Kinetic and Thermodynamic Study of Cr (III) Ion Removing from Aqueous Media onto the functionalized Multi-Walled Carbonnanotubes

In this study, the multi-walled carbonnanotubes (MWCNTs) were functionalized and then were characterized by the several techniques such as :Fourier-transform infrared spectroscopy analysis, X-ray powder diffraction ,scanning electron microscopy, Brunauer-Emmett-Teller and Barett-Joyner-Halenda analysis and particle size analyzer. Then, the functionalized multi-walled  carbonnanotubes were used for removing Cr (III) ions from aqueous media. Several adsorption experiments were carried out for evaluating the adsorption capacity of the synthesized FMWCNTs. For adsorbing Cr (III) ions from aqueous solutions. The experimental results showed that the synthesized FMWCNTs have a good capacity for Cr (III) ions adsorption. The effect of the initial concentration of the sorbate, sorbent dosage, temperature, pH  and contact time on the removal  percentage of Cr ( III) ions on to the FMWCNTs and the adsorption capacity of the prepared adsorbent was studied and the optimum value of each of them was determined.Based on the experimental results, the isotherm models evaluation was also performed and the obtained results revealed that the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models can be used for interpretation the experimental results. Kinetic study showed that the kinetic results of this research can be compared with the pseudo first order, Elovich and intraparticle diffusion kinetic models and selecting ones with the largest R2. In addition, adsorption thermodynamic study ,on the basis of the adsorption capacity dependence on the  temperature,was performed. The obtained results showed that the considered adsorption process at the used temperature range is exergonic G0ad<0 and exothermic H0ad<0 and with a decrease in the randomness (S0ad< 0). Based on the magnitude of H0ad, one can claim that the studied adsorption may be a physical adsorption one.