Zeitschrift für analytische und bioanalytische Techniken

Abstrakt

Comparative Adsorption Studies of Cd(II) on EDTA and Acid Treated Activated Carbons from Aqueous Solutions

Magda A Akl, Ali M Abou-Elanwar, Magda D Badri and Abdel-fattah M Youssef

This study plans to functionalize activated carbon with oxygen and nitrogen containing groups to improve removal of Cd(II) ions from aqueous solutions. Activated carbon (AC) was treated with nitric acid giving MC-HNO3 that was pursued by modifying with EDTA to form MC-EDTA. AC, MC-HNO3 and MC-EDTA were analyzed using FTIR, SEM, TEM, Boehm titration, point of zero charge and N2 adsorption-desorption analysis. The batch technique sorption studies of Cd(II) onto sorbents were conducted and the factors controlling the adsorption process of Cd(II) were tested. Langmuir and Freundlich models were used to analyze the isotherm data. The equilibrium data fitted well Langmuir isotherm for all adsorbents. Pseudo-first order, pseudo-second order, intraparticle diffusion and the Boyd equations were used to analyze the kinetic data. The rate constants, equilibrium capacities and related correlation coefficients (R2) for each kinetic model were evaluated and discussed. The second order model is the best fit model for the three sorbents. Though intraparticle diffusion has essential role in rate-controlling step in the adsorption process of Cd(II) onto the investigated sorbents, film diffusion is also governing this process. The thermodynamic parameters ΔG°, ΔH° and ΔS° for the sorption processes of Cd(II) onto the adsorbents were estimated, and spontaneity of adsorption was deduced from the negative sign of ΔG°. Desorption study highlighted the cost saving due to the easiness of regeneration for both MC-HNO3 and MC-EDTA.