Selective recovery of metals in spent batteries by electrochemical precipitation to cathode material for sodium-ion batteries.

The recycling of key components in waste lithium-ion batteries (LIBs) is an important route to make up for the shortage of battery materials. Metal separation and purification is an important step. It is of great significance to propose an efficient and green separation technology. In this paper, an electrochemical precipitation method was applied to metal separation from spent LiNi0.5Mn1.5O4 cathode material. The Li and metal elements were effective separated and the precipitates were then used as precursor to synthesize high-performance R-O3-NaNFM cathode material for sodium-ion batteries. The R-O3-NaNFM exhibits excellent electrochemical cycling stability. The capacity retains 71.3 mAh g-1 after a long-term cycling of 200 times at 1 C. This method offers a referable strategy of the recycling for the waste cathode material in spent LIBs.

Measurement artifacts in the dithiothreitol (DTT) oxidative potential assay caused by interactions between aqueous metals and phosphate buffer.

Metals in particulate matter (PM) are hypothesized to have enhanced toxicity based on their ability to catalyze reactive oxygen species (ROS) formation. Acellular assays are used to measure the oxidative potential (OP) of PM and its individual components. Many OP assays, including the dithiothreitol (DTT) assay, use a phosphate buffer matrix to simulate biological conditions (pH 7.4 and 37 °C). Prior work from our group observed transition metal precipitation in the DTT assay, consistent with thermodynamic equilibria. In this study, we characterized the effects of metal precipitation on OP measured by the DTT assay. Metal precipitation was affected by aqueous metal concentrations, ionic strength, and phosphate concentrations in ambient PM sampled in Baltimore, MD and a standard PM sample (NIST SRM-1648a, Urban Particulate Matter). Critically, differences in metal precipitation induced differing OP responses of the DTT assay as a function of phosphate concentration in all PM samples analyzed. These results indicate that comparison of DTT assay results obtained at differing phosphate buffer concentrations is highly problematic. Further, these results have implications for other chemical and biological assays that use phosphate buffer for pH control and their use to infer PM toxicity.

Role of the substrate on Ni inhibition in biological sulfate reduction.

In treating mine-impacted waters using sulfate-reducing bacteria (SRB), metal inhibition and substrate selection are important factors affecting the efficiency of the bioprocess. This work investigated the role of the substrate (i.e. lactate, formate, glycerol and glucose) on Ni inhibition to SRB with sulfate-reducing activity tests at initial pH 5, 7 and 9 and 100 mg/L of Ni. Results indicated that the type of substrate was a significant factor affecting Ni inhibition in SRB, which was the most negligible in the lactate system, followed by glycerol, glucose, and formate. Although less significant, Ni inhibition also varied with the pH, leading for instance, to a reduction of 77% in the sulfate reducing activity for the formate system, but only of 28% for lactate at pH 5. The added substrate also influenced the precipitation kinetics and the characteristics of the precipitates, reaching Ni precipitation extents above 95%, except for glucose (83.2%).

Removal of multiple heavy metals from mining-impacted water by biochar-filled constructed wetlands: Adsorption and biotic removal routes.

Granular biochar made from walnut shells was layered into sand-based constructed wetlands (CWs) to treat simulated mining-impacted water (MIW). The results showed that the biochar media exhibited markedly high capacities for metal binding and acidity neutralization, supported notably better plant growth and mitigated metal transfer from the plant roots to the shoots. The addition of organic liquid wastes (domestic sewage and plant straw hydrolysation broth) stimulated biogenic sulfate reduction after 40 d of adaptation to effectively remove multiple heavy metals in the MIW. The microbial community compositions were prominently regulated by organic carbon, with desirable communities dominated by Cellulomonas and Desulfobulbus formed in the CWs for MIW biotreatment. The role of macrophytes in the CWs in MIW treatment was insignificant and was dependent on operation conditions and metal species. A biochar-packed CW system with liquid organic waste supplementation was effective in metal removal and acidity neutralization of MIW.

Sulfate and metal removal from acid mine drainage using sugarcane vinasse as electron donor: Performance and microbial community of the down-flow structured-bed bioreactor.

