Synthesis of an organic chelate doped sol gel filter to remove Cu (II) ions from aqueous solutions

A leaching free sol-gel glass resin was synthesized by doping 1-5-methyl-4-(2-thiazolylazo)resorcinol (5-Me-TAR) ligand in an inert, optically transparent and porous sol-gel glass, the produced gel matrix was used in the solid phase extraction to remove Cu(II) fromwater samples. The doped ligand is dissolved in the liquid phase at the beginning of the preparation; by hydrolysis and condensation of the alkoxysilanes, a solid glass forms around the dopant. The ligand molecule is entrapped inside the glass pores while small Cu(II) metal ions can diffuse into the pores where they are complexed by the ligand and retained inside the pores. Absorption and fluorescence spectroscopy were used to characterize 5-Me-TAR ligand and 5-Me-TAR-Cu complex both in solution and sol-gel glass. The sol-gel glass precursors were carefully selected to produce a glass composite material doped with the ligand with no leaching especially when the glass is soaked in solution. To study complexation/adsorption, the  batch method was employed in which a known weight of the sorbent resin (glass containing the ligand) is mixed with a known concentration of Cu(II) ions. In order to attain the maximum metal ion complexation/adsorption capacity, these organically modified silica filters were optimized to the optimum separation/preconcentration conditions of analytes, including the kinetics, isotherm, effect of pH and shaking time; afterwards, the solution was filtered. The amount of copper metal ion complexed/adsorbed was determined by the difference between the initial concentration in aqueous solution and that found in the supernatant using a flame AA. With a loading of 0.013 g ligand per g of dry silica (0.055 mmol ligand per g), the sol-gel silica sorbent has a capacity of 0.053 mmol Cu/g. In all cases, applications to reference materials and to real environmental samples were investigated.

Jordan Journal Of Chemistry, 2014, 9(2), 81-96.