Preparation Of Nanocellulose Based Solar-Driven Interfical Evaporator And The Study On Its Water Treatment Performance

With the continuous growth of population and the continuous development of industry,the shortage of fresh water resources and water pollution have become the common problems faced by human society.In recent years,a lot of methods have been developed to produce clean water,but these methods are often faced with the disadvantages of high energy consumption and high cost.Solar energy is the most abundant renewable energy on earth.Seawater desalination by solar evaporation is a low-cost and sustainable way to produce fresh water.Traditional solar evaporation methods are often faced with low photothermal conversion efficiency,slow evaporation rate and other shortcomings,but the interface solar evaporation method emerging in recent years can concentrate heat on the water-air interface to achieve efficient water evaporation.Evaporator is the most important part of interfacial water evaporation,and its water evaporation capacity mainly depends on photothermal materials and matrix materials.Molybdenum disulfide nanosheets have nearly 100%light absorption in the near infrared band,which is very suitable for the light absorption unit of evaporator.Cellulose nanofibers（CNF）are a kind of biomass material with a wide range of sources and environmental friendliness,which has the characteristics of super hydrophilic and good mechanical properties,and are suitable for the matrix material of interfacial evaporator.The photothermal aerogels based on these two materials have potential application prospects in the field of water evaporation driven by solar energy.In addition,the surface of nanocellulose contains rich oxygen-containing functional groups,which can provide a large number of adsorption sites for dye molecules in industrial printing and dyeing wastewater.At the same time,aerogel has the characteristics of large specific surface area and high porosity,so it is very suitable as an adsorption material for wastewater treatment.Therefore,the hybrid aerogel can be used in the treatment of seawater desalination and industrial printing and dyeing wastewater.In view of the above background,the main research content of this paper is as follows:（1）Preparation and the study on physicochemical properties of CNF/Molybdenum disulfide nanosheets biomimetic hybrid aerogel（CMoA）:Molybdenum disulfide nanosheets with good morphology were prepared through the synergistic effect of mechanical agitation and ultrasonic stripping.Molybdenum disulfide nanosheets were blended with cellulose nanofibers（CNF）and sodium alginate（SA）.Inspired by the wood structure of plants,a hybrid aerogel with vertical channels arranged in parallel was prepared by applying temperature gradient accurately through ice template method.The mechanical properties of the system are greatly improved by chemical intersections.Due to the superhydrophilicity of CNF and the design of bionic wood structure,the hybrid aerogel prepared has good water transport ability,molybdenum disulfide nanosheets also give it good photothermal conversion ability,low thermal conductivity aerogel has good thermal management ability,in addition,the composite aerogel can also significantly reduce the enthalpy of evaporation of water molecules.（2）Study on the interfacial water evaporation performance of CMoA:Taking CMoA as the interfacial solar evaporator,the pure water evaporation performance of CMoA was investigated at first.The evaporation rate of CMOA under one sun is 1.8918kg·m^-2·h^-1,and the evaporation efficiency is 92.31%.The evaporation rate is stable under long-term use.There are a lot of salt and other impurities in seawater,so we investigated its evaporation performance in high concentration brine and its interface evaporation decontamination performance by various means.It was found that CMoA could also realize long-term stable evaporation in high concentration brine,and could substantially remove pollutants in water.Finally,we designed a small outdoor device to test its evaporation performance in an outdoor environment.CMoA shows good evaporation capacity and has a potential application prospect in seawater desalination.（3）Study on the adsorption performance of Cationic dyes:A typical cationic dye methylene blue was selected to further explore the adsorption effect of CMoA on industrial printing and dyeing wastewater to explain its application potential in complex water environment.In the adsorption experiment,we systematically investigated the effects of adsorption time,adsorbent concentration,adsorbent dosage,temperature and pH on the adsorption process,and used a variety of kinetic models and isotherm models to study the mechanism of the adsorption process.The experimental results showed that the adsorption process followed Langmuir isothermal model and quasi-second-order kinetic model.Monomolecular adsorption and chemisorption are the main adsorption methods,and the maximum adsorption capacity can reach 316.3mg/g.Thermodynamic results show that the adsorption of methylene blue by CMoA is a spontaneous entropy-increasing and endothermic process.Finally,we studied the recycling and regeneration performance of CMoA.After five adsorption and desorption cycles,the adsorption capacity of CMoA decreased by 28.8%,indicating that it has good recycling performance.