Process For Recovery Of Metals Research Articles

Bioleaching of End-of-Life Printed Circuit Boards: Mathematical Modeling and Kinetic Analysis

This work reports a kinetic study of the bioleaching process for Cu extraction from waste printed circuit boards (WPCBs), using iron as an oxidant agent. The kinetic study considered both the Fe2+ oxidation by bacteria metabolism and the chemical reaction between Fe3+ and Cu within WPCBs. The model was composed of a system of three differential equations characterized by three dependent variables and seven parameters. The first equation describes the bacteria abundance trend, the second one represents the variation of Fe2+ concentration, and the third one focuses on the Cu extraction by the biogenerated Fe3+. The developed model was consistent with experimental data with an R2 higher than 0.97. The results showed that the bacteria metabolism was 1.8–2.5 times faster than the chemical reaction. The determined mathematical model, suitable for the implementation at an industrial scale, could be an important tool to predict the bioleaching mechanism in a metal recovery process.

The effect of increasing water content on transition metal speciation in deep eutectic solvents

A move towards the use of green solvents in metal recovery processes is going to be necessary for the development of a sustainable circular economy. This paper determines the effect of adding water to choline chloride based deep eutectic solvents on transition metal speciation, a common method for reducing their viscosity, using UV/Vis absorption spectroscopy. Even small amounts of water (< 5 %) were seen to cause a hypsochromic shift in UV/Vis spectra, indicating a change in metal speciation. In the choline chloride – urea solvent, the hydrolysis of the studied metals (V3+, Fe3+, Ni2+, Co2+, Cu2+) was observed. In the ethylene glycol and malonic acid systems precipitation was not observed, and Mx+ − H2O interactions were generally seen to dominate above ca. 30 % H2O. The presented results will impact metal recovery process design, where water additions to deep eutectic solvents to lower viscosity must be balanced with changes in metal speciation. This will allow for optimization of pumping systems whilst maintaining an effective process.

Characterization and recycling potential of the discarded cathode ray tube monitors

Abundantly available discarded cathode ray tubes are a serious threat to the environment and loss to resource conservation and therefore requiring immediate recycling efforts. In this study, extensive characterization of all parts of the discarded cathode ray tube was carried out using X-ray diffraction, thermo-gravimetric, X-ray photoelectron spectroscopy, Scanning electron microscope, and Energy Dispersive Spectroscopy. The detailed mass balance and the overall potential (market value calculations) of discarded cathode tubes as an urban source, and the techno-economic calculations were carried to provide guidelines for the development of recycling technology. Recycling techniques of cathode-ray tubes were reviewed, and a concise flow sheet for overall recycling was prepared for evaluation and assessment of recycling potential. The thermal response and dissociation kinetics of the phosphor were investigated, and the activation energy in the temperature range (600–930 °C) for thermal processing of phosphor was determined as 105.4 kJ/ mol. Effective recycling of cathode ray tube phosphor can yield 4.5 g of Y, Eu and, La metal values per 500 kg of discarded units with a market value of 835 INR and an overall market value of 115,870 INR ($1567.34). The different fractions of cathode-ray tube glass were recycled using a combination of the pyrometallurgical and hydrometallurgical processes for metal recovery. Recycling of different fractions of hazardous discarded cathode ray tubes is necessary and is beneficial for a circular economy for recovery of phosphor, copper, glass and coating material, plastics, and steel.

Supported liquid membrane with strip dispersion for recovering indium from etching solution of LCD industry: influence of factors on performance

Supported liquid membrane with strip dispersion (SLMSD) is a promising process for metal recovery from e-waste or waste streams because of many advantages such as the ability to combine extraction and stripping into one single step and thus have non-equilibrium mass transfer characteristics and maximum driving force. This paper investigated the effect of important factors on SLMSD performance to recover indium from etching solution such as: pH of feed solution, extractant (Di-(2-ethylhexyl) phosphoric acid (D2EHPA)) concentration, oxalic acid concentration. It was found that 99.5 % In3+ was removed from feed solution in about 20 minutes with high concentration factor (4.5) under suitable conditions (pH 1; 0.6M Di-(2-ethylhexyl) phosphoric acid (D2EHPA), 2 wt% oxalic acid).

