A novel remediation method of cadmium (Cd) contaminated soil: Dynamic equilibrium of Cd2+rapid release from soil to water and selective adsorption by PP-g-AA fibers-ball at low concentration

The acid-extractable fraction Cd(II) in soil accumulates easily in organisms, migrates and transforms in the ecological environment, which has posed potential health risks to human. This study found that the acidextractable fraction Cd(II) in soil could be released rapidly into water at very low Cd2+ concentration. Carboxylated polypropylene (PP-g-AA) fibers-ball with high selectivity as adsorbent was used in the Cd(II) contaminated soil-water system. It could remove promptly trace Cd2+ from water even in the presence of interfering metal ions. Moreover, Cd(II) desorbed from soil to water could be continuously adsorbed by PP-g-AA fibers-ball, which kept the Cd2+ concentration always at a low level. This forms a dynamic equilibrium of rapid release- selective adsorption toward the acid-extractable fraction Cd(II) in the soil-water system. Here, the migratory pathway for the acid-extractable fraction Cd(II) to be released from contaminated soil to water and adsorbed simultaneously on the surface of PP-g-AA fibers-ball was established. This work offers a novel protocol that can remove more than 90% of the acid-extractable fraction Cd(II) from contaminated soil within 12 h, thereby contributes better to mitigate the risk of Cd(II) from soil to the food chain without changing the physical and chemical properties of soil.