Removal of Antimony in Wastewater by Antimony Tolerant Sulfate-Reducing Bacteria Isolated from Municipal Sludge.

Antimony (Sb), a global and priority controlled pollutant, causes severe environmental issues. Bioremediation by microbial communities containing sulfate-reducing bacteria (SRB) is considered to be among the safest, economical, and environmentally friendly methods to remove Sb from wastewater. However, the roles of SRB species in these communities remain uncertain, and pure cultures of bacteria that may be highly efficient have not yet been developed for Sb removal. In this study, an Sb tolerant community was enriched from municipal sludge, and molecular ecological analysis showed that Escherichia (40%) and Desulfovibrio (15%) were the dominant bacteria. Further isolation and identification showed that the enriched SRB strains were closely related to Cupidesulfovibrio oxamicus, based on the molecular analyses of 16S rRNA and dsrB genes. Among them, a strain named SRB49 exhibited the highest activity in removal of Sb(V). SRB49 was able to remove 95% of Sb(V) at a concentration of 100 mg/L within 48 h under optimum conditions: a temperature of 37-40 °C, an initial pH value of 8, 4 mM of sulfate, and an initial redox potential of 145-229 mV. SEM-EDX analysis showed that SRB49 did not adsorb Sb(V) but reduced and precipitated Sb(V) via the formation of Sb2S3. The results demonstrated the potential roles that pure cultures of SRB species may play in Sb removal and the use of Sb-tolerant SRB strains for Sb remediation.

Characterization and physicochemical aspects of novel cellulose-based layered double hydroxide nanocomposite for removal of antimony and fluoride from aqueous solution.

A series of novel adsorbents composed of cellulose (CL) with Ca/Al layered double hydroxide (CCxA; where x represent the Ca/Al molar ratio) were prepared for the adsorption of antimony (Sb(V)) and fluoride (F-) ions from aqueous solutions. The CCxA was characterized by Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), elemental analysis (CHNS/O), thermogravimetric analysis (TGA-DTA), zeta potential, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis. The effects of varying parameters such as dose, pH, contact time, temperature and initial concentration on the adsorption process were investigated. According to the obtained results, the adsorption processes were described by a pseudo-second-order kinetic model. Langmuir adsorption isotherm model provided the best fit for the experimental data and was used to describe isotherm constants. The maximum adsorption capacity was found to be 77.2 and 63.1 mg/g for Sb(V) and F-, respectively by CC3A (experimental conditions: pH 5.5, time 60 min, dose 15 mg/10 mL, temperature 298 K). The CC3A nanocomposite was able to reduce the Sb(V) and F- ions concentration in synthetic solution to lower than 6 µg/L and 1.5 mg/L, respectively, which are maximum contaminant levels of these elements in drinking water according to WHO guidelines.

Efficient antimony removal by self-assembled core-shell nanocomposite of Co3O4@rGO and the analysis of its adsorption mechanism.

Co3O4@rGO were facilely prepared by template free self-assemble in this study. The morphology of Co3O4@rGO was actiniaria-like core-shell structural nanocomposites. The formation mechanism of Co3O4@rGO core-shell nanocomposite was discussed according to its significant time-dependent morphology evolution course. To evaluate the application potential of Co3O4@rGO, its adsorption performance toward highly toxic antimony ions were studied. The Co3O4@rGO nanocomposite exhibit high anti-interference ability and high adsorption ability. The maximum adsorption capacities towards Sb(III) and Sb(V) are 151.04 and 165.51 mg/g, respectively. River water samples containing antimony violating the limit were used to evaluate the practical application of Co3O4@rGO, and high performance was achieved. The EU and China limits for antimony in drinking water can be met by using mesoporous Co3O4@rGO treating the actual river water samples with original antimony concentration lower than 50 µg/L. Adsorption isotherm, adsorption kinetics, pH and co-existing ions effects were also studied in details. The results indicate that mesoporous Co3O4@rGO is an excellent adsorbent for antimony removal. Mesoporous Co3O4@rGO nanocomposite is a potential candidate for antimony removal from waste water.

Effect of Water Chemistry on Antimony Removal by Chemical Coagulation: Implications of ζ-Potential and Size of Precipitates.

