The Study Of The Degradation Of Tetracycline Wastewater By Persulfate Activated By Bimetallic Catalysts

Recently,with the wide application of antibiotics,massive antibiotic residues have been remained in surface water,groundwater and other water sources,which leads to potential water pollution.If these pollutants cannot be removed effectively and timely,the water environment and resident's health in our country will be threated seriously.However,antibiotics like tetracycline are a class of refractory organic pollutants,they have characteristics,such as high stability and excellent solubility,and traditional methods,such as adsorption,membrane filtration and activated sludge treatment,cannot treat them efficiently.Compared with these traditional methods,novel persulfate based advanced oxidation processes can degrade these pollutants rapidly.At the same time,transition metal catalysts often have been utilized in these processes to activate persulfate,and they have several advantages,such as,simple operation,low costs and wide sources.The study was focused on the synthesis of novel,efficient and environmentally-friendly bimetallic catalysts for the efficient activation of persulfate and degradation of tetracycline.In this research,different kinds of Ni_xFe_3-xO₄ catalysts and Co₃O₄/CeO₂ composites were rapidly synthesized by a calcination method,and their physical and chemical characteristics were analyzed by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy,inductively coupled plasma atomic emission spectroscopy,et al.To prove the catalytic performances of Ni_xFe_3-xO₄ catalysts and Co₃O₄/CeO₂ composites,they were used to activate persulfate for the degradation of tetracycline wastewater.The catalytic performances of Ni_xFe_3-xO₄ catalysts and Co₃O₄/CeO₂composites were further analyzed by hydrogen temperature-programmed reduction and Ni dispersion.Then,the optimum experimental conditions,such as catalyst concentrations,persulfate concentrations,reaction pH,et al.were identified.To explore the reaction mechanisms,possible radical species which were generated in the reactions were analyzed by radical scavenger experiments and electron spin resonance spectroscopy.Finally,the stability,recyclability and actual application ability of catalysts were demonstrated by cyclic experiments and actual wastewater experiments.Experimental results indicated that Ni_0.6Fe_2.4O₄ catalyst was the optimum catalyst among different kinds of Ni_0.6Fe_2.4O₄ catalysts.Under the optimal experiment conditions,the degradation rate of tetracycline in this system was 86%.In the reaction process,persulfate was activated by Ni_0.6Fe_2.4O₄ catalyst,and sulfate radicals and hydroxyl radicals were generated to degrade tetracycline effectively.Meanwhile,redox reactions were existed between?Ni and?Fe active centers.In the reaction process,Fe³⁺ions can be reduced to Fe²⁺ions which can continue take part in the activation of persulfate.This promoted the recovery of the catalytic ability of Ni_0.6Fe_2.4O₄ catalyst in the persulfate activation process.Therefore,more radical species can be produced and the degradation efficiency can be improved.In addition,Co₃O₄/CeO₂-2 composite was also a good catalyst,?Co and?Ce were its active centers.And the redox reactions between Co/Ce can promote the recovery of the catalytic activity of Co₃O₄/CeO₂-2 composite.Under the optimum experimental conditions,the degradation rate of tetracycline was 79%.