Adsorption properties of aqueous ferric ion on natural cotton fiber: kinetic and thermodynamic studies

The aqueous ferric (Fe3+) ion has been successfully adsorbed by natural cotton fibers (NCF). The equilibrium of adsorption has been carried out, by taking into account the influence of the ferric ion concentration, doses of NCF, temperature, and the contact time. The percentage of adsorption is slightly increased while increasing the temperature. Langmuir and Freundlich adsorption models are applied in order to describe the thermodynamic parameters and to understand the sorption behavior of ferric ion onto NCF. The Fe3+-NCF adsorption system follows Langmuir and Freundlich isotherm models (R-2>0.993). The capacity (q(max)) and intensity (b) of Langmuir adsorption are calculated to be 49.75mgg(-1) and 0.0193 L mol(-1), respectively. The capacity (K-f) and intensity (1/n) of Freundlich adsorption are 1.114 and 0.840, respectively. The results reveal that the adsorption of ferric ion on NCF is chemisorption, spontaneous and favorable in nature. Adsorption reaction kinetic models, such as pseudo-first-order and pseudo-second-order, and adsorption diffusion model, such as Weber-Morris intra-particle diffusion model, have been used to describe the adsorption rate and mechanism of the ferric ion onto NCF surface. The Fe3+-NCF adsorption system has achieved Lagergren pseudo-second-order model (R-2=1.0 approx.). The kinetic parameters, rate constant, and sorption capacities are calculated. These results suggest that NCF has a high potential use in the removal of ferric ion from aquatic systems.