Preparation Of Regenerated Cellulose Based Composite Aerogel And Its Adsorption Of Heavy Metals

Water resource is an important natural resource for human survival and development.Therefore,in view of the current serious water pollution problem,how to purify and recycle wastewater has become the focus of people’s attention.This topic for heavy metal pollution,sources,low cost,biodegradable microcrystalline cellulose(MCC)and chitosan(CS),organic biomass materials as two elements combined with high cation exchange capacity of montmorillonite(MMT),inorganic materials,the design and preparation of the high adsorption,high strength and renewable composite aerogel materials.Firstly,NaOH/urea was applied to break the hydrogen bonds between MCC macromolecular chains,and then the hydrogen bonds between cellulose were regenerated to construct regenerated cellulose(RC)aerogel.Then,MMT particles were introduced into RC aerogel forming process,and a three-dimensional porous network structure of regenerated cellulose/montmorillonite(RC/MMT)composite aerogel with excellent compression and adsorption capacity was prepared by hydrogen bonding between MMT lamellar and hydroxyl group in cellulose.The maximum compressive strength of the aerogel is 251.8 kPa,and the saturated adsorption capacity of Pb2+,Cd2+,Co2+and Cu2+reaches 152.2 mg/g,100.2 mg/g,84.1 mg/g and 30.6 mg/g,respectively.The results of regeneration cycle adsorption experiments show that the saturated adsorption capacity of RC/MMT composite aerogels for heavy metal ions remains above 70%of the original value after five sorption-desorption cycles.In order to improve the low porosity of RC/MMT aerogel and increase the free diffusion channels of heavy metal ions in the adsorption process,CS solution dissolved in acetic acid was rapidly mixed with RC/MMT sol,and gradually crosslinked by hydrogen bonding between the three.A highly efficient and well-structured regenerated cellulose/montmorillonite/chitosan(RC/MMT/CS)composite aerogel was constructed after freeze drying.The aerogel has a maximum compressive strength of 279.0 kPa,1.23 times that of RC/MMT aerogel.The results of adsorption experiments showed that the saturated adsorption capacities of RC/MMT/CS composite aerogel for Pb2+,Cd2+,Co2+ and Cu2+were 221.6 mg/g,153.1 mg/g,134.5 mg/g and 67.2 mg/g,respectively.It is 1.46,1.53,1.60 and 2.20 times of RC/MMT aerogel in the same adsorption environment.The adsorption process accords with quasi-second-order adsorption kinetic curve and Langmuir adsorption isotherm model.The adsorption mechanism of RC/MMT/CS composite aerogel shows that the adsorption capacity of RC/MMT/CS composite aerogel is derived from physical and chemical double adsorption.The regeneration results of RC/MMT/CS composite aerogel show that the saturated adsorption capacity of the composite aerogel for heavy metal ions is more than 75%of the original value after 5 cycles of adsorption-desorption,which proves that RC/MMT/CS composite aerogel can be used as a recyclable adsorption material.