Adsorption Characterisation Of Low Concentration Of VOCs Onto Hypercrosslinked Polymers By Inverse Gas Chromatography

Low concentrations of VOCs are widely present in the environment; exposure in such an environment is harmful to human beings. Hypercrosslinked polymers are a novel polymeric adsorbent with high performance for medium and high-concentration VOCs adsorption. But for adsorption of low concentration VOCs, few researches has been reported. Using traditional technology is time-consuming in low concentration adsorption research. Inverse gas chromatography (IGC) is a new approach for material study, with advancement in saving time and accuracy. In this paper, IGC was used to characterize the surface properties of four different hypercrosslinked resins, and adsorption characteristics for low concentration VOCs. N-alkanes, ethyl acetate, acetone, chloroform, dichloromethane, benzene and 1,2-dichloroethane were selected as probe solutes. The main contents and results are as follows:(1)Using VBC(Vinylbenzyl chloride) as the monomer, divinylbenzene as the cross-linking agent, two hypercrosslinked polymers were prepared through polymerization and post-crosslinking step, in which two kind of solvents (1,2-dichloroethane and nitrobenzene) were used. Another two hypercrosslinked polymers were prepared under traditional way, using 1,2-dichloroethane and nitrobenzene as post-crosslinking solvents. The results showed that all the four polymers had high specific areas. The resins synthesized with nitrobenzene as solvent had more functional groups.(2) N-pentane, n-hexane, n-heptane, n-octane, ethyl acetate, acetone and chloroform were selected as probes to determine the retention volume in four polymers by IGC at infinite dilution concentration. Dispersive surface energy (74～105 mJ/m2), specific free energy (3.3～6.4 kJ/mol), adsorption enthalpy (37～62 kJ/mol) and acid-base parameters were determined. The results showed that the resins synthesized with nitrobenzene as solvent performed higher acid-base interactions and dispersive interactions with probes than the resins synthesized with 1,2-dichloroethane as solvent.(3)Isotherms were determined by IGC at finite dilution concentration with n-pentane, n-hexane, benzene, acetone, dichloromethane, chloroform and 1, 2-dichloroethane as probes. The tests were carried out at 403K,423K and 443K, respectively. The experimental dada were found to fit well by Langmuir (R2>0.987), Freundlich (R2>0.998) and Dubinin-Astakov equations (R2>0.9996). Energy distribution functions were calculated by fitting results. With the acid-base interactions, four resins performed different energy distribution. LSER was analyzed with multiple linear regression, the results showed that dispersive interaction is predominant in adsorption. Hydrogen-bond donor acidity and Hydrogen-bond basicity made different degree of contribution.