Clean and effective removal of Cl(-I) from strongly acidic wastewater by PbO2

Recycling strongly acidic wastewater as diluted H 2 SO 4 after contaminants contained being removed was previously proposed, however, Cl(-I), a kind of contaminant contained in strongly acidic wastewater, is difficult to remove, which severely degrades the quality of recycled H 2 SO 4 . In this study, the removal of Cl(-I) using PbO 2 was investigated and the involved mechanisms were explored. The removal efficiency of Cl(-I) reached 93.38% at 50℃ when PbO 2 /Cl(-I) mole ratio reached 2:1. The identification of reaction products shows that Cl(-I) was oxidized to Cl 2 , and PbO 2 was reduced to PbSO 4 . Cl 2 was absorbed by NaOH to form NaClO, which was used for the regeneration of PbO 2 from the generated PbSO 4 . Cl(-I) was removed through two pathways, i.e., surface oxidation and •OH radical oxidation. •OH generated by the reaction of PbO 2 and OH − plays an important role in Cl(-I) removal. The regenerated PbO 2 had excellent performance to remove Cl(-I) after six-time regeneration. This study provided an in-depth understanding on the effective removal of Cl(-I) by the oxidation method.