The process of coagulation and precipitation affect the fate and mobility of antimony (Sb) species in drinking water. Moreover, the solubility and physico-chemical properties of the precipitates may be affected by the media chemistry. Accordingly, the present study aimed to investigate the removal of Sb(III, V) species by ferric chloride coagulation under various water chemistry influences with a particular focus on the role of the properties of the precipitates. The results indicated that the amount of Sb(III) removed increased with increasing solution pH, showing the insignificant effects of the hydrodynamic diameter (HDD) and ζ-potential of the precipitates. However, no Sb(V) removal occurred at alkaline pH values, while a highly negative ζ-potential and the complete dissolution of precipitates were observed in the aqueous solution. The solution pH was also useful in determining the dominant coagulation mechanisms, such as co-precipitation and adsorption. The Fe solubility substantially affects the Sb removal at a certain pH range, while the HDD of the precipitates plays an insignificant role in Sb removal. The presence of divalent cations brings the ζ-potential of the precipitates close to point of zero charge (pzc), thus enhancing the Sb(V) removal at alkaline pH conditions. Pronounced adverse effects of humic acid were observed on Sb removal, ζ-potential and HDD of the precipitates. In general, this study may provide critical information to a wide group of researchers dealing with environmental protection from heavy metal pollution.

Facile synthesis of Bi3O(OH)(AsO4)2 and simultaneous photocatalytic oxidation and adsorption of Sb(III) from wastewater.

Antimony (Sb) decontamination in water is necessary owing to the worsening pollution which seriously threatens human life safety. Designing bismuth-based photocatalysts with hydroxyls have attracted growing interest because of the broad bandgap and enhanced separation efficiency of photogenerated electron/hole pairs. Until now, the available photocatalysis information regarding bismuth-based photocatalysts with hydroxyls has remained scarce and the contemporary report has been largely limited to Bi3O(OH)(PO4)2 (BOHP). Herein, Bi3O(OH)(AsO4)2 (BOHAs), a novel ultraviolet photocatalyst, was fabricated via the co-precipitation method for the first time, and developed to simultaneous photocatalytic oxidation and adsorption of Sb(III). The rate constant of Sb(III) removal by the BOHAs was 32.4, 3.0, and 4.3 times higher than those of BiAsO4, BOHP, and TiO2, respectively, indicating that the introduction of hydroxyls could increase the removal of Sb(III). Additionally, the crucial operational parameters affecting the adsorption performance (catalyst dosage, concentration, pH, and common anions) were investigated. The BOHAs maintained 85% antimony decontamination of the initial yield after five successive cycles of photocatalysis. The Sb(III) removal involved photocatalytic oxidation of adsorbed Sb(III) and subsequent adsorption of the yielded Sb(V). With the acquired knowledge, we successfully applied the photocatalyst for antimony removal from industrial wastewater. In addition, BOHAs could also be powerful photocatalysts in the photodegradation of organic pollutants studies of which are ongoing. It reveals an effective strategy for synthesizing bismuth-based photocatalysts with hydroxyls and enhancing pollutants' decontamination.

Separable alginate gel spheres encapsulated with La-Fe modified biochar for efficient adsorption of Sb(III) with high capacity.

Sb and its compounds have been widely used in various industrial applications. Therefore, the preparation of Sb adsorbents with easy recovery and excellent adsorption levels is an urgent problem that must be resolved. By calcining and treating La/Fe metal-organic frameworks (MOF) biochar as a precursor, a loaded La-Fe-modified water hyacinth biochar was synthesised and used as a filler to synthesise iron alginate composite gel spheres, MBC/algFe. Through a series of static adsorption experiments, the effects of different filler addition ratios, solution pH, reaction time, coexisting ions, and other factors on the adsorption of Sb(III) were investigated. According to the Langmuir model, the maximum adsorption capacity of MBC/algFe at 25 â„ƒ was 277.8 mg·g-1. The adsorption mechanism mainly involved hydrogen bonding and metal-organic complexation interactions.

MIL-101(Fe) based biomass as permeable reactive barrier applied to EK-PRB remediation of antimony contaminated soil.

Numerous studies have demonstrated that electrokinetic-permeable reactive barrier (EK-PRB) can be used for the remediation of heavy metal contaminated soils, and their remediation efficiency is mainly determined by the filler material selected. By growing MIL-101(Fe) in situ on hollow loofah fiber (HLF), a novel material entitled HLF@MIL-101(Fe) was developed. The morphological characteristics and loading conditions were investigated, the adsorption characteristics were analyzed, and finally the synthesized composite material was applied to treat antimony-contaminated soil with EK-PRB as the reaction medium. The results show that MIL-101(Fe) is stably loaded on HLF. The adsorption capacity of Sb(III) can reach up to 82.31 mg g-1, and the adsorption is in accordance with the quasi-secondary kinetic model, which indicates that chemisorption is dominant. The isothermal adsorption model indicates that the adsorption form of HLF@MIL-101(Fe) is mainly monolayer adsorption with more uniform adsorption binding energy. In the EK-PRB experiment, when ethylenediaminetetraacetic acid (EDTA) is used as the cathodic electrolyte, it can effectively enhance the electromigration and electroosmotic effects, and the overall remediation efficiency of the soil is increased by 38.12% compared with the citric acid (CA) group. These demonstrate the feasibility of HLF@MIL-101(Fe) in collaboration with EK-PRB in the treatment of antimony-contaminated soil.

