Optimization of simultaneous removal of binary mixture of indigo carmine and methyl orange dyes by cobalt hydroxide nano-particles through Taguchi method

Abstract

The simultaneous removal of Indigo carmine(IC) and Methyl orange(MO) in binary mixtures by cobalt hydroxide nanoparticles in batch system is investigated. Taguchi optimization approach (an L16 orthogonal array design) was employed for estimating the important and interactive impressions of some considered variables (such as, initial concentrations of Indigo carmine and Methyl orange, amount of sorbent, initial pH value, and contact time) on the adsorption process. Under the optimized conditions, the maximum removal percent (%R) was equal with 75% and 87% and also the uptake capacity was obtained to be 62.5 and 81.3 mg/g for Indigo carmine and Methyl orange dyes, respectively. Isotherm modeling and kinetic studies indicated that modified Langmuir and pseudo-second-order are good models for illustrating the adsorption equilibrium and kinetic behavior of process. Thermodynamic parameters proved that the adsorption process was endothermic (∆H° > 0) for MO while it was exothermic (∆H° < 0) for IC. Finally, the morphology and structure of the nanosorbent was characterized by using XRD, EDX, SEM, FTIR and TEM techniques.