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Membrane distillation (MD) is a promising thermally-driven desalination process for various applications in food, pharmaceutical, textile, and chemical industries. However, membrane fouling and wetting are still major challenges, which limit the stability of MD membranes over long-term use. From 2005, researchers have developed many strategies to enhance membrane fouling resistance by simultaneously engaging reactions, but these works have not been systematically reviewed and categorized. Therefore, this review aims to identify research gaps and provide an overview of the state-of-the-art reactive MD processes, which are categorized broadly based on two configurations: 1 – " hybrid" involving coupling MD with an oxidation or biological process as a pre-treatment step and 2 – " integrated" involving immobilizing reactive materials on the membrane. The reactive MD processes were sub-classified into five categories based on reaction technology then analysed in terms of working mechanisms, advantages, limitations, and their application potentials. It shows that minimizing fouling in both hybrid and integrated processes can be attributed to the interaction of the organics/degraded by-products with the membrane surface/immobilized reactive layer, and the capability of the pollutants to be oxidized. In addition, depending on the types of the coupled process, oxidation can be accompanied by other mechanisms, such as electrostatic repulsion and electro flotation which is the most promising mechanism. Overall, despite the current developments in hybrid and integrated MD processes, many challenges exist including flux decline in the case of the complex feed solutions, a trade-off between oxidation and other accompanied mechanisms (e., electrostatic repulsion), and the possibility of membrane alteration. Future opportunities can be explored in terms of dedicated fouling studies, energy efficiency, removing/converting waste streams to valuable by-products, durability of the process equipment against oxidation, and targeting unique applications such as the treatment of concentrated organic waste streams. [Display omitted] • Reactive MD categorized into "hybrid" and "integrated" configurations. • Oxidation processes are a major focus in reactive MD. • Challenges include membrane fouling and material degradation. • Reactive MD demonstrates highly efficient treatment simultaneous with desalination. • Future studies should focus on fouling, reaction efficiency and targeted applications. [ABSTRACT FROM AUTHOR]

This study focused on the effect of sodium alginate on the performance of direct contact membrane distillation (DCMD). The feed solution contained various combinations of sodium chloride, sodium sulfate and calcium chloride along with bovine serum albumin, xanthan gum and sodium alginate. Unlike findings from the majority of prior studies that suggested the presence of alginate in feed solution caused the deterioration of membrane process performance, our results indicated that sodium alginate exhibited anti-scaling properties and water flux enhancing effect. However, this interesting phenomenon was exhibited by sodium alginate under particular conditions only. Experiments performed with other organic foulants such as xanthan gum did not display the same trend. It is believed that the presence of a hydrophilic layer (calcium alginate gel), which is much less thermal conductive as compared to the PTFE membrane, on the top of the membrane could reduce the amount of heat dissipated due to evaporative cooling or reduce conductive heat loss in the membrane, thus enhancing the thermal efficiency of the system. • Sodium alginate exhibited anti-scaling properties and water flux enhancing effect • Reduction of conductive heat loss with the presence of hydrophilic layer • The degree of improvement was governed by the consistency of the gel layer formed [ABSTRACT FROM AUTHOR]