Central composite design optimization study of the sorption of Bemacid blue Anthraquinone dye by Fe3O4-bentonite from a cupric medium

Abstract

ABSTRACT The present research was devoted to the optimisation of the sorption of Bemacid Blue Anthraquinone dye (BB) in a cupric medium by a magnetic bentonite intercalated with iron oxide ‘Fe3O4’ (M-Bt). The structural and morphological characteristics of adsorbent was studied by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), BET specific surface area and Fourier Transformed Infrared Spectroscopy (FTIR) analysis. A quadratic model was applied to assess and correlate the influential experimental variables using the central composite design (CCD) method. The results of the batch design experiments indicated that the four factors studied initial pH of the solution (1–5), contact time (5–25 min), concentration of copper (1–25% by weight) and the nature of counter ions (Cl−, SO4 −2, NO3 −) play an important role in the sorption process. The R2 = 0.9945 showed the consistency of the model with the experimental data; the predicted (RPred 2 = 0.9851) and fitted (RAdj 2 = 0.9068) reflected the robustness of the model. The analysis of variance (ANOVA) of the quadratic model showed that the model is highly significant and its percentage contribution in descending order is as follows: contact time (28%) > pH (27%) > nature of counter ions (23%) > copper concentration (15%). Applying the desirability function, an optimal removal efficiency of the BB dye by the Fe3O4/bentonite nanocomposite of 93.28% was obtained for a contact time of 21.49 min, a pH of 1.38 and a mass percentage of 12.97% Cu(cl)2. The three-dimensional graphs confirmed the relationships between the sorption of the BB dye and the factors studied, describing the behaviour of the sorption system in a batch process. However, the synthesis of bentonite intercalated with Fe3O4 could be considered as a potential adsorbent for the removal of Bemacid Blue dye in wastewater treatment.