Liquid metals dealloying as a general approach for the selective extraction of metals and the fabrication of nanoporous metals: A review

Liquid metal dealloying, a method of etching based on different solubilities of each component of the alloy into the liquid metal, has been extensively developed for metallurgical and structural materials applications. This review discusses the development on liquid metal dealloying for recycling alloy scraps and the fabrication of nano-porous materials. Extracting and recycling the valuable metal from alloy scraps by liquid metal dealloying can be more efficient and environmentally friendlier comparing to traditional alloy treatment processes for metal recovery. Manufacturing of nano-porous materials by liquid metal dealloying, not only can meet the need for efficient production of less noble metal nano-porous materials, but also can precisely control the morphology of the nano-pores by adjusting the dealloying conditions. This review demonstrates that liquid metal dealloying opens new avenues for the recycling of alloy scraps and for the fabrication of nano-porous metals, in addition to a wide variety of other promising applications.

Separation of Fe(III) and Al &lt;i&gt;via&lt;/i&gt; Tributyl Phosphate and 2-Octanol in the Comprehensive Recovery Process of Metals from Hydrochloric Acid Leaching Solution of Fly Ash

Separation of Fe(III) and Al &lt;i&gt;via&lt;/i&gt; Tributyl Phosphate and 2-Octanol in the Comprehensive Recovery Process of Metals from Hydrochloric Acid Leaching Solution of Fly Ash

A Study on Decreasing Heat and Metal Loss In Ladle In HC-FeCr Production

Yilmaden Holding is one of the important players in the chromium industry, company consists of 10 companies and operating in 7 different countries. High-quality high carbon ferrochromium (HQ HC FeCr) is produced in 3 different plants with 12 furnaces. These plants are Eti Krom Inc in Turkey, Vargon Alloys AB in Sweden, and Tikhvin Ferro Alloy in Russia. Tikhvin Ferro Alloy (TFZ) casting operations take place through refractory-lined ladles for a long time and also climate conditions are tough. Under these working conditions, some of the liquid metal solidifies in the ladle and a secondary process is needed. The secondary metal recovery process increases the production cost, that’s why ladle refractory design has critical importance to decrease solidified metal amount during casting. In this study, to decrease heat loss and reprocessed metal volume, a new refractory lining design to increase insulation capability of transfer ladle is studied. Theoretical heat loss calculation of existing design and new design are compared.

Intelligent optimization of bioleaching process for waste lithium‐ion batteries: An application of support vector regression approach

SummaryRecovery of toxic and vital metal from spent Li‐ion batteries is a vital problem in the recycling industry. The recycling processes such as bioleaching are much simpler and environment friendly but lack the required efficiency for metal recovery to prove the commercial feasibility of the model. This work focuses on increasing the efficiency of the bioleaching process by targeting its intermediate processes for maximum vital metal recovery. The intermediate process of biomass generation from Aspergillus niger fungus is targeted. The data from experimental design is modelled using support vector regression with v‐fold cross‐validation. The bioleaching process is optimized such that maximum biomass concentration is obtained for efficient and commercially viable metal recovery. The results are divided into four sections, each addressing an important issue of the recycling process mechanism. The generated model is found to have good stability and accurate process mechanism predictability. Global sensitivity and interaction analysis is employed for efficient weighted optimization. The model generated trends and optimization results are verified through the profiling curve as well as past literature experimental data. This work reports the maximum biomass concentration of 25 g/L. The model employed is stable and efficient, reaching a stable optimized value under 300 iterations. The optimized input parameters values obtained are 144.39 g/L, 1.29% v/v, 6.70, 1513.05 ppm, 4989.79 ppm, 2094.22 ppm, 347.57 ppm and 2.37 for sucrose concentration, inoculum size, initial pH, oxalic acid, gluconic acid, malic acid, citric acid concentration and final pH, respectively.

