Leach Residue Research Articles

Near-Zero-Waste Approach for the Treatment of Saprolitic Nickel Laterite via a Combined Hydrometallurgical Process

Atmospheric acid leaching can be used for processing the nickel laterite ore. The lixivium composition necessitates Fe3+ separation as the first step in recovering valuable metals. However, traditional partial neutralization has the problem of significant loss of Ni2+ and Co2+ ions due to the high Fe3+ concentration. Besides, the discharged acidic residue leads to environmental pollution. This study proposes a combined hydrometallurgical method for efficiently recovering valuable components from saprolitic laterite. After atmospheric sulfuric acid leaching, the Fe3+ in the lixivium was first separated using phosphoric acid and sodium hydroxide as reagents; 92% of the Fe3+ precipitated as iron phosphate at a pH of 1.8. The charge and discharge capacities of the LFP sample prepared from this iron phosphate at the rate of 1 C were 157 and 154 mA h/g, respectively. During the recovery of Fe3+ ions, approximately 100% of other metals were retained in the aqueous solution. After adjustment of the pH to 6.0, this solution was used to remove impurities, including Al, Mn, Cr, and Fe. Then, more than 98% of Ni and Co were recovered as Ni,Co(OH)2 precipitates at a pH of 8.0–9.0. When the pH was raised to 11.0, over 98% of Mg precipitated as Mg(OH)2. The leach residue with a high silica content was used to prepare calcium silicate hydrate (C–S–H) via a hydrothermal process. The recovery of FePO4, Mg(OH)2, and C–S–H, in addition to Ni,Co(OH)2, made this a value-added process and with a near-zero residue discharge.

Spatial Distribution and Controlling Factors of Groundwater Quality Parameters in Yancheng Area on the Lower Reaches of the Huaihe River, Central East China

Groundwater samples that were distributed across the Yancheng area in the lower reaches of the Huaihe River were collected from the phreatic aquifer and first confined water layer during the summer of 2016. Using the water quality index, the suitability of the groundwater for drinking and irrigation purposes was systematically evaluated. The controlling factors of solute formation and the causes of water quality deterioration were discussed using the Chadha diagram and the relationship among ions. The results showed that there was a serious lack of excellent- and good-grade groundwater for drinking purposes in the shallow layer. The groundwater was also found to be unsuitable for irrigation, with only approximately 70% being of good quality. The spatial heterogeneity of the water quality was significant, and poor-quality groundwater was found to be distributed discontinuously. The high concentration of alkali metals in the shallow groundwater was found to be due to the weathering of silicate rocks in clay and subclays and the replacement of Ca2+ with Na+ in the surrounding rocks. Additionally, the leaching of residues from the salt industry and marine sediment in historical periods were identified as key factors leading to the scattering of poor-quality groundwater in inland areas. The study found that the shallow groundwater in the study area was not significantly affected by seawater intrusion and human activities. However, signs of human activity, such as agricultural fertilizer and urban sewage, were found to be affecting the “excellent-” and “good-grade” shallow groundwater intended for irrigation purposes.

Hydrometallurgical recovery of critical metals from an incinerated fly ash of municipal solid waste from western India

ABSTRACT The global generation of 2.2 billion tons of municipal solid waste (MSW) as a result of population growth, rapid urbanization, and industrial development has highlighted an urgent need for MSW management. Incineration is widely accepted as one alternative to landfilling; however, the recovery of heavy metals from the incinerated fly ash (IFA) before its final disposal is highly desirable to make the process sustainable. In this study, we studied the recovery of zinc and lead from typical MSW-IFA employing hydrometallurgical techniques. Sulfuric acid leaching was performed to selectively leach out zinc over the lead at the optimal condition of H2SO4 concentration = 1.5 M, temperature = 30°C, S/L ratio = 150 g/L, time = 2 h, and stirring speed = 300 rpm. The sulfate leach liquor was treated with a 5% stoichiometric excess of oxalic acid to precipitate>99% of zinc to be recovered as ZnC2O4·2 H2O. Further, the remaining lead in leach residue was subsequently leached in 50 g/L NaCl solution for 2 h yielded>94% efficiency. The dissolved lead was crystallized to recover the crystals of PbCl2. The demonstrated process leads towards the recovery of critical metals from an alternative source of MSW-IFA.

