Thermal Localized Micro-nano Structure To Enhance The Performance Of Solar Desalination

Solar desalination technology is not only an efficient,environmentally friendly and sustainable way to obtain clean fresh water,but also a low-carbon environmental protection scheme to effectively solve the water crisis.In recent years,the development of micro-nano technology provides new ideas and opportunities for high-efficiency solar seawater desalination.Among them,solar-powered steam generation at the interface of micro-nano structures shows great potential for high energy conversion efficiency in seawater desalination and wastewater treatment.Based on the principle of mass transport driven by capillary force in micro-channels and the photo-thermal effect of local surface plasma of precious metals,this paper designed a thermal local micronano structure of mass transport driven by capillary force in micro-channels,which greatly improved the efficiency of solar seawater desalination.The main research contents are as follows:(1)A thermal local micro-nano structure driven by capillary force for mass transport is proposed and designed,and its effectiveness in promoting solar seawater desalination process is verified by experiments.Firstly,based on the capillary force in the microchannel and the photo-thermal effect of plasma,a thermal local micro-nano structure was designed to drive mass transport by the capillary force.Secondly,a set of solar seawater desalination experiment and fresh water collection device is designed and processed for the designed micro-nano structure.Finally,the effectiveness of the thermal local micro-nano structure in improving the performance of solar seawater desalination is verified experimentally.(2)The influence of the variation of structural parameters in the thermal local micro-nano structure on the production efficiency of fresh water in seawater desalination is studied and the optimal structural parameters are determined.Firstly,the thermal local micro-nano structures of tapered holes were fabricated by surface projection micro-stereo-lithography.Then,through experimental tests,the key parameters and main factors affecting the production efficiency of structural fresh water were determined,and the main mechanism of improving the performance of solar seawater desalination by thermal local micro-nano structure was systematically analyzed.The results show that the structure parameters of the sample mainly affect the fresh water production efficiency in the process of solar seawater desalination by affecting the morphology of the ultra-thin water film formed on the surface of the sample: the thinner and better continuity of the water film on the surface of the sample,the higher the fresh water production efficiency.(3)In order to further improve the thermal local micro-nano structure of solar seawater desalination performance,a "gold resin" micro-nano structure was designed and prepared,and the mechanism of local surface plasma effect of precious metals in enhancing the performance of solar seawater desalination was systematically studied and analyzed.Firstly,through metal thermal evaporation,a nanoscale Au film layer(50nm)was evaporated on the surface of the above-mentioned micro-nano structure to obtain the gold-resin structure.Subsequent research results show that the plasma photothermal effect of Au nano-film can effectively improve the freshwater production efficiency of micro-nano structure,reaching 186.86%.Through the study,we found that the strong local surface plasmon resonance on the structure surface of the gold film can achieve a great local and field enhancement of the surface electric field,the local surface plasmon non-radiation attenuation leads to a great increase in the surface temperature,so as to accelerate the generation of surface seawater steam.Finally,in view of the problem that the crystalline salt on the surface of the sample clogs capillary pores and impedes the continuous transport of seawater in the process of seawater desalination,we covered the surface of the sample with an ultra-thin seawater dispersing film,which not only effectively solved the problem of the blocking of capillary pores by crystalline salt,but also further improved the efficiency of seawater desalination.