CFD-Assisted Process Optimization of an Integrated Photocatalytic Membrane System for Water Treatment

Abstract

An integrated photocatalytic membrane system (IPMS) was developed for potential use in the remediation of naproxen using real water samples from a drinking water treatment plant. Key parameters such as time, pH, water matrix, mixing speeds, flow rate, and light intensity undeniably affected photocatalytic and membrane separation processes. The system optimization was based on improving irradiation to generate a more reactive species and mass transfer to increase the reaction rate. Upon optimization, IPMS achieved 99% naproxen removal efficiency. Computational fluid dynamics (CFD) simulated the flow patterns and radiation distribution inside the photocatalytic membrane reactor to improve irradiation and mass transfer during operation. The simulated flow field revealed the presence of dead zones with different velocities in the photocatalytic membrane reactor; this limited the mass transfer of reactive species in the reactor, resulting in uneven distribution of reactive radicals. The dead zones were mitigated by increasing the mixing speed, and as a result, convective mass flow improved process performance. The governing parameters (flow patterns and radiation distribution) of the simulated and experimental data were in agreement. The absorption of irradiation by the active site of the membranes improved with light intensity; at higher light intensities, the light irradiated deeper into the membrane. As such, the CoFe2O4 nanoparticles incorporated inside the membrane pores became highly activated, thus enhancing degradation. The obtained space–time yield (STY) (1.23 × 1011 mol/cm2.s) and photocatalytic space–time yield (PSTY) (4.39 × 1011 mol/W.s) showed that the developed IPMS was efficient regarding energy intensiveness and throughput for treatment of pollutants in water.