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..

The present study aimed to characterise some active phenolic compounds in the alcoholic extract of two types of local microalgae, Chlorella sorokiniana Shihira & R.W.Krauss and Coelastrella saipanensis N.Hanagata These compounds were detected using HPLC device. The results showed that there were four types of active phenolic compounds, which were Gallic acid, Catechine, Ferulic acid and Hydrobenzoic acid. The highest concentration of all these compounds  found in Coelastrella saipanensis. Concerning the compounds, the highest value was for Gallic acid and it was 45. 85 ppm, while the lowest value was for Hydrobenzoic acid and it was 14. 28 ppm in Chlorella sorokiniana. It is that these compounds have vital activity in inhibiting different types of pathogenic bacteria and fungi as shown in many previous studies. From this study, we conclude the ability to produce these active compounds from both algae under natural conditions of growth.