Page 219 - Materials Chemistry, Second Edition

202 Practical Design Calculations for Groundwater and Soil Remediation

react very quickly and persist for very short periods of time (less than 1 s).
Permanganate-based ISCO is more fully developed than the other forms of
oxidant [8].

5.6.3 Oxidant Demand
In a chemical oxidation process, the COCs will be oxidized and the oxidant
will be reduced. The reaction involves electron transfers in which the oxidant
will serve as a terminal electron acceptor by accepting the electrons from the
COCs. The half-reactions of some common oxidants are:

MnO + 4H + 3e → MnO + 2H O (5.34)
+
−
−
4
2
2
H O + 2H + 2e → 2H O (5.35)
+
−
2
2
2
+
2 ∙ OH + 2H + 2e → 2H O (5.36)
−
2
O + 2H + 2e → O + H O (5.37)
+
−
3
2
2
S O + 2e → 2SO 4 2− (5.38)
−
2−
2
8
∙SO + e → SO 4 2− (5.39)
−
−
4
O + 4e → 2O 2− (5.40)
−
2
These equations show that each mole of hydroxyl radical (∙OH) or sulfate
radical (∙SO ) can accept one mole of electrons; each mole of hydrogen per-
−
4
oxide, ozone, or persulfate can accept two moles of electrons; each mole of
permanganate can accept three moles of electrons; and each mole of oxygen
can accept four moles of electrons. Table 5.3 tabulates the amount of oxidant
needed to transfer one mole of electrons. For a given mass of COC, a smaller
oxidant amount would be needed for oxidants that transfer more electrons
per unit mass (e.g., oxygen). However, this is not an indicator of whether the
TABLE 5.3
Amount of Oxidant Needed to Transfer One Mole of Electrons
Electrons Molecular Moles of Electrons Accepted
Accepted Weight per Unit Mass of Oxidant
Potassium permanganate 3 158 0.0190
Hydrogen peroxide 2 34 0.0588
Ozone 2 48 0.0417
Sodium persulfate 2 238 0.0084
Oxygen 4 32 0.1250