Graphene oxide supported sulfidated nano zero-valent iron (S-nZVI@GO) for antimony removal: The role of active oxygen species and reaction mechanism.

Sulfidated nano zero-valent iron (S-nZVI) was used to remove various pollutants from wastewater. However, the instability, poor dispersibility, and low electron transfer efficiency of S-nZVI limit its application. Herein, graphene oxide supported sulfidated nano zero-valent iron (S-nZVI@GO) was successfully synthesized using graphene oxide (GO) as a carrier. The properties of S-nZVI@GO were characterized by scanning electron microscopy coupled to X-ray photoelectron spectroscopy (SEM-EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) concerning the surface morphology, crystalline structure, and elemental components. S-nZVI@GO displayed an excellent capacity for antimony (Sb) removal under aerobic conditions (96.7%), with a high adsorption capacity (Qmax = 311.75 mg/g). It maintained a high removal rate (over 90%) during a wide pH range (3-9). More importantly, S-nZVI@GO activated the molecular oxygen in water via a single-electron pathway to produce •O2－ and H2O2, and then oxidized trivalent antimony (Sb(III)) to pentavalent antimony (Sb(V)) and further separated it by synergistic adsorption and co-precipitation. Therefore, S-nZVI@GO shows excellent potential for Sb contamination remediation.

Factors affecting antimonate bioreduction by Dechloromonas sp. AR-2 and Propionivibrio sp. AR-3.

The microbial reduction of antimonate (Sb(v)) to antimonite (Sb(iii)), which forms insoluble Sb compounds, is a promising approach to remove antimony (Sb) from wastewater. Among the bacterial strains capable of reducing Sb(v) via anaerobic respiration that have been isolated to date, Dechloromonas sp. AR-2 and Propionivibrio sp. AR-3 are promising agents because they can grow aerobically and reduce Sb(v) under both anaerobic and microaerobic conditions. In this study, the effects of temperature, pH, electron donors, and coexisting electron acceptors on Sb(v) reduction and Sb removal by strains AR-2 and AR-3 were investigated to assess the usefulness of the strains in practical Sb treatment scenarios. Efficient Sb(v) reduction and removal by the two strains occurred over a relatively wide temperature range (15-35 °C) and neutral pH (6-7). In contrast, the carbon sources usable by these strains as electron donors for Sb respiration were limited to simple fatty acids such as acetate and lactate. Although strain AR-2 used nitrate and AR-3 used nitrate and arsenate as electron acceptors for anaerobic respiration in addition to Sb(v), the co-presence of other electron acceptors did not inhibit Sb(v) reduction. These results suggest that strains AR-2 and AR-3 can be potentially used in the practical treatment of Sb(v)-containing wastewater. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02703-0.

Microbial antimonate reduction and removal potentials in river sediments.

Antimony (Sb), a toxic metalloid, exists mainly as Sb(V) and Sb(III) in the aquatic environment. Sb(V) displays greater solubility and can be reduced to insoluble Sb(III) compounds by microbial activities under anaerobic conditions, thus affecting the environmental fate of Sb. This study was conducted to evaluate the potential of Sb(V) reduction and removal from the aqueous phase by microbial communities existing in river sediments with and without the impact of Sb mining activities. Among the 14 tested sediment samples, which were collected from an urban river without Sb impact and a river flowing through mining area, microbial communities in two samples could reduce and remove Sb(V) in the presence of high concentrations of sulfate, whereas those in other six samples could reduce Sb(V) even under low sulfate concentrations, indicating the relatively wide distribution of microbial Sb(V) reduction potential in the environment, irrespective of the anthropogenic impact. The Sb(V) reduction and removal abilities under different sulfate levels also suggested the presence of multiple types of Sb(V) reduction and removal pathways, including the direct Sb(V) reduction by anaerobic respiration, indirect (chemical) Sb(V) reduction by sulfide produced by microbial sulfate reduction, and their combination. Furthermore, analysis of microbial communities in two enrichment cultures, which were constructed from sediment samples with Sb(V) reduction ability under the minimum sulfate condition and maintained Sb(V) removal ability during 28-d enrichment process, revealed possible contribution of several microbial taxa such as Azospira, Chlostridium, Dechloromonas, Dendrosporobacter, and Halodesulfovibrio to Sb(V) reduction in sediment microbial communities.

