Application of Response Surface Method for Optimization of Adsorptive Removal of Eriochrome Black T Using Magnetic Multi-Wall Carbon Nanotube Nanocomposite

Abstract

Response surface method was employed to optimize adsorptive removal of Eriochrome Black T (EBT) from aqueous solutions using the magnetic multi-wall carbon nanotube (MMWCNT) nanocomposite. The nanocomposite was synthesized by mixing commercial multi-wall carbon nanotube and a solution containing ferric and ferrous salts in highly basic media at elevated temperature. Properties of the nanocomposite were characterized by scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectrometer, and X-ray diffractometer. Adsorption experiments were carried out based on a central composite design (CCD) with four input variables including adsorbent dosage (w: 2–10 g/L), contact time (t: 35–95 min), pH (2–9), and ionic strength (i: 0.02–0.1). Regression analysis showed good fit of the experimental data to a quadratic polynomial model with coefficient of determination (R 2) value of 0.9897 and Fisher ratio of 103.34. Adequacy of the model was verified by analysis of variance (ANOVA), lack-of-fit test, and residual analysis. Optimum values of the variables for maximum adsorptive removal of EBT were predicted by the model (w = 5.39 g/L; pH = 2.11; t = 78 min and i = 0.08). The observed dye removal of 99.80% in the predicted optimal condition confirmed high efficiency of the response surface method in modeling EBT removal from aqueous solutions using MMWCNT nanocomposite.