The down flow structured bed bioreactor (DFSBR) was applied to treat synthetic acid mine drainage (AMD) to reduce sulfate, increase the pH and precipitate metals in solutions (Co, Cu, Fe, Mn, Ni and Zn) using vinasse as an electron donor for sulfate-reducing bacteria (SRB). DFSBR achieved sulfate removal efficiencies between 55 and 91%, removal of Co and Ni were obtained with efficiencies greater than 80%, while Fe, Zn, Cu and Mn were removed with average efficiencies of 70, 80, 73 and 60%, respectively. Sulfate reduction increased pH from moderately acidic to 6.7-7.5. Modelling data confirmed the experimental results and metal sulfide precipitation was the mainly responsible for metal removal. The main genera responsible for sulfate and metal reduction were Geobacter and Desulfovibrio while fermenters were Parabacteroides and Sulfurovum. Moreover, in syntrophism with SRB, they played an important role in the efficiency of metal and sulfate removal.

Sulfate removal rate and metal recovery as settling precipitates in bioreactors: Influence of electron donors.

Four down-flow structured bed bioreactors were operated targeting biological sulfate-reduction and metal recovery. Three different electron donors were tested: glycerol (R1), lactate (R2), sucrose (R3), and a blend of the previous three (R4) with an increasing copper influent load (5, 15, and 30 mg Cu2+.L-1). Copper inhibited sulfate-reduction in R1 (15 mg Cu2+.L-1) and R3 (5 mg Cu2+.L-1), but the fermentative activity was not affected. R2 and R4 were not inhibited by the copper influent concentration. R2 provided the highest sulfate reduction rate (1767.3 ± 240.1 mg SO42-.L.day-1). Nonetheless, the accumulation of settling precipitates was 22 % higher in R4 than in R2, indicating the former yielded the highest metal recovery as settling precipitates (24.8 g FSS.L-1, 25 % Fe2+, 5% Cu2+). 16S rRNA sequencing showed highest diversity of sulfate-reducing bacteria in R2. A predominance of sulfate-reducing and fermentative bacteria with more similarity was observed between microbial populations in R1 and R4, despite the difference in toxicity thresholds. Hence, the electron donor influenced not only the biological sulfate reduction, but also metal toxicity thresholds and metal recovery as settling precipitates.

Effect of speciation and composition on the kinetics and precipitation of arsenic sulfide from industrial metallurgical wastewater.

Precipitation of arsenic as As2S3 produces little waste sludge, has the potential for low chemical consumption and for selective metal(loid) removal. In this study, arsenic removal from acidic (pH 2), metallurgical wastewater was tested in industrially relevant conditions. Sulfides added at a S:As molar ratio of 2.5 and 5 resulted in removal of 99% and 84% of As(III) and As(V). Precipitation of As2S3 from the As(III) and industrial wastewater containing 17% As(V) was nearly instantaneous. For the synthetic As(V) solution, reduction to As(III) was the rate limiting step. At a S:As ratio of 20 and an observed removal rate (k2 = 4.8 (mol L-1) h-1), two hours were required to remove of 93% of arsenic from a 1 g As L-1 solution. In the case of As(V) in industrial samples this time lag was not observed, showing that components in the industrial wastewater affected the removal and reduction of arsenate. Speciation also affected flocculation and coagulation characteristics of As2S3 particles: As(V) reduction resulted in poor coagulation and flocculation. Selective precipitation of arsenic was possible, but depended on speciation, S:As ratio and other metals present.

Promotion of bioremediation performance in constructed wetland microcosms for acid mine drainage treatment by using organic substrates and supplementing domestic wastewater and plant litter broth.

Gravel-based subsurface-flow constructed wetlands (CWs) amended with a walnut shell (WS) substrate were established to treat synthetic acid mine drainage (AMD) in this study, and artificial domestic wastewater (DW) and plant litter broth (PLB) were supplemented to enhance the performance. The CW media rapidly reached adsorption saturation with respect to metals (except Fe and Cr) without an external carbon source, while the addition of DW and PLB stimulated sulfate reduction activity and achieved efficient biogenic metal removal, primarily by the formation of hydroxide and sulfide precipitates and concomitant co-precipitation. The WS-amended CWs performed notably better than the control systems, not only in sequestering more metals and rapidly establishing favourable environments for biogenic metal abatement but also in supporting better growth of plants and functional microbes. The external organic carbon input greatly shaped the bacterial community compositions in the CWs, with substantial increases in the proportions of core functional populations involved in AMD biotreatment. Cooperation among Cellulomonas, Propioniciclava and sulfate-reducing bacteria (SRB), dominated by Desulfobulbus and Desulfatirhabdium, was the primary biogenic mechanism of AMD remediation in the CWs. Cellulosic waste-amended CWs with DW and PLB addition offer a promising eco-technology for AMD remediation.

