Thermo- and pH-responsive poly(A-ProOMe)--poly (AAc) membrane for selective separation of metal ions

Hasegawa, Shin; Ohashi, Hitoshi; Maekawa, Yasunari; Katakai, Ryoichi*; Yoshida, Masaru

We investigated the permeation behavior of Li over Co and Ni ions through thermo- and pH-responsive gel membranes. The gel membranes were synthesized by -ray grafting of pH-responsive poly (acrylic acid) (AAc) onto a thermo-responsive polymer gel of acryloyl-L-proline methyl ester (A-ProOMe). The permeation constant of Li ions is 3.5 and 2.8 times higher than those of Co and Ni ions at 30 C in a pH 6.0. The most appropriate temperature and pH through the 15% grafted membrane were 30 C and pH 6.0. The adjacencies of the carboxyl groups of poly (AAc) surrounded by thermo-responsive poly (A-ProOMe) matrix must be decisive for the selective Li ion permeability. From the microscopic structures using SEM and the distributions of Co and Ni ions by EDS analysis, we confirmed that the structures formed by the flexible grafted chains of the carboxyl groups onto the thermo-response gel membrane are significant for the selective permeation of Li ion.