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 (q_t = 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 (q_e = 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/C_o 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.

RR2 dye adsorption to Hymenaea courbaril L. bark activated carbon associated with biofilm

This study addressed the removal performance of RR2 from aqueous solutions in adsorption columns experiments by comparing the potential of activated carbon alone (ACA) and microbially inoculated (MIAC), prepared from barks of a largely available tree in Brazilian Cerrado biome, Hymenaea courbaril L. or "Jatobá," presenting the kinetics, isotherms, breakthrough curves, and dissolved organic carbon removal. ACA presented strong interaction to RR2 dye, evidenced at the first 20 min when absorbance already attained 66.4%. The removal percentage gradually increased with time and the equilibrium occurred around 91.7% within 120 min. Langmuir model best fitted the isotherm data, indicating a maximum adsorption capacity of 4.068 mg g^-1 for the amount of 0.5 g of adsorbent. The Langmuir's model parameters K_L, R_L, and R² corresponded to 0.0234 L mg^-1, 0.4159, and 0.9663, respectively, indicating a favorable adsorption process (0 < R_L < 1). The experiments in adsorption columns revealed maximum adsorption capacities of 14.38 and 11.43 mg g^-1 for MIAC and ACA, respectively, where the microbial activity favorably retarded the adsorption breakpoint in approximately 20 min and enhanced the RR2 consumption in 25.8%. Effectiveness of DOC removal attained above 90% for both ACA and MIAC, reducing the content from 86.1 to 7.84 mg L^-1 and 4.82 mg L^-1, respectively.