Page 282 - Materials Chemistry, Second Edition

Groundwater Remediation 265

In situ chemical oxidation is considered as one of the remedial alterna-
tives. Determine the stoichiometric amount of potassium permanganate that
needs to be delivered to the zone. What would be the amount if sodium
persulfate is used?

Solution:
Basis: 1 m of aquifer
3
(a) Determine log K from Table 2.5:
ow
log K = 2.6
ow
Use Equation (2.28) to find K :
oc
K = 0.63K = 0.63(10 ) = (0.63)(398) = 251
2.6
oc
ow
Use Equation (2.26) to find K :
p
K = f K = (0.02)(251) = 5.02 L/kg
oc
p
oc
Use Equation (2.25) to find PCE concentration adsorbed onto the
solid:
S = K C = (5.02 L/kg)(400 mg/L) = 2,006 mg/kg
p
(b) Determine the total mass of PCE present in the aquifer (per m ):
3
Mass of the aquifer materials = (1 m )(1,600 kg/m ) = 1,600 kg
3
3
Mass of PCE adsorbed on the solid surface = (S)(M )
s
= (2,006 mg/kg)(1,600 kg) = 3,210,000 mg = 3,210 g
Pore volume of the aquifer = V × ϕ
= (1 m )(35%) = 0.35 m = 350 L
3
3
Mass of PCE dissolved in the groundwater = (C)(V)
l
= (400 mg/L)(350 L) = 140,000 mg = 140 g
Total mass of PCE in the aquifer = dissolved + adsorbed
= 140 + 3,210 = 3,350 g of PCE/m of aquifer
3
(c) MW of PCE (C Cl ) = (12)(2) + (35.5)(4) = 166
4
2
MW of potassium permanganate (KMnO ) = (39)(1) + (55)(1) +
4
(16)(4) = 158
Moles of PCE = 3,350 g/m of aquifer
3
= (3,350 g ÷ 166 g/mole)/m of aquifer
3
= 20.2 moles of PCE/m of aquifer
3
As shown in Equation (5.42), the stoichiometric requirement to
oxidize PCE is 4/3 mole permanganate per mole of PCE.
Stoichiometric amount of KMnO needed per m of aquifer
3
4
= (4 moles of KMnO /3 moles of PCE) × (20.2 moles of PCE/
4
m of aquifer)
3