A heterogeneous advanced Fenton process (AFP) based on the use of zero valent iron (ZVI) has been investigated for the treatment of a real industrial wastewater, generated from a drug manufacturing plant. The effluent consists of a complex mixture of organic substances which are refractory to conventional treatments. The concentration of ZVI and oxidant (H2O2) were studied. The use of moderate concentrations of oxidant and ZVI commercial catalyst led to total organic carbon (TOC) reductions of 70% and 55% of diluted (TOC0 0.1 g L-1) and as-received pharmaceutical wastewater (TOC0 5 g L-1), respectively, with a remarkable enhancement of the biodegradability in all cases. Apart from that, it was demonstrated a notable effect of the magnetic agitation system (speed and size of the stir bar) on the catalytic performance of the ZVI/H2O2 system. The aggregation of ZVI particles on the magnetic stir bar surface, due to its intrinsic magnetic properties makes that the availability of active ZVI particles was somewhat controlled by the size of the magnetic stir bar. For the best operation conditions, a higher TOC conversion was accomplished during the first minutes of reaction, slowing down afterwards, probably due to passivation of the ZVI catalyst. The different stratified layers of iron/hydrous oxides covering the metallic ZVI surface formed under the different reaction conditions were studied by XRD, TPR and XPS characterization techniques. (C) 2015 Elsevier B.V. All rights reserved.