A study on heterogeneous Fenton regeneration of powdered activated carbon impregnated with iron oxide nanoparticles

This paper reports on the fabrication, characterization and testing of iron oxide nanoparticles – powdered activated carbon (PAC) composites for water treatment and PAC regeneration by Fenton reactions. Different wet impregnation procedures and iron loadings were assessed in terms of organic micropollutant adsorption, by using the pharmaceutical diclofenac (DCF) as model compound. The preparation of a ferrihydrite-impregnated PAC with low iron content (~40.7 mg_Fe/g_PAC) and high BET surface area (1037 m² g^-1) was found to be the optimum, exhibiting excellent DCF adsorption capacity, similar to that of the original PAC (203 mg_DCF/g_PAC/Fe), with the adsorption isotherm satisfactorily fitted by both the Freundlich and Langmuir models. The regeneration of the ferrihydrite-PAC (Fe/PAC) indicated that the presence of iron-oxide nanoparticles is important for achieving a high regeneration efficiency by hydrogen peroxide, even at neutral pH. However, the solution pH had a significant effect on DCF uptake, being greater at acidic pH after the regeneration of the composite. Ongoing R&D is aimed at material optimization and testing in a novel hybrid process scheme developed in author’s laboratory, involving a continuous Fe/PAC – Fenton process in conjunction with a low pressure membrane separation process.