Preparation Of Cellulose-based Composites And Their Adsorption-catalytic Properties

The rapid growth of global industry has led to a number of environmental problems,such as water pollution.Organic dyes MB and antibiotics TC are common toxic and hazardous pollutants that persist in the environment.MB and TC can directly disrupt the balance of ecosystems and pose a threat to humans by contaminating drinking water.Conventional methods of MB and TC removal may have disadvantages such as low efficiency,complex process,secondary pollution,and non-repeatable.Therefore,efficient removal of MB and TC by green methods is a major part of current research.Adsorption technology is widely used for its advantages of simple operation,high efficiency,no secondary pollution,and high economic efficiency,and photocatalysis is an advanced oxidation technology for efficient and green removal of pollutants.In this work,cellulose,was chosen as the raw material due to it is resourceful,inexpensive and green,and different cellulose based adsorbents and photocatalysts were prepared by grafting polymers,in situ growth of MOFs,metal doping and molecular imprinting,aiming to improve the ability of cellulose to remove organic pollutants.The specific work is as follows:1.ZIF-8/MAA adsorbent was prepared by simply loading ZIF-8 into PAA-grafted MCC aerogel.The successful preparation of the adsorbent was demonstrated by using XRD,FTIR,SEM,XPS and BET characterization.The prepared adsorbent exhibited a high specific surface area（641.0159 m²/g）,resulting in a maximum adsorption capacity of 1492.99 mg/g,as well as a good recovery effect,and showed good MB adsorption performance even after five times of reuse.The kinetic model fitting results showed that the adsorption process of MB on ZIF-8/MAA aerogel was controlled by both intraparticle diffusion and boundary layer diffusion.In addition,the Langmuir isotherm model fitted the adsorption isotherm of MB better,indicating that the adsorption of MB is a homogeneous monolayer adsorption process.Thermodynamic studies indicate that the adsorption process of MB is exothermic and physicochemical.The mechanism of MB adsorption was studied and illustrated which may involve pore filling,hydrogen bonding,π-πstacking and electrostatic attraction.2.Based on the first part of the work,Fe/ZIF-8@cellulose biosorbents were successfully synthesized by applying the in situ growth of Fe-doped MOFs strategy.The successful preparation of the adsorbent was demonstrated using XRD,FTIR,SEM,XPS and BET characterization.The results showed that the adsorption capacity of TC was greatly improved after doping with Fe.The adsorption behavior of TC on Fe/ZIF-8@cellulose biosorbent was in accordance with the quasi-secondary kinetics and Langmuir isothermal adsorption model with a maximum adsorption capacity of 1359.2 mg/g,which exhibited chemisorption and monolayer adsorption.The adsorption mechanism of the adsorbent on TC was proposed based on the synergistic effects of surface complexation,electrostatic attraction,π-πinteractions and hydrogen bonding.3.Ag/ZIF-8@cellulose aerogel with excellent photocatalytic degradation performance was prepared.Firstly,Ag nanoparticles were loaded onto the surface of ZIF-8 by a reduction method and then they were loaded onto the pore wall of cellulose aerogel using in situ growth method.The successful preparation of the photocatalyst was demonstrated by using XRD,FTIR,SEM,XPS and other characterization methods.The synthesized Ag/ZIF-8@cellulose aerogels exhibited excellent photocatalytic activity and photostability due to the high specific surface area of ZIF-8 and the interaction between Ag nanoparticles and ZIF-8 that suppressed the carrier complexation rate.The MB degradation rate reached 86%after 150 min of visible light irradiation.In addition,the photoluminescence,and trapping experiments of Ag/ZIF-8@cellulose aerogels were also investigated to speculate the degradation mechanism of MB by photocatalyst,and it was confirmed that·OH and·O₂^-radicals play a very important role in the degradation process.4.Molecularly imprinted Zn O/ZIF-8@cellulose aerogels were prepared at room temperature using a simple synthetic modification method.The characterization results demonstrated the successful preparation of molecularly imprinted Zn O/ZIF-8@cellulose aerogels.Through the photocatalytic degradation experiments of different antibiotics in wastewater,it was found that the molecularly imprinted Zn O/ZIF-8@cellulose had high photocatalytic activity and good selectivity,and the TC degradation rate reached nearly 80%after 40 min of visible light irradiation.In addition,the synthesized photocatalysts showed excellent photocatalytic activity and photostability due to the high specific surface area of ZIF-8 and the interaction between molecularly imprinted Zn O and ZIF-8 which suppressed the carrier complexation rate.Finally,the degradation mechanism of TC was inferred by trapping experiments and photoluminescence,and it was confirmed that·O₂^-and·OH radicals play a very important role in the degradation process.