Reactores Bioquímicos Pasivos: Una alternativa biotecnológica para la remediación de drenajes ácidos de mina / Biochemical passive reactors: a biotechnological alternative to remediation of acid mine drainage

RESUMEN El Drenaje ácido de mina (DAM) es actualmente el principal contaminante de las regiones mineras. Los reactores bioquímicos pasivos son una tecnología sostenible fácil de instalar que utiliza desechos agroindustriales de la región y puede operar en áreas remotas con poco mantenimiento. Además, son una tecnología limpia que involucra bioprocesos, reacciones químicas y precipitación de metales, minimizando el impacto de los vertimientos ácidos sobre suelos y cuerpos de aguas. Los reactores bioquímicos pasivos son columnas empacadas con una "mezcla reactiva" conformada por materiales orgánicos, inorgánicos y un inóculo microbiano. En esta mezcla se remedia el DAM por medio de procesos fisicoquímicos como la adsorción, precipitación, coprecipitación de los metales y de la reducción del sulfato a sulfuro, mientras se incrementa el pH y la alcalinidad. Con el fin de brindar información reciente, así como las necesidades de investigación en el tema, este documento presenta una revisión de literatura sobre la generación química y biológica de los DAM, así como su remedición utilizando reactores bioquímicos pasivos. El conocimiento de los conceptos básicos de estos procesos es extremadamente útil para evaluar las posibles aplicaciones, beneficios y limitaciones de estos sistemas de tratamiento utilizados por la biotecnología durante la biorremediación de efluentes mineros.

ABSTRACT Acid Mine Drainage (AMD) is currently the main pollutant in mining areas. Passive biochemical reactors are a sustainable technology easy to install using agro-industry waste from the mining region and operating in remote locations. Besides, bioreactors are clean technology that involves bioprocesses, chemical reactions, and metal precipitation, minimizing the impact of AMD on soils and fresh water sources. The passive biochemical reactors are columns packed with a "reactive mixture" consisting of organic, inorganic materials and a microbial inoculum. In this reactive mixture, AMD is remediated through physicochemical processes such as metals adsorption, precipitation, and co-precipitation, as well as, the reduction of sulfate to sulfur, while pH and alkalinity are in-creased. To provide recent information and research needs in the subject, this document presents a review of the literature about the chemical and biological generation of AMD and its remediation using passive biochemical reactors. The knowledge of the basic concepts of these processes is extremely useful to evaluate the possible applications, benefits and limitations of these treatment systems used by biotechnology during the bioremediation of mining effluents.

Long Chain Fatty Acid Degradation Coupled to Biological Sulfidogenesis: A Prospect for Enhanced Metal Recovery.

This research assessed the microbiological suitability of oleate degradation coupled to sulfidogenesis by enriching communities from anaerobic sludge treating dairy products with S0, SO 3 2 - , SO 4 2 - , and S2 O 3 2 - as electron acceptors. The limiting factor hampering highly efficient oleate degradation was investigated in batch reactors. The best sulfidogenic performance coupled to specialization of the enriched bacterial community was obtained for S0- and S2 O 3 2 - -reducing enrichments, with 15.6 (± 0.2) and 9.0 (± 0.0) mM of sulfide production, respectively. Microbial community analyses revealed predominance of Enterobacteraceae (50.6 ± 5.7%), Sulfurospirillum (23.1 ± 0.1%), Bacteroides (7.5 ± 1.5%) and Seleniivibrio (6.9 ± 1.1%) in S0-reducing cultures. In S2 O 3 2 - -reducing enrichments, the genus Desulfurella predominated (49.2 ± 1.2%), followed by the Enterobacterales order (20.9 ± 2.3%). S0-reducing cultures were not affected by oleate concentrations up to 5 mM, while S2 O 3 2 - -reducing cultures could degrade oleate in concentrations up to 10 mM, with no significant impact on sulfidogenesis. In sequencing batch reactors operated with sulfide stripping, the S0-reducing enrichment produced 145.8 mM sulfide, precipitating Zn as ZnS in a separate tank. The S2 O 3 2 - fed bioreactor only produced 23.4 mM of sulfide precipitated as ZnS. The lower sulfide production likely happened due to sulfite toxicity, an intermediate of thiosulfate reduction. Therefore, elemental sulfur reduction represents an excellent alternative to the currently adopted approaches for LCFA degradation. To the best of our knowledge, this is the first report of oleate degradation with the flux of electrons totally diverted toward sulfide production for metal precipitation, showing great efficiency of LCFA degradation coupled to high levels of metals precipitated as metal sulfide.

