Preparation of Copolymers Based on Aniline and 2[2-chloro-1-methylbut-2-en-1-yl]Aniline and Their Application for the Removal of Methyl Orange from Aqueous Solutions

In this work, new copolymers P1-P9 were synthesized by oxidative copolymerization of aniline and 2-[2-chloro-1-methylbut-2-en-1-yl]aniline in HCl solution. The resulting copolymers were characterized by FTIR, UV-vis spectroscopy, thermogravimetric analysis, scanning electron microscopy, nitrogen adsorption-desorption isotherms, and particle size. The equilibrium, kinetics, isotherms, and thermodynamics of adsorption of methyl orange azo dye from aqueous solutions on P1-P9 copolymers were studied. The influence of physicochemical variables (dosage (0.01 g), contact time (480 min), pH (~ 7), dye concentration (20 mg/L or 0.061 mmol/L), temperature (25 °C), ionic strength of the solution) on the specific adsorption of the dye with removal efficiency up to 99.27% was determined. The adsorption of methyl orange followed the Langmuir model (correlation coefficient is 0.9774–0.9987), which corresponded to monolayer adsorption on a homogeneous surface. The kinetics of dye adsorption was described by a pseudo-second-order equation, which was characteristic of chemisorption, with the pseudo-second-order rate constant up to 0.0003–0.0028 g/mg min. The thermodynamic parameters such as ∆G°, ∆H°, and ∆S° were calculated to estimate the nature of adsorption. According to the standard enthalpy (12.37–43.70 kJ/mol), standard entropy (81.47–175.22 J/mol K), and Gibbs free energy (− 52.17-(-24.27) kJ/mol) values, it was determined that the dye adsorption was a spontaneous endothermic process. It was shown that P1-P4 exhibit good adsorption capacity up to 108.63-147.26 mg/g or 0.393–0.445 mmol/g. These copolymers retain high efficiency in five repeated adsorption-desorption cycles. The developed materials were considered to be suitable as cheap regenerated sorbents for anionic pollutants in wastewater.

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