Progress 07/01/20 to 06/30/24
Outputs
Target Audience:Research institutions and companies engaged in fertilizer research and production; Researchers in nonthermal plasma technology and nitrogen fixation;Nationally and internationally professional communities of fertilizer and soil health Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?One graduate student hasbeen hired and one other undergraduate student have been trained and involved to conduct the project and related research work. How have the results been disseminated to communities of interest?Journal articles and conference presentations/papers What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Mechanism ofammonia oxidation by liquid-phase plasma Nitrogen fixation to ammoniawas not successfully achieved using our liquid-phase plasma process, the ammonia oxidation instead was accomplished with very encouraging results. As reported in the last year's results,98.91% of NH3- N could be removed with a N2 selectivity of 92.91% in a one-hour treatment. Our research thenwasfocused on elucidating the mechanism forliquid phase plasma discharge to accelerate the ammonia oxidation reaction.First,free electrons gain energy from the electric field generated between the discharge and ground electrodes, resulting in high-energy electrons. These high-energy electrons can interact with oxygen, water molecules, and other ionic compounds in the aqueous phase to initiate various physical and chemical reactions. These processes may generate shock waves, reactive chemical species such as •OH, ?O, ?H, H2, O2, H2O2 and intense ultraviolet (UV) radiation which can be detected as a spectrum of emitted light photons by optical emission spectroscopy (OES). This spectrum of plasma-emitted radiation is grated, and the intensity is measured as a function of the wavelength. The spectra obtained in this study were analyzed using the National Institute of Standards and Technology atomic spectra databaseto identify the various active chemical species present in the reactor during operation.The relative intensity of the optical emission spectra observed in our CLPPD system from oxygen gas (flow rate = 2.5 L/min) at different power input levels (300 W and 225 W, respectively). The magnitude of the emission intensity lines provides a qualitative indicator of chemical species concentration in the optical emission. The results showed that the relative intensity of OES was strongly influenced by the magnitude of the discharge voltage. For example, an increase in power input from 225W (Vrms = 9.2 kV, Irms = 9.08 mA) to 300W (Vrms = 10.4 kV, Irms = 11.2 mA) resulted in a significant increase in the density/intensity of the transition lines of all active radicals and ionic species. This observation could be ascribed to the fact that stronger electric fields are produced when the power is increased, and as a result, collisions of high-energy electron with oxygen molecules accelerates the generation of active radicals through ionization, resulting in more light emissions. The discharge produced a significant UV radiation that was clearly visible to the naked eye and was dominated by atomic oxygen lines at 777.04 and 844.14 nm, which correspond to atomic transition 3p5P-3s5S and 3p3P-3s3S, respectively. These transitions arise from the decay of various excited states of oxygen atoms. In addition, molecular bands corresponding to transitions in the first negative system of the ?O2+ ions (b4Σg−- a4Πu), as well as hydrogen atoms, (3s→2p), were found at 559.6 and 659 nm, respectively. The ?OH emission from the electronic transition of A2Σ+ → X2Π with a band-head at 310.2 nm was also visible for the oxygen plasma discharge. These excited states can be generated due to both energetic electron impact excitation of oxygen atoms and energetic electron impact dissociation or Penning ionization of O2, NH3, ?OH, H2O2, and H2O molecules. The emission spectra obtained from this study are consistent with the results from other studies conducted by different research groups. ?O2+ and ?OH molecules are the most important reactive species that are frequently generated by the plasma treatment of aqueous solutions. They can oxidize most organic and inorganic compounds they come in contact with and are the primary source of hydrogen peroxide in plasma systems. During plasma treatment, NH3-N is mainly oxidized to NO3-, NO2-, and nitrogen gas, which are inactive. Based on data from the OES, theconceptual reaction pathways for NH3-N removal by the CLPD system are proposed.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2024
Citation:
D. Mohotti, MM. Hossain, R. Ndeddy Aka, A. Mukhtar, N. Holloway, *S. Wu. 2024. Evaluating a green liquid phase plasma discharge process and working mechanism for remediating cobalt contamination in water. Separation and Purification Technology, 354(3):128940. https://doi.org/10.1016/j.seppur.2024.128940.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
D. Mohotti, MM. Hossain, Y. Yuan, R. Robi, S. Wu. Evaluating a Green Liquid Phase Plasma Discharge Process and The Mechanism for Remediating Cobalt Contamination in Water. University of Idaho Institute for Health in the Human Ecosystem Annual Research Symposium, April 8, 2024.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Mohotti, D., MM. Hossain, R. Ndeddy Aka, A. Mukhtar, *S. Wu. Efficient Cobalt Removal and Synthesis of Cobalt Oxide Particles from Wastewater by A Continuous Liquid Phase Plasma Discharge Process, ACS Fall 2024 Conference, Denver, CO. August 18-22, 2024.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
T. Booker, MM. Hossain, Y. Yuan, S. Asghar, S. Wu. Investigating Early Growth Characteristics of Nonthermal Plasma Treated Wheat Seeds. University of Idaho Institute for Health in the Human Ecosystem Annual Research Symposium, April 8, 2024.