Overlooked residue of Li-ion battery recycling waste as high-value bifunctional oxygen electrocatalyst for Zn-air batteries

Continuously increasing production of Li-ion batteries (LIBs) for the Green Transition is underlined by the absence of feasible recycling methods for graphite, regardless of its criticality as a raw material. The current study demonstrates a novel strategy to valorize waste graphite as a valuable raw material in oxygen electrocatalyst production. Industrially produced LIBs post-metallurgical leach residue was transformed into highly active bifunctional oxygen electrocatalyst, which was subsequently successfully applied as an active catalyst for Zn-air batteries. Moreover, produced graphene-like material was in-situ doped by the impurity cobalt present in the recycling residue. The resultant Zn-air battery was shown to deliver a high specific capacity of 719 mA h g-1, peak power density of 112.8 mW cm-2 and could be cycled over 400 times. Results clearly demonstrate that an often-neglected LIB recycling waste fraction can be a valuable source for electrocatalysts production required in metal-air batteries and regenerative fuel cells.

Innovative Recovery of Gallium and Zinc from Corundum Flue Dust by Ultrasound-Assisted H2SO4 Leaching

ABSTRACT Rare metal gallium is classified as a strategic material because of continued high demand, uncertain supply, and low reserves. Corundum flue dust (CFD) is generated during bauxite smelting to produce brown corundum. Gallium (Ga), Zinc (Zn), and potassium in the bauxite could be enriched with CFD through this process, so CFD is regarded as one of the potential sources of Ga and Zn. A novel that utilizes ultrasound to enhance the H2SO4 leaching efficiency of Ga and Zn from CFD was developed from CFD. The effects of ultrasound power, leaching time, sulfuric acid concentration, and leaching temperature on the leaching behavior of Ga and Zn were studied, and the corresponding kinetics model was established. It was found that the maximum Ga and Zn leaching efficiencies of 81.22% and 96.72% were obtained at optimum leaching conditions: the leaching temperature of 90°C, the leaching time of 60 min, 3 M H2SO4, the solid-to-liquid ratio of 1:5 (g/mL), and the ultrasound power of 750 W. In all cases, the leaching effect of Zn is not significantly improved by ultrasonic treatment, but the leaching efficiency of Ga has a positive effect (more than an 18% increase). Kinetic analysis shows that the leaching process of Ga and Zn were controlled by chemical reaction and diffusion, respectively. The apparent activation energy values are 20.39 kJ/mol for Ga and 13.44 kJ/mol for Zn. The characterization of the leaching residues reveals that the ultrasound effected to enable the whole block to be fractured or dispersed into fragments, accelerating the penetration of H2SO4 into the pores and cracks at the solid, which further prompts the dissolution of the encapsulated gallium and achieves the conspicuous improvement to Ga leaching efficiency.

Water/acid/reductive biomass leaching of Cr(VI) in chromium ore processing residue (CORP) for safe discharge of effluent and to recover Cr(III) and gypsum

The hydrolyzed biomass, a green and renewable resource, was used as a reducing agent to achieve the harmless treatment of chromium ore processing residue (COPR). This paper proposes a detoxification process of two-stage sulfuric acid leaching accompanied by biomass reduction of hexavalent chromium and a one-step combined leaching and reduction process. The orthogonal tests and single factor tests allowed to propose the most suitable operating conditions of different stages such as biomass hydrolysis, two-stage acid leaching, reduction of the acid leachate and combined leaching and reduction. The Cr(VI) content in both the leach residue and reduction solution reached the discharge criterion. The FTIR and XPS measurements showed that the reducing sugars produced by the hydrolysis of biomass reacted with the leached Cr(VI) to generate chromium sulfate adsorbed on the surface of COPR. In addition, XRD, SEM-EDS showed that the gypsum was generated after COPR detoxification, which can be used for resource utilization, providing a new idea and reference for the harmless treatment of COPR producing Cr(III) and gypsum.

