Treatment of gold mining effluent in pilot fixed bed sorption system

• The removal of heavy metals from gold mining effluent was studied in pilot columns.
• 14.8 m3 of effluent was treated prior to As breakthrough in the system.
• The removal efficiency exceeded 98% in all the cases studied.
• Cu, As and Fe uptake amounted to 16.1, 12.7 and 5.5 mg g-1, respectively.
• Cu uptake was 2.3 times higher than the value obtained in a laboratory column study.

This paper studied the removal of heavy metals from gold mining effluent (GME) of the AngloGold Ashanti mine (Obuasi, Ghana) in continuous down-flow fixed bed columns using coconut shell and iron oxide-coated sand as sorbents operated at a temperature of 28 ± 2 °C and a constant flow-rate of 150 mL min− 1. The two-stage treatment system targeted the removal of copper and arsenic, but other heavy metals (iron, lead and zinc) present in the GME in very low concentrations were also removed, with removal efficiencies exceeding 98% for all metals in all the cases studied. A total of 14.8 m3 of GME was treated in 1608 h before arsenic breakthrough occurred in the system. At that point, copper, iron, lead and zinc were still completely removed, leaving no traces of the metals in the treated effluent. Copper uptake amounted to 16.11 mg g− 1, which is 2.23 times higher than the value obtained in a single ion laboratory column study. Arsenic and iron uptake amounted to 12.68 and 5.46 mg g− 1, respectively. The study showed that the two-stage treatment configuration is an ideal system for the simultaneous removal of copper and arsenic from low concentration GME, in addition to other heavy metals present at low concentrations.