Membrane technology has been used in desalination and wastewater treatment due to its many advantages such as ease of operation, smaller footprint, higher efficiency, and lower chemical consumption over conventional...

The global scenario of water shortage and pollution has necessitated the use of advanced water treatment and desalination technologies. Solar interfacial evaporation has shown promising results for clean water generation but depends on the sunlight intensity, which changes over time and climatic conditions. Furthermore, the solar-driven interfacial evaporation cannot operate in the dark and is susceptible to salt deposition. Here, we have explored the Joule heating effect in laser-induced graphene (LIG)-based Joule heaters (JHs) for interfacial water evaporation under different applied voltages. The effect of stacking of Joule heaters has been explored and found to give an enhanced evaporation rate with less spatial footprint and energy consumption. The evaporation rate in a single-layer LIG JH reached ∼5 kg·m–2·h–1 under the application of 10 V. The JH area and its stacking effect on evaporation rate, spatial footprint, and energy consumption were investigated. An increase in evaporation rate by seven times and reduction of electrical energy consumption by three times has been demonstrated by three levels of stacking compared to its equivalent triple-area LIG JH. The enhanced performance of the stacking configuration could be due to the enhanced heat transfer from the bottom JH to the upper JH, thermal concentration, and reduced thermal losses to the environment. The single-layer LIG JH also gave ∼2 kg·m–2·h–1 evaporation rate under natural sunlight and environmental conditions, showing potential for solar interfacial evaporation. The JHs also showed excellent resistance to salt deposition with self-salt-cleaning capability under the tested conditions. These compact stacked JH systems could be integrated with renewable energy, which can be operated in the presence and absence of sunlight. Such compact JH systems with a lesser spatial footprint, enhanced evaporation rate, and reduced energy requirement can help in providing constant water evaporation for various applications.

No abstract

Laser-induced graphene (LIG) is a low-cost, chemical-free single-step fabrication process and has shown its potential in water treatment, electronics, and sensing. LIG fabrication optimization is mostly explored for dense polyimide (PI) polymers. However, LIG-based filters and membranes for water treatment need to be porous, and additional steps are required to get porous surfaces from PI-based surfaces. Polyethersulfone (PES) porous membranes are cost-effective and are common in water purification as compared to PI; further, the optimization of LIG fabrication on PES-based porous membranes is not explored. So, this study demonstrated the fabrication, optimization, and characterization of LIG with different laser parameters such as power, speed, image density (ID), focusing, laser platforms, and membrane support layer effect on porous PES commercial (UP010) and lab-casted 15% PES (PES15) membranes. The performance of optimized LIG filters was tested for interfacial evaporation (IE)-based desalination in single and stacked layer configuration and water purification applications such as dye removal and disinfection. IE was done in Joule heating (JH) and solar heating (SH) modes, and the UP010-ID7 LIG filter showed the highest JH evaporation rates of ∼1.1, 1.8, and 2.82 kg m −2 h −1 in single, double, and triple stacked configurations, respectively. Using a JH IE setup, the best-performing UP010-ID7 LIG filters have also shown ∼100% removal of methylene blue dye from the contaminated water. Furthermore, all LIG filters showed a complete 6-log bacterial inhibition at the 5 V filtration experiments; at 2.5 V, the optimized LIG filters showed a higher removal than the non-optimized filters. Additionally, the LIGs obtained with the aluminum platform were the best quality. This work demonstrates that laser power, ID, platform, and membrane support are critical parameters for the best-performing PES-LIG filters, and they can be effectively utilized to fabricate PES-based LIG porous surfaces for various energy, environmental, and catalysis applications.