Drinking Water Purification Using Metal-Organic Frameworks: Removal of Disinfection By-Products
Academic Background
With the increasing severity of global clean water shortages, research on drinking water purification technologies has become particularly important. In drinking water treatment processes, chlorination and chlorine dioxide disinfection are commonly used methods. Although they effectively kill bacteria and viruses, they also produce some toxic by-products, such as chlorite (ClO₂⁻) and chlorate (ClO₃⁻). Despite the low toxicity of these compounds, recent studies have indicated that long-term exposure to such by-products may be associated with chronic diseases and hormonal disorders. Therefore, the European Union has recently set maximum allowable concentration standards for these compounds in drinking water, requiring that the concentration of chlorite and chlorate in each liter of water does not exceed 0.25 mg.
Currently, the existing technologies for treating these disinfection by-products have many limitations, such as complicated implementation and maintenance, high cost, and poor durability. Therefore, it is an urgent task to develop new technologies to effectively remove these by-products. Metal-organic frameworks (MOFs), as an emerging class of porous materials, have shown great potential in the field of wastewater treatment in recent years due to their high specific surface area, tunable pore structures, and excellent adsorption properties. However, the application of MOFs in drinking water treatment—especially for the removal of chlorite and chlorate—has not yet been systematically studied.
Source of the Paper
This paper was co-authored by Gabriel Sanchez-Cano, Pablo Cristobal-Cueto, Lydia Saez, and others from Canal de Isabel II company (Spain), IMDEA Energy Institute, Rey Juan Carlos University, etc. The paper was published on April 10, 2025 in the journal Chem, titled “Drinking Water Purification Using Metal-Organic Frameworks: Removal of Disinfection By-Products”.
Research Process and Results
1. Material Screening and Synthesis
The study first screened four different iron-based MOF materials, including MIL-53-NH₂, MIL-88B, MIL-88B-NH₂, and MIL-101-NH₂. These materials all have high hydrolytic stability and porous structures, making them suitable for water treatment. The researchers synthesized these MOFs through the solvothermal method, and characterized them by X-ray powder diffraction (XRD) and thermogravimetric analysis (TGA) to ensure that their structures were as expected.
2. Static Adsorption Experiments
In the static adsorption experiments, the synthesized MOF materials were suspended in drinking water containing different concentrations of chlorite and chlorate. The adsorption efficiency and material stability were monitored by ion chromatography (IC) and high-performance liquid chromatography (HPLC). The results showed that MIL-88B-NH₂ exhibited the best adsorption performance, being able to completely remove chlorite within 15 minutes and remove 41.4% of chlorate under high concentration conditions. In addition, MIL-88B-NH₂ demonstrated extremely high stability during the adsorption process, with a degradation rate of less than 1%.
3. Kinetic Study
To further understand the adsorption process, the researchers conducted kinetic studies on MIL-88B-NH₂. The results indicated that the removal of chlorite was extremely rapid, reaching 100% removal within 1 minute, while the adsorption of chlorate reached saturation within 5 minutes, with a removal rate of about 30%. The adsorption kinetics fit a pseudo-second-order kinetic model, indicating that the adsorption process is mainly controlled by ion-exchange reactions.
4. Continuous-Flow Adsorption Experiments
Based on the excellent performance of MIL-88B-NH₂, the researchers designed a continuous-flow adsorption device to simulate the operating conditions of an actual drinking water treatment plant. The experimental results showed that the device could continuously and efficiently remove chlorite and chlorate for 3 days, and the material maintained its stability during continuous operation, with a degradation rate of less than 2%. In addition, the researchers regenerated the adsorbent using a simple sodium chloride solution, demonstrating the reusability of the system.
5. Molecular Simulation
To gain a deeper understanding of the adsorption mechanism, the researchers conducted molecular simulations to study the adsorption behavior of water molecules and salt molecules in the structures of MIL-88B and MIL-88B-NH₂. The simulation results showed that the presence of salt molecules significantly enhanced the adsorption of water molecules in the MOFs structures, and that the electrostatic interaction between chlorate, chlorite, and the MOFs framework is the key factor in the adsorption process.
Conclusions and Significance
This study systematically explored for the first time the application of MOFs in drinking water treatment, specifically for the removal of chlorite and chlorate. The results showed that MIL-88B-NH₂, as a highly efficient and stable adsorbent, can rapidly remove disinfection by-products from drinking water and perform well under actual operating conditions. Through the design of continuous-flow adsorption devices and regeneration experiments, the researchers demonstrated the feasibility of applying MOFs in drinking water treatment plants.
The scientific value of this research lies in the first application of MOFs in drinking water treatment, providing a new solution for the removal of disinfection by-products. Its practical value is reflected in the high efficiency, stability, and reusability of MOFs materials, which can significantly reduce the cost and complexity of the drinking water treatment process.
Research Highlights
- High-Efficiency Adsorption Performance: MIL-88B-NH₂ can completely remove chlorite in an extremely short time and effectively remove chlorate under high concentration conditions.
- Material Stability: MOF materials exhibit extremely high stability during continuous operation, with a degradation rate of less than 2%.
- Continuous-Flow Adsorption Device: The researchers designed a continuous-flow adsorption device simulating the operating conditions of actual drinking water treatment plants, proving the feasibility of applying MOFs in practical scenarios.
- Molecular Simulation: Through molecular simulation, the researchers gained a deep understanding of the adsorption mechanism, providing a theoretical basis for optimizing MOF materials.
This research opens a new direction for the application of MOFs in drinking water treatment, with important scientific and practical value.