CIPROFLOXACIN ADSORPTION ON SEWAGE SLUDGE DERIVED BIOCHAR

Ciprofloxacin (CIP) is a broad-spectrum fluoroquinolone antibacterial agent that is used to treat a variety of infections. CIP is commonly found in hospital and drug manufacturer waste, and thus has the potential to be released into the environment. One promising method of remediation involves the application of biochar, the solid material obtained from the pyrolysis of biomass under oxygen-free conditions. Biochar is a common adsorbent used in contaminant removal in aqueous systems due to its relatively high surface functional group density, complex internal structure, and large surface area. Preliminary studies have reported the utility in removing CIP from aqueous solution with biochar derived from sewage sludge, where research primarily focused on adding catalysts to biochar to improve CIP adsorption. Sewage sludge is also an ideal biomass because it is present at wastewater treatment plants that aim to remove CIP and other pharmaceuticals during the treatment process. There is currently a limited understanding of the optimal conditions for CIP removal via sewage sludge biochar because it contains many dissolved organic species and metals that may affect adsorption. This project considers sewage sludge biochar pyrolyzed at 550 ̊C and 700 ̊C, with the primary objectives to constrain biochar surface chemistry and determine how CIP complexes with the biochar during adsorption. We hypothesize that functional group interactions and organic partitioning will govern CIP adsorption given that biochar pyrolyzed at a higher temperature tend to have a more graphite-like structure and more basic functional groups. The biochar surface chemistry was characterized using FTIR and Raman spectroscopy, elemental analysis, and potentiometric titrations, while adsorption experiments using both isotherm and pH edge approaches were employed to determine the kinetics and equilibrium loadings of CIP adsorption. Results have shown that biochar pyrolyzed at 550 ̊C has a higher proton-active surface functional group density than at 700 ̊C, providing more sites for electrostatic interactions with charged aqueous species. This research will help develop an in-depth understanding of how a complex pharmaceutical compound, such as CIP, adsorbs to sewage sludge biochar, thus enabling maximum CIP removal from the environment.