Turning waste into valuables: deposition of polypyrrole on the obsolete mask for Cr(VI) removal and desalination.

The global mask consumption has been exacerbated because of the coronavirus disease 2019 (COVID-19) pandemic. Simultaneously, the traditional mask disposal methods (incineration and landfill) have caused serious environmental pollution and waste of resources. Herein, a simple and green mass-production method has been proposed to recycle carbon protective mask (CPM) into the carbon protective mask/polydopamine/polypyrrole (CPM/PDA/PPy) composite by polymerization of PPy. The CPM/PDA/PPy composite was used for the removal of Cr(VI) and salt ions to produce clean water. The synergistic effect of PPy and the CPM improved the removal capability of Cr(VI). The CPM/PDA/PPy composite provided high adsorption capacity (358.68 mg g) and economic value (811.42 mg $). Consequently, the CPM/PDA/PPy (cathode) was combined with MnO (anode) for desalination in CDI cells, demonstrated excellent desalination capacity (26.65 mg g) and ultrafast salt adsorption rate (6.96 mg g min), which was higher than conventional CDI cells. Our work proposes a new low-carbon strategy to recycle discarded masks and demonstrates their utilization in Cr(VI) removal and seawater desalination.