Reactivity of Thioglycolic Acid Physically and Chemically Bound to Silica Gel as New Selective Solid Phase Extractors for Removal of Heavy Metal Ions From Natural Water Samples

A method is presented for the immobilization of thioglycolic acid moiety on the surface of active silica gel via a simple and direct synthetic route and based on one step reaction procedure. Two-product solid phase extractors were successfully synthesized according to physical adsorption and chemical immobilization binding techniques, phases (I) and (II), respectively. The mode of interaction between the silanol group and the thioglycolic moiety was also discussed for both phases based on the infrared analysis studies. The thermal stability properties as well as the effect of buffer solutions on the percentage hydrolysis of the two silica gel phases were examined and revealed the high stability and superiority of silica phase (II) in these respects. The evaluation of the selectivity and metal uptake properties incorporated in these two silica gel phases were also studied and discussed for a series of divalent heavy metal ions under different controlling factors. The mmol/g values were found to be higher in case of phase (I). The selective removal and extraction of some heavy metal ions, viz . Cu(II), Zn(II), and Hg(II) from natural seawater samples was successfully accomplished with the percentage recovery values for the three tested metal ions in the range of 96.5-98.4 - 0.2-0.6%. The presence of higher concentrations of Na(I), K(I), Mg(II) and Ca(II) showed insignificant role or no matrix effect on such selective extraction process due to their 0% values of removal by these silica gel phases (I) and (II).