Reactive dye degradation using fe-loaded bentonite as a fenton-like catalyst: From process optimization to effluent acute toxicity

Abstract

© by PSP. The present work demonstrates an application of the heterogeneous Fenton process in the degradation of aqueous solutions of Reactive Blue 4 (RB4) synthetic dye using Fe-loaded bentonite (Fe-Bt) as a catalyst. Characterizations of the Fe-Bt catalyst were performed using XRD, multipoint BET, BJH model, N2 adsorption, FT-IR and SEM/EDS analysis. Effects of the operation conditions (catalyst loading, H2O2 concentration and pH) on decolourization efficiency are discussed with a selection of optimum parameters through response surface analysis. In terms of both decolourization efficiency (98.3%) and stability of the catalyst, optimum conditions for this Fenton process are pH = 3, minimum applied Fe-Bt load of 0.15 g L-1 and initial H2O2 of 3 mM. Samples obtained under optimum conditions described above were analysed to evaluate total organic carbon content within mineralization efficiency, toxicity, as well as ion concentrations (Cl-, NO3 -, NO2 -, SO4 2-). Organic degradation compounds of RB4 dye were detected by GC/MS. Acute toxicity was determined using an inhibitory test on bioluminescent bacterium Vibrio fischeri. According to the results, a Fentonlike process with Fe-Bt could be proposed as an appropriate process for decolourization with the possibility of multiple reuse of the catalyst (reuse of the catalyst was successful after the fifth run) but with an incomplete mineralization of the RB4 resulting in the generation of highly toxic effluent. This drawback of the applied process requires extended reaction time or combination with other methods to remove degradation products.