5.2 Materials and Methods
95
5.2.2 Preparation of Membrane
The membranes were developed utilizing a phase separation approach as Osifo et al.
[3]. Most experts [10, 12, 13] also used this method to make chitosan beads. Chitosan
formulations were made with a concentration of 7 wt% by breaking down the chitosan
particles in an acetic acid solution (4 wt% in distilled water). The formulation of
the gelatinous chitosan was placed into a mould on a smooth plane (glass plate).
The mould and chitosan formulation were properly poured in a 5 wt% minimum
aqueous sodium hydroxide solution (97% high purity, supplied by Saarchem Ltd.)
at a constant temperature of 25 °C for 15 min. The produced membranes were
rinsed after production using running distilled water (<0.5 µS cm
−1 ) for two min,
separating the membranes and moulds from the plate of glass. Instead, the membranes
were separated from the moulds and submerged for 1 h in distilled water. After
immersing the membranes in the distilled water, they were washed again using fresh
distilled water till a neutral pH was observed. The disc-shaped formulations had an
approximate size of 0.8 (±0.02) mm with a diameter of 47 mm. It was observed that
the concentration of chitosan had a strong impact on the solution’s moisture content
and that the other factors, i.e. variations in concentrations of acetic acid and sodium
hydroxide, had no effect on the solution’s moisture content [3].
The membranes were cross-linked in a 2.5 wt% glutaraldehyde solution (25%
natural provided by Merck) at a temperature of 25 °C to avoid the membrane from
breaking down in acidic water. A glutaraldehyde solution with a concentration of
1.5 cm
3 per gram of wet membrane was applied. The membranes were properly rinsed
following cross-linking, to eliminate possible excess glutaraldehyde. The membranes
were classified as a thick polymer matrix, and the physicochemical characteristics
were examined. The membranes had a wet density of 1100 kg m
−3 according to our
earlier studies [3], a chitosan volume of 5.2 wt%; a free water volume of 65 wt%; a
fixed water holding capacity of 30 wt; a maximum pore radius of 40 nm; and a total
surface area of 1.15 × 10
5 m
2 kg
−1 .
The CS and XCS zero charge point (pH PZC ) was calculated using the methodology
defined by Igberase et al. [1, 14]. In short, 45 mL of documented concentration
solution KNO 3 was put in a collection of Erlenmeyer flask. The solution’s initial pH
(pH i ) measurements were controlled from pH 2 through eight either by introducing
0.1 M HCl or NaOH. The maximum mixture volume in each flask was composed of
50 mL by adding the KNO 3 solution. The solution’s pH i was recorded, so every beaker
was introduced with 0.45 g of adsorbent. The suspensions were remotely rattled and
enabled to stabilize with periodic controlled rattling for 48 h. The maximum pH
values of the supernatant liquids (pH f ) were indicated. The variation was plotted
against the pH i between the initial and final pH values (pH = pH f − pH i ). The
resultant point of intersection at which pH = 0 gave the pH PZC .
95
5.2.2 Preparation of Membrane
The membranes were developed utilizing a phase separation approach as Osifo et al.
[3]. Most experts [10, 12, 13] also used this method to make chitosan beads. Chitosan
formulations were made with a concentration of 7 wt% by breaking down the chitosan
particles in an acetic acid solution (4 wt% in distilled water). The formulation of
the gelatinous chitosan was placed into a mould on a smooth plane (glass plate).
The mould and chitosan formulation were properly poured in a 5 wt% minimum
aqueous sodium hydroxide solution (97% high purity, supplied by Saarchem Ltd.)
at a constant temperature of 25 °C for 15 min. The produced membranes were
rinsed after production using running distilled water (<0.5 µS cm
−1 ) for two min,
separating the membranes and moulds from the plate of glass. Instead, the membranes
were separated from the moulds and submerged for 1 h in distilled water. After
immersing the membranes in the distilled water, they were washed again using fresh
distilled water till a neutral pH was observed. The disc-shaped formulations had an
approximate size of 0.8 (±0.02) mm with a diameter of 47 mm. It was observed that
the concentration of chitosan had a strong impact on the solution’s moisture content
and that the other factors, i.e. variations in concentrations of acetic acid and sodium
hydroxide, had no effect on the solution’s moisture content [3].
The membranes were cross-linked in a 2.5 wt% glutaraldehyde solution (25%
natural provided by Merck) at a temperature of 25 °C to avoid the membrane from
breaking down in acidic water. A glutaraldehyde solution with a concentration of
1.5 cm
3 per gram of wet membrane was applied. The membranes were properly rinsed
following cross-linking, to eliminate possible excess glutaraldehyde. The membranes
were classified as a thick polymer matrix, and the physicochemical characteristics
were examined. The membranes had a wet density of 1100 kg m
−3 according to our
earlier studies [3], a chitosan volume of 5.2 wt%; a free water volume of 65 wt%; a
fixed water holding capacity of 30 wt; a maximum pore radius of 40 nm; and a total
surface area of 1.15 × 10
5 m
2 kg
−1 .
The CS and XCS zero charge point (pH PZC ) was calculated using the methodology
defined by Igberase et al. [1, 14]. In short, 45 mL of documented concentration
solution KNO 3 was put in a collection of Erlenmeyer flask. The solution’s initial pH
(pH i ) measurements were controlled from pH 2 through eight either by introducing
0.1 M HCl or NaOH. The maximum mixture volume in each flask was composed of
50 mL by adding the KNO 3 solution. The solution’s pH i was recorded, so every beaker
was introduced with 0.45 g of adsorbent. The suspensions were remotely rattled and
enabled to stabilize with periodic controlled rattling for 48 h. The maximum pH
values of the supernatant liquids (pH f ) were indicated. The variation was plotted
against the pH i between the initial and final pH values (pH = pH f − pH i ). The
resultant point of intersection at which pH = 0 gave the pH PZC .