Simultaneous removal of Basic blue and Toluidine blue O dyes by Magnetic Fe3O4@polydopamine nanoparticle as an efficient adsorbent using derivative spectrophotometric determination and central composite design optimization

Abstract

• Toluidine blue (TO) and basic blue (BB) dyes can be removed simultaneously from aqueous solutions in a simple and rapid manner. • The experimental design was used to analyze variables' interaction and achieve optimal conditions. • In order to analyze dye concentrations, derivative spectrophotometry was used. • Pseudo-second-order kinetics is consistent with adsorption kinetics data. • FT-IR, SEM, VSM, and XRD analyses were performed on the novel sorbent to characterize it. Simultaneous determination and removal of Toluidine blue (TO) and basic blue (BB) dyes by dopamine-modified magnetic nanoparticles was considered. Nanomagnetic oxide coated with polydopamine (PDA) acid is introduced as a new and efficient adsorbent to remove cationic dyes in a binary mixture solution. Characterization of the Fe 3 O 4 and Fe 3 O 4 @PDA nanoparticles was also supported by FT-IR, XRD, SEM, and VSM analysis. First-order derivative spectrophotometry is employed to simultaneously determine TO and BB in a binary mixture. Linear range for TO and BB in binary mixture obtained by least square equations (y= 0.00014x+ 0.00013 and y= - 0.00136x- 0.00487) were 2-20 mg L -1 and limit of detection 0.4 and 0.3 mg L -1 , respectively. The effect of independent factors such as pH, dye’s initial concentration (C 0 ), and adsorbent amount (m) on the dyes adsorption process was investigated. The response surface methodology was employed by running a central composite design (CCD) to obtain optimal values for dye removal percent. It leads to optimum conditions as follows: pH= 10˛ m=25 (mg), C TO =320 (mg L -1 ), C BB =350 (mgL -1 ), %R TO =85, %R BB =80. Kinetic data followed a pseudo-second-order model while equilibrium data were well described by the Freundlich model. Using Langmuir's isotherm, the maximum monolayer uptake capacity q max for single system and binary systems, respectively, were 381 mg g -1 and 355 mg g -1 for BB, and 362 mg g -1 340 mg g -1 for TO. The negative value of △G o and the positive value of △H o (12.52 kJ mol -1 for TO and 12.98 kJ mol -1 for BB) demonstrated the spontaneous and endothermic nature of both dyes' adsorption.