Source: PANI CLEAN INC submitted to
A FLUIDIZED BED PHOTOCATALYTIC REACTOR FOR NITRATE CONVERSION
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
ACTIVE
Funding Source
SMALL BUSINESS GRANT
Reporting Frequency
Annual
Accession No.
1031018
Grant No.
2023-39411-40586
Cumulative Award Amt.
$650,000.00
Proposal No.
2023-04029
Multistate No.
(N/A)
Project Start Date
Sep 1, 2023
Project End Date
Aug 31, 2025
Grant Year
2023
Program Code
[8.4]- Air, Water and Soils
Project Director
Lee, J.
Recipient Organization
PANI CLEAN INC
2350 FLINTSHIRE VIEW
CORALVILLE,IA 522413609
Performing Department
(N/A)
Non Technical Summary
Opportunity: Nitrate contamination has emerged as the most pervasive groundwater pollutant in North America, predominantly originating from agricultural activities and shifting nitrogen inputs to land surfaces. In the United States, over 7 million people rely on community water systems (CWS) with nitrate concentrations exceeding the maximum contaminant level (MCL). A rigorous, peer-reviewed study by the Environmental Working Group indicates that nitrate pollution in US drinking water may contribute to up to 12,500 cancer cases annually, with associated healthcare costs reaching $1.5 billion. Current nitrate treatment technologies for CWSs generate highly concentrated nitrate brine residuals, rendering them constrained by expensive brine disposal and management processes. Moreover, with over 35 million acres of sub-surface drained land in the US, no technology has yet established a significant market share for nitrate removal from agricultural drainage. Given the vast extent of nitrate contamination in community water systems and the increasing necessity to curtail nitrogen loads from tile drainage, the market potential for effective nitrate removal solutions is substantial.Project Objectives: The main technical objective of this project is to demonstrate and validate a highly efficient photocatalytic denitrification unit for the sustainable removal of nitrates from wastewater at a lower cost than incumbent technologies. In Phase I, the team successfully developed materials and systems that exhibit superior nitrate removal and conversion efficiencies, exceeding 95%. These materials demonstrated a photon-to-chemical conversion efficiency of 2.5% and remained stable for 100 hours of operation. In Phase II, the down-selected materials and systems from Phase I will undergo extensive optimization, testing, and operation in lab-scale and mini-scale prototypes, aiming to achieve photonic efficiencies greater than 10%, nitrate conversion efficiencies surpassing 95%, and stability exceeding 1000 hours. To accomplish these objectives, the team will refine the physical and chemical composition of the Phase I catalyst to enhance its photoactivity and stability. Furthermore, they will employ operando tools developed during Phase I to investigate the catalyst's selectivity and corrosion mechanisms and assess their performance in lab-scale and mini-pilot plant-scale reactors. A comprehensive techno-economic analysis will also be conducted to identify pathways for successful commercialization.Anticipated Results. By the end of Phase II, Pani Clean Inc. will have developed a small engineering-scale nitrate treatment unit that boasts nitrate conversion efficiencies and selectivity exceeding 95%, eliminates brine disposal issues, and costs less than $1.5 per 1000 gallons of treated water. This represents a two-to-five-fold decrease in cost compared to incumbent technologies.Potential Commercial Applications. The immediate addressable market for Pani Clean Inc.'s innovative nitrate treatment unit comprises the 1600+ community water systems (CWS) that have recently experienced violations of nitrate levels, primarily due to agricultural practices. In the near term, point-of-use (POU) nitrate treatment systems for individual residences with nitrate-contaminated private wells will be targeted, as well as treating nitrates at the edge-of-field practices.
Animal Health Component
40%
Research Effort Categories
Basic
25%
Applied
40%
Developmental
35%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
11102102020100%
Knowledge Area
111 - Conservation and Efficient Use of Water;

Subject Of Investigation
0210 - Water resources;

