Enhancement of Arsenite Sorption onto Oxide Coated Light Expanding Clay Aggregate by Means of Manganese Oxide

Arsenic(As) is highly toxic to humans wherefore its removal from groundwater is a great challenge on areas with As- containing minerals in soil. One of the most common technologies applied in purification of the unsafe waters is sorption. However, As species differ in their sorption behaviour. In anoxic conditions prevailing in groundwater, Asis present as arsenite (AsIII) which has a decisively lower sorption tendency than arsenate (AsV) that can be efficiently retained on the surface of aluminum (Al) and iron (Fe) oxides in the soil. Furthermore, in anoxic conditions also Fe is present in ferrous form (Fe2+) not able to retain any anions. This study was undertaken to examine if the sorption of AsIIIfrom water can be enhanced by using manganese oxide (MnO2) as an oxidizing agent transforming AsIIIto AsV. Batch experiments were carried out by using Light Expanding Clay Aggregate (LECA) and LECA coated with Al oxide (AOCL) or Fe oxide (IOCL) as sorbent materials. The results revealed that MnO2 resulted in a 4-fold, 3.7-fold and 3.2-fold increase in the As sorption onto LECA, IOCL and AOCL, respectively.