Hydrous CeO₂ polypyrrole nanocomposite as a stable and efficient adsorbent for defluoridation of acidic wastewater

Polypyrrole (PPy) is widely available and has excellent potential for removing fluoride. Current research on PPy for fluoride removal mainly focuses on low-pollution neutral solution systems, such as drinking water and groundwater. However, there are fewer systematic studies on defluorination in acidic wastewater. In this work, a highly efficient hydrous CeO2 polypyrrole nanocomposite (HCeO2@PPy) was prepared by in situ oxidative polymerization. The composites were characterized using XRD, SEM-EDS, FTIR, XPS, and point-of-zero charge (pzc) determination. The material was tested for its ability to remove fluoride from both simulated and industrial wastewater. The results showed that the adsorption capacity of HCeO2@PPy increased by 3 times to 43.6 mg/g when compared to PPy. The adsorbent was particularly effective in removing F- under acidic conditions. The Langmuir model was used to describe the adsorption process, and the maximum adsorption capacity was 80.93 mg/g. In competitive anion adsorption experiments, other ions had negligible effects on fluoride ion removal and the adsorbent had a strong affinity for F-. In addition, the adsorbent was able to achieve a removal efficiency of 71.7% in acidic wastewater. The main adsorption mechanism is attributed to ion exchange and electrostatic attraction. This study provides new insights for the development of efficient and stable fluoride removal materials in acidic fluoride wastewater with complex compositions.