3.2.3. Effect of pH
MB exists in aqueous solutions in form of positively charged ions
(cationic dye) and the degree of its adsorption on the membrane
surface is primarily influenced by the membrane surface charge, in
turn influenced by the solution pH.
Figs. 2c and 3c show the behavior of adsorption capacity and
removal efficiency in function of pH, respectively, both evaluated
using the starting solution at 250 mg L
−1
, an adsorbent dosage of
1 g L
−1
, an equilibration time of 24 h and a temperature of 20
◦
C.
As can be seen, the adsorption capacity increased with increase
of the pH up to 10. This was due to both higher amount of negatively
charged groups of keratin at pH higher than its isoelectric point
(4–4.5) and to lesser competition between protons (H
+
) and the
MB molecules at higher pH. For the same reasons an increase of
removal efficiencies with increasing the pH occurred
3.2.3. Effect of pH
MB exists in aqueous solutions in form of positively charged ions
(cationic dye) and the degree of its adsorption on the membrane
surface is primarily influenced by the membrane surface charge, in
turn influenced by the solution pH.
Figs. 2c and 3c show the behavior of adsorption capacity and
removal efficiency in function of pH, respectively, both evaluated
using the starting solution at 250 mg L
−1
, an adsorbent dosage of
1 g L
−1
, an equilibration time of 24 h and a temperature of 20
◦
C.
As can be seen, the adsorption capacity increased with increase
of the pH up to 10. This was due to both higher amount of negatively
charged groups of keratin at pH higher than its isoelectric point
(4–4.5) and to lesser competition between protons (H
+
) and the
MB molecules at higher pH. For the same reasons an increase of
removal efficiencies with increasing the pH occurred
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