Anthraquinone acted as a catalyst for the removal of triphenylmethane dye containing tertiary amino group: Characteristics and mechanism

Herein, we found that anthraquinone (AQ) acted as a catalyst for the rapid and effective removal of triphenylmethane dye containing tertiary amino group (TDAG). Results showed that AQ had an enhanced catalytic reactivity towards the removal of TDAG compared to hydro-quinone, which was further proved and explained using density functional theory (DFT) calculations. AQs could achieve a TDAG removal efficiency and rate of approximately 100% and 0.3583 min −1 , respectively, within 20 min. Quenching experiments and electron paramagnetic resonance (EPR) tests indicated that the superoxide radical (O 2 •− ) generated through the catalytic reduction of an oxygen molecule (O 2 ) by AQ contributed to the effective removal of the TDAG. In addition, it was found that the electrophilic attack of the O 2 •− radical on the TDAG was the driving force for the dye degradation process. Decreasing the pH led to protonation of the substituted group of AG, which resulted in formation of an electron deficient center in the TDAG molecule (TDAG-EDC + ) through delocalization of the π electron. Therefore, the possibility of the electrophilic attack for the dye by the negative O 2 •- radical was significantly enhanced. This study revealed that the H + and the O 2 •− generated by the catalytic reduction of O 2 have synergistic effects that led to a significant increase in the dye removal rate and efficiency, which were higher than those obtained through persulfate oxidation. l AQ could act as a new catalyst for the removal of the TDAG. l The pH value played a critical role in governing the dye degradation process. l Degradation of the TDAG was attributed to the catalytically generated O 2 •− . l The catalytic performance of AQ in TDAG removal was higher than that of PDS oxidation. .