Post-Leaching of Silver from a Non-Sulfide Lead–Zinc Ore Flotation Tailing Leach Residue in a Copper–Ammonium Thiosulfate Solution: A Fuzzy Logic Prediction

Post-Leaching of Silver from a Non-Sulfide Lead–Zinc Ore Flotation Tailing Leach Residue in a Copper–Ammonium Thiosulfate Solution: A Fuzzy Logic Prediction

Phase transformation of montebrasite for efficient extraction and separation of lithium, aluminum, phosphorus

Montebrasite LiAlPO4(OH) is a high quality lithium extraction material with more than 8% Li2O content. The contents of Al and P as main component both exceed 16% while the chief impurity is SiO2, thereby the mineral purity is greater than 90%. In this paper, a process combining sulfuric acid baking and water leaching was proposed so as to realize the energy-efficient and comprehensive treatment of montebrasite and efficient extraction of Li, Al, and P. There are two main steps: (1) The montebrasite was heated and decomposed with sulfuric acid at 200 ℃. (2) The Li, Al and P in the baked slag were dissolved by water leaching. The X-ray diffraction(XRD) results of the baked slag prove that Li and Al are transformed into Li2SO4 and Al2(SO4)3 after decomposition by sulfuric acid. The only observed phase is SiO2 in the XRD patterns of leach residue, indicating that Li, Al and P are all transformed into soluble substances and leached by water after baking. The influence of baking temperature and baking time on the leaching rates of Li, Al and P was researched, and the leaching rates of Li, Al and P reached more than 96%. The novelty of the process lies in its low energy consumption, high comprehensive recovery rates of valuable elements and environmental friendliness.

Copper recovery from waste printed circuit boards with small peptides enhanced by ultrasound

Waste printed circuit boards (WPCBs) are one of the most critical and valuable components in electronic equipment. WPCBs contain many metals (Cu accounts for more than 90%), which are a potential secondary resource to overcome metal scarcity. The recovery of metals from WPCBs is significant for environmental protection and resource reuse. This investigation presents a simple and sustainable approach to leach Cu from WPCBs with small peptides enhanced by ultrasound. Various leaching parameters, including initial small peptides concentration, temperature and initial H2O2 volume fraction have a highly significant influence. The maximum Cu leaching were 95.4 ± 0.1%, 92.5 ± 0.1% and 87.4 ± 0.1% by glutathione (GSH), glycylglycine (GG), and glycyl-L-glutamine (GLG), which caused by the differences of small peptides functional groups. The Cu leaching by ultrasound exhibited 2.1–3.9 folds higher than without ultrasound treatment. The kinetic analysis showed that the Cu leaching from WPCBs was mainly controlled by diffusion and chemical reactions. The coordination numbers of copper-chelating GSH (CC-GSH), copper-chelating GG (CC-GG), and copper-chelating GLG (CC-GLG) were measured by simulation experiments. The hydroxyl, carboxyl, amino and sulfhydryl groups are the main reasons for the complexation of small peptides and Cu2+, which was confirmed by the characterization of copper-chelating small peptides (CCPs) crystal. The Cu leaching with small peptides enhanced by ultrasound potentially represents an innovative technology with significant advantages in metals extraction and time efficiency. Furthermore, the results provide perspectives and new insights into the preparation of CCPs and the industrial application of modified leaching residues.

Investigation of a novel alkali baking–leaching process for dissolution of Fe, Al, Ti, Sc, and Ga values and generation of alumina and titania from red mud

