We adapt the sol-gel process to synthesize monodisperse metallic iron (80-155 mu m), iron oxide (117-200 mu m), xerogel (130-224 mu m), and -PVA hydrogel (300-600 mu m) microspheres. According to the Mossbauer 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 nanometerdimensions (<= 20 nm) inside the iron-PVA hydrogel microspheres. (C) 2012 Elsevier B.V. All rights reserved.