Preparation And Application Of Cellulose Aerogel With High Water Absorption And Retention Properties

With the world population growth and population aging,people ' s demand for disposable health supplies has increased significantly.Currently,polyacrylic superabsorbent materials dominate the market.However,they are non-biodegradable and will cause great damage to the environment.Using renewable and biodegradable natural polymer materials to replace petroleum-based materials in preparation of superasorbent materials with high water retention is desirable.Cellulose has the advantages of being readily degradable and available,cheap,and highly biocompatible,but its water absorption capacity is only moderate.Although many studies have been devoted to improving the water absorption properties of cellulosic materials,in most cases their degradability and non-toxicity were compromised due to the use of toxic additives.In addition to the above-mentioned factors,the water absorption capacity,water absorption rate,water retention performance and mechanical properties of the cellulose-based water-absorbing and water-retaining materials also determine the upper limit of its application performance.Cellulose aerogel combines the advantages of high porosity and large specific surface area of traditional aerogels and the excellent properties of cellulose itself,and is an ideal substrate as a superabsorbent.In this dissertation,cellulose aerogels were prepared by using sodium carboxymethyl cellulose(CMC-Na)as a hydrophilic polymer,the non-toxic and readily available citric acid(CA)as the cross-linking agent,and cellulose nanofibers(CNF)as the basic building units.Cellulose aerogels were prepared by freeze drying and heating cross-linking after mixing uniformly.The effects of different preparation and application conditions on the water absorption and water retention properties of aerogels were systematically explored.First,we investigated the effect of freezing temperature on the water absorption and water retention properties of aerogels.It was found the water retention rate of the aerogel prepared at a freezing temperature of-196 ? reaches 97.4%,which also has excellent water retention performance.The water absorption capacity(in 1 min)of the aerogel prepared at-18 ? is 80.8 g/g with rapid water absorption.Subsequently,we chose the aerogels prepared at a-80 °C(with the maximum water absorption of 157 g/g)to test the effects of p H and electrolytes on the water regain.It is found that when p H is between 5 and 7,the aerogel has a larger water absorption,and the aerogel has a lower water absorption under strong acid and alkali conditions.When the cation molar concentration in salt solution is the same,with the increase of cation valence,the water absorption of aerogel is lower,and with the increase of cation concentration,the water absorption of aerogel will also decrease.Finally,the water retention properties of the aerogels under different conditions were investigated.After centrifugation at 3000 and 15000 r/min for 30 min,the water retention rates of the aerogels were 100% and 75.6%,respectively.The water-saturated aerogel was heated at 40 °C for 11 hours,and the water retention rate was still up to 76.9%.When the dosages of CMC-Na,CA,and CNF were 7.000 wt%,0.005 wt%,and 0.100 wt% of the deionized water,respectively,the aerogels frozen at-80 ? then baked at 160 ? for 40 min had a maximum water absorption of 157.0 g/g.These aerogels also display excellent water retention performance,making them greener alternatives to petroleum-based superabsorbent materials with great potential in the fields of disposable hygiene products,agricultural forestry,and biomedicine.