SILICA GEL-PHYSICALLY ADSORBED-DIPHENYLCARBAZONE AS A SELECTIVE SOLID PHASE EXTRACTOR AND PRE-CONCENTRATOR FOR CHROMIUM (III) AND IRON(III)

Phenylazoformic acid 2-phenylhydrazide (diphenylcarbazone) is a nitrogen and oxygen donor atoms containing chelating compound. This was used to modify the surface of silica gel via physical adsorption technique to produce a new chelating silica gel phase (Si-DPCZ) with a certain incorporated characters for interaction with metal ions. Surface modification was identified and characterized based on the infrared and elemental analysis as well as thermal desorption method. The determined surface coverage values were found 0.310 and 0.325 mmol g^-1 according to elemental analysis and thermal desorption method, respectively. Factors affecting the metal sorption properties of (Si-DPCZ) for a series of metal ions were studied and evaluated including the pH of metal ion solutions and the effect of shaking time on the metal capacity values. The results refer to the good metal sorption of (Si-DPCZ) for Cr(III), 0.350 mmol g^-1, iron(III), 0.330 mmol g^-1 and Cu(II), 0.280 mmol g^-1 with the same order. The stoichiometric ratios for these metals-(Si-DPCZ) complexes were identified as 1:1 while for other metal ions as Zn(II) and Cd (II) the stoichiometric ratios were found to take place by 1:2. The selectivity characters incorporated into (Si- DPCZ) were also studied by determination the distribution coefficient and separations factor values for the same series of metal ions and found to provide additional evidences for the strong affinity of (Si- DPCZ) toward Cr(III) and Fe(III). The potential applications of (Si-DPCZ) for selective extraction and preconcentration of heavy metal ions Cr(III), Fe(III) and Cd(II) in the range of ppm and ppb were successfully performed with percentage recovery values of 95.0 for the tested metal ions.