Arsenic(V) removal on the lanthanum-modified ion exchanger with quaternary ammonium groups based on iron oxide
Sebastian Dudek, Dorota Kołodyńska
Abstract
In this study, the commercially available iron oxide sorbent with quaternary ammonium groups was modified with lanthanum(III) ions for removing arsenate(V) from water. Several analyses, such as SEM, N2 adsorption–desorption method, FTIR and XPS, were employed to characterize the ion exchanger and explore the adsorption of As(V) ions on Ferrix A33E-La(III) (in the abbreviated form A33E-La(III)). The experimental results revealed much better sorption properties of A33E-La(III) than those of unmodified A33E. After the modification, the maximum sorption capacity of the ion exchanger increased by 55% and the percentage removal at various initial As(V) concentrations was higher. According to the results, the As(V) removal was spontaneous and of the exothermic chemisorption type which proceeded due to the formation of monodentate and bidentate inner-sphere complexes as well as lanthanum arsenate by precipitation. Even after 3 cycles of adsorption–desorption A33E-La(III) could be used for arsenic(V) removal with almost the same initial efficiency. It was found that the presence of lanthanum on the surface of the ion exchanger plays a great role in the adsorption of As(V) from the contaminated water due to changing the mechanism of the process.