Urea is used as a low-cost agricultural nitrogen fertilizer and poses environmental challenges when present in agricultural runoff (Shutterstock)
Imagine that you had a device that could not only select urea from a mixture of water, but at the same time convert it into a clean energy source: hydrogen gas.
This may seem far-fetched, but a research team from the Worcester Institute of Applied Sciences in America succeeded in achieving this. It announced, in a study published in the Journal of Physical Chemistry Letters, the design of this “supermaterial” that does not merely select urea alone from among The mixture of substances found in water, but also made it economically valuable.
From "eutrophication" the problem begins
Urea is usually used as a low-cost nitrogen agricultural fertilizer, and it poses environmental challenges when it is present in agricultural runoff and municipal wastewater, as its discharge contributes to what is known as “eutrophication,” which has negative consequences on the ecosystem.
Eutrophication is a process through which a waterway is enriched with nutrients such as nitrogen. When these substances enter the water, they stimulate the growth of algae and other aquatic plants, which creates hypoxic “dead zones” and negatively affects aquatic ecosystems and human health.
This negative effect occurs when algae and plants die and decompose, and the bacteria consume the decomposing matter, which leads to an increase in the consumption of oxygen in the water, and this can lead to a decrease in the proportion of this element, and in extreme cases “dead areas” that lack its presence can form, which is This harms fish and other aquatic organisms that depend on oxygen-rich water, and disrupts the balance of the aquatic ecosystem, affecting the abundance and distribution of different species. It can also lead to the dominance of certain species, often harmful algae, at the expense of other species.
Extracting hydrogen from urea adds value to the process of removing it from water (Shutterstock)
5 attempts.. 5 obstacles
Before the latest attempt made by researchers at the Worcester Institute of Applied Sciences in America, previous studies explored different ways to reduce or remove urea from water, which are:
Biological treatment:
It depends on the use of some microorganisms and bacteria to decompose urea naturally through biological processes.
Advanced oxidation processes:
By using advanced chemical processes to decompose or oxidize pollutants in water, and exploring techniques such as photocatalysis and ozone to break down urea molecules into less harmful components.
Adsorption and filtration:
Through the use of materials that can capture and remove urea from water, such as activated carbon and certain types of membranes.
Electrochemical methods:
These methods include the use of electrical energy to facilitate chemical reactions that lead to the decomposition of urea.
Chemical precipitation:
It involves adding specific chemicals to water to induce the formation of solid molecules that can be easily separated.
The previous five methods showed positive results on the laboratory scale, but there are obstacles that prevented them from developing into an applied solution, including:
Non-selectivity:
These methods do not achieve high selectivity in targeting urea specifically, which leads to unwanted oxidation or removal of other substances present in the water, and this lack of selectivity can reduce the overall efficiency of the treatment process.
Energy Density:
Some methods are energy intensive, requiring large energy inputs for the processing process, and this can contribute to high operating costs and limit the feasibility of large-scale implementation.
Scalability:
Some technologies that work well in laboratories may face challenges when scaling up for real-world applications, because they lack the ability to handle large volumes of water.
Limited efficiency:
Some methods do not achieve high removal rates, or may be less effective in the presence of other common contaminants in the water.
Chemical waste:
Some chemical-based methods may introduce additional residues or byproducts into the water, which may raise secondary environmental concerns.
The presence of urea fertilizer in the water causes the process of “eutrophication” (Shutterstock)
A metamaterial... promising prospects for application
Based on studying previous experiments, and the challenges that prevented them from being applied on a large scale, researchers from the Worcester Institute of Applied Sciences in America worked on a solution based on “selective electro-oxidation of urea” using a non-polluting metamaterial that can handle large quantities of water and creates added value to the process. Treatment is the production of hydrogen gas from urea, so this approach holds promise for implementation on a large scale.
According to a press release published by the Worcester Institute of Applied Sciences website, the thinking about this substance was based on what is known about the unique properties of urea, the most important of which is that it contains a large percentage of hydrogen (6.7% by weight), and therefore electrolysis to produce hydrogen from it may be more efficient. Energy efficient and cost effective compared to traditional water electrolysis.
The researchers in the study do not claim to be the first to think about electrolysis of urea to extract hydrogen, but they point out that the obstacle facing previous attempts is the lack of affordable and highly efficient electrocatalysts capable of selectively oxidizing urea from water.
The researchers, led by Professor Xiaowei Teng, said they addressed this challenge by developing electrocatalysts comprising synergistically interacting nickel and cobalt atoms with unique electronic structures, facilitating the selective electro-oxidation of urea.
January 2024 cover of the Journal of Physical Chemistry Letters celebrates the invention
This achievement can be summarized as follows:
First - Material development:
Researchers built materials using nickel and cobalt atoms with specific electronic configurations. These materials were transition metal oxides and hydroxides, specifically nickel and cobalt oxides and hydroxides.
Second: Selective urea oxidation:
The key breakthrough was getting these materials to selectively oxidize urea in an electrochemical reaction, meaning the material could specifically target urea molecules and convert them into other substances such as hydrogen gas, without affecting the surrounding water molecules.
Third- Weaving the electronic structure:
The researchers found that the success of this selective oxidation lay in designing the electronic structures of the nickel and cobalt atoms, targeting the dominant species - the nickel ion and the cobalt ion - in the electronic configuration.
This "electronic structure" can be likened to the "language" or communication style of the nickel and cobalt atoms, and by modifying this language to contain more "words" - that is, more nickel and cobalt ions - the researchers made the material better at reacting with and converting urea.
Electrolysis to produce hydrogen from urea may be more efficient and less expensive compared to traditional electrolysis (Shutterstock)
A new era for the relationship between water and energy
In a telephone interview with Al Jazeera Net, Professor of Chemical Engineering at Ilmenia University (Southern Egypt), Khaled Abu Al-Ezz, praises this research achievement, because it benefits from the presence of urea fertilizer in the water to inaugurate a new era of the relationship between water and energy. By efficiently removing urea from water via an electrochemical process, researchers aim not only to address the pollution problem, but also to produce hydrogen gas as a potential energy source.
Choosing urea fertilizer for this work represents a smart gesture by the researchers, as Abu Al-Ezz explains, because the quantities of it leaking into waterways allow the construction of an economic project to extract hydrogen. It has been one of the major nitrogen fertilizers and feed additives since the 1920s, and approximately 180 million metric tons (one metric ton equals 1,000 kg) were produced in 2021.
But this praise did not prevent Abu Al-Ezz from pointing out that what was achieved in this research is a step that requires additional steps to answer two important questions in practical application, which are:
First: How stable are the electrocatalysts used in the long term, is there a possibility of degradation over time, and how can the stability of materials be improved for extended use?
Second: How can this technology be integrated with existing water treatment and energy production systems, and are there potential aspects of integration with other emerging technologies, and how can it fit into water and energy infrastructure?
Abu Al-Ezz says: “Researchers certainly need additional studies to answer these two questions. These studies may lead, for example, to further improving the electrocatalysts to increase efficiency and selectivity or making additional modifications to the electronic structures or structure to improve their performance.”
Source: Al Jazeera + websites