Preparation Of Nano-Cellulose Based Porous Composite Foam And Its Application To Remove Pollutants

Due to the special characteristics,such as good mechanical properties,high specific surface area,light weight and high porosity,etc.,foam materials are widely used in the adsorption of pollutants such as dyes,heavy metal ions,and hormones,oil-water separation and desalination,etc.Traditional foam materials are mainly acquired from fossil resources and have been widely developed because of their convenience for preparation,cheapness and excellent performance.However,petroleum-based materials are non-biodegradable.The environmental pollution caused by them usually required high-cost treatment.Use of renewable,biodegradable and abundant cellulose as raw material to construct cellulose nanofibrils based foam materials with light weight and high porosity had been considered as an alternative to solve the increasingly prominent environment and resource problems.In addition,the porous structure of cellulose nanofibrils based foam materials is beneficial to mix with other functional materials to endow them with special properties and expand their application scope in chemical industry,environmental protection,food,medicine and other fields.This subject used cellulose nanofibrils as raw material andγ-glycidoxypropyltrimethoxysilane(GPTMS)as crosslinking agent.A series of cellulose nanofibrils based composite foams were prepared by introducing gelatin,modification with dopamine and in situ growth by MOF(ZIF-8),and their applications in removing pollutants were studied.The Fourier transform infrared spectroscopy,FTIR)X-ray diffraction(XRD),Field emission scanning electron microscopy,FESEM)Thermogravimetric analyzer(TGA),contact angle tester,universal mechanical testing machine and other apparatus were used to characterize the prepared cellulose nanofibrils based composite foams.The research work is as follows:1.The gelatin/cellulose nanofibrils composite foams(CGMA)were obtained via freeze-drying by adding gelatin into cellulose nanofibrils suspension and using GPTMS as the crosslinking agent.It was found that the composite foam CGMA30/1 with a small amount of gelatin showed the best mechanical properties,the compressive stress of which was five times higher than that of pure cellulose nanofibrils foam(CA).In addition,the CGMA 30/1 can be stably present in the water.Moreover,the amount of gelatin had a significant effect on the pore size of the composite foams.With the decrease of gelatin content,the pore size of the composite foams decreased gradually.The CGMA 30/1exhibited good adsorption performance toward methylene blue(MB)with a maximum value of 430.33 mg/g.After four recycles within the hydrochloric acid solution,the adsorption efficiency of CGMA 30/1 still remained more than 84% of the original foam,demonstrating the good regeneration property of CGMA 30/1.2.The polydopamine/cellulose nanofibrils composite foams(PDA/CA)were prepared by immersing the GPTMS crosslinked cellulose nanofibrils foams into the ethanol/water solution of dopamine.A serious of PDA/CA can be obtained by changing the time of dopamine polymerization.The results showed that PDA/CA were stable in water due to the physical modification of polydopamine and chemical cross-linking of GPTMS.The compressive stress can reach up to496.2KPa.In addition,the coating of polydopamine can endow the PDA/CA with underwater hydrophobic characteristics.The underwater oil contact angle of PDA/CA was 147.8° toward petroleum ether.The separation effi ciency of various oil/water mixture can reach up to above97%.3.Base on the preparation of the above PDA/CA,ZIF-8 was in situ growth on the surface to increase their surface roughness to further improve the underwater hydrophobicity and mechanical properties of PDA/CA,the resulting composite foams(ZIF-8/PDA/CA)had potential application in oil/water separation.The experimental results showed that the introduction of ZIF-8 can tune the nano-microstructure of ZIF-8/PDA/CA to endow them with excellent separation ability toward mixtures of variety oil and water.The underwater oil contact angle of ZIF-8/PDA/CA was larger than 150° toward different kinds of oil,and the separation effi ciency of various oil/water mixture can reach up to above99%.In summary,this subject successfully prepared a series of cellulose nanofibrils porous composite foams by simple methods,which showed good dye adsorption and oil-water separation properties.As a result,the prepared cellulose nanofibrils composite foams have a potential application in the removal of environmental pollutants.