Polyaniline grafting induces abundant active sites on red soil for fluoride removal from wastewater

Water pollution is currently a critical global issue. Various research groups have developed active adsorbent materials. This study aims to enhance the adsorption of water pollutants, particularly fluoride, by modifying the electronic structure of red soil through in-situ chemical oxidative polymerization techniques. The synthesized materials were characterized using techniques including powder XRD, FT-IR, UV spectroscopy, and Conductometer, followed by testing their adsorption performance. The XRD analysis revealed that while the crystal structures of embedded red soil remained amorphous, polyaniline (PANI) and PANI/red soil (RS) nanoparticles became polycrystalline. The maximum adsorption capacity (qmax) of fluoride ions by PANI/RS was determined to be 9.35 mg/g. Optimization experiments showed that PANI/RS exhibited maximum adsorption performance for fluoride ions under specific conditions: pH 4.0, a contact time of 50 min, temperature of 35 °C, and an initial concentration of 15 mg/L with 2 mg of adsorbent, achieving a removal efficiency of 99.9%. Both Langmuir and Freundlich isotherm models demonstrated a good fit with the experimental data, with R² values of 0.94 and 0.95, respectively. This suggests that PANI/RS is an effective adsorbent material for removing fluoride ions from wastewater. Overall, PANI/RS outperformed red soil alone, demonstrating potential for practical application in water treatment processes.