Application Of Short-pulse Under-water Bubble Discharge In Degradation Of Pharmaceutical Residues Carbamazepine

As people's emphasis on the safety of drinking water and the improvement of detection level on trace pollutants,trace organic pollutants in water have gradually attracted people's attention.Pharmaceutical residues are potential dangers to the natural environment and human health because of its sustainability and recalcitrant properties in water.In this paper,Carbamazepine(CBZ),a typical pharmaceutical residue,was used as the target pollutant to study the degradation process of the CBZ in the aqueous solution and the soil by the short-pulse under-water bubble discharge.Through the short-pulse under-water bubble discharge treating CBZ solution,studied the effects of gas species,gas flow rate,peak voltage,discharge frequency,electrode gap distance,initial concentration of CBZ on degradation rate of CBZ.For 1 mg/L CBZ solution,the oxygen bubble discharge can completely degrade the target pollutant by 30 s,and the oxygen bubble discharge displays higher degradation efficiency than that of argon bubble discharge.The energy efficiencies of oxygen bubble discharge at different frequencies and different initial CBZ concentrations were calculated.A high energy efficiency of 6.35 g/kWh is able to achieve at low pulse frequency 10 Hz and relative high CBZ concentration of 50 mg/L.The lower the frequency,the higher the initial concentration,is able to achieve the higher energy efficiency.TOC tests show that under the same discharge conditions,the proportion of mineralization in degradation of CBZ by argon bubble discharge is far higher than that of oxygen bubble discharge.CBZ solution was treated by ozone alone,and it is found that the ozone contributes about 40%-60% in the degradation of CBZ by oxygen bubble discharge.Solution samples before and after discharge were analyzed by the ultra performance liquid chromatography-mass spectrometry,it is found that degrading CBZ mainly produces acridine-9-carbaldehyde;carbamazepine-10,11-epoxide;1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one;1-(2-benzaldehyde)-(1H,3H)-quinazoline-2,4-one;1-(2-benzoic acid)-(1H,3H)-quinazoline-2,4-one five kinds of transformation products.The values of reaction rate constant for ozone with transformation products of CBZ degradation is small,so oxygen bubbles discharge is good at degrading carbamazepine rather than the transformation products;argon bubbles discharge can produce more active radicals hydroxyl,there is still a high efficiency of degrading transformation products of CBZ.In this paper,distilled water and polluted soil were mixed in different proportions,and the mixed suspension was treated by the short-pulse under-water bubble discharge.The experimental results show that the smaller water to soil ratio,that is,the more soil,lead to the discharge weakened,will reduce the degradation rate of CBZ.In this paper,when the water to soil ratio is 15,the mass of degradation of CBZ is maximum.Through the mode of elution-discharge,treating the solution after elution,can greatly improve the discharge intensity and the degradation rate of CBZ.Plenty of ferrous ions are contained in soil,the ferrous ion and the hydrogen peroxide produced by the discharge have Fenton reaction,which is beneficial to the degradation of CBZ.