Fluoride removal from water by granular ceramic adsorption

Fluoride contamination in water remains a global concern due to its potential health effects when present in high concentrations. Existing methods for fluoride removal often face limitations in efficiency or cost. While prior research has explored adsorption as a viable approach, gaps remain in understanding how pH, coexisting ions, and adsorbent properties influence fluoride uptake. This uncertainty drives the need for new materials that can enhance fluoride removal under variable conditions. No prior work had resolved the role of granular ceramic in this context. Researchers have yet to fully determine how surface characteristics and solution chemistry interact to affect adsorption. The role of temperature and kinetic models in fluoride removal has also remained unclear. This study addresses these open questions by introducing a novel adsorbent and analyzing its performance under diverse environmental conditions.

The aim of this study was to evaluate granular ceramic as a new adsorbent for fluoride removal from water. The researchers focused on understanding how physical and chemical properties of the adsorbent influence its effectiveness. They examined the impact of pH, coexisting ions, and temperature on adsorption. The study also aimed to determine the best-fit isotherm and kinetic models for the process. A specific problem addressed was the variability in adsorption efficiency under different solution conditions. The motivation stems from the need for cost-effective and stable adsorbents for water treatment. By characterizing the adsorbent’s surface and adsorption behavior, the study contributes to optimizing fluoride removal strategies. The findings may inform the design of water treatment systems that operate efficiently under real-world conditions.

The researchers used BET, SEM, and EDS to assess the physical and chemical properties of granular ceramic. These techniques provided data on particle size, pore distribution, and surface roughness. Fluoride adsorption experiments were conducted in a batch system to evaluate removal efficiency. Variables included initial fluoride concentration, solution pH, and presence of coexisting ions. Adsorption equilibrium data were collected at three different temperatures: 293, 303, and 323 K. The Langmuir and Freundlich isotherm models were applied to interpret the equilibrium data. Kinetic studies were performed to determine the rate of fluoride uptake. The pseudo-second-order model and intraparticle diffusion were used to analyze the adsorption process.

Fluoride adsorption was highest at pH 5.0–8.0, indicating a strong pH dependence. The Freundlich isotherm provided a better fit for the equilibrium data than the Langmuir model. Adsorption capacity increased with rising temperature, suggesting endothermic behavior. The pseudo-second-order model best described the adsorption kinetics. Intraparticle diffusion was identified as a key mechanism in fluoride uptake. Presence of phosphate and sulfate ions reduced adsorption efficiency. Chloride and nitrate ions had a minor positive effect on fluoride removal. These findings suggest that solution chemistry and adsorbent properties are critical to the process.

The study demonstrates that granular ceramic is effective for fluoride removal under specific pH and temperature conditions. The adsorption process follows a pseudo-second-order model, with intraparticle diffusion as a major mechanism. The Freundlich isotherm better describes the adsorption behavior than the Langmuir model. The presence of certain ions, like phosphate and sulfate, hinders fluoride uptake. Chloride and nitrate ions slightly enhance adsorption. The pH range of 5.0–8.0 is optimal for maximum removal. These findings align with the authors’ claim that granular ceramic is a promising adsorbent for water treatment. The results support the need to consider solution chemistry when designing fluoride removal systems.