Preparation Of Dialdehyde Cellulose Based Composite Aerogel And Its Adsorption And Degradation Of Congo Red

The rapid development of industry leads to increasingly serious water pollution.Dyeing wastewater is one of the industrial wastewaters with great harm and difficult to treat due to high biological toxicity and chromaticity at present.With the increasing awareness of environmental protection,an increasing number of scholars are devoted to water treatment research.How to develop a green,low-cost and efficient water treatment material are becoming a research hotspot.Cellulose,as a biomass material with abundant sources,is one of the preferred raw materials for water treatment.However,the high crystallinity and tight molecular structure of pure cellulose lead to poor adsorption performance,which are limited to its application for the field of water treatment.In this thesis,after the selective oxidation of microcrystalline cellulose（MCC）to obtain dialdehyde cellulose（DAC）,the composite aerogel adsorption material was prepared by sol-gel,freeze-drying,crosslinking with chitosan（CS）and glucose（G）.Furthermore,composite aerogel photocatalytic material was prepared by modification with the bioadhesive agent polydopamine（PDA）and titanium dioxide nanoparticles.The contents and the results of the study are as follows:（1）DAC was prepared by selective oxidation of hydroxyl groups on C2 and C3positions in MCC using sodium periodate.SEM and FTIR characterization showed that compared with MCC,DAC modified by oxidation exhibited a new aldehyde absorption peak,its crystallinity and thermal stability decreased.However,its porosity increased significantly.The aldehyde group content of DAC was highest when the concentration of sodium periodate was 0.06 mol/L.（2）DAC/CS/G（DCG）composite aerogel was prepared by crosslinking reaction between DAC having different oxidant concentrations and CS and glucose（G）.The characterization results of SEM,BET and FTIR showed that the pore structure of DCG-0.06 was evenly distributed,with a specific surface area of 4.36 m²/g.DAC was bonded to CS and G by schiff base and hydrogen bond in the composite aerogel.The adsorption performance of DCG on Congo red dye（CR）showed that when the concentration of DAC oxidant in DCG was 0.06 mol/L,the temperature of CR solution was 55℃,p H=3,the input amount of DCG was 0.5 g/L,and the adsorption reaction time was 240 min,the maximum adsorption amount of DCG-0.06 reached 619.69 mg/g.The adsorption process of DCG to CR was consistent with the quasi-secondary adsorption kinetic model,the Langmuir adsorption isotherm model and the adsorption thermodynamic model withΔG<0,which indicated that the adsorption of CR dye by DCG was spontaneous monolayer adsorption mainly by chemisorption.（3）DA/TiO₂-DAS composite aerogel was prepared by using DAC and chitosan（CS）as carriers and polydopamine（PDA）as the binder,doped with nano-TiO₂.The characterization results of SEM,BET and FTIR showed that the nano-TiO₂was uniformly loaded onto the DAS molecules under the adhesion of PDA.The composite aerogel prepared with different DA addition amouts all had a three-dimensional network structure of micropores,in which the pore structure of DA/TiO₂-DAS-2 was evenly distributed and its average pore size was only 12.59 nm.The DA/TiO₂-DAS with added DA had optical response in the range of 200～800 nm.Under UV photocatalytic conditions,when the input amount of DA/TiO₂-DAS-2 was 0.8 g/L,CR concentration was 20 mg/L,p H=6,and photocatalytic time was 90 minutes,the degradation rate of CR could reach 99%.The degradation rate of DA/TiO₂-DAS-2 could reach 40%under simulated visible light conditions for 120 min.·O₂^-,·OH,and h⁺all participated in the photocatalytic degradation of CR,with·O₂^-playing a major role.The degradation rate of DA/TiO₂-DAS-2 still reached 70%after five degradation cycles.