Influence of anions on the adsorption kinetics of salicylate onto alpha-alumina in aqueous medium.
The adsorption kinetics of salicylate on alpha-alumina surfaces were studied at 25 degrees C and pH 6 in the presence of 0.05 mM concentration of different anions (Cl(-), Br(-), I(-), SCN(-), HCOO(-), CH(3)COO(-), S(2)O(2-)(3), CO(2-)(3), and SO(2-)(4)) as a function of time. The experimental data were significantly better fitted to a pseudo-second-order kinetics equation of nonlinear form in the entire time duration and are in excellent agreement with corresponding estimated values. Considering adsorption data for salicylate in the presence of Cl(-) as the face value, all the monovalent anions (Br(-), I(-), SCN(-), HCOO(-), CH(3)COO(-)) promote the adsorption of salicylate onto alpha-alumina surfaces while the divalent anions (S(2)O(2-)(3), CO(2-)(3), and SO(2-)(4)) have the reverse effect under similar conditions. DRIFT spectra of alpha-alumina treated with salicylate reveal that the symmetric peak nu(s)(COO(-)) is shifted by approximately 40 cm(-1) to a lower wavelength region, which implies that salicylate forms an inner-sphere complex with alpha-alumina surface in the presence of both mono- and divalent anions.
Borah
Jayanta M
JM
Material Science Division, North-East Institute of Science and Technology, Jorhat-785 006, Assam, India.
Das
Manash R
MR
Mahiuddin
Sekh
S
D000327:Adsorption; D000537:Aluminum Oxide / Q000737:chemistry*; D000838:Anions / Q000737:chemistry; D007700:Kinetics; D012459:Salicylates / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry
D000838:Anions; D012459:Salicylates; D014867:Water; D000537:Aluminum Oxide