Leaching Of Co Research Articles

An effective tandem leaching method for recovering precious metals from depleted ternary lithium-ion batteries

The increasing volume of spent ternary lithium batteries necessitates the development of an environmentally friendly and efficient recycling process tailored for these batteries. This paper introduces an innovative leaching system that employs oxalic acid and its derivative, Deep Eutectic Solvents (DES), as leaching agents, specifically designed to selectively recover Li and other valuable metals from the cathode materials of discarded ternary lithium batteries, Li(NixCoyMn1-x-y)O2 (NCM). These findings indicate that oxalic acid is capable of selectively leaching Li without the need for reducing agents, whereas DES effectively segregates and leaches other valuable metals. The optimal parameters determined through orthogonal experiments for the initial leaching stage included a solid-to-liquid ratio of 15 g L−1, leaching duration of 3 h, temperature of 75 °C, and stirring speed of 400 rpm, resulting in a Li leaching rate of 99.95%. In the subsequent step, DES enabled the precipitation of Ni and the leaching of Co and Mn within 2 h at 110 °C, achieving recovery rate of 99.88% for Ni, 98.1% for Co, and 90% for Mn, while also significantly optimizing the recovery conditions. This breakthrough may offer an environmentally benign and effective method for the selective recovery of Li and other valuable metals.

Efficient activation of peroxymonosulfate by CoMg2Mn-LDO for the degradation of orange Ⅱ: The important synergy of Mg

Advanced oxidation process (AOP) based on peroxymonosulfate (PMS) has aroused extensive discussion in the degradation of organic pollutants due to the strong oxidative ability of SO4•−. Great attention has been paid to developing transition metal catalysts for PMS activation. Still, few studies focused on the co-catalysis effect of non-redox metals. To study the co-catalysis of Mg and develop a more efficient metal catalyst, the CoMg2Mn-LDO was prepared by a co-precipitation method accompanied by calcination. The material showed an excellent ability for PMS activation. 97.1% of Orange Ⅱ was degraded within 15 min with the reaction rate constant (kobs) of 0.539 min−1 when pH equals 6.7, the dosages of CoMg2Mn-LDO and PMS were 90 mg L−1 and 100 mg L−1, respectively. By contrast, the value of kobs was 0.375 min−1 for the system of Co3Mn-LDO/PMS at the same experimental conditions. The electron paramagnetic resonance (EPR) and quenching experiments results proved the existence of O2•−, SO4•− and HO• in the CoMg2Mn-LDO/PMS system and the dominant role of SO4•− in Orange Ⅱ degradation. The synergistic effects among Co, Mn, and Mg were found to be responsible for the outstanding catalytic ability of CoMg2Mn-LDO. The presence of Mg could not only promote the formation of Mg–HSO5− and CoOH+ complexes but also reduce the leaching of Co and Mn, which accelerated the generation of free radicals and decreased secondary pollution risk. Based on the overall analysis, reasonable activation mechanisms of PMS and possible degradation pathways of Orange Ⅱ in this reaction system were proposed. This work proves that Mg could be applied as an effective co-catalytic element and provides new insight into developing transition metal catalysts for PMS-based AOPs.

Recovery of valuable metals from spent lithium-ion batteries using microbial agents for bioleaching: a review.

Spent lithium-ion batteries (LIBs) are increasingly generated due to their widespread use for various energy-related applications. Spent LIBs contain several valuable metals including cobalt (Co) and lithium (Li) whose supply cannot be sustained in the long-term in view of their increased demand. To avoid environmental pollution and recover valuable metals, recycling of spent LIBs is widely explored using different methods. Bioleaching (biohydrometallurgy), an environmentally benign process, is receiving increased attention in recent years since it utilizes suitable microorganisms for selective leaching of Co and Li from spent LIBs and is cost-effective. A comprehensive and critical analysis of recent studies on the performance of various microbial agents for the extraction of Co and Li from the solid matrix of spent LIBs would help for development of novel and practical strategies for effective extraction of precious metals from spent LIBs. Specifically, this review focuses on the current advancements in the application of microbial agents namely bacteria (e.g., Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans) and fungi (e.g., Aspergillus niger) for the recovery of Co and Li from spent LIBs. Both bacterial and fungal leaching are effective for metal dissolution from spent LIBs. Among the two valuable metals, the dissolution rate of Li is higher than Co. The key metabolites which drive the bacterial leaching include sulfuric acid, while citric acid, gluconic acid and oxalic acid are the dominant metabolites in fungal leaching. The bioleaching performance depends on both biotic (microbial agents) and abiotic factors (pH, pulp density, dissolved oxygen level and temperature). The major biochemical mechanisms which contribute to metal dissolution include acidolysis, redoxolysis and complexolysis. In most cases, the shrinking core model is suitable to describe the bioleaching kinetics. Biological-based methods (e.g., bioprecipitation) can be applied for metal recovery from the bioleaching solution. There are several potential operational challenges and knowledge gaps which should be addressed in future studies to scale-up the bioleaching process. Overall, this review is of importance from the perspective of development of highly efficient and sustainable bioleaching processes for optimum resource recovery of Co and Li from spent LIBs, and conservation of natural resources to achieve circular economy.

