Abstract
Binary nanocomposite of magnetite/multi-walled carbon nanotubes (Fe3O4/MWCNTs) was synthesized through the chemical reduction method at room temperature and employed for adsorptive removal of Reactive Violet 2 (RV2) from aqueous solutions. The experiments were carried out based on a Taguchi experimental design with four variables of the adsorbent dosage, pH, contact time and ionic strength. Analysis of variance (ANOVA) showed that the adsorbent dosage with contribution of 79.14% was the most effective factor on the process efficiency. Percent contributions of solution pH and contact time were found to be 9.85 and 6.16, respectively. The ionic strength showed no considerable contribution to the response. The optimal dye removal conditions were determined as the adsorbent dosage of 2.0 g L−1, pH = 6, contact time of 30 minutes and ionic strength of 0.1 mol L−1 which resulted in the average efficiency of 98.23% for RV2 removal. The results showed that RV2 adsorption onto Fe3O4/MWCNTs followed the pseudo-second order kinetic model. Moreover, the intraparticle diffusion model suggested a two-step adsorption process, including macropore diffusion of about 94% of RV2 molecules into the nanocomposite surface during ∼10 minutes and a micropore diffusion as the rate-limiting step. Fitting of the experimental data to six isotherms (Langmuir, Harkins-Jura, Freundlich, Tempkin, Halsey and Redlich-Peterson) was also investigated and Redlich-Peterson and Halsey isotherms provided the best quality of fitting for the dye-nanocomposite system with R2 values of 0.9992 and 0.9906, respectively.
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