Preparation Of Solar Thermal Membrane And Its Application In Water Treatment

Due to various environmental pollution and rapid population growth brought about by rapid social development,water resources have become increasingly scarce.In fact.it is estimated that two-thirds of the world population faces water scarcity.To address the shortage of freshwater resources,many desalination strategies have been developed,such as ultrafiltration,nanofiltration,and reverse osmosis.However,these methods usually require high energy consumption and high equipment costs.Therefore,a simple and efficient method has been proposed to generate steam from a photothermal conversion material floating on the water-air interface,which fully absorbs solar energy and converts it into heat energy.Photothermal conversion materials can reduce the heat loss to the body water by concentrating heat in the upper region,thus improving the photothermal conversion efficiency.However,the low photothermal conversion efficiency of traditional solar evaporation methods greatly hinder the practical application of this technology.Therefore,a facile and efficient method to generate steam using photothermal conversion materials floating on the water-air interface has been proposed,which can fully absorb the solar energy and convert it into thermal energy.In addition,the light-to-heat conversion material can also reduce the heat loss to the bulk water by concentrating the heat in its upper region,thereby greatly improving the light-to-heat conversion efficiency.How to design solar absorbers through reasonable materials,improve the efficiency of light-to-heat conversion,and expand the application in water treatment is the next research.(1)Ag3PO4@CW membrane were obtained by uniformly depositing nanostructured Ag3PO4 on wood blocks after delignification and carbonization by onestep synthesis.The microstructure characterization of the membrane shows that it has a porous structure,which can ensure the reversal of steam,and the capillary force of the wood block can continuously provide water for the absorber.The UV-Vis diffuse reflectance spectrum proves that the Ag3PO4@CW membrane has a higher absorption rate of sunlight.Thermal conductivity tests show that it has excellent thermal diffusivity and good thermal conductivity.High performance liquid chromatography(HPLC)and Inductively Coupled Plasma Spectroscopy(ICP)results show that Ag3PO4@CW membrane has a high removal rate of dyes,heavy metals and various ions in seawater,and the purified water is in line with the World Health Organization(WHO)prescribed drinking water standards.In the seawater desalination cycle experiment,there is no obvious scaling phenomenon on the membrane surface after the cycle.It is further confirmed that it has good stability and durability.Through the determination of the number of E.coli before and after evaporation,it shows that it has good bactericidal performance,and in addition,it has a high removal efficiency for 10%formaldehyde solution.According to the material cost estimate,the cost per square meter is estimated to be $10,which has good economic benefits,making it promising for water purification.(2)In order to further improve the photothermal conversion efficiency and purification performance of sewage,Ag3PO4/TiO2 composite material was obtained by compounding with synthesized TiO2 on the basis of Ag3PO4 material,which was deposited on FFP to obtain the solar absorber Ag3PO4/TiO2@FFP(STP)membrane.The cotton cloth in the absorber can continuously provide water to the surface of the STP membrane.The microstructural characterization of the STP membrane showed that it had fibrous channels that ensured the reversal of steam.To explore the photothermal performance and water purification performance,the surface plasmon effect of defective titanium dioxide and silver phosphate enhances the absorption of solar spectrum,and the solid UV-Vis diffuse reflectance spectrum shows that the STP membrane has a higher absorption rate of solar light.HPLC and ICP results show that the removal rate of organic dyes and heavy metal ions is higher than that of Ag3PO4@CW membrane,and the concentration of various ions in purified water is lower than the drinking water standard stipulated by WHO.Experiments on seawater desalination cycles show that it can be used for efficient and durable seawater desalination.Based on material cost estimates,the cost per square meter is estimated to be less than $10,making it promising for water purification.(3)In order to reduce the cost of solar absorbers,Cu are cheaper than Ag,and Cu2O/C3N4 composites were prepared by a three-step synthesis method as lightabsorbing materials,which were loaded on carbonized melamine with excellent thermal insulation and water transport properties,Cu2O/C3N4@MF(CCF)membrane were obtained to self-assemble solar absorbers for solar evaporation,wastewater purification and seawater desalination.With an estimated cost of $3 per square meter,the CCF membrane greatly reduces the cost and is highly economical.Scanning electron microscopy(SEM)shows that it has abundant porous results,and UV-Vis diffuse reflectance spectroscopy shows that the CCF membrane has a good absorption rate of sunlight.HPLC and ICP results showed that the purification performance of pollutants and desalination performance were efficient,which reached the standards of WHO.