Utilization of Spirulina algae powder for efficient removal of lubricating oil from aqueous media

Abstract

The potential of the Spirulina algae powder as a biosorbent for the adsorption of lubricating oil from freshwater was investigated. The impact of various contact times between the biosorbent and oil–water mixture was studied through different experiments. Under optimum conditions, a maximum removal efficiency of 32.69 % was achieved within 180 min, highlighting the gradual yet effective adsorption behavior of Spirulina algae powder over time. A high regression coefficient (R² = 0.9981) indicates that the experimental result closely matched pseudo-second order kinetics, suggesting a strong model fit and suggesting that the dominant mechanism was chemisorption, which is defined by strong interactions between oil molecules and mobile sites on the algae surface. FTIR analysis confirmed that oil adsorption onto Spirulina algae powder involves hydroxyl, carbonyl, amide, and polysaccharide groups through hydrogen bonding and van der Waals interactions, accompanied by surface chemical modifications. SEM images showed a transition from a porous to a smoother, compact structure with reduced pore population, indicating effective oil deposition. Contact angle measurements revealed a shift from 63.2° to 20.3°, reflecting increased surface polarity and enhanced hydrophilicity after adsorption. These results show that Spirulina algae powder effectively adsorbs lubricating oil from water through multiple interaction mechanisms, making it a promising bio-sorbent for oil removal.