The pH in this investigation was in the range of 2.0–5.0. The
COD concentration was around 385 mg/L. Experimental condition
was controlled at [COD]:[Fe2+]:[H2O2] = 1:0.95:3.17. As shown in
Fig. 2(a), COD removal efficiency increased with the increasing initial
pH from 2 to 3, but further increase of pH reduced the removal
efficiency. The same trend was also found in the decolorization
(Fig. 2(b)). Figs. 2(a and b) show that the removals of COD and color
from the textile wastewater in the first 2 min were more rapid than
after 2 min. According to literature [22], that investigation suggested
that the Fe2+ reacts very quickly with H2O2 to produce a
large amount of OH (see Eq. (1)) and then Fe2+ in the solution
was rapidly consumed. This result was also found in Fig. 2(c)).
The OH can react rapidly with organic matter, therefore, the