Barrier and Sorption Properties of Polymer-modified Bentonite to Steel Slag Leachate and Its Cr(Ⅲ) Ion

Purposes To prevent containment barriers failure caused by the high hydraulic conductivity of conventional bentonite to chemically aggressive leachates, the polymer-modified bentonite (PMB) was developed. Methods The permeability tests were conducted to investigate the hydraulic conductivity of PMB to high salinity solution, strong alkalinity solution, and steel slag leachate. Moreover, the effects of sorption time, solution pH, and initial Cr(Ⅲ) concentration on Cr(Ⅲ) adsorption were investigated. Findings The results showed that the rigid-wall hydraulic conductivity of the conventional bentonite without polymer to aggressive solutions was as high as 1×10-8 m/s. In contrast, the PMB exhibited a much superior performance in aggressive environment, with the flexible-wall hydraulic conductivity being <10-11 m/s and rigid-wall hydraulic conductivity ≈3×10-11 m/s. Conclusions With the increase of sorption time, solution pH, and initial Cr(Ⅲ) concentration, the Cr(Ⅲ) adsorption increases. The data fit the pseudo-second order kinetic very well. And, the adsorption isotherms are best-fit with the Langmuir isothermal model.