Electrochemistry during efficient copper recovery from complex electronic waste using ammonia based solutions

Leaching selectivity during metal recovery from complex electronic waste using a hydrochemical process is always one of the generic issues. It was recently improved by using ammonia-based leaching process, specifically for electronic waste enriched with copper. This research proposes electrodeposition as the subsequent approach to effectively recover copper from the solutions after selective leaching of the electronic waste and focuses on recognising the electrochemical features of copper recovery. The electrochemical reactions were investigated by considering the effects of copper concentration, scan rate and ammonium salts. The diffusion coefficient, charge transfer coefficient and heterogeneous reaction constant of the electrodeposition process were evaluated in accordance with different solution conditions. The results have shown that electrochemical recovery of copper from ammoniabased solution under the conditions of selective electronic waste treatment is charge transfer controlled and provide bases to correlate the kinetic parameters with further optimisation of the selective recovery of metals from electronic waste.

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Modeling of Boehmite Leaching from Actual Hanford High‐Level Waste Samples

Abstract

The Department of Energy plans to vitrify approximately 60,000 metric tons of high level waste sludge from underground storage tanks at the Hanford Nuclear Reservation. To reduce the volume of high level waste requiring treatment, a goal has been set to remove about 90 percent of the aluminum, which comprises nearly 70 percent of the sludge. Aluminum in the form of gibbsite and sodium aluminate can be easily dissolved by washing the waste stream with caustic, but boehmite, which comprises nearly half of the total aluminum, is more resistant to caustic dissolution, and requires higher treatment temperatures and hydroxide concentrations. In this work, the dissolution kinetics of aluminum species during caustic leaching of actual Hanford high level waste samples is examined. The experimental results are used to develop a shrinking platelet model that provides a basis for the prediction of dissolution dynamics from a known process temperature and hydroxide concentration. This model is further developed to include the effects of particle size polydispersity, which is found to strongly influence the rate of dissolution. Two identical parameters for this model are used to describe leaching data from two sets of leaching results. When compared to other common monodisperse shrinking particle models, this result suggests a more physically meaningful model.     

Statistical Evaluation of Factors Affecting the Leaching Process of Waste Electrical and Electronic Equipment using Sodium Persulfate

Recycling of waste electrical and electronic equipment (WEEE) is important not only to reduce the amount of waste requiring treatment, but also to promote the recovery of valuable materials. Implementation of the European Directive on WEEE and recycling targets imposed in the European Union will require new processes to be developed and applied to recover metals from WEEE. This study aims to provide an alternative process for the dissolution of metals from WEEE which contains Cu and Zn based on our previous research. The effects of leaching parameters, such as temperature, Na₂S₂O₈ concentration, and leaching time, were separately investigated on leaching of copper, zinc, and brass (alloy composition ?35% zinc and 65% copper) in Na₂S₂O₈ solution (0.1, 0.2 and 0.3 M). Box–Behnken experimental design (BBD) method was used to determine the number and the condition of necessary leaching experiments. Statistical analysis of variance (ANOVA) was performed to see whether process parameters such as leaching time, temperature, and oxidant concentration are statistically significant or not on the leaching performance. Results show leaching time as the most influential factor in the dissolution process, for the first six models. Two extended models have been developed to optimize the parameters of the investigated process. In these models, we consider the metal composition as a model input next to the earlier investigated parameters. Optimal condition for maximum copper and zinc dissolution in Na₂S₂O₈ environment can be found for parameter values: temperature 45°C, oxidant concentration 0.1 M and leaching time 35 min.     

酸浸-置换工艺回收废甲醇催化剂中铜的研究

对酸浸-置换工艺回收废甲醇催化剂中的铜进行了研究。酸浸实验中考察了酸浸时间、液固比、酸浸温度对铜浸出量的影响;置换实验中考察了pH、置换时间、置换温度对铜回收量的影响。研究表明,酸浸-置换工艺回收废甲醇催化剂中铜的最佳工艺条件为：酸浸时间80 min、液固比20：1、酸浸温度80℃、置换pH=5、置换时间60 min、置换温度65℃。每克废甲醇催化剂可回收铜0.4531 g。     