Remediation by waste marble powder and lime of jarosite-rich sediments from Portman Bay (Spain).

We investigate the use of hydrated lime and calcite waste marble powder as remediation treatments of contaminated jarosite-rich sediments from Portman Bay (SE, Spain), one of the most contaminated points in the Mediterranean coast by mining-metallurgical activities. We tested two commercial hydrated limes with different Ca(OH)2 percentages (28 and 60% for Lime-1 and Lime-2 respectively) and two different waste marble powder, WMP, from the marble industry (60 and 96% of calcite for WMP-1 and WMP-2 respectively). Mixture and column experiments and modelling of geochemical reactions using PHREEQC were performed. Lime caused the precipitation of hematite, gypsum and calcite, whereas WMP treatments formed iron carbonates and hematite. The fraction of amorphous phases was mainly composed of iron oxides, hydroxides and oxyhydroxides that was notably higher in the lime treatment in comparison to the WMP treatment. The reactive surface area showed a positive trend with the amorphous phase concentration. Results highlighted the effectiveness of lime treatments, where Lime-2 showed a complete elimination of jarosite. Column experiments revealed a clear reduction of heavy metal concentration in the lixiviate for the treated sediments compared to the original sediments. Particularly, Lime-2 showed the highest reduction in the peak concentration of Fe, Mn, Zn and Cd. The studied treatments limited the stabilisation of Cr and Ni, whereas contrarily As increases in the treated sediment. PHREEQC calculations showed that the most concentrated heavy metals (Zn and Mn) are stabilized mainly by precipitation whereas Cu, Pb and Cd by a combination of precipitation and sorption processes. This chemical environment leads to the precipitation of stable iron phases, which sorb and co-precipitate considerable amounts of potentially toxic elements. Lime is significantly more effective than WMP, although it is recommended that the pH value of the mixture should remain below 9 due to the amphoteric behaviour of heavy metals.

Thiosulfate as the electron acceptor in Sulfur Bioconversion-Associated Process (SBAP) for sewage treatment.

The sulfur bioconversion-associated processes (SBAP) for sewage treatment have been extensively reported so far. In this study, biological thiosulfate reduction (BTR)-driven biotechnology for high rate sulfidogenesis and organic removal was explored to further close the gap of our knowledge on the sulfur cycle-based sewage treatment bioprocess. With thiosulfate as the electron acceptor, the sulfidogenic rate in the UASB rector is 105.6 mg S/L/h with the sludge yield of only 0.044 g MLVSS/g CODsubstrate. Thus providing sufficient electron donors or chemical sources (i.e. HS-) for the downstream autotrophic denitrification or for the cost-effective heavy metal precipitation. Thiosulfate disproportionation was not observed in BTR reactor. High-throughput pyrosequencing analysis reveals that Desulfobulbus and Desulfomicrobium are the predominant thiosulfate-reducing genera and the thiosulfate disproportionation-bacteria were at much lower genus level. The specific thiosulfate-reducer i.e. Dethiosulfatibacter which could utilize thiosulfate but not sulfate as the electron acceptor was also identified. Batch testing results indicate that the sulfidogenic activity on thiosulfate was 1.5 times that on sulfate. The optimal pH for BTR activity was between 7.0 and 8.0, a typical pH range of the municipal sewage. Thiosulfate can be efficiently recovered in the sulfide-driven denitritation reactor enriched with abundant sulfide-oxidizing genera (mainly including Thiobacillus and Sulfurimonas). Finally, a conceptual model of the sulfur cycle based on the biotransformation between thiosulfate and sulfide was established, offering new insights into the sustainable SBAP with sludge minimization.

