Preparation And Properties Of Low-grade Attapulgite-based Porous Photothermal Materials

Solar interface evaporation seawater desalination technology has been considered as one of the most promising technologies to replace traditional seawater desalination technology for many years because of its high thermal localization efficiency and good sustainability.However,the existing photothermal materials still have many problems in practical application,such as low evaporation efficiency,high raw material cost and complex preparation process,which limit the large-scale development and application of solar interface evaporation technology.In order to solve the problem of low evaporation efficiency,researchers mainly improve evaporation efficiency by increasing light absorption of materials,enhancing heat management and improving water transport.For the problems of high cost of raw materials and complex preparation process,the development of photothermal materials with low cost,simple preparation and excellent properties are the key to solve these problems.In this paper,clay-based photothermal materials were prepared from cheap attapulgite(ATP)in Linze,Gansu Province,using polyethylene glycol(PEG),chitosan(CS)and carboxymethyl cellulose(CMC)as carriers.And the solar-water vapor evaporation efficiency and seawater desalination ability were tested under laboratory conditions.The main research contents are as follows:1.The raw ATP from Linze,Gansu Province was dispersed by sodium hexametaphosphate,mechanically mixed with PEG and self-made manganese dioxide nanowires(MnO₂NWs),the clay-based composite(APM)was prepared by freeze-drying,and then carbonized at high temperature to prepare photothermal material(CAPM).The composite photothermal material(CAPE)without MnO₂NWs was prepared by the same method.Analyzed by SEM,TEM and BET,both of them have intertwined three-dimensional network structure with rich pores,low thermal conductivity,super hydrophilicity and high absorptivity of more than 95%to the solar spectrum.The evaporation efficiency of the CAPM and CAPE under 1 k Wm^-2 light intensity is about 85.94%and 75.0%,respectively.At the same time,the distillate of simulated seawater in CAPM was detected,and its ion contentd were far lower than the standard of drinking water,and has a good ability of seawater desalination.2.Using ATP as the raw material,CS as carrier,glutaraldehyde as cross-linking agent,clay-based aerogel(ACS)was prepared by simple mechanical mixing and freeze-drying.The light absorptioner(FACS)was obtained by carbonization treatment on its surface as photothermal transfer layer(C-FACS).Analyzed by SEM and BET,FACS has a porous network structure with different pore sizes,showing light weight(0.0326 gcm^-3),self-floating,super hydrophilic and low thermal conductivity(0.0218 Wm^-1K^-1),strong light absorption ability and can absorb more than 90%of sunlight.The evaporation efficiency under 1 k Wm^-2light intensity is 86.32%,which is much higher than the ACS without carbonized layer(50.15%).The ion contents of simulated seawater distillate are much lower than that of drinking water and has good desalination ability.3.Clay-based aerogel(ATC)was prepared by using ATP as the raw material,CMC as carrier,freeze-drying molding and Al³⁺as cross-linking agent.And then soot carbon was deposited on the surface as photothermal conversion layer to obtain photothermal material(FATC).The lower water conducting layer shows light weight(0.0219 gcm^-3),self-floating,super hydrophilic and low thermal conductivity(0.0324 Wm^-1K^-1),and the upper photothermal layer has good light absorption(95%)and hydrophobicity(water contact angle is about 132°).The evaporation efficiency under 1 k Wm^-2 light intensity is 84.08%,which is much higher than the ATC without photothermal layer(48.04%).The ion contents of simulated seawater distillate are much lower than that of drinking water and has good desalination ability.