Study of the adsorption-desorption of Cu2+, Cd2+ and Zn2+ in single and binary aqueous solutions using oxygenated carbons prepared by Microwave Technology

In the present work was studied the adsorption-desorption of heavy metals from aqueous solutions using carbonaceous materials prepared with a technology that combines radiant and microwave heating. Three optimum carbons O-Cu, O-Cd and O-Zn were prepared and characterized using elemental analysis, potentiometric titration, nitrogen adsorption isotherms at - 196 °C, SEM/EDX analysis, and temperature programmed desorption (TPD). The three optimum carbons had very high oxygen contents mainly ascribed to surface functional groups of acidic nature. In contrast, the porosity of the carbons was very limited with specific surface areas being < 50 m2/g. Liquid adsorption isotherms were carried out and capacities of the three optimum carbons were 67, 26 and 24 mg/g for Cu2 +, Cd2 + and Zn2 +, respectively. The higher capacity of the O-Cu carbon was explained in terms of the higher electronegativity of metallic Cu and the theory of hard and soft acids and bases (HSAB) defined by Pearson, when compared with both Cd and Zn atoms. Additionally, the desorption percentage of heavy metals was lower than 10%