As(III) Adsorption and Oxidation by Metal (Hydro) Oxides Enriched on Alligator Weed Root

Abstract

The dried powder of the alligator weed root (AWR) was employed as a biosorbent to remove As(III) from aqueous solution, using acid pre-treated AWR (HAWR) and As(V) as the contrasts. The results of batch adsorption experiment suggested that there is no substantial difference between As(III) and As(V) adsorption. Both of them are affected by the solution pH significantly, but insensitive to the ionic strength. The speciation analysis indicated that more than 95 % of the total As(III) in aqueous solution is oxidized into As(V) in the presence of AWR, while barely oxidized in the presence of HAWR. It proves that without pre-oxidation, AWR can oxidize and adsorb As(III), simultaneously. The properties of the biosorbent were characterized by various techniques including scanning electronic microscopy-energy dispersive spectrometer, Fourier transform infrared spectra analysis, inductive coupled plasma emission spectrometer and Zeta potential detection. The results suggested that typical metals including Mn, Fe and Al enrich in the morphology of metal (hydro) oxide over the surface of AWR, originally. Based on the nature of the biosorbent and arsenic besides the adsorption and oxidation performances, the metal (hydro) oxides are proved as the essential role to drive the adsorption and oxidation. The proof is that with the metal (hydro) oxides denuded, as the contrast of AWR, HAWR loses its capability of adsorption and oxidation for As(III), totally.