Promotion effect of Cl- on the decoloration of rhodamine B in Cu(II)/peracetic acid process: Performance and mechanism

Usually, Cu(II) cannot effectively activate peracetic acid (PAA), but it was observed that the high concentration of Cl^- in Cu(II)/PAA process could notably promote the decoloration of rhodamine B (RhB) in the preliminary experiment. Therefore, the mechanism on the enhanced effect of Cl^- in Cu(II)/PAA process for RhB decoloration was investigated in detail in this work. With the addition of Cl^- in Cu(II)/PAA process, it could rapidly combine with Cu(II) to produce highly active Cu(II)-Cl_n complexes, which could promote the Cu(II) reduction to Cu(I) and subsequent PAA activation. At pH 8.5, the RhB decoloration efficiency in Cl^-/Cu(II)/PAA process could reach 85.8 %, and CH₃C(O)OO^• and CH₃C(O)O^• mainly contributed to the decoloration of RhB in this condition. However, at pH 4.0, reactive chlorine species were considered to be responsible for RhB decoloration in this process. The increase of Cu(II), PAA and Cl^- dosage facilitated the RhB decoloration in Cl^-/Cu(II)/PAA process, while the excessive Cl^- inhibited RhB decoloration. HCO₃^- showed an apparent improvement effect on RhB decoloration, while fulvic acid (FA) obviously suppressed RhB decoloration. This work provides a deep insight on the facilitation effect of Cl^- in Cu(II)/PAA process and a strategy to broaden PAA catalysis via Cu(II).