Removal of Fluoride from Aqueous Solution using Calcium Peroxide as a Low-cost Adsorbent

Abstract

Removal of fluorides from water is essential for humans and animals because it causes dental and bone deficiency. The maximum permissible limit of fluoride is 1.5 mg/L, according to the World Health Organization. Recently it became known that countries like Pakistan, India, Sri Lanka, China, Argentina, etc. have high fluoride concentration in groundwater. In the present work, calcium peroxide nanoparticles adsorption behaviour and its fluoride removal efficiency from an aqueous phase was studied. Adsorption technique was used to concentrate fluoride on the adsorbent. The advantage of using adsorption is that it is a technique which is easy to implement and relatively cheap. To characterise the structure, size and morphology of adsorbent nanoparticles, Fourier-transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy with energy dispersion X-ray spectroscopy, and Raman spectroscopy were applied. In batch adsorption experiments, the process parameters varied were: pH (2–12); contact time (5–60 min); adsorbent dosage (0.05–1 g); concentration (10–100 mg/L), and temperature (5–60°C). The kinetic study has shown that the experimental data are consistent with pseudo second order model with the regression coefficient of 0.99. The adsorption equilibrium is best describable by Langmuir isotherm model with adsorption capacity of 89.6 mg/g. The process thermodynamic was also studied to confirm the proposed mechanism of fluoride adsorption on the adsorbent. The isothermal multistage adsorption was investigated to understand the mechanism of calcium peroxide nanoparticle adsorption for fluoride removal. The maximum fluoride adsorption capacity calculated for CaO2 was 89 mg/g, with 90% defluoridation efficiency. The results suggested that calcium peroxide nanoparticles can be considered as a promising adsorbent for fluoride removal.