网状骨架CVD生长碳纳米管用于重盐水脱盐

CVD Grown Carbon Nanotubes on Reticulated Skeleton for Brine Desalination

目前,太阳能海水淡化领域通过光子管理、纳米尺度热调控、开发新型光热转换材料、设计高效光吸收太阳能蒸馏器等方法实现了界面太阳能驱动蒸汽生成,这种绿色、可持续的脱盐技术已成为近年来的研究热点。碳基材料如碳纳米管、石墨烯、炭黑、石墨等都有涵盖整个太阳光光谱的光吸收能力,是一类新型的光热转换材料。本文通过对材料进行微结构设计,使用化学气相沉积(CVD)技术,在不锈钢网状骨架上生长碳纳米管形成光热转换活性区,以实现高效光吸收、光热转换,并进一步设计了房屋型太阳能蒸发器,其中盐水表面被微米网状-碳纳米管蒸发膜覆盖,利用光热转换过程产生的热量驱动重盐水中的水蒸发产生水蒸气,最后对水蒸气进行冷凝回收实现脱盐。实验结果表明,当光照强度为1个太阳光(1 kW·m-2)时,膜表面温度迅速升高并稳定于84.37°C,对于重盐水(100 g·L-1 NaCl)的脱盐率达到99.92%,可实现稳定持续的重盐水脱盐。这种方法可用于构建多孔界面光热转换脱盐系统,对设计界面光蒸汽转化膜材料及器件,实现规模化海水淡化具有重要的意义。

Using solar energy to power evaporative processes has found various applications in desalination,wastewater treatment,and power generation among other fields.Due to its green-energy sources and energy-efficient conversions,it has gained increasing attention.However,as one of the oldest approaches,the application of solar evaporation is still limited by issues such as low evaporation efficiency,fouling,and the rapid degradation of solar absorbers.During solar evaporation processes,the solar absorbing materials are directly heated by sunlight and the generated heat is transferred to the water around the material.Within this process,in situ photo-thermalconversion is realized by absorber materials at the air-water interface.After the water is heated,it vapors continuously.Therefore,the material for solar absorption and photo-thermal conversion is key to improving the efficiency of solar evaporation processes.Currently,many approaches are being developed to achieve high-efficient solar evaporation,such as the photon management,nano-scale thermal regulation,the development of new photo-thermal conversion materials,and the design of efficient light-absorbing solar stiller.Carbon-based materials including carbon nanotubes,graphene,carbon black,graphite,etc.have broad light-absorption profiles over the entire solar spectrum,which makes them the outstanding photo-thermal conversion materials.Herein,we design a new structure and house-like solar still on the basis of carbon-based materials to achieve high light absorption,efficient photo-thermal conversion,and continuous desalination.We use the chemical vapor deposition(CVD)technique to fabricate a reticulated carbonnanotube solar evaporation membrane.Stainless steel mesh(SSM)is used as a reticulated skeleton,providing porous structures and increasing the mechanical strength of the membrane.Then the carbon nanotubes(CNTs)are grown on the reticulated skeleton to function as solar conversion structures due to their wide range of light absorption capacities.The CVD grown CNTs reticulated membrane(CGRM)is fixed in a house-like device with a sloped ceiling to condense and collect water vapors ensuring the continuous desalination of water.Our experiments show that the fabricated CGRM is hydrophobic with an average contact angle of 133.4°for a 100.0 g·L-1 NaCl solution,only allowing water vapors to pass through while rejecting salts.When the light intensity was 1 kW·m-2,the surface temperature of the membrane increased rapidly and stabilized at 84.37°C.The salt rejection rate of the system could reach up to 99.92%.To perform a comparative study,we also prepared a mechanically-filled CNTs reticulated membrane(MFRM1,MFRM2)for solar evaporation tests,which showed an inferior performance to that of the growing structure of the CGRM.Therefore,it was determined that our system might provide a potential way to harvest freshwater readily with portabletype equipment.