A Comparative Study of Cement-Bentonite and Cement-Based Remediation of Lead-Contaminated Soils

Abstract

The mixture of bentonite and cement at a mass ratio of 2:1 (recorded as BC) was used as solidifying agent to repair lead contaminated soil, and traditional cement (PC) was used as contrast solidifying agent. The comparative test results show that the soil restoration and maintenance period reach 7 days and 28 days respectively. Compared with PC solidified soil, the pH and EC value of BC solidified soil is lower, and the pH value and EC value of 4% and 8% BC-solidified soil meet the interval value needed for vegetation growth. The dissolution of heavy metals in BC-solidified soil and PC-solidified soil decreases with the increase of the content of solidifying agent. At the same content, the dissolution of heavy metals in BC-solidified soil is lower, which indicates that the mixed material (bentonite + cement) has better effect on the fixation of heavy metals. The unconfined compressive strength of BC-solidified soil and PC-solidified soil increases with the increase of the content of solidifying agent, but compared with PC-solidified soil, the unconfined compressive strength of BC-solidified soil decreases significantly. Lower unconfined compressive strength is beneficial to the secondary development and utilization of solidified soil. The above research results show that the mixed material of bentonite and cement can effectively fix the heavy metal lead in the soil, avoid the excessive strength of the soil, and consequently cause soil hardening and influence the re-development and utilization. The mixed material is a feasible and economical repair material.