Effect of humic substances on the electrochemical reduction of p -nitrophenol

p -Nitrophenol (PNP) is the main hydrolysis product of methylparathion (MP), one of the most commonly used organophosphate insecticides in the world. Such a product is very toxic for human and animals. Humic substances (HS) are natural recalcitrant organic matter found in soil and waters that have an ability to interact, immobilize, and degrade pesticides. This article presents electroanalytical and UV-Visible studies, conducted to understand the effect of the HS on the PNP reduction process and therefore to understand how the HS can influence PNP degradation in the environment. Electroanalytical results showed that the HS benefit the reduction of the nitro-group of PNP by electrocatalysis. UV-Visible spectra showed that the catalytic effect of HS occurs due to the interection between the PNP and the HS followed by a proton donor mechanism.