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

Sulfate radicals (SO4•−) and hydroxy radicals (HO•) are the major radicals used in advanced oxidation technologies (AOTs) for the removal of contaminants. Although SO4•− reacts with organic or inorganic compounds with rate constants comparatively lower than that of HO•, AOTs based on SO4•− (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• by SO4•− 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.