Equilibrium Isotherms for Batch Experiments 481 Langmuir Model

The experimental data were fitted to the Langmuir model and the linearised forms are shown in Figs. 12, 13, 14, 15, 16 and 17 which had high correlation coefficients (R2 > 0.85), thus, showing very good agreement with this model. The high correlation coefficients also indicated a good agreement between the parameters and confirmed the monolayer adsorption of RR158 onto the adsorbent surface. A summary of the results for the calculated values of the Langmuir parameters and the R2 values is tabulated in Table 7. RL indicates the isotherm shape according to

Fig. 12 The linearised Langmuir isotherm for RR158 on CAC's. Experimental conditions: room temperature, 200 rpm, adsorbent dosage = 7.5 g/L
Fig. 13 The linearised Langmuir isotherm for RR158 on CAC's. Experimental conditions: at room temperature, 200 rpm, adsorbent dosage = 10 g/L

the following adsorption characteristics, RL > 1 (is unfavourable), RL = 1 (linear adsorption), RL = 0 (is irreversible) and 0 < RL < 1 (is favourable). The RL values for the present study were found to be 0.264-0.488 for initial dye concentrations of 20-120 mg/L, which is consistent with the requirement for a favourable adsorption

Fig. 14 The linearised Langmuir isotherm for RR158 on CAC's. Experimental conditions: at room temperature, 200 rpm, adsorbent dosage = 12.5 g/L
Fig. 15 The linearised Langmuir isotherm for RR158 on CAC's. Experimental conditions: room temperature, 200 rpm, adsorbent dosage = 15 g/L

process. High Langmuir constant KL indicates high affinity for the binding of RR158. The values of qmax obtained were in the range of 0.0017-0.9728 mg/g for the synthetic dye solutions of 20-120 mg/L and the KL values obtained were in the range of 0.01-0.05 L/mg.

Fig. 16 The linearised Langmuir isotherm for RR158 on CAC's. Experimental conditions: at room temperature, 200 rpm, adsorbent dosage = 17.5 g/L
Fig. 17 The linearised Langmuir isotherm for RR158 on CAC's. Experimental conditions: at room temperature, 200 rpm, adsorbent dosage = 20 g/L
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