Methylene Blue Removal in Airlift Bioreactor Packed with Coelastrella Biosorbent

Water contamination by Methylene Blue (MB) is a significant environmental challenge that requires cost-effective purification strategies. The green algae Coelastrella was used as an adsorbent inside the airlift bioreactor as an effective and inexpensive material. Experiments were conducted over a range of conditions, including initial MB concentration (3-30 mg/L), contact time (0-60 min), air flow rate (200-300 mL/min), algae dosage (0.1-2 g/L), and temperature (20-40 ˚C). Diverse characterization techniques were employed to comprehensively understand the process and its outcomes. These techniques include Energy Dispersive Spectroscopy (EDS), Fourier Transform-InfraRed (FT-IR) spectroscopy, UV-Visible (UV-Vis) spectrophotometry, and Scanning Electron Microscopy (SEM). Adsorption isotherms were analyzed in this study, with a focus on the Langmuir, Freundlich, and Temkin models. The Langmuir model had the highest (R² = 0.9998), indicating monolayer adsorption with a maximum adsorption capacity of 30 mg/g. Additionally, kinetic studies found the pseudo-second-order model to be the most accurate (R² = 0.9990). Under optimal conditions, the process achieved a high removal efficiency of 98.9%. Finally, mass transfer adsorption models were examined using three models. When these models were compared, the Liquid film diffusion model had the highest value (R² = 0.9736). These results suggest that algae biomass is an effective, green adsorbent for MB removal, presenting a viable alternative to conventional treatments..