Recovery of Nickel and Cobalt By Electrowinning from Spent Lithium-Ion Batteries Using Molten Salt Electrolytes

Electrodeposition of metals is of wide interest with application in several fields such as electroplating, electrorefining and electrowinning (EW). Particularly, electrowinning is used in the fabrication of commercially pure copper and zinc, with approximately 20% of the world refined copper (Cu) produced by this process. One of the main advantages of EW is the high purity achieved of the final product. Electrowinning has been implemented recently as one of the final steps in the hydrometallurgical recycling process of lithium-ion batteries (LIBs) to recover some of the valuable metals present in the battery such as cobalt and nickel.This work describes advances in the recovery of metals from spent LIBs, by using a two-phase molten salt of sodium borate/sodium chloride at high temperature. The study takes advantage of the versatility of the molten salts used as electrolytes - sodium borate’s easiness for dissolving metal oxides, and sodium chloride as the chosen electrolysis media. For the study, two different cathode chemistries were used, NMC 111 and NCA. The electrolytic cell comprises of a gas-tight vertical tube furnace under argon atmosphere, possible in a single-vessel configuration by utilizing the immiscibility of the two liquid phases used (see Figure 1). The experiments are conducted in a three-electrode setup, using graphite (C) as counter electrode, and tungsten (W) as pseudo-reference and working electrodes. The process operates within the temperature range of 800-900℃, where both salts are in liquid state. The reduction potentials were applied stepwise using chronoamperometry to record the current output. Cyclic voltammetry was used beforehand to corroborate the reduction potential for each metal, and to compare it to the reported ones by Amietszajew et. al. The plating potentials and recovered metals quality are reported (see Figures 2-3), indicating successful process proof-of-concept.Evaluation of the energy efficiency of the process and purity of the deposited metals is compared with the current commercial processes for metal recovery employed to recycle batteries from portable devices. The system demonstrates stability, and gives the possibility to be used in joint with other metal recycling sources and process. It has the possibility to solve some of the issues related to the hydrometallurgical methods including significant amounts of water waste, sulphates by-products presence and toxic acids resulting in highly detrimental effects on the environment. The reduction in energy consumption and hazardous gases generation that the common pyrometallurgical process adds to the advantages. Furthermore, the method developed is inclusive of a range of metals, which is of high importance considering the growing and future complexity of the battery waste stream. Figure 1

Feasible route for the recovery of strategic metals from mixed lithium-ion batteries cathode materials by precipitation and carbonation

• Two recycling routes with high Li and Co recovery are designed and compared. • Three scenarios were compared to achieve an economically feasible recycling path. • Detailed breakdown of costs and gains in each step were analyzed. • Nano-sized Li 2 CO 3 and Co was recovered with high purity. Recycling routes and orientations set the tone for the feasibility of lithium-ion batteries (LIBs) recycling. An economically feasible hydrometallurgical route for the recycling of strategic metals from LIBs cathode materials was in great need both in the sense of achieving the sustainable development of clean energy and emissions reductions. Three scenarios with routes emphasis on higher lithium and cobalt recovery and orientations incline towards high overall recovery and profit, respectively, were compared, i.e., scenarios A and B with the same orientation (high overall recovery) in different routes (higher lithium and cobalt recovery, respectively), scenario B and C with same routes (high cobalt recovery) in different orientations (high overall recovery and profit, respectively). With the assistance of thermodynamic simulations and profit calculations, three scenarios were tested for recycling 1 Kg of spent cathode materials. The highest leaching and Li 2 CO 3 precipitation ratio were achieved in scenario A, followed by scenario B with the highest cobalt recovery ratio, however, the optimum profit was achieved in scenario C with the lowest costs. A comparison among scenarios A, B, and C indicate that a profit-oriented strategic metals recovery process is more reasonable for LIBs recycling.

Carbonization processing of bauxite residue as an alternative rare metal recovery process

A prerequisite for commercial production of rare metals is a continuous effort given to developing knowledge-intensive recovery and refining techniques. Commonly known natural raw materials and conventional processing techniques, which are based on initial acid activation and recovery of minerals, as well as selective recovery of the target component (i.e. by sorption and extraction) cannot always ensure sufficient productivity or cost-effectiveness. This paper considers certain aspects of continued research in this area, which would require novel techniques. Such techniques should be based on new approaches allowing for the use of alternative raw materials to produce valuable rare metals on a cost-effective basis. It is demonstrated that red mud, i.e. waste material generated by bauxite industry and rich in scandium and other rare metals, can serve as such alternative source material. The paper describes the results of a study that looked at finding an optimum carbonization process for red mud that would ensure a consistent and predictable complexing process with regard to certain components. The paper also examines the environment in which soluble carbonate complexes can be stabilized and concentrated in the pregnant solution before the primary scandium-bearing concentrate can be recovered. The authors identified target parameters that determine enhanced filtration properties of carbonized slurry to ensure complete separation of the pregnant solution from the dehydrated (to the residual moisture content of 18%) carbonized residue. The paper highlights some positive factors of the carbonization process which enable a comprehensive utilization of alumina production waste. They include a long-term sequestration of carbon dioxide in the air and modified physical and chemical properties of red muds. This makes carbonized muds more compactable and thus more suitable for transportation and minimizes waste disposal hazards. The experimental research was carried out in conformance with the governmental assignments of the Institute of Solid State Chemistry of the Ural Branch of the Russian Academy of Sciences and Saint-Petersburg Mining University.

