Development of membrane distillation by dosing SiO2-PNIPAM with thermal cleaning properties via surface energy actuation

Smart dynamic hybrid membranes with self-cleaning capability

The growing freshwater scarcity has caused increased use of membrane desalination of seawater as a relatively sustainable technology that promises to provide long-term solution for the increasingly water-stressed world. However, the currently used membranes for desalination on an industrial scale are inevitably prone to fouling that results in decreased flux and necessity for periodic chemical cleaning, and incur unacceptably high energy cost while also leaving an environmental footprint with unforeseeable long-term consequences. This extant problem requires an immediate shift to smart separation approaches with self-cleaning capability for enhanced efficiency and prolonged operational lifetime. Here, we describe a conceptually innovative approach to the design of smart membranes where a dynamic functionality is added to the surface layer of otherwise static membranes by incorporating stimuli-responsive organic crystals. We demonstrate a gating effect in the resulting smart dynamic membranes, whereby mechanical instability caused by rapid mechanical response of the crystals to heating slightly above room temperature activates the membrane and effectively removes the foulants, thereby increasing the mass transfer and extending its operational lifetime. The approach proposed here sets a platform for the development of a variety of energy-efficient hybrid membranes for water desalination and other separation processes that are devoid of fouling issues and circumvents the necessity of chemical cleaning operations.

Membrane distillation crystallization for water and mineral recovery: The occurrence of fouling and its control during wastewater treatment

Membrane distillation crystallization (MDC) is an emerging technology envisaged to manage challenges affecting the desalination industry. This technology can sustainably treat concentrated solutions of produced water and industrially discharged saline wastewater. Simultaneous recovery of clean water and minerals is achieved through the integration of crystallization to membrane distillation (MD). MDC has received vast research interest because of its potential to treat hypersaline solutions. However, MDC still faces challenges in harnessing its industrial applications. Technically, MDC is affected by fouling/scaling and wetting thereby hindering practical application at the industrial level. This study reviews the occurrence of membrane fouling and wetting experienced with MDC. Additionally, existing developments carried out to address these challenges are critically reviewed. Finally, prospects suggesting the sustainability of this technology are highlighted.