A hydrometallurgical process was used for selectively extraction of valuable metals from zinc plant residues. The process includes the following two steps. (1) The zinc plant residue is treated by sulfuric acid atmospheric leaching process with KMnO4 as oxidatant to selectively dissolve zinc while leaving most (above 98 pct) of indium and germandium in the iron residues. (2) The iron residues are treated by acidic atmospheric leaching process with NaClO3 as oxidant to dissolve indium and germanium. The valuable metals of indium and germanium in the second leaching solution can be reclaimed by further treatment. The optimum operating parameters of the first stage and the second stage were established by conditional tests. The experimental data indicated that under the conditions employed the zinc extraction in the first stage was above 95%, and the leaching percentage of indium and germanium in the second stage reached 91.6% and 90.7%, respectively.

Hydrothermal sulfidation of pure white lead with elemental sulfur has been studied in the present paper. The variables considered in the study were temperature, time, particle size and elemental sulfur fraction in the reacting mixture. Temperature and time were the most two important factors, with an increase in temperature and holding time the sulfidation extent of lead improved greatly and the constituent of products changed a lot. At temperatures above 140°C, PbS and PbSO4 were the only stable reaction products in the sulfidation of white lead. The experimental data indicated that under the hydrothermal conditions with a particle size of -58+48 μm and sulfur fraction in reacting mixture of 8% at 140 °C for 90 min, and 86% of lead sulfidation extent was achieved.

We prepared nanometer-sized nickel oxide by hydrothermal decomposition. In this work, NiSO4•6H2O and Na2CO3 were used as raw materials to prepare the precursors. Nanometer-sized nickel oxide was obtained after calcining the precursors. The temperature of the calcination process affects the morphology and size of the nanometer-sized nickel oxide. The precursors and products were analyzed by TG, XRD and SEM. Sheet nanometer-sized nickel oxide was obtained and characterized by its high purity, smooth surface, regular hexagon shape, average size of 500 nm and 30-60 nm thickness. The results indicate that the NiO particles become open pore structures at a calcination temperature above 500 °C

A process has been developed at the laboratory scale for leaching of vanadium from a vanadium residue using mixed hydrofluoric and sulfuric acid solutions, and NaClO as an oxidant. The extraction studies were carried out using various acid concentrations, liquid/solid ratios, addition of oxidant, reaction temperatures and leaching times. The optimum leaching conditions were then determined. Characterization of the leach residues was carried out by SEM and EDS analysis. Results indicate that the silicates can be effectively destroyed by HF, and the vanadium contained in the vanadium-iron spinel can be leached by the mixed acid solutions. The addition of NaClO enhanced the leaching process by the oxidation of V3+(s) to V4+ and V5+. The leaching efficiency was also improved by raising the leaching temperature, prolonging the reaction rime and using a higher liquid/solid ratio. A vanadium recovery of 81.8% was obtained by the direct acid leaching process

Leaching behaviors of zinc, copper, indium and iron from a sphalerite concentrate in sulfuric acid-oxygen system has been investigated in the present paper. Various parameters were studied including particle size, concentration of sulfuric acid, partial pressure of oxygen, leaching temperature, and leaching time. The experimental data indicated that under the typical plant conditions employed up to 99% zinc , 85% copper and 90% indium extraction were achieved. The mineralogical analysis of the residue showed that the main minerals are elemental sulphur, unreacted pyrite and quartz, the amount of sulphide sulphur oxidized to sulfur during leaching is 81%. This process provides an effective way for the extraction of zinc, copper and indium from sphalerite concentrate.