Stabilizing Arsenic in Copper Heap Leaching Residues

The need to sustainably produce raw materials encourages mining companies to develop and incorporate new economically and environmentally efficient processes. Therefore, there is a need to investigate the behavior and stabilization of hazardous elements present in effluents from metal recovery processes such as arsenic. This study evaluates the incorporation of an effluent solution from a copper smelter that is to be treated in a copper hydrometallurgical plant (heap leaching). The treatment is applied to recover compounds of interest such as copper, acid and water, in addition to confining impurities as stable residues in the leach residues. Here, we assess the capacity of the mineral to retain arsenic. To do this, a mixed solution of effluent and process solution was prepared, with a concentration of 1 g/L of arsenic. The solution was irrigated in leach columns loaded with a heap mineral with varying pH levels (0.8; 1.5 and 2) and solution potentials (510 and 540 mV). The concentrations of arsenic and iron in the solution and in the solid residues were measured to determine the capacity of the mineral to retain arsenic and how it was retained. The pH level plays an important role since, at a higher pH, the presence of arsenic and iron in the solution decreases, therefore increasing in the solid residue. Finally, a retention of 57% of arsenic is reached at pH 2. The characterization of the residues by scanning electron microscopy (SEM) confirms that arsenic is associated with Fe, S and O, forming ferric arsenates, while an X-Ray analysis identifies the arsenic compounds as crystalline scorodite.

Cleaner recovery of multiple valuable metals from cyanide tailings via chlorination roasting

ABSTRACT Recovery of valuable metals is hindered by sulfur in cyanide tailings. In this work, a process for the clean recovery of multiple valuable metals through chlorination roasting was proposed. HSC software was used to find that the process of dissociation of chlorides is further accelerated by sulfur in the tailings. Experiments were carried out to study temperature variables and chlorinated agent variables. The optimum conditions were identified to be a CaCl2 dosage of 4%, roasting temperature of 1323 K, achieved maximum recovery of 84% of Au, 71% of Ag, 72% of Cu, 92% of Pb, and 69% of Zn.

Highly efficient recovery of molybdenum from spent catalyst by an optimized process

ABSTRACT Disposal of spent catalyst in an economical and green way has become a great concern for industrial production. We developed a process including acid leaching, solvent extraction and stripping in order to recycle spent catalyst. In this study, we conducted selective recovery of molybdenum through focus on finding an optimized extraction and stripping process by comparing different extractants and stripping agents. To separate molybdenum from other metals efficiently and figure out the mechanism of extraction process, the five different extractants of methyl trioctyl ammonium chloride, tri-n-octylamine, tris (2-ethylhexyl) amine, bis (2-ethylhexyl) phosphate, and tributyl phosphate with different functional groups were examined; the extraction ability and extraction mechanism of these five extractants were systematically studied under the same system for the first time. It was found that more than 98% of the molybdenum could be extracted with an organic phase consisting of tri-n-octylamine or methyl trioctyl ammonium chloride under the optimal conditions. The result indicated that the tri-n-octylamine and methyl trioctyl ammonium chloride possess excellent molybdenum extraction ability, the extraction capacity of the rest extractants was in the order of bis (2-ethylhexyl) phosphate > tris (2-ethylhexyl) amine > tributyl phosphate. In the stripping process, NH4OH, NaOH, and H2SO4 were chosen as stripping agent to strip the molybdenum from the loaded tri-n-octylamine organic phase. The stripping ability of the three studied stripping agents was in the order NaOH > NH4OH > H2SO4. The Fourier transform infrared (FTIR) spectra showed that the structure of the tri-n-octylamine organic phase was stable during the extraction and stripping process. Results showed that molybdenum could be highly and efficiently recovered by optimized extraction and stripping process. Implications: A series of different extractants and stripping agent have been systematically studied in order to compare their extraction and stripping ability under the same system. Based on the obtained results, an optimized extraction and stripping process was proposed to recycle molybdenum from spent catalyst efficiently. It is possible to dispose spent catalysts in an economic and environmental way by this developed metal recovery process.

