Comparative study of zero valent mercury immobilization by solid 2026 Chemos

There is a lack of specific treatments to mitigate medium-range mercury concentrations in soil in the context of mercury-based industrial sites decommission. Treatability tests were carried out to assess the immobilization of Hg(0) using in situ solidification-stabilization (S/S). Various chemical treatments were investigated. They were based on solidifying agents and sulfur-based mercury stabilizers, used individually and in combination. These treatments were applied to a limestone backfill model material (BM), at concentrations around 1000 mg kg–1 of Hg(0). Although its ultimate purpose was reagent injection, the treatment was performed through mixing to minimize result variability and enable a robust assessment of the applied chemical treatments. Chemical treatments were assessed considering the Hg-mobility from the treated BM, its mechanical strength, and its residual permeability. The apparently conflicting objectives of mercury sequestration, solidification of a macro-porous material, and maintenance of BM permeability were achieved using very low reagent concentrations ranging from 0.1 to 4% w/w. The study revealed the synergy operating between solidifying and stabilizing agents. After 5 contact days, reductions of up to 600-fold in GEM release and up to 80-fold of total mercury in leachates were achieved.