Preparation Of Cationic Nanofibrillar Cellulose Based Aerogel And Its Adsorption And Photodegradation Of Dyes

Dye wastewater from printing and dyeing,textile and printing industries is the main part of industrial wastewater,which usually has high biological oxygen consumption and chemical oxygen consumption,as well as high color,high toxicity,and non-degradable.If it wasn't timely treated that will have a great threat to water creatures and human health.So the development of new and efficient materials capable of treating dyes has become a top priority.In this paper,cationic nanofibrillar cellulose(C-NFC)was prepared from bamboo pulp.Then,C-NFC/CS aerogel-type adsorbing materials and N-doped TiO2/C-NFC aerogels that integrated the adsorption and photo-degradation were prepared by using C-NFC as carrier.The primary achievements are as following:(1)The bamboo pulp pretreated by 2,3-epoxypropyltrimethylammonium chloride(EPTAC),and then the C-NFC suspension was obtained by the high-pressure homogenization.The C-NFC suspension was subsequently prepared into the transparent cellulose nanopaper by drying.The C-NFC suspension and nanopaper were characterized by conductivity titration,FT-IR,XRD,TEM and SEM.The mechanical properties and oxygen barrier properties of cellulose nanopaper were also studied.The results showed that the content of trimethylammonium chloride group increased with the amount of EPTAC adding.The process of chemical pretreatment did not destroy the crystalline structure of cellulose that was cellulose I.The degree of nanofibrillation also increased with the amount of EPTAC adding,but the average degree of polymerization was declined.The diameter of C-NFC1.0 was 6.3 nm,and both of the suspension and resulting nanopaper show high light transmittance.The tensile strength of C-NFC1.0 is up to 160.7 MPa and the elastic modulus is up to 6.5 GPa,which is higher than that of C-NFC0.5.However,the oxygen barrier properties of C-NFC0.5 were better than that of C-NFC1.0.The oxygen barrier properties of C-NFC0.5 were even better than those of the ideal oxygen barrier material that is ethylene-vinyl alcohol copolymer(EVOH)film.(2)C-NFC/chitosan(CS)aerogels with excellent mechanical properties were prepared by two-step freeze-drying method using C-NFC as carrier and epichlorohydrin as crosslinking agent.The products were characterized by FT-IR,XRD,and SEM.The effects of the mass ratio of C-NFC and CS,the pH value and temperature on the adsorption properties of the aerogels were discussed.In addition,the adsorption kinetics and adsorption isotherm were studied.Finally,the application of composite aerogels in dye separation and adsorption reproducibility were investigated.The results showed that the mass ratio of C-NFC and CS had little effect on the adsorption capacity of composite aerogels,while the pH value and the temperature had a great influence on the adsorption capacity of the composite aerogels.And the C-NFC/CS=1:1 aerogel adsorption capacity to Acid red 88 was up to 377 mg?g-1,at pH 7,25 oC,which was 1.4 times that of C-NFC aerogel and 2 times that of CS aerogel.The adsorption process was fitted well to the second-order kinetics and Langmuir isotherm,indicating a chemisorption nature and the monolayer adsorption.C-NFC/CS(1:1)aerogels also have a strong selectivity adsorption to the mixture dye solution of methylene blue and acid red 88.In addition,after 5 cycles of adsorption-desorption,the removal rate of the composite aerogels for Acid red 88 is still as high as 96%,and the structure of aerogel is intact.(3)N-doped TiO2/C-NFC composite aerogels were prepared by one-step hydrothermal method using C-NFC as carrier,urea as nitrogen source and titanium sulfate as titanium source.The aerogels were characterized by TEM,SEM,EDX,FT-IR,XRD and XPS.The adsorption and photo-degradation performance of aerogels towards methyl orange(MO)were studied.The adsorption kinetics and adsorption isotherm were also discussed.Finally,the reusability and degradation mechanism of the composite aerogel were investigated.The results show that the TiO2 in the composite aerogel is anatase and N successfully enters the TiO2 lattice.The adsorption process of the aerogels was fitted well to the second-order kinetics and Langmuir isotherm,indicating a chemisorption nature and the monolayer adsorption.The theoretical maximum adsorption capacity of 10N10Ti-NFC towards the MO dye was 17.6 mg?g-1.In addition,the composite aerogel exhibited excellent photo-degradation performance,and the degradation rate of the MO dye was 99.9% within 90 min,and it had excellent reusability.And the composite aerogel exhibits high photocatalytic activity under simulated sunlight mainly because the band gap of TiO2 can be reduced due to the doping of N.