Preparation Of Cellulose Aerogels And Their Application In Dye Wastewater Treatment

In recent years,with the continuous development of China’s printing and dye industry,the dye wastewater has become an important pollution source that destroy our ecological environment.Among the dye wastewater,the pollution of organic dye is particularly serious,and needs to be treated urgently.Traditional treatment methods for organic dye wastewater include chemical precipitation,biological treatment,etc.However,the shortcomings of these methods,such as low treatment efficiency and high cost,limit their application.Therefore,it is necessary to develop new high-performance materials for the treatment of organic dye wastewater.Adsorption and photocatalysis are two common methods to treat organic dye wastewater in recent years,which have several advantages,for example high efficiency,cost-effectiveness and eco-friendliness.Cellulose aerogels have shown good application prospects in adsorption,catalysis and other fields because of their renewability,high porosity,high specific surface area,high reactivity,and so on.In this thesis,bacterial cellulose（BC）was used as the substrate to prepare cellulose aerogels to achieve high-efficiency adsorption and photocatalytic degradation for organic dyes,and achieve the recycling of cellulose aerogels.The detailed work is as follows:（1）Crosslinked BC aerogels were prepared by one-pot method with BC as substrate,BTCA as crosslinking agent and SHP as catalyst.The result of FT-IR shows that the spectrum of crosslinked aerogel appeared ester bonds.Combined with the results of crystallinity,surface morphology and porosity of aerogel,it is proved that BC was successfully crosslinked with BTCA.The effects of BC concentration,BTCA concentration,p H value,and temperature on the adsorption properties of BC/BTCA aerogels for methylene blue as well as the changes in mechanical properties of aerogels before and after crosslinking were investigated.The results show that the adsorption quantity of BC/BTCA aerogels for methylene blue was 50.57 mg/g at 20℃.The results of cyclic compression and dimensional stability show that the mechanical properties of BC/BTCA aerogels are greatly improved,which implies that BC/BTCA aerogels can meet the requirements of long-term service in water environment.In addition,the adsorption-desorption cycle test of cross-linked BC aerogels was carried out.The results show that the cross-linked BC aerogels had a maximum adsorption quantity of 45.83 mg/g for methylene blue,which is 90.62%of initial BC aerogels.This indicated that crosslinked aerogels had good adsorption capacity and cycling stability.（2）Using BC as substrate,KH550 as coupling agent and TiO₂/ZIF-8 composite powder as photocatalyst,composite BC aerogels with amphoteric adsorption and photodegradation performance were prepared.The resulting composite BC aerogels had evident adsorption-degradation capacity for methylene blue（MB,cationic dye）and greatly improved adsorption performance for Congo red（CR,anionic dye）.Firstly,in situ growth of ZIF-8 on the surface of TiO₂was used to prepare TiO₂/ZIF-8 composite powder.The results of FT-IR,XRD and SEM show that ZIF-8 was successfully grown on the surface of TiO₂.Secondly,BC/KH550 aerogels were prepared by one-pot method with BC as substrate and KH 550 as crosslinking agent.Finally,TiO₂/ZIF-8 composite powder was loaded on the surface of BC/KH550 to obtain composite BC aerogels.The adsorption properties of MB and CR on composite BC aerogels and the photo-degradation performance for MB were explored.The results show that the obtained aerogel had excellent adsorption capacity for both cationic and anionic dyes.The adsorption quantity and exhaustion rates of obtained aerogel were 4.5 mg g^-1and 39.42%for MB and10.61 mg g^-1and 92.8%for CR,respectively.At the same time,composite aerogels also have excellent photo-degradation performance.After adsorption-degradation measurement,the overall removal rate of MB by composite aerogel exceeded 98%.After three cycles,the removal rate of MB within 120 min can still reach 90.56%.These results show that composite BC aerogels had effective adsorption and photo-degradation capacities for cationic and anionic dyes,and have certain application prospects in dye wastewater treatment.