Enhanced fluoride removal using alumino urea gel synthesized by a facile hydrothermal method

Fluoride with high amounts in drinking water is harmful to human's health. In this study, an aluminum-urea gel adsorbent (AUG) was synthesized using aluminum chloride and urea as raw materials based on a simple one-pot hydrothermal method and applied for the defluoridation of drinking water. The structures of AUG were characterized and its defluoridation performance was evaluated. Our experimental results showed that the surface of AUG was amorphous with rich functional groups and its efficiency for fluoride removal exceeded 90% in the pH range of 5.0-8.0 with good stability. The fluoride adsorption isotherm of AUG could be fitted well with Langmuir with its maximum adsorption capacity at 107.7 mg/g. The pseudo-second-order model implied that the adsorption mechanism of fluoride on AUG was mainly based on chemical reactions between fluoride and the ligands between unsaturated aluminium and carbon functional groups. In addition, ion exchange effect and electrostatic attraction may also help the adsorption. Our study suggests that AUG might become a potential defluoridation agent for drinking water.