Simultaneous Adsorptions of Pb(II) and Cd(II) in Hard Water by Synthetic Silica Gels Modified with Dithizone

Simultaneous adsorptions of Pb (II) and Cd (II) in hard water by synthetic silica gel which was modified with dithizone were studied. The products treated in the study were silica gel synthesized from the rice husk dust (SG), SG physically modified with dithizone (SGD-Phys), and the SG chemically modified with dithizone (SGD-Chem). Analyses of metals contained in samples were performed by atomic absorption spectrophotometry method. The results showed that the capacity and the sorptions energy of Pb (II) and Cd (II) were increased gradually with the arrangement: SG < SGD-Phys < SGD-Chem. The sorptions capacity gradual 719.42 μmol/g; 724.64 μmol/g and 826.45 μmol/g for Pb (II) metal ions and 847.46 μmol/g, 900.09 μmol/g and 925.93 μmol/g for Cd (II) metal ions, whereas the sorptions energy gradual 24.65 kJ/mol, 24.79 kJ/mol, and 25.33 kJ/mol for Pb (II) metal ions and 20.95 kJ/mol, 21.31 kJ/mol and 21.49 kJ/mol for Cd (II) metal ions. The sorptions process of Pb (II) mostly happened by ion exchange mechanism, while Cd (II) mostly happened by pitfall mechanism.