Studies of adsorption thermodynamics and kinetics of Cr(III) and Ni(II) removal by polyacrylamide

Polyacrylamide (PAA), as an adsorbent was investigated for the removal of Ni(II) and Cr(III) metal ions from their synthesized aqueous solutions. The different variables affecting the adsorption capacity of the adsorbent such as contact time, pH of the sorption medium, metal ions concentration and temperature of the solution were investigated on a batch sorption basis. The adsorption equilibrium data fitted best with the Langmuir isotherm model. The maximum adsorption capacities found to be 84.03 and 32.67 mg g-1 of the polyacrylamide for Cr(III) and Ni(II), respectively. Three kinetic models including the pseudo-first-order, pseudo-second-order and intraparticle diffusion equations were selected to follow the adsorption process. Kinetic parameters such as rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was indicated that the adsorption of both ions onto polyacrylamide could be described by the pseudo-second-order kinetic model. Different thermodynamic parameters such as ΔH◦, ΔS◦ and ΔG◦ have also been evaluated and it has been found that the sorption was feasible, spontaneous and exothermic

Removal of Cu(II) from wastewater by waste tire rubber ash

The influence of pH, adsorbent dose, initial Cu(II) concentration and contact time on the removal of Cu(II) from aqueous solution by the batch adsorption technique using waste tire rubber ash as a low-cost adsorbent was investigated. The adsorption equilibrium was achieved after 2 h at pH 4–6, the optimum for the adsorption of Cu(II) ions. A dose of 1.5 g/L of adsorbent was sufficient for the optimum removal of copper ions. The experimental data were analyzed by the Langmuir and Freundlich isotherms and the corresponding sorption constants were evaluated. The adsorption kinetics data were fitted by a first-order equation. The cost of removal is expected to be quite low, as the adsorbent is cheap and easily available in large quantities. The present study showed that waste tire rubber ash was capable of removing copper ions from industrial wastewater samples