With an increase in the pH values above that of PZC value (more than 7), the result was that the biosorbent surface became predominantly -ve charged which resulted in the enhancement of electrostatic repulsion between IJSP surface and dye anions.
The biosorption of AB25 on IJSP was studied at different AB25 concentrations (range of 25-100 mg [L.sup.-1]).
Therefore, it can be concluded that the pseudo-second-order kinetic model provides a better correlation for the adsorption of AB25 on IJSP at different initial AB25 concentrations, compared to the pseudo-first-order model.
To study the effect of temperature on the influence of removal of AB25, using IJSP, several experiments were carried out at temperature values of 35, 45, 55, and 65[degrees] C; pH value of 5.44; and the AB25 concentration value of 50 mg [L.sup.-1] with the adsorption dosage at 4 g [L.sup.-1].
This may be due to the decrease in the surface activity which suggests that the process of adsorption between AB25 and IJSP is exothermic in nature.
The variation of [DELTA][G.sup.0] and its trend demonstrate that adsorption of AB25 by IJSP is more spontaneous and more favorable, especially at low temperatures in the range used in the study.
In this work, the equilibrium data at different concentrations of AB25 and the adsorption of AB25 on IJSP were modeled with the the Langmuir and Freundlich models.
The [R.sub.L] value for the adsorption of AB25 on IJSP was found to be 0.0124, which indicates that the adsorption is a favorable process.
Similar to the above calculations, for various concentrations of AB25, both equilibrium models, the Langmuir model and the Freundlich model, were extended to understand the effect of temperature of AB25 solutions on IJSP. The values of the Langmuir and Freundlich constants, calculated from the figures (figures are not shown) similar to Figures 12 and 13, are presented in Table 6.
The adsorption capacity of IJSP for the removal of AB25 is shown in Table 7.
The present study has revealed that IJSP is a low-cost and eco-friendly biosorbent for the removal of AB25 from aqueous solution.
Pseudo-second-order kinetics was used to predict the biosorption kinetics as it is the best for the biosorption of AB25 by IJSP, with good correlation.