Layered Double Hydroxides Reduce the Availability of Cadmium and Lead in Soil and the Content of Cadmium and Lead in Grain

Abstract

ABSTRACT Layered double hydroxides (LDHs) have excellent immobilization effects on heavy metals (HMs) in water and soil. For the first time in Hunan province, the immobilization effect of Ca-Al LDH (SR-02-02) and Mg-Al LDH (SR-02-03) for the remediation of Cd and Pb was examined in contaminated soils. With treatments of SR-02-02 at 3000 kg/ha(L2–3), the immobilization effect of available Cd and Pb was 54.74% and 20.85%; with treatments of SR-02-03 at 3000 kg/ha(L3–3), the immobilization effect of available Cd and Pb was 68.02% and 26.70%, which showed that Cd, and Pb were gradually solidified into stable oxidizable and residual state. Less HMs were absorbed by rice as a result of the immobilization effect of SR-02-02 and SR-02-03, and the concentration of Cd and Pb in the root, stem, husk, and grain of rice were also significantly reduced. In particular, under the treatment of L2–3, the content of Cd and Pb in grain decreased by 69.13% and 72.67%, respectively; under the treatment of L3–3, the content of Cd and Pb in grain decreased by 80.76% and 100%, respectively. This was because LDHs materials reacted with HMs to form Cd-OH, Pb-OH, CdAl-LDH, and Ca/Mg-O-Pb etc. which reduced the availability of HMs. In conclusion, LDHs material is a promising material for the synergistic remediation of Cd and Pb contaminated soil.