Acetylsalicylic acid biosorption onto fungal-bacterial biofilm supported on activated carbons: an investigation via batch and fixed-bed experiments

This study reports on acetylsalicylic acid (ASA) biosorption onto fungal-bacterial biofilm supported on two types of activated carbons (one commercial type made of coconut fibers, CAC, and one other manufactured from fruit rinds of Hymenaea stigonocarpa Mart., HYAC, which after biofilm inoculation, they were named CAC-b and HYAC-b), via batch and fixed-bed experiments. These materials were characterized by BET Specific Surface Area and Scanning Electronic Microscopy (SEM). Biosorption onto HYAC-b was 57.2% higher than HYAC. Despite presenting the highest biosorption capacity over time (qₜ = 85.4 ± 0.82 mg g⁻¹), CAC-b had a lower increase in efficiency (32.4%) compared to CAC. Kinetic data from the biosorption experiments responded well to the pseudo-first-order model thus suggests the predominance of physisorption, while without biofilm presence, there was a better agreement with the pseudo-second-order model, suggesting chemisorption. The possible interaction mechanism of ASA to biofilm was attributed to ionic forces between the drug in anionic form and eventual presence of cationic by-products of the biologically active surface metabolism. Biosorption equilibrium data responded better to the Sips model and CAC-b presented the highest biosorption capacity (qₑ = 292.4 ± 2.01 mg g⁻¹). A combination of faster volumetric flow rates, higher inlet concentrations and shorter beds accelerated the breakthrough time of ASA biosorption in the fixed-bed experiments. These operational conditions affected C/Cₒ ratio in the following magnitude order: volumetric flow rate < inlet concentration < bed height. Breakthrough data responded better to the modified dose-response model compared to Thomas and Yoon-Nelson models.