f temperature from 20 to 60 ◦C at a system pH of 11.00.
The values of qmax and b at different temperatures were determined
from the slope and intercept of Langmuir plots,
respectively. All constant values obtained by this model are
represented in Table 5. Therefore, the b values also indicate
that chitosan had a maximum affinity and higher strength of
synthetic reactive dye wastewater adsorption at lower temperatures.
But the qmax values of chitosan at lower temperatures
were lower than at higher temperatures at equilibrium
conditions of Langmuir plots (Fig. 8). This might indicate
that chitosan could adsorb synthetic reactive dye at high temperatures,
but it had a high affinity and strength for synthetic
reactive dye wastewater adsorption at low concentrations at
low temperatures. For practical application, the concentration
of dye in the wastewater and the values of qmax and b
were also considered for the determination of the most suitable
temperature for wastewater treatment.
The influence of the adsorption isotherm shape is discussed
to determine whether adsorption is favorable in terms
of RL [15], a dimensionless constant referred to as the separation
factor. RL is calculated using the equation [16]