Abstract:

In order to investigate the effect of sepiolite addition on the construction workability and permeability of soil-bentonite slurry barrier wall, as well as the retardance of heavy metal cation contamination in groundwater, natural sepiolite was used to modify the soil-bentonite slurry barrier wall. Lead was used as a representative contaminant and slump， permeability and adsorption tests were carried out. The results show that the addition of sepiolite not has much impact on the construction workability of the soil-bentonite-sepiolite barrier material. Increasing the sepiolite dosage from 0 to 30% increases the optimum water content of the barrier material by only 1% when meeting the target slump requirement. Sepiolite has little effect on the permeability performance of the slurry barrier material in the experimental dosage range, and the permeability coefficients of the materials are less than 10-7 cm/s, which can meet the engineering requirements. The adsorption of Pb2+ by the soil-bentonite-sepiolite material is an adsorption process dominated by chemical adsorption, and the adsorption amount of Pb2+ by the material was 89.73, 112.52, 140.85, 183.40 mg/g in the order of 0, 5%, 10%, and 20% of sepiolite doping, and the adsorption amount was reduced when the temperature was decreased. Under the corrosion of Pb2+, the permeability coefficient of the soil-bentonite-sepiolite barrier material gradually increases, but the presence of sepiolite can delay the corrosion of Pb2+ to the barrier material. Changes in pH and lead mass concentration of the exudate indicate that the soil-bentonite-sepiolite barrier material still acts as a blocking material during the experimental time.

Key words: slurry barrier wall, sepiolite, soil-bentonite, heavy metal contaminated groundwater, contaminant erosion