[M
2+
]/ mg dm
–3
k
obs
x 10
–2
/ s
–1
Cu
2+
Fe
2+
Zn
2+
Mn
2+
Co
2+
Ni
2+
0.1
0.2
0.3
0.4
0.5
1.03
1.05
1.12
1.20
1.45
2.94
4.40
4.54
5.04
6.46
1.24
1.28
1.55
1.51
1.51
1.32
1.42
1.43
1.51
1.45
1.37
1.45
1.39
1.46
1.11
0.63
0.95
1.08
0.89
1.04
Table 2:
Influence of transition metal ions on the rate of decolorization (k
obs
) of MB
+
with SO
3
2−
. ([MB
+
]
o
= 20 mg/dm
3
; [Na
2
SO
3
] = 1.0 mol/dm
3
; pH = 8-9; T = 30°C ).
