PPy nanotubes-enabled in-situ heating nanofibrous composite membrane for solar-driven membrane distillation

Recent developments in solar-powered membrane distillation for sustainable desalination

The freshwater shortage continues to be one of the greatest challenges affecting our planet. Although traditional membrane distillation (MD) can produce clean water regardless of climatic conditions, the process wastes a lot of energy. The technique of solar-powered membrane distillation (SPMD) has received a lot of interest in the past decade, thanks to the development of photothermal materials. SPMD is a promising replacement for the traditional MD based on fossil fuels, as it can prevent the harmful effects of emissions on the environment. Integrating green solar energy with MD can reduce the cost of the water purification process and secure freshwater production in remote areas. At this point, it is important to consider the most current progress of the SPMD system and highlight the challenges and prospects of this technology. Based on this, the background, recent advances, and principles of MD and SPMD, their configurations and mechanisms, fabrication methods, advantages, and current limitations are discussed. Detailed comparisons between SPMD and traditional MD, assessments of various standards for incorporating photothermal materials with desirable properties, discussions of desalination and other applications of SPMD and MD, and energy consumption rates are also covered. The final section addresses the potential of SPMD to outperform traditional desalination technology while improving water production without requiring a significant amount of electrical or high-grade thermal energy.

Designing Photothermal Superhydrophobic PET Fabrics via In Situ Polymerization and 1,4-Conjugation Addition Reaction

This study demonstrates a simple and fast method to integrate superhydrophobicity, UV protection, and photothermal effect onto PET fabrics. The surface of PET fabric forms a hierarchical rough structure through in situ oxidative polymerization of the pyrrole (Py). The 1,4-conjugate addition reaction between pentaerythritol tetraacrylate, 3-aminopropyltriethoxysilane, and octadecyl acrylate not only endows the PET fabric with superhydrophobicity but also forms a cross-linked network structure which improves the stability of multifunctional coatings on the surface of the PET fabric. In addition, the wettability of the prepared PET fabric is investigated by adjusting the Py monomer and octadecyl acrylate concentration. The results reveal that the prepared PET fabrics exhibit obviously superhydrophobic behavior with a contact angle of 155.8°. The surface temperature of the superhydrophobic PPy/PET fabric can rise to 91 °C under a simulated sunlight which is much higher than the pristine PET fabric, while reaching basically the same steady-state in five heating/cooling cycles. The prepared PET fabric also possesses excellent self-cleaning, UV shielding, and solar light absorption performances. Furthermore, the superhydrophobic PET fabric exhibited excellent stability against 180 °C high temperature, strong UV radiation, different pH solutions and organic solvent erosion, 8 h washing tests, and 25 sandpaper abrasion cycles. These findings provide a path for the future development of multifunctional fabrics using fluorine-free environmentally friendly materials.

The advent of thermoplasmonic membrane distillation

Freshwater scarcity is a vital societal challenge related to climate change, population pressure, and agricultural and industrial demands. Therefore, sustainable desalination/purification of salty/contaminated water for human uses is particularly relevant. Membrane distillation is an emerging hybrid thermal-membrane technology with the potential to overcome the drawbacks of conventional desalination by a synergic exploitation of the water-energy nexus. Although membrane distillation is considered a green technology, efficient heat management remains a critical concern affecting the cost of the process and hindering its viability at large scale. A multidisciplinary approach that involves materials chemistry, physical chemistry, chemical engineering, and materials and polymer science is required to solve this problem. The combination of solar energy with membrane distillation is considered a potentially feasible low-cost approach for providing high-quality freshwater with a low carbon footprint. In particular, recent discoveries about efficient light-to-heat conversion in nanomaterials have opened unprecedented perspectives for the implementation of sunlight-based renewable energy in membrane distillation. The integration of nanofillers enabling photothermal effects into membranes has been demonstrated to be able to significantly enhance the energy efficiency without impacting on economic costs. Here, we provide a comprehensive overview on the state of the art, the opportunities, open challenges and pitfalls of the emerging field of solar-driven membrane distillation. We also assess the peculiar physicochemical properties and synthesis scalability of photothermal materials, as well as the strategies for their integration into polymeric nanocomposite membranes enabling efficient light-to-heat conversion and freshwater.