Abstract
Sinusoidal alternating electro-Fenton (SAEF) is a new type of advanced electrochemical oxidation technology for the treatment of refractory organic wastewater. In this research, the removal performance and degradation mechanism of tetracycline (TC) were investigated, and the optimal operation parameters were determined. Scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) were used to characterize the morphology, elemental composition, crystal structure, function groups of sludge produced by SAEF. UV-visible spectroscopy (UV) and liquid chromatograph-mass spectrometer (LC-MS/MS) were employed to determine the concentration of organic matter, middle products of decomposed organics in the SAEF process, respectively. The results showed that the removal rates of TC, chemical oxygen demand (COD), electric energy consumption (EEC) and the amount of produced sludge (Ws) are 94.87%, 82.42%, 1.383 kWh⋅m−3 and 0.1833 kg⋅m−3 by SAEF, respectively, under the optimal conditions (pH = 3.0, conductivity (κ) = 1075 μS⋅cm−1, current density (j) = 0.694 mA⋅cm−2, initial c (TC) = 100 mg·dm−3, c [30%H2O2] = 1.17 cm3⋅dm−3, frequency (f) = 50 Hz, t = 120 min). Compared with pure direct electro-Fenton (DEF) or sinusoidal alternating current coagulation (SACC), SAEF was a highly effective method with low-cost for the treatment of TC wastewater. It was found that the conjugated structure of TC was destroyed to generate intermediate products, and then most of them was gradually mineralized into inorganic materials in the SAEF process.
Highlights
College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China; Department of Materials and Chemical Engineering, Hunan Institute of Technology, Hengyang 421008, China; Abstract: Sinusoidal alternating electro-Fenton (SAEF) is a new type of advanced electrochemical oxidation technology for the treatment of refractory organic wastewater
Because the TC was incompletely absorbed by the gut and decomposed, a great quantity of TC were discharged into the environment in the form of parent compounds, which are not easy to be biodegraded and accumulated in the environment, causing serious pollution to soil, surface water and groundwater
By comparing the treatment effects of SAEF and direct electro-Fenton (DEF), we find that the TC conversion efficiency of SAEF is 5.07% lower than that of DEF, the chemical oxygen demand (COD) removal rate of SAEF and DEF was nearly the same, but the sludges output and energy consumption of DEF were
Summary
Human’s increasingly frequent industrial and agricultural activities led to the production of a large amount of wastewater which contains pesticide residues, heavy metals, antibiotics and other pollutants. If it is discharged directly without any technologies, it results in great pollution to the ecological environment [1,2,3,4,5,6,7,8,9]. Antibiotics entering the environment will lead to chemical pollution, and induce microbial resistance, accelerate the diffusion and spread in the ecological environment These resistant microorganisms affect human health through the food chain [13,14]. How to efficiently remove TC from wastewater is a research hotspot in the field of water treatment
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