Enhanced fluoride removal over MgFe2O4-chitosan-CaAl nanohybrid: Response surface optimization, kinetic and isotherm study.

In this work an effective adsorption route was developed for fluoride removal from aqueous solution. For this purpose MgFe2O4, MgFe2O4-chitosan and a three component nanocomposite of were synthesized and used. Characterization of the sorbents was performed with FESEM, TEM, FTIR, BET, VSM, SEM mapping and XRD techniques. Effective parameters on the adsorption process such as pH, contact time, adsorbent dosage and fluoride concentration was optimized by response surface methodology (RSM) using Box-Behnken design (BBD). Results showed that solution pH is a significant factor in fluoride adsorption with all adsorbents. However, adsorbent dosage was a significant factor when MgFe2O4-chitosan and three component adsorbents are employed. Kinetic study was performed based on pseudo-first order, pseudo-second order, intraparticle diffusion and Elovich model and results confirmed fluoride adsorption followed the pseudo-second order model. Isotherm study was studied at two concentration ranges of 0.5-10 mg/L and 10-100 mg/L of fluoride ions. Results showed that adsorption process followed Langmuir model with capacity of 263.15 mg/g. Regeneration was performed with NaOH solution (0.1 mol/L). It was found that removal percentage is in the range of 91-73% in five cycles of adsorption and regeneration.