Synergistic adsorption and advanced oxidation activated by persulfate for degradation of tetracycline hydrochloride using iron-modified spent bleaching earth carbon

At present, tetracycline hydrochloride (TCH) is a widely used antibiotic, and is often detected in water, posing a serious harm to human and ecological health. In this study, spent bleaching earth (SBE) was pyrolyzed to obtain spent bleaching earth carbon (SBE@C) and the nano Fe⁰/SBE@C prepared after zero-valent iron loading was adopted to remove TCH in water for the first time. The combination of nano Fe⁰/SBE@C and PS, the strong adsorption of SBE@C coupled with the oxidation of free radicals could achieve TCH efficient removal. The effects of nano Fe⁰ load, nano Fe⁰/SBE@C dosage, solution initial pH, and PS/TCH molar ratio on TCH removal efficiency in nano Fe⁰/SBE@C?+?PS system were studied. The results indicate that the optimal reaction conditions are 5% nano Fe⁰ load, 0.2 g/L nano Fe⁰/SBE@C dosage, initial pH of 3, PS/TCH molar ratio of 100:1. Under these conditions, TCH removal efficiency could reach 91%. Meanwhile, response surface methodology (RSM) was applied to predict optimal value of reaction conditions. The removal efficiency corresponding to the predicted optimal conditions was consistent with the actual removal efficiency obtained from the experiment. Moreover, six reaction systems were tested, and TCH removal efficiency in the SBE@C?+?PS system was 22.6%. When nano Fe⁰ was loaded on SBE@C, TCH removal efficiency in Fe⁰/SBE@C?+?PS system increased to 78.2%, in which TCH was first adsorbed on the surface of nano Fe⁰/SBE@C, and then was degraded by the oxidation of SO₄^?? and ?OH. Totally, the nano Fe⁰/SBE@C?+?PS system displayed excellent TCH removal efficiency, good stability and reusability, exhibiting a promise toward TCH removal.