Characterization and performance of novel carbon-doped aluminum-modified bentonite for cost-effective fluoride removal

Abstract

Elevated fluoride levels in water pose a critical global health issue, necessitating advanced remediation strategies. This study introduces a novel, cost-effective approach using clay minerals, specifically bentonite, enhanced with carbon-doped aluminum. The resulting composite, carbon-doped aluminum-bentonite (CCDAB), exhibits exceptional fluoride adsorption performance. Detailed structural analyses by SEM, FTIR, BET, and X-ray diffraction reveal successful carbon-doped aluminum integration, which markedly improves fluoride uptake. Adsorption kinetics adhere to pseudo-second-order models, signifying predominant chemical interactions, while the Langmuir isotherm model indicates monolayer coverage. CCDAB achieves a fluoride adsorption capacity of 85.51 mg/g and a removal efficiency of 95.3 %, demonstrating robust performance even in the presence of competing ions. Its efficacy over a broad pH range (3−7) is attributed to its high point of zero charge (pHpzc), which enhances electrostatic interactions. Carbon doping introduces additional active sites, synergistically enhancing fluoride removal alongside aluminum oxide. Thermodynamic analysis confirms that the process is both spontaneous and endothermic. The mechanisms of fluoride removal encompass electrostatic attraction, ion exchange, and surface complexation. This study highlights CCDAB’s promise as a highly effective and economical solution for fluoride contamination in water.