Utilization of gold-bearing and iron-rich pyrite cinder via a chlorination–volatilization process

The chlorination-volatilization process has been adopted to make full use of gold-bearing and iron-rich pyrite cinder. However, problems of low recovery rate, pulverization of pellets, and ring formation have been encountered during the industrialization of this process. The effects of various parameters on the volatilization rates of valuable metals and on the compressive strength of roasted pellets were investigated in this paper. The parameters include the CaCl_2 dosage, heating temperature, and holding time. The results show that heating temperature is the most important parameter for the recovery of target metals. More CaCl_2 was needed for the recovery of zinc than for the recovery of gold, silver, and lead. CaCl_2 started to react with sulfides/SO_2/SiO_2 at temperatures below the melting point of CaCl_2 to generate Cl_2/HCl. Gaseous CaCl_2 was formed at higher temperatures and could react with any of the components. The compressive strength of roasted CaCl_2-bearing pellets first decreased slowly with increasing temperature at temperatures lower than 873 K, which could result in the pulverization of pellets during heating. Their compressive strength increased dramatically with increasing temperature at temperatures greater than 1273 K. Certain quantities of CaCl_2 and Fe(Ⅱ) could improve the compressive strength of the roasted pellets; however, the addition of excessive CaCl_2 decreased the compressive strength of pellets.

Silver dissolution in a novel leaching system: Reaction kinetics study

Effective silver recovery is usually restricted by either environmental pollution or high recovery costs. To tackle the issues, this study introduces a novel method for the effective recovery of silver by utilizing the alkaline sodium thiosulfate-potassium ferricyanide leaching system. The reaction kinetics of silver dissolution in this system was investigated via the rotating disk electrode technology. The influences of important parameters, including the rotation speed, sodium thiosulfate concentration, potassium ferricyanide concentration, and temperature, on the silver dissolution rate were systematically investigated. The activation energy was measured to be 17.96 kJ·mol^(-1) when the silver dissolution was controlled by a diffusion process. When the silver dissolution was in the region of mixed control, the reaction orders of ferricyanide and thiosulfate were found to be 0.57 and 0.19, respectively, and the reaction orders of ferricyanide and thiosulfate were 0.55 and 0.22, respectively, when the silver dissolution was controlled by surface reaction. This study has great potential for the development of an environmentally friendly silver recovery process from end-of-life products.

Oxide Inclusions in Ferromanganese and Its Influence on the Quality of Clean Steels

Low and medium carbon ferromanganese produced by oxygen decarburization process and electric silicothermic process was briefly introduced, and the quality of products by these two processes was analyzed. Results showed that the total oxygen content in medium carbon ferromanganese by electric silicothermic process in China, which ranged from 0.039% to 0.171%, was between those of the common and refined products by oxygen decarburization process outside of China. The increments of total oxygen content in liquid steel were estimated when ferromanganese was added for the purpose of Mn element adjustment at the end of smelting. Refined low and medium carbon ferromanganese, which had low total oxygen content, was recommended for composition adjustment of clean steels during final stage of a heat. It is possible that the inclusions in the ferromanganese alloy greatly influenced the quality of clean steel indirectly by affecting the amount, size and composition of inclusions in steel.