Synthesis And Properities Study Of Temperature And Chemical Dual-stimuli Responsive Cd²⁺ Heavy Metal Ions Absorbent

Heavy metals polltants are known to be toxic and they can easily enter the food chain and cause serious toxicity to human beings and other organisms with gradual accumulation.Various methods for heavy metal removal from wastewater have been extensively developed and adsorption is considered to be one of the most effective method.Polymeric sorbents containing ligands such as ion exchange groups or chelating agents have received special interest.Reversible addition-fragmentation chain transfer?RAFT?polymerization was employed to synthesize copolymer poly?methyl acrylate-b-N-isopropylacrylamide-b-methyl acrylate??PMA-b-PNIPAM-b-PMA?.With the breaking of trithiocarbonates,hydrazide was obtained by hydrazinolysis of the methyl ester then reacted with2,4-dinitrobenzaldehyde to introduction of acylhydrazone.Finally we achieved the polymericsorbentspoly?2,4-dinitrobenzaldehydeacryloylhydrazone?-b-N-isopropylacrylamide)?PDAH-b-PNIPAM?comprising both thermo-sensitive block and chemical sensitive block.FT-IR,¹H NMR spectroscopy and GPC analysis verified the polymeric sorbents with clear structure and narrow molecular weight distribution.A detailed examination of the effect of contact time and the concentration of heavy metal ion Cd?II?on the adsorption characteristics was performed.The LCST is slightly decrease with the increase of mole ratio of PDAH copolymer block.The copolymeric adsorbent with 10.1%mole ratio of PDAH copolymer block exhibits maximum adsorption capacity.The Lagergren adsorption second-order kinetic model and the Freundlich isotherm model fitted the experimental data well,which indicating that Cd²⁺have been adsorbed via chemical reactions and the adsorption sites on the surface of the polymeric sorbents were heterogeneous.This results is consistent with the structural formula of the thermosensitive polymeric sorbents.The recovery and recycle investigation indicated that the dual-stimuli sensitive block copolymeric adsorbent showed very good renewability.