Chemical modification of silica gel with 4,4′-((1Z,8Z)-2,5,8-triazanona-1,8-diene-1,9-diyl)diphenol and applications to chromium Cr(VI) ions in industrial wastewaters

This study describes synthesis of a new resin through immobilization of the 4,4'-((1Z,8Z)2,5,8-triazanona-1,8-diene-1,9-diyl)diphenol (TRI) onto silica gel modified with 3-chloropropyltrimethoxy silane and its application for the removal of chromium(VI) ions from aqueous solution as well as from industrial wastewater. The same applications were also made for industrial wastewater vapor. The newly synthesized Si-TRI is characterized by scanning electron microscope and elemental analysis and Cr(VI) heavy metal ions were used as sorbate. The sorption of Cr(VI) ion was evaluated with using batch methods. The value of adsorption of Cr(VI) ion was detected by an atomic absorption spectrometer. The influences of concentration, temperature, amount of metal ions, contact time and pH to sorption on the Si-TRI were also investigated. The optimum pH range for the sorption of the metal ions is 5.0. The mean sorption energies for modified silica gel were found to be 21.32 and 17.68 kJ/mol for Cr(VI) in aqueous solution and industrial wastewater respectively, which may correspond to chemical ion-exchange. The maximum adsorption capacities and isotherm parameters were calculated from the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm equations. The adsorption of Cr(VI) ion onto the immobilized material followed the Langmuir adsorption models. Thermodynamic parameters such as free energy (Delta G degrees), entropy (Delta S degrees) and enthalpy (Delta H degrees) were also calculated from the sorption results. It was reflected reactions were endothermic and spontaneous. The modified structure used as adsorbent was successfully employed in the removal of Cr(VI) ions on the samples of industrial wastewater.