Photocatalytic degradation of dyes by mononuclear copper(II) complexes from bis-(2-pyridylmethyl)amine NNN-derivative ligands

Abstract

Photocatalytic degradation of organic pollutant dyes under ultraviolet radiation has emerged as an efficient wastewater treatment. This work describes the application of four mononuclear copper(II) complexes coordinated to NNN ligands: bis-(2-pyridylmethyl)amine (BMPA), N-methylpropanoate-N,N-bis-(2-pyridylmethyl)amine (MPBMPA), N-propanoate-N,N-bis-(2-pyridylmethyl)amine (PBMPA) and N-propanamide-N,N-bis-(2-pyridylmethyl)amine (PABMPA); in the photocatalytic degradation of different dyes: methyl orange (MO), methylene blue (MB), crystal violet (CV), Congo red (CR) and Rhodamine B (RhB). The reactions were carried out under a UV lamp of 250 W, where 100% of degradation was achieved in 90 min for all complexes using hydrogen peroxide as oxidant. Kinetic experiments were carried out to investigate the photodegradation of the dyes under a UV lamp of 24 W. The reactions followed a zero-order model in relation to the dye, showing that its concentration did not play a significant role in the photocatalysis. The reaction order in relation to hydrogen peroxide varied from 0 to 0.8, from low to high concentrations of oxidant. The light intensity and the intrinsic catalytic activity of the complexes are the most important features for the dye photodegradation pathway.