Biosorption of fluoride by apple pulp from aqueous solution

 Introduction: Fluoride is an essential element at low concentrations in drinking water. On the other hands, excessive levels of fluoride can cause a number of problems such as dental fluorosis and skeletal fluorosis. Therefore, this study was carried out with the aim of application of apple pulp in order to fluoride removal from aqueous solutions. Materials and Methods: Apple pulp was modified with H2O2 (30 %wt) and were tested for fluoride removal. In batch experiments, effect of various parameters such as pH (2-10), adsorbent mass (2-10 g/L), initial fluoride concentration (5-20 mg/L) and contact time (1-120 min) were studied. In addition, experimental data were fitted to Langmuir and Freundlich isotherms. Results: Fluoride removal at optimum conditions was 86.7% and 89% for natural and H2O2-modified apple pulp, respectively. Maximum removal (92 and 95.4 for natural and H2O2-modified apple pulp) achieved at adsorbent dosage of 10 g/L. From the results of various kinetic models, pseudo-second-order model best describe the fluoride adsorption by natural and H2O2-modified apple pulp (R2= 0.992 and 0.998 respectively). The experimental adsorption data complied with Langmuir isotherm. Conclusion: Modification of natural apple pulp with H2O2 improved the removal efficiency. Apple pulp could be employed as an effective adsorbent for the removal of fluoride ions from aqueous solutions