Synthesis, Characterization And Adsorption Studies Of Branched Poly(Ethyleneimine)s Chelating Resins

The recent research progress of Poly(ethyleneimine) chelating resins and their application of chelate adsorption was introduced in this paper, based on these reseaches, three kinds of PEI-based chelating resins containing 4-hydroxy-4'-methoxybiphenyl as mesogenic groups with different spacer length methylene units were synthesized, and different reaction conditions on the substitution degree of polymer was also studied. IR and 1H NMR were used to characterize the different structure, the branching degree of the mesogenic side groups were also calculated from 1H NMR. DSC analyses show that Glass transition temperature of the product increases with the substitution degree of mesogenic groups and the grafting yield reaches a certain value can present as liquid crystal, and confirmed by POM. WXRD characterize the structure of the polymer:three kinds of polymers have crystallinity and their crystal structures were similar; with the grafting rate of increase, the better the crystalline polymer; rigid mesogenic side chains help to improve product order degree.A series of conventional adsorption properties of chelating resins have been investigated. Their results showed that, the resins have a higher adsorption capacity for Hg(â…¡), and a medium adsorption capacity for Cu(â…¡),Pb(â…¡), but a very poor adsorption capacity for Zn(â…¡),Cd(â…¡), so they presented a excellent adsorption selectivity for abovementioned metal ions; pH values have a greater effect on adsorption properties and which have different expression forms along with different metal ions; the resin's adsorption equilibrium time to Cu(â…¡) and Hg(â…¡) both are 2h, and the adsorption process can be described with GE.Boyd liquid film diffusion equation; Effect of temperature on the adsorption is great and certain temperature is beneficial to adsorption; the adsorption isotherms of P4 for Hg(â…¡) can be described by Langmuir isotherm equation, whereas the adsorption isotherms of P4 for Pb(â…¡),Cu(â…¡) can only be described by Freundlich isotherm equation; in addition, the resins presented excellent regeneration properties with an upon 89% desorption rate after three times reuse.In order to investigate the effect of resinic orientation on adsorption performance for metal ions, we have obtained the crystalline state with lower orientation degree and the liquid crystalline state with orientational state of rigid groups by annealing and quenching thermal treatment on P4 resin prepared. The results indicated that there were some differences on adsorption capacity for a given metal of resins under different thermal states, and these differences have better regularities which have different form to every specific metal ion. So it's expected to enhance the adsorption selectivity for a given metal ion by modifying the orientation degree of resins. Additionally, the correlative mechanism of adsorption was investigated from the point of the matching degree between resinic molecular mean space and effective hydrated metal ionic radius as well as the principle of the hard and soft acids and bases (HSAB), by means of abovementioned theories, we can successfully explain the especial adsorption behavior of liquid crystalline resin which was different from that of crystalline resins.