Calcium hypochlorite removal of mercury and petroleum hydrocarbons from co-contaminated soils

Abstract

Former oil and gas processing sites are often contaminated with both mercury and petroleum hydrocarbons. Traditional methods for treating these co-contaminated soils include thermal treatments and placement in landfills (Stepan et al. 1993). This study examines a chemical oxidation treatment, calcium hypochlorite, and its effectiveness in reducing both the petroleum and mercury content of several industrial soils. A sequential extraction method was used to determine the forms of mercury removed through the hypochlorite treatment. The forms included five organic forms of mercury, mercury associated with the mineral phase, ion exchangeable mercury, water phase mercury, and mercury associated with the petroleum hydrocarbons. The hypochlorite treatment did lower the mercury content of all five soils, but failed to remove the petroleum hydrocarbons from the soils. Prior to the hypochlorite treatment the dominant form of mercury was that associated with soil organic matter while after treatment most of the mercury remaining in the soil was associated with either the petroleum hydrocarbons or the mineral phase.