Spent MgO-carbon refractory bricks as a material for permeable reactive barriers to treat a nickel- and cobalt-contaminated groundwater.

Spent magnesia (MgO)-carbon refractory bricks were repurposed as a permeable reactive barrier reactive media to treat a nickel (5 mg l-1)- and cobalt (0.3 mg l-1)-contaminated groundwater. MgO has been used for decades as a heavy metal precipitating agent as it hydrates and buffers the pH in a range of 8.5-10 associated with the minimum solubility of various divalent metals. The contaminated groundwater site's conditions are typical of contaminated neutral drainage with a pH of 6 as well as high concentrations of iron (220 mg l-1) and sulphates (2500 mg l-1). Using synthetic contaminated water, batch and small-scale column tests were performed to determine the treatment efficiency and longevity. The increase and stabilization of the pH at 10 observed during the tests are associated with the hydration and dissolution of the MgO and promoted the removal not only of a significant proportion of the contaminants but also of iron. During the column test, this accumulation of precipitates over time clogged and passivated the MgO resulting in a loss of chemical performance (pH lowering, metal breakthrough) after 210 pore volumes of filtration. Precipitation also affected the hydraulic conductivity values which dropped from 2.3·10-3 to 4.2·10-4 m s-1 at the end of test. Saturation indices and XRD analyses suggest the precipitates formed are likely composed of goethite as well as iron, cobalt and nickel hydroxides. Recycled MgO-C refractory bricks were demonstrated to be an efficient reactive material for the removal of Co and Ni, but careful considerations should be taken of the potential clogging and passivation phenomena given particular physicochemical conditions.

Removal of sulfate and heavy metals by sulfate-reducing bacteria in an expanded granular sludge bed reactor.

The objective of this study is to utilize an expanded granular sludge bed reactor for removing heavy metals and sulfate from synthetic acid-mine drainage (AMD) using sewage sludge fermentation centrate as the substrate. The reactor was bioaugmented with an enriched consortium of sulfate-reducing bacteria (SRB). The bioreactor performance was studied with different chemical oxygen demand [Formula: see text] ratios, liquid upflow velocity (Vup), hydraulic retention time (HRT) and influent pH. The highest COD, sulfate and heavy metal removal efficiencies were achieved at a [Formula: see text] ratio of 1.5, Vup of 4.0 m/h, HRT of 15 h and influent pH of 6.0 (68.2%, 92.1% and 100%, respectively). The activity of SRB greatly increases the effluent pH. Even at an influent pH of 3.0, 60.8% of sulfate, 41.3% of COD and 91.2% of heavy metals could be removed, and the effluent quality can meet the national discharge standard of China. The activity tests demonstrate that the sludge fermentation centrate is an excellent carbon source for SRB. This study shows the potential of synchronous treatment of residual sewage sludge and treatment of AMD.

Prevención de drenajes ácidos de mina utilizando compost de champiñón como enmienda orgánica / Acid mine drainage prevention using mushroom compost as organic amendment

Resumen Los drenajes ácidos de mina (DAM) son vertimientos con bajo pH, alta concentración de metales y sulfato. Son considerados el mayor problema ambiental de la industria minera y prevenir su formación es la mejor alternativa ambiental y económica. En este estudio, se evaluó el compost de champiñón como enmienda de carbono orgánico para prevenir la formación de DAM. Se construyeron tres celdas en tubos de PVC (2,4 L), llenas con 300 g de mezcla de compost de champiñón y estéril de carbón en diferentes proporciones (40:60, 25:70, 60:40) y 400 mL de agua (18,5Ω). Los cambios químicos en el lixiviado, así como la actividad microbiana en las mezclas fueron monitoreados durante 6 semanas. En los lixiviados el oxígeno disuelto (< 2,0 mg L-1) y potencial de óxido reducción (< (100 mV) disminuyeron, mientras el pH (> 6,5) y la alcalinidad (> 1.500 mg CaCO3 L-1) incrementaron. Además, todas las mezclas fueron eficientes en precipitar los metales (Fe2+ > 95%; Mn2+ > 96%; Zn2+ > 52%) y remover sulfato (> 50%). Sin embargo, en la celda que contenía una proporción de compost y estéril de 25:75 se observó una producción significativa de sulfuro y una mayor actividad microbiana, indicando la presencia de bacterias sulfato-reductoras. Los resultados muestran que el compost de champiñón puede ser utilizado como enmienda orgánica de carbón para contrarrestar la formación de DAM y que la mezcla 25:75 puede ser una opción promisoria para usar en campo en el Distrito minero de Zipaquirá (Colombia).