The current study investigates alkali baking using sodium hydroxide followed by water and sulfuric acid leaching to extract Al, Fe, Ti, Sc, and Ga values. Water leaching of baked mass selectively dissolves Al. Subsequent, sulfuric acid leaching of water-leach residue dissolves Fe, Ti, Sc, Ga, and remaining Al and Si values. The alkali baking forms sodium metal oxide (NaFeO2, Na2TiO3, NaAlO2, NaAlSiO4) phases, which improves the dissolution in sulfuric acid compared to the oxide phases of metals. The alkali dose was a prominent factor in forming sodium metal oxides. Baking at 600 °C, 1 h, 75 wt% NaOH yielded 60% Al dissolution during water leaching and 82% Ti, 83% Fe, 97% Sc, and 64% Ga dissolution during acid leaching. Scandium dissolution strongly correlates with titanium during leaching, and TEM analysis confirms the apparent enrichment of scandium in the anatase and hematite matrix. Carbonation of water leach solution precipitates alumina and dawsonite (NaAlCO3(OH)2) phases with a product having 85–87% Al2O3 purity and 12 wt% yield. Thermal hydrolysis of acid leach solution generates Ti(OH)4 precipitate which is calcined to obtain anatase with a 95–97% TiO2 and 13 wt% yield. The leach residue contains unreacted hematite and anatase phases having <10% Al2O3 and SiO2 with 6.5 wt% yield. The hydrolyzed solution contains Sc(III) (6 mg/L), Ga(III) (5 mg/L), and Fe(II) (28.4 g/L) ions. The proposed process consumes 0.75 kg NaOH and 1.40 kg H2SO4 per kg red mud and generates 0.14 kg alumina and 0.13 kg titania product with 0.07 kg residue enriched with 48% anatase.

Atmospheric acid leaching of powdery Ni-Co-Fe alloy derived from reductive roasting of limonitic laterite ore and recovery of battery grade iron phosphate

The efficient and inexpensive extraction of Ni and Co from limonitic laterite ore is becoming imperative due to the rapidly growing demand for nickel and cobalt driven by electric vehicles (EVs). In this work, powdery Ni-Co-Fe alloy was prepared from limonitic laterite via reductive roasting followed by magnetic separation, with nickel and cobalt recoveries of 91.9% and 93.3%, respectively. Most of the gangue material was rejected, and the obtained powdery alloy was readily dissolvable in sulfuric acid solution at atmospheric pressure. Under the conditions of 2.5 M H2SO4, 80 °C, 60 min, L/S ratio of 8 mL/g, the extractions of Ni, Co and Fe were 98.5%, 99.9% and 95.6%, respectively, and chemical reaction was the rate-controlling step. The proposed process is promising for the utilization of limonitic laterite ore with high leaching efficiency and less leach residue discharge.

Waste Treatment and Resource Utilization: Removal and recovery of soluble impurities from nitric acid leaching residue of phosphate rock by electrokinetic

Electrodynamic cleaning techniques for removing and recycling soluble impurities (phosphorus, fluorine, Sr, Pb, Cr, Cu, and Mn) in nitric acid leaching residues of phosphate rock (NG) were investigated. The PO43− concentration of the anode chamber was increased to 207.94 mg/L, while the F− concentration of the cathode chamber rose to 28.33 mg/L. Besides, the soluble phosphorus levels in the cathode regions (R1 and R2) were decreased by 98.02% and 90.16%, respectively. Moreover, the dissolved heavy metals, namely Mn, Cr, Cu and Pb in NG were enriched in the anode chamber, and Sr was enriched in the cathode chamber. The synergistic effects of electrocoagulation and electrodeposition lowered the levels of phosphate, fluoride, and heavy metals in the cathode, thus reducing the decreasing electrical conductivity. The migration and accumulation behaviors of soluble impurities in an electric field were regulated by electromigration, electro-osmotic flow, and electrolysis reaction. Considering that, this paper provides support for the harmless treatment of NG and the recovery of valuable elements, which is conducive to developing the wet-process phosphoric acid process and reducing the large-scale storage of phosphogypsum.

An effective method for directly extracting lithium from α-spodumene by activated roasting and sulfuric acid leaching

The global trend toward electrification has encouraged lithium's market position to grow prominently. Spodumene is the focus of lithium extraction owing to its abundant lithium resources. In this study, a novel lithium extraction method was proposed for α-spodumene by combining activated roasting and sulfuric acid leaching. First, the thermodynamics of the roasting process demonstrated that α-spodumene was converted into β-spodumene, which reacted with CaO to produce acid-soluble LiAlSiO4 and CaSiO3 concurrently. The addition of CaO reduced the melting temperature, which promoted the structural transformation of β-spodumene and further acid leaching. Then, the influences of various factors on lithium extraction were investigated by a single-factor test. A lithium leaching yield of 96.18% was obtained under optimum conditions: 20% CaO, roasting temperature of 1200 °C, holding time of 1.5 h, H2SO4 concentration of 120 g/L, liquid–solid ratio of 7:1 mL/g, leaching temperature of 80 °C and leaching time of 1.5 h. Finally, Li entered into leach liquor by the action of sulfuric acid, and the main components of the leach residue were silicate and calcium sulfate. Compared to the conventional acid approach, this method has a higher lithium recovery and lower energy and acid consumption (decrease by approximately 0.42 kg/ kg).

