Ball milling boosted magnetic cotton husk-derived biochar adsorptive removal of oxytetracycline and ciprofloxacin from water
Chen Chen, Fengxia Yang, Yongfei Ma, Lihong Dai, Zulin Zhang, Haixin Guo, Yongzhen Ding
Abstract
Abstract Oxytetracycline (OTC) and ciprofloxacin (CIP) contamination have caused serious risks to human health, and modified biochar is considered as a potential adsorbent for their removal. The typical agricultural waste of cotton husk was used as the feedstock, then was combined with γ-Fe 2 O 3 and ball milling to innovatively synthesize nano zero-valent iron (nZVI) supporting magnetic cotton hush-derived biochar (Fe 2 O 3 @BMBC) by reductive calcination. Fe 2 O 3 @BMBC performed excellent adsorption performance with a maximum adsorption capacity for OTC (266.7 mg · g −1 ) and CIP (83.36 mg · g −1 ), and its adsorption capacity was 1.6 and 2.3 times that of cotton husk biochar (BC). Characterization analysis showed that Fe 2 O 3 @BMBC contained abundant oxygenated functional groups (e.g., -OH, C = O and Fe–O) and its surface was covered by diverse iron oxides. The high magnetization sensitivity of Fe 2 O 3 @BMBC guaranteed that it was easily to be separated by a magnet. Oxygenated functional groups (e.g., -OH, C = O and Fe–O) participated in the adsorption process, and solution pH significantly affected the adsorption behaviour, and pseudo-second-order model and Freundlich model better fitting the kinetics and isotherms data. These results confirmed that π-π conjugation, H-bonding, Fe–O complexation and electrostatic interactions contributed to the greater adsorption capacity of Fe 2 O 3 @BMBC. Ethanol + ultrasound could efficiently regenerate the used Fe 2 O 3 @BMBC and maintain its sustainable adsorption performance for OTC and CIP. Additionally, Fe 2 O 3 @BMBC performed a good environmental security in a wide pH range (from 3 to 11) in view of the low leaching risk of Fe. Graphical Abstract