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 understand 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.