Preparation And Adsorptive Property Of Phenol Hydroxyl Hypercrosslinked And Molecularly Imprinted Adsorption Resin

The hypercrosslinked resin compared with the traditional macroporous adsorption resin, the hypercrosslinked resin has high mechanical strength, significant specificity adsorption, high absorption capacity and wide functionallization range to get more and more research attention. At present, hypercrosslinked adsorption resins are widely used in sewage treatment, extraction process of traditional Chinese medicine composition, hemodialysis, analytical chemistry, petrochemical and other fields. In recent years, the great our achievements of development and application of polymer adsorption resin in organic wastewater treatment have been obtained in China, especially for extracting carcinogenic organic matters in wastewater. The desorption process is difficult when the adsorption of polymer resin is conducted with covalent bonding, while the specificity adsorption is not strong for hydrogen bonding. To improve the adsorption specificity and adsorption capacity of hypercrosslinked adsorption resin, based on the hypercrosslinked hydrogen adsorption and molecular imprinting technique, a novel polymer adsorption resin was prepared for adsorbing organic pollutant of aniline.The lower crosslinked styrene-divinyl benzene polymer(St-DVB) was prepared by suspension polymerization method. Using self-made 1,4-dichloro methoxy butane as chloromethylation reagent, the hypercrosslinked molecularly imprinted adsorption resin modified by phenol in post-crosslinking reaction(PHMI) was prepared with cyclohexylamine as imprinting template. The non-molecularly imprinted hypercrosslinking adsorption resin(LM-5) was also prepared.The prepared adsorption resins were characterized by specific surface area and pore size tester(BET), fourier infrared spectrometer(FT-IR) and scanning electron microscope(SEM). The adsorption properties and the adsorption selectivity of aniline onto PHMI adsorption resin were investigated in water system and non-water system of benzene and aniline mixed solution. The effects of temperature, concentration and pH on the adsorption performance were investigated, especially on the hydrogen bonds formed between adsorbent and adsorbate. The adsorption thermodynamics and the adsorption dynamics behavior of PHMI adsorption resin were systematically investigated in water system. The comprehensive adsorption properties of benzene and aniline onto PHMI and LM-5 resin were compared in water system.The specific surface area of PHMI resin is 678.3m2/g with pore capacity of 0.577cm3/g. For the initial concentration of 800 mg/g in water system, the equilibrium adsorption capacities of benzene and aniline onto PHMI resin are 62.240 mg/g and 118.485mg/g at 298 k, respectively. For different initial concentrations, the equilibrium adsorption capacitis of aniline are greater than those of benzene due to the hydrogen bonding formed between aniline and PHMI surface. Because the adsorption processes of benzene and aniline are exothermic, the adsorption capacities of benzene and aniline are reduced with the increasing of temperature. The selectivity coefficient of aniline onto PHMI is greater than 1.5 at 298 k in neutral solution, which illuminates selective adsorption. The adsorption thermodynamics results show that the adsorption of benzene onto PHMI fits Freundlich model, and the adsorption of aniline fits both Freundlich model and Langmuir model. The adsorption of aniline is pushed by both physical adsorption and chemical adsorption, while the adsorption of benzene is only pushed by physical adsorption. Based on Lagergren and Kannan-Sundaram dynamics model analysis, the adsorption rates of benzene and aniline are controlled by liquid film diffusion and particle diffusion. The adsorption rate constant of benzene and aniline onto PHMI out of particles are 0.0164 min-1 and 0.0128 min-1, respectively, while the adsorption rate constant in granules are respective 5.491 mg·min-1/2·g-1 and 9.620 mg·min-1/2·g-1. The pH value has great influence on adsorption process, especially for the adsorption of aniline. In strong acid and strong alkali solutions, the selective adsorptions of aniline onto PHMI are lost. The desorption times of benzene and aniline on PHMI are about 8 h and 12 h with resolving rates of 99.72% and 91.20%, respectively.The adsorption capacities onto PHMI and LM-5 in mixed water system were compared. For the initial concentration of 800 mg/g at 298 k, the equilibrium adsorption capacity of aniline onto PHMI is 36.975 mg/g bigger than that onto LM-5, and the equilibrium adsorption capacity of benzene is 16.284 mg/g bigger than that onto LM-5. The equilibrium adsorption capacity of 2-naphthol onto PHMI is 3.494 mg/g bigger than that onto LM-5. In the mixed solution, the adsorption capacity difference of 2-naphthol is slight, while the adsorption capacity of aniline onto PHMI is obviously bigger than that onto LM-5. The adsorption results show that the hydrogen bonding is formed between PHMI and aniline, and molecularly imprinted technology can improve the adsorption performance to achieve strong adsorption specificity. For different pH values, the adsorption change trends of aniline and 2-naphthol onto PHMI and LM-5 are similar. The desorption efficiency of aniline on PHMI and LM-5 are 91.20%, 93.72% with desorption times of 12 h and 9 h, respectively. The desorption efficiencies are similar, while the desorption time of aniline from PHMI is longer than that from LM-5. The molecular imprinting template hole causes the space steric hindrance to make the desorption difficult.