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The pseudo-second order rate model is expressed as:
formula
6
where h = k2 qe2 which denotes the initial sorption rate (mg/g min) and k2 (g/mg min) is the rate constant of the pseudo-second order equation. The second order rate constant k2 and qe are calculated from the intercept and slope of the plot of t/qt versus t. The experimental data plotted is shown in Figure 8. The calculated values of qe, k1, k2 and R2 are presented in Table 2. The experimental qe value is in agreement with the calculated qe value and the plots show good linearity with an R2 value of 0.983. This indicates that the pseudo-second order kinetic model better represents the adsorption kinetics, suggesting that the adsorption process might be chemisorption. Some of the previous researchers also reported that pseudo-second order model correlates well to the experimental data obtained for the adsorption of As(III) on polymeric Al/Fe modified montmorillonite (Ramesh et al. 2007), fly ash agglomerates (Polowczyk et al. 2010) and maize leaves (Kamsonlian et al. 2011).
Table 2

Kinetic parameters for As(III) adsorption on IOISB adsorbent

 Pseudo-first order parameters
Pseudo-second order parameters
Temp (K)k1 (min–1)R2h (mg/g min)k2 (g/mg min)Experimental qe (mg/g)Calculated qe (mg/g)R2
304 0.1059 0.976 0.0041 2.113 0.0392 0.0441 0.983 
 Pseudo-first order parameters
Pseudo-second order parameters
Temp (K)k1 (min–1)R2h (mg/g min)k2 (g/mg min)Experimental qe (mg/g)Calculated qe (mg/g)R2
304 0.1059 0.976 0.0041 2.113 0.0392 0.0441 0.983 
Figure 8

Second order kinetic model (initial concentration 0.395 mg/L, adsorbent dose 10 g/L, mixing speed 30 rpm).

Figure 8

Second order kinetic model (initial concentration 0.395 mg/L, adsorbent dose 10 g/L, mixing speed 30 rpm).

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