombohedral structure with size in the range of 2.8 ± 0.6 μm. The micro-CuFeO 2 efficiently catalyzed the activation of peroxymonosulfate (PMS) to generate sulfate radicals (SO 4 −), causing the fast degradation of carbamazepine (CBZ). The catalytic activity of micro-CuFeO 2 was observed to be 6.9 and 25.3 times that of micro-Cu 2 O and micro-Fe 2 O 3 , respectively. The enhanced activity of micro-CuFeO 2 for the activation of PMS was confirmed to be attributed to synergistic effect of surface bonded Cu(I) and Fe(III). Sulfate radical was the primary radical species responsible for the CBZ degradation. As a microscaled catalyst, micro-CuFeO 2 can be easily recovered by gravity settlement and exhibited improved catalytic stability compared with micro-Cu 2 O during five successive degradation cycles. Oxidative degradation of CBZ by the couple of PMS/CuFeO 2 was effective in the studied actual aqueous environmental systems. [ABSTRACT FROM AUTHOR]

Monoethanolamine (MEA), a toxic organic chemical, is widely used in industries and is found in their wastewater. Anaerobic MEA degradation is an appropriate strategy to reduce energy and cost for treatment. Industry wastewaters also contain sulfate, but information on the effects of sulfate on MEA degradation is limited. Here, an up-flow anaerobic sludge blanket (UASB) for MEA-containing wastewater treatment was operated under psychrophilic conditions (18–20 ºC) to investigate the effects of sulfate on the microbial characteristics of the retained sludge. To acclimatize the sludge, the proportion of MEA in the influent (containing sucrose, acetate, and propionate) was increased from 15% to 100% of total COD (1500 mg L–1); sulfate was then added to the influent. The COD removal efficiency remained above 95% despite the increase in MEA and sulfate. However, granular sludge disintegration was observed when sulfate was increased from 20 to 330 mg L–1. Batch tests revealed that propionate and acetate were produced as the metabolites of MEA degradation. In response to sulfate acclimation, methane-producing activities for propionate and hydrogen declined, while sulfate-reducing activities for MEA, propionate, and hydrogen increased. Accordingly, acclimation and changes in dominant microbial groups promoted the acetogenic reaction of propionate by sulfate reduction. [Display omitted] • Monoethanolamine (MEA) was satisfactorily removed by UASB treatment. • Increasing sulfate levels in wastewater caused deterioration of the retained sludge. • Propionate and acetate were detected as anaerobic degradation products of MEA. • Microbial community structure was markedly changed by increasing MEA and sulfate. [ABSTRACT FROM AUTHOR]

The removal of bisphenol A (BPA) in aqueous solution by an oxidation process involving peroxymonosulfate (PMS) activated by CuFe 2 O 4 magnetic nanoparticles (MNPs) is reported herein. The effects of PMS concentration, CuFe 2 O 4 dosage, initial pH, initial BPA concentration, catalyst addition mode, and anions (Cl − , F − , ClO 4 − and H 2 PO 4 − ) on BPA degradation were investigated. Results indicate that nearly complete removal of BPA (50 mg/L) within 60 min and 84.0% TOC removal in 120 min could be achieved at neutral pH by using 0.6 g/L CuFe 2 O 4 MNPs and 0.3 g/L PMS. The generation of reactive radicals (mainly hydroxyl radicals) was confirmed using electron paramagnetic resonance (EPR). Possible mechanisms on the radical generation from CuFe 2 O 4 /PMS system are proposed based on the results of radical identification tests and XPS analysis. The lack of inhibition of the reaction by free radical scavengers such as methanol and tert -butyl alcohol suggests that these species may not be generated in the bulk solution, and methylene blue probe experiments confirm that this process does not involve free radical generation. Surface-bound, rather than free radicals generated by a surface catalyzed-redox cycle involving both Fe(III) and Cu(II), are postulated to be responsible for the mineralization of bisphenol A. [ABSTRACT FROM AUTHOR]

Magnetic spinel ferrites, as heterogeneous catalysts to generate powerful radicals from peroxymonosulfate (PMS) for the degradation of organic pollutants, have received much attention in recent years due to the characteristic of environmental benefits. In this study, with titanate nanotubes (TNTs) as catalyst support, a novel CoFe 2 O 4 /TNTs hybrid was constructed by an impregnation-calcination method. Characterization results revealed that TNTs support could promise small size and good dispersion of CoFe 2 O 4 nanoparticles. Compared to the pure CoFe 2 O 4 , the as-prepared CoFe 2 O 4 /TNTs not only exhibited better performance in catalytic decomposition of Rhodamine B, but also realized higher total organic carbon removal and less cobalt leaching, which could be attributed to the enhanced catalytic ability from smaller CoFe 2 O 4 nanoparticles and the unique ion-exchange ability from TNTs support. Some influential factors, including reaction temperature, dosages of PMS and CoFe 2 O 4 /TNTs, and pH values were investigated and analyzed. Moreover, CoFe 2 O 4 /TNTs maintained its catalytic efficiency during the repeated batch experiments and also displayed functional advantages in the catalytic degradation of phenol. We believe the CoFe 2 O 4 /TNTs hybrid can be an efficient and green heterogeneous catalyst for the degradation of organic pollutants, and this study provides insights into the rational design and development of alternative catalysts for wastewater treatment. [ABSTRACT FROM AUTHOR]

