Recycling of residues from mining leachate treatment for remediation of arsenic contaminated groundwater

Arsenic is a naturally occurring inorganic contaminant, whose presence in both surface- and ground-water due to natural processes and anthropogenic sources is a widespread problem. In Southern Tuscany (Italy), an important mining district was based until 1996 and scraps from sulfides processing were disposed of in piles on land without any protection for infiltration of leachate, which increased groundwater arsenic content up to 1 mgAstotL-1. Several studies have demonstrated the feasibility of using adsorption on ferric (oxy-)hydroxides (FeOH) to remove arsenic from water. Therefore, the present study evaluates adsorption capacity of residues (mostly FeOH) generated by the treatment of neutral mine drainage (NMD) originated from a local abandoned mine. The first step of the experimental investigation consisted of slow gravity filtration tests of NMD through two non-woven fabrics (NWFs) of different porosities. Afterwards, NWFs overlaid by the precipitated ochre cake (OC) were used as a filtration media to treat a synthetic solution simulating the As-bearing groundwater of the mining district.