• Resources Recycling
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• v.28 no.5
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• pp.68-73
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• 2019

Ilmenite is one of the principal ores for the production of titanium dioxide. To produce titanium dioxide with purity higher than 99.9% from ilmenite, Ti(IV) should be separated from the dissolved impurities such as Fe(III), Si(IV), and Mn(II) present in ilmenite. In this work, a hydrometallurgical process was investigated to recover pure titanium dioxide from ilmenite by HCl leaching followed by separation and hydrolysis of Ti(IV). An optimum leaching condition was obtained by investigating the effect of HCl concentration, pulp density, and leaching time on the leaching percentage of Ti(IV), Fe(III), Si(IV), and Mn(II). Ammonium hydroxide and sodium hydroxide solutions were employed as neutralizing agents to hydrolyze Ti(IV) from the stripping solution of Ti(IV). Titanium dioxide of the anatase phase was obtained by calcination of the hydrolyzed precipitates with $NH_4OH$ solution. A hydrometallurgical process can be developed to produce pure $TiO_2$ powders from ilmenite.

• Resources Recycling
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• v.24 no.3
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• pp.44-50
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• 2015

Recycling technologies would be required in consideration of increasing demand in lithium ion batteries (LIBs). In this study, the leaching behavior of Ni, Co and Mn is investigated with ammoniacal medium for spent cathode active materials, which are separated from a commercial LIB pack in hybrid electric vehicles. The leaching behavior of each metal is analyzed in the presence of reducing agent and pH buffering agent. The existence of reducing agent is necessary to increase the leaching efficiency of Ni and Co. The leaching of Mn is insignificant even with the existence of reducing agent in contrast to Ni and Co. The most conspicuous difference between acid and ammoniacal leaching would be the selective leaching behavior between Ni/Co and Mn. The ammoniacal leaching can reduce the cost of basic reagent that makes the pH of leachate higher for the precipitation of leached metals in the acid leaching.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.906-913
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• 2015

The red mud generated from the Bayer alumina production process seriously threatens the environment and human safety. Therefore, the reduction and recycling of red mud is an urgent topic in the aluminum industry. In this study, the effects of four parameters, ultrasound power, reaction temperature, time, and acid concentration, on the leaching of Fe, Al from red mud was investigated. The major parameters influencing the metal recovery efficiency from red mud were ultrasound power and reaction temperature. The use of ultrasonic irradiation resulted in 1.72 and 1.28 times higher recovery efficiency for Fe and Al, respectively. The proper conditions for the recovery of the metal components present in the red mud is the ultrasound intensity (150 W), sulfuric acid concentration (4-6N), reaction temperature ($70^{\circ}C$), and reaction time (2 hours), etc.

• Resources Recycling
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• v.3 no.1
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• pp.17-24
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• 1994

Recovery of precious metal values from petrochemical spent catalyst is important from the viewpoint of environmental protection and resource recycling. Two types of spent catalysts were used in this study. One used in the manufacture of ethylene contains 0.3% Pd in the alumina substrate. The other used in oil refining contains 0.3% Pt and 0.3% Re. Both spent catalysts are roasted to remove volatile matters as carbon and sulfur. Then, metallic Pd powder from Pd spent catalyst is obtained in the course of grinding, hydrochloric acid or aqua regia leaching and cementation with iron. For the recovery of Pt and Re from Pt-Re spent catalyst, Pt and Re are leached with either HCI or aqua regia, first. Metallic Pt powder is recovered from the leach solution by cementation with Fe powder. Re in sulfide form is precipitated by the addition of sodium sulfide to the solution obtained after Pt recovery. It is found that 6N HCI can be successfully used as leaching agent for both types of spent catalyst. 6N HCI is considered to be better than aqua regia in consideration of reagent and equipment cost.

• Resources Recycling
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• v.20 no.4
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• pp.46-51
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• 2011

A study on the recovery of tin from the steel ball scraps for barrel plating has been carried out the physical treatment and leaching experiment. The recovery of iron component was over 95% by the physical treatment, and the recovery of tin component was also over 95% by the hydro process.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.159-164
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• 2001

A novel fluidized-bed reactor was designed and installed for bioleaching in a semi-continuous way, by which a process for bioleaching-cyanidation of Guangxi Jinya refractory gold arsenical concentrate was studied. An arsenic extraction rate reaches 82.5% after 4-day batch biooxidation of the concentrate under the optimized condition of pH 2.0, ftrric ion concentration 6.5g/L and pulp concentration 10%. And leaching rate of gold in the following gold cyanidation is over 90%. The parameters of three series fluid-bed reactors exhibit stability during the semi-continuous bioleaching of the concentrate. Arsenic in the concentrate can be got rid of 91% after 6-day leaching. Even after 4 days, 82% of arsenic extraction rate was still obtained. The recovery rates of gold are 92% and 87.5% respectively in cyaniding the above bioleached residues. The results will provide a base for further commercial production of gold development.

