Closed-loop recycling of spent lithium-ion batteries based on selective sulfidation: An unconventional approach.

The facile recycling of spent lithium-ion batteries (LIBs) has attracted considerable attention because of its great importance to environmental protection and resource utilization. A novel process is developed for cyclic utilization of spent LiNixCoyMnzO2 (NCM) batteries. The spent NCM was converted into water-soluble Li2CO3, acid-dissolved MnO, and nickel-cobalt sulfides through selective sulfidation, based on roasting condition optimization and thermodynamic calculation. More than 98 % of lithium is extracted preferentially from calcined NCM through water leaching, and over 99 % of manganese is extracted selectively from water leaching residue with H2SO4 solution of 0.4 mol/L in the absence of additional reductant. The nickel and cobalt sulfides were concentrated into the leaching residue without metal impurities. The obtained Li2CO3, MnSO4, and nickel-cobalt sulfides can be regenerated as new NCM, showing good electrochemical performance, and its discharge capacity is 169.8 mAh/g at 0.2C. After 100 cycles at 0.2C, the discharge specific capacity can still be maintained at 143.24 mAh/g, and its capacity retention ratio is as high as 92  %. An environmental assessment and economic evaluation indicate that the process is an economical and eco-friendly approach for green recycling of spent LIBs.

Pristine and sulfidized zinc oxide nanoparticles alter bacterial communities and metabolite profiles in soybean rhizocompartments.

A better understanding of bacterial communities and metabolomic responses to pristine zinc oxide manufacture nanoparticles (ZnO MNPs) and its sulfidized product (s-ZnO MNPs), as well as their corresponding Zn ions in rhizocompartments, critical in the plant-microbe interactions, could contribute to the sustainable development of nano-enabled agriculture. In this study, soybean (Glycine max) were cultivated in soils amended with three Zn forms, namely ZnSO4·7H2O, ZnO MNPs and s-ZnO MNPs at 0, 100 and 500 mg·kg-1 for 70 days. Three Zn forms exposures profoundly decreased the bacterial alpha diversity in roots and nodules. High dose (500 mg·kg-1) groups had a stronger impact on the bacterial beta diversity than low dose (100 mg·kg-1) groups. In the rhizosphere soil and roots, 500 mg·kg-1 of ZnSO4 and s-ZnO MNPs treatments showed the largest shifts in bacterial community structure, respectively. In addition, several significant changed bacterial taxa and metabolites were found at the high dose groups, which were associated with carbon and nitrogen metabolism. PLS-DA plot showed good discrimination in metabolomic profiles of rhizosphere soil and roots between three Zn forms treatments and control. Most metabolic pathways perturbed were closely linked to oxidative stress. Overall, our study indicates either dissolved or nano-particulate Zn exposure at high dose can drastically affected bacterial communities and metabolite profiles in soybean rhizocompartments.

Design of cryogel based CNTs-anchored polyacrylonitrile honeycomb film with ultra-high S-NZVI incorporation for enhanced synergistic reduction of Cr(VI).

An ultra-high NZVI-loaded PAN film (S-CPN) with a unique 3D honeycomb structure was designed based on the cryogel method of green solvent-induced pores and confinement of the spatially free conformation of films by anchoring carbon nanotubes (CNTs), supplemented sulfidation for removing hexavalent chromium (Cr(VI)), and characterized by SEM, AFM, BET, XRD, XPS, and electrochemical corrosion. The doping amounts of the compounds for S-CPN synthesis were optimized to be 0.075 g CNTs, 0.25 g Na2S, and 0.3 M FeSO4. S-CPN possessed a 175.247 m2/g specific surface area, -0.365 V reduction potential, and 46.54 mg/g ultra-high NZVI-loading. S-CPN had the strong activity of Cr(VI) removal and tolerance to coexisting ions. The removal efficiency remained at 80 % after age for 30 days or 5 cycles. The pseudo-first-order kinetics and Langmuir model were more favorable to simulate the adsorption of Cr(VI) on S-CPN. The thermodynamics show that S-CPN removing Cr(VI) was a spontaneous exothermic reaction. The reasons for these excellent properties were that CNTs improve the film porosity and ultra-high NZVI-loading, and synergistic the FeSX layer to chelates-reduces Cr(VI). This was the first time that honeycomb film with 3D structure and potential applications in heavy metal removal was developed via an eco-friendly strategy.

Sulfidation and Reoxidation of U(VI)-Incorporated Goethite: Implications for U Retention during Sub-Surface Redox Cycling.