Abstract The Acid mine drainage (AMD) are discharges characterized by low pH and high concentrations of sulfate and metals. AMD is considered as a serious problem of the mining industry and preventing its formation is the best environmental and economical option. Mushroom compost was evaluated as organic carbon amendment to promote sulfate reduction and metal sulfide precipitation during AMD formation. Three PVC cells (2.4 L) were filled with 300 g of the mixture of mushroom compost and coal mining waste in different proportions (40:60, 25:70, 60:40 %) and 400 mL of water (18,5 Ω). The chemical change in the leachates and the microbial activity in the mixtures were evaluated for 6 weeks. In leachates, dissolved oxygen (< 2,0 mg L-1) and redox potential (< (100 mV) decreased while pH (> 6,5) and alkalinity (> 1500 mg CaCO3 L-1) increased. Besides, all mixtures were efficient for metals precipitation (Fe2+ > 95%; Mn2+ > 96%; Zn2+ > 52%) and sulfate reduction (> 50%). However, a significant production of sulfide and a greater microbial activity was observed in the mixture of mushroom compost and coal mining waste 25:75, indicating the presence of sulfate-reducing bacteria. The results showed that mushroom compost could be used as organic carbon amendment to prevent AMD generation and that the mixture 25:75 could be a promising option to be used in Zipaquirá Mining District (Colombia).

A case in support of implementing innovative bio-processes in the metal mining industry.

The metal mining industry faces many large challenges in future years, among which is the increasing need to process low-grade ores as accessible higher grade ores become depleted. This is against a backdrop of increasing global demands for base and precious metals, and rare earth elements. Typically about 99% of solid material hauled to, and ground at, the land surface currently ends up as waste (rock dumps and mineral tailings). Exposure of these to air and water frequently leads to the formation of acidic, metal-contaminated run-off waters, referred to as acid mine drainage, which constitutes a severe threat to the environment. Formation of acid drainage is a natural phenomenon involving various species of lithotrophic (literally 'rock-eating') bacteria and archaea, which oxidize reduced forms of iron and/or sulfur. However, other microorganisms that reduce inorganic sulfur compounds can essentially reverse this process. These microorganisms can be applied on industrial scale to precipitate metals from industrial mineral leachates and acid mine drainage streams, resulting in a net improvement in metal recovery, while minimizing the amounts of leachable metals to the tailings storage dams. Here, we advocate that more extensive exploitation of microorganisms in metal mining operations could be an important way to green up the industry, reducing environmental risks and improving the efficiency and the economy of metal recovery.

Supported liquid membrane based removal of lead(II) and cadmium(II) from mixed feed: Conversion to solid waste by precipitation.

Simultaneous removal of two heavy metals, lead(II) and cadmium(II), from mixed feed using supported liquid membrane (SLM) based technique is investigated in this work. The carrier-solvent combination of "sodium salt of Di-2-ethylhexylphosphoric acid (D2EHPA) (4% w/w) in environmentally benign coconut oil" was immobilized into the pores of solid polymeric polyvinylidene fluoride (PVDF) support. Sodium carbonate (Na2CO3) was used as the stripping agent. Carbonate salts of lead(II) and cadmium(II) were formed in the stripping side interface and they were insoluble in water leading to precipitation inside the stripping solution. The transportation of solute is positively affected due to the precipitation. Lead(II) removal was found to be preferential due to its favorable electronic configuration. The conversion of the liquid waste to the solid one was added advantage for the final removal of hazardous heavy metals.