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Progress 07/01/22 to 06/30/23
Outputs
Target Audience: Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? One graduate student and one undergraduate student have been hired and one other undergraduate student have been trained and involved to conduct the project and related research work. How have the results been disseminated to communities of interest? What do you plan to do during the next reporting period to accomplish the goals?Nitrogen fixation to produce ammonia is not yet achievedwith only water and air or water with nitrogen gas by the CLPD process. Our plan for the next period will be to test if a hybrid of plasma with a catalyst is able to make the reaction of synthesis of ammonia from air (or nitrogen) and water as we have achieved the opposite reaction very successfully.
Impacts
What was accomplished under these goals?
To understand the effect of plasma assisted reactions on nitrogen cycle, our novel continuous liquid plasma process (CLPD) was evaluated to remove and convert NH3- N from synthetic wastewater, which is usually very hard to achieve by other chemical/physical processes. The Box-Behnken experimental design was used to optimize the main process parameters, including the initial NH3- N concentration (50-200 mg/L), power input (150-300 W), and gas-flow rate (1.5-2.5 L/min), for efficient NH3- N removal from wastewater. The gas-flow rate and power input were found to be significant factors affecting the removal efficiency of NH3- N, whereas the initial concentration of NH3- N played a vital role in determining the energy efficiency of the process. Under the optimal conditions of an initial NH3- N concen- tration of 200 mg/L, applied power of 223 W, and gas-flow rate of 2.4 L/min, 98.91% of NH3- N could be removed with a N2 selectivity of 92.91%, and the corresponding energy efficiency was 0.527 g/kWh after 2 hrs of treatment. A small fraction of undesirable NO−3 -N (7.05 mg/L) and NO−2 -N (2.83 mg/L) were also produced. Kinetic modeling revealed that NH3- N degradation by the CLPD followed a pseudo-first-order reaction model, with a rate constant (k) of 0.03522 min− 1. Optical emission spectroscopy (OES) was used to gather information about the active chemical species produced during the plasma discharge. The obtained spectra revealed the presence of several highly oxidative radicals, including ?OH, ?O, and ?O+2 . These results demonstrate the potential of liquid phase plasma discharge as a highly efficient technology for removing ammonia from aqueous solutions.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Ndeddy Aka, RJ., S. Wu, #D. Mohotti, MA. Bashir, A. Nasir. 2022. Evaluation of a liquid-phase plasma discharge process for ammonia oxidation in wastewater: process optimization and kinetic modeling. Water Research, 224: 119107. https://doi.org/10.1016/j.watres.2022.119107.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Wu, S., B. Thapa, Yuan, Y., R. Ndeddy Aka, A. Nasir. 2022. Optimization of a green plasma process for nitrogen fixation in water. ASABE 115th Annual International Meeting. Paper#: 2200908. Houston, TX. July 17-20, 2022.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Booker, T., S. Wu, Y. Yuan. Evaluating a green nitrogen fertilizer produced by plasma discharge of air and water. University of Idaho Undergraduate Research Symposium, April 24, 2023.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Booker, T., S. Wu, Y. Yuan. Evaluating a green nitrogen fertilizer produced by plasma discharge of air and water. 2022 Idaho Conference on Undergraduate Research (ICUR). Online. July 20-21, 2022.
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Progress 07/01/21 to 06/30/22
Outputs
Target Audience: Research institutions and companies engaged in fertilizer research and production; Nationally and internationally professional communities of fertilizer and soil health Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? One graduate student and one undergraduate student have been hired and one other undergraduate studenthave been trained and involved to conduct the project and related research work How have the results been disseminated to communities of interest?Journal articles and conference presentations/papers What do you plan to do during the next reporting period to accomplish the goals?Our next reporting period is going to focus on further optimization of the plasma process for nitrogen fixation and ammonia removal.
