Study and optimization of the adsorption process of methylene blue dye in reusable polyaniline-magnetite composites

Abstract

This study aimed to obtain a reusable composite based on conducting polymer to remove cationic dyes in an aqueous solution. For this, two composites (CPs) with different molar ratios of aniline and magnetite (10:1 and 50:1) were synthesized, characterized, and used as an adsorbent in the methylene blue dye (MB) adsorption studies. The incorporation of Fe3O4 into the PANI matrix was confirmed by FTIR, SEM, N2 physisorption, VSM, and elemental analysis. The response surface methodology (RSM) and central composite design (CCD) were applied to optimize the operating factors (pH, temperature, and adsorbent concentration) and build an empirical model to predict the percentage of MB removal. The 50:1 CP showed better performance for MB removal. The maximum MB removal was 82.5% with optimized factors of pH (12), temperature (15 °C), and adsorbent concentration (2.0 mg L−1). pH and its interaction with the temperature and adsorbent concentration were significant. The adsorption isotherm and kinetic data were fitted by the Langmuir, Freundlich, and pseudofirst-order (PFO), pseudosecond-order (PSO), and intraparticle diffusion (IPD) models. Langmuir isotherm and PSO kinetic models fit closely to the adsorption data. The maximum adsorption capacity was 61.51 mg g–1 in 30 min. IPD revealed that intraparticle diffusion is involved in the adsorption process, but it is not the only rate-limiting mechanism. In conclusion, the conducting polymer with magnetic particles studied showed an excited reusable absorbent for methylene blue dye.