Selective Adsorption of Methyl Orange Dye by Novel Synthetic Crosslinked-Polydopamine/Polyaniline Nanoparticles

Abstract

Abstract A novel technique known as water-in-water emulsion was utilized to synthesize the cross-linked nanoparticles of polydopamine@polyaniline (CPDA@PANI). The synthesized nanoparticles demonstrated their ability to selectively adsorb methyl orange (MO) from aqueous media. Solution pH and contact time are the influential factors employed to ascertain the optimal conditions for organic dye adsorption. Both pseudo-first and pseudo-second-order kinetic models were utilized to fit the adsorption kinetics. Four isothermal adsorption models were used to find the adsorption kinetics model, including Dubnin-Radushkevich, Temkin, Freundlich, and Harkins-Jura. The results revealed that the nanoparticles presented a higher adsorption capacity of 114.48 mgr/gr in acidic medium than in alkaline conditions with dye removal efficiency of 95.4%. This phenomenon can be explained by protonating PANI, which leads to a strong electrostatic attraction between amino and imine groups with MO. By conforming to the pseudo-second-order kinetics model, the adsorption kinetics process displayed a favorable fit, and it was found that the Freundlich isotherm model was more effective for monitoring and assessing adsorption behavior than other available models. It can be derived from this analysis that the absorption of the dye in CPDA@PANI nanoparticles can be categorized as a single-layer adsorption process with homogeneous absorption sites on the nanoparticles.