Alternative Approach of Gold Extraction using Modified Borax

Abstract

The extraction of gold in many part of the world is left in the hands of artisanal local miners who do this with the use of mercury which is considered to be a very hazardous chemical to human and the biophysical environment. This research investigated the use of borax as a replacement for mercury in extraction of gold from its ore. The sample used for the study was collected from Chanchaga mining site in Niger State. Calcination of the sulphide ore was done at a temperature of 600 oC in order to oxidize the sulphur content of the ore. The Borax in its modified form was used as a metal flux in the extraction process and this was optimized through Box-Behnken experimental design method using Design Expert 7.0 software. The effect of temperature, mole ratio of heavy mineral concentrate to borax, and time were studied at 800 – 1000 oC, 0.8 – 3.5 and 15-30 min respectively. Sieve, X-Ray Fluorescence (XRF), and carat analysis of the samples were carried out. The percentage yield of gold extract was 70.2 % at 900 oC, 30 min and 0.8 mole ratio of heavy mineral concentrate to modified borax. The sieve analysis shows that visible gold liberation was achieved between 0.3 and 0.15 mm, the X-Ray Fluorescence showed 88.7 % extract gold purity with 22 carat. This method can be a replacement for the current toxic method of gold extraction using mercury.