Recycling Of Waste Cotton Fiber And Its Application In The Field Of Solar Steam Generation

With the development of economy and improvement of living standard,the demand for textiles is increasing,at the same time,there is also the problem of short life cycle of textiles,which in turn leads to an increasing number of waste textiles.At present,waste textiles are mainly disposed of by incineration and landfill,which not only pollute the natural environment,but also cause serious waste of resources.In the waste textiles,cotton and cotton textiles account for about one-third,while cotton has significant biodegradability and recyclability and other advantages.Therefore,how to achieve the recycling of waste cotton textiles while giving it high added value has significant research significance.Among them,the aerogel prepared from cotton has been widely used by virtue of its remarkable physical and chemical effects.In this paper,cotton fiber-based aerogel was constructed based on natural waste cotton by combining physical and chemical methods;and combined with high-temperature carbonized treated cotton rods as light-absorbing materials,an aerogel photothermal evaporator with the advantages of low cost,scalability and biodegradability was prepared for water treatment,providing a new idea for the high-value utilization of waste cotton textiles.Specific work was carried out as follows:(1)In this paper,natural cotton fibers were used as raw materials,and the fibers were sheared and dispersed by means of high-speed shearing,repeatedly washed with water to remove impurities,and the dispersed cotton fibers were chemically cross-linked by means of epichlorohydrin,and then the cotton fiber-based aerogels were prepared by freeze-drying.The optimal amount of the cross-linking agent epichlorohydrin used in the preparation process was determined by orthogonal experiments,and the structure and properties of the aerogels were characterized by scanning electron microscopy(SEM),infrared analyzer(FTIR),mechanical compression and other testing means.The results showed that the chemical cross-linking treatment could enhance the binding effect of the fibers and improve the dispersion uniformity of the pore structure.The density of the cross-linked cotton fiber-based aerogel was 9.8 mg/cm3,the porosity was 98.5%,and the specific surface area was 9.8 m2g-1.The contact angle between water droplets and the aerogel surface was 39.6°,indicating its good hydrophilicity,and the stress-strain curve indicated its strong mechanical properties.(2)The charcoal powder(light absorbing material)was prepared by high temperature charring and ball-milling of waste cotton sticks as raw material,ethanol was used as solvent,polyvinylpyrrolidone was added to improve the liquid phase dispersion of charcoal powder,and methyltrimethoxysilane was added as coupling agent.The charcoal powder solution was sprayed onto the surface of the cotton fiber-based aerogel prepared above by a spray gun,and it was named as charcoal powder-cotton fiber-based aerogel.The structure and properties were characterized using scanning electron microscopy(SEM),infrared analyzer(FTIR),and thermogravimetric analyzer.The results showed that the charcoal powder solution with the addition of polyvinylpyrrolidone and methyltrimethoxysilane was more tightly bound to the aerogel and evenly distributed.Thermal weight loss analysis showed that the thermal stability of the charcoal powder-cotton fiber-based aerogel was significantly higher than that of the cotton fiber-based aerogel alone,and the contact angle between water droplets and the surface could reach 160°,indicating that the prepared photothermal aerogel could self-float on the water surface.(3)Three types of charcoal powder-cotton fiber-based aerogels were prepared by adding polyvinylpyrrolidone and methyltrimethoxysilane to the charcoal powder solution,respectively,and their photothermal water evaporation properties were tested.The results showed that their light absorption in the wavelength range of 250~2500 nm was more than 90%,and the thermal conductivity of the three charcoal powder-cotton fiber-based aerogels were 0.049,0.043 and0.039 Wm-1 K-1,respectively.Under different solar light intensities,it was concluded that the charcoal powder-cotton fiber-based aerogels with the addition of polyvinylpyrrolidone and methyltrimethoxysilane had the best photothermal performance,and the devices were subjected to Photothermal water evaporation test,the data showed that the photothermal water evaporation rate was 1.93 kg-m-2 h-1 under 1 solar light intensity,and the calculated photothermal conversion efficiency was 82.13%.Under 1 solar illumination condition,the photothermal effect is stable after 4 cycles,and the evaporation rate is 1.46 kg-m-2 h-1.Further,the aerogel can achieve effective separation and purification of sewage containing non-volatile pollutants,and the purification rate can reach more than 99.9%.