Adsorption of polythiophene/TiO2 composite for Zn (II), Pb (II) and Cu (II): Selectivity and synergistic effect investigation

A composite with self-doping nature, polythiophene (PTh)/TiO2 with impressive selectivity was synthesized in the aqueous medium to support the mechanism on synergistic effect between PTh and TiO2. An interesting self-doping of TiO2(O-) on the polythiophene in the PTh+/TiO2(O-) composite was also prepared with tunable heterojunction structure by adjusting the solution pH. An impressive selective adsorption property with an ascending order of Zn2+ > Pb2+ >> Cu2+ was achieved in the single and competitive adsorption study, where the adsorption for Cu2+ could be almost suppressed. This interesting selective adsorption was confirmed to be caused by the dedoping of TiO2(O-) in the heavy metal ion solution due to the metastable doping form of PTh in non-acid solution from the TGA and electrochemical point of view. While the selective adsorption of the composite was also determined on TiO2. The general mechanisms on synergistic effect and on selective adsorption were successfully convinced through the designed experiment, providing some reliable guidelines for designing adsorbents with selectivity towards specific heavy metal ions. In addition, PTh+/TiO2(O-) composite with high adsorption capacity for Zn2+ and Pb2+ can be readily applied in the practical application, especially in the Cu2+ rich waste water without capacity loss.