Field Of Science
2020 - Engineering;
Goals / Objectives
Major goals:The overall goalof this project is to demonstrate and validate a highly efficient photocatalytic denitrification unit for the sustainable removal of nitrates from wastewater at a lower cost than incumbent technologies. In Phase I, the team successfully developed materials and systems that exhibit superior nitrate removal and conversion efficiencies, exceeding 95%. These materials demonstrated a photon-to-chemical conversion efficiency of 2.5%. In Phase II, the down-selected materials and systems from Phase I will undergo extensive optimization, testing, and operation in lab-scale and mini-scale prototypes, aiming to achieve photonic efficiencies greater than 10%, nitrate conversion efficiencies surpassing 95%, and stability exceeding 1000 hours.Objectives:Objective 1. Develop fluidizable metal oxide (light absorber)/metal (catalyst) particulate photocatalytic heterostructures (PPHs)with varying chemical composition, oxygen vacancies, and catalyst loading and demonstrate improved performance for nitrate-to-nitrogen reduction compared to photocatalysts synthesized in Phase 1. The performance and durability of photocatalytic heterostructures synthesized in this objective will be tested in model nitrate-rich waters using a batch reactor. A deliverable at the end of this objective is to demonstrate specific nitrate conversion rates >300 mg-N/g-catalyst/hr. with >95% selectivity towards nitrogen formation in 0.1 L batch reactor using model nitrate-rich waters.Objective 2. Investigate the activity, selectivity, and durability of the PPHs using operando spectroscopy and optimize photocatalyst formulations based on the results. Using operando spectroscopy, we will examine reaction intermediates, reaction rates, and product branching ratio (N2 vs nitrite/ammonia) for nitrate reduction as a function of light intensity (5 W, 15 W, 30 W), initial nitrate concentrations (50 mg-NO3/l to 500 mg-NO3/l), and pH (6.5 - pH 8.5). The effect of chloride and other anions on the activity, selectivity, and durability will also be investigated.Objective 3. Construct a lab-scale (1 L) and mini pilot plant scale (10 L total photocatalytic reactor volume) fluidized photocatalytic reactor and test their nitrate conversion efficiency and durability for continuous removal and conversion of nitrates in different feed water sources using the best-in-class catalysts identified from Objectives 1 and 2. We will design and construct a lab and mini pilot-scale cylindrical fluidized bed reactors and benchmark best-in-class PPHs from Objective 1 and 2 for nitrate conversion and hypochlorite production in fluidized bed reactors for different nitrate feed concentrations (50 mg-NO3/l to 1000 mg-NO3/l), water composition (e.g., bicarbonate rich, silica-rich, chloride rich, sulfate-rich) and TDS concentration (1000 - 10,000 mg/l).Objective 4. Perform an overall technoeconomic (TEA) of the process to quantify the economic impact of the fluidized photocatalytic denitrification unit.
Project Methods
Methods: (i) Researchers at the University of Iowa will optimize metal oxide/metal catalysts identified in Phase 1 with varying metal oxide chemical composition and metal catalyst loading. This will be achieved through in-house thermal and chemical treatments available at the University of Iowa labs. (ii) The selectivity and stability of the synthesized catalysts for nitrate conversion will be probed first using an in-house batch reactor by Pani Clean, and (iii) using rapid operando spectroscopy tools housed at Dr. Shan's lab at the University of Houston. The operando spectroscopy tools and the stirred batch photocatalytic reactor will allow for rapid and cost-effective screening of photocatalysts. (iv) Pani Clean will then test the best-in-class photocatalyst formulations with enhanced selectivity, photoactivity, and stability in 1 L (lab scale), and 10 L (mini-pilot scale) fluidized reactors for their nitrate treatment performance. (v) Additionally, process design and economic model will be built to verify the advantages of the approach compared to available nitrate treatment technologies.

