Biosorption of methylene blue from wastewater using green olive stone-based biocomposites incorporating Bacillus sp. and Pleurotus eryngii : Kinetic and isotherm analyses

In this study, two different biocomposites (Bsp–GOS and Pe–GOS) were created by immobilizing Green Olive Stone with Bacillus sp. and Pleurotus eryngii . The removal of methylene blue (MB) from aqueous solutions was investigated using these materials. The structural and surface properties of the biocomposites were characterized by FTIR, SEM, and EDX analyses. FTIR results showed that hydroxyl, carbonyl, and ether groups played an active role in the biosorption mechanism; SEM–EDX analyses showed porous structure and morphological changes occurring on the surface. Experimentally, the effects of parameters such as pH, contact time, initial dye concentration, and biocomposite amount on biosorption efficiency were evaluated. The optimum pH of Bsp–GOS and Pe–GOS biocomposites was determined as 7.0 and 6.0, respectively. The contact time was determined as 60 minutes for both biocomposites. Isotherm analyses showed that Bsp–GOS fit the Langmuir model better, while Pe–GOS fit the Freundlich model better. Kinetic data showed a fit to a pseudosecond-order model for both systems. In conclusion, the developed biocomposites were evaluated as biosorbents prepared from agricultural waste.