Enhanced degradation of nonylphenol at neutral pH by ultrasonic assisted- heterogeneous Fenton using nano zero valent metals G.M.S. ElShafei a,⇑ , F.Z. Yehia b , Gh. Eshaq b , A.E. ElMetwally b a Taibah University, College of Science, Chemistry Department, AlMadina Almounawara, Saudi Arabia b Department of Petrochemicals, Egyptian Petroleum Research Institute, Nasr City, Cairo, Egypt article info Article history: Received 28 May 2016 Received in revised form 15 January 2017 Accepted 15 January 2017 Available online 18 January 2017 Keywords: Fenton-like Ultrasonic Nonylphenol Degradation Zero valent metals AOP abstract The nano zero valent metals (nZVMs) of Fe, Cu, and Ni were prepared and examined in degradation of nonylphenol (6 mg L 1 ) by ultrasonic (20 kHz) assisted-Fenton-like process at the neutral pH, and the room temperature. The experiments were performed to investigate effects of irradiation time, H 2 O 2 dosage, and pH. In presence of 1.0 g L 1 of a solid catalyst, and 10 mM H 2 O 2 the degradation was com- plete after 15 min of sonication in presence of Fe 0 and Cu 0 ; while Ni 0 needed 25 min to do the same effect. Degradation is enriched in the presence of the catalyst and hydrogen peroxide, due to enhanced produc- tion of hydroxyl radicals at interfacial regions between cavitation bubbles and solid particles. Particle size and specific surface area of used catalysts have a major role. Results of total organic carbon removal sup- ported the conclusion that the degradation of nonylphenol takes place through initial attack of the formed hydroxyl radicals to the side chain that decomposes in the form of gaseous products. Ó 2017 Elsevier B.V. All rights reserved. 1. Introduction Nonylphenols, a kind of substances that cause endocrine system disruption, are widely used as emulsifiers, detergents, surface modifiers, and flotation/dispersing agents in industry [1,2]. Due to the extensive use of nonylphenol, it reaches sewage treatment works in substantial amounts [3]. Hence, the major source of nonylphenol in the environment is the discharge of effluents from sewage treatment works [4]. Nonylphenols could evaporate from water into atmosphere and exist in the form of gaseous or particle state (aerosol) that would return again to water, soil and sediment by dry and wet deposition [1]. Nonylphenol is a mixture of iso- mers; the dominant component (about 90%) is 4-nonylphenol (4- NP) [5]. 4-NP is a bioaccumulative in aquatic organisms at low con- centrations [6,7] and can cause adverse effects on the endocrine system via, for example, binding to human serum albumin [8,9]. Currently, the EPA has accepted the risks of nonylphenol and has prepared a guideline for ambient water quality that recommends nonylphenol concentrations in freshwater to be below 6.6 lgL 1 and in saltwater below 1.7 lgL 1 [10]. Due to its refractory and toxic nature, and the relatively low efficiency of the current reme- diation processes, the advanced oxidation processes (AOPs), based on the generation of highly reactive species such as hydroxyl rad- icals (OH Å ), appear to be a promising alternative for the removal of such a substance. The most widely studied AOPs include; photo degradation [11] heterogeneous photocatalytic oxidation [12], Photo degradation by simulated sunlight [13], simulated solar UV [14], gold nanoparticles/rutile titanium(IV) oxide Plasmon photo- catalyst [15] treatment with ozone (often combined with H 2 O 2 , UVA, or both) [16,17],H 2 O 2 /UV systems [18], Fenton [19] and photo-Fenton type reactions [20]. Great attention has been paid during recent past years to the use of ultrasound as an effective technology for wastewater treat- ment [21,22]. Implosions of the ultrasound irradiation-born cavi- ties result in local extremely high temperature and pressure that lead to the formation of reactive radicals such as H Å , HO Å and O 2 Å , in addition to the homolytic splitting of pollutant compounds. Degradation of pollutants using cavitations is based on the attack of the generated free radicals. Some of the reactions have been explained by hot-spot theory (localized generation of extremely high conditions of temperature and pressure). However, in most cases ultrasound processes result in low mineralization rate due to the refractory behavior of the oxidized byproducts [23]. On the other hand, ultrasonic irradiation provides improvements in heterogeneous catalytic systems by decreasing mass transfer limi- tations and fragmentation of catalyst into small particles that result in a higher surface area [23–26]. Moreover, the additionally generated free radical species in ultrasound systems should http://dx.doi.org/10.1016/j.seppur.2017.01.028 1383-5866/Ó 2017 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Ain Shams University, Faculty of Science, Chemistry Department, Cairo, Egypt. E-mail addresses: elshafei_gamal57@yahoo.com, gshafei@taibahu.edu.sa (G.M.S. ElShafei). Separation and Purification Technology 178 (2017) 122–129 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur