Capillary Action Promoted Enhanced Photothermal Desalination and Separation of Impurities from Water using Honeycomb Structured Porous Magnetic Nanoparticles Derived from Waste Biomass
V.G. Dileep Kumar, Abhinav Chandel, Prachi Upadhyay, Sankar Chakma
Abstract
Utilizing the interfacial solar steam generation process occurring at the interface between liquids and air has emerged as a compelling and economically viable technique. This method shows significant potential in effectively treating water, desalinating seawater, and capturing energy, all while capitalizing on solar power. By leveraging solar energy for enhanced evaporation, this inventive method offers a powerful solution to various issues concerning water. Herein, an easy and effective methodology for interfacial photothermal-based water purification from seawater and wastewater has been reported. A simpler approach has been described for the synthesis of honeycomb-structured porous magnetic nanoparticles (MNPs) from waste cotton using a flame-assisted carbonization technique for high rejection of salts and impurities to achieve usable water. In the study, MNPs were well characterized by using various microscopic and spectroscopic techniques. The photothermal desalination results with MNPs showed a high evaporation rate of ∼3.79 kg/m 2 ·h from saline water, which is quite comparable to that in existing reports. The augmentation in the evaporation rate was due to the enhanced mass transfer by increasing the diffusion rate through a porous medium similar to that of transpiration and the capillary action, which helps water molecules travel upward comparatively at a faster rate. Additionally, the adhesive force is more dominant in saline water, which resulted in decreased contact angle and acceleration of the rate of evaporation. The optical tensiometer analysis confirmed that the contact angles of the MNPs with DI water and 3.5 wt % saline water were 145.31 ± 2° and 118 ± 2°, respectively. Further to support the viability of the reported procedure, a comparative inductively coupled plasma mass spectrometry analysis was performed where the photothermal desalination results showed that the rejection rates were ∼98% Na + ions, ∼95% Mg 2+ ions, ∼75.52% Ca 2+ ions, and ∼80% K + ions with MNPs and light irradiation, due to the combined effects of capillary action and the repulsive forces because of the hydrophobic nature of the MNPs.