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[Display omitted] • Buoyant barium alginate bubble beads (BABB) boosted the growth of immobilized microalgae. • BABB reduced the leakage of microalgae by 80% over traditional calcium alginate beads (CAB). • BABB enabled rapid microalgal biomass separation and full freeze−drying in 3.5 h. • Three strategic BABB optimizations were introduced for further enhanced culture. • Optimized BABB in open raceway pond reactor achieved 0.609 mg/bead biomass in 7 days. Microalgae immobilization in alginate beads shows promise for biomass production and water pollution control. However, carrier instability and mass transfer limitations are challenges. This study introduces buoyant barium alginate bubble beads (BABB), which offer exceptional stability and enhance Chlorella vulgaris growth. In just 12 days, compared to traditional calcium alginate beads, BABB achieved a 20 % biomass increase while minimizing cell leakage and simplifying harvesting. BABB optimization involved co-immobilization with BG-11 medium, enrichment of CO 2 in internal bubbles, and the integration of Fe nanoparticles (FeNPs). In the open raceway pond reactor, these optimizations resulted in a 39 % increase in biomass over 7 days compared to the unoptimized setup in closed flasks. Furthermore, enhancements in pigment and organic matter production were observed, along with improved removal of ammonia nitrogen and phosphate. These results highlight the overall advantages of BABB for microalgae immobilization, offering a scientific foundation for their effective utilization. [ABSTRACT FROM AUTHOR]