Methods of Persulfate Activation for the Degradation of Pollutants: Fundamentals and Influencing Parameters
Javad Saien, Farnaz Jafari
Abstract
Sulfate radical advanced oxidation processes with relevant high redox potential, long lifetime and selectivity to the electron-rich compounds have been dramatically developed for the aim of efficient degradation of pollutants. Persulfate (S2O82−) and peroxymonosulfate (HSO5−) are common species which supply both the well-known sulfate and hydroxyl active radicals. These persulfate salts have a low environmental impact and rather low price. To overcome the difficult reaction of reagents with organic pollutants, a variety of methods have been employed to generate active radicals through imparting energy and accepting electrons from electron donors. The cost-effective and sustainable strategies of persulfate activation include alkaline, organic substrate, and catalytic activation with no external energy as well as heat, microwave, ultrasound, photo- and electrochemical techniques with external energy. Each activation process could be implemented either in homogeneous or heterogeneous operation modes depending on the presence of a solid-state reagent, catalyst, and/or electrode. In this chapter, the basic concepts, dominant mechanisms, as well as effects of operating parameters, particularly, persulfate concentration, pH, temperature, involved materials, and reactor configuration are discussed for each technique. The comprehensive content will bring greater knowledge and clarity to select the most appropriate persulfate activation method.