Organic dyes and ions selective adsorption and separation from aqueous solution using novel synthetic cross-linked-polydopamine/polyaniline nanoparticles

Abstract

Mussel-inspired polydopamine nanoparticles were cross-linked using a unique water-in-water emulsion method (CPDA). Afterward, CPDA was modified with polyaniline (CPDA@PANI) in an HCl solution to enhance CPDA's adsorption capabilities. The adsorption process of two water-soluble dyes (anionic dye: methyl orange (MO) and cationic dye (methylene blue (MB)) and three ions (anions such as \(\left( {{\text{SO}}_{4} } \right)^{2 - }\), \(\left( {{\text{NO}}_{3} } \right)^{ - }\) and Sn²⁺ as cation) was studied in depth. The pH of solution, temperature, and contact time are affected when determining the quality and ion adsorption of organic dye. Pseud-first- and pseudo-second-order kinetic models were employed to suit the adsorption kinetics. The adsorption kinetic model was determined using four isothermal adsorption models: Temkin, Freundlich, Dubnin–Radushkevich, and Harkins–Jura. Regarding MO, MB, and ionic compounds, the nanoparticles' specific adsorption capacity is relatively high. The adsorption kinetics process followed the pseudo-second-order kinetics model, although the Temkin isotherm model worked better for tracking adsorption behavior than other isotherm models. Additionally, the findings demonstrated that the CPDA@PANI had a highly effective adsorption capacity of 114.4 mg g⁻¹ with a dye removal efficiency of 95.4% in an acidic medium. Also, desorption experiments were conducted using NaOH solutions at various concentrations (0.01–0.13 M), with 0.13 M NaOH achieving the maximum MO desorption efficiency (~ 84.9%). One can, therefore, conclude that CPDA@PANI nanoparticles may be a highly effective adsorbent for some anionic contaminants.