Fabrication Of Functional Cellulose-based Aerogels And Their Adsorption And Degradation Behaviors To Dyes

The high-value transformation and reuse of the waste cellulose resources from textile industry,as well as the treatment of printing and dyeing wastewater discharged by textile industry are the key problems of the green sustainable development of the textile industry.In this work,cellulose-based aerogels were prepared by chemical modification of waste cellulose from textile industry.The interaction between structure and properties was studied through controlled preparation process.Their adsorption behaviors,interaction between host guest and adsorption mechanisms were investigated.The highly efficient adsorption and porous properties of the Cu2O/cellulose-based composite catalysts were obtained by functional assembly using chemical in-situ deposition,and their catalytic properties and the degradation mechanism of the dye molecules were investigated.The results of this paper were as follows:(1)Controllable preparation and properties of cellulose-based aerogels:Cellulose-based aerogels were fabricated from waste cotton fibers through free-radical copolymerization method at low temperature.The effects of crosslinker,extra water,functional feeding ratio on the structure and performances of aerogels were experimentally investigated.The physical and chemical properties of the prepared samples were characterized as follows:SEM,FTIR,content of carboxyl amino,porosity and swelling degree.It was found that the connected porous structure of sample can be controlled by adjusting the crosslinking agent MBA and freezing water,and the number of functional groups of sponge-like samples can be controlled by adjusting functional monomer ratio during the preparation.Cellulose-based aerogels with tunable porous structure and functional functional group are possibale.The samples were successful obtained with pore size range of 20-250 ?m,carboxyl functional group range of 4.21-5.47 mmol g-1,and amino functional group range of 2.70-6.36 mmol g-1.(2)Study on adsorption behavior and adsorption mechanism of cellulose-based aerogels on dye molecules:Two organic dyes(methylene blue(MB),acid red(AR1))were used as model pollutants to investigate the adsorption characteristics of cellulose-based aerogels in aqueous solution.The effects of solution pH,temperature,initial dye concentration,and contact time on the adsorption capacity of the cellulose-based aerogels were investigated.Due to the abundant functional groups and macroporous network structure,cellulose-based aerogels exhibited remarkable adsorption performance for the removal of type dyes with an equilibrium adsorption capacity of 998 mg g-1 for MB and 523 mg g-1 for AR1.The kinetic studies revealed that the adsorption of dyes was exactly described by a pseudo-second-order kinetic model and Langmuir isotherm model,which shows that the adsorption process was mainly single molecule layer adsorption dominated by the electrostatic and hydrogen bonding interactions between the dye molecules and the cellulose-based aerogels.In additional,the samples showed better recycling performance and wider adaptability to environment.Thus,the eco-friendly cellulose-based aerogels possessed excellent potential for water purification.(3)Functionalized assembly of Cu2O/cellulose-based composite catalysts and their visible light photocatalytic performance:Cu2O nanoparticle(NP)-functionalized cellulose-based aerogels with 3D macroporous structure and abundant active sites was successfully prepared for visible-light photocatalysis via in situ deposition of Cu2O NPs on cellulose-based aerogels.The surface morphology,microstructure and phase composition of samples were characterized by SEM,TEM,XRD,BET,PL,UV-vis-NIR etc.Results show that octahedral Cu2O NPs were formed and anchored onto the surface and inner wall of the cellulose matrix,and which acted as a microreactor to prevent aggregation and protect the catalytic character of the Cu2O NPs.In particular,the separation of photogenerated electrons and holes can be enhanced via in situ deposition of Cu2O NPs on cellulose matrix.The photocatalytic performance of the Cu2O/cellulose-based composite catalysts was evaluated using degradation of methylene blue(MB)as model pollutant.The effects of catalyst dosage,initial MB concentration,and solution pH on MB photodegradation were investigated.The catalysts exhibit excellent photocatalytic properties,with higer than 95%degradation rate of MB within 60 min under visible light irradiation.Moreover,the composite catalysts was easily recycled and reused,with 80%MB degradation rate retained even after six cycles.The stability of Cu20/cellulose-based composite catalysts during catalysts was evaluated,it was found that the surface morphology,crystal structure and mechanical stability of the composite samples were maintained after 6 cycles.(4)Study on the catalytic mechanism and decomposition process of Cu2O/cellulose-based composite catalysts for MB:The XPS analyses showed that in situ Cu2O deposition in the cellulose matrix can improve the surface chemisorbed oxygen species,which plays a key role in improving catalytic efficiency.Hydroxyl radical and superoxide radical were the main catalytic activities in the process of catalysis.The catalytic mechanism of Cu2O/cellulose-based composite catalysts for MB was related with its high adsorption sites which provided by surface three-dimensional porous structures and multiple active sites of cellulose matrix.Moreover,the coordination between cellulose matrix and nanoparticles of Cu2O/cellulose-based composite catalysts was also related to the catalytic mechanism during the process of catalytic degradation of dyes.The decomposition process of Cu2O/cellulose-based composite catalysts on MB is speculated as follows:The S-Cl bond was first breaked,followed by the C-S and C-N bonds.The intermediates such as hydroquinone,resorcinol,quinone and catechol were emergenced in the process of catalysis.The results provide a theoretical and experimental basis for the application of Cu2O/cellulose-based composite catalysts in photocatalytic field.In summary,the cellulose-based aerogels were prepared from waste cotton fibers,and the controllability of the preparation process was investigated,in addition their adsorption properties of the dyes were studied.On this basis,a visible light photocatalytic system of aerogels was constructed and their catalytic degradation performance was studied.The results show that the functional cellulose-based aerogels exhibit excellent adsorption and degradation behavior of dye molecules.The results of this paper provide theoretical basis and research basis for realizing high value utilization of environmental wastes and controlling toxic and harmful substances in environment.