Comparison of deionized and tap water activated with an atmospheric pressure glow discharge

Abstract

Liquid-cathode discharge at atmospheric pressure has been excited by a direct current voltage above the surfaces of deionized and tap water. Gap voltage decreases with increasing discharge current, which suggests that the discharges above both the liquids belong to a normal glow regime. For a given discharge current, gap and power voltages of the discharge above deionized water are higher than those above tap water. The optical spectrum obtained from the water surface reveals that there are abundant active species related to oxygen, nitrogen, and water vapor, which leads to changes in the pH value, conductivity, and concentrations of NO3−, NO2−, and H2O2 in liquid. Therefore, these parameters are investigated in the two liquids as functions of discharge current and plasma activation time. For both of them, the results show that the pH value decreases, while conductivity increment and concentrations of NO3−, NO2−, and H2O2 increase with increasing discharge current or activation time. Compared to activated tap water, deionized water has a lower pH value, while higher conductivity increment and concentrations of NO3−, NO2−, and H2O2 are observed after the same activation time and discharge current. Finally, these parameters are compared for different salt types and salt concentrations after plasma activation.

The Effects of Plasma-Activated Water on Heavy Metals Accumulation in Water Spinach

“…The concentration of NO 3 − decreased in the order 20 min > 15 min > 10 min > 5 min > control. The increasing trend nitrate concentration with increasing treatment time was similar to results reported in some other studies [21,22]. The findings of Zhou et al [21] indicated that NO 2 − and NO 3 − are formed in water, with the constant rate following zero-order kinetics, indicating a direct effect of the plasma.…”

“…Meanwhile, they also reported that air microplasma treatment resulted in the highest concentration of nitrites and nitrates, followed by nitrogen plasma and oxygen plasma. Li et al [22] also mentioned that the concentrations of NO2 − , NO3 − , and H2O2 increased with increasing discharge current or activation time [22]. Figure 3 depicts the concentrations of NO2 − in PAW treated for different lengths of time in this study.…”

Generation of neutral pH high‐strength plasma‐activated water from a pin to water discharge and its bactericidal activity on multidrug‐resistant pathogens

“…The released $${{\rm{H}}}^{+}$$ leads to acidic pH in DM water. However, the bicarbonate ions present in the tap water consume the $${{\rm{H}}}^{+}$$ ions [ 23,27 ] generated (Equation ), resulting in buffering of water pH. The bicarbonate ions of the tap water provide initial buffering during the first few minutes of activation.…”

“…Activating demineralized (DM)/distilled (DI) water results in the acidic pH of the PAW. [12,14,20,[25][26][27]30,31] The PAW generated using the tap water remains in the neutral pH range, as shown in Table 1, due to the buffer action of naturally occurring bicarbonates in tap water [23,27,28] (discussed later in Section 3.1). However, their strength was not higher than DI/DM-activated PAW.…”

“…Acidic pH enhances the degradation rate of H 2 O 2 by $${\mathrm{NO}}_{2}^{-}$$ at pH < 3.5, [ 4 ] resulting in lowering the strength of PAW. Among P2W works, the maximum strength of PAW, that is, 238 mg/l, was achieved by Hoeben et al [ 25 ] Following this, Lu et al [ 26 ] and Li et al [ 27 ] reported a strength of 92 and 76 mg/l, respectively, and have not reported any bactericidal effect of the PAW. Schmidt et al [ 28 ] reported a maximum strength of 74 mg/l at neutral pH and showed a 5 log CFU reduction of Staphylococcus aureus (common wound pathogen) and Escherichia coli (infection pathogen).…”