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Iron-oxide nanoparticles by the green synthesis method using Moringa oleifera leaf extract for fluoride removal

Silveira, Carole, Shimabuku, Quelen Letícia, Fernandes Silva, Marcela, Bergamasco, Rosângela
Environmental technology 2018 v.39 no.22 pp. 2926-2936
Moringa oleifera, X-ray diffraction, activated carbon, adsorbents, adsorption, desorption, endothermy, environmental technology, fluorides, iron oxides, leaf extracts, models, nanoparticles, pH, scanning electron microscopy, sorption isotherms, thermodynamics
In this work, we synthesized iron-oxide nanoparticles (NPsFeO) via a green synthesis method, using Moringa oleifera leaf extract, and evaluated its fluoride ion adsorption potential, comparing its efficiency with a commercially available adsorbent (activated carbon of bone [BGAC]). The adsorbent materials were characterized using X-ray diffraction, transmission, and scanning electronic microscopy, X-ray dispersive energy spectrometry, and N2 adsorption/desorption. The results showed that the maximum adsorption occurred in pH 7 for NPsFeO and pH 5 for the BGAC. Adsorption kinetic tests showed that the equilibrium was reached in 40 min for the NPsFeO, and 90 min for BGAC, with adsorption potential of 1.40 and 1.20 mg g⁻¹, respectively. The model that best described the kinetic data was pseudo-first-order for NPsFeO and pseudo-second-order for BGAC. The Langmuir isotherm had a better fit for both adsorbents. The thermodynamic parameters indicated spontaneous and endothermic adsorption at 30°C, 40°C, and 50°C for BGAC, and at 30°C for NPsFeO. The regeneration process showed that it is possible to reuse NPsFeO three times in the fluoride ion adsorption process. As a result of its adsorption capabilities and the shortest contact time to achieve equilibrium, the NPsFeO is a highly promising material for fluoride ion removal.