Immobilization of Cr(VI) in polluted soil using activated carbon fiber supported FeAl-LDH

Layered double hydroxides (LDHs) have great potential as new amendments for the remediation of Cr(VI) polluted soil. However, the large-scale application of LDHs is limited by the difficulties of separating from the environment and the metal leaching during application. Herein, a carbon-based composite, FeAl-LDH@ACF, was synthesized by assembled FeAl-LDH onto activated carbon fiber (ACF). The resulting FeAl-LDH@ACF had an inherent affinity of FeAl-LDH toward Cr(VI) and the outstanding performance of the ACF, which could easily separate from the soil. Immobilization experiments showed that FeAl-LDH@ACF had good performance for the immobilization of Cr(VI) in polluted soil. Products before and after immobilization were characterized by SEM, EDS, XRD, FTIR and XPS. A Cr (VI) removal mechanism by FeAl-LDH@ACF involving immobilization and reduction processes had been proposed. Cr(VI) was immobilized to the FeAl-LDH@ACF by anion exchange then the Cr(VI) was reduced to the less toxic Cr (III) by Fe2+ on the main laminate of the material. The influencing factors affecting the immobilization performance of FeAl-LDH@ACF for Cr(VI) were explored, for example, the contact time, the dosage, the initial concentration, and the initial pH. In addition, the TCLP extraction tests, dry-wet cycle, freeze-thaw aging cycle, and phytotoxicity tests were considered to investigate the stability and suitability of materials used in the environment remediation.