Degradation of benzoic acid by advanced oxidation processes in the presence of Fe or Fe-TiO2 loaded activated carbon derived from walnut shells: A comparative study

Abstract

In this study, the degradation of a major pollutant present in terephthalic acid wastewater, benzoic acid, was investigated by several advanced oxidation methods using catalysts derived from walnut shells. The 10% Fe or 10% Fe-TiO2 (wt/wt, 1:99 as Fe:TiO2) catalysts were loaded on an AC prepared from walnut shells by physical activation or chemical activation methods with different chemical reagents. The effect of the activation method was investigated using catalyst screening tests. The most efficient catalyst for the Fenton-like oxidation and catalytic wet air oxidation was determined as B-FAC and for photocatalytic/photo-Fenton-like oxidation was the N-FTAC from the screening experiments. After the catalyst screening, the effect of operating conditions such as catalyst loading, temperature, initial pH, etc. on the catalytic activity were tested in terms of degradation efficiency by determining their optimum values. Maximum degradation efficiencies from parametric studies for each method were 40% for the Fenton-like oxidation, 70% for the catalytic wet air oxidation, and 90% for photocatalytic oxidation. The highest degradation efficiency was achieved by the photo-Fenton-like oxidation in the presence of the N-FTAC catalyst with a degradation efficiency of 95% at 0.5 g/L catalyst loading, 6 W UV light, 2 mM initial H2O2 concentration, and an initial pH of 3 or 6, with a reaction time of 80 min.