Carbamazepine is used to treat epilepsy and nerve pain and has been detected in wastewater and natural waters. Ultraviolet-based advanced oxidation processes can degrade pharmaceuticals by activating chemicals such as peroxymonosulfate, hydrogen peroxide or chlorine. Wastewater also contains microplastics, including polyamide particles shed from textiles. As these particles age, their surfaces change and can interact with pollutants and treatment chemicals. Earlier studies reported that microplastics could either help or hinder pollutant degradation, depending on the materials involved. What remained unclear was how aged polyamide affects carbamazepine removal across different oxidants—and whether the resulting products present additional risks.
A study (DOI: 10.48130/newcontam-0026-0021) published in New Contaminants on 09 September 2026 by Xiaohui Wang's & Tingting Zhang's team, Beijing University of Chemical Technology, reports that aged polyamide increased carbamazepine degradation rates while changing the amounts of potentially toxic transformation products formed.
To test these effects, the researchers added carbamazepine and aged polyamide particles to laboratory reactors using ultraviolet light with one of three oxidants: peroxymonosulfate, hydrogen peroxide or chlorine. They compared each setup with a corresponding treatment containing no microplastics, measured carbamazepine over two hours, and calculated degradation rate constants. Adding aged polyamide raised those constants to 2.30, 0.70 and 0.36 per hour, respectively—1.2, 1.3 and 1.8 times the rates without particles. Peroxymonosulfate gave the fastest overall degradation, while chlorine showed the largest relative boost from microplastics. Using electron paramagnetic resonance and chemicals that intercept reactive species, the team investigated what drove the changes. Their measurements indicated that aging produced persistent free radicals on the polyamide surface and that aged particles increased the formation of hydroxyl radicals and singlet oxygen. The dominant reactive species still varied by oxidant; chlorine radicals also contributed substantially in the ultraviolet/chlorine system. Mass spectrometry identified 16 transformation products in the peroxymonosulfate treatment with aged particles, 14 in the hydrogen peroxide treatment and 15 in the chlorine treatment. From these products, the researchers proposed pathways involving hydroxylation, oxidation and changes to carbamazepine’s ring structure. Aged particles mainly increased reaction rates and the abundance of certain products, while the choice of oxidant accounted for the clearer differences in pathways. A computer-based assessment predicted that several products could be more toxic to aquatic organisms than the original drug. Finally, tests of common water constituents showed that nitrate promoted carbamazepine degradation across the three systems, whereas bicarbonate and humic acid inhibited it. Chloride's effect depended on the treatment system and its concentration. These results show why laboratory removal rates alone may not predict how a process performs in wastewater with a different chemical composition.
The study suggests that aged microplastics are active participants in ultraviolet-based treatment, influencing both how quickly carbamazepine disappears and which byproducts accumulate. Its toxicity findings are predictions, so measuring byproducts and testing treated water would help establish their practical significance. For wastewater treatment, the central lesson is to evaluate the fate of the drug alongside the fate of its transformation products.
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References
DOI
10.48130/newcontam-0026-0021
Original Source URL
https://doi.org/10.48130/newcontam-0026-0021
Funding information
This work was financially supported by the National Natural Science Foundation of China (Grant No. 41977142).
About New Contaminants
New Contaminants (e-ISSN 3069-7603) is a multidisciplinary platform for communicating advances in fundamental and applied research on emerging contaminants. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of new contaminants research around the world to deliver findings from this rapidly expanding field of science.