Efficient removal of Congo red dye by adsorption using novel mesoporous chitosan-polyaniline/Nano SiO2 composite

Congo red dye (CR) is a toxic, environmentally persistent compound that exhibits mutagenic and carcinogenic properties. Due to the dye’s persistence and toxicity, its removal from wastewater is a pressing environmental need. This work demonstrates the successful synthesis of a novel CSPAn-based nanocomposite, characterized by appreciably high thermal and mechanical stability, a moderately high surface area, and efficient removal of CR. The composites were fabricated by loading varying amounts of silicon dioxide nanoparticles (SiO2) (5–30%) into the chitosan-polyaniline matrix (CSPAn) via a chemical oxidation procedure. The synthesized materials were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy, and their surface properties (the Brunauer, Emmet and Teller (BET) surface area, total pore volume, mean pore radius, and point of zero charge) were determined. Among the investigated samples, the new CSPAn/nano SiO2-20% composite (CSPAnS3) showed the highest values of both surface area and total pore volume (21.70 m2/g and 0.083 cm3/g, respectively), and high thermal stability. The effect of nanoparticle oxide composition, adsorbent dosage, solution pH, initial dye concentration, contact time, and temperature, on the removal of CR was explored. CSPAnS3 has been found to exhibit superior adsorption efficiency, achieving 100% removal of CR in 40 min. CSPAnS3 composite showed the highest adsorption capacity at 394.93 mgg− 1 and exhibited strong affinity for CR. The adsorption data were fitted to the pseudo-second-order kinetic model, indicating that the interaction between CR molecules and CSPAnS3 is achieved by chemisorption. Electrostatic, hydrogen bonds, and π-π interactions explained the mechanism. The CSPAnS3 adsorbent demonstrated excellent stability and reusability across multiple cycles, underscoring its potential for practical, sustainable applications.