Wastewater flocculation substrate derived three-dimensional ordered macroporous Co single-atom catalyst for singlet oxygen-dominated peroxymonosulfate activation

Herein, wastewater flocculation substrate is used as a carbon source to prepare a three-dimensional ordered macroporous (3DOM) structure carbon-based catalyst with the CoN4 coordination active sites (Co-NC-PS) through a hard-template strategy. Abundant single-atom CoN4 active sites endow the Co-NC-PS with splendid performance in degrading organic pollutants by activating peroxymonosulfate (PMS). Experiment results show that the singlet oxygen (1O2) is the main reactive oxygen species (ROSs) for bisphenol A (BPA) degradation. The strong coordination of Co atoms with N atoms not merely avoids the leaching of Co and improves the stability of the catalyst but also establishes stable adsorption configuration and facilitates the generation of 1O2 proven by density functional theory (DFT) calculations. This study provides the design of efficient Co carbon-based catalysts in mint conditions with high stability for water treatment, as well as a new idea for the preparation of high-value-added products from the recycling of flocculated waste.

Mechanistic insight into SO4•−/•OH radical for enhancing stability and activity of LaMO3 perovskite toward detoxification of bulk pharmaceutical wastewater: Stoichiometric efficiency and controlled leaching study

This study aims to investigate the detoxification of real pharmaceutical manufacturing wastewater by PMS activated with perovskite LaMO3 (M = Cu, Co, Fe), synthesized by citric sol–gel method. The textural properties of synthesized perovskite were monitored by BET, FESEM/EDS, TEM, XRD, FTIR, and XPS techniques. The effects of key parameters (PMS dose, catalyst, pH and reaction temperature) on ofloxacin degradation along with PMS utilization efficiency as well as PMS consumption were evaluated in detail. Catalyst LaCoO3 exhibited the excellent catalytic activity and stability towards the degradation of ofloxacin (97.11 %) and COD (79.41 %) at optimum operating conditions. Removal of ofloxacin and COD were suppressed by 7 % and 9 % over the fourth cycle, along with minor leaching of Co were observed. Quenching experiments and EPR results demonstrated that both ROS species (SO4•− and •OH) were dominant species for ofloxacin degradation in LaCoO3/PMS system. The treatment cost for ofloxacin degradation in LaCoO3/PMS system was estimated to be 40.78$/m3 of real pharmaceutical wastewater. Six plausible degradation pathways of ofloxacin were proposed based on intermediate compounds identified by GC-MS and reported literature.

Alkali salts of amino acids as alkaline additives for neutralization of acidic corrosion inhibitors

We present alkali salts of amino acids as functional, non-toxic, non-hazardous, non-volatile, chemically stable, and cheap alkaline additives for common acidic corrosion inhibitors. The resulting mixtures have been evaluated for Co, Ni, and Cu leaching and were analyzed by chip filter assay, potentiodynamic polarization measurements, electrochemical impedance measurements, and gravimetry for corrosion protection of iron and steel in aqueous environment at slightly alkaline pH. Leaching of Co and Ni was found to depend on the corresponding complex stabilities. Taurine (Tau) as well as aminohexanoic acid (AHX) leads to low leaching of Co and Ni. Particularly AHX is an attractive low leaching additive leading to lower Co and Ni concentrations in solution than currently used amino alcohols. Glu and Tau were found to synergistically interact with several acidic corrosion inhibitors of the carboxylic acid and the phosphonic acid type. Tau had a particularly positive impact on the protective properties of carboxyphosphonic acids. Glu had also a positive effect on the anti-corrosive properties of several acidic corrosion inhibitors and served as an anti-scalant. Alkali salts of Glu and Tau might thus serve as commercially and ecologically attractive substitutes for current alkaline additives to acidic corrosion inhibitors.