A promising selective recovery process of valuable metals from spent lithium ion batteries via reduction roasting and ammonia leaching

In this study, a promising process has been developed for selective recovery of valuable metals from spent lithium ion batteries (LIBs). First, reduction roasting which used spent anode powder as reduction agent and water immersion are applied to preferentially recover lithium. Subsequently, an ammonia leaching method is adopted to eff ;ectively separate nickel and cobalt from water immersion residue. Results indicate that Li2CO3, (NiO)m·(MnO)n, Ni, Co are the ultimate reduction products at 650 °C for 1 h with 5% anode powder. 82.2 % Li is preferentially leached via water immersion after reduction roasting and Li2CO3 products are obtained by evaporation crystallization. Thermodynamics shows that reducing ammonia leaching is feasible for water immersion residue. Amounts of 97.7 % Ni and 99.1 % Co can be selectively leached by NH3·H2O and (NH4)2SO3 while Mn remain in the residue as (NH4)2Mn(SO3)2·H2O, (NH4)2Mn(SO4)2·6H2O and (NH4)2Mn2(SO3)3 under the optimized conditions. Ammonia leaching kinetic show the activation energy of Ni and Co is 84.44 kJ/mol and 91.73 kJ/mol, which indicate the controlling steps are the chemical reaction. Summarily, the whole process achieves the maximum degree of selective recovery and reduces the environmental pollution caused by the multistep purification.

Electrochemical-Osmotic Process for Simultaneous Recovery of Electric Energy, Water, and Metals from Wastewater.

A highly-efficient, autonomous electrochemical-osmotic system (EOS) is developed for simultaneous recovery of electric energy, water, and metals from wastewater. We demonstrate that the system can generate a maximum electric power density of 10.5 W m-2 using a spontaneous Fe/Cu2+ galvanic cell, while simultaneously achieving copper recovery from wastewater. With an osmotic pressure difference generated by the deployed electrochemical reactions, water is osmotically extracted from the feed solution with the EOS at a water flux of 5.1 L m-2 h-1. A scaled-up EOS realizes a power density of 105.8 W per m-3 of treated water to light an LED over 24 h while also enhancing water extraction and metal recovery. The modularized EOS obtains ultrahigh (>97.5%) Faradaic efficiencies under variable operating conditions, showing excellent system stability. The EOS is also versatile: it can recover Au, Ag, and Hg from wastewaters with simultaneous electricity and water coproduction. Our study demonstrates a promising pathway for realizing multiresource recycling from wastewater by coupling electrochemical and osmosis-driven processes.

Indirect (hydrogen-driven) electrodeposition of porous silver onto a palladium membrane

Hydrogen permeation through a pure palladium film (25 μm thickness, optically dense) is employed to trigger electron transfer (hydrogen-driven) reactions at the external palladium | aqueous electrolyte interface of a two-compartment electrochemical cell. Two systems are investigated to demonstrate feasibility for (i) indirect hydrogen-mediated silver electrodeposition with externally applied potential and (ii) indirect hydrogen-mediated silver electrodeposition driven by external formic acid decomposition. In both cases, porous metal deposits form as observed by optical and electron microscopies. Processes are self-limited as metal deposition blocks the palladium surface and thereby slows down further hydrogen permeation. The proposed methods could be employed for a wider range of metals, and they could provide an alternative (non-electrochemical or indirect) procedure for metal removal or metal recovery processes or for indirect metal sensing.Graphical abstract

Dissolution of Silver and Gold with Sodium Hypochlorite and Hydrochloric Acid in Refractory Minerals (Mangano-Argentiferous)

