Original

Oxidized (dH₂O)

Oxidized (HCl)

Reduced

SEM

Redox potential, mV

−19 ± 2

109 ± 2

481 ± 5

−39 ± 1

${\text{NO}}_3^{-}$ in the filtrand, mg

0.120

0.266

1.125

0.037

0.288

${\text{NO}}_3^{-}$ in the filtrate, mg

18.8^c

43.1^b

52.9^ab

59.5^a

4.9

${\text{NO}}_3^{-}$ recovered, mg

47.4^a

23.0^b

12.4^bc

6.8^c

4.1