Synthetic and Modified Clay for Heavy Metal Removal in Acid Mine Drainage

Abstract

The treatment of acid mine drainage using clays has been widely investigated and has produced the most promising results in unravelling the issue of heavy metals present in AMD that are responsible for endangering the environment and human beings. However, clays in its pure form fails to perform well in AMD with high concentrations of metals. The modification of already available clays and the production of the cheap synthetic form may be an alternative solution into achieving clean water within the government legislated maximum concentrations for human consumption. Nano-clays were used as adsorbents to evaluate their ability to remove heavy metals from acid mine drainage with a specific focus on manganese and iron. The two nano-clay adsorbents used in this study are modified bentonite (MB) and hydrotalcite (HT) clays. Batch adsorption experiments were carried out to determine the adsorption capacity of both clays. The Langmuir isotherm gave the best fit with adsorption capacity of 2.98 and 243.9 mg/g in MB, and 5.44 and 227.27 mg/g in HT, for Mn (II) and Fe (II) ions, respectively. The pseudo-first order and pseudo-second order kinetic models were applied to the data. The best fit was achieved with the pseudo-second order model