Self-Assembly of Pt3Co Superlattice as a Catalyst for Oxygen Reduction Reaction

Pt-based binary alloy catalysts with different structures have been designed to boost the catalytic activity of oxygen reduction reaction (ORR), however, the dissolution of the transition metals leads to insufficient catalyst durability. In order to solve this problem, a self-assembly Pt3Co superlattice catalyst is reported in this paper, which exhibits enhancement in both activity and durability towards ORR. Compared with commercial Pt catalyst, the mass activity and specific activity of Pt3Co superlattice are significantly improved. The Pt3Co superlattice dropped only 9.2% and 12.4% in the mass activity and specific activity after 5000 cycles of durability tests. Moreover, the mechanistic studies find that the improvement of the catalyst performance is mainly dominated by reducing the energy of oxygen adsorption to a more suitable energy, optimizing the electronic structure of d-band, and suppressing the leaching of Co. This work provides a strategy to prepare superlattice catalyst with great activity and durability toward ORR.

Baselining Activity and Stability of ORR Catalysts and Electrodes for Proton Exchange Membrane Fuel Cells for Heavy-Duty Applications

Activity and stability of electrodes with Pt and PtCo alloy catalysts supported on high surface area carbon, hereafter to as a-Pt/C and d-PtCo/C, were evaluated for heavy-duty applications. Both catalysts had nearly identical Pt loading (50-wt% Pt on carbon and 0.25 mgPt cm−2) and had undergone thermal treatment to stabilize them by growing the average particle size to 4–5 nm. Both were subjected to 90,000 (90 k) standard accelerated stress tests (AST) cycles consisting of 0.6–0.95 V square wave potentials, 3-s hold at upper and lower potential limits in H2/N2 at 1.5 atm, 80 °C and 100% RH. Test protocols were developed to monitor the performance losses and characterize them in terms of activity for the oxygen reduction reaction (ORR), oxygen transport in the electrode and proton transport in the membrane and cathode catalyst layer. Despite the nearly double initial ORR activity, the PtCo/C electrode degraded faster due to the leaching of Co from the catalyst that had started even before the imposition of the AST potential cycles. Commensurate with Co leaching, Co poisoning of ionomer is responsible for the inferior performance of d-PtCo/C electrode at high current densities both before and after AST.

Autocatalytic formed bamboo-like N-doped carbon nanotubes encapsulated with Co nanoparticles as highly efficient catalyst for activation of peroxymonosulfate toward degradation of tetracycline

Co-based catalysts activated peroxymonosulfate (PMS) for organic pollutants degradation has been extensively studied. Co dissolution of Co-based catalysts would result in secondary environmental contamination. Co autocatalysis the formation of bamboo-like N-doped carbon nanotubes to confine Co nanoparticles (Co NPs). Herein, the N-doped carbon nanotubes encapsulated Co (Co@NCTs) were successfully synthesized through a one-step high-temperature calcination method at different temperatures. Co@NCTs-800 exhibited excellent catalytic performance, the degradation efficiency of tetracycline (TC) could reach 94.5% with only 0.05 g/L catalyst in activating PMS. In addition, the encapsulation of carbon nanotubes inhibits the dissolution of Co, the Co2+ dissolution was 0.0594 mg/L in 40 min in the system of Co@NCTs-800/PMS. Free radical quenching tests, electron paramagnetic resonance, and electrochemical measurements revealed that the non-radical route was dominated by tetracycline degradation, with singlet oxygen (1O2) and electron transfer as the principal active species. The N-doped carbon nanotubes can effectively encapsulate Co, which not only reduces the leaching of Co but also play a synergistic role with Co in degrading organic pollutants. In addition to this, the degradation mechanism and pathways of TC were further investigated. The Co@NCTs-800/PMS system was also able to successfully decompose a variety of organic contaminants, demonstrating that it has real application potential in wastewater.

