Economic feasibility of copper extraction from Seruwila copper magnetite deposit

Abstract

Sri Lanka is endowed with a variety of industrial minerals such as graphite, quartz, mica, brick and tile clay, ball clay, kaolin, dolomite, calcite, feldspar, miocene limestone, mineral sands (Ilmenite, Rutile , Garnet and Zircon), apatite (phosphate rock), silica sand, magnetite and also gem minerals.- Contribution to the GDP from mining and quarrying industries including gems is within the range of 1.8-2% over the last two decades. However, Government has banned export of minerals used for ceramic, construction and agricultural industries considering the limited availability of such mineral resources in Sri Lanka. Some export limitations were also imposed for other export minerals as well without value addition. However, high energy cost for processing is a drawback to value addition of industrial minerals. Considering the above fact and the country's needs, this research was carried out to evaluate economic viability of manufacturing of copper metal from Seruwila Copper magnetite. A detailed literature survey has been done initially and field investigations were carried out to collect ore samples. The chemical analysis revealed that average copper concentration of the surface sample collected in Arippu area was 1.1%. Copper concentration of finely-ground ore samples could be increased up to 15- 20% using a Potassium Amyl Xanthate in a laboratory scale flotation cell. Concentrated copper sample taken from froth flotation was dissolved in concentrated hydrochloric acid and the filtered solution was used for copper electrowinning. Extraction of copper was directly related to the applied current density. However, current density varies with other factors mainly the distance between electrodes, temperature, pH, concentration of electrolyte, area of the electrode, stirring speed and applied potential etc. Conducting several trial for laboratory made copper sulphate solution by varying a single parameter at a time, the optimum parameters for electrowinning were identified. Unit cost for electrowinning of copper metal was calculated by applying identified optimum current density and other parameter values to actual chalcopyrite solution and average cost of copper extraction was calculated as Rs.l01.7/kg considering the average electrical tariff for industrial application in Sri Lanka is to Rs.l5/kwh.