Modern municipal wastewater treatment plants (MWWTPs) are facing a growing challenge: removing microcontaminants, or chemicals of emerging concern (CECs), that persist even after primary, secondary, and tertiary treatments. These contaminants, which include pesticides, pharmaceuticals, and personal care products, pose significant risks to public health and aquatic ecosystems due to their bioaccumulative and toxic characteristics. In a recent study published in the Journal of Environmental Management, researchers Antonio Faggiano, Paula Soriano-Molina, Oriana Mottad, Antonio Proto, José Luis Casas López, Antonino Fiorentino, and José Antonio Sánchez Pérez investigated a promising new approach: using an iron-functionalized 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 catalyst in a solar photo-Fenton process to tackle this problem. Their work shows a highly effective method for a fourth stage of water purification, known as quaternary treatment, to meet increasingly strict environmental regulations.

The core of this innovative approach is iron-functionalized biochar (FeBC), a carbon-rich 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 that has been modified to enhance its catalytic properties. The study compared the performance of this modified biochar with raw biochar (RBC) from woodchips. The researchers confirmed that the functionalization process was successful, noting a significant increase in the biochar’s specific surface area (SSA) from 611 m²/g for RBC to a remarkable 855 m²/g for FeBC. This expanded surface area provides more active sites for the degradation of contaminants and is a key reason for the material’s enhanced performance. The team also found that iron leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More from the FeBC was minimal, staying below 1 mg/L, which is crucial for preventing the formation of iron hydroxide sludge and minimizing environmental impact.

In initial batch experiments using tap water spiked with the pesticide acetamiprid (ACTM), the FeBC showed superior performance. It achieved a 98% removal efficiency, slightly higher than the 95% seen with RBC. More importantly, when combined with hydrogen peroxide and sunlight, the FeBC catalyst resulted in a 56% degradation of ACTM, while the raw biochar only achieved a 10% degradation. This clearly demonstrates that the iron-functionalization makes the biochar an active catalyst, rather than just an adsorbent. The process was also effective at a neutral 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, which is a major advantage over traditional photo-Fenton processes that require acidic conditions, thereby reducing operational costs and environmental concerns.

The study then moved to a more realistic scenario using real MWWTP secondary effluent. Even with the presence of organic matter and other substances that can interfere with degradation, the FeBC system continued to outperform the raw biochar. FeBC maintained a high adsorption efficiency of 91% and achieved a remarkable 50% degradation of ACTM, compared to 88% adsorption and only 20% degradation with RBC. The most significant finding came from the pilot-scale continuous flow tests, which are more indicative of real-world application. The solar photo-Fenton process using FeBC was able to sustain a high total ACTM removal efficiency of 94% and an impressive 88% degradation under optimal conditions. The researchers also found that they could increase the treatment capacity from 4.0 mg ACTM/m²h to 6.9 mg ACTM/m²h by reducing the hydraulic residence timeResidence time refers to the duration that the biomass is heated during the pyrolysis process. The residence time can influence the properties of the biochar produced.   More (HRT) from 60 to 30 minutes, without a significant drop in removal efficiency. This suggests that the process can be optimized for both effectiveness and speed, making it a viable and efficient solution for upgrading wastewater treatment facilities. The success of this study highlights the potential of FeBC as a stable and powerful heterogeneous catalyst for the quaternary treatment of wastewater, offering a sustainable way to protect public health and the environment from emerging microcontaminants.

Source: Faggiano, A., Soriano-Molina, P., Mottad, O., Proto, A., Casas López, J. L., Fiorentino, A., & Sánchez Pérez, J. A. (2025). Iron-functionalized biochar in raceway pond reactors for quaternary treatment of municipal WWTP effluents. Journal of Environmental Management, 392, 126772.