Enhancement of the Bioremediation of Pyrene-Contaminated Soils Using a Hematite Nanoparticle-based Modified Fenton Oxidation in a Sequenced Approach Sahand Jorfi a,b , Mohammad Reza Samaei c , Reza Darvishi Cheshmeh Soltani d , Amirreza Talaie Khozani e , Mehdi Ahmadi a,b , Gelavizh Barzegar f , Neda Reshadatian g , and Nasim Mehrabi g a Environmental Technologies Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; b Department of Environmental Health Engineering, School of Health, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; c Department of Environmental Health Engineering, School of Health, Shiraz University of Medical Sciences, Shiraz, Iran; d Department of Environmental Health Engineering, School of Health, Arak University of Medical Sciences, Arak, Iran; e Department of Civil Engineering, Jami Institute of Technology, Isfahan, Iran; f Department of Environmental Health Engineering, Behbahan Faculty of Medical Sciences, Behbahan, Iran; g Master of Environmental Health Engineering, Department of Environmental Health Engineering, School of Health, Ahvaz, Iran ABSTRACT The effect of modified Fenton oxidation using synthesized hematite nanoparticles and sodium pyrophosphate as a chelating agent was investigated for the pretreatment of pyrene-contaminated soil in a sequence with bioremediation. Synthesized hematite nanoparticles comprised hematite according to X-ray diffraction (XRD) analysis, with particle sizes ranging between 28 and 55 nm. Three pyrene-degrading bacteria, Bacillus cereus, Acidovorax wohlfahrtii , and Bacillus thuringiensis, were isolated from hydrocarbon-contaminated soil and used as inoculums for the bioremediation. A sequence of modi fied Fenton oxidation- bioremediation using a synthesized hematite nanoparticles dosage of 30 mM and H 2 O 2 concentration of 300 mM significantly enhanced the pyrene removal rate to 96%, 87%, and 82% compared to 88%, 59%, and 37%, which were obtained during the bioremediation alone for synthetically fresh, aged, and naturally contaminated soil with initial pH 7, respectively. The results of kinetic studies indicated that modi fied Fenton oxidation of pyrene-contaminated soil was best fitted with a pseudo-first order kinetic model. Consequently, a sequence of modified Fenton- bioremediation can effectively remediate polycyclic aromatic hydrocarbon- contaminated sites in a shorter reaction time than bioremediation alone. KEYWORDS Soil contamination; Pyrene; modified Fenton oxidation; hematite-nanoparticles; bioremediation Introduction Polycyclic aromatic hydrocarbons (PAHs) are persistent contaminants resulting from natural or anthropogenic resources. Industrial effluents, petroleum product spillages, and incomplete com- bustion of fossil fuels have led to PAHs accumulation in the environment during past decades CONTACT Sahand Jorfi sahand369@yahoo.com Environmental Technologies Research Center, Ahvaz Jundishapur University of Medical Sciences, 67396-64578 Ahvaz, Iran. Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/bssc. © 2017 Taylor & Francis Group, LLC SOIL AND SEDIMENT CONTAMINATION 2017, VOL. 26, NO. 2, 141–156 http://dx.doi.org/10.1080/15320383.2017.1255875