## 1 Introduction  
The uses of phthalates as plasticizers are widely spread and growing rapidly in the manufacture of various PVC products, textiles, toys as well as medicinal products [1; 2; 3; 4]. Moreover, they can be applied in various industries such as insect repellents, propellants and many cosmetics manufacture [3; 4]. Due to its low cost production and its versatile chemical properties, phthalates attracted innumerable industrialists towards plastic-based productions throughout the world [3; 5]. Being widely used as plasticizers and not bounded to polymer mesh, they easily pass from plastic products to surrounding environments and consequently pollute water, soil, air and last but not least food products [6; 4; 7; 8; 9]. Rainfall transfers phthalates and phthalate esters in the atmosphere, which lead to their accumulation in water depending on geographic locations [8]. Discharge of phthalate esters into the atmospheric and aquatic regions has therefore increased as a reason of urbanization. Using agricultural plastics has enormously caused contamination to the soil in rural areas [10]. Hence, phthalates are very toxic, carcinogenic and can cause serious diseases in human beings [9; 11; 12]. They are considered as toxic environmental priority pollutants and endocrine disruptor chemicals [7; 10; 13; 14]. In addition, it has toxic effects on the liver, kidney, and reproductive organs and act partly as endocrine disrupting agents [5; 12; 14; 15]. Thus far, a number of phthalates have been reported such as Dibutyl Phthalate (DBP), Diethyl Phthalate (DEP), Diethyl Hexyl Phthalate (DEHP), Diallyl Phthalate (DAP) and identified in environmental water samples. DAP selected for evaluation in the current work has a chemical structure given in Figure 1. This compound can pause environmental and health problems [16; 17]. DAP is largely used as plastilizers in PVC plastic containers, packaging and medical devices. It can be released during longtime storage in warm conditions and contaminate water bodies [10; 11; 12; 13; 14; 15; 16; 17]. Nevertheless, despite its high toxicity, no valuable information on the decontamination of wastewaters containing DAP exists. Advanced oxidation processes (AOPs) are water treatment methods generating powerful oxidants mainly hydroxyl radicals (HO\({}^{\bullet}\)). The Fenton process, considered a cost-effective AOP is largely utilized in industrial wastewater treatment plants [18; 19; 20]. In Fenton oxidation, the reaction between hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) and ferrous ions (Fe\({}^{2+}\)) promotes the formation of \({}^{\bullet}\)OH radicals in an acidic medium (Equation (1)). \[\mathrm{Fe}^{2+}+\mathrm{H}_{2}\mathrm{O}_{2}\rightarrow\mathrm{Fe}^{3+}+ \mathrm{HO}^{\bullet}+\mathrm{OH}^{-} \tag{1}\]  
Acidic conditions are necessary to scavenge the hydroxide ions formed in reaction (Equation (1)) to avoid the precipitation of Fe(OH)\({}_{3}\). In addition, the doses of Fe\({}^{2+}\) and H\({}_{2}\)O\({}_{2}\) should be carefully adjusted to make Fenton oxidation highly effective. Recently, the development of new Fenton and Fenton-like catalysts for more efficient decomposition of H\({}_{2}\)O\({}_{2}\) into HO\({}^{\bullet}\) radicals would result in the large industrial application of Fenton oxidation for environmental remediation and water purification [21; 22; 23]. This work aims to investigate the degradation of DAP in aqueous solutions by Fenton oxidation. The effects of different experimental parameters such as pH, H\({}_{2}\)O\({}_{2}\) and iron doses, iron source on the mineralization efficiency and oxidative degradation of DAP aqueous solutions were studied. The absolute rate constant for the reaction between the DAP and hydroxyl radicals was determined by the competition kinetic method, using benzoic acid as a reference. Aromatic and aliphatic byproducts of DAP oxidation by the Fenton process were examined by high performance liquid chromatography (HPLC) analysis and total organic carbon (TOC) measurement.