Facile defluoridation of drinking water by forming shell@fluorapatite nanoarray during boiling egg shell

Millions of people globally face health risks due to high fluoride concentrations in drinking water. Conventional methods like adsorbents and treatment plants are effective for large-scale use but are not practical for scattered households, especially in developing regions. Existing solutions often require infrastructure or technical expertise, which limits accessibility. Prior research has shown that fluoride removal is possible through adsorption onto calcium-rich materials, but these methods may not be feasible for individual use. This gap motivated the search for a simpler, low-cost alternative. No prior work had resolved how to achieve defluoridation using common household items. The need for a user-friendly, affordable solution remains unmet. This paper introduces a novel approach using eggshells, a readily available material, to address this problem. The potential of eggshells in water treatment had not been fully explored until now.

The goal of this study was to develop a household-friendly defluoridation method using eggshells and common additives. The researchers aimed to create a process that requires no specialized equipment or training. They focused on using eggshells, which are abundant and inexpensive, as a natural adsorbent. The study tested the feasibility of using eggshells in combination with phosphate and acetic acid. The motivation was to provide an accessible solution for regions lacking water treatment infrastructure. The researchers wanted to determine if this method could consistently lower fluoride levels to safe thresholds. They also sought to understand the underlying mechanism of fluoride removal. The study aimed to validate the method’s effectiveness at both small and pilot scales.

The team tested a defluoridation process involving boiling eggshells in high-fluoride water with phosphate and acetic acid. They used 0.4 L of water with 10 mg/L fluoride and boiled one egg at 80 °C for 10 minutes. The setup included 0.3 g/L of NaH2PO4 and 0.05 v% acetic acid. Fluoride concentrations were measured before and after treatment. The same method was applied using eggshell powder instead of whole eggs. Scanning electron microscopy and X-ray diffraction were used to analyze the surface morphology and crystal structure of the treated eggshells. Pilot-scale experiments were conducted with 2.5 L of water across 10 trials. The researchers evaluated the Langmuir adsorption capacity to quantify the material’s fluoride uptake potential. This approach allowed them to assess both practical feasibility and adsorption efficiency.

The method successfully reduced fluoride levels from 10 mg/L to below 1.5 mg/L in 0.4 L of water. Boiling one egg with phosphate and acetic acid achieved this result in 10 minutes at 80 °C. The process formed fluorapatite or fluorine-substituted hydroxyapatite on the eggshell surface. Eggshell powder showed higher adsorption capacity than whole eggs, reaching 47.9 mg/g. Pilot-scale trials confirmed consistent performance across 10 repetitions with 2.5 L of water. Scanning electron microscopy revealed the formation of nanorod arrays on the eggshell surface. X-ray diffraction confirmed the presence of fluorapatite structures. The Langmuir model indicated strong adsorption affinity for fluoride ions. These findings suggest the method is both effective and scalable for household use.

The study demonstrates that boiling eggshells with phosphate and acetic acid can effectively remove fluoride from drinking water. The formation of fluorapatite or fluorine-substituted hydroxyapatite on the shell surface is a key mechanism. The method requires no specialized equipment and can be used by individuals with minimal training. Eggshell powder outperformed whole eggs in adsorption capacity, suggesting a more efficient approach. Pilot-scale testing confirmed the method’s reliability and consistency. The Langmuir adsorption capacity of 47.9 mg/g supports its practical viability. The researchers propose that this method could be adapted for household use in areas with limited water treatment infrastructure. These findings suggest a low-cost, accessible solution for defluoridation.