Recovery of Copper from Low Grade Ores by HNO3 Leaching: Process Optimization and Solvent Extraction Studies using Soybean Fatty Acid

This paper presents the recovery of copper from a Nigerian low-grade copper ore containing 4.08 wt. % Cu via nitric acid leaching, followed by solvent extraction using soybeans oil fatty acid extractant. The leaching tests on the milled ore were done according to a 3-factor Central Composite Design with time, acid concentration and temperature as the selected process variables. Regression models were developed from the experimental data for the ore dissolution and the quantity of copper extracted, and the effects of the individual process variables and their interactions were determined from the leaching studies using analysis of variance (ANOVA). Results from the leaching tests indicate that the ore dissolution depends mainly on the leaching time. About 92 percent of the copper contents were recovered at optimum leaching time, temperature and nitric acid concentration of 29.5 min, 81.25 oC and 2.18 M, respectively. The solvent extraction studies show that copper can be extracted from aqueous media using soybeans fatty acid, with the performance of the diluents in terms of the quantity of Cu extracted being MIBK > kerosene > xylene.