Magnetic polyaniline nanocomposite modified by multi-walled carbon nanotube for efficient adsorptive removal of methyl orange from aqueous solutions

Azo dyes such as methyl orange pose significant environmental hazards due to their toxicity and persistence in aquatic systems. The design of high-performance, magnetically separable adsorbents is critical for wastewater treatment. In this study, polyaniline-based magnetic nanocomposites, namely PANI/Fe₃O₄ and PANI/Fe₃O₄/MWCNT, were synthesized and evaluated as efficient adsorbents for methyl orange removal from aqueous solutions. The structural and morphological characteristics of the fabricated materials were comprehensively analyzed using standard techniques, and the effects of contact time, pH, temperature, adsorbent dosage, and initial dye concentration were systematically investigated. The maximum adsorption capacity was achieved within 15 min at an initial dye concentration of 15 mg L⁻¹, adsorbent dosage of 0.05 g L⁻¹, and ambient temperature. The optimal pH for adsorption was determined as 6 for PANI/Fe₃O₄ and 8 for PANI/Fe₃O₄/MWCNT. Kinetic data fitted the pseudo-second‑order model (R² = 0.999), indicating chemisorption as the dominant mechanism. Both adsorbents demonstrated exceptional removal efficiency (>99%) and maintained high reusability over ten consecutive adsorption-desorption cycles. The findings highlight the strong promise of PANI-based magnetic nanocomposites as sustainable and regenerative adsorbents for the removal of refractory azo dyes from contaminated water.