Optimization of gold recovery from copper anode slime by acidic ionic liquid

Hydrometallurgical gold recovery from primary or secondary sources is mainly based on a cyanide process, which is very dangerous for the environment due to the high toxicity levels. In view of the environmental effect, the present study proposes a new green solvent called 1-ethyl-3-methyl-imidazolium hydrogen sulfate (EmimHSO₄) ionic liquid (IL) to recover gold from copper anode slime (CAS). The optimum leaching conditions for maximizing gold recovery were determined by orthogonal array (OA) of Taguchi’s experimental design method. OA L₁₆ (4⁴) including four parameters with four levels each, was used to examine the effects of IL concentration (20%, 40%, 60%, 80% v/v), temperature (25, 50, 75, 95 °C), time (½, 1, 2, 4 h) and solid/liquid ratio (1/10, 1/15, 1/20, 1/25 g/mL) on leaching efficiency of the gold recovery. Statistical analysis of variance (ANOVA) was used to determine the relevance between experimental conditions and gold recovery. The selective leaching tests results showed that gold recovery up to 89.07% was attained on laboratory scale under the optimum leach conditions: 80% IL concentration, 75 °C, 4 h and 1/25 g/mL solid/liquid ratio. According to these results, EmimHSO₄ IL provides a very good ambiance for the oxidative leaching of gold and can be offered as an alternative leaching agent instead of harmful cyanide-based solvents.     

Extraction of Hydrocortisone from the Fermentation Liquor with Annular Centrifugal Contactors

Abstract

A continuous countercurrent extraction process for the recovery of hydrocortisone from the fermentation liquor has been developed with annular centrifugal contactors. When the hydrocortisone was extracted from the fermentation liquor with the butyl acetate, the distribution ratio increased with increase of the hydrocortisone concentration in the equilibrium aqueous phase. Both the laboratory tests and the plant tests have been finished with Φ20 mm and Φ230 mm annular centrifugal contactors respectively. In the laboratory tests, when the rotor speed was 3400～4200 r/min, the fermentation liquor flow was 30～50 mL/min and the phase ratio (V_O/V_A) was 0.36～0.50, the percent recovery of hydrocortisone was higher than 92%. In the plant tests, when the rotor speed was 2000 r/min, the fermentation liquor flow was 2000 L/h and the butyl acetate flow was 1000 L/h, the percent recovery of hydrocortisone was about 96.5～98%.     

Dried waste activated sludge as biosorbents for metal removal: adsorptive characterization and prevention of organic leaching

Dried waste activated sludge was used for copper removal from simulated waste water in this study. Unconditioned activated sludge (UAS) bound up to 35 mg Cu g^?1, although there was significant leaching of organic material. Organic and copper leaching from the UAS increased significantly as the pH was reduced. Immobilization of UAS by sodium and calcium alginate was utilized in order to overcome the leaching problems, but reduced the adsorption capacity. Based on metal removal and organic leaching, calcium alginate‐conditioned UAS (CACAS) was found to be the most suitable sorbent for copper removal. Kinetic experiments showed that copper removal by both sodium alginate‐conditioned UAS (SACAS) and CACAS was faster than that by activated carbons, but slower than most of the other biosorbents described in the literature. FTIR spectroscopy identified a number of atomic groupings and structures in UAS relevant to copper adsorption. It suggested that hydrogen ions are replaced with copper ions. The Freundlich equation fitted the experimental isotherms better than the Langmuir equation. A computational model based on adsorption isotherm, external mass transfer and diffusion processes successfully described the kinetics of copper ion removal and suggested that the biosorption kinetics was controlled by mass transfer. © 2002 Society of Chemical Industry     

废电解液净化除杂制取硫酸铜研究

介绍了废电解液净化除杂制取硫酸铜的新工艺。在废电解液中加入CH80和CH6 4试剂进行净化除杂 ,净化液进行化学浓缩、结晶 ,便可得到CuSO4 ·5H2 O产品 ,铜的回收率大于 94 %,硫酸铜含量 96 %以上 ,达到GB4 37— 80一级标准     

Recovery of Nonferrous Metals from Metal Finishing Industry Wastes

Abstract

Flexible schemes have been devised for recovery of nonferrous metals (copper, chromium, nickel and zinc) from metal finishing industry waste acids and hydroxide sludges. Evaluations conducted with bench scale experimentation established technical feasibility for adaptations of solvent extraction, precipitation and ion exchange separation processes. It was demonstrated with industrial waste samples that by tailoring several separation stages appropriate for specific waste compositions for complex mixtures of widely varying character that efficient separations can be achieved for copper, chromium, nickel or zinc from contaminant metals such as aluminum, chromium or iron.     

Boehmite Actual Waste Dissolution Studies

Abstract

The U.S. Department of Energy plans to vitrify approximately 60,000 metric tons of high-level waste (HLW) sludge from underground storage tanks at the Hanford Nuclear Reservation. To reduce the volume of HLW requiring treatment, a goal has been set to remove a significant quantity of the aluminum, which comprises nearly 70 percent of the sludge. Aluminum is found in the form of gibbsite, sodium aluminate and boehmite. Gibbsite and sodium aluminate can be easily dissolved by washing the waste stream with caustic. Boehmite, which comprises nearly half of the total aluminum, is more resistant to caustic dissolution and requires higher treatment temperatures and hydroxide concentrations.

