The energy shortage and clean water scarcity are two key challenges for global sustainable development. Near half of the total global water withdrawals is consumed by power generation plants while water desalination consumes lots of electricity. Here, we demonstrate a photovoltaics-membrane distillation (PV-MD) device that can stably produce clean water (>1.64 kg·m −2 ·h −1 ) from seawater while simultaneously having uncompromised electricity generation performance (>11%) under one Sun irradiation. Its high clean water production rate is realized by constructing multi stage membrane distillation (MSMD) device at the backside of the solar cell to recycle the latent heat of water vapor condensation in each distillation stage. This composite device can significantly reduce capital investment costs by sharing the same land and the same mounting system and thus represents a potential possibility to transform an electricity power plant from otherwise a water consumer to a fresh water producer.

A sustainable supply of clean water is essential for the development of modern society, which has become increasingly dependent on desalination technology since 96.5% of the water on Earth is salt water. Thousands of desalination plants are producing massive waste brine as byproduct, and the direct discharge of brine raises serious concerns about its ecological impact. The concept of zero liquid discharge (ZLD) desalination is regarded as the solution, but the current ZLD technologies are hampered by their intensive use of energy and high cost. In this work, a 3D cup shaped solar evaporator was fabricated to achieve ZLD desalination with high energy efficiency via solar distillation. It produces solid salt as the only byproduct and uses sunlight as the only energy source. By rationally separating the light absorbing surface from the salt precipitation surface, the light absorption of the 3D solar evaporator is no longer affected by the salt crust layer as in conventional 2D solar evaporators. Therefore, it can be operated at an extremely high salt concentration of 25 wt % without noticeable water evaporation rate decay in at least 120 h. This new solar evaporator design concept offers a promising technology especially for high salinity brine treatment in desalination plants to achieve greener ZLD desalination as well as for hypersaline industrial wastewater treatment.

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Thin film nanocomposite (TFN) membranes containing 0.05 or 0.10 w/v% functionalized titanate nanotubes (TNTs) in polyamide selective layer were prepared via interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) monomers. Nanomaterials were dispersed into the monomer solution using two different approaches. In the first one, the functionalized TNTs were dispersed into the amine aqueous solution, while in the second approach the same nanomaterials were dispersed in TMC organic solution. The TFN membranes were characterized and compared with a control thin film composite (TFC) membrane to investigate the effect of nanofiller loadings and the fabrication approach on membrane properties. Results showed that introducing nanofillers into the organic phase was more effective to synthesize a TFN membrane of greater separation performance as the use of rubber roller to remove aqueous solution from the substrate surface could cause the loss of a significant amount of nanofillers, which further affected the polyamide layer integrity. It was also found that incorporation of high nanofiller loading tended to interfere with interfacial polymerization and weaken the bonds between monomers blocks, resulting in poor polyamide-nanotubes integrity. Compared to the TFC membrane, the TFN membrane made of 2% PIP and 0.15% TMC with 0.5% nanofiller incorporation could achieve greater water flux (7.5 vs 5.4 L/m 2 .h.bar) and Na2SO4 rejection (96.4% vs 86%) while exhibiting higher resistance against the fouling by protein and dye.