Highly Efficient, Antibacterial, and Salt-Resistant Strategy Based on Carbon Black/Chitosan-Decorated Phase-Change Microcapsules for Solar-Powered Seawater Desalination

Solar-powered interfacial evaporation has been recognized to be a promising and sustainable technology for seawater desalination, in view of the challenge of freshwater scarcity and fossil energy storage. Nevertheless, current cutting edge interfacial evaporation systems mostly ignore the issues of intermittent solar irradiation and bacterial contamination. We have hereby developed a novel type of an interfacial evaporator equipped with carbon black (CB)/chitosan (CS)-decorated phase-change microcapsules as a multifunctional photothermal material for solar-powered seawater desalination, based on a highly efficient, antibacterial, and salt-resistant multipurpose strategy. In the developed microcapsules, an n-docosane phase-change material (PCM) core was engulfed in a TiO2 shell, followed by surface decorating a CB/CS nanocomposite layer. A high thermal energy storage capacity of more than 140 J g-1 was achieved, thanks to tight sealing of n-docosane as a PCM core in the perfect core-shell structured microcapsules. Moreover, a rational combination of CS and CB nanoparticles not only contributes an extremely high solar absorption efficiency of 95.04% and good wettability to the as-synthesized microcapsules, but also imparts outstanding antibacterial and salt-resistant abilities to them. These innovative designs enable the developed evaporator to gain a high evaporation rate of 2.58 kg m-2 h-1, along with an evaporation efficiency higher than 90% for consecutive and stable evaporation of seawater under intermittent solar illumination. Compared to conventional evaporators without a PCM, there is an increase by 1.03 kg m-2 in the total water production of the develop evaporator under natural solar illumination for 8 h on a semicloudy day. The resultant evaporated water presents good vegetation compatibility to meet the requirement of crop growth for agricultural cultivation. This work provides a new pathway for designing and developing the high-performance interfacial evaporators with prominent antibacterial and salt-resistant abilities to produce purified water through solar-powered sustainable seawater desalination.

Automated summary

This article introduces a novel solar-powered seawater desalination system that solves the problems of intermittent solar irradiation and bacterial contamination by using carbon black/chitosan-decorated phase-change microcapsules as a multifunctional photothermal material. The system has high efficiency, antibacterial and salt-resistant abilities, and can continuously and stably evaporate seawater under intermittent solar illumination, increasing the total water production and water purification effect.