Evaluation and microanalytical study of ZVI /zeolite substrate mixtures for treating acid mine drainage using reactive barriers - removal mechanisms

Abstract: Batch and column experiments were performed to evaluate contaminant removal from acid mine drainage (AMD) using volcanic ash zeolite (VA) with or without zero-valent iron (ZVI) media. Two types of AMD were used i.e. WZ with pH of 2.43 taken from goldfields and TDB with pH of 2.93 collected from coalfields. It was found that VA substrate performed similarly or better than ZVI reactive media whose pH reached 7.0 to 8.5. VA was effective in removing heavy metals despite attaining a relatively lower maximum pH of 5.5. Metals Al, Fe, Zn were generally completely removed from both types of AMD by both the VA and ZVI substrates and their 50:50 mixtures. Removal of Mg and Mn was influenced by the type of AMD. Generally, the substrate comprising 50:50 ZVI/VA mixture was found to treat both AMD types fairly consistently, achieving complete removal of major elements in TDB and a majority of other elements in WZ..