Eco-friendly synthesis of Cynomorium coccineum extract for controlled production of copper nanoparticles for sorption of methylene blue dye
particular Diffusion to understand the possible mechanisms
tải về 1.78 Mb. Chế độ xem pdf
|
particular Diffusion to understand the possible mechanisms involved in the adsorption process of methylene blue in the (a) (b) Elements Wt % At % C K 26.52 53.09 O K 19.38 21.64 Cu K 54.1 25.27 Total 100 100 (c) (d) Fig. 4 SEM images of copper nanoparticles synthesized using Cynomorium coccineum extract with different magnifications: (a) 1000 , (b) 2500 , (c) 5000, and (d) the elemental analysis determined by EDX. 4268 N. Sebeia et al. presence of the synthesized nano-adsorbents. The fitting curves and the computed kinetic parameters were presented in Fig. 6 and Table 3 , respectively. The conformity between experimen- tal data and the model predicted values was expressed by the correlation coefficients R 2 and the comparison of calculated with experimental adsorption capacities. The pseudo-first- order model ( Fig. 7 a) yielded relatively low R 2 values (0.89– 0.92). Hence it could not describe the kinetic data in this case. It is reported that the pseudo-first-order equation does not fit well with the whole range of contact time in the adsorption experiments and it remains generally applicable over the initial stage of the adsorption processes ( Mazengarb and Roberts, 2009 ). However, following the pseudo-second-order data ( Fig. 7 b), excellent linearity was observed. The correlation coefficients are greater than 0.99 associated with the decrease of the rate constant k2 with increasing initial dye concentra- tion. Moreover, the registered experimental sorption capacities are close to those calculated theoretically. These trends suggest that the chemi-sorption was so significant ( Gucek et al., 2005 ). Regarding the intraparticle diffusion data ( Fig. 7 d), the plots were deviated from the origin indicating that this equation was not the sole rate-controlling step but more than one kinetic process was involved in the adsorption process ( Ho and McKay, 1998 ). 3.4. Isotherms study and thermodynamic parameters determination The study of the adsorption isotherms remains a useful strat- egy to describe both the relationship between the adsorbate concentration in the solution and the solid adsorbent at a con- stant temperature and the design adsorption systems. In this study, Langmuir, Freundlich, Temkin, and Dubinin– Fig. 5 (a) XRD patterns, and (b) TGA curves of the synthesized copper nanoparticles using cynomoriumcoccineum extract. 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11 12 tải về 1.78 Mb. Chia sẻ với bạn bè của bạn:
|