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

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 co-ordinated 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.