The risks associated with dust explosions still exist in industries that either process or handle combustible dust. This explosion risk could be prevented or mitigated by applying the principle of inherent safety (moderation). This is achieved by adding an inert material to a highly combustible material in order to decrease the ignition sensitivity of the combustible dust. The presented paper deals with the experimental investigation of the influence of adding an inert dust on the minimum ignition energy and the minimum ignition temperature of the combustible/inert dust mixtures. The experimental investigation was done in two laboratory scale equipment: the Hartmann apparatus and the Godbert-Greenwald furnace for the minimum ignition energy and the minimum ignition temperature test respectively. This was achieved by mixing various amounts of three inert materials (magnesium oxide, ammonium sulphate and sand) and six combustible dusts (brown coal, lycopodium, toner, niacin, corn starch and high density polyethylene). Generally, increasing the inert materials concentration increases the minimum ignition energy as well as the minimum ignition temperatures until a threshold is reached where no ignition was obtained. The permissible range for the inert mixture to minimize the ignition risk lies between 60 to 80%. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop microbial electrolysis cell (MEC) with a novel acidophilic and autotrophic biocathode for treatment of acid wastewater. A biocathode was developed using acidophilic sulfate-reducing bacteria as the catalyst. Artificial wastewater with 200 mg L −1 sulfate and different Zn concentrations (0, 15, 25, and 40 mg L −1 ) was used as the MEC catholyte. The acidophilic biocathode dominated by Desulfovibrio sp. with an abundance of 66% (with 82% of Desulfovibrio sequences similar to Desulfovibrio simplex ) and achieved a considerable sulfate reductive rate of 32 g m −3 d −1 . With 15 mg L −1 Zn added, the sulfate reductive rate of MEC improved by 16%. The formation of ZnS alleviated the inhibition from sulfide and sped the sulfate reduction. With 15 and 25 mg L −1 Zn added, more than 99% of Zn was removed from the wastewater. Dissolved Zn ions in the catholyte were converted into insoluble Zn compounds, such as zinc sulfide and zinc hydroxide, due to the sulfide and elevated pH produced by sulfate reduction. The MEC with acidophilic and autotrophic biocathode can be used as an alternative to simultaneously remove sulfate and metals from acid wastewaters, such as acid mine drainage. [ABSTRACT FROM AUTHOR]

This study explored the efficacy and efficiency of a simultaneous UV-catalyzed oxidation–coagulation process of titanium sulfate (UV/Ti(SO 4 ) 2 ) for efficient removal of As(III) from water. It revealed that, As(III) could be oxidized to As(V) during the UV catalyzed coagulation of Ti(SO 4 ) 2 with highly efficient As(III) removal in the pH range 4–6 . The UV catalyzed oxidation–coagulation showed surprisingly effective oxidation of As(III) to As(V) within a short time. XPS indicated that 84.7% of arsenic on the coagulated precipitate was in the oxidized form of As(V) after the UV/Ti(SO 4 ) 2 treatment of As(III) aqueous solutions at pH 5. Arsenic remaining in solution at high pH was in the oxidized form As(V). Removal efficiencies of As(III) were investigated as a function of pH, Ti(SO 4 ) 2 dosage, initial As(III) concentration and irradiation energy. As(III) could almost completely be removed (>99%) by the photocatalytic oxidation–coagulation process with a moderate dose of Ti(SO 4 ) 2 in the pH range 4–6 at an initial arsenic concentration of 200 μg/L. The mechanisms of the photocatalytic coagulation oxidation of Ti(SO 4 ) 2 are similar to those of UV/crystalline TiO 2 particles, involving the formation and reactions of the hydroxyl radical OH and superoxide HO 2 /O 2 − . [ABSTRACT FROM AUTHOR]

The pollution risk of dilute acidic sulfate effluent (DASE),which is discharged from titanium dioxide factories heavily every year, has sparked the recycling of sulfuric acid, iron and water. In this study, a new green recovery process for the DASE is proposed based on coupling solventextraction–oxidation–hydrolysis. Compared to the conventional ways, this innovative method allows the effective extraction of sulfuric acid and the precipitation of Fe x O y · n H 2 O in onestep without adding inorganic neutralizer or precipitant. Trioctylamine (TOA) in kerosene (20–50%) was used as an organic phase for solvent extraction. The hydrolytic productions and the raffinate purified by a cation exchange were evaluated using XRD and ICP-OES, respectively. The initial pH of 0.63 and Fe(II) concentration of 0.1 mol/L in the DASE, the volume ratio of organic toaqueous phase (O/A) of 3/1, and reaction temperature of 25 °C were determined as the optimal conditions. Under this conditions, Fe(II) was transformed as yellow precipitation which was characterized as α-FeOOH, and pH of raffinate was in the range of 3.6–3.8. [ABSTRACT FROM AUTHOR]

