Preparation Of Polysaccharide-based Aerogels And Their Performance In Water Treatment

Aerogel is a new type of low density and amorphous material with three-dimensional porous network structure.In recent decades,because of its many excellent properties,such as thermal,acoustic,mechanical,optical and electrical properties,the aerogel has been listed one of the top ten pop technologies.The three-dimensional porous network structure endows the aerogel with unique values in the field of adsorption.With the expanding range of aerogel application,the preparation of aerogel is continuously update,and the selection range of raw materials has kept expanding.At present,the domestic research mainly focused on the preparation of new types of aerogels,various kinds of composite aerogels and the exploration of new applications of aerogels.To enrich and develop the theory and practice of the aerogel and widen its application fields,a series of new aerogels were prepared by using natural polysaccharide as the main raw material and their applications were also investigated in this paper.1.A highly efficient absorbent(cellulose based aerogel)with a low density(p<0.034 g/cm3,?>98.5%)and high mechanical strength was fabricated via a novel physical-chemical foaming method,plasma treatment and subsequent silane modification process.This aerogel has perfect 3D skeleton and interconnected pores similar to honeycomb,which are favorable to oil adsorption and storage.More importantly,without introducing additional micro/nanoparticles,the rough micro/nano structure of the surface was directly constructed using plasma irradiation in this study.The low surface energy substrate was further introduced using a simple physical-soaking method and the resulting aerogel exhibited excellent superhydrophobicity(WCA>156°)and superoleophilicity(OCA=0°),which can selectively and efficiently absorb various oils or organic solvents from polluted water.More interestingly,this aerogel exhibits excellent mechanical abrasion resistance and corrosion resistance even in strong acid,alkali solution and salt marine environment.The aerogel could be reused more than 30 times after removal of the absorbed oil by rinsing with ethanol.2.Absorbent cotton using as raw material was dissolved in NaOH/urea/water system at low temperature to obtain regenerated cellulose solution.Followed by sol-gel and freeze-drying process,regenerated cellulose aerogel was prepared.TiO2 particles with different size were modified by silane coupling gent and then were spray-coated onto the regenerated cellulose aerogel to achieve superhydrophobicity.The developed aerogel exhibited excellent superhydrophobicity(WCA= 172°)and superoleophilicity(OCA = 0°).More impressively,the as-prepared aerogel can even keep its superhydrophobicity even after sharp friction or being immersed in strong acid,alkali solution and high salt environment.Furthermore,the aerogel could separate various oil/water mixtures with a high separation efficiency(of up to 99%)and good reusability(at least 40 cycles).3.Inspired by the underwater superoleophobicity of seaweed,two kinds of alginate-based aerogels were prepared through incorporating reinforcement(GO and NFC,respectively)into ALG matrix by using a facile combined freeze-drying and ionic cross-linking method.The wetting properties of the aerogels in air and water were investigated,and the formation mechanism of the underwater superoleophobicity of the aerogels was studied.The results show that the aerogels have excellent underwater superoleophobicity(OCA>160°),salt-tolerance and antifouling properties.More impressively,the as-prepared aerogels can even keep its underwater superoleophobicity and high hydrophilicity after being immersed in seawater for 30 days,indicating their good stability in marine environments.Furthermore,the alginate-based aerogels could separate oil-seawater mixtures with a high separation efficiency(>99.6%)and good reusability(at least 40 cycles).The facile and green fabrication process combined with the excellent separation performance and good reusability makes them possible to develop engineering materials for oil-water separation in marine environments.4.The nanofibrillated cellulose(NFC)/chitosan(CS)aerogel was prepared by freeze-drying method using NFC as reinforcement and CS as matrix.The three-dimensional(3D)network structure of the aerogel and a large number of amino and hydroxyl functional groups are beneficial to the efficient adsorption of heavy metal ions.The adsorption performance of NFC/CS aerogel for Cu2+ was studied.The effects of such factors as solution pH value,adsorption time and initial Cu2+ concentration on adsorption performance of the aerogel were investigated.The adsorption isotherm and kinetic modeling of Cu2+ on NFC/CS aerogel were studied.The results show that the process follows a pseudo second-order kinetics and Langmuir isotherm model.The adsorption of Cu2+ on the aerogel belongs to monolayer adsorption,and it is mainly chemical adsorption.The aerogel has good adsorption capacity for Cu2+,and the maximum adsorption capacity is up to 81.21mg/g.In addition,after 5 adsorption/regeneration cycles,the adsorption capacity of Cu2+ was still above 85%.The metal ion adsorption capacity and reusability of the aerogel make it a promising adsorbent for wastewater treatment.