Synergistic enhancement of metal extraction from spent Li-ion batteries by mixed culture bioleaching process mediated by ascorbic acid: Performance and mechanism

Pure and mixed cultures of microorganisms are used to leach spent Li-ion batteries (LIBs) to extract high-value metals. However, a low metal leaching efficiency is a general problem, hindering the commercialization of spent LIBs bioleaching. Therefore, a mixed culture bioleaching (MCB) process, mediated by ascorbic acid (AA), is proposed to promote the leaching of spent LIBs. Results show that the AA-MCB process leaches 94% Co and 95% Li at a pulp density of 20 g L−1, realizing 54% Co and 31% Li enhancement. Mass spectrometry analysis showed that a reduced bioleaching system is constructed by the mixed culture, AA, and AA products. In this system, bacteria promote LiCoO2 exposure on spent LIB surface by producing bioacid. Therefore, the refractory Co(III) easily reduces to soluble Co(II) by AA and its products, leading to the destruction of the crystalline structure of LiCoO2. Furthermore, bioacid facilitates easy leaching of Co and Li from structurally damaged LiCoO2. Ultimately, the AA-MCB process transforms spent LIBs from hazardous to general solid waste, exhibiting no biotoxicity to Escherichia coli growth. Therefore, bioleaching process intensification by adding a green organic reducing agent is a promising alternative for effective metal extraction from spent LIBs, enriching the current recycling technologies of spent LIBs.

Co and N co-doped hierarchical porous carbon as peroxymonosulfate activator for phenol degradation via nonradical pathway mechanism

Developing catalysts with high metal utilization rates for activation of peroxymonosulfate (PMS) has attracted extensive attention. Herein, Co and N co-doped hierarchical porous carbon (Co/HOPNC) was synthesized successfully for peroxymonosulfate (PMS) activation to degrade phenol. Transmission Electron Microscope (TEM) confirmed that this hierarchical porous carbon indeed offered a site for the highly dispersed with low doping amount of Co. The 1.5 % Co/HOPNC exhibited the optimal removal efficiency and admirable adaptability to pH, temperature and different co-existing ions, which was credited to the highly dispersing Co atoms. Furthermore, the leaching of Co showed a neglectable impact on catalytic efficiency, revealing metal leaching was indeed inhibited. Remarkably, singlet oxygen (1O2) and high-valence Co-oxo species were verified as major contributors to enhance the catalytic activity. This finding gives a unique insight in PMS activation mechanism triggered nonradical pathways of hierarchical porous carbon materials. Moreover, the 1.5 % Co/HOPNC displayed an outstanding effect on phenol degradation in actual wastewater which expressed great potential in practical applications.

Leaching valuable metals from spent lithium-ion batteries using the reducing agent methanol.

When considering resource shortages and environmental pressures, salvaging valuable metals from the cathode materials of spent lithium-ion batteries (LIBs) is a very promising strategy to realize the green and sustainable development of batteries. The reductive acid leaching of valuable metals from cathode materials using methanol as a reducing agent was studied. The results show that the leaching efficiencies of Co and Li are 99% under optimal leaching conditions. The leaching kinetics of cathode materials in a H2SO4-methanol system indicate that the leaching of Co and Li is controlled by diffusion, with activation energies of 69.98 and 10.78kJ/mol, respectively. Detailed analysis of the leaching reaction mechanism indicates that methanol is ultimately transformed into formic acid through a two-step process to further enhance leaching. No side reactions occur during leaching. Methanol can be a sustainable alternative for the reductive acid leaching of valuable metals from spent LIBs due to its high efficiency, application maturity, environmental friendliness, and low cost.

Bimetallic zeolitic imidazolate framework-derived nitrogen-doped porous carbon-coated CoFe2O4 core–shell composite with high catalytic performance for peroxymonosulfate activation in Rhodamine B degradation

