A two-step pH control method to remove divalent metals from near-neutral mining and metallurgical waste drainages by inducing the formation of layered double hydroxide.

A neutral M-rich and M-poor (M = metal) metallurgical waste drainage was used to test a metal removal method based on the precipitation of layered double hydroxide (LDH). The LDH precipitation was induced by adding a salt of Al (trivalent metal missing in the drainage) and maintaining or restoring the pH to a circum-neutral value. The precipitates were characterized by chemical analysis, XRD, ESEM, HRTEM and XAS.