The Investigation Of Product Characteristics And Inactivation Application Of Needle-to-Water Plasma Activated Water Under Different Powers

Needle-to-plate discharge is a classical type to generate plasma.It is widely investigated by researchers for its abundant chemical produtcs,high energy efficiency,excellent discharge uniformity and easy to be array.Especially when the aqueous solution acts as the ground-electrode,the plasma activated water?PAW?is produced by the discharge.PAW is widely applied in biology,medicine and food industry for its outstanding inactivation and water treament effects.For the sake of exploring the product and inactivation characteristics of PAW in different power supplies,discharge parameters and gas flow conditions,we have designed a multi-needle-to-water discharge system.In this experiment,High voltage DC,AC and pulse power supplies are applied as the excitation of the device,respectively.The product characteristics under different parameter conditions are investigated.Oscilloscope and high-voltage probe are applied to record the waveforms of the voltage and current.Ultraviolet and visible spectrophotometer is applied to text the product concentrations in PAW.And the microscope is applied to observe the morphology of penicillium.Firstly,under DC needle-to-water discharge,we apply 1 kV as the voltage step to control the transformation of the discharge modes.Mass flowmeter and gas-washing bottle can be used to vary the gas flow rate and gas-phase products absorbing modes.The product concentrations and germination inhibition rate of penicillium are detected under different discharge modes and gas conditions.Secondly,the products characteristics and inactivation mechanism are investigated in AC needle-to-water discharge.Unbuffered aqueous solution and PBS solution are applied as discharge liquid,respectively.The results show that H₂O₂ react with NO₂^-in acid solution to generate ONOO^-.And the efficient inactivation of PAW is attributed to the generation of ONOO^-and its reaction system.Finally,in pulse needle discharge,we investigate the influence of electrical parameters such as pulse width,frequency and peak voltage and gas parameters such as flow rate and gas washing modes.The experimental results show that the inactivation efficiency improve with the increase of pulse width,frequency and peak voltage.Moreover,when the gas flow rate is above 150L/h,the H₂O₂ and NO₂^-can be seperated in discharge chamber and gas washing bottle,respectively.And the re-mixture of the above two PAW obtains better inactivation effect.When H₂O₂ is excessive,the inactivation effect of the mixture is better.The germination inhibition rate is 82.3%when the molar ratio of H₂O₂ and NO₂^-is 3:1.In order to verift the advantage of PAW,we prepare the mixture of HNO₃,HNO₂ and H₂O₂ of the same concentration of PAW and investigate its inactivation efficiency.and it is proved to be less effective than PAW.