Adsorption behaviour of direct yellow 50 onto cotton fiber: equilibrium, kinetic and thermodynamic profile.

This study investigated the adsorption of direct yellow 50 onto cotton fiber from aqueous solution by using parameters, such as pH, temperature, contact time, initial dye concentration and the effect of sodium sulphate, tetrasodium edate and trisodium citrate. The extent of dye adsorption increased with increasing contact time, temperature and solution concentration. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. It was found that the Langmuir equation fit better than the Freundlich equation. The results show that the presence of SE and SC significantly enhance the dye adsorption onto cotton fiber. In addition, the adsorption data obtained at different temperatures of DY50 onto cotton fiber were applied to pseudo first-order, pseudo second-order and intraparticle diffusion models. The rates of adsorption were found to conform to pseudo second-order kinetics with good correlation. Also, free energy of adsorption (ΔG(#)), enthalpy (ΔH(#)), and entropy (ΔS(#)) changes were determined to predict the nature of adsorption. The positive value of the enthalpy change indicated that the adsorption is endothermic process. The activation energy, Ea, is ranged between 1.9 and 3.9kJmol(-1) indicated that the adsorption process is a physisorption. This low value of Ea generally indicates diffusion controlled process.

Removal of some heavy metal cations by synthetic resin purolite C100.

The discharge of heavy metals into aquatic ecosystems has become a matter of concern over the last few decades. These pollutants are introduced into the aquatic systems significantly as a result of various industrial operations. This paper describes the adsorption behaviour of cation exchange resin purolite C100 with respect to Ce(4+), Fe(3+) and Pb(2+) in order to consider its application to purify metal finishing wastewaters. The batch method has been employed, using metal concentrations in solution ranging from 2.65 to 265mg/L. The adsorption percentages (%) and distribution coefficient (K(d)) were determined for the adsorption system in the aqueous media as a function of sorbate concentration. The experimental isotherm data were analyzed using the Langmuir, Freundlich, and Dubinin-Kaganer-Radushkevich (DKR) equations. It was found that the adsorption phenomena depend on charge density and hydrated ion diameter. According to the equilibrium studies, the metal ions sequence can be given as Ce(4+)>Fe(3+)>Pb(2+). These results show that cation exchange resin purolite C100 holds great potential to remove cationic heavy metal species from polluted wastewater.