Sulfur-replaced Fenton systems: can sulfate radical substitute hydroxyl radical for advanced oxidation technologies?

Sulfate radicals (SO4 center dot-) and hydroxy radicals (HO center dot) are the major radicals used in advanced oxidation technologies (AOTs) for the removal of contaminants. Although SO4 center dot- reacts with organic or inorganic compounds with rate constants comparatively lower than that of HO center dot, AOTs based on SO4 center dot- (abbreviated as SR-AOTs) have gained lots of attention due to the selective oxidation and non-pH-dependence. A series of systems using persulfate (PS) or peroxymonosulfate (PMS) instead of H2O2 is designated as a sulfate radical-Fenton system or sulfur-replaced Fenton system (SR-Fenton). Comparisons and analogies between Fenton (Fenton-like) systems and SR-Fenton systems are made and some new SR-AOTs systems without PS or PMS are introduced. The possibility for the substitution of HO center dot by SO4 center dot- for AOTs is discussed. Most likely in the future, efforts will be concentrated on product-oriented AOTs with the purpose of recovery of chemical products rather than mineralization of organic contaminants, producing greenhouse gas CO2. Moreover, such SR-Fenton system may be more atomically economical. (c) 2014 Society of Chemical Industry