Liwen Ma

“Complexation–precipitation” metal separation method system and its application in secondary resources

Recovery processes of secondary resources usually encounter problems because of the diverse compositions of wastes. To enhance the applicability of traditional hydrometallurgical process toward secondary resources, the adjustment of components is necessary. In traditional hydrometallurgical separation, precipitation and complexation are extensively used. However, their combination as a specific metal separation method has not yet been studied in detail. This approach is very promising for solving problems caused by changeable components during recycling processes of secondary resources. This paper reviews the effects of precipitation and complexation in metal separation processes, and a metal separation method system of “complexation–precipitation” developed to adjust the components of secondary resources is introduced.

The study of carbon-based lead foam as positive current collector of lead acid battery

The carbon-based lead foam was produced by electrodepositing a uniform and dense lead coating on lightweight carbon foam in fluoborate system under appropriate conditions. The cyclic voltammetry showed that its electrochemical properties resembled the metallic pure lead. A lead acid battery equipped with the carbon-based lead foam as positive current collector undergone a charge–discharge test. The battery had a high discharge capacity and a good cycling stability, which indicated that the carbon-based lead foam could serve as positive current collector. The three-dimensional net structure of carbon-based lead foam provides larger surface area than traditional lead alloy grids, thus enhances the specific capacity of lead acid battery. The carbon-based lead foam might be a promising substitute for lead alloy grids.

Electrochemical Dissolution of Tungsten Carbide in NaCl-KCl-Na 2 WO 4 Molten Salt

Tungsten carbide was utilized as anode to extract tungsten in a NaCl-KCl-Na2WO4 molten salt, and the electrochemical dissolution was investigated. Although the molten salt electrochemical method is a short process method of tungsten extraction from tungsten carbide in one step, the dissolution efficiency and current efficiency are quite low. In order to improve the dissolution rate and current efficiency, the sodium tungstate was added as the active substance. The dissolution rate, the anode current efficiency, and the cathode current efficiency were calculated with different contents of sodium tungstate addition. The anodes prior to and following the reaction, as well as the product, were analyzed through X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. The results demonstrated that the sodium tungstate could improve the dissolution rate and the current efficiency, due to the addition of sodium tungstate decreasing the charge transfer resistance in the electrolysis system. Due to the fact that the addition of sodium tungstate could remove the carbon during electrolysis, pure tungsten powders with 100 nm diameter were obtained when the content of sodium tungstate was 1.0 pct.

Acid Leaching Process of Waste Power Lithium Ion Battery

The power lithium ion battery has been widely used for its excellent performance, with the waste batteries increased yearly and causing environmental pollution and resource waste. The problem must be solved immediately. In this paper, through the “alkaline separation-roasting-acid leaching” process, spent lithium ion battery anode is handled so that to achieve the extraction of valuable metals in the anode. The results show positive active material can separate from the aluminum foil by means of the using of NaOH solution. Under the process of 700 ℃ high-temperature roasting for 2 h, active substances Li (NixCo1-x) O2 transform into NiO, CoO, etc., and it is conducive to subsequent acid leaching. After roasting, the acid leaching of active substance is conducted through respectively using hydrochloric acid and sulfuric acid. The leaching rate of Li, Ni, Co are 99.9, 99.5, 99.2% under the optimum conditions in hydrochloric acid system respectively: the concentration of the acid 2 mol/L, the ratio of solid-liquid 60 mg/ml, leaching temperature 90 ℃ and leaching time 50 min. In sulfuric acid system, the leaching rate of Li, Ni, Co are all closer to 100% under the optimum conditions: the concentration of the acid 2 mol/L, the S/L 75 mg/ml, leaching temperature 85 ℃ leaching time 50 min and volume ratio of hydrogen peroxide is 5%. Through the fitting calculation, acid leaching is applied to the nuclear reaction model and leaching of lithium nickel and cobalt are controlled by chemical reaction. Two kinds of acid system all have good results for metal extraction from waste lithium ion battery cathode material. Considering recycling cost and environmental impact, sulfuric acid system is better.