The Assessment and Remediation of Chromite Ore Processing Residue at Former Disposal Sites, Glasgow, Scotland: Current Status (2007)

摘要

Analytical, experimental and modelling work has identified the mineral phases and processes responsible for the retention and release of hexavalent chromium (Cr(VI)) from high-lime chromite ore processing residue (COPR) under prevailing field conditions in Glasgow, Scotland. Key processes are precipitation/dissolution of Cr-containing minerals, inter-layer anion-exchange, sorption and co-precipitation of Cr(VI), and organic complexation in pore waters. A mineral implicated in Cr(VI) dynamics is a hydrocalumite-type phase, which has anion-exchange properties, exchanging chromate (CrO_4~(2-) for sulfate (SO_4~(2-) in laboratory experiments. Such phases, however, are often transitory to the more stable hydrogarnet, which has now been identified as a major COPR phase capable of hosting Cr(VI). Both the nature of mineral phase retention and the high pH of the COPR militate against direct remediative treatment of the source material, for example by the application of generic methods such as ferrous sulfate to reduce Cr(Vl) to Cr(III). Nevertheless, calcium polysulfide (CaS_x) has recently been successfully applied to the remediation of high-lime COPR and Cr(VI)-contaminated groundwater in a series of laboratory experiments, leading to ongoing field trials.