Optimization and characterization of Direct Blue 71 removal using nanocomposite of Chitosan-MWCNTs: Central composite design modeling

Adsorption of Direct Blue 71 (DB71) in aqueous solution was investigated by nanocomposites of chitosan-MWCNTs (ch-MWCNTs). The central composite design (CCD) was applied to optimize the adsorption process of DB71. The morphological of nanocomposite was characterized by scanning electron microscopy (SEM), Fourier transfer infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The effects of operational parameters, i.e. the initial dye concentration, pH and adsorbent dosage on the removal of DB71 were studied, and the optimum conditions were defined. All variables were confirmed by Analysis of variance (ANOVA), lack of fit test and residuals distribution consideration and have significant influence on the model response. The quadratic model was obtained for optimization of the process variables for maximum adsorption of DB71 by ch-MWCNTs. The optimum values of input variables were found to be 6.25 (pH), 33 mg/L (DB71 concentration) and 0.1 g (ch-MWCNTs). The experimental isotherm data were analyzed by Langmuir, Freundlich, and Temkin models. Equilibrium data agreed well with Langmuir isotherm (R-2 = 0.9985), Based on this model, the maximum adsorption capacity (q.) of nanocomposite of ch-MWCNTs was obtained to be 2932 mg/g. A pseudo-second order model has been proposed to correlate the experimental data (R-2 = 0.999). (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.