A novel, simply prepared biosorbent for the removal of cationic dye: characterization, isotherm, kinetic and thermodynamic study

This study utilized raw (MTC) and NaOH-modified magnolia tree cone powder (MMTC) as adsorbents for the first time in the literature. The adsorbents were characterized through SEM, BET, FTIR, XRD, pHpzc analyses and contact angle measurements. The findings offered valuable insights into the increased removal efficiencies observed after modification. The study investigated the effects of pH, adsorbent dosage, contact time, initial dye concentration (Astrazon Red 5BL), and temperature on dye removal efficiency. Optimal dye removal (97.5% (+/- 1.5%)) was achieved at pH 8, 25 degrees C, 0.7 g/100 mL adsorbent dosage, and 30 min contact time. Pseudo-first, pseudo-second order and intraparticle diffusion kinetic models applied. Nonlinear kinetic models strongly fit the pseudo-second-order model (R2 = 0.99, RMSE 0.12). The nonlinear fit of the Freundlich isotherm effectively described the equilibrium data (R2 = 0.98, RMSE 4.73). Thermodynamic calculations indicated that the adsorption process is both spontaneous and endothermic. Experiments were performed to assess the effectiveness of MMTC in adsorbing cationic dyes from dye mixtures and in the presence of various salts under optimal conditions. The results show that MMTC has a higher affinity for cationic dyes compared to anionic (40.0% (+/- 0.6%)) and nonionic dyes (47.0% (+/- 0.8%)), and the presence of different salts in the solution didn't significantly affect dye adsorption. MMTC maintained a removal efficiency of over 88.0% (+/- 0.9%) even after ten regeneration cycles. The adsorbent obtained is applicable in wastewater treatment and environmental remediation, providing a significant advantage over traditional adsorbents as a new, sustainable, and environmentally friendly material in the field.