Energy harvesting from acid mine drainage using a highly proton/ion-selective thin polyamide film

A huge chemical potential difference exists between the acid mine drainage (AMD) and the alkaline neutralization solution, which is wasted in the traditional AMD neutralization process. This study reports, for the first time, the harvest of this chemical potential energy through a controlled neutralization of AMD using H⁺-conductive films. Polyamide films with controllable thickness achieved much higher H⁺ conductance than a commercially available cation exchange membrane (CEM). Meanwhile, the optimal polyamide film had an excellent H⁺/Ca²⁺ selectivity of 63.7, over two orders of magnitude higher than that of the CEM (0.3). The combined advantages of fast proton transport and high proton/ion selectivity greatly enhanced the power generation of the AMD battery. The power density was 3.1 W m^-2, which is over one order of magnitude higher than that of the commercial CEM (0.2 W m^-2). Our study provides a new sustainable solution to address the environmental issues of AMD while simultaneously enabling clean energy production.