Preparing of layered double hydroxide- alginate microspheres for Cr(VI)-contaminated soil remediation

The powdered layered double hydroxide(LDH) synthesized by hydrothermal coprecipitation was compounded with sodium alginate to form microspheres(LDH-AL). The characterizations of the LDH-AL show that the microspheres were successfully prepared. Then the immobilization experiments of hexavalent chromium(Cr(VI)) were investigated. The results have proved the effectiveness of microspheres in the immobilization of Cr(VI) in soil. Other limiting factors including LDH percentage, the effects of pH, LDH-AL dosage, interlayer ions, and initial heavy metal concentration were also explored. The LDH-AL showed advantages and its maximum adsorption capacity is 17.0 mg/g. LDH contained in the materials plays a main role in the removal process. In addition, the toxicity characteristic leaching procedure (TCLP) experiment, plant potting tests, and simulation of natural aging processes were used to verify the stability of microspheres. While a series of characterization investigated the adsorption mechanism, the interlayer ion exchange and surface adsorption are the main reasons for Cr(VI) immobilization in contaminated soil. There are also isomer substitution and complexation adsorption phenomena. This study demonstrated the potential application of LDH-AL microspheres in the immobilization of Cr(VI) from contaminated soil.