Samples were taken from four Hanford tanks and homogenized in order to give a sample that is representative of REDOX (Reduction Oxidation process for Pu recovery) sludge solids. Bench scale testing was performed on the homogenized waste to study the dissolution of boehmite. Dissolution was studied at three different hydroxide concentrations, with each concentration being run at three different temperatures. Samples were taken periodically over the 170 hour runs in order to determine leaching kinetics. Results of the dissolution studies and implications for the proposed processing of these wastes will be discussed.     

Liquid-Membrane-Permeation and Its Experiences in Pilot-Plant and Industrial Scale

Abstract

Emulsion-Liquid-Membrane-Perraeation (LMP) is an operation for the recovery of several harmful substances from industrial waste water streams. Within this process the substance is separated from the waste water and enriched by a factor up to 1000 in the receiving phase depending on the process conditions. The largest experimental experiences are in the separation of Zn, Cd, Pb, Cu, Ni, NH₃ and phenol from aqueous solutions.     

Hydrometallurgical Treatment of Zinc Waste Dusts

Abstract

Hydrometallurgical separation processes offer attractive potential for recovery of marketable zinc from industrial wastes. In view of the importance of having a supply of zinc from a diversity of sources to supplement zinc imports, it is useful to assess the applicability of available separation technology. A brief review is presented of applications of several separation processes which have been applied to a variety of zinc waste dusts. In addition the results of bench scale tests are presented for a technically feasible scheme applied to a high zinc content fly ash from a waste to energy power plant which show a potential of providing a marketable zinc recovery product.     

Silver-catalyzed bioleaching for raw low-grade copper sulphide ores

This research was conducted to investigate the biooxidation and copper dissolution from raw low-grade refractory copper sulphide ores located in the Xinjiang Autonomous Region of China using adapted Thiobacillus ferrooxidans bacteria. In order to accelerate the bioleaching rate, the adapted mixed bacteria and silver ion catalyst were tested in the leach columns at laboratory scale. The overall acid consumption was 4.3 kg sulphuric acid per kg of dissolved copper and was linearly related to the percent copper dissolution. The calculated copper dissolution rates obey the Shrinking Core Model. The relative activation energy of the whole biooxidative leaching stages was calculated to be 48.58 kJ/mol.     

Separation and recovery of copper from waste printed circuit boards leach solution using solvent extraction with Acorga M5640 as extractant

Waste printed circuit boards (WPCBs) have received extensive attention in recent years because of its harmfulness and resource. In this work, two-step leaching process was carried out by using steel pickling waste liquor (SPWL) as the leaching agent. The leaching solution contains a variety of metals, especially iron, which will have an effect on the recovery of copper. Acorga M5640 (M5640) extractant with a kerosene diluent was used to recover copper from WPCBs leach solution, and the separation factor is adopted to analyze the effects of these metal ions. The effect of different parameters such as pH of aqueous phase, phase ratio (O/A), M5640 concentration, contact time as well as the concentration of H₂SO₄ as stripping reagent were investigated. Over 90.0% copper was extracted with pH 1.1, phase ratio (O/A) 1/1, M5640 concentration 16%, contact time 3 min at room temperature. For the stripping process, the 60 s contact time and 2.5 mol/L H₂SO₄ concentration are suitable with 90.0% stripping percentage of copper. Copper extraction isotherm accords with Langmuir isotherm equation and the results show that iron is the most influential metal ion for copper extraction, which will reduce the theoretical saturation of the extractant. The extractant M5640 has excellent reuse performance and can be recycled more than 10 times, which demonstrated M5640 has the industrial application value in the extraction of copper from WPCBs leach solution.     

废阴极炭碳热还原法贫化艾萨铜熔炼渣

以电解铝工艺所产生废阴极炭块为还原剂,可实现艾萨铜熔炼渣中铜的有效火法贫化回收。结合热力学分析,研究了废阴极炭加入量、还原温度、保温时间和CaO添加量对艾萨铜渣中铜贫化回收的影响规律。结果表明,废阴极炭添加量2.0%、还原温度1300℃和保温时间60 min条件下,铜贫化回收率可达98.24%。废阴极炭中F可转移并以CaF2形式固定在贫化尾渣中,尾渣中F?和CN?的毒性浸出浓度远低于国家允许排放标准,实现了艾萨铜熔炼渣铜的高效贫化回收和废阴极炭的资源化利用。     

CSA Continuous Countercurrent Ion Exchange (CCIX) Technology

Abstract

The CSA-CCIX concept started at ORNL in 1951. It has been adapted to a wide variety of applications worldwide, in water and waste water treatment, fertilizers, hydrometallurgy, and general chemical processing. Unique features and how it works are described. Two extreme applications are described in detail. One is for the extraction of trace amounts of uranium from a copper leach, at 37.85m³/min (10,000 gpm) where very high throughput rates are emphasized. The other is for Acid Retardation, where a strong acid waste is purified and recovered. The feed processing rate here is much lower than the resin rate.     

