Study On The Preparation And Adsorption Characteristics Of Cucurbit[6]Uril-based Polysaccharides

The chemical contamination of water from a wide range of toxic derivatives,in particular heavy metals,aromatic molecules and dyes,is a serious environmental problem owing to their potential human toxicity.Therefore,there is a need to develop technologies that can remove toxic pollutants found in wastewaters.Among all the treatments proposed,adsorption is one of the more popular methods for the removal of pollutants from the wastewater.Adsorption is a procedure of choice for treating industrial effluents,and a useful tool for protecting the environment.In particular,adsorption on natural polymers and their derivatives are known to remove pollutants from water.The increasing number of publications on adsorption of toxic compounds by modified polysaccharides shows that there is a recent increasing interest in the synthesis of new low-cost adsorbents used in wastewater treatment.In this paper,cucurbit[6]uril(CB[6])was used to construct the CB[6]-based chitosan adsorbent and CB[6]cross-linked alginate adsorbent.The properties of CB[6]-based adsorbent was also studied.An apparent advantage of CB[6]-based adsorbent polysaccharides is the appearance of CB[6]cavity on the polysaccharides backbone,which can enhance adsorption by supramolecular interaction.(1)Three cucurbit[6]uril grafted chitosan with different CB[6]content(CB[6]-CS-1,CB[6]-CS-2,CB[6]-CS-3)were prepared.The composition of CB[6]-CS absorbents were characterized by FT-IR.The CB[6]-CS was further used to absorb acid chrome blue and azocarmine B.The content of CB[6]in CB[6]-CS played an important role for the adsorption of acid chrome blue and azocarmine B.The adsorption capacity increased with increasing CB[6]content for CB[6]-CS.Meanwhile,the acid chrome blue and azocarmine B adsorption was highly dependent on initial concentration of azo dyes,temperature and initial solution pH value.Adsorption isotherm and adsorption kinetics was studied in this paper.The excellent acid chrome blue and azocarmine B adsorption capacities and relatively low cost made the CB[6]-CS very useful for applications in wastewater treatment.(2)We report the preparation of hydrogels from CB[6]cross-linked alginate and covalently cross-linked polyacrylamide interpenetrating polymer networks(CB[6]-IPN).The composition,microstructure,and morphology of CB[6]-IPN hydrogel beads were characterized by Fourier transform-infrared spectroscopy,solid-state proton nuclear magnetic spectroscopy,thermogravimetric analysis,and scanning electron spectroscopy.The CB[6]-IPN gel demonstrated irregular pore shapes and a relatively open three-dimensional network structure.With the porosity produced from the separated CB[6]structures and the exceptional binding affinity to the CB[6]outer surface,CB[6]-IPN could be an effective adsorbent for azocarmine B removal from contaminated water bodies.Studies on adsorption isotherm and adsorption kinetics showed that azocarmine B adsorption on the CB[6]-IPN gel fitted the Freundlich isotherm model and the pseudo-second-order kinetics,respectively.Furthermore,the effects of solution pH,temperature,adsorption time,and CB[6]content in CB[6]-IPN were investigated.Adsorption capacity increased with increasing CB[6]content in CB[6]-IPN and pH of azocarmine B.This work presented methods for preparation of CB[6]-functionalized interpenetrating polymer,which showed potential as an efficient adsorbent for specific large-sized dyes.