Catalytic slurry-membrane reactor for continuous catalytic wet peroxide oxidation of micropollutants as a potential quaternary treatment technology

This work evaluates the feasibility of a catalytic slurry-membrane reactor (CSMR) for the continuous treatment of six emerging pollutants (EPs) included in the Directive (EU) 2024/3019. The system combined CWPO using suspended Fe 3 O 4 particles as the catalyst with a 2 μm polytetrafluoroethylene (PTFE) microfiltration membrane for catalyst retention. The operating conditions were first optimized by a central composite design, using hydrochlorothiazide (HCTZ) removal after 4 h as the response variable. HCTZ was selected based on the preliminary experiments, as it showed the lowest degradation extent and apparent rate constant among the six EPs in the mixture, thus representing the kinetically limiting compound under the studied conditions. The optimum Fe 3 O 4 and initial H 2 O 2 concentrations were 4 g L −1 and 50 mg L −1 , respectively. Under these conditions, the CSMR was continuously operated for 30 d, maintaining removal efficiencies above 80% for all six EPs and an average HCTZ removal of 85%. Dissolved Fe concentrations remained below 0.1 mg L −1 , while no Fe 3 O 4 particles were detected in the permeate. At the nominal operating flux of 12 L m −2 h −1 , the system operated at a low transmembrane pressure of 0.7 kPa without flux decline. SEM, XRD, XPS, and FTIR analyses confirmed that the catalyst maintained its morphological, structural, and surface chemical properties, while the PTFE membrane remained chemically stable after continuous operation. These results demonstrate the potential of the CSMR as an effective configuration for the long-term continuous treatment of water containing mixtures of emerging pollutants, supporting its potential application as a quaternary treatment.