Preparation and pollutant adsorption of cyclodextrin-crosslinked polymer adsorbent
[Objective]Rapid economic and industrial development has produced a large amount of industrial wastewater,and organic dyes and heavy metal ions seriously threaten the environment and human health.Adsorption is a widely used method for treating dyes and heavy metals in water,but the currently used adsorbents commonly have problems,such as a single function and limited adsorption capacity.In addition,dyes and heavy metals generally coexist in wastewater,and both vie for the same adsorption sites and inhibit adsorption effects.The presently reported adsorbents for wastewater purification usually have limited adsorption capacity toward a single type of pollutant.Few can simultaneously remove multiple types of pollutants from contaminated water with high efficiency.[Methods]Therefore,in this paper,an easily made,efficient adsorbent for simultaneously removing dyes and heavy metals is prepared by the simple one-pot nucleophilic substitution of β-cyclodextrin(β-CD)and 4-amino-2,3,5,6-tetrafluoropyridine(ATFP).β-CD is a cyclic oligosaccharide created by the biotransformation of starch under the action of cyclodextrin transferase.β-CD comprises seven D-glucopyranoses linked by α-(1,4)glycosidic bonds,and its hydrophobic cavity can bind many hydrophobic organics through host-guest interactions,while the numerous hydroxyl groups in its cross-section can be used to bind metal ions through functional group modification,providing diverse adsorption sites for dyes and heavy metals to prevent competitive adsorption.Porous adsorbents derived by cross-linking β-CD with rigid aromatic ring-containing molecules such as tetrafluoroterephthalonitrile and decafluorobiphenyl have the advantages of a high specific surface area,easy synthesis,and fast adsorption rate and have been broadly utilized for the rapid removal of a wide range of organic micropollutants from water.[Results]The generated crosslinked polymer PCD-ATFP possesses a superior porous network structure,which is confirmed by CO2 adsorption-desorption and scanning electron microscopy analysis.RB and Cd(Ⅱ)adsorption by PCD-ATFP reaches adsorption equilibrium in only 45 and 60 min,respectively.The maximum adsorption amounts of RB and Cd(Ⅱ)are 173.2 and 64.2 mg·g-1,respectively.The adsorption follows the Langmuir isothermal model.For the RB-Cd(Ⅱ)mixed solution,PCD-ATFP demonstrates an ideal simultaneous adsorption effect with no mutual adsorption inhibition of dyes and heavy metals.Finally,the adsorption mechanism is verified by X-ray photoelectron spectroscopy.[Conclusions]Generally,natural polysaccharide β-CD is used as the raw material to make adsorbents for the simultaneous adsorption of dyes and heavy metals from wastewater.The raw materials are green and environmentally friendly,the preparation is mild,and the characterization methods are simple and universal.The experiment proposes high requirements on students'research and exploration ability while training their basic knowledge application ability,which is fitting for the comprehensive experimental courses of senior undergraduates in chemistry,materials,and other related majors.This experiment"introduces research into teaching,"requiring students to master the preparation of β-CD cross-linked polymers by nucleophilic substitution,to comprehend the characterization methods and basic principles of polymer chemical structure and microscopic features,and to learn the experimental operation methods and data processing and examination of the adsorption of dyes and heavy metals.This approach will enable students to apply their knowledge of the subject comprehensively,think and study diligently,utilize subject knowledge comprehensively,develop a creative sense of thinking,and research diligently.
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