Derivative spectrophotometry and multivariate optimization for simultaneous removal of Titan yellow and Bromophenol blue dyes using polyaniline@SiO2 nanocomposite

•PAN@SiO2 nanocomposites have excellent adsorption properties for anionic dyes from water.•Derivative spectrophotometry was developed for determination of dyes concentrations.•Central composite design was used to optimize the removal conditions.•The maximum adsorption capacities (qmax) of dyes were found.•Adsorption process matched with pseudo-second order kinetic and Langmuir isotherm. In the present study, the performance of PAN@SiO2 nanocomposites as an adsorbent to remove Bromophenol blue (BPB) and Titan yellow (TY), was considered in single- and binary-component solutions. PAN@SiO2 nanocomposites were characterized through diverse techniques such as FE-SEN, XRD, FTIR, and EDX. Derivative spectrophotometry (DS) was developed to determine TY and BPB in two-compound mixtures employing ‘zero-crossing’ technique. In fact, useful parameters such as the amount of sorbent, pH, and the initial concentration of each dye were optimized using a four-factor central composite design (CCD) to maximize the percentage removal of TY and BPB dyes from aqueous solution simultaneously. The optimum operation conditions were pH of 3, initial concentration of 202 mg/L for BPB, 218 mg/L for TY and an adsorbent dose of 0.048 g. Under optimal condition, the maximum removal percents of 95% and 84% were obtained for both TY and BPB, respectively. The adsorption kinetics of both TY and BPB dyes were best correlated to the pseudo 2nd order model. The Langmuir isotherm model was appropriate for elucidating the dye adsorption process in single and binary solutions. The maximum uptake capacity (qmax) of TY and BPB was 141.5 mg/g and 129.6 mg/g for the single solution and 129 mg/g and 109 mg/g for the binary solution, respectively. The thermodynamic calculations demonstrated that the adsorption of TY and BPB dyes onto PAN@SiO2 was endothermic and spontaneous. [Display omitted]