Removal of Sulfamethazine by Corn Biochars from Aqueous Solution: Sorption Mechanisms and Efficiency

Abstract

Sorption mechanisms of sulfamethazine (SMT) in different pH solutions are complicated. It has not been sufficiently investigated to enhance removal of SMT from alkalescent aqueous solution. In this study, sorption isotherms and kinetics of SMT by corn biochars pyrolyzed at 300°C and 600°C (300C, 600C) under diverse pH conditions were compared. In order to improve the sorption efficiency of SMT from alkalescent aqueous solution, the biochar 300C was modified by acid or base. Different mathematic models were used to describe sorption driving force and sorption process. Results showed that the biochar 300C possessed more amorphous organic carbon and polar functional groups, which led to a higher sorption capacity than biochar 600C. The sorption rate of biochar 300C was greater than 600C under diverse pH as the physisorption of 300C outweighed 600C. The SMT presented stronger hydrophobicity at pH 5 and higher electrostatic repulsion at pH 1 or 8, which resulted in a higher combining capacity of SMT with both biochars at pH 5 than other pH values. In addition, the acid modified biochar had better removal effect on SMT than alkali at pH solution around 8. The research provides a theoretical basis for the removal of SMT from alkalescent aqueous solution.