Extensive investigation on extraction and leaching kinetics study of Cu and Cr from spent catalyst using acetic acid.

The application of organic acids towards the extraction of both Cu and Cr from the Cu-Cr spent catalyst was investigated. A series of organic acid such as acetic acid, citric acid, formic acid, ascorbic acid and tartaric acid were adopted, and after screening, acetic acid showed a profound effect on dissolution of either of the metals over other green reagents. The spent catalyst was characterized by XRD and SEM-EDAX to confirm the existence of the oxide phase due to both Cu and Cr metals. For efficient dissolution of metals, the critical parameters such as agitation speed, acetic acid concentration, temperature, particle size, as well as S/L ratio affecting on it was systematically investigated. It was observed that at approximately 99.99% of Cu along with 62% of Cr was extracted at the optimised conditions (agitation speed: 800rpm, 1.0M CH3COOH, 353K temperature, particle size of (75-105) µm and S/L: 2% (W/V). The leach residue obtained after the first stage of leaching was analysed by SEM-EDAX and XRD, indicating no peaks due to the presence of Cu ensures complete dissolution of Cu at the optimum conditions. Further, to attain the quantitative leaching yield of Cr, the leach residue obtained after the first stage was sequentially investigated using varied acetic acid concentration and temperature. Leaching kinetics was established based on obtained results at the varied operating parameters, and it revealed support for fitting a model of the leaching data to the shrinking core chemical control model (R2 = 0.99) for both metals (Cu and Cr). The activation energy determined to be 34.05kJmol-1 and 43.31kJmol-1 for Cu and Cr, respectively, validates the proposed leaching kinetics mechanism.

Bridging Li-Ion Batteries and Fuel Cells: From Cathode Leaching Residue to an Atomic-Scale Catalytic System

Bridging Li-Ion Batteries and Fuel Cells: From Cathode Leaching Residue to an Atomic-Scale Catalytic System

Optimisation of extraction of valuable metals from waste LED via response surface method

AbstractThe valuable metals were separated and extracted from waste light-emitting diodes (LEDs) by pyrolysis and leaching process. About 98.16% Ga and 99.54% Y were recycled from the LEDs after the pyrolysis by sieving process in advance. The effects of various leaching conditions on the extraction of Fe, Cu and Ag were investigated by single factor experiments and response surface method. About 90.15% Fe was selectively extracted from the waste LEDs by H2SO4 leaching without oxidant, and 99.55% Cu and 99.36% Ag were recovered from the iron leaching residue by acid leaching with the addition of HNO3. The XRD and SEM−EDS analyses confirmed that the iron and copper were effectively extracted from the waste LEDs by the developed process.

Simultaneous Recovery of NH3–N and Removal of Heavy Metals from Manganese Residue Leachate Using an Electrodialysis System

The problem of high concentration of NH3–N and heavy metals in manganese residue leachate (MRL) needs to be solved urgently as it can harm the surrounding soil, water bodies, and even the ecological system. In this study, a novel electrodialysis system with a self-growing titanium dioxide nanowire (TiO2 NW) electrode is proposed to recover NH3–N and remove heavy metals from MRL. Plant growth experiments and ecotoxicity studies are used to evaluate the ecological risks of the reuse of recovered NH3–N. In the electrodialysis system with a proton membrane to separate the two chambers, 87%–97% removal of heavy metals and 95% recovery of NH3–N from MRL can be achieved. The obtained recovery solution from the cathode chamber can greatly promote the plant growth. The ecotoxicity experiment results further reveal that the recovered NH3–N can optimize the soil microbial community structure by promoting the reproduction of the genus Bacillus and thus improve soil fertility. This work can provide a new perspective on the harmless disposal and resource recovery of MRL.

