The gallium electrodeposition from alkaline solution has a very low current efficiency, the reason for which is still not quite understood. The effects of electrode materials used for gallium electrodeposition, as well as the effects of NaOH concentration and the anions concentrations in the solution, including 5042-, SiO32-, CO32-, AlO2-, F-, and CI-, on the deposition were analyzed in this study. The suitable materials of SUS316-SUS316 were suggested for the gallium electrodeposition. Based on the electrode couples, the NaOH concentration of 4 mol.L-1 for gallium electrodeposition exhibits the greatest current efficiency. Moreover, the current efficiency would decrease in the electrolyte along with the increasing concentration of the anions, except that, 0.2 mol-L-1 C1- in the solution slightly improves the current efficiency of gallium elec- trodeposition. Moreover, the gallium deposited on the cathode from the solution with 0.6 mol.L-1 SiO32- appears tiny black in color and coarse. Meanwhile, SUS304 is shown to be not suitable to be used as cathode for the gallium electrodeposition from the alkaline solution.
The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater dis charged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from plateletlike and nee dlelike shape to rodlike shape when the temperature was increased from 25 to 70 ℃. An increase in the agglom.
