We adapt the sol–gel process to synthesize monodisperse metallic iron (80–155μm), iron oxide (117–200μm), xerogel (130–224μm), and -PVA hydrogel (300–600μm) 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⩾4h) 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 0.011M NaOH solution, reaching an efficiency of 74.64%. Our sol–gel process is effective in maintaining the iron particles monodisperse and with nanometer dimensions (⩽20nm) inside the iron-PVA hydrogel microspheres.