LAUSR

Abstract Mercapto as an effective functional group for immobilizing heavy metal ions is usually grafted into various materials. However, mercapto is easily oxidized, which limits its practical application to a great extent. Therefore, mercapto iron complex functionalized nanosilica (RNS-SF) was prepared to improve the stability of amendments and the immobilization efficiencies in Pb/Cd-contaminated soil. RNS-SF was characterized with SEM, TEM, FTIR. The long-term stability and immobilization governing factors of RNS-SF were investigated. The results showed that the immobilization efficiencies of Pb and Cd in contaminated soil via RNS-SF were 98.7% and 97.9% with the dosage of 3% (w/w), respectively. Moreover, its immobilization efficiencies remains unchanged from −20 °C to 50 °C. And after 360 days storage at room temperature, the immobilization efficiencies of Pb and Cd were all about 90%. RNS-SF had the best passivation effect on Pb and Cd when the soil moisture maintained at 60% after 6 days aging. Sequential extraction experiments demonstrated that the fractions of EXC species and Carb species of Pb and Cd in the contaminated soil before and after RNS-SF immobilization declined from 22.62% and 43.12% to 0.321% and 0.94%, resulting in substantially reduced environmental risk of Pb and Cd.