Production and Characterization of Different Sodium Alginate Biospheres with Activated Carbon and Arthrospira platensis: A Novel Adsorbent for Removing Textile Dyes

Activated carbon is known to be an effective adsorbent for textile dye removal. However, the limited alternatives of adsorbent materials have resulted in reliance on activated carbon, preventing the exploration of potentially cheaper and more effective alternatives. Thus, this work aimed to immobilize activated carbon and the Microcoleaceae (Arthrospira platensis) in cross-linked alginate biospheres (designated SAAC and SAM, respectively), producing novel materials for dye adsorption. The biospheres were characterized through FT-IR and SEM analyses. The adsorption experiments were also conducted to analyze the kinetics, isotherm, and thermodynamics. Kinetic and isotherm studies indicated that adsorption across all materials occurs through physisorption, reaching adsorption equilibrium in 120 min. The qe values of all biospheres were ∼3.00 µg mg−1, with the alginate biosphere without any immobilized agent (SAB) presenting the highest qe value of 3.450 µg mg−1. Thermodynamic analysis revealed that adsorption was an exothermic process for all biospheres. SAB showed a ΔS° of −0.123 kJ mol−1 K−1 and ΔH° of −31.822 kJ mol−1, together with the negative values of ΔG°, further confirming that the adsorption process is favorable and spontaneous, with the optimal temperature being 20 °C. Overall, it was concluded that the SAB are the most effective adsorbent for textile dye adsorption, showing superior efficiency compared to SAAC and SAM.