Fluoride and nitrate adsorption from water by Fe(III)-doped scoria: optimizing using response surface modeling, kinetic and equilibrium study

The Fe(III)-doped Scoria was prepared to examine its potential use as an efficient sorbent for removal of fluoride and nitrate from water. Structure and morphology of raw scoria (RS) and Fe(III)-doped scoria (FeS) were studied by scanning electron microscopy, X-ray diffraction analysis and Fourier transform infrared spectroscopy. A four-factor central composite design combined with response surface modeling (RSM) was employed for maximizing fluoride and nitrate removal based on 30 different experimental data obtained in a batch system. At optimum condition, the maximum removal of fluoride and nitrate were 78.36% and 81.4%, respectively. The kinetic of fluoride and nitrate adsorption onto RS and FeS were followed the pseudo-first-order with high determination coefficient values (R-2 > 0.997). The isotherm data of fluoride was fitted with the Freundlich model, whereas equilibrium data of nitrate are better fitted to the Langmuir isotherm model. The Langmuir maximum adsorption capacities of Fe(III)-doped scoria for fluoride and nitrate were 0.317 and 11.3 mg/g, respectively. In conclusion, Fe(III)-doped scoria is recommended as an economic and efficient sorbent for nitrate and fluoride removal from contaminated water.