
43Waste from Metal Processing Industries
432
ml H
+
added
10
14
12
10
8
6
4
2
0
14
12
10
8
6
4
2
0
pH
pH
432100.5 1.52.5 3.5
FIGURE 2.5 (a) Buffer curves for red mud titrated with 1M HCl and 1M NaOH; lled
square = rst addition of HCl; lled circle = rst addition of NaOH; empty square = second
addition of HCl; empty circle = second addition of NaOH; and (b) point of zero charge of red
mud; lled squares = the titration with red mud, lled diamonds = the blank titration. The
point of zero charge is given by the intersection of the two pH curves (Pulford etal., 2012).
(Reproduced with kind permission from Elsevier.)