Impacts
What was accomplished under these goals?
Factorial design is used to find out significant process factors for NOx production using NOx concentration and energy efficiency for nitrogen fixation as the responses. The summary of analysis of variance settled the model a second-order polynomial equation. The ANOVA analysis for NOx Model with F-value of 231.51 implies the model is significant at 95% confidence level. Applied power, water volume, and air flow rate had positive effects on NOx with power as a factor with the most significant positive effect while water flow rate was the only factor with a negative effect on NOx production. Water volume and air flow rate had a positive effect on N-efficiency with the volume being the most significant positive factor. And water flow rate is the only factor with a negative effect on N-efficiency. The response surface contour plot by a central composite designrevealed that the maximum production of NOx that can be achieved 284mg/Lat the center of the circle with2.2 standard liter per minutefor air flow rate and 310 W for appliedpower.Similar observation was made on effects of independent variables on N-efficiency. The maximum efficiency was achieved as 259.1mg/kWh when power is in the range of 245 W and air flow rate in the range of 2.25 standard liter per minute.
Publications
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Progress 07/01/20 to 06/30/21
Outputs
Target Audience: 1. Research institutions and companies engaged in fertilizer research and production 2. Ordinary citizens who are interested in green nitrogen fertilizer production technologies 3. Nationally and internationally professional communities of fertilizer and soil health Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?One graduatestudent and one undergraduate studenthavebeen hired and three otherundergraduate and graduate students havebeen trained and involved to conduct the project and related research work, which has been resulted in one peer-reviewed journal article and four conference paper/presentations. This project has provided opportunities forundergraduate and graduate students toprepare them for their career development in the academic and industrial comminities. How have the results been disseminated to communities of interest?The results have been disseminated as published peer-reviewed papers, conference papers, and conference and on-campus presentations. The results are also shared with the interested industry for potential collaboration for the scale-up and commercialization of the proposed technology. What do you plan to do during the next reporting period to accomplish the goals?In the next year, our work will be focused onevaluating and optimizing the liquid plasma reactor to determine the optimal operating conditions for efficient production of nitrogen fertilizer from air and water, in terms of process parameters including airflow rate, liquid flow rate, power, N2 and O2 ratio, as well as design parameters. The mechanism and reaction pathways of nitrogen fixation by CFLPPD will be determined.
Impacts
What was accomplished under these goals?
Technical feasibility of nitrate and nitrite production by the continuous flow liquid-phase plasma discharge and influence of operating factors Variations of NO2 and NO3 (NOx, ditto) produced from air and water by the continuous flow liquid-phase plasma discharge (CFLPPD) system have been studied, based on which the technical feasibility was confirmed, and a few comments can be made for the influence of operating factors. First, the production of NOx increased with increasing power usage under all tested airflow rates in a largely linear manner. This was expected because increasing power supply would normally provide more energy to the plasma system, thus leading to increased reaction rates and improved product yields or treatment effects. Second, it was interesting to note that the CFLPPD system produced more NO3 than NO2 (the amount of the former was greater than about 2 times the latter). When the nitrogen gas in the air was oxidized by the strong oxidizing species, such as the hydroxyl radicals and H2O2 generated in large quantities by the plasma discharge, nitrite was expected to be formed in the first step of N2 oxidation. However, the existence of nitrite was transient, and as soon as it was generated, it would be immediately subjected to oxidation to nitrate by the abundant oxidizing species provided by the plasma discharge. It was reported that when O2 was copiously present, the formation of NO3 in water could proceed at a significantly higher rate. Since crops are in favor of nitrate as nitrogen fertilizer and nitrate is also considered a nutrient to improve soil quality, it is desirable to produce more nitrate than nitrite in the final effluent. That said, since nitrite can be further oxidized in the soil by soil microorganisms, a small amount of nitrite in the liquid should not pose a concern when the plasma-treated liquid is used as fertilizer. As a matter of fact, the nitrite to nitrate transformation in soils could take place without involving microorganisms. An early study revealed that when reactive