Current trends for wastewater treatment technologies with typical configurations of photocatalytic membrane reactor hybrid systems: A review

The separation process with the membrane is limited sometimes, therefore, their coupling with other methods such as photocatalysis can exert a synergistic effect, overcome the membrane fouling, and improve energy efficiency, especially suitable for the separation of mixtures. This paper presents an overview of the typical configurations of photocatalytic membrane reactor (PMRs) hybrid systems and their possible applications in industrial wastewater treatment. Various configurations of photocatalytic membrane reactors are described and characterized, including PMRs with photocatalysts immobilized on or in the membrane as well as reactors with suspended catalysts. Several types of photocatalysis-membrane reactor configurations are compared with respect to their permeate flux, membrane fouling, and permeate quality. The numerous variables that influence the performance of PMRs are described, such as the photocatalyst, wavelength, light intensity, temperature, pH, flow velocity, retention time, aeration, inorganic ions, initial pollutant concentration, reactor geometry and design, and membranes. Moreover, this work provides a short introduction to photocatalysis and membrane processes as unit operations. The integrative type of suspension PMR configuration was found to be the optimal configuration for treating industrial wastewater due to its high contaminant removal efficiency and low operation and design costs compared to other configurations.