A series of Co x Mn 3− x O 4 particles as Fenton-like solid catalysts were synthesized, and their catalytic performance in oxidative degradation of organic dye compounds in water was investigated. The surface morphology and structure of the Co x Mn 3− x O 4 catalysts were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that, as an oxide composite of Co and Mn elements, CoMn 2 O 4 showed much stronger catalytic activity in peroxymonosulfate (PMS) oxidation than Co 3 O 4 , Mn 2 O 3, and their physical mixture. Typically, the uses of 0.02 g/dm 3 CoMn 2 O 4 and 0.2 g/dm 3 PMS yielded a nearly complete removal of Rhodamine B (0.03 g/dm 3 ) in 80 min at 25 °C. The efficiency of Rhodamine B decomposition increased with increasing temperature (15–55 °C), but decreased with the increase of fulvic acid concentration (0–0.08 g/dm 3 ). Furthermore, CoMn 2 O 4 could maintain its catalytic activity in the repeated batch experiments. Moreover, HO and SO 4 − radicals participating in the process were evidenced using quenching experiments, and a rational mechanism was proposed. PMS oxidation with CoMn 2 O 4 is an efficient technique for remediation of organic contaminants in wastewater. [ABSTRACT FROM AUTHOR]

Biological technology used to treat flue gas is useful to replace conventional treatment, but there is sulfide inhibition. However, no sulfide toxicity effect was observed in haloalkaliphilic bioreactors. The performance of the ethanol-fed bioreactor was better than that of lactate-, glucose-, and formate-fed bioreactor, respectively. To support this result strongly, Illumina MiSeq paired-end sequencing of 16S rRNA gene was applied to investigate the bacterial communities. A total of 389,971 effective sequences were obtained and all of them were assigned to 10,220 operational taxonomic units (OTUs) at a 97% similarity. Bacterial communities in the glucose-fed bioreactor showed the greatest richness and evenness. The highest relative abundance of sulfate-reducing bacteria (SRB) was found in the ethanol-fed bioreactor, which can explain why the performance of the ethanol-fed bioreactor was the best. Different types of SRB, sulfur-oxidizing bacteria, and sulfur-reducing bacteria were detected, indicating that sulfur may be cycled among these microorganisms. Because high-throughput 16S rRNA gene paired-end sequencing has improved resolution of bacterial community analysis, many rare microorganisms were detected, such as Halanaerobium , Halothiobacillus , Desulfonatronum , Syntrophobacter , and Fusibacter . 16S rRNA gene sequencing of these bacteria would provide more functional and phylogenetic information about the bacterial communities. [ABSTRACT FROM AUTHOR]

In this study, the transformation of five amino acids (AAs), i.e., glycine (GLY), alanine (ALA), serine (SER), aspartic acid (ASP), and methionine (MET), in a heat activated peroxydisulfate (PDS) oxidation process was investigated. Experimental data showed that the nitrogen in the AA molecules was oxidized to NH 4 + and nitrate (NO 3 -) sequentially. However, in the presence of natural organic matter (NOM), nitrophenolic byproducts including 4-nitrophenol, 2,4-dinitrophenol, 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid were formed. The nitrogen dioxide radical (NO 2 •) generated during the transformation of NH 4 + to NO 3 - was presumed to be the key nitrating agent. It reacted with phenolic moieties in NOM and was transformed to nitrophenolic byproducts. Among the selected AAs, SER showed the highest nitrophenolic byproducts formation potential. A total yield of 0.258 μM was observed at the condition of 0.1 mM SER, 5 mg/L (as TOC) NOM, 2 mM PDS, and pH 7.0. The formation from GLY and ALA was lowest, only 0.009 μM detected under the same conditions. The nitrophenolic byproducts formation potential of the AAs was positively related to their reactivity toward SO 4 •- and can be explained by the local nucleophilicity index (N k). These findings underline the potential risks in the application of SO 4 •- based oxidation technology. [Display omitted] • Nitrophenolic byproducts were formed during the degradation of AAs by heat/PDS. • NO 2 • formed during the transformation of NH 4 + to NO 3 - was the nitrating agent. • AA's reactivity to SO 4 •- dictates its nitrophenolic byproducts formation potential. • Transformation pathways of AAs in the heat/PDS process were proposed. [ABSTRACT FROM AUTHOR]