manganese oxides were present, nitrite could be oxidized to nitrate in the presence or absence of atmospheric O2, which explained the seldom accumulation of nitrite in soils even when nitrifying bacterial numbers were low and the conditions for their growth were unfavorable. Third, the product yields of NOx apparently increased with the increase in air flow rate. And this increase showed a trend of continuing beyond the highest air flow rate examined in this study (2.0 L/min) because no slowdown or turning point was observed. This implies that the current experimental settings in terms of power and treatment times may be able to accommodate higher airflow rates than 2.0 L/min to produce more NOx. Further studies should be planned on increasing the airflow rate without increasing the power and treatment times to ascertain the maximal NOx yields for the CFLPPD system. Finally, it seemed that treatment times played a profound role in producing the NOx species by the CFLPPD system. As shown in Figure 2, as the treatment time increased from 20 min to 60 min, almost all treatments showed significant increases in NOx yields, regardless of airflow rate and power applied. The highest yields of NO3 and NO2 were observed for air flow rate at 2.0 L/min and power consumption at 300 W, which was 49.5, 75.8, and 97.5 mg/L for the former and 23.5, 35.0, and 38.7 mg/L for the latter under 20, 40, and 60 min treatments, respectively. However, the percent increases in yields were found to be reduced with the increases in treatment time. For instance, calculations of percent increases in yields using the same data showed that the NO3 yield increased by 53.13% and 28.63% corresponding to the treatment time increases from 20 to 40 min and from 40 to 60 min. This calculation can be performed on all the other experimental conditions with similar results achieved. It may therefore be concluded that increasing treatment time may not be as effective as increasing airflow rate with respect to increasing the NOx yields by the CFLPPD system examined in this study. Feasibility of nitrogen fixation to ammonium by CFLPPD As pure nitrogen gas was used as the gas reactant instead of air, it was expected that the product species in the solution will consist of ammonium ions besides nitrate and nitrite, based on the hypothesis that hydrogen ions and radicals from water ionization can react with nitrogen radicals by ionization of molecular nitrogen to produce ammonium. However, the actual results showed almost no ammonium ions in the treated solution from nitrogen gas and water, while the NOx ions are still dominant. In CFLPPD, the plasma discharge ionizes water to produce a high concentration of hydroxyl radical which possesses the highest oxidation capability. The existence of ammonium ions can be transient, and as soon as it was generated, it would be immediately subjected to oxidation to nitrate by the abundant oxidizing species provided by the plasma discharge in water. The commonly reported information in the literature on nonthermal plasma discharge for ammonia synthesis is from N2 and H2 with the assistance of catalysts by gas-phase plasma discharge. Given the current knowledge and level of development thus far, such a system is expected to be complex and requires the availability of expensive H2 in addition to readily available N2, which is unrealistic for most farms and can even pose a safety hazard due to the on-site storage of H2. Furthermore, the use of catalysts and the ability to recycle them constitute another hurdle to on-farm applications of the NTP process for ammonia synthesis. Therefore, it is concluded that the CFLPPD system is more suitable and economical for nitrogen fixation to NOx as fertilizer products.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Wu, S., B. Thapa, C. Rivera, Y. Yuan. 2021. Nitrate and nitrite fertilizer production using a continuous flow liquid-phase plasma discharge process. Journal of Environmental Chemical Engineering, 9(2): 104761. https://doi.org/10.1016/j.jece.2020.104761.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Wu, S., B. Thapa, R. Ndeddy Aka, Y. Yuan, C. Rivera, 2021. Production of Liquid Nitrogen Fertilizer by Air Activated Plasma Discharge in Water. ASABE 114th Annual International Meeting. Paper#: 2100284. Online. July 11-14, 2021.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Booker, T., S. Wu, B. Thapa, R. Ndeddy Aka. 2021. Liquid-phase Plasma Discharge Process for Green Nitrogen Fixation. University of Idaho Undergraduate Research Symposium, April 26, 2021.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2020
Citation:
Wu, S., B. Thapa, C. Rivera, Y. Yuan. 2020. Liquid-Phase Plasma Discharge for Producing Green Nitrogen Fertilizer from Air and Water. Nutrient Cycling, Soil Health, and Food Safety Conference Online. October 27-28, 2020.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2020
Citation:
Wu, S., B. Thapa. 2020. Liquid-Phase Plasma Discharge for Producing Green Nitrogen Fertilizer from Air and Water. ASABE 113th Annual International Meeting. Paper#: 2000940. Online. July 12-15, 2020.
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