Enhanced removal efficiency of NaY zeolite toward phenol from aqueous solution by modification with nickel (Ni-NaY)

Abstract

The present work was designed to synthesize novel NaY and Ni modified NaY (Ni-NaY) zeolites for efficient removal of phenol from aqueous solution. The Ni-NaY (FAU, Si/Al = 2.56) was prepared by ion-exchange method at 873 K and pH = 5.8. The characterization of NaY and Ni-NaY was done by EDX, FTIR, ATD/TGA, BET, SEM, and XRD. Characterization results revealed that Ni-NaY showed an increased surface area and pore volume compared to NaY. The phenol adsorption reached the equilibrium within 2 h at pH = 4. A comparative study indicated that Ni-NaY exhibited a high adsorption capacity of phenol compared to NaY, with an average removal of 77.20% and 88.79% by NaY and Ni-NaY, respectively. The low coordination number of Ni cations in NaY structure and the ability of this zeolite to stabilize Ni cations in low- valence states were the main reasons for its superior adsorption performance compared with NaY. The experimental adsorption data were applied to different adsorption and kinetic models to under- stand the adsorption mechanism. Results indicated that the Freundlich model and pseudo-second order fited the adsorption of phenol on NaY and Ni-NaY. The phenol adsorption on NaY and Ni- NaY zeolite was mediated principally via hydrogen bonding between the hydroxyl (OH) group of phenol and silanol groups of the Ni-NaY zeolite surface. Results also showed that after 5 cycles of regeneration, Ni-NaY had a removal efficiency higher than 90%, which demonstrated an excellent reproducibility of modified zeolite as an adsorbent.