Recycling of metallic values from discarded tantalum capacitors

ABSTRACT The generation of electronic waste generation has led to significant attention towards metal recovery from urban sources. Due to scarcity, finite resources, and geopolitical constraints, tantalum recycling from capacitors is essential. In this study, sequential separation involving the removal of tightly bound epoxy resin and metallic impurities is carried out. Pyrolysis as a pre-treatment and its response on phase transformation, resin decomposition and metal enrichment are investigated. Pyrolysis effectively liberates the tantalum–rich sintered core from outer resin which is followed by mild organic acid leaching. The manganese impurity was removed from the core to obtain Ta recovery of ∼94.8% with ∼96% purity in the leach residue. The separated resin component was subjected to conventional sink-float separation for the recovery of metallic values (silver, tantalum). It is found that 100 g (666 units) of Ta capacitors can yield 34 g of Ta, equivalent to 0.28 tons of primary ore.

A novel process for the treatment of steelmaking converter dust: Selective leaching and recovery of zinc sulfate and synthesis of iron oxides@HTCC photocatalysts by carbonizing carbohydrates

A large amount of converter dust (CD) is generated annually, posing serious environmental problems due to its zinc content. Moreover, zinc mainly exists in the form of inert ZnFe2O4 in CD, which negatively affects the leaching efficiency of zinc. On the other hand, the photocatalytic activity of hydrothermal carbonation carbon (HTCC) is restricted by its wide bandgap, poor charge-transfer ability, and inconvenience of recycling. This work presents an oxygen pressure leaching method to selectively leach Zn from CD. In this process, not only the decomposition of ZnFe2O4 is effectively promoted to increase zinc recovery, but also Fe2+ in the solution is skillfully oxidized and hydrolyzed to solid Fe(OH)SO4. Under the optimum conditions, the leaching efficiency of zinc reached 98.8%, and 86.3% of iron remained in the leach residue, realizing the one-step separation of zinc and iron. Furthermore, the leach residue was successfully applied to synthesize a magnetically recyclable iron oxides@HTCC composite photocatalyst.

Selective Sulfation Roasting for Cobalt and Lithium Extraction from Industrial LCO-Rich Spent Black Mass

The extraction of cobalt from secondary resources has become crucial, as cobalt has been identified as a strategically important and critical raw material due to the high risks of supply chain disruptions. In this work, selective sulfation roasting was investigated as a potential recycling strategy to extract cobalt and lithium from an industrial lithium cobalt oxide (LCO)-rich black mass. Additionally, the effect of graphite on metal extraction was studied. In the first set of experiments, the sieved black mass fraction containing both cathode and anode materials was directly roasted in a predetermined composition of gas mixtures of SO2, O2, and Ar for 1 h at 850 °C. The gas composition was determined from Kellogg’s diagram to allow for the selective sulfation of Co and Li. In another set of experiments, the carbon present in the black mass was first removed by roasting the material in Ar for 2 h and then in an Ar and O2 gas mixture for five hours at 600 °C. Afterward, selective sulfation roasting was performed in mixtures of SO2, O2, and Ar gas similar to the previous set of experiments. For comparison, similar experiments were performed at 800 °C. The sulfation roasted black mass was leached in water to study the efficiency of Co extraction into the solution. Interestingly, the presence of carbon was found to be beneficial for Co extraction. The extraction efficiency for the first case (with carbon present in the raw material) was observed to be more than three times higher than in the second case (with carbon removed) for sulfation at 850 °C. The extraction efficiency and purity of the extracted Co were found to be better for higher temperature sulfation roasting conditions due to faster reaction kinetics. It was also found that almost all of the Li could be recovered while extracting Co. The maximum efficiency of the extraction was 99.51% Li and 61.21% Co for roasting under a gas flow of 10% SO2-10% O2-Ar at 850 °C for 60 min. These results suggest that Co and Li can be selectively extracted from the black mass by sulfation roasting pre-treatment followed by leaching in water. In holistic processing, the leach residue can then be further subjected to battery metal processing by state-of-the-art methods.