Study On Tetracycline Degradation In Aqueous Solution By Electro-assisted Bornite Activited Persulfate

A naturally occurring ore bornite(NBO)was used as a high-efficient peroxodisulfate(PS)activator for degradation of tetracycline hydrochloride(TC)that on behalf of typical antibiotics simulated the recalcitrant contaminants degradation experiments.This paper explored the feasibility of this method and the effect of different experimental conditions including ore dosages,persulfate concentration,pH and inorganic ions on the removal of tetracycline.The NBO elemental composition,valence of chemical elements,crystal morphology,free radical generation during the reaction,intermediate products were characterized and analyzed by modern techniques,X-ray fluorescence spectroscopy(XRF),X-ray electron spectroscopy(XPS),X-ray diffractometer(XRD),electron spin resonance(ESR),Ultra-high-resolution electro-spray time of flight mass spectrometry(UHS-ESI-TOF/MS).The degradation mechanism was analyzed and the possible decay way was inferred from the intermediate products.The major research contents and conclusions are as follows:(1)Respectively,4%,10.2%and 81.6%tetracycline were degraded from solution be oxidized by PS,BNO,PS and NBO.Using inductively coupled plasma mass spectrometry,the leachate concentrations of iron and copper from reaction system were 1.0 mg/L and 57.1 mg/L.The removal rate of TC is higher in the only iron ions activation persulfate system than copper ions activation.Experimental results of the iron ions and NBO,copper ions and NBO co-activation persulfate for TC decomposition show that it is irons rather than copper ions to play an important catalytic action.The detection concentration of different valences iron ions in solution are higher ferrous ion but lower ferric ion,indicating that ferric ion was reduced by sulfur with different low-valence states.Moreover,the XRD and XPS characterization of before and after used NBO also show that iron and copper in the natural NBO participate in the activation of persulfate,the changes of sulfur content in different valence states act a role in the reduction of metals.(2)Tetracycline removal rate decrease with the methanol and tert-butanol as quenchers added into the reaction system,demonstrating the presence of free radical SO4·-,·OH in the solution.The degradation of TC was significantly inhibited using phenol and benzoquinone as quenchers,also indicating that free radical are present on the surface of the NBO and superoxide radicals(·O2-)are present in the solution.Electron spin resonance(ESR)technique experiments has once again proven the existence of radicals(SO4·-,·OH and ·O2-).Based on the above conclusions,both the reaction mechanism and TC decay pathway were proposed based on the detected intermediate products.The trial outcome of different conditions,NBO dosage,PS concentration,pH and inorganic anions show that TC removal rate was 81.6%when NBO,PS and pH are 3.5 g/L,11.1 mM,3.6,respectively;the addition of inorganic ions(Cl-,CO32-)inhibited the decomposition of TC.NBO reuse test shows that it has good stability and can be reused.(3)Experiments on electron-assisted NBO activation persulfate for TC degradation were done:The removal rates of TC reach 94.2%,92.7%,respectively,when the anode are ruthenium-iridium and platinum mesh electrode,cathode corresponds to the titanium mesh.Four-factor three-level of orthogonal experiments were used to explore the influence of different factors such as NBO dosages,pH,potassium persulfate and current density on the degradation of TC under the experimental conditions of ruthenium-iridium-titanium electrode.The results prove that the removal rate of TC will be higher under the conditions of current density,NB amounts,persulfate concentration and pH are 15 mA/cm2,3.5 g/L,11.1 mM,3 respectively.Inorganic ions(Cl-,NO3-,HCO3-,PO43-)have little negative effect on the experimental results.Quenching trials show that TC degradation was inhibited,indicating that active free radicals are presented during the reaction.