Preparation Of Functional β-cyclodextrin Polymers And Study On Removal Of Pollutants From Water

With the rapid development of industry and the improvement of residents’ living standards,as well as the rise of the service industry in cities,the discharged industrial wastewater and urban sewage have caused important damage to the ecological environment and a serious threat to human health,especially the pollution of heavy metals and organic matter.How to quickly and efficiently remove contaminants from water is a very important topic.At present,the advantages of the adsorption method,such as rapid removal,simple operation,low energy consumption,and reusability,have attracted the attention of many researchers.β-cyclodextrin(βCD)is a kind of cyclic oligosaccharide that is easy to obtain,low cost,non-toxic,does not cause secondary pollution,and can produce a host-guest form of encapsulation for organic matter,especially non-polar organic matter.In this thesis,using β-cyclodextrin as matrix,polyethyleneimine(PEI)and 5,5’,6,6’-tetrahydroxy-3,3,3’,3’-tetramethyl-1,1’-spirobisindane were selected as crosslinking objects.Three kinds of high-efficiency adsorbents were synthesized from different crosslinking agents to remove Pb(II),hydroquinone(HQ),and endocrine disruptors such as BPA and BPS.The chemical composition,surface morphology,and physical-chemical properties of β-cyclodextrin crosslinked polymer were characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),nitrogen adsorption isotherm(BET),thermogravimetric analyzer(TGA),X-ray photoelectron spectroscopy(XPS)and Zeta potential analysis.Moreover,the influence of various factors on the target adsorbate adsorption onβ-cyclodextrin polymer was studied,and the main conclusions were as follows:1.Using melamine chloride as the crosslinking agent,β-cyclodextrin and polyethyleneimine as cross-linking objects,the adsorbent(CD@PEI)was successfully prepared by a two-step synthesis method to remove lead and hydroquinone(HQ)from water.First,β-cyclodextrin and cyanuric chloride pre-react under low-temperature conditions,and then add polyethyleneimine completes the cross-linking reaction at high temperature to synthesize β-cyclodextrin and PEI polymer adsorbent(CD@PEI)for the removal of Pb(II)and HQ from water.The results of adsorption kinetics reveal that Pb(II)and HQ adsorption onto CD@PEI are better fitted by the pseudo-second-order kinetic model.The maximum adsorption capacity of Pb(II)and HQ on CD@PEI can reach 113.52 mg/g and 364.86 mg/g,respectively.The Langmuir model is in good agreement with the experimental results,indicating that the adsorption of Pb(II)and HQ on CD@PEI is monolayer;Thermodynamic studies show that the adsorption process of HQ and Pb(II)on CD@PEI is spontaneous and exothermic.CD@PEI has good recycling performance for Pb(II)and HQ.After five cycles,the adsorption performance of HQ decreased by 5.14%,and Pb(II)was only 12.57%;CD@PEI adsorbed Pb(II)and HQ.The mechanisms mainly include chelation of nitrogen-containing functional groups,electrostatic interactions,and host-guest inclusion and interaction.2.Using hexamethylene diisocyanate as the cross-linking agent,β-cyclodextrin and 5,5’,6,6’-tetrahydroxy-3,3,3’,3’-tetramethyl-1,1’-spirobisindane as the cross-linking objects,a novelβ-cyclodextrin polymer adsorbent(CD@TTSBI)was synthesized in DMF solution by solvothermal method for removal of Bisphenol A(BPA)and Bisphenol S(BPS)from aqueous solutions.The CD@TTSBI polymer exhibited excellent three-dimensional network structure and thermal stability.Both BPA and BPS reached the adsorption equilibrium at 1.5 min,and achieved adsorption rates of 99.42% and 99.11%,respectively;Among them,the maximum adsorption capacity of BPA and BPS reached 353.68 mg/g and 397.45 mg/g,respectively;Thermodynamic studies showed that the adsorption of both on CD@TTSBI belonged to the spontaneous process of exothermic entropy increase;methanol was used as the desorption solvent after five The adsorption capacity losses of BPA and BPS on CD@TTSBI after the second cycle were 1.05%and 2.6%,respectively.The main mechanism of the adsorption process is the wrapping effect of the cyclodextrin cavity,the trapping effect of the three-dimensional network pore structure of the material,and the effect of the hydrogen bond.3.Using epichlorohydrin as a cross-linking agent,p-toluenesulfonyl chloride modifiedβ-cyclodextrin and polyethyleneimine as cross-linking objects,a β-cyclodextrin polymer adsorbent(Tosyl CD@PEI)was synthesized for the removal of hydroquinone from water.Adsorption kinetics experiments showed that HQ reached the adsorption equilibrium at 180 min and fitted well with the pseudo-second-order model;The maximum adsorption capacity of HQ was 77.54 mg/g and fit well with the Langmuir model;The adsorption process of HQ on Tosyl CD@PEI is in a spontaneous exothermic process and adsorption capacity of HQ was less affected by temperature;The adsorption capacity of HQ is only reduced by 8% after repeated for five times;the main mechanism of adsorption is electrostatic interaction and the host-guest encapsulation effect of the cavity.