The present study examined a process for precious metal recovery (silver and gold) from difficult minerals which exhibit refractory characteristics to cyanidation and ammonium thiosulfate leaching (low extraction and high consumption of leaching agent). It is well known that mangano-argentiferous minerals are mainly composed of manganese, silver, gold, and iron. In this research, a mineral sample from Monte del Favor mine, located in Hostotipaquillo, Jalisco, Mexico, was physically and chemically characterized by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), fire assay, and atomic absorption spectroscopy (AAS). Two-stage leaching was carried out: first to eliminate manganese from the sample using sodium sulfite (Na2SO3) as a reductive reagent and sulfuric acid (H2SO4) and a second stage to dissolve silver and gold with sodium hypochlorite (NaClO) and hydrochloric acid (HCl); the results show extraction around 96% for Mn and 98.73% and 83% of Ag and Au, respectively. The usefulness of high acidity and Na2SO3 to obtain good results in Mn and Ag leaching is discussed along with the roles that HCl and NaClO play in the dissolution of Ag and Au values.

Stirred-tank and heap-bioleaching of shredder-light-fractions (SLF) by acidophilic bacteria

End-of-life vehicles are usually crushed in large scaled shredders in order to increase the surface area for further processing. During the shredding process, the so-called shredder-light-fraction (SLF), containing mainly plastics and other synthetic polymers, is discharged. However, this fraction still contains up to 20% metals such as iron (Fe), copper (Cu), nickel (Ni) and zinc (Zn), making them an interesting substrate for bioleaching and source of high-value metal traces. To develop a bioleaching process for metal recovery from shredded fractions, two experimental approaches including a heap- and a stirred-tank reactor were tested. The acidophilic, iron- and sulfur-oxidizing bacteria Acidithiobacillus ferrooxidans and the iron-oxidizing bacteria Leptospirillum ferrooxidans were investigated as pure and co-culture for their ability to solubilize trace metals. A. ferrooxidans proofed to be the more suitable bioleaching organism resulting in leaching efficiencies of up to 100% for Zn and Ni in batch experiments. Furthermore, in the stirred-tank reactor using A. ferrooxidans about 100, 80 and 55% of Cu, Zn and Ni have been recovered from 50 g l−1 of the SLF, respectively. Bioleaching of 3000 g SLF in the heap-reactor resulted in a recovery of about 100% Zn, 60% Cu and ~ 55% Ni after 33 days without the need of external sulfuric acid addition for pH regulation. The high leaching efficiencies in both experimental setups confirmed the potential of bioleaching for a sustainable metal recovery from shredder residues (i.e. SLF) making it a profitable, eco-friendly alternative to conventional chemical leaching processes.

Interaction among branched polyethylenimine (PEI), sodium dodecyl sulfate (SDS) and metal cations during copper recovery from water using polymer-surfactant aggregates

The application of polymer–surfactant aggregates (PSAs) to recover heavy metal ions from water is a novel treatment process for aqueous metallic effluents. To better employ this strategy, branched polyethylenimine (PEI), sodium dodecyl sulfate (SDS) and copper ions were selected to investigate their interaction in water and to improve the recyclable PSAs process for metal removal and recovery. Electrostatic association between PEI and SDS caused the formation of PSAs, and the addition of SDS to a partially protonated PEI solution caused a pH increase; however, re-dispersal of PSAs could be achieved via an increase in pH. Precipitation of PSAs depended on pH, SDS/PEI concentration ratio and the total concentration of PEI; the optimal SDS/PEI ratio decreased as pH increased, and a higher concentration of PEI showed a greater potential to precipitate. PEI formed a strong complex with Cu2+, with the most stable complex at a PEI/Cu chelation ratio of 4. Acidification decreased the chelation capacity of PEI to Cu2+, because of the competition from protons for amino groups. Complexation with Cu2+ in turn reduced the proton buffer capacity of PEI in a non-acid solution. The removal of Cu2+ increased by increasing the total PEI concentration, or by increasing pH from 1 to above 4. Ionic strength and hardness had no marked effect on Cu2+ removal using the PSAs process. Following the initial interaction among PEI, SDS and Cu2+, the Cu2+ could then be released from the PSAs by acidification and the reuse of the PSAs material could be achieved by alkalization. Copper removal and recovery were still up to 98 % and 88 % after three reuse cycles of the PSAs process, respectively.