Chemical properties

Un-treated CFA

Treated CFA

pH H₂O

9.5

12.2

Organic Carbon (%)

0.49

0.24

Nitrogen (%)

0.02

0.01

P₂O₅ HCl 25% (%)

0.53

0.11

K₂O HCl 25% (%)

0.1

0.12

MgO HCl 25% (%)

1.96

0.64

CaO 25% (%)

4.82

1.35

Sulphur (%)

0.1

0.28

SiO₂ (%)

31.4

10.9

H₄SiO₄ (%)

0.008

2.50

Al₂O₃ (%)

28.16

8.6

Fe₂O₃ (%)

20.91

4.4

Pb (ppm)

17.1

20.4

Cd (ppm)

10.5

0.9

As (ppm)

n.d.*

n.d.

Hg (ppm)

n.d.

n.d.

Cr (ppm)

326.8

n.d.

Ni (ppm)

40.0

15.3