CHARACTERIZATION OF ARSENATE ON NANO-SIZE IRON OXIDE-COATED PERLITE ADSORBENT

This study aims to characterize the arsenate adsorption on nano-size iron oxide-coated perlite, to describe the adsorption rate and efficiency, and to investigate the feasibility of using the low-cost adsorbent material. Perlite is inexpensive and easily available, and could be an efficient adsorbent for removing arsenic from drinking water. The coating of nano-size iron oxide on the perlite surface was performed using a thermal treatment process to utilize the adsorption properties of the nano-size iron oxide and the filtration properties of the perlite.

The adsorption study was conducted using different initial concentrations of As(V) (0.2 to 10 mg/L) in 0.01M NaCl solution and pH of the solutions were adjusted between 6.5 and 7. SEM observations showed clear differences of the surface morphology among perlite, nano-size iron oxide-coated perlite (NIOCP) and As(V)-treated NIOCP. EDAX spectra confirmed that arsenate was adsorbed on the NIOCP surface. BET results illustrated that the pore volume and specific surface areas of perlite were increased from 2.29 to 9.58 mm³/g and 1.73 to 9.62 m²/g, respectively with the coating of iron oxide on the surface but these values were decreased after the As(V) adsorption reaction. Thus the pores and surfaces of the NIOCP were occupied by the As(V). The extent of removal of As(V) was 95 -99.99% within 2-5 minutes of adsorption reaction. This work revealed that the adsorption rate of As(V) ion was very rapid and about 100% of As(V) removal was achieved within less than 5 minutes from the samples containing initial As(V) concentration up to 1.5 mg/L. The adsorption isotherms of both Langmuir and Freundlich for arsenate were nonlinear. The Langmuir equation provided a better fit of the isotherm than that obtained in the Freundlich equation, which indicated that the chemisorption of arsenate species was predominantly taken place on the NIOCP surface. The maximum adsorption capacity of arsenate on NIOCP was estimated to be 0.39 mg/g. The desorption study showed that the adsorbent could be reused after reacting with mild HCl solution. Further study on desorption of NIOCP should be needed for reuse/regenerability. Finally it can be concluded that the NIOCP is a suitable adsorbent for the removal of arsenate from drinking water due to its high adsorption capacity, natural availability and low cost.