Central composite design for optimizing the organic dyes remediation utilizing novel graphene oxide@CoFe2O4 nanocomposite

Abstract

Organic dyes pollution can result in several adverse effects on the ecological environment; hence, the treatment technologies are necessary to alleviate these influences. The present study reports the synthesis and application of magnetic graphene oxide@CoFe2O4 nanocomposite for the removal of various organic dyes in water. Congo red (CR), methyl red (MR), and crystal violet (CV) were selected as representatives of cationic, neutral and anionic dyes. Graphene oxide@CoFe2O4 nanocomposite was structurally characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The central composite design based on response surface methodology was approached to reach the optimal dyes removal conditions. By applying the optimized conditions for CR (Ci = 81.0 mg/L, Dos = 0.9, and pH 5.5), MR (Ci = 92.0 mg/L, Dos = 1.5, and pH 5.0) and CV (Ci = 81.0 mg/L, Dos = 1.2, and pH 7.0), a confirmation test was successfully carried out with very low errors and the outstanding removal efficiencies were attained, between 93.0% and 99.7%. Moreover, adsorption kinetic results indicated that pseudo second-order model was of better description for adsorption of organic dyes over graphene oxide@CoFe2O4 than pseudo first-order model. It was calculated that maximum adsorption capacities from Langmuir were found: MR (78.81 mg/g) < CR (109.18 mg/g) < CV (137.95 mg/g). With such high values, graphene oxide@CoFe2O4 can be nominated as a good candidate for the removal of organic dyes from wastewater.