Adsorptive Separation Of Aromatic Compounds From Aqueous Medium By Beta-cyclodextrin And Starch Based Polymers

Efficient separation of organic pollutants from chemical wastewater is an important research direction in chemical process.Natural polymer materials are widely available and cheap,functional groups are abundant and easy to modify.The design and development of materials with rich pore structure and selective functional groups provide the possibility for efficient separation of organic pollutants.In this paper,based on?-cyclodextrin(?-CD)and starch,different monomers and synthesis methods were used to design and synthesize a variety of polymers.By infrared spectroscopy,solid-state nuclear magnetic,X-ray photoelectron spectroscopy,scanning and transmission electron microscopy,N₂ adsorption-desorption characterization methods to get chemical structure,morphology and pore characteristics of polymers,the preparation process and pore size regulation rules were also grasped.To explore the process of adsorptive separation for aromatic organic pollutants and clarify the mechanism of adsorption.The main research contents of this thesis are as follows:(1)Combined with?-CD cavity molecular recognition and stronger?-?interaction of benzene ring to acetophenone(AP).Two triisocyanate crosslinked?-CD polymers were prepared using methyl ethyl ketone(MEK)and N,N-dimethyl formamide(DMF)as solvent,which named CTPM and CTPD,respectively.Polymers were used for adsorptive separation of AP and 1-phenylethanol(PE)that come from the by-product of epoxy-propane styrene(PO/SM)co-production process.The results showed that CTPM had better selective adsorption for AP than CTPD.The saturated adsorption capacity of CTPM for AP and PE was 3.55 and 2.16mmol·g^-1 in single component solutions,respectively,and the separation factor for AP reached 7.01 in the AP/PE mixture with equimolar concentration(40 mmol·L^-1).Based on the molecular simulation analysis of adsorption process,it can be inferred that the good adsorption selectivity is attributed to the synergistic effect of the core and shell structure of CTPM.The main interactions in the adsorption process include?-CD cavity host-guest inclusion,?-?interaction and hydrogen bonding.After single continuous adsorption-desorption of PO/SM by CTPM,the content of AP can increase from 77.16%to 93.80%.(2)The?-CD cavity with molecule recognition and the benzene ring of aromatic polyisocyanate can be used as the adsorptive sites for 2,4-dichlorophenol(2,4-DCP).Expand the application range of?-CD polyurethane materials,the submicron?-cyclodextrin-based polymer particles(CSPs)were prepared by triphenylmethane-4,4?,4?-triisocyanate(TTI)crosslinking?-CD and using dibutyltin dilaurate(DBTDL)as catalyst.The content of TTI in CSPs can be increased by increasing the amount of catalyst.CSPs have good adsorption performance for 2,4-DCP,the slightly acidic and neutral pH as well as inorganic ions co-existence were found to be favorable for 2,4-DCP onto CSPs.Furthermore,CSPs had specific selective adsorption for 2,4-DCP from aqueous media which containing 2-chlorophenol or phenol.The comprehensive analysis of adsorption experimental and theoretical results suggested that the?–?interaction,?-CD cavities host-guest inclusion and hydrogen bonding may jointly drive the adsorption of 2,4-DCP.(3)In view of the shortcoming of starch-based materials with low specific surface area,starch grafted styrene hypercrosslinked polymers(SSHCPs)with rich porosity and high specific surface area were prepared by Friedel-Crafts alkylation with ferric chloride(Fe Cl₃)as catalyst,starch grafted styrene(st-g-ps)as a precursor,formaldehyde dimethyl acetal(FDA),dichloroxylene(DCX)and 4,4'-bis(chloromethyl)biphenyl(BCMBP)as diplomatic agents.The effect of type of crosslinking agent on polymers structure and the adsorption separation for AP/PE were studied.The results showed that the specific surface areas of the three SSHCPs were 222,791 and 818 m²·g^-1,respectively.The specific surface area of SSHCPs increased with the increase of aromatic ring in the crosslinking agent,and the adsorption performance for AP/PE was better.SSHCP-3 was prepared with BCMBP as crosslinker can adsorb 93.6%of AP and 74.4%of PE in PO/SM effluent,which indicating the application prospect of SSHCP-3 for adsorption treatment of wastewater containing AP and PE.The saturated adsorption capacity of SSHCP-3 for AP and PE was 4.50 and3.21 mmol·g^-1,respectively,which was higher than that of CTPM.Spectroscopic studies and theoretical calculations show that the adsorption process of AP and PE is driven by van der Waals forces,hydrogen bonding with glucose unit and?-?interaction with aromatic ring.(4)Combined with the high adsorption capacity of SSHCPs for aromatic compounds and the high selectivity of CTPM.?-CD modified by p-tolyl isocyanate(CD-PTI-3)was loaded into st-g-ps by Friedel-Crafts alkylation reaction to obtain?-CD modified starch grafted styrene porous polymer(CD-SSHCPs).The effects of crosslinker type on structure and the adsorption properties of CD-SSHCPs for aromatic compounds were studied.The results showed that DCX and BCMBP were easier to fix CD-PTI-3 onto st-g-ps than FDA.The specific surface areas of the polymers prepared by FDA,DCX and BCMBP as crosslinkers were 139,280 and538 m²·g^-1,respectively.The adsorption of CD-SSHCP-3(prepared by BCMBP)for phenolic organic compounds was investigated.It was found that the electron-withdrawing groups can reduce the?electron density of benzene ring,reducing the?-?repulsion between substrate and adsorbent,which improving the?-?interaction and enhancing the adsorption.(5)For CD-PTI-3 modified starch-based porous polymers,crosslinkers must be needed to load CD-PTI-3 into the polymers.A simpler preparation technology of non-crosslinking agent was proposed.First,starch grafting vinylbenzyl chloride polymer(st-VBC)was prepared by emulsion polymerization,and then CD-PTI-3 was loaded onto st-VBC by electrophilic substitution reaction between chloromethyl and benzene ring to obtain porous polymer(stVBC-CD).The effects of addition amount of CD-PTI-3 on adsorptive properties and morphology of stVBC-CD were investigated.The higher addition amount of CD-PTI-3(the molar ration of st-VBC),the smaller the specific surface area of stVBC-CD.The specific surface areas of stVBC-CD-0.5,stVBC-CD-1.0 and stVBC-CD-1.5 were733,574 and 462 m²·g^-1,respectively.The saturated adsorption capacity of stVBC-CD-1.0 for 2,4-DCP can reach 874 mg·g^-1.