This study investigates the kinetic and equilibrium behavior of fluoride adsorption onto thermally treated eggshells (ES-800) under batch conditions. Kinetic experiments were conducted at 15, 25, and 35 °C using a fixed concentration of 500 mg/L fluoride and 3.33 g/L ES-800. The results showed rapid initial uptake, with adsorption reaching 136.29 mg/g within 12 hours and increasing to 141.70 mg/g after 24 hours. The pseudo-second-order kinetic model provided a better fit (R² = 0.954) than the pseudo-first-order model (R² = 0.912), indicating that chemisorption is the dominant rate-limiting mechanism. This suggests that fluoride ions form strong chemical bonds with active sites on the ES-800 surface, likely involving calcium hydroxide and oxide groups.SCG2 Antibody In Vitro
Equilibrium adsorption studies were performed across initial fluoride concentrations ranging from 200 to 1000 mg/L at 25 °C. The Langmuir isotherm model yielded a higher R² value (0.991) compared to the Freundlich model (0.919), confirming that fluoride adsorption occurs via monolayer coverage on homogeneous surfaces. The maximum adsorption capacity (Qₘ) was calculated as 258.28 mg/g at 25 °C, increasing to 273.19 mg/g at 35 °C and decreasing slightly to 198.44 mg/g at 15 °C. The Freundlich constant (1/n) ranged between 0.230 and 0.269, indicating strong adsorption affinity and favorable conditions for the process. These results confirm that the system exhibits high selectivity and capacity for fluoride removal.
Thermodynamic analysis revealed that the adsorption process is endothermic (ΔH⁰ = 92.34 kJ/mol) and spontaneous (ΔG⁰ < 0), with positive entropy change (ΔS⁰ = 315.PKM2 Antibody Formula 91 J/mol·K), suggesting increased randomness at the solid-liquid interface during adsorption.PMID:34972256 The positive enthalpy indicates chemical interaction rather than physical adsorption. The data collectively demonstrate that fluoride adsorption by ES-800 follows a chemically driven, monolayer mechanism, with enhanced performance at higher temperatures. This insight supports the use of ES-800 in real-world applications where elevated temperatures may be present, such as in decentralized water treatment systems. The excellent fit of the Langmuir model further validates the material’s potential for predictable and scalable operation in defluoridation processes.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com