Catalytic Wet Peroxide Oxidation of 4-Nitrophenol Over Al–Fe, Al–Cu and Al–Cu–Fe Pillared Clays

Abstract

Bentonite clay was modified with Al, Fe and Cu metal cations to form pillared interlayered catalysts (Al–Fe, Al–Cu and Al–Cu–Fe). These catalysts were synthesized, characterized and tested for their reactivity in the presence of hydrogen peroxide for the degradation of 4-Nitrophenol (NP). The X-ray diffraction studies and Brunauer Emmett Teller results showed increases in basal spacing d (0 0 1) and specific surface area of bentonite clay after pillaring with Al, Fe and Cu metal cations. The effect of various parameters, such as concentration of hydrogen peroxide, catalyst dose, temperature and initial pollutant concentration, for the degradation of 4-NP over Al–Fe pillared interlayered clay PILC catalyst has been studied. Samples were analysed to determine degradation (%) of 4-NP, total organic carbon (TOC) removal (%) and chemical oxygen demand (COD) removal (%). At optimized conditions, Al–Fe PILC showed higher catalytic activity compared to Al–Cu and Al–Cu–Fe PILCs. The degradation efficiency of 4-NP was 99.6% with TOC and COD removal of 83% and 75%, respectively using Al–Fe PILC at 20 mM H2O2, 3 g/L PILC and 50°C temperature in 5 h. Possible degradation pathways have been proposed for the catalytic oxidation of 4-NP.