## 4 Conclusions  
This study investigates the use of Plasma-Activated Water (PAW) for nitrate fertilizer production without the addition of external nitrate ions. The dielectric properties of plasma-treated water were analyzed and compared to untreated water (RO Water). The results show that plasma treatment for 3 h at a flow rate of 0.5 L/min achieved a dielectric constant (\(\epsilon^{\prime}\)) of 79.79 \(\pm\) 0.41%, which is close to nitrate-mixed water (NO\({}_{3}\) + RO 10g) with a \(\epsilon^{\prime}\) of 82.55 \(\pm\) 0.58% at a frequency of 0.2 GHz. Moreover, plasma treatment reduced energy loss, as the dielectric loss factor (\(\epsilon^{\prime\prime}\)) of PAW after 1 h of treatment was 7.03 \(\pm\) 0.11%, decreasing to 5.64 \(\pm\) 0.10% after 3 h, which is lower than that of nitrate-mixed water at 9.19 \(\pm\) 0.28%. The study further reveals that a longer treatment duration enhances nitrate production efficiency, while a lower flow rate (0.5 L/min) improves energy storage and reduces energy loss more effectively compared to higher flow rates, such as 2.0 L/min,  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ref.** & **Type** & **Power** & **Nitrate** \\  & & & **Concentration (ppm)** \\ \hline
[1] & Plasma Electrolysis & 700 W & 2213.5 \\ \hline
[2] & Continuous Flow Liquid-Phase & & \\  & Plasma Discharge (CFLPPD) & 300 W & 73–136.2 \\ \hline
[3] & Plasma-Activated Water (PAW) & 125 W & 2.9–3.8 \\ \hline
[49] & Plasma-Activated Water (PAW) & 24 kV & 30–40 \\ \hline This work & Plasma-Activated Water (PAW) & 100 W & 235.2 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of nitrate concentration and energy consumption in this study with previous research.  
where \(\epsilon^{\prime}\) decreases and \(\epsilon^{\prime\prime}\) increases. The PAW process at a flow rate of 0.5 L/min and a 3 h treatment period produced a nitrate concentration of 235.2 ppm using only 100 W of power, which is more energy-efficient than traditional methods like electrolysis that require significantly more energy. Despite not adding any chemicals, plasma treatment generated nitrate concentrations comparable to direct nitrate mixing, making PAW a promising and sustainable technology for nitrate fertilizer production. It reduces environmental impacts while enhancing energy efficiency.  
Conceptualization, J.P., S.S. (Samroeng Santalunai), W.C., S.R., P.J., C.T., T.T., N.S. and S.S. ([PERSON]); methodology, J.P., S.S. ([PERSON]), C.T., N.S. and S.S. ([PERSON]); validation, J.P., S.S. ([PERSON]), W.C., S.R., P.J., C.T., N.S. and S.S. ([PERSON]); formal analysis, J.P., S.S. ([PERSON]), W.C., S.R., C.T., N.S. and S.S. ([PERSON]); investigation, J.P., S.S. ([PERSON]), C.T., N.S. and S.S. ([PERSON]); data curation, J.P., S.S. ([PERSON]), W.C., S.R., N.S. and S.S. ([PERSON]); writing--original draft preparation, J.P., S.S. ([PERSON]), W.C., N.S. and S.S. ([PERSON]); writing--review and editing, J.P., S.S. ([PERSON]), C.T., N.S. and S.S. ([PERSON]); visualization, J.P., S.S. ([PERSON]), W.C., S.R., N.S. and S.S. ([PERSON]); supervision, C.T., N.S. and S.S. ([PERSON]); project administration, C.T., N.S. and S.S. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
This research was funded by Suranaree University of Technology (SUT), Thailand Science Research and Innovation (TSRI), and National Science Research and Innovation Fund (NSRF) (NRIS no. 179268).  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
This research was made possible through the support provided by Suranaree University of Technology, which generously provided research facilities and measuring equipment.  
The authors declare no conflicts of interest.