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The adsorption kinetics of TCP to GO and G are displayed in Figure 2. For GO and G, the adsorption equilibrium can be reached in less than 6 h. G has a higher adsorption rate than GO, which may be attributed to the higher specific surface areas of G (Table S1, available online). In order to illustrate the adsorption kinetics process, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were employed to fit experimental data. Results are shown in Figure 2 and Figure S2 (available online), and fitting parameters are listed in Table 1. For GO and G, the correlation coefficients (R2) for the pseudo-second-order were relatively higher than those of the pseudo-first-order model, indicating that the pseudo-second-order kinetic model was suitably fitted with the kinetic data. As shown in Figure S2(c), the regressions of qt versus t1/2 were linear, but it did not pass through the origin, suggesting that the adsorption involves intraparticle diffusion but it is not the only rate-controlling step (Zhang et al. 2012; Wang et al. 2016).
Table 1

Kinetic parameters for the adsorption of TCP on GO and G

AdsorbentPseudo-first-order model
Pseudo-second-order model
Particle diffusion model
k1 (min−1)R2k2 (g·mg−1·min−1)R2ki (g·mg−1·min−1/2)R2
GO 0.0097 0.8872 0.0064 0.9947 0.3590 0.8456 
0.0286 0.9188 0.0021 0.9982 1.2872 0.8076 
AdsorbentPseudo-first-order model
Pseudo-second-order model
Particle diffusion model
k1 (min−1)R2k2 (g·mg−1·min−1)R2ki (g·mg−1·min−1/2)R2
GO 0.0097 0.8872 0.0064 0.9947 0.3590 0.8456 
0.0286 0.9188 0.0021 0.9982 1.2872 0.8076 
Figure 2

Adsorption kinetic modeling of TCP on GO (a) and G (b). Solid and dotted lines represent kinetics fitted by the pseudo-first-order model and pseudo-second-order model, respectively. The error bars indicate the standard deviations (n = 3).

Figure 2

Adsorption kinetic modeling of TCP on GO (a) and G (b). Solid and dotted lines represent kinetics fitted by the pseudo-first-order model and pseudo-second-order model, respectively. The error bars indicate the standard deviations (n = 3).

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