In a new article published in the journal ACS Omega, researchers Geming Wang, Shiyu Zhou, and Ziheng Yang, along with their colleagues, have presented an innovative pedagogical approach to teach sustainable wastewater treatment. The study outlines a hands-on curriculum for undergraduate students focused on building and testing a capacitive deionization (CDI) system. CDI is a technology that uses electrically charged porous electrodes to attract and remove ions from contaminated water, offering a lower-cost alternative to traditional desalination and water treatment methods. This particular study focuses on treating phosphogypsum wastewater, a byproduct of industries like fertilizer manufacturing, which poses significant environmental risks due to its content of toxic substances like phosphorus and fluoride.

The experiment guides students through the entire process, from creating porous 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 electrodes to assembling and operating a functional CDI device. The biochar was made from coconut shells, which were heated to 650∘C in an oxygen-limited environment to form a porous carbon network. To improve its performance, the biochar was then activated by doping it with magnesium chloride ( MgCl2​) and aluminum chloride (AlCl3​). This process created a more porous structure and introduced new functional groups that help capture ions. Characterization of the materials confirmed that the doping process was successful and that the biochar had a highly porous structure with uniformly distributed magnesium and aluminum.

One of the key findings of the research was the performance and durability of the developed electrodes. The team’s analysis revealed that after 16 consecutive adsorption-desorption cycles, the Mg-Al-BC electrodes retained 94.2% of their initial salt adsorption capacity. This is a critical indicator of the material’s stability and reusability, which are essential for practical, long-term wastewater treatment applications.

The study also investigated the optimal operating parameters for the CDI system. The researchers found that while higher voltages led to increased ion removal efficiency, a voltage of 1.2 V offered the best balance between performance and electrode stability. Specifically, at 1.2 V, the adsorption efficiency for phosphorus ions was 40.26%, and for fluoride ions, it was 30.8%. Higher voltages, such as 1.4 V, caused unwanted side effects like gas bubbles and electrode damage. The study also found that an optimal flow rate of 50 mL/min was ideal for maximizing adsorption efficiency by balancing ion transport and contact time with the electrode.

The research highlights the practical and educational value of this experimental framework. It gives students hands-on experience in materials science and chemical engineering, bridging the gap between theoretical knowledge and real-world problem-solving. The learning process helped students develop a comprehensive understanding of the entire workflow, from biochar synthesis to CDI device testing. This type of practical training is vital for creating a new generation of skilled professionals who can develop sustainable solutions to environmental issues like water pollution. The low specific energy consumption of the device, calculated at 0.000306 kWh/m³, further emphasizes the material’s efficiency and its potential for real-world use.

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, 10.1021/acsomega.5c05966.