Phenolic compounds are commonly used as pesticides, disinfectants, germicides, and as additives in many industrial processes. Some phenolic compounds have been reported to survive conventional wastewater treatment and persist in the environment. Phenolic compounds such as cresols have been listed as a priority pollutant by the US Environmental Protection Agency and have been classified by the Center for Disease Control as immediately dangerous to life. An environmentally friendly way to degrade phenolic compounds is through photolysis with sunlight irradiation. This study used p-cresol (pC) as a surrogate for phenolic compounds to understand their photodegradation mechanisms. pC irradiation in pure water using a sunlight simulator revealed that pC does not degrade by direct photolysis. When Methylene Blue (MB) is added to the solution, pC undergoes indirect photolysis by 1O2. Control experiments showed no other RIs involved in pC degradation. A kinetic model to predict the photodegradation of pC under sunlight irradiation employing MB as a photosensitizer was developed. The model incorporates changes in pH, Ionic Strength, and Ionic Activity of the system with time, with no adjustable parameters. Model validation was conducted by comparing predicted and experimental results with different conditions and concentration of reactants in the system. Initial concentration of target and photosensitizer, and irradiation time are the inputs for the model which predicts the changes in concentration of target, photosensitizer and RIs with accuracy. The model predicted that the steady state concentration of 1O2 increased from 5.5 x10-11 M to 1x10-10 M with increase in concentration of MB from 3 to 5 mg L-1. The model provides an accurate way to predict the target fate under sunlight irradiation. The model will be validated for other Contaminants of Emerging Concern (CECs). This will provide a tool to predict the photodegradation of CECs in conditions similar to sun exposure of contaminants in surface water.

Kinetic model for the prediction of the photodegradation of phenolic compounds in water

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.