Preparation Of Hydrogel Porous Materials And Its Application In Solar Evaporation

In recent years,the shortage of water resources has become increasingly serious,and the technical means of purifying seawater or wastewater to obtain freshwater resources have received extensive attention.The interfacial evaporation technology utilizes solar energy to realize the separation of water and impurities through water evaporation,which was a promising strategy for clean water production.However,the traditional interfacial evaporation technique suffers severe heat loss due to the conduction of heat by water.Therefore,it was of great significance to construct a high-performance evaporator to make full use of heat.In this paper,the purpose of regulating the distribution of water content,reducing heat conduction and improving heat utilization efficiency was achieved by constructing thermos-sensitive hydrogels.The details were as follows:（1）A temperature-sensitive hydrogel was prepared by composite cross-linking of N,N-diethylacrylamide and acrylamide,which was used as a solar evaporator substrate to explore the effect of temperature sensitivity on the evaporation rate.The results were analyzed according to the water contact angle,evaporation surface area,and swelling properties.Due to the absorption of light on the upper surface of the evaporator,the surface temperature increases and the hydrophobicity increases.Then the water content of the evaporation surface is reduced,and the heat was used intensively.The lower surface of the evaporator was immersed in water,so the surface temperature was lower and still maintains good hydrophilicity.Therefore,an adequate water supply can be provided.Evaporation performance results show that under 1 sun light conditions,the absorbance and evaporation rate of the thermos-sensitive solar evaporator can reach 95%and 2.74 kg m^-2 h^-1,respectively.In addition,the evaporator has good reusability after several cycles.（2）For the environmentally friendly preparation of temperature-sensitive solar evaporators and uniform dispersion of photothermal materials.Through the strategy of in-situ crystallization of CuS on sulfonated lignin（SL）,SL-CuS composite photothermal materials with excellent photothermal conversion performance and good dispersion properties were prepared SL-CuS hydrogels were further prepared by incorporating them into thermos-sensitive hydrogels.The results of FTIR,SEM,XRD,XPS and TEM indicated that CuS was successfully in-situ crystallized on the SL framework.Because the SL-CuS composite photothermal material has abundant hydrophilic groups,it can be uniformly dispersed in the SL-CuS hydrogel without blocking the pore structure of the hydrogel.This ensures an adequate water supply.The existence of CuS in the SL-CuS composite photothermal material in turn enables the SL-CuS hydrogel to absorb light energy and convert it into heat.Evaporation performance results show that under 1sun light conditions,the absorbance and evaporation rate of SL-CuS hydrogel can reach 94%and 2.67 kg m^-2 h^-1,respectively.（3）In order to further improve the salt resistance of the temperature-sensitive solar evaporator and realize its self-floating.PY-DGS1 foam gel was prepared by mixing sodium alginate with N,N-diethylacrylamide and foaming by mechanical stirring.According to the characterization results of water contact angle and scanning electron microscopy,PY-DGS1foam gel has a large number of open and closed cells with large pore size inside.The open-cell bubbles were connected to form a channel network,which was conducive to the rapid dissolution of salt crystals.The presence of closed-cell air bubbles ensures that the foamed gel achieves self-floating.The evaporation performance results show that the PY-GDS1 foam gel can be continuously evaporated in 10%high-concentration brine for 10 h without salt crystallization,and can maintain a solar evaporation rate of 2.11 kg m^-2 h^-1.