The biochar-supported iron-copper bimetallic composite activating oxygen system for simultaneous adsorption and degradation of tetracycline

An economical biochar-supported iron-copper bimetallic composite (BC-FeCu) was successfully prepared and used to remove tetracycline (TC) from water. The experiment results expressed that BC-FeCu exhibited higher removal (92.50%) than FeCu (67.30%) under the same condition (pH 4.50, TC concentration 10 mg/L, and catalyst dose 0.05 g/L). Moreover, the TC removal by BC-FeCu constantly increased with the pH value from 4.50 to 9.03. Desorption experiments showed that adsorption and degradation accounted for 26.09% and 73.91% of the total TC removal by BC-FeCu, respectively. N2 sparging experiments concluded that the degradation led by dissolved oxygen (DO) and the direct degradation by BC-FeCu accounted for 17.02% and 56.89% of the total TC removal, respectively. The existence of O2•−, •OH, 1O2 was testified by electron spin resonance (ESR) analysis. And O2•− was proved to be the dominating active substance for TC degradation by BC-FeCu through quenching experiments. It could be that the electron transferred from –COOH, –OH and Cu/Cu+ in BC-FeCu to O2 to form O2•−, thus realizing the activation of O2. Finally, three possible TC degradation ways were presented through the analysis of eight intermediates.