A Study Employing Differents Clays for Fe and Mn Removal in the Treatment of Acid Mine Drainage

Acid mine drainage (AMD) has long been a significant environmental problem that impairs water resources in historic or current mining industries throughout the world. One of the methods using passive treatment system at low cost to remove metals from solution involves the use of clays. The ability of three different adsorbents (montmorillonite K-10, bentonite (NT-25), and hydrotalcite (HT)) to remove Fe and Mn from aqueous solutions and acid mine drainage samples has been studied at different optimized conditions such as pH, amount of adsorbent and contact time. Flame atomic absorption spectrometer (FAAS) was used for measuring Fe and Mn concentrations. Langmuir and Freundlich isotherms were applied and isotherm coefficients were computed. A kinectic study was also developed for HT using the first order, second order and intraparticle diffusion models. A great amount of clay (more than 100 mg) and also contact times higher than 60 min had also no influence in the adsorption capacity for all adsorbents. HT was found to be the best among the studied clays removing more than 90 % of Fe and Mn for all AMD samples investigated. Moreover, the maximum adsorption capacity was 63.7 mg Mn g(-1) HT and 666.7 mg Fe g(-1) HT.