Elimination of Vanadium and Arsenic from VKCs Catalysts

Abstract

Vanadium and arsenic eliminations from an alkaline leaching solution of spent VKCs catalysts were studied. To this end, several commercial resins or polymers synthesized in the laboratory were evaluated in a solid–liquid batch extraction. Conditions for an effective extraction of vanadium and arsenic were determined. An extraction process, using a glass column, is described for the recovery of the vanadium. The elimination of arsenic by precipitation is proposed.     

Economic and environmental applications for recent innovations of nonferrous metallurgy in some industrial nations

As ore grades drop at today’s large mines, and environmental regulations for waste discharges increase, economics drives new recovery innovations. This paper describes some technological advances in the recovery processes for copper, gold, silver, lead and zinc. It does not discuss pyrometallurgy. Korea, like many nations with industrial economies, consumes large amounts of these metals, and is dependent on overseas suppliers for nearly its entire supply. This paper also discusses how technology for recovery of metal now in Korea, for example from existing wastes, is important. Improved reagents for both leaching and froth flotation of copper minerals, plus bio-oxidation and pressure autoclaving for gold have improved metal recovery. Copper recovery by SX-EW is expanding rapidly, and the method is also commercial for zinc. Biooxidation of encapsulating waste materials and, in some instances, of the desired metal has reached commercial scale. Pressure leaching on a large scale solves specific problems for several metals. Improvements in gold and silver cyanidation include variants of activated carbon adsorption from solution. Zinc and lead still largely depend on flotation for the treatment of ores. However, innovation in hydrometallurgical extraction has been spurred by environmental concerns. Computer modeling and process control worldwide have likely led to the largest improvements in recovery. The limited availability of land, clean water and sites for waste disposal in many countries affects the economics of re-treatment of existing wastes. Some of the new technologies could be combined, for example in modular plants that can be moved between reclamation sites to economic advantage on the Korean Peninsula. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8-10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

OPTIMIZATION OF LEACHING OF COPPER FROM OXIDIZED COPPER ORE IN NH3-(NH4)2SO4 MEDIUM

Studies were carried out for selective leaching of Cu with simultaneous avoidance of iron dissolution during leaching of oxidized copper ore in an aqueous NH₃-(NH₄)₂SO₄ system. The effects of leaching parameters, such as ammonia concentration, ammonium sulphate concentration, leaching time, and solid-to-liquid ratio, were investigated on leaching of copper. A 2ⁿ factorial experimental design method in the dissolution experiments was used. In addition, the “Steepest Ascent” method was also applied to determine the optimum leaching conditions. It was observed that the most effective parameters on the leaching of copper were ammonia concentration and leaching time. Only 0.17% of iron in ore was dissolved in ammonia and ammonium sulphate medium. The optimum conditions established for maximum copper recovery were: ammonia concentration 2.824 mol L^?1, ammonium sulphate concentration 0.236 mol L^?1, solid-to-liquid ratio 0.167 g mL^?1, leaching time 2 h. Fixed parameters chosen in the experiments were: room temperature, average particle size 2.8 mm, stirring speed 500 rpm. Under the optimum conditions established for maximum copper recovery, the percentage of leached copper was 98.87.     

WASTE TREATMENT AT THE RADIOCHEMICAL ENGINEERING DEVELOPMENT CENTER

ABSTRACT

At the Radiochemical Engineering Development Center (REDC), irradiated targets are processed for the recovery of valuable radioisotopes, principally transuranium nuclides. A system was recently installed for treating the various liquid alkaline waste streams for removal of excess radioactive contaminants at REDC. Radionuclides that are removed will be stored as solids, and thus the future discharge of radionuclides to liquid-low level waste tank storage will be greatly reduced. The treatment system is of modular design and is installed in a hot cell at REDC, where preliminary testing is in progress. The module incorporates the following: (1) a resorcinol-formaldehyde resin column for cesium removal, (2) a cross-flow filtration unit for removal of rare earths and actinides as hydroxide, and (3) a waste solidification unit. Process flowsheets for operation of the module, key features of the module design, and its computer-assisted control system are presented. Good operability of the cross-flow filter system is mandatory to the successful treatment of REDC wastes. Results of tests to date on the operation of the filter in its slurry collection mode and its slurry washing mode are presented. These tests include the effects of entrained organic solvent in the waste stream to the filter.