Simultaneous Determination and Optimization of Titan Yellow and Reactive Blue 4 Dyes Removal Using Chitosan@hydroxyapatite Nanocomposites

Abstract

Chitosan (CS) and hydroxyapatite (HA) nanocomposites have been prepared and used for the simultaneous removal of Titan Yellow (TY) and Reactive Blue 4 (RB 4) dyes from aqueous solutions in single and binary batch systems. Chitosan@hydroxyapatite nanocomposites (NCs) were characterized by diverse techniques such as EDX, FTIR, TGA, and FESEM. Derivative spectrophotometry (DS) was developed to the determination of TY and RB 4 in two-compound mixtures employing the ‘zero-crossing’ technique. The influence of operational variables (such as sorbent mass, contact time, pH, and initial concentration of dyes) on the dyes adsorption is evaluated. A response surface methodology based on a Hybrid central composite design is used to optimize the removal of dyes by CS@HA NCs through a batch adsorption process. In optimum conditions (pH = 4, sorbent dosage = 0.03 g TY (initial TY concentration) = 1100 mg L−1 and RB 4 (initial RB 4 concentration) = 950 mg L−1), the maximum uptake capacities of dyes were obtained 170.7 and 118.4 mg g−1 for TY and RB 4 dyes, respectively. The Langmuir isotherm model was convenient for elucidating the dye adsorption process in both single and binary solutions. The adsorption kinetics of both TY and RB 4 dyes were in best correlation with pseudo 2nd order model. The thermodynamic calculations elaborated that the adsorption of TY and RB 4 dyes was endothermic and spontaneous.