Styrene/amidoxime copolymer for the removal of heavy metal from water

The aim of this work is to prepare a low cost chelating material containing amidoxime [1] groups with constant chemical compositions and good mechanical properties [2]. A random copolymer of styrene-acrylonitrile (SAN) with a composition of 70/30 (w/w) was used as a starting materials to increase the mechanical properties with respect to the amidoxime homopolymer. The reaction was carried out by reacting SAN with hydroxylamine in the presence of sodium carbonate and precipitated in water. The conversion of nitrile groups to amidoxime was confirmed by FT-IR analysis. The absorption capacity of styrene/amidoxime (ST/AMO) copolymer towards metal ions was carried out by a continuous flow experiment by loading the resin in a column and flowing a solution of 20 metal ions: Mo2+, Sb2+, Hg2+, Tl2+, Pb2+, Be2+, Al3+, Cr2+, Co2+, Cu2+, Zn2+, As3+, Cd2+, Ba2+, Sn2+, V3+, Mn2+, Ni3+, UO22+, Ag+. Results show a good adsorption capacity towards Ag+, Al 3+, Cr3+,Hg2+, V2+, UO22+, Pb2+, Co2+ and Cu2+. The influence of pH on the adsorption capacity of ST/AMO copolymer was determined for the ions Hg2+, Pb2+, Co2+ and Cu2+, (Figure 1). It can be observed that the chelating properties of the resins decreases as PH decreases. The regeneration of the chelating resin and as consequence the recovering of metal ions has been performed by washing of HCl 2 M and then neutralized with a solution of NaOH. The amount of metal ions recovered from the resin is comparable with that of the adsorption step.