Synthesis And Adsorption Properties Of Selective Resin For P-Hydroxybenzoic Acid

In the present study,a selective anion exchange resin MIP is prepared via the reaction of chloromethylated PS-DVB copolymer beads with 4-hydroxybenzoic acid(4-HB)used as template molecule,ethylene glycol dimethacrylate(EGDMA)as the cross-linker,diethylaminoethyl methacrylate(PDEAEMA)as functional group by the technique of atom transfer radical polymerization(ATRP).And the optimum reaction conditions are determined by optimizing the ratio of synthetic raw materials and the synthesis conditions.The structural and surface parameters of the resins are characterized by Fourier transform infrared spectroscopy,specific surface analysis and X-ray photoelectron spectroscopy.Phenol,benzoic acid,3-hydroxybenzoic acid,2-hydroxybenzoic acid and 2-hydroxynaphthalene are selected as interfering substances in order to study the selective adsorption of two resins.The results show that the adsorption capacity of MIP is higher than NIP with the interfering substances,and the MIP has good selectivity for the adsorption of 4-HB in the two-substance system than NIP.Disruptors such as Phenol,benzoic acid,3-hydroxybenzoic acid,2-hydroxybenzoic acid and 2-hydroxynaphthalene were selected as interfering substances in the binary.The relative selection of adsorption coefficient are 5.734,4.492,3.131,3.095 and 11.696 respectively,indicating that the selectivity of MIP is better than NIP.The adsorption properties of both resins are studied.The results show that the adsorption capacity for 4-HB is highest when the solution pH value is 3.5 and for phenol is highest when the solution pH value is 6.5.Langmuir isotherm model and Koble-Corrigan isotherm model can well describe the adsorption process of 4-HB and phenol on both the studied resins,indicating adsorption process is monolayer adsorption and binding sites are uniform distributed.The lower temperature is advantageous to the adsorption process.The adsorption capacities of MIP and NIP for 4-HB are 1.88mmol/g and 1.65mmol/g,and for phenol are 1.38mmol/g and 1.25mmol/g when the temperature is 303 K.The adsorption mechanism mainly contains hydrogen bonding,electrostatic interactions and ?-? interactions.The analysis on the adsorbent thermodynamics of both resins demonstrates that adsorption processes are spontaneous under experimental conditions.The pseudo second order kinetics model can well describe the adsorption kinetics of 4-HB and phenol on the resins.And the adsorption processes of adsorbates on both resins are controlled mainly by liquid film diffusion and intra-particle diffusion secondly.The sulfate ions and chloride ions contained in solutions have less negative effect on the adsorption properties of MIP than NIP.Both resins have good dynamic adsorption performance.Yoon-Nelson and Thomas model can simulate the adsorption breakthrough curves of 4-HB well.The penetration time of MIP and NIP for 4-HB are 16 h and 9 h respectively,indicating that the processing capacity of MIP is 1.77 times of NIP.And MIP has good selectivity for the adsorption of 4-HB than NIP.The resins can be reused effectively by using NaOH solution as desorption agent.