Understanding the self-catalyzed decomplexation mechanism of Cu-EDTA in Ti3C2Tx MXene/peroxymonosulfate process

Self-catalyzed decomplexation of Cu-ethylene diamine tetraacetic acid complex (Cu-EDTA) and recovery of Cu without addition of extraneous transition metals were achieved in Ti3C2Tx MXene/peroxymonosulfate (Ti3C2Tx/PMS) process. Free radical quenching experiments and electron spin resonance (ESR) measurements demonstrated that both hydroxyl radical (HO•) and sulfate radical (SO4•-) contributed to the degradation of Cu-EDTA. Activation of PMS by Ti3C2Tx initiated Cu-EDTA decomplexation and released free Cu ions. Then, the formation of Ti-O-Cu bonds between Cu ions and Ti3C2Tx accelerated the electron transfer from Ti3C2Tx to Cu(Ⅱ) and triggered Cu(Ⅱ)/Cu(Ⅰ) cycle, which further enhanced PMS activation and led to the self-catalyzed decomplexation of Cu-EDTA. Simultaneous recovery of Cu was achieved due to the excellent absorption performance of negative charged Ti3C2Tx towards Cu ions. This study revealed the self-catalyzed decomplexation mechanism of Cu-EDTA in the Ti3C2Tx/PMS process and provided a feasible strategy for heavy metal complexes treatment.