Sustainable Gold Recovery from Mine Tailings through Reagent Optimisation and Bottle-Roll Cyanidation: Implications for Small-Scale Mining

Abstract

Mine tailings can still contain amounts of gold, due to liberation and recovery inefficiencies during primary processing and secondary mineralisation, thus representing the possibility of secondary resource potential and treatment of tailings as an additional source of gold. This paper presents the optimisation of reagent dosage in reprocessing mine tailings for gold recovery from the Klein Letaba mine, using bottle-roll cyanidation, followed by geochemical, statistical, and spatial characterisation. 39 representative samples were collected at approximately 50-m intervals and analysed following fusion-digestion coupled with ICP-OES determination of concentration, with values ranging from 0.20 to 5.30 g/t. Statistical data from R/RStudio show wide grade variation: a mean of 1.157 g/t, a median of 0.800 g/t, and a standard deviation of 0.500 g/t. dev. of 1.079 g/t. Dev and coefficient of variance of 93.25%, and the data is positively skewed (2.155). Ordinary Kriging demonstrates spatial grade variation and concentrated grade pockets, particularly at S08, S32, S35, and S37, enabling targeted investigations & treatment. During 24-h bottle roll cyanidation in alkaline pH, pH ranged from 9.35-10.14, then stabilised at 9.93, Lime: 4.528kg/t and NaCN: 3.074 kg/t were respectively consumed, mobilisation of gold was at 81.5% and transferred into the solution-carbon system 0.484g/t, resulting in a total recovery of 41.3 %. This study provides information and guidelines for the optimum dosage for tailings reprocessing, while further optimisation with respect to leaching, loading and recovery is required.