Studies on arsenic release and its mitigation from tailings dam using nanomagnetite particles

Knowledge of the geochemistry of As in tailings material after beneficiation of gold-bearing sulphidic ores is necessary to comprehend the nature, stability and mobilization of As into the geo-environment and its subsequent mitigation during storage. In this study, XRD combined with reflected light microscopy and SEM-EDX were employed to carry out studies on the mineralogical composition of As in a tailings material. Arsenic-rich solutions were generated from the tailings material using de-ionised water to ascertain As mobilisation. The remediation kinetics of the soluble As was carried out using nanomagnetite (Fe3O4). The XRD and SEM- EDX analyses showed that the major source of As in the tailings material is arsenopyrite (FeAsS). The study further confirmed that the residual As mineral in the tailings material is capable of decomposing during storage and can be subsequently mobilised into the geo-environment. It was established that nanomagnetite can efficiently remove As from tailings leachates; preferably at pH between 6 and 7 and Langmuir isotherm best described the sorption process while the Gibbs free energy of the sorption was found to be -12.1026 KJ/mol. Thus, nanomagnetite can be used to mitigate arsenic foot-prints from tailings dam. (au)