Study On Branched Poly(Ethylene Imine)-Modified Cellulose-graft-polymer

Water pollution caused by heavy metals has become one of the most serious environmental issues worldwide. Adsorption is an efficient and renewable technology without secondary pollution. Thus, removal of heavy metals from industrial effluent by adsorption with adsorbent attracted much attention. Meanwhile, with enhanced understanding of sustainable utilization of energy and the improvement of environmental awareness, eco-friendly natural material has become an ideal choice in the synthesis of adsorbents for heavy metals.Branched polyethylene imine (BPEI), is a typical water-soluble polyamine with hypotoxicity, which possesses strong chelating ability for heavy metal ions. This study focuses on an improved synthesis of a branched poly (ethylene imine)(PEI)-modified cellulose-based adsorbent (Cell-g-PGMA-PEI). We aim to improve the adsorbent capacity by reducing side reaction of epoxide ring opening during graft copolymerization of glycidyl methacrylate (GMA) onto cellulose so as to increase the content of epoxy groups, anchors to immobilize branched PEI moieties.We put forward to an optimum synthesis condition by determination graft percentage (Gp), graft efficiency (GE) and content of epoxy groups. FT-IR spectra, elemental analysis and TG/DTG analysis provided the evidence of successful graft copolymerization of GMA onto cellulose initiated by benzoyl peroxide (BPO) and modification with PEI. The amount of epoxy groups of Cell-g-PGMA was4.35mmol g-1, the amount of PEI grafted onto Cell-g-PGMA was found to be0.56mmol g-1(nitrogen7.77mmol g-1).Subsequently, the adsorption behavior of Cu(Ⅱ), Ni(Ⅱ) and Pb(Ⅱ) on Cell-g-PGMA-PEI in aqueous solution has been investigated. Data from the adsorption kinetic experiments agreed well with pseudo-second-order model based on the assumption that the rate-limiting step may be chemisorption involving valency forces through sharing electrons between adsorbent and heavy metallic cation. Meanwhile, within200-240min, the adsorption equilibrium between Cu(Ⅱ), Ni(Ⅱ), Pb(Ⅱ) and Cell-g-PGMA-PEI could be established. The adsorption isotherms of Cu(Ⅱ)、Ni(Ⅱ)、Pb(Ⅱ) can be interpreted by the Langmuir model, Langmuir model and Preundlich model, respectively. The corresponding dynamic adsorption capacity obtained from the column tests was119mg g-1(copper),41mg g-1(nickel),222mg g-1(lead), and the adsorbent could be easily regenerated by HC1of0.1mol L-1.Experimental results indicate that the novel pathway for the synthesis of Cell-g-PGMA-PEI exhibits significant potential to improve the performance of adsorbents in removal and recovery of Cu(Ⅱ), Ni(Ⅱ) and Pb(Ⅱ)from aqueous solution. Therefore, Cell-g-PGMA-PEI is proved one promising and efficient adsorbent for heavy metals in practical application.