Sulfamethazine adsorption using livestock manure-derived biochar: Significance of oxygen concentration during biochar generation

초록

This study investigated the effects of oxygen concentration (0.5-10 %) during biochar production on its characteristics and capacity for sulfamethazine adsorption. The biochar was produced from cattle manure, which was either pretreated with ZnCl2 or left untreated, and subsequently pyrolyzed at different temperatures. Increasing oxygen concentration during pyrolysis led to biochar oxidation, which reduced its carbon content and adsorption efficiency. Higher pyrolysis temperatures and lower oxygen concentrations enhanced the sulfamethazine removal efficiency, primarily due to the increased specific surface area. Biochar produced at 0.5 % oxygen concentration maintained over 90 % removal efficiency after at least four cycles of reuse, while biochar produced at higher oxygen concentrations exhibited significant efficiency loss upon reuse. Continuous-flow experiments revealed that flow rate, column height, and initial solute concentration significantly influenced breakthrough dynamics, with optimal adsorption observed at lower flow rates and increased column height. Experiments with the livestock wastewater demonstrated that the adsorption process was conformed to the Freundlich and Elovich model, indicating that adsorption occurred unevenly across heterogeneous sites of the biochar and was controlled by mass transport as a heterogeneous diffusion process. These findings underscore the significance of regulating oxygen levels during biochar generation to enhance its viability as adsorbent.

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