Evaluation of chemically treated and lime stabilized gold mine tailings: Effect on unconfined compressive strength

For over 200 years of gold mining, little has been done to minimize the negative impact of gold mine tailings to the environment. The overall generation of tailing by South African gold mining industry is approximately 300 million tons of slimes. This study was conducted to develop an effective chemical treatment process to reduce major heavy metals in the gold mine tailings, to stabilize the treated gold tailings with lime, to enhance its unconfined compressive strength. Two reagents were investigated namely, citric acid and oxalic acid, the concentrations were varied between 0.25 M and 0.5 M. The leaching tests were conducted at temperatures of 25, 50 and 85 oC. The Elemental, mineralogical and micrograph analysis were conducted on the raw gold mine tailing, treated tailings and stabilized tailing. The results showed a higher relative proportion of magnesium, aluminium silicon, iron and sulphate. The relative proportion for all other metals was below 1 wt%. Citric acid proved to be the best chemical reagent and the optimum results were obtained when the leaching tests were conducted at a temperature of 85 oC, with the concentration of 0.5 M. The final treated solid products had major constituents which enhances material strength development, thus silica and aluminium. Stabilising the treated tailings with 30% hydrated lime, improved the unconfined compressive strength from 1.14 MPa to 2.9 MPa.