Preparation of cellulose nanocrystals-agarose-titanium carbide hydrogel interfacial evaporator for desalination and pulping waste liquid treatment

The shortage of fresh water resources and energy crisis have seriously affected the sustainable development of human society. Therefore, exploring sustainable water desalination technology for human and industrial use has become a research hotspot. In recent years, utilization of solar energy to achieve water desalination has become an effective way to produce clean fresh water at a low cost. Biopolymer-based hydrogels are candidates for efficient solar evaporation due to their internal porosity, structural diversity, biocompatibility and other properties. In this study, cellulose nanocrystal (CNC) was used as raw material and agarose (Agar) as hydrogel self-crosslinking network to prepare cellulose nanocrystals-agarose- titanium carbide (Ce-CAM) composite hydrogel interfacial evaporator. Scanning electron microscopy, Fourier transform infrared spectroscopy, and rheometer were used to analyze and characterize the physicochemical properties of Ce-CAM composite hydrogels, and to explore their applications in seawater desalination and desalination, and pulping waste liquid purification and treatment. The results showed that the light absorption of Ce-CAM composite hydrogel in the range of 250-2500 nm was more than 90%, and the light absorption of Ce-CAM composite hydrogel in the range of 1 kW·m⁻². Under the light intensity of 1 kW·m⁻², its evaporation rate of 3.5% NaCl solution and pulping waste liquid was 1.44 kg·m⁻²·h⁻¹ and 1.42 kg·m⁻²·h⁻¹, respectively, and the removal rate of four ions, namely, Na⁺, Mg²⁺, K⁺ and Ca²⁺, was greater than 99.9%. Its BOD and COD removal could reach 99.48% and 99.53%, respectively. This study can provide a potential technical solution for the use of hydrogel-based interfacial evaporation for seawater desalination and pulping waste liquid purification and treatment.