Removal of arsenate from aqueous solution by nanocrystalline Mg/Al layered double hydroxide: sorption characteristics, prospects, and challenges

摘要

Removal of arsenate (As(V)) from aqueous solution using both nanocrystalline and coprecipitatednMg/Al layered double hydroxides (LDHs) was examined under different sorption/desorptionnconditions. The surface area, pore volume, and pore size of the nanocrystalline LDH werensignificantly higher than those of the coprecipitated LDH, thus resulting in a higher As(V) sorptionnmaximum than the coprecipitated LDH. The calculated activation energy (Ea) value was 24.7 kJ/mol,nsuggesting the occurrence of anion exchange process for As(V) removal by the nanocrystallinenLDH. The predominance of anion exchange process was further supported by the investigationnof ionic strength effect, and XRD and FTIR analyses. The effect of aqueous matrix on As(V)nsorption by the nanocrystalline LDH was found to increase in the order of nitrate , silican, sulfate , carbonate , phosphate. Regeneration study showed that a secondary sorptionnmechanism might occur concurrently for the As(V) sorption by nanocrystalline LDH besides thenpredominant anion exchange process. Prospects and challenges for practical application of thennanocrystalline LDH were also discussed in the latter part of this study.