Preparation Of Prussian Blue Decorated Porous Materials For Solar Seawater Desalination

Freshwater shortage has become a serious global problem.This problem can be efficiently alleviated by seawater desalination.At present,different seawater desalination technologies have been well developed,such as reverse osmosis,membrane distillation,and solar-enabled seawater desalination.Among them,solar-enabled seawater desalination has attracted extensive attention,since it is a green and efficient technology.The key for solar-enabled seawater desalination is to develop efficient photothermal conversion membranes.The present studies mainly focus on floating single/double photothermal membranes on seawater and generate water vapor under sunlight.These membranes include carbon sponges,aerogels and hydrogel,showing excellent seawater desalination performance.However,solar desalination still faces two mian problems.The first problem is low evaporation rate,since the nanopores in photothermal membranes can prevent the water vapor diffusion.The second problem lies in severe solid-salt crystallization on the photothermal membranes,deteriorating the seawater desalination performance.To solve the above problems,herein,two photothermal aerogels have been developed with large pore,and further applied in the inclined suspension evaporator.The solar evaporation rate can be greatly enhanced under the assistance of wind flow.The main results are listed as follows:1.Prussion blue loaded melamine foams for solar-enabled seawater desalinationPorous melamine foam(MF)was firstly modified by 3-(2-aminoethyl)-aminopropyl trimethoxysilane(NN)through a infiltration drying method,and then applied for the in situ growth of prussian blue(PB)nanoparticles.The MF exhibited a three-dimensional network structure with an average pore diameter of about 66.3?m.The pores were interconnected,and the size of Prussian blue was 1?m.The MF-NN-PB foam showed excellent hydrophilicity and strong light absorption property(absorbance:87%).Then,the MF-NN-PB foam was equipped in an inclined suspension evaporator.Under the irradiaiton of solar simulator(1.0 kW·m^-2),This device performed an evaporation rate of 1.82 kg·m^-2·h^-1under the irradiaiton of solar simulator(1.0kW·m^-2),and exhibited an evaporation rate of 2.85 kg·m^-2·h^-1under wind flow(3.0 m·s^-1)in darkness.When the evaporator was placed under both solar simulator(1 kW m^-2)and wind flow(3.0 m/s),the evaporation rate reached as high as 3.83 kg·m^-2·h^-1.During 48 h continuous evaporation test,no solid salt crystal can be found on MF-NN-PB,and the water evaporation rate remained unchanged,showing excellent stability and great application potential for seawater desalination.2.Loofah-PB foam for solar enabled seawter desalinationFresh Loofah was firstly pre-treated and then loaded by PB nanoparticles through a simple impregnation method,obtaining Loofah-PB photothermal foam.Loofah-PB showed a disordered three-dimensional porous structure with the pore size larger than 1 mm and PB particle size of?0.5?m.Besides,the Loofah-PB exhibited excellent hydrophilicity and light absorption performance,with an absorption efficiency of 78%.By using this material,an inclined evaporation device was built and exhibited an evaporation rate of 2.36 kg·m^-2·h^-1under simulated sunlight(1.0 kW·m^-2).Under the effect of wind flow(3.1 m/s),the device performed an evaporation rate of 7.06 kg·m^-2·h^-1without light irradiation.When both simulated sunlight(1.0kW·m^-2)and wind flow(3.1 m/s)were applied on the device,its evaporation rate reached as high as 14.04 kg·m^-2·h^-1.Furthermore,the device exhibited no obvious decrease on evaporation performance in the 48 h cycling evaporation experiments.Based on the large pore designing idea,two photothermal foams was developed with big pores,and can be applied for solar evaporation under wind assistance.This paper provides the foundation for the development of high-performance seawater desalination technology.