The adsorption of As(Ⅲ) on a novel granular Fe-Cu-Mn trimetal oxide (GFCM): Behavior and mechanism

A novel sorbent of granular Fe-Cu-Mn trimetal oxide (GFCM) was fabricated by coating method,with chitosan as adhesive. The GFCM presents an incomplete spheric shape with a diameter of 0.7~ 1.0 mm. It can effectively oxidize As(Ⅲ) to As(V) and efficiently adsorb the new formed As(V). Its maximal sorption capacity on As(Ⅲ) is up to 56.5 mg·g~(-1) at pH 7.0,which is superior to most of reported granular sorbents. The GFCB also shows excellent As(Ⅲ) sorption efficiency over a wide range of pH from 5.0 to 9.0,and is less affected by ionic strength. The coexisting anions would restrain the As(Ⅲ) sorption efficiency by the following order: PO~(3-)_4 > SiO_3~(2-) > CO_3~(2-) > Cl~-> SO_4~(2-). The arsenic-loaded sorbent could be effectively regenerated by using NaOH solution and reused again. During the process of As(Ⅲ) removal,Mn oxide in sorbent is mainly responsible for As(Ⅲ) oxidation,while both Fe and Cu oxides are dominant for adsorbing As(Ⅲ) and formed As(V). Moreover,Cu oxide contributes to enhance As(Ⅲ) sorption performance of the GFCM.