An enhanced pH-response CS/CaO₂ nanocomposite with nucleocapsid structure for environmental remediation: Preparation, characterization, and application

The formation process of contaminated groundwater is invariably associated with pH fluctuations caused by the intrusion of anthropogenic contaminants, including heavy metals and organic compounds. In this study, a pH-responsive CaO 2 nanocomposite wrapped in chitosan (CS/CaO 2 ) was successfully synthesized via a pH-regulated chemical precipitation method. The CS/CaO 2 exhibited a well-defined core-shell bilayer structure with particle sizes ranging from 100 to 200 nm. Significantly, the incorporation of the chitosan (CS) coating not only enhanced the pH responsiveness but also reduced nanoparticle agglomeration. The sequence of reagent addition was found to be critical in achieving successful encapsulation. Simulation experiments were performed to assess the remediation effect on organic p- nitrophenol (PNP) and inorganic heavy metals. The inner core CaO 2 , acting as a solid source of H 2 O 2 , would be released as the external CS was broken after experiencing pH response. A CaO 2 modified Fenton system was then provided for the oxidative degradation of PNP, and its concurrently generated Ca(OH) 2 could facilitate the precipitation and immobilization of heavy metals. Removal efficiency exceeded 95 % under the optimized experimental conditions, demonstrating the high effectiveness of this approach. Overall, this study presents an enhanced pH-responsive nucleocapsid CS/CaO 2 nanocomposite with promising applications in the multi-contaminant remediation.