Heterogeneous Fenton-like oxidation of pharmaceutical diclofenac by a catalytic iron-oxide ceramic microfiltration membrane
The oxidation of pharmaceutical diclofenac (DCF) was investigated in a catalytic membrane reactor (CMR) comprising a tubular porous alumina (α-Al2O3) membrane, as support material, with embedded iron oxide nanoparticles (nFe) in situ generated in its pores. The performance of the heterogeneous Fenton-type oxidation reaction was examined in a laboratory-scale membrane pilot, with the addition of hydrogen peroxide. Aiming to optimize this CMR, Central Composite Design with Response Surface Methodology was employed to assess the effects of three key process parameters and their interaction on DCF degradation. Encouraging results were obtained, showing a significant DCF oxidation/mineralization by the α-Al2O3/nFe CMR. Feed solution pH was found to be the most significant variable, with acidic values leading to improved performance. Under near optimum operating conditions (pH 3 and 42.9 mg/L H2O2), the removal and mineralization of DCF was ∼65% and ∼48%, respectively. Negligible iron leaching was observed in the tests, which confirms the effective embedding and stability of catalytic nanoparticles in the ceramic porous matrix, thus allowing multiple membrane utilization. Future research directions are proposed towards method optimization, with emphasis given to membrane modification for improving the adsorption of organic pollutants and their oxidation within the catalytic membrane matrix.