The on the adsorption site so the residual

The effect of the amount of adsorbent dosage was determined by
varying the amount of adsorbent dosage added at a particular MB concentration,
pH and temperature. This present study observed that with an increase of the amount
of adsorbent, the percentage removal of MB dyes also increases until reaching an equilibrium value after 0.16g which
corresponded to 96.6% of dye adsorption. The increase of adsorption due to the
adsorbent dosage can be attributed to a greater
surface area and more availability on the adsorption sites. However, at dosage beyond 0.16g, the surface of
adsorbent becomes fully covered with MB molecules due to the aggregation or
overlapping on the adsorption site so the residual concentration in the
solution becomes high. This causing the
removal efficiency become constant and the incremental of MB removal become
very low as the concentration of MB on the adsorbent surface and in the
solution become equilibrium to each other. This finding agreed with other
researchers (Edokpayi et al., 2015)(Rahman et al., 2012)(Kose et
al., 2014)The adsorption of MB on the
CFFS adsorbent is greatly influenced by the initial pH of the solution. In
order to optimize the pH, adsorption of MB was carried out over the pH range
from 3 to 10 at room temperature (30°C). The result indicated that there is a steep increase in the adsorption of MB from 3
to 8 and no significant change occur
after pH 8. Similar findings were reported by many authors (Pathania et al., 2017)(Njoya et al., 2017)(Cont, 2015).

The pH curve obtained explains
that the maximum adsorption takes place
at both natural and slightly basic pH. This is due to the electrostatic
interaction of MB which has a cationic structure with the negative charge of
the adsorbent. On the contrary, at lower pH value, the development of positive
charge on the adsorbent might occur and
causes the surface area of the adsorbent become gradually protonated and
competitive adsorption occurred between the H+ ions and the free MB
ions on the active sites thus decrease the adsorption of MB (Jirekar et al., 2014). So, it can be concluded that
CFFS adsorbent showed good removal capacity in the basic medium than in acid medium. The effect of MB concentration
on the adsorption of MB was investigated in the concentration range from 25-150
mg/L at room temperature without changing the pH of the MB and adsorbent
dosage. In this study, the removal of MB was represented in Figure 4.5 where
the percentage of dye uptake decreased with increasing initial dye
concentration. The adsorption of the dye was
constant at the initial stage and reach
equilibrium between 25 mg/L to 75 mg/L. the adsorption was high at the
beginning due to higher availability of actives sites on the adsorbent surface.

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However, the uptake of MB dye
become lower at higher concentration due to an increased ratio of initial
adsorption number of moles of dyes to the available surface area. So, high
number of ions competing for the available sites on the surface of adsorbent at
higher dye concentration. Similar result was also reported by other researcher (García et al., 2014).

 

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