Industrial byproducts, such as phosphogypsum, pose a significant environmental risk due to their content of heavy metals, radioactive elements, and toxic substances. When these materials leach into soil and groundwater, they can cause serious issues like drainage blockages, dust pollution, and the release of fluoride (F). To combat this, researchers are turning to new and sustainable solutions for wastewater treatment. A recent study published in ACS Omega by Geming Wang and colleagues explores a pedagogical approach to this problem, using a porous biochar-based capacitive deionization (CDI) device to treat phosphogypsum wastewater. This study not only showcases an effective treatment method but also serves as an educational framework for undergraduate students in materials science and chemical engineering.

The core of this technology is capacitive deionization (CDI), a method that uses an electrical charge to pull and trap ions from contaminated water onto electrode surfaces. This process, known as electrosorption, is more cost-effective than conventional methods like reverse osmosis and multi-stage flash desalination. While traditional CDI works well, its performance is highly dependent on the efficiency of the electrode material. The research team focused on enhancing biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More, a porous carbon material derived from biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More, for this specific application.

The researchers synthesized an advanced biochar electrode from coconut shells. The process involved converting the coconut shells into a porous carbon network through thermal decomposition in a low-oxygen environment. To boost its ability to remove contaminants like F and phosphorus (P), the biochar was modified by activating it with magnesium chloride (MgCl2​) and aluminum chloride (AlCl3​). This modification created a highly porous structure that facilitates ion diffusion and adsorption. The successful incorporation of magnesium and aluminum was confirmed by elemental mapping, showing a uniform distribution across the material’s surface.

The study found that the CDI device with the modified biochar electrodes was highly effective at removing P and F ions from simulated wastewater. The team evaluated the system under various operating conditions to find the optimal balance between performance and stability. They discovered that an applied voltage of 1.2 V offered the best results, removing 40.26% of P ions and 30.8% of F ions, while avoiding side effects like gas bubble formation that occurred at higher voltages. The research also highlighted the importance of maintaining a slightly acidic pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More of 5, which enhanced the biochar’s positive surface charge and improved its ability to attract negatively charged P and F ions. At this optimal pH, the highest adsorption efficiency was observed.

The modified biochar electrodes proved to be exceptionally durable and efficient. Over 16 consecutive adsorption-desorption cycles, the electrodes maintained 94.2% of their original ion-removal performance, demonstrating their excellent reusability. The system also had a remarkably low energy consumption, calculated at 0.000306 kWh-m³, which the authors attribute to the enhanced surface properties from the magnesium and aluminum doping.

Beyond the technical findings, this study serves as a novel educational model. The curriculum guides students through the entire process, from preparing the biochar electrodes to assembling and operating the CDI device for wastewater treatment. This hands-on approach allows students to gain practical experience and apply theoretical knowledge to real-world problems. A post-experiment evaluation showed significant improvement in student understanding, with nearly all participants being able to describe the entire process and understand the key concepts. This educational framework successfully bridges fundamental research with practical, experiential learning.

In conclusion, this research provides a sustainable and efficient solution for treating phosphogypsum wastewater using a modified biochar electrode. The successful removal of P and F ions, coupled with the electrode’s high durability and low energy consumption, highlights its potential for real-world applications. The project’s unique educational design also provides a pathway for training the next generation of environmental professionals.

Source: Wang, G., Zhou, S., Yang, Z., Chen, D., Zhao, H., Chen, Z., Hu, S., Rahman, S. T., & Wu, Q. (2025). Exploring a Porous Biochar-Based Capacitive Deionization Device for Phosphogypsum Wastewater Treatment in Undergraduate Experimental Teaching: Understanding, Development, and Practice. ACS Omega, 5(C05966), 1-11.