Removal of fluoride from drinking water using nanomagnetite aggregated schwertmannite

Fluoride contamination is a worldwide problem now-a-days. To remove this contaminant from water a new adsorbent was synthesized by applying a novel nanomagnetite aggregation process through the formation procedure of iron oxide hydroxide, i.e., schwertmannite (Fe8O8(OH)6SO4)(Fe8O8(OH)6SO4). Characterization of the new adsorbent was done by VSM, XRD, FTIR, BET and FESEM. The fluoride adsorption behavior of nanomagnetite aggregated schwertmannite (NMSh) was studied with the help of different process parameters viz. contact time, adsorbent dose, pH, stirring speed and other co-ions effect. Fluoride adsorption by NMSh was highly pH sensitive. Maximum fluoride was adsorbed from water at pH 5.8. Study of temperature effect on fluoride adsorption confirmed the endothermic behavior of the process. Other thermodynamic properties were also calculated and found that chemisorption was dominant with activation energy of 73.2 kJ/mol. Kinetic study revealed that pseudo second order model was followed by the adsorption process. Adsorption equilibrium was analyzed with Langmuir, Freundlich, Temkin and Dubinin–Rasdushkevich isotherm models. Results showed that the adsorption system followed both Langmuir and Temkin isotherms with Langmuir adsorption capacity of 17.24 mg/g which was compared with other adsorbents and observed that the performance of the present adsorbent is better than others. A regeneration technique was proposed in order to reuse the adsorbent for better economy of the process. Finally, a process design calculation was reported to know the amount of adsorbent required for efficient removal of fluoride from aqueous medium.