Chemistry of persulfates in water and wastewater treatment: A review

Thermal activation can induce persulfate (S2O82−) degradation to form sulfate radicals (SO4−•) that can undergo radical interconversion to form hydroxyl radicals (HO•) under alkaline conditions. The radicals SO4−•/HO• can be present either individually or simultaneously in the persulfate oxidation system. To identify the active radical species, a chemical probe method was developed. An excess of probe compounds was added to the system, and differences between the reactivity of the probes and the potential radical species were observed. The usage of various probes, including tert-butyl alcohol, phenol, and nitrobenzene (NB), for simultaneously identifying SO4−•/HO• was investigated. NB can only react with radicals: it cannot react with persulfate. The reaction rate of NB with HO• is 3000−3900 times greater than that of NB with SO4−•, which is a good candidate for use as a probe for differentiating between SO4−•/HO• reactivity. Furthermore, the effects of pH on the formation of SO4−•/HO• were demonstrated b...

Identification of Sulfate and Hydroxyl Radicals in Thermally Activated Persulfate

Persulfate is the newest oxidant that is being used for in situ chemical oxidation (ISCO) in the remediation of soil and groundwater. In this review, the fundamental reactions and governing factors of persulfate relevant to ISCO are discussed. The latest experiences for ISCO with persulfate are presented, with a focus on the different activation methods, the amenable contaminants, and the reactions of persulfate with porous media, based primarily on a critical review of the peer-reviewed scientific literature and to a lesser extent on non-reviewed professional journals and conference proceedings. The last sections are devoted to identifying the best practices based on current experience and suggesting the direction of future research.

In Situ Chemical Oxidation of Contaminated Soil and Groundwater Using Persulfate: A Review

Degradation efficiencies of azo dye Acid Orange 7 by the interaction of heat, UV and anions with common oxidants: Persulfate, peroxymonosulfate and hydrogen peroxide

The effect of halides on organic contaminant destruction efficiency was compared for UV/H2O2 and UV/S2O82– AOP treatments of saline waters; benzoic acid, 3-cyclohexene-1-carboxylic acid, and cyclohexanecarboxylic acid were used as models for aromatic, alkene, and alkane constituents of naphthenic acids in oil-field waters. In model freshwater, contaminant degradation was higher by UV/S2O82– because of the higher quantum efficiency for S2O82– than H2O2 photolysis. The conversion of •OH and SO4•– radicals to less reactive halogen radicals in the presence of seawater halides reduced the degradation efficiency of benzoic acid and cyclohexanecarboxylic acid. The UV/S2O82– AOP was more affected by Cl– than the UV/H2O2 AOP because oxidation of Cl– is more favorable by SO4•– than •OH at pH 7. Degradation of 3-cyclohexene-1-carboxylic acid, was not affected by halides, likely because of the high reactivity of halogen radicals with alkenes. Despite its relatively low concentration in saline waters compared to Cl–, ...

Comparison of halide impacts on the efficiency of contaminant degradation by sulfate and hydroxyl radical-based advanced oxidation processes (AOPs).

A rapid spectrophotometric determination of persulfate anion in ISCO

Influences of carbonate and chloride ions on persulfate oxidation of trichloroethylene at 20 °C

Trichloroethylene (TCE) and tetrachloroethylene (PCE) are commonly found contaminants in soil and groundwater. However, the persulfate anion (S2O82-) is an oxidant; when activated with ferrous cati...

Hydroxypropyl-beta-cyclodextrin-mediated iron-activated persulfate oxidation of trichloroethylene and tetrachloroethylene

Fenton's reaction is comprised of hydrogen peroxide (H2O2) catalyzed by iron, producing the hydroxyl radical (·OH), a strong oxidant. ·OH in turn may react with H2O2 and iron and is capable of destroying a wide range of organic contaminants. In this laboratory study, Fenton's reaction was observed in aqueous and soil slurry systems using trichloroethylene (TCE) as the target contaminant, with the goal of maximizing TCE degradation while minimizing H2O2 degradation. Fenton's reaction triggers a complex matrix of reactions involving ·OH, H2O2, iron, TCE, and soil organics. In soil slurries with a high fraction of organic carbon (fOC), iron tends to sorb to soil organics and/or particles. In aqueous systems the optimal ratio of H2O2:Fe2+:TCE to degrade TCE in a timely fashion, minimize costs, and minimize H2O2 degradation is 300 mg/L: 25 mg/L: 60 mg/L (19:1:1 molar ratio), while soil slurries with a fOC up to approximately 1% and a soil:water ratio of 1:5 (weight ratio) require about ten times the amount of ...

Nihar Mohanty

Papers

A rapid spectrophotometric determination of persulfate anion in ISCO

Influences of carbonate and chloride ions on persulfate oxidation of trichloroethylene at 20 °C

Hydroxypropyl-beta-cyclodextrin-mediated iron-activated persulfate oxidation of trichloroethylene and tetrachloroethylene

Use of Fenton's Reagent for the Degradation of TCE in Aqueous Systems and Soil Slurries