Preparation Of Attapulgite-Based Photothermal Aerogels And Its Application In Seawater Desalination Research

Desalination of seawater using solar desalination technology to alleviate the shortage of freshwater resources is considered one of the most promising desalination technologies.Interfacial solar photo-thermal evaporation concentrates thermal energy at the water-air interface,which can effectively avoid heat transfer between the photo-thermal material and the water body which significantly improves the energy utilization efficiency.At present,it is mainly from three aspects of improving light absorption,reducing heat loss and improving water transfer performance to improve the performance of interfacial solar evaporator for photo-thermal evaporation.Aerogel is an ideal material for water treatment due to its low density,high porosity and low thermal conductivity.Among them,clay-based aerogels have been widely studied due to the advantages of environmentally friendly and low-cost raw materials,but their poor mechanical properties and poor hydrophilicity have limited their further application in desalination.Therefore,in this paper,we chose environmentally friendly and low-cost attapulgite（ATP）as the raw material,by selecting different photothermal materials and cross-linking agents,we prepared attapulgite based composite aerogels with different compositions and structures.And the performance of different aerogels for photothermal evaporation and desalination of seawater has been investigated with aerogels.（1）By modifying ATP with copper sulfide（Cu S）,we obtained Cu S@ATP with excellent photothermal properties,which was then cross-linked with potato starch（PS）and then freeze-dried to obtain a low-density composite photothermal aerogel（Cu AP aerogel）with abundant pores.Cu AP aerogel has over 97%light absorption performance in the full spectral range,and combined with its low thermal conductivity and superhydrophilicity,thus,Cu AP aerogel has excellent photothermal evaporation performance,and its photothermal evaporation rate of pure water under 1 sun irradiation is 1.57 kg m^-2 h^-1.It also shows excellent desalination performance in seawater desalination tests,The concentrations of major metal ions in the water after desalination are significantly reduced by several orders of magnitude.（2）Inspired by the vascular tissue of sugarcane,a biomimetic aerogel（PAS aerogel）with vertical pore structure similar to the vascular bundle of sugarcane was prepared by unidirectional freezing technique.Firstly,poly（dopamine）（PDA）was used to modify the ATP（PDA@ATP）,and then it was cross-linked with sodium alginate（SA）,finally the aerogel with vertical pore structure was obtained by liquid nitrogen pre-freezing and freeze-drying.PAS aerogels have excellent mechanical elasticity,and they maintain excellent mechanical properties after many consecutive compression cycles.The super hydrophilic vertical pore structure inside PAS aerogel ensures sufficient supply of water during evaporation,and together with the excellent light absorption and low thermal conductivity of aerogel,its photothermal evaporation rate of pure water under 1 sun irradiation is 1.71 kg m^-2 h^-1.Meanwhile,PAS aerogel has excellent salt tolerance,its evaporation efficiency is still relatively high in high concentration of salt water,and in the actual outdoor evaporation test,the daily water production of PAS aerogel in sunny days is 3.92 kg m^-2 d^-1,which satisfies the daily water requirement of human body.