Selective adsorption towards heavy metal ions on the green synthesized polythiophene/MnO₂ with a synergetic effect

Selective adsorption towards heavy metals from the industrial wastewater is of great value. Here, we developed a green synthetic strategy to acquire a polythiophene (PTh)/MnO₂ composite in the aqueous medium. The produced core-shell composite, which featured abundant sulfurs and hydroxyls, provided a platform for the effective heavy metal ion capture, resulting in a rapid adsorption equilibrium within 30 min, and in novel adsorption capacities of 82.10, 30.72 and 60.79 mg g⁻¹ for Pb²⁺, Zn²⁺ and Cu²⁺, respectively. It also showed developable selectivity towards these heavy metal ions, which could be tuned by the core MnO₂, with a competition factor order of P(1.22, Pb²⁺)∼P(1.02, Zn²⁺)≫P(0.508, Cu²⁺). We showed that, through experiments, characterizations and DFT calculation, this selectivity resulted from its synergetic self-doping nature between PTh and MnO₂, by which the PTh would protect hydroxyls from being associated with H⁺ before adsorption, enabling hydroxyls catch heavy metals in a much efficient and selective manner. Moreover, this self-doping nature allowed our composite to be robustly recycled for more than five cycles through a simply acid-base treatment. The provided design principle for the task-specific adsorbent herein would contribute to address challenges concerning heavy metal selective capture in the environmental field.