Optimising synthesis conditions of PANI-NSA nanotubes for chromium removal

Abstract

Polyaniline-naphthalene-sulfonic acid (PANI-NSA) nanotubes were synthesized and evaluated in this preliminary study for Cr(VI) removal from synthetic wastewater. SEM analysis showed that optimized synthesis conditions produced uniform nanotubes with additional surface spheres, potentially enhancing adsorption performance. Adsorption isotherms (Redlich-Peterson and Langmuir models) suggested a monolayer adsorption mechanism, while kinetic studies (Elovich and Wang two-phase models) indicated chemisorption-driven, diffusion-controlled adsorption. To explore the influence of synthesis conditions, temperature and water volume (as reaction eluent) were varied. PANI-NSA synthesized at 5 °C with 80 mL of water (more dilute) had an adsorption capacity of 374.9 mg g⁻1 (66.72% removal), increasing to 438.2 mg g⁻1 (79.28% removal) at 15 °C with 20 mL of water (i.e. more concentrated). While these results highlight promising trends, further detailed characterization and adsorption optimization studies are required to fully assess scalability and long-term application in industrial Cr(VI) remediation.