Abstract
Clean water supply in off-grid locations remains a stumbling stone for socio-economic development in remote areas where solar energy is abundant. In this regard, several technologies have already introduced various solutions to the off-grid freshwater predicament; however, most of them are either costly or complex to operate. Nonetheless, photothermal membrane distillation (PMD) has emerged as a promising candidate with great potential to be autonomously driven by solar energy. Instead of using energy-intensive bulk feed heating in conventional MD systems, PMD membranes can directly harvest the incident solar light at the membrane interface as an alternative driving energy resource for the desalination process. Because of its excellent photothermal properties and stability in ionic environments, herein, Ti3C2Tx MXene was coated onto commercial polytetrafluoroethylene (PTFE) membranes to allow for a self-heated PMD process. An average water vapor flux of 0.77 kg/m2 h with an excellent temporal response under intermitting lighting and a photothermal efficiency of 65.3% were achieved by the PMD membrane under one-sun irradiation for a feed salinity of 0.36 g/L. Naturally, the efficiency of the process decreased with higher feed concentrations due to the reduction of the evaporation rate and the scattering of incident sunlight toward the membrane photothermal surface, especially at rates above 10 g/L. Notably, with such performance, 1 m2 of the MXene-coated PMD membrane can fulfill the recommended daily potable water intake for a household, that is, ca. 6 L/day.
Highlights
Recent reports show that water consumption has increased 600 times during the last century due to the rapid increase in global population, urban expansion, and industrialization.[1]
Following the vacuum-assisted filtration of our MXene suspensions, we investigated the conformality of the Ti3C2Tx nanosheets over the PTFE membrane using scanning electron microscopy (SEM)
We prepared three sets of MXene-coated membranes, each with a specific aerial density, where the hydrophobic PTFE membranes were successfully coated with the hydrophilic Ti3C2Tx MXene at different aerial densities using an optimized vacuum-assisted filtration technique
Summary
Recent reports show that water consumption has increased 600 times during the last century due to the rapid increase in global population, urban expansion, and industrialization.[1]. MD is driven by the difference in the vapor pressure of fluids across a hydrophobic microporous membrane. It can be categorized into several configurations that mainly differ on the permeate side.[9] Direct contact MD (DCMD) is the most studied among these configurations due to its simplicity and comparatively high flux.[10−12] despite its advantages, the commercialization of MD technology is hindered by a few critical factors, including temperature polarization (TP), which can negatively affect the flux, rendering the process energetically inefficient.[13−17] the magnitude of TP typically increases significantly with the MD module length, limiting the MD scale-up.[18,19]
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