EDTA functionalized silica for removal of Cu(II), Zn(II) and Ni(II) from aqueous solution

Ethylenediaminetetraacetic acid (EDTA) functionalized silica adsorbent has been synthesized using (3-aminopropyl) triethoxylsilane (APTES) as a bridging link between silanol groups (SiOH) of silica and carboxylic group of EDTA. Fourier transform infrared spectroscopy (FTIR) and Temperature-programmed oxidation (TPO) analysis confirmed the grafting of EDTA onto the silica. The synthesized EDTA-silica was investigated as an adsorbent for removal of Cu(II), Zn(II) and Ni(II) from aqueous solution. The effect of solution pH, initial solution concentration, and contact time were studied. The removal of metal ions increased with the increase in solution pH, contact time and concentration. The maximum equilibrium time was found to be 45min for all three metal ions. Kinetics studies revealed that the adsorption of Cu(II), Zn(II) and Ni(II) onto EDTA-silica followed the pseudo-second order kinetics and film diffusion and intra-particle diffusion mechanism were involved. Adsorption equilibrium data were well fitted to Langmuir isotherm model and maximum monolayer adsorption capacity for Cu(II), Zn(II) and Ni(II) was 79.36, 74.07 and 67.56mg g(-1), respectively. Thermodynamic results reveal that the removal of metals onto EDTA-silica was endothermic and spontaneous in nature.