Fundamentals of ISCO Using Persulfate

Abstract

ScopeChemistry and use of persulfate for in situ chemical oxidation of subsurface contaminants, including free radical and other reaction mechanisms, catalysts, subsurface transport, and contaminant treatability. Key ConceptsPersulfate reaction chemistry is complex. Persulfate can react through direct electron transfer or free radical reactions. Electron transfer reactions are relatively slow and selective. Upon activation, the free radicals generated have nonspecific reactivity that allows for the degradation of a wide range of organic contaminants. The radicals that are presently understood to play a major role in reactions are the sulfate radical and the hydroxyl radical. However, there is emerging evidence that the superoxide anion and the perhydroxyl radical also may be important. Persulfate activation may be achieved by heat, chelated or non-chelated transition metals (especially iron), hydrogen peroxide, and alkaline pH conditions. The efficiency, effectiveness, and reaction products may vary between contaminants, activation methods, and the porous media to be treated. Carbonate, bicarbonate, or chloride ions can act as free radical scavengers and reduce reaction efficiency and effectiveness. The kinetics of reaction between persulfate and target compounds is complex. To simplify, pseudo first-order kinetics are often assumed. However, these usually require laboratory estimation because extrapolating between systems is difficult. The interaction of aquifer solids and persulfate is not well understood; persulfate does react with aquifer solids resulting in oxidant consumption, but the rate and magnitude of this process are not well characterized. Persistence varies from days to months, depending on conditions. The impact of persulfate on metal mobility is not well understood. Conceivably, persulfate could impact metal concentrations in groundwater through modification of pH, oxidation of metals, injection of activation amendments, and other mechanisms.

Persulfate activation during exertion of total oxidant demand

“…The initial concentration of persulfate was 10 g/kg or 0.042 M in the aqueous phase. Sodium hydroxide was added in a 2:1 base:persulfate molar ratio; the initial concentration of sodium hydroxide was 0.084 M. The persulfate dose used in this study is similar to doses typically used in the field (Petri et al, 2011). The corresponding dose of sodium hydroxide was a 2:1 M ratio of NaOH:persulfate, which neutralizes the two moles of sulfuric acid generated per mole of persulfate activated.…”

“…A common analysis conducted for persulfate ISCO treatability studies is total oxidant demand (TOD); sodium persulfate concentrations are measured at time ¼ 0 and time ¼ 5 days, and TOD is defined as the mass of persulfate consumed over the 5 days per mass of soil (g/kg). Because the cost of sodium persulfate is relatively high, a TOD >10 g/kg is considered too costly for field applications (Petri et al, 2011). Soil organic matter often comprises a significant fraction of the TOD (Haselow et al, 2003).…”

“…Therefore, TOD evaluation is necessary in permanganate treatability studies to ensure the permanganate dose is sufficient to destroy contaminants. TOD evaluations for activated persulfate ISCO were adopted as an integral part of treatability studies because the consensus among practitioners was that persulfate TOD is exerted the same way as for permanganate; i.e., that persulfate preferentially oxidizes the soil organic matter, and contaminant oxidation proceeds only after the soil organic matter is consumed (Petri et al, 2011).…”

Electrochemical Oxidation of Phenol using Persulfate and Nanosized Zero-valent Iron

“…최근 십수년간 과황산염(persulfate)을 이용한 오염지하 수 및 폐수의 산화처리 기술이 주목을 받아왔다 (Petri et al, 2011). 과황산염은 물에 용해되었을 때 과황산이온…”

Chemical oxidation using stabilized hydrogen peroxide in high temperature, saline groundwater impacted with hydrocarbons and MTBE

“…The process of chemical oxidation has the potential to destroy toxic compounds and remediate a wide range of contaminants (Kashir & McGregor, ; Petri et al., ; Petri, Watts, Teel, Huling, & Brown, ; Sra, Thomson, & Barker, ; Usman, Faure, Hanna, Abdelmoula, & Ruby, ; Usman, Faure, Ruby, & Hanna, ; Usman, Faure, Ruby, & Hanna, ; Yen, Chen, Kao, Liang, & Chen, ). For the treatment of impacted soil and groundwater, chemical oxidants are usually applied in situ , which is commonly referred to as in situ chemical oxidation (ISCO).…”