Study On Graft Modification Of Sulfonic Polystyrene Resin And Its Adsorption Behavior And Catalytic Performance

Sulfonic polystyrene-divinylbenzene cation exchange resin has the structure of crosslinking matrix copolymerized by styrene and divinyl benzene with sulfonic groups(-SO3H).Its acidity is equivalent to inorganic acids such as HCl,H2SO4,and H3PO4.It can be used in the treatments of wastewater containing metal ions,water softening,and biological pharmacy separation and purification,etc.due to its ion exchange property;and it can also be used as a solid acid catalyst for chemical reactions with its acidity.In this study,the research was carried out from three aspects-the ion exchange property of 732 strong acidic sulfonic polystyrene cation exchange resin(732-CR);the adsorption property of hexamethylene diamine modified resin(HDMR),and the catalytic performance of 732-CR in ketalization.The main contents include:732-CR was used for the removal of divalent metal ions(Pb2+,Cu2+,Ni2+ and Mg2+)from aqueous solutions.The effects of various parameters such as contact time,initial pH,initial metal ion concentration(C0),resin amount and temperature were investigated.The ion exchange kinetics and thermodynamics were measured,and the mechanism was studied at the temperature range of 298-328 K.The results show that the ion-exchange processes are favored under particle diffusion control mechanism when C0? 20 mmol·L-1.Otherwise,film diffusion control phenomenon is more prominent below 20 mmol·L-1.Ion exchange kinetic data were treated by the Nernst-Planck equation and the Unreacted-core model.The values and relationships of diffusion coefficients of counter ions(DM and DH)within the resin and the efficient diffusion coefficient(De)were calculated and discussed.The ion-exchange isotherm analysis shows a well fit with the Langmuir model,proving the homogeneity of resin surface and a monolayer chemical sorption mechanism.The maximum monolayer exchange capacities(qm)were found to be 2.336 for Pb2+,1.736 for Cu2+,2.876 for Ni2+,and 1.577 mmol·g-1 for Mg2+ at 308 K,respectively.And these values were verified by the Energy Disperse Spectroscopy(EDS)analysis.The hydrated structure was discussed to explain the difference in qm.The results show a two-shell six-coordinated-hydrate with eight water molecules for Cu2+([Cu(H2O)8]2+)and a octahedral six-coordinated-hydrate with six water molecules for Ni2+([Ni(H2O)6]2+)are the effective components for ion exchange.The regeneration property of 732-CR was studied and the ion exchange capacity reduced to 60%?70%of fresh resin after four cycles.Hexamethylene diamine modified resin(HDMR)was prepared by sequentially reacting with thionyl sulfoxide and hexamethylene diamine,using 732-CR as raw material.The adsorption capacities of HDMR for divalent metal ions are:Ni2+>Zn2+>Co2+>Cu2+>Pb2+>Ca2+>Mg2?.The 732-CR,HDMR,and the metal complexes of HDMR(HDMR+Pb2+)were characterized by IR,SEM,EDS,and BET,confirming amino groups and metal ions are successfully anchored onto 732-CR and HDMR,respectively.And N and O atoms in HDMR are involved in the process of the adsorption of metal ions.Compared with 732-CR,the adsorption capacity of HDMR for Ni2+ increased significantly to 4.179 mmol·g-1 at 298 K and initial Ni2+ concentration of 20 mmol·L-1.The adsorption behavior of Ni2+ in aqueous solution on HDMR was investigated.The effects of various parameters such as initial pH,adsorbrnt dosage,temperature,and initial metal ion concentration were discussed.The kintic data was regressed with six kinetic models and the adsorption mechanism was studied.The results show that the adsorption process of Ni2+ on HDMR is chemical adsorption,including ion exchange and chelation.The adsorption activation energy is 44.7 kJ-mol-1.The whole adsorption process consists of three stages:the first stage is controlled by film diffusion,the second stage is controlled by intra-particle diffusion,and the third stage reaches the equilibrium.The adsorption isotherm shows that the Frenchlich model can well describe the adsorption process,indicating the multilayer sorption mechanism.That is,the graft of hexamethylamine on 732-CR results in the change of the mechanism of metal ion adsorption.The regeneration and recovery of HDMR show that 82.3%adsorption could be achieved up to fourth generation cycle,demonstrating a good performance of recycling.A seven-membered ring ketal—7,12-Dioxaspiro[5.6]dodecane(DOSD)was synthesized through the ketalization reaction of cyclohexanone with 1,4-butanediol(BD)using 732-CR as catalyst.The influences of various experimental parameters like agitation speed,initial molar ratio of reactants,temperature,catalyst loading and particle size on the conversion of limiting reactant BD were studied.The non-ideal reaction system was calculated by the UNIFAC group contribution method.The thermodynamics and kinetics of ketalation were also studied.The reaction equilibrium constant(Ke)was determined experimentally in the temperature range 293.15-333.15 K.The standard molar reaction thermodynamics properties(?H0,?S0,and ?G0)were obtained at 298 K.Different kinetic models like pseudohomogeneous,Eley Rideal,Langmuir Hinshelwood were tested against experimental data,and Eley-Rideal mechanism based on the chemisorption of BD predict the kinetics best.