| The scarcity of freshwater resources has become increasingly severe due to population growth and environmental pollution.By 2025,more than 50%of the world’s population will suffer from a shortage of freshwater,and this number will rise to 75%by 2050.In this context,desalination of seawater and purification of wastewater have become important means of obtaining freshwater resources.However,traditional industries for seawater desalination and wastewater purification are mainly driven by petrochemical energy,which leads to high energy consumption,environmental pollution,complex production processes,and high equipment costs,making it difficult to promote and apply in impoverished and remote areas.As an environmentally friendly renewable energy source,solar energy has been widely used in fields such as photovoltaic power generation,solar thermal conversion,and solar hydrogen production.Therefore,using solar energy as a driving energy source for interface evaporation systems has become a new way to obtain freshwater.Currently,solar-driven interface evaporation systems are mainly used in two application areas,seawater desalination and wastewater treatment.The system can absorb solar energy and convert it into thermal energy to promote water evaporation.The evaporated water vapor is then condensed to form freshwater and collected,while impurities and salt ions in the water are left behind in the water body.However,solar-driven interface evaporation systems still have some issues that need further improvement,such as improving the evaporation efficiency,enhancing the removal of organic pollutants in the water,developing photo-thermal materials with excellent performance,and reducing production costs.Based on these issues,this work constructed a series of photothermal materials by modifying g-C3N4 and ZnIn2S4,and prepared a high-performance interface evaporator,which greatly improved freshwater production efficiency and water quality.The specific research contents are as follows:(1)A photothermal materials of AuNPs@g-C3N4 which doped AuNPs into g-C3N4 was synthesized and loaded onto carbonized melamine foam(CMF)to construct an AuNPs@gC3N4/CMF interface evaporation membrane(AMF).The morphology characteristics of the photothermal material and the three-dimensional network structure of AMF were characterized by scanning electron microscopy and transmission electron microscopy.Excellent water transport capability,good thermal insulation performance,and light absorotion performance enable the AMF to obtain an evaporation rate of 1.675 kg m-2 h-1 under a light intensity of 1 kW m-2,with a corresponding light-thermal efficiency of 94.03%.These outstanding basic properties allow the AMF to achieve an average removal rate of 99.94%for ions in seawater and maintain a high evaporation rate in high-concentration saltwater solutions.The pollution solution before and after treatment was determined by ICP and HPLC,and the results showed that under the light intensity of 1 kW m-2,the AMF membrane show a removal rate of over 99.9%and 99%for heavy metal ions and organic pollutants,respectively.(2)By directly hydrolyzing silane,SiO2 microspheres containing thiol groups were obtained.ZnIn2S4 was further in-situ generated on the surface of SiO2 through a hydrothermal method,and together with sodium alginate aerogel doped with activated carbon,constructed the ZnIn2S4@SiO2/ACSA interface evaporation membrane(ZSAS).Scanning electron microscopy and transmission electron microscopy clearly show the successful loading of ZnIn2S4 and the formation of a core-shell structure.The doping of activated carbon powder enhances the light absorption performance of the interface evaporation membrane while acting as a filler to improve the mechanical stability of the evaporation membrane.The porous structure of the aerogel ensures sufficient water supply inside the interface evaporation membrane.Under a light intensity of 1kW m-2,ZSAS-3 can achieve an evaporation rate of 1.485 kg m-2 h-1 and a photothermal efficiency of 96.33%.In terms of seawater desalination,the interface evaporation membrane has good continuous working ability in simulated seawater and can adapt to higher concentrations of saltwater environments.In wastewater treatment,there is a significant decrease in the concentration of heavy metal ions and organic dyes in the steamed liquid.(3)In addition,to further reduce the preparation cost of the interface evaporation device,we prepared a MIL-100(Fe)@g-C3N4/ACSA interface evaporation membrane(MCAS)loaded with MIL-100(Fe)@g-C3N4 composite material.The pore structure of the black sodium alginate aerogel provides channels for water transport,and its low thermal conductivity maximizes the heat on the surface of the interface evaporator.The surface temperature of MCAS-3 can rise to 44.4℃ within 1 hour,which enables the MCAS-3 interface evaporation membrane to achieve a high evaporation rate(1.562 kg m-2 h-1)and a photothermal conversion efficiency of 93.5%.In terms of seawater desalination,the salt resistance test proved that MCAS-3 has the ability to work continuously in seawater,and the ion content in the steamed liquid is much lower than the minimum standard set by the World Health Organization.For the wastewater treatment,MCAS-3 achieved satisfactory removal effects on heavy metal ions and organic pollutants in water,with removal rates of 99.9%and 99.8%,respectively. |
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