Granular activated carbons impregnated by iron oxide (Fe-GACs) for simultaneous adsorption and photodecomposition of methylene blue in an oxalate solution

The granular activated carbons (GACs) impregnated with iron oxide containing 6-8 mass% Fe (Fe-GACs) were prepared from a commercially available GAC (BAU) and iron oxalate (BAU-OA), iron chloride (BAU-CL) and iron benzohydroxamate (BAU-HA). The impregnated BAU samples heat treated at 250°C had specific surface areas (S_BET) of 111, 50 and 4 m²/g, respectively. The XRD patterns showed amorphous structure in the BAU-CL sample and had low crystallinity (as FeOOH and Fe₂O₃ phases) in the BAU-HA and BAU-OA samples. The BAU-OA and BAU-CL samples showed higher methylene blue (MB) adsorption capacities than the BAU-HA sample, which was corresponded to the S_BET values. The apparent MB photodegaradation rate constant (k_app) was higher in the BAU-OA sample than the other samples under the standard experimental conditions. The intensive photodegradation was found to be at pH = 3 but decreased greatly at pH>5, consistent with the presence of Fe(III)-OA complexes. Since the current process was performed without the addition of hydrogen peroxide and showed higher efficiency under solar light irradiation, this system can be used in the treatment of wastewater containing organic dyes.