Comparison of organic materials for the passive treatment of synthetic neutral mine drainage contaminated by nickel: Short- and medium-term batch experiments

ABSTRACT: This paper addresses the comparison of various low-cost organic materials for the passive treatment of circum-neutral pH contaminated mine water. First, the effectiveness of five organic materials to remove Ni from a contaminated neutral drainage (CND) was compared in short-term batch experiments (24 h) at various pH values. Second, based on results of the short-term experiments, two substrates (brown algae and sawdust) were eliminated and three (horticultural peat, compost, wood ash) were compared along with a new substrate (field-collected surface peat) in medium-term (56 days) batch experiments to treat CND. In these experiments, calcite was added to peat samples and all substrates performed equally well, sequestering over 97% of the Ni. Chemical extractions revealed that Ni was more strongly bound to the horticultural peat-calcite (HD-peat-calcite) residue than to the field-collected peat-calcite (LT-peat-calcite) residue. Compost, because of its higher density, was identified as the most promising candidate for sorption-based fixed-bed column experiments. Nevertheless, wood ash should not be discarded as its alkaline properties favor nickel removal