Ti₃C₂-based Solar Still For Efficient Water Evaporation Based On Interfacialsolar Heating

Desalination,remote water transfer,and wastewater recycling are all effective methods on solving the global water shortage.Seawater,accounting for 97%of the world's total water resources,can provide sufficient source for desalination with a broader prospect.The seawater desalination process commonly used in the industry is Multiple-stage Flashing Systemc)and reverse osmosis(RO).However,the two processes are processed with high energy consumption,which leads to high water production costs.If fossil energy is used,it will also cause air pollution and greenhouse effect and the process is not conducive to be applied in remote or island areas.In order to solve the above problems,recently,a solar seawater distillation technology based on air-water interfacial heating has been emerging.In this paper,layered titanium carbide(MXene Ti3C2)was proposed as a photothermal conversion material to explore its application prospects in this technology.The layered structure MXene Ti3C2 with length of 3.0 ?m and width of 1.4 ?m was prepared by the HF etching method using carbon aluminum titanate as the raw material.The BET surface area and the average pore size of the as-prepared Ti3C2 was 1.28 cm2/g and 22.3 nm respectively.Ti3C2 was deposited on a polyvinylidene fluoride(PVDF)filter through vacuum filtration.From the 3D micrograph observation,the surface of Ti3C2/PVDF was flat,and its surface was hydrophobic since its water contact angle was 128.6°.The light absorption rate in the solar spectrum of 200-2000 nm was 96.36%which was measured via ultraviolet-visible-near infrared absorption spectrum combined with Matlab software.The water evaporation process by Ti3C2/PVDF based on interfacial solar heating was fitted with the zero-order kinetics.Under two sunlight intensity,the water evaporation rate by the Ti3C2/PVDF was 0.98 kg·m-2·h-1,which is 2.8 times higher than that of pure water.The water-air interface heating characteristics were verified by a method of real-time recording of reactor temperature changes by an infrared camera.In addition,the effects of Ti3C2 dosage,light intensity and durability on the water evaporation rate were investigated.Finally,the water quality of the condensed fresh water was analyzed using the actual seawater as the water source.To further improve the water evaporation rate and salt-rejecting property of theTi3C2/PVDF,the Ti3C2/PVDF w'as combined with an expanded polyethylene(EPE)foam and air-laid paper(ALP)to form a solar still(denoted as EPE/ALP/Ti3C2/PVDF),in which the Ti3C2/PVDF served as the photothermal material to absorb solar light,the EPE foam served as the theral barrier to avid heat transfer into the underneath bulk watem,and the ALP served as the water transport channel to deliver sufficient water to the H3C2/PVDF.Under the optimal working conditions,the evaporation rate of the EPE/ALP/Ti3C2/PVDF was 1.39 kg-m-2·h-1,which was 4.96,1.42,and 2.05 times higher than the control cases of salt water itself evaporation,water covered withTi3C2/PVDF and water covered with EPE/ALP,respecitively.Besides,the EPE/ALP/Ti3C2/PVDF possessed excellent salt-rejecting property under different salinities and light intensities.