Rice husk composite with polyaniline, sodium alginate and polypyrrole: naphthalene adsorption kinetics, equilibrium and thermodynamic studies

In this investigation, composites consisting of polypyrrole (PPy), polyaniline (PAN), and sodium alginate combined with rice husk (RH) biomass were fabricated, utilizing them as adsorbents for naphthalene. The optimization of key process variables, including pH, pesticide concentration, composite dosage, contact time, and temperature were systematically undertaken to enhance the removal efficiency of naphthalene. Notably, the composites exhibited promising efficacy in adsorbing naphthalene, with native rice husk and PPy/RH (at pH 4), PAN/RH (at pH 5), and Na-alginate/RH (at pH 6) displaying the highest removal rates. Optimized conditions for composite dosage, temperature, and contact time were determined as 0.05 g, 30 °C, and 90 min, respectively, ensuring efficient removal of naphthalene. The adsorption capacities for naphthalene were found to be 22.04, 23.15, 23.89 and 21.67 (mg/g) for RH, PAN/RH, PPY/RH and Na-alginate/RH, respectively. The Langmuir isotherm and pseudo-first-order kinetics models aptly described the adsorption process onto the composite material. The surface morphology and functional groups involved in the biocomposite formation were examined through scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) techniques. These analyses confirmed that PPy, PAN, and Na-alginate composites with RH biomass exhibit high effectiveness in naphthalene removal, showcasing their potential application in the remediation of naphthalene from effluents.