Synthesis of magnetite multi-walled carbon nanotubes composite and its application for removal of basic dyes from aqueous solutions

A magnetic composite of multi-wall carbon nanotubes and magnetite nanoparticles was synthesized, and its applicability to the removal of dye contaminants from aqueous solutions was investigated as adsorbent. Tris(4-(dimethylamino) phenyl) methylium chloride or crystal violet (also known as gentian violet) was used as a representative of the basic dyes, and an orthogonal array design with four factors-three levels (3(4)) matrix-was applied to assign the significant factors affecting the dye uptake. The chosen experimental parameters and their ranges were the following: pH, 9-11; adsorbent, 0.002-0.01 g; NaCl concentration, 0-4%; removal time, 1-5 min. L9 orthogonal array for experimental design and the smaller the best criterion based on reduction of residual dye were used to determine the optimum conditions, which were found to be pH = 9, 0.01 g adsorbent, 5 min removal time, and 0% NaCl, respectively. Analysis of variances revealed that the amount of adsorbent affected the adsorption efficiency of crystal violet significantly. The adsorption capacity of sorbent was found to be 38 mg g(-1). The magnetic composite displayed the main advantage of separation convenience compared with the other adsorption techniques. (C) 2014 Curtin University of Technology and John Wiley & Sons, Ltd.