Diffusion Dynamics of Metal Ions Uptake at the CarboxylatedEpichlorohydrin Red Onion Skin Extract Resin – Aqueous Interface

Abstract

Investigation into the diffusion dynamics of Mn 2+, Fe 2+ and Pb 2+ ions uptake from aqueous solution by chemically modified red onion skin extract was carried out. The polyhydroxylic extract of red onion skin was utilized in the synthesis of carboxylated-epichlorohydrin red onion skin extract resin (CERR). The fourier transform infrared spectra of red onion skin extract and CERR exhibited variations in bond interactions which was ascribed to the structural modification of the extract to yield CERR. Predictions of the mechanism of diffusion dynamics were carried out by applying the data resolved from the fractional attainment of equilibrium at varied times into the Vermeulen diffusion models within the temperature range of 29 to 70°C. The predominance of film diffusion mechanism was established from the smaller values of its diffusion coefficients as compared to those of particle diffusion. The film diffusion coefficient values were lowest at 29°C, indicating the most probable temperature condition for optimum exchange result with the CERR. Deductions from utilizing the Arrhenius type temperature dependence equation gave negative values of activation energy (-7.223 kJ/mol for Mn 2+ , -6.898 kJ/mol for Fe 2+ and -13.957 kJ/mol for Pb 2+ ions); which suggests that increase in temperature from 29 to 70°C, lowered the rate of the exchange reaction.