Removal of cadmium, copper, nickel, cobalt and mercury from water by Apatite II™: Column experiments

► The efficiency of Apatite II™ increases as the acidity decreases, then the application of apatite-based materials for metal removal treatments should be restricted to slightly acid to neutral waters. ► Because of the preferred process of using phosphate ions to form metal-phosphate precipitates, the mixture with other sources of alkalinity, such as limestone, is proposed to extend the duration of Apatite II™. ► Compared with other reactive materials such as limestone and caustic magnesia that exhibit a reduction of porosity Apatite II™ showed stable hydraulic performance. ► The extrapolation of the column durabilities to a 1-m-thick passive treatment suggests that the Apatite II™ filling can be active between 5 and 10 years for an inflow pH exceeding 5.