Preparation Of Cellulose Nanocrystal Aerogels By Hydrothermal Method And Their Adsorption Properties

Cellulose nanocrvstals(CNCs)are a naturally derived renewable resource,which have good strength,flexibility and has become a research hotspot in the field of nano biotechnology due to its large amount,reproducible,non-toxic and biodegradable properties.Today,developments in industry and commerce have raised the problem of dye contamination and heavy metal ions contamination,in particular that associated with Pb2+,Cd2+,and Cu2+pose a considerable threat to aquatic environments and human health.Quantum dots(QDs)are new fluorescent nanomaterials with unique and excellent fluorescence properties.CNC-g-AA hydro/aerogels synthesized by a free radical graft copolymerization of acrylic acid(AA)and CNCs followed by hydrothermal strategy and freeze drying methods.The obtained CNC-g-AA hydrogels showed good elastic properties and reciprocating compression ability.The CNC-g-AA hydrogels withstood up to 0.821 MPa of compression and showed good reciprocating performance when the deformation reached 40%.The swelling performance of the CNC-g-AA aerogels was related to the hydrothermal treatment temperature and duration.The swelling capacity of the CNC-g-AA aerogels was also affected by the volume of added AA and the mass fraction of the CNCs.The swelling ratio of the CNC-g-AA aerogels was as high as 495:1 when the CNC content was as low as 0.15 wt%.This high swelling ratio is considerably greater than those of other polysaccharide-g-AA aerogels systems.In this work,we applied CNC-g-AA aerogel as an adsorbent for MB,Pb2+,Cd2+,and Cu2+removal.The morphology,surface functional groups,electronegativity,and adsorption properties of the CNC-g-AA aerogels were investigated in detail.The as-formed CNC-g-AA aerogels had highly porous honeycomb structure,with many functional groups and a high zeta potential,all of which are essential features for an effective adsorbent.The characterization of the MB adsorption behavior showed that the MB adsorption kinetics and isotherm were well-fitted by a pseudo-second-order model and the Langmuir isotherm model,respectively.The kinetic data also agreed well with the Elovich model.The maximum MB removal capacities of CNC-g-AA aerogels reached 400 mg/g.CNC-g-AA aerogel as an adsorbent for Pb2+,Cd2+,and Cu2+ removal.Their adsorption followed the Freundlich isotherm model and fitted well with pseudo-second-order kinetics models even agreed well with the Elovich model.The heavy metal ions adsorbed by CNC-g-AA aerogels mainly through electrostatic chelation with sulfonate and carboxylate groups.The maximum Pb2+,Cd2+.and Cu2+removal capacities of CNC-g-AA aerogels reached 1026,898.8,and 872.4 mg/g respectively.CNC-g-AA/CdSe/ZnS quantum dots gels were prepared by free graft copolymerization and hydrothermal treatment.During this hydrothermal process CNCs as raw materials and water-soluble CdSe/ZnS quantum dots as precursor,via the interaction of AA and MBA,CdSe/ZnS quantum dots will be fixed in the porous CNC-g-AA gel structure.The fluorescence spectra showed that the fluorescence properties of CdSe/ZnS did not change obviously during the transformation,indicating that the CdSe/ZnS quantum dots had been doped into the CNCs gel structure.CNC-g-AA/CdSe/ZnS quantum dot gel can show four different colors of red,yellow,blue and green,which showed good detection performance of Pb2+.