The rational design and development of a highly efficient and sustainable heterogeneous catalyst has become a limiting factor for the practical application of persulfate-based advanced oxidation processes in organic dye degradation. Herein, a nitrogen-doped porous carbon-coated CoFe 2 O 4 core – shell composite (CoFe 2 O 4 @NPC) was synthesized by in-situ growth of cobalt/iron bimetallic zeolitic imidazolate framework-9 (Co/Fe-ZIF-9) on graphene oxide (GO) nanosheets followed by one-step calcination of the bimetallic ZIF-GO composite in nitrogen. The textural, chemical, and magnetic properties of the composites were comprehensively characterized using various analytical techniques. The catalytic performances of the as-prepared CoFe 2 O 4 @NPC in activating PMS to decompose Rhodamine B (RhB) were then systematically evaluated. The composite calcined at 600 °C exhibited the highest catalytic activity. The maximum RhB degradation efficiency of 99.05% and pseudo-second-order kinetic constant of 0.0766 L/(mg·min) were achieved after 20 min at 25 °C. Moreover, CoFe 2 O 4 @NPC displayed excellent recyclability and stability with negligible leaching of Co and Fe ions into the solution. Subsequently, electron spin resonance, reactive oxygen species quenching, and X-ray photoelectron spectroscopy were conducted to clarify the PMS activation mechanisms. Results suggested that SO 4 •− and •OH were generated during PMS activation and that SO 4 •− was the predominant radical involved in RhB degradation. In addition, Co(II), Fe(III), and structured nitrogen, especially pyridinic and graphitic N groups, participated in the PMS activation. Some insights into possible mechanisms of RhB degradation were also attained from spectral analyses. All these results suggested that CoFe 2 O 4 @NPC had excellent potential as a PMS activator for application in dye-contaminated wastewater treatment. • Nitrogen-doped porous carbon shell-coated CoFe 2 O 4 core – shell composites (CoFe 2 O 4 @NPC) prepared. • Multiple parameters influenced the catalytic performance of CoFe 2 O 4 @NPC. • CoFe 2 O 4 @NPC recyclable, stable, and resists the leaching of Co and Fe ions. • SO 4 •− is the principle radicals involved in the degradation of RhB. • Co(II), Fe(III) and structured nitrogen participated in the PMS activation process.

Petal-like CuCo2O4 spinel nanocatalyst with rich oxygen vacancies for efficient PMS activation to rapidly degrade pefloxacin

Herein, for the first time, we report the design and preparation of petal-like spinel structure CuCo2O4−σ with rich oxygen vacancies (Ov) derived from CuCo-zeolitic imidazolate framework (ZIF) for activating peroxymonosulfate (PMS) to quickly and efficiently degrade pefloxacin (PFX), one of important second-generation fluoroquinolone antibiotics. The petal-like CuCo2O4-σ was fabricated via carbonizing bimetal CoCu-ZIF precursor at 700 °C in air, followed by simple NaBH4 reduction strategy. Various characterization outcomes prove that the CuCo2O4-σ possesses rich Ov, hierarchical meso- and macro-porous microstructures, and stable spinel structure. The CuCo2O4-σ/PMS system exhibited approximate 95% PFX degradation during 5 min reaction, while only 4% PFX removal did in the presence of control product C-700. The PFX degradation rate constant (kapp) in the CuCo2O4-σ/PMS system was 0.572 min−1, which was about 78 times that of the C-700/PMS system (0.0073 min−1) and about 34 times that of the CuCo2O4/PMS system (0.017 min−1). Similarly, the kapp values for the Co3O4-σ/PMS and CuO1-σ/PMS systems are about 7.7 and 3.2 times those of the Co3O4/PMS and CuO/PMS systems, respectively, indicating that Ov significantly accelerates PFX degradation. In addition, the kapp value for the CuCo2O4-σ is much higher than the sum of kapp values for the Co3O4-σ and CuO1-σ, indicating important role of synergy between Cu and Co in PFX degradation. The electrochemical impedance and XPS trials demonstrate that, in addition to accelerate the electron transfer ability of CuCo2O4, the introduction of Ov also leads to the generation of low valence Co2+ ions and Cu+ ions on the surface of CuCo2O4-σ, driving the redox cycles of Co2+/Co3+ and Cu+/Cu2+ to accelerate PMS activation and realize fast PFX degradation. The CuCo2O4-σ exhibited good PMS activation capability in the 3.0 to 10.0 pH range, and good recyclability with over 92% PFX removal after the fourth-cycle run, and low leaching of Co and Cu during catalytic reaction. In addition, the CuCo2O4-σ/PMS system can rapidly degrade other organic pollutants (i.e. levofloxacin, ciprofloxacin, tetracycline hydrochloride, and rhodamine B), indicating its good universality. The active reactive species investigation reveals the generation of SO4•–, •OH, O2•− and 1O2 in the catalytic degradation of PFX. Effects of various factors, i.e. the calcination temperature for the preparation of CuCo2O4-σ, initial solution pH, catalyst dosage, PMS concentration, reaction temperature, inorganic anions, and humic acid on the degradation of PFX in the CuCo2O4-σ/PMS system were explored. Relative to other nanocatalysts for PMS activation, the CuCo2O4-σ exhibits low activation energy of 27.0 KJ/mol. Combined with LC-MS determination of PFX degradation intermediates, the possible PMS activation mechanism by the CuCo2O4-σ and possible PFX degradation pathways were proposed.