Over 60 years of nuclear activity have resulted in a global legacy of contaminated land and radioactive waste. Uranium (U) is a significant component of this legacy and is present in radioactive wastes and at many contaminated sites. U-incorporated iron (oxyhydr)oxides may provide a long-term barrier to U migration in the environment. However, reductive dissolution of iron (oxyhydr)oxides can occur on reaction with aqueous sulfide (sulfidation), a common environmental species, due to the microbial reduction of sulfate. In this work, U(VI)-goethite was initially reacted with aqueous sulfide, followed by a reoxidation reaction, to further understand the long-term fate of U species under fluctuating environmental conditions. Over the first day of sulfidation, a transient release of aqueous U was observed, likely due to intermediate uranyl(VI)-persulfide species. Despite this, overall U was retained in the solid phase, with the formation of nanocrystalline U(IV)O2 in the sulfidized system along with a persistent U(V) component. On reoxidation, U was associated with an iron (oxyhydr)oxide phase either as an adsorbed uranyl (approximately 65%) or an incorporated U (35%) species. These findings support the overarching concept of iron (oxyhydr)oxides acting as a barrier to U migration in the environment, even under fluctuating redox conditions.

Ball milling sulfur-doped nano zero-valent iron @biochar composite for the efficient removal of phosphorus from water: Performance and mechanisms.

This study successfully prepared a novel sulfur-doped nano zero-valent iron @biochar (BM-SnZVI@BC) by modifying corn stover biochar with Fe0 and S0 using a mechanical ball milling method for effective phosphorus (P) adsorption in the waterbody. Batch experiments revealed that BM-SnZVI@BC (BC/S0/Fe0 = 3:1:1) reached a Qmax of 25.00 mg P/g and followed PFO and Langmuir models. This work had shown that electrostatic attraction, surface chemical precipitation, hydrogen bonding, and ligand effects all contributed to P removal. Since the FeS layer mitigated the oxidation-induced surface passivation of nZVI, sulfidation significantly extended the lifetime of BM-SnZVI@BC, removing 84.4% of P even after 60 d aging in air. The regeneration experiments of composites showed that re-ball milling destroyed the surface iron oxide layer to improve the properties of the recovered material. This is an essential step in the design of P-removal agents to implement anti-aging and commercialization of adsorbents for engineering applications.

Sulfidation of magnetite with incorporated uranium.

Uranium (U) is a radionuclide of key environmental interest due its abundance by mass within radioactive waste and presence in contaminated land scenarios. Ubiquitously present iron (oxyhydr)oxide mineral phases, such as (nano)magnetite, have been identified as candidates for immobilisation of U via incorporation into the mineral structure. Studies of how biogeochemical processes, such as sulfidation from the presence of sulfate-reducing bacteria, may affect iron (oxyhydr)oxides and impact radionuclide mobility are important in order to underpin geological disposal of radioactive waste and manage radioactively contaminated land. Here, this study utilised a highly controlled abiotic method for sulfidation of U(V) incorporated into nanomagnetite to determine the fate and speciation of U. Upon sulfidation, transient release of U into solution occurred (∼8.6% total U) for up to 3 days, despite the highly reducing conditions. As the system evolved, lepidocrocite was observed to form over a period of days to weeks. After 10 months, XAS and geochemical data showed all U was partitioned to the solid phase, as both nanoparticulate uraninite (U(IV)O2) and a percentage of retained U(V). Further EXAFS analysis showed incorporation of the residual U(V) fraction into an iron (oxyhydr)oxide mineral phase, likely nanomagnetite or lepidocrocite. Overall, these results provide new insights into the stability of U(V) incorporated iron (oxyhydr)oxides during sulfidation, confirming the longer term retention of U in the solid phase under complex, environmentally relevant conditions.

Sulfidated nano zerovalent iron (S-nZVI) for in situ treatment of chlorinated solvents: A field study.

Sulfidated nano zerovalent iron (S-nZVI), stabilized with carboxymethyl cellulose (CMC), was successfully synthesized on site and injected into the subsurface at a site contaminated with a broad range of chlorinated volatile organic compounds (cVOCs). Transport of CMC-S-nZVI to the monitoring wells, both downgradient and upgradient, resulted in a significant decrease in concentrations of aqueous-phase cVOCs. Short-term (0-17 days) total boron and chloride measurements indicated dilution and displacement in these wells. Importantly however, compound specific isotope analysis (CSIA), changes in concentrations of intermediates, and increase in ethene concentrations confirmed dechlorination of cVOCs. Dissolution from the DNAPL pool into the aqueous phase at the deepest levels (4.0-4.5 m bgs) was identifiable from the increased cVOCs concentrations during long-term monitoring. However, at the uppermost levels (∼1.5 m above the source zone) a contrasting trend was observed indicating successful dechlorination. Changes in cVOCs concentrations and CSIA data suggest both sequential hydrogenolysis as well as reductive ß-elimination as the possible transformation mechanisms during the short-term abiotic and long-term biotic dechlorination. One of the most positive outcomes of this CMC-S-nZVI field treatment is the non-accumulation of lower chlorinated VOCs, particularly vinyl chloride. Post-treatment soil cores also revealed significant decreases in cVOCs concentrations throughout the targeted treatment zones. Results from this field study show that sulfidation is a suitable amendment for developing more efficient nZVI-based in situ remediation technologies.