Progress 09/01/23 to 08/31/24

Outputs
Target Audience:Pani Clean has actively engaged with communities in Iowa that rely on private well water. Our focus was on understanding their pain points regarding water treatment needs and raising awareness about nitrates in water so that these communities could take preventive measures to protect their health. Pani Clean reached out to the International Centre for Clean Water (ICCW)in India to promote awareness of nitrate contamination challenges in the region. This served to introduce Pani Clean's innovative technologies for nitrate remediation, addressing a pressing issue that has received less attention than other water-related challenges in India. Pani Clean has offered guidance and internship opportunities to high school students eager to understand water-related challenges and explore cutting-edge, low-cost, energy-efficient water treatment technologies. One of our students achieved significant recognition, winning the 1st place in the regional Water Awards for High School students. Changes/Problems:The optimization of PPH phase composition and catalyst loading %, along with the batch reactor testing, which were initially scheduled to be carried outuntil the end of Year 2, were completed ahead of schedule. This allowed the team to shift focus towards optimizing the mini-pilot system in Year 2. Additionally, the technoeconomic analysis, originally planned to begin in the second quarter of the second year, was performed in the first year. This early analysis provided a clearer understanding of the major cost drivers, enabling the team to concentrate on cost-effective materials and processes. As a result, we were better positioned to select critical parts and components for scaling up the system in Year 2. What opportunities for training and professional development has the project provided?Pani Clean participated in several key workshops and expos to stay informed on trends and cutting-edge technologies in the water treatment field: Water Leaders Summit: Hosted by the Water Council, a global hub dedicated to addressing critical water challenges. Mazarine WaterVent: Organized by Mazarine Ventures, with a focus on advancements in water and wastewater treatment technologies. Water Environment Federation's Technical Exhibition and Conference (WEFTEC): The world's largest gathering of water quality professionals, offering comprehensive insights into industry innovations. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?In Year 2, the focus will be on further investigating the properties of the metal oxide using operando spectroscopy to better understand the relationship between the metal oxide, catalyst properties, and the final conversion efficiency. This will aid in optimizing the composition into a final product. A scaled-up system will be tested as a mini-pilot unit to effectively remove nitrates from feedstock water, and the TEA will be refined to determine the levelized cost of the system for commercialization. The emphasis will remain on optimizing operational efficiency and reducing treatment costs to meet the project's objectives.

Impacts
What was accomplished under these goals? The overarching goal of this project is to develop a high-efficiency photocatalytic denitrification unit capable of sustainably reducing nitrates in wastewater at a competitive cost. In Phase I, the project demonstrated the feasibility of fluidized bed reactors combined with particulate photocatalytic heterostructures (PPHs), achieving over 95% nitrate-to-nitrogen conversion efficiency in a small-scale batch setup. Building on this foundation, Phase II aims to refine these catalysts, scale the reactor system to lab-scale and mini-pilot prototypes, and assess economic feasibility. In the first year of Phase II, significant progress was made toward the project's primary objectives. The first objective focused on optimizing the photocatalyst through controlled variations in the metal oxide ratio, catalyst loading, and phase composition. We successfully achieved the optimal composition of metal oxide properties and catalyst loading, resulting in the best catalytic activity with the highest selectivity for the conversion reaction. Experimental tests using batch reactors confirmed that catalysts with the optimized metal oxide and 0.5 wt% catalyst loading yielded optimal results, achieving over 95% nitrate reduction in simulated conditions. Notably, this catalyst formulation demonstrated high selectivity for nitrogen gas production, exceeding 90%, a critical factor for effective nitrate removal from water, with stability confirmed across multiple cycles. A crucial Phase II goal was the construction and testing of lab-scale (1 L) and mini-pilot (10 L) fluidized bed reactors, addressing the third objective of scaling the technology. We successfully scaled up the reactor design, achieving consistent fluidization of the PPHs throughout testing, which is one of the most critical aspects of scale-up. The 1 L reactor demonstrated continuous nitrate reduction capability, with efficient particle fluidization and stability during extended operations. However, when tested with real-world water samples sourced from reverse osmosis (RO) reject brine, the system's nitrate removal efficiency was limited by competing ions such as calcium and magnesium, which affected the PPHs' conversion processes. Pre-treatment of these brines significantly improved nitrate conversion, highlighting the importance of pre-treatment steps for effectively handling complex real-world water samples. Scaling to the 10 L reactor presented fluidization challenges, including catalyst settling and reduced nitrate conversion. Adjustments to the reactor design, such as the introduction of baffle plates, improved fluid distribution. The team then identified a commercial fluidized bed reactor that matched the PPH properties for fluidization, facilitating scalability more effectively than a customized system. Finally, the fourth objective involved conducting a technoeconomic analysis (TEA) to assess the cost feasibility of the system. Key findings indicated that UV lighting is a significant cost factor, and incorporating renewable energy sources could improve economic viability. Additionally, the TEA underscored the importance of extending catalyst lifespans to reduce maintenance costs. Preliminary TEA results align with the project's goal of achieving a photon-to-chemical efficiency (PCE) greater than 8.5%, which is crucial for maintaining cost competitiveness compared to traditional methods. In summary, the first year of Phase II demonstrated success in optimizing catalyst composition and loading for improved conversion selectivity, refining reactor design for efficient fluidization and scale-up, and conducting preliminary TEA to address key cost contributors for scaling the system.

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