Enhanced removal of antimony in dyeing wastewater by mixing Fe3 O4 with manganese sand filter material.

Wastewaters from the printing and dyeing industries contain many contaminants in particular antimony (Sb) that end up in the environment. Both manganese sand filter and Fe3 O4 have good removal effect on Sb, and are cheap and easy to obtain. We made a filter material by mechanically mixing the manganese sand filter material and ferro-ferric oxide (Fe3 O4 ). The Fe-Mn oxide filter material was analyzed by X-ray diffraction. We studied the filtration of real wastewater from a dyeing wastewater resource recovery facility in Suzhou, China, containing Sb at high concentration of 410 µg/L, using dynamic tests in adsorption columns during 7 days. We tested the effects of filter material volume filling ratio, the empty bed contact time (EBCT), pH, and back washing on the removal of Sb. Results show that the addition of Fe3 O4 enhanced the removal of Sb, reaching 85% of initial Sb. When the initial influent pH of the raw water is 3.0, the volume filling ratio of filter material is 60%, the EBCT is 20 min, and the developed dynamic Fe-Mn oxide filter has the best removal effect on Sb. Daily back washing of the filter keeps a Sb removal rate of about 80%. PRACTITIONER POINTS: A novel and cheap Fe-Mn oxide was developed for Sb removal from dyeing wastewater. A self-designed filter device was designed to verify performance of the low-cost material. Optimal design and operational parameters of the filtration process were determined.

Antimony Removal from Water by a Chitosan-Iron(III)[ChiFer(III)] Biocomposite.

The presence of antimony(III) in water represents a worldwide concern, mainly due to its high toxicity and carcinogenicity potential. It can be separated from water by the use of sustainable biopolymers such as chitosan or its derivatives. The present study applied chitosan modified with iron(III) beads to Sb(III) removal from aqueous solutions. The resulting material performed with a high adsorption capacity of 98.68 mg/g. Material characterization consisted of Raman spectroscopy (RS), X-ray diffraction (XRD), scanning electron microscope observations (SEM-EDX), Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pHpzc). The adsorption study included pH study, effect of initial concentration, kinetics, ion effect, and reusability assessment. The RS, XRD, and FTIR results indicated that the main functional groups in the composite were related to hydroxyl and amino groups, and iron oxyhydroxide species of α-FeO(OH). The pHpzc was found to be 7.41. The best adsorption efficiency was set at pH 6. The equilibrium isotherms were better fitted with a non-linear Langmuir model, and the kinetics data were fitted with a pseudo-second order rate equation. The incorporation of iron into the chitosan matrix improved the Sb(III) uptake by 47.9%, compared with neat chitosan (CS). The material did not exhibit an impact in its performance in the presence of other ions, and it could be reused for up to three adsorption⁻desorption cycles.

Coagulation removal of Sb(V) from textile wastewater matrix with enhanced strategy: Comparison study and mechanism analysis.

The wide use of antimony in textile industry has posed threat to ecological health and attracted increased attention. The objective of this work was to develop enhanced coagulation strategies including PFS/FeSO4 and aerated PFS/FeSO4 for efficient antimony elimination from textile wastewater matrix. With a dosage of 0.75 mM Fe, aerated PFS/FeSO4 coagulation could achieve 82.6% removal of 500 µg L-1 Sb(V) from simulated textile wastewater, which was better than PFS (77.6%) and PFS/FeSO4 coagulation (79.9%). Compared with PFS and PFS/FeSO4 coagulation, aerated PFS/FeSO4 strategy could meet the indirect discharge standard (<100 µg L-1), without any other additional treatment. pH ranged from 5 to 6 could reach 93.8% Sb(V) removal, by affecting coagulant hydrolysis and charges on flocs. Phosphate ion with a level more than 0.03 mM could compete with Sb(V) species and thus reduced its removal. Temperature of 35 °C could lead to enhanced Sb(V) removal by accelerating coagulant hydrolysis. Flocs of aerated PFS/FeSO4 had smaller average size than that of PFS and PFS/FeSO4 coagulation. FeOOH was the hydrolysis product of aerated PFS/FeSO4 strategy. Adsorption, rather than direct and co-precipitation was predominant in the coagulation mechanism. From the phosphate extraction test, 64% of the Sb could form inner-sphere surface complex during aerated PFS/FeSO4 coagulation removal.