Novel halloysite nanotube-based ultrafine CoMn2O4 catalyst for efficient degradation of pharmaceuticals through peroxymonosulfate activation

In this study, a highly efficient catalyst was prepared by loading CoMn2O4 spinel oxide (CMO) on halloysite (HNT), a natural mineral nanotube, for the activation of peroxymonosulfate (PMS) towards the degradation of some frequently detected pharmaceuticals in water bodies. The CMO nanoparticles are evenly distributed on the outer surface of HNT tubes with little agglomeration and smaller grain size compared to bare CMO. A moderate loading of 40% CMO on HNT (i.e. 40-CMO/HNT) displayed an excellent catalytic ability, leading to the complete degradation of carbamazepine in 20 min. Carbamazepine was decomposed gradually by oxidation, hydrolysis and the cleavage of rings with 60% mineralization rate. The adhering of CMO on HNT contributed to better stability and durability than bare CMO and the recycling of 40-CMO/HNT was found feasible and efficient. A test of three-(3)-time-reuse showed that over 90% of carbamazepine was removed in each cycle, while the leaching of Co and Mn was reduced stepwise by 12.6% and 8.9%, respectively. The possible universal application of 40-CMO/HNT in removing common antibiotics was verified by targeting tetracycline, ofloxacin and sulfamethoxazole. The positive results promise the development of an effective treatment technology for the removal of common pharmaceuticals.

Novel electrochemically driven and internal circulation process for valuable metals recycling from spent lithium-ion batteries.

The sustainable recycling of valuable metals from spent lithium-ion batteries (LIBs) is impeded by the issues of extensive chemicals consumption, tedious separation process and deficient selectivity. Here, novel electrochemically driven and internal circulation strategy was developed for the direct and selective recycling of valuable metals from waste LiCoO2 of spent LIBs. Firstly, the waste LiCoO2 can be efficiently dissolved by generated acid (H2SO4) during electro-deposition of Cu from CuSO4 electrolyte. Then, Co2+ ions in the lixivium can be electrodeposited and recovered as metallic Co with a coinstantaneous regeneration of H2SO4 and regenerated acid can be reused as leachant without obvious shrinking of leaching capability based on circulating leaching results. Over 92% Co and 97% Li can be leached, and 100% Cu and 93% Co are recovered as their metallic forms under the optimized experimental conditions. Results of leaching kinetics suggest that the leaching of Co and Li is controlled by internal diffusion with significantly reduced apparent activation energies (Ea) for Li and Co. Finally, Li2CO3 can be recovered from Li+ enriched lixivium after circulating leaching. This recycling process is a simplified route without any input of leachant and reductant, and valuable metals can be selectively recovered in a closed-loop way with high efficiency.

Pursuing green and efficient process towards recycling of different metals from spent lithium-ion batteries through Ferro-chemistry

Sustainable recycling of different value-added metals from spent lithium-ion batteries (LIBs) can expect significant environmental and economic benefits for the fulfillment of resources utilization. During the separation and recovery of different metals, excessive chemical consumption caused by prolonged processes may eventually spoil the environmentally soundness recycling of spent LIBs. Here, Ferro-chemistry was innovatively proposed towards the recycling of different metals based on transformation of iron morphology from different types of spent LIBs (LiCoO2 and LiFePO4). It can be concluded from the thermodynamic results that redox reaction will take place in dilute sulfuric acid medium without addition of reductant/oxidant, indicating that Fe(II) in LFP can be used as reductant for the direct leaching of LiCoO2. Leaching results indicate that 99.9% Li, Fe, P and 92.4% Co can be dissolved and existed as Fe3+, Li+, PO43− and Co2+ under the optimized conditions, with a decline of over 80% acid consumption. The leaching kinetics of different metals and reaction mechanism suggest that Fe(II) will be promptly liberated to lixivium and then slowly oxidized into Fe(III) with the existence of Co(III), resulting in a synergetic leaching of Co and Fe. Then, Fe(III) can be precipitated as FePO4 at pH of 2.5, which can remove PO43− with the direct generation of LiFePO4 precursors. This above ferro-chemistry strategy can effectively reduce the consumption of chemicals with reduced environmental footprint.

