Synthesis and characterization of iron-PVA hydrogel microspheres and their use in the arsenic (V) removal from aqueous solution

We adapt the sol–gel process to synthesize monodisperse metallic iron (80–155 μm), iron oxide (117–200 μm), xerogel (130–224 μm), and -PVA hydrogel (300–600 μm) microspheres. According to the Mössbauer analysis, iron xerogel and -PVA hydrogel microspheres have superparamagnetic nanoparticles of ferrihydrite (65%) and goethite (35%). Maximum arsenic (V) adsorption (87.18 mgAs/g, ⩾99.40% at t ⩾ 4 h) on the iron-PVA hydrogel microspheres takes place in the pH range 2–5, in accordance with the Langmuir model. In this adsorption, chemisorption mechanism is predominant, but the intra-particle diffusion model suggests that the adsorption mechanism is more complex. Desorption can be done with 0.011 M NaOH solution, reaching an efficiency of 74.64%. Our sol–gel process is effective in maintaining the iron particles monodisperse and with nanometer dimensions (⩽20 nm) inside the iron-PVA hydrogel microspheres.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Monodisperse iron microspheres were produced by the sol–gel process. ► Mössbauer spectroscopy was used to characterize the iron microspheres. ► Metallic iron microspheres could be produced with an average diameter ⩾80 μm. ► Iron oxide microspheres with a mesoporous structure (105 m2/g) were obtained. ► Iron-PVA hydrogel microspheres showed high As(V) uptake (87.18 mg/g).