Removal of Cd from solution and in-situ remediation of Cd-contaminated soil by a mercapto-modified cellulose/bentonite intercalated nanocomposite

A novel intercalated nanocomposite of mercapto-modified cellulose/bentonite (LCS-BE-SH) was synthesized by high-speed shearing method in one step at room temperature, and was applied to remove Cd from solution and remediate Cd-contaminated soil. Results revealed that cellulose long-chain molecules have intercalated into bentonite nanolayers and interlayer spacing was increased to 1.411 nm, and grafting –SH groups improved adsorption selectivity, which enabled LCS-BE-SH to have distinct capability of Cd adsorption (qmax = 147.21 mg/g). Kinetic and thermodynamics showed that Cd adsorption onto LCS-BE-SH was well fitted by pseudo-second-order and Langmuir adsorption isotherm. Characterizations of the adsorbents revealed that synergistic effect of complexation (e.g., CdS, CdO) and precipitation (e.g., Cd(OH)2, CdCO3) mechanism played a major role in Cd removal. In soil remediation, application of LCS-BE-SH was most effective (67.31 %) in Cd immobilization compared to the control (8.85 %), which reduced exchangeable Cd from 37.03 % to 11.44 %. Meanwhile, soil pH, soil organic matter, available phosphorus, and enzyme activities (catalase, urease, and dehydrogenase) were improved LCS-BE-SH treatment. The main immobilization mechanism in soil included complexation (e.g., CdS, CdO) and precipitation (e.g., Cd(OH)2, Cd–Fe-hydroxide). Overall, this work applied a promising approach for Cd removal in aqueous and Cd remediation in soil by using an effective eco-friendly LCS-BE-SH nanocomposites.