Activated Carbon-Spinels Composites for Waste Water Treatment

Nowadays, mining effluents have several contaminants that produce great damage to the environment, cyanide chief among them. Ferrites synthesized from transition metals have oxidative properties that can be used for cyanide oxidation due to their low solubility. In this study, cobalt and copper ferrites were synthesized via the precipitation method, using cobalt nitrate, copper nitrate, and iron nitrate as precursors in a molar ratio of Co or Cu:Fe = 1:2 and NaOH as the precipitating agent. The synthesized ferrites were impregnated in specific areas on active carbon. These composites were characterized using X-Ray Diffraction (XRD) and Scanning Electron Spectroscopy (SEM). The XRD results revealed a cubic spinel structure of ferrites with a single phase of cobalt ferrite and two phases (copper ferrite and copper oxides) for copper. The CoFe2O4 impregnated on active carbon reached a cyanide oxidation of 98% after 8 h of agitation; the composite could be recycled five times with an 18% decrease in the catalytic activity. In cobalt ferrites, a greater dissolution of iron than cobalt was obtained. In the case of copper ferrite, however, the copper dissolution was higher. These results confirm that ferrites and activated carbon composites are a novel alternative for cyanide treatment in mining effluents.

Gold Electroextraction Fundamentals Using Zinc Three-Dimensional Cathode

In the present work, gold electroextraction technological features on three-dimensional cathode are studied. Zinc powders are used as cathode. Similar ones are used to gold cementation from cyanide solutions. The studies object was production of cyanide solution of following composition, mg/dm3: 7 Au. 123.65 Zn, 670 CN-; pH 10.3. Electroextraction laboratory studies were carried out in cylindrical electrolyzer with a horizontal arrangement of current-carrying electrode. It has been found that zinc powders polarization contributes to more complete gold deposition from cyanide solutions. Moreover, it allows to reduce zinc transition into spent solution, as a consequence, zinc consumption reduces. At the same time, under investigated conditions, significant cyanide oxidation does not occur.