Contaminant removal by efficient separation of in situ formed layered double hydroxide compounds from mine wastewaters†
The efficient removal of a range of anionic and cationic contaminants from acid mine waters to facilitate water reuse or for safe discharge constitutes a major environmental challenge. Recently, layered double hydroxide (LDH)-type materials have shown considerable efficacy at experimental and full-scale for acid mine water treatment. In this study, LDH-type materials were prepared in situ under different experimental conditions with a method for their separation also developed. This work demonstrated that an interlinked network of smaller LDH aggregates was formed during synthesis leading to the development of stable colloids. Different approaches were tested to separate the solid materials containing the captured contaminants from the solute. Polyelectrolytes adsorbed strongly on the particle networks causing charge neutralization and overcharging, however, destabilization of the stable dispersions was unsuccessful. Diluting the stable dispersions led to rapid sedimentation and separation of the LDH, which facilitated higher solute recoveries.