Process and Kinetics of Extracting Cobalt from Complex High-Silicon White Alloy by Sulfuric Acid Oxidation Leaching

A sulfuric acid system was used to recover Co from cobalt white alloy, and the leached cobalt was electrochemically dissolved.i This is a key step to separate the iron-silicon alloy phase from valuable metals when leaching cobalt white alloys with high silicon and iron contents. As an additive, sodium hypochlorite (NaClO) acts as an oxidant to break cobalt encapsulation and enhances leaching. It generates chloride ions, which further enhance Co leaching based on their corrosive ability. The results showed that the maximum leaching ratio of Co from the waste cobalt white alloy was 97.76%. Kinetic analysis showed that the apparent activation energy of Co leaching was 34.58 kJ/mol, and the surface chemical reaction was a controlling step for this process. The kinetic equation for the leaching of Co can be expressed as $$1 - \left( {1 - \alpha } \right)^{\frac{1}{3}} = 0.065t \times \left( {r_{0}^{ - 1} } \right) \times \left[ {{\text{H}}_{2} {\text{SO}}_{4} } \right]^{2.44} \times \exp \left( {\frac{ - 34580}{{8.314T}}} \right)$$ .

Nanoscale zero-valent iron/cobalt@mesoporous hydrated silica core–shell particles as a highly active heterogeneous Fenton catalyst for the degradation of tetrabromobisphenol A

Degradation of TBBPA by NZVI/NZVC@mHS CSP/H 2 O 2 heterogeneous Fenton system. • Synthesis of NZVI/NZVC@mHS CSP materials by one-pot method. • The core–shell structure of the material reduced aggregation and increased the specific surface area. • The mesoporous network structure effectively prevented the leaching of Co (II). • NZVI/NZVC@mHS CSP efficiently degraded TBBPA as Fenton-like catalyst. While the bimetal heterogeneous Fenton system degraded organic pollutants, the leaching of heavy metals caused secondary pollution. To resolve this problem, nanoscale zero-valent iron/cobalt@mesoporous hydrated silica core–shell particles (NZVI/NZVC@mHS CSP) were synthesized as a novel Fenton-like catalyst for the rapid degradation of Tetrabromobisphenol A (TBBPA). The performance of NZVI/NZVC@mHS CSP in the degradation of TBBPA and the mechanism of their action were investigated through scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. NZVI/NZVC@mHS CSP exhibited a regular spherical shape with a surface area (115.44 m 2 ·g −1 ) that was 5 times more than that of the ordinary NZVI/NZVC (23.59 m 2 ·g −1 ). The core of NZVI/NZVC was covered with a hydrated silica shell that formed a mesoporous network that effectively prevented the leaching of cobalt ions from the core. The best catalytic performance of NZVI/NZVC@mHS CSP was obtained by optimizing the iron-to-cobalt ratio, H 2 O 2 concentration, and the dosage of the catalyst. The optimized NZVI/NZVC@mHS CSP exhibited the greatest mineralization activity (97.13%) for TBBPA removal than those in NZVI/NZVC bimetal (84.49%) and pure NZVI/NZVC@mHS CSP (59.37%). Thus, our results demonstrated that NZVI/NZVC@mHS CSP exhibited excellent reactivity in potential application as a highly active heterogeneous Fenton catalyst for degradation of TBBPA in soil and groundwater.

Kinetic modeling of the leaching of LiCoO2 with phosphoric acid

In this article, we analyze the leaching kinetics with phosphoric acid of LiCoO2 samples from spent Li-ion batteries and commercial LiCoO2. The purpose was to study the mechanism by which the extraction reaction of cobalt and lithium is produced from the solid samples. The experimental results showed that raising the temperature and the reaction time contributed to improving both the extraction of Li and Co from the structure. The leaching rate of the metals from both samples in the phosphoric acid solution could be expressed as: ln⁡1-X=-b1ln⁡1+b2t-b2t1+b2t. The morphology of the solid revealed that the dissolution reaction of the samples develops from preferential growth of active sites, points susceptible to chemical interaction, occurring in one direction, giving rise to the start and progress of the reaction. The generation of these sites in the LCO-H3PO4 reaction system is of the "sequential" type. The apparent activation energy values for the leaching of Co and Li would indicate that the surface chemical reaction is the rate-controlling step during this dissolution process.