Efficient degradation and mineralization of 4-nitrophenol achieved through innovative saponite-based Al-Ti pillared clay catalyst

Abstract

Pillared clay catalysts are emerging as heterogeneous catalysts for degrading refractory organic pollutants. The present study modified saponite clay using aluminium and saponite metal cations to synthesize Al-Ti pillared clay catalyst (Al-Ti PICC). It is subsequently used to study the degradation and mineralization of 4-nitrophenol. The synthesized Al-Ti saponite clay catalyst is characterized using XRD, BET isotherm, SEM, XRF, and thermo-gravimetric analysis. XRD, BET, XRD, and SEM characterization of Al-Ti PICC results indicate higher surface area (74 m²/g), d-spacing (17 Å), porous and fluffy surface compared to saponite clay. The thermo-gravimetric study reveals a lower decomposition of Al-Ti PICC (5.7%) than saponite clay (38.7%). The parameters affecting the degradation and mineralization of 4-nitrophenol, such as H₂O₂ dosage, catalyst dose, and temperature, were optimized.  At optimized conditions: 20 mM H₂O₂, 3 g/L of synthesized Al-Ti PICC, and 70℃ at 5.7 pH 83.5% mineralization (Total organic carbon removal) with 95.6% degradation of 4-nitrophenol, was achieved after 240 min of reaction time. The TOC removal data was further used to study the reaction kinetics using the lumped kinetic model (LKM). It was observed that the data described well the LKM model for the mineralization of 4-nitrophenol.