• Journal of Powder Materials
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• v.28 no.6
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• pp.497-501
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• 2021

Cobalt (Co) is mainly used to prepare cathode materials for lithium-ion batteries (LIBs) and binder metals for WC-Co hard metals. Developing an effective method for recovering Co from WC-Co waste sludge is of immense significance. In this study, Co is extracted from waste cemented carbide soft scrap via mechanochemical milling. The leaching ratio of Co reaches approximately 93%, and the leached solution, from which impurities except nickel are removed by pH titration, exhibits a purity of approximately 97%. The titrated aqueous Co salts are precipitated using oxalic acid and hydroxide precipitation, and the effects of the precipitating agent (oxalic acid and hydroxide) on the cobalt microstructure are investigated. It is confirmed that the type of Co compound and the crystal growth direction change according to the precipitation method, both of which affect the microstructure of the cobalt powders. This novel mechanochemical process is of significant importance for the recovery of Co from waste WC-Co hard metal. The recycled Co can be applied as a cemented carbide binder or a cathode material for lithium secondary batteries.

• Resources Recycling
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• v.24 no.3
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• pp.3-10
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• 2015

A study has been made on the recovery & separation of cobalt and copper from organic acid leaching solution by solvent extraction. The experimental parameters such as the equilibrium pH, concentration of extractant and phase ratio were observed. Copper was extracted using LIX 84 and Cobalt was extracted using cyanex 272 and versatic acid 10. Experimental results showed that extraction percent of copper was 99% at above eq. pH 2.0 and then more than 90% of cobalt were extracted by cyanex 272 in eq. pH 6.0 and versatic acid 10 in eq. pH 7.5. Stripping of copper and cobalt from the loaded organic phases can be accomplished by sulfuric acid as a stripping reagent and 120 ~ 150 g/L of $H_2SO_4$ was effective for the stripping of copper and cobalt respectively. Finially, the basic optimal process for recovery of copper and cobalt from the bio-leaching solution was proposed.

• Journal of the Korean Applied Science and Technology
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• v.27 no.2
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• pp.208-215
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• 2010

EAF dust which is contained around 30% of zinc, 15% of iron and 3% of lead individually, is chemically treated by ammonium chloride, ammonia water, ammonia gas and carbon dioxide, and also tested and identified the ratios of the recovery of In by applied the variations of particle size, pH and heating temperature as well, in order to getting optimized recovery of the In metal after performing all of those processes. Experimental results showed that the rate of Zn recovery is 97% when the mixture of 1.3 of $NH_4Cl$/EAF is heated to the temperature of $400^{\circ}C$ and leached by water, and 95% recovery of In when ammonia gas and carbon dioxide is added simultaneously and adjust the 9.5 of pH to the same mixture above. For the purpose of remove the impurities in the mixed sample, which is prepared by the two samples, indicated above showing as the ratio of 95% and 97% recovery, in case of applied the cementation process to it, and also by electrolytic process, produced the In plate of 95~97%, and acquired 99-99.5% of In metal ingot finally by applied the heating process at $470{\sim}500^{\circ}C$.

• Resources Recycling
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• v.3 no.2
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• pp.17-23
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• 1994

The dissolution of gold and silver from concentrate was studied with acidic thiourea solution. The results showed that the gold and silver extraction was severely affected by concentration of thiourea and oxidant, pulp density, etc. Especially, oxidant such as ferric ions enhanced the leching rate of gold and silver. High concentration of ferric ions, however, dissolved the sulfide ore to form electrochemically passive layer on the surface of ore particles, which caused the precious metal not to be leached out from the ore. The use of $SO_2$could not effectively enhance the recovery of precious metal but reduce to some extent the consumption of thiourea. The leaching of gold and silver was achieved with recovery more than 90% and 80%, respectively, under the following conditions; Thiourea conc. :0.4M Oxidant : None $H_2SO_4$ conc. : 0.5M Pulp density : <10% Leaching time :4 Hrs Potential :250mV The Thiourea was consumed about 10% in comparison with its initial concentration.