The Fenton process involves the combination of hydrogen peroxide and iron salts (II) as catalysts to generate hydroxyl radicals by the catalytic decomposition of H2O2 in acidic medium (Walling, 1975). The Fenton process has been extensively studied (more than 1000 references in Web of Science), and the improvements of this process have been based on the use of heterogeneous catalysts instead of the homogeneous ones (over 300 references in Web of Science), in order to prevent the recovery of the homogeneous catalyst (iron II or III) at the end of the process, making it a more environmentally and efficient process.In the Fenton process, H2O2 is the main reagent and represents the main operating cost. One of the problems involving the use of H2O2 in oxidation processes is related to its handling and storage, as it is a highly reactive compound and it can be exothermically decomposed by heating or by contamination, especially at high concentrations. Currently, the commercial production of hydrogen peroxide (Riedl-Pfleiderer process) involves the catalytic hydrogenation of an alkylantraquinone to its corresponding hydroquinone, followed by treatment with oxygen to produce H2O2 and the original anthraquinone (Goor et al, 1989). A potentially more economical alternative would be its direct formation from H2 and O2. This has been the subject of numerous studies in recent years, analyzing the effectiveness of various catalysts and operating conditions (more than 50 references in Web of Science). In this sense, in Spain, the research groups of García Fierro et al. and García Serna et al. (Blanco-Brieva et al., 2010a, 2010b; Moreno et al., 2010) have been working in the direct synthesis of hydrogen peroxide using different Pd catalysts. However, two of the drawbacks presented by these systems are the need to work at very high pressures due to the low solubility of hydrogen, or in the presence of other co-solvent; and its dangerousness, as it is necessary to work in O2/H2 ratios out of the explosion limits (5:1 to 20:1, meaning that it should be introduced substantial quantities of nitrogen for security reasons).In order to avoid these problems, Choudhary et al. (2005, 2007) indicated that hydrazine and hydroxylamine can be used as hydrogen sources for production of hydrogen peroxide leading to a remarkable selectivity toward hydrogen peroxide using Pd/Al2O3 catalyst. However, this system utilizes hydrazine or hydroxylamine, classified as toxic compounds. It also requires addition of halide ions as prerequisite to proceed. Besides, presence of a mineral acid creating an extremely low pH is of importance in the case of hydrazine in order to stabilize hydrogen peroxide. In this sense, in the URV group that co-presents this project, the decomposition of formic acid as a source of hydrogen to obtain hydrogen peroxide (Yalfani et al., 2008) using Pd/Al2O3 catalyst has been studied. According to our knowledge no result concerning this route for the generation of hydrogen peroxide had been previously published. As a conclusion of this work, we attained a new route to produce hydrogen peroxide with several advantageous properties including simplicity, cleanness and most importantly environment-friendly. It performs at ambient conditions and in aqueous medium.Furthermore, the use of in situ generated H2O2 in oxidation processes would open new possibilities, for which the in situ generation should be performed in operating conditions compatible with those of the subsequent oxidation reactions. In this sense, very interesting is the paper of García Fierro et al. (Blanco-Brieva et al., 2008), related to the production of propene oxide based on the direct synthesis of hydrogen peroxide. This paper reports, clear evidence that hydrogen peroxide generated in situ can be used to oxidize some organic substrates. Taking this into consideration, in situ hydrogen peroxide generation could be used for the removal of organic pollutants in water. The oxidation of Calmagite dye has been studied by in situ generated H2O2 from hydroxylamine and O2, using a homogeneous catalyst of manganese (II) ions (Sheriff et al., 2007).Recently, the URV group has been working in the in situ generation of hydrogen peroxide using different hydrogen sources like formic acid, hydrazine, hydroxylamine and direct hydrogen, using heterogeneous catalysts. We have studied the in situ generation of hydrogen peroxide to be applied in a Fenton process, using heterogeneous catalysts, for the removal of several organic contaminants like phenol, chlorophenols, clofibric acid, etc. This is an original study in which the URV group is pioneer in Spain as well as in the rest of the World. Thus, the URV group has developed a Pd-based catalytic system for the in-situ generation of hydrogen peroxide, from formic acid and oxygen (Yalfani et al., 2008). Afterwards, the URV group has applied this technology in the oxidation of organic compounds by a Fenton-like process for wastewater treatment: Phenol was used as model compound in order to test the feasibility of this system. Initially, a semi-heterogeneous catalytic system was used (Pd/alumina + Fe(II) in solution). The new catalytic process showed to achieve higher mineralization degrees than the conventional Fenton system, the catalytic system being stable and environmentally friendly (Yalfani et al., 2009). In a second stage, the catalytic system was completely heterogeneized, incorporating Fe to the solid catalyst forming Pd-Fe alloy nanoparticles (Yalfani et al., 2010). Recently, the URV group has studied different bimetallic catalysts and study their efficiency in the degradation of recalcitrant organic compounds in aqueous solution using different hydrogen sources like hydrazine and hydroxylamine as well the study of alloy formation of bimetallic nanoparticles in different supports (see Yalfani et al. 2011 and Contreras et al., 2011). In these papers the effectiveness of this system for the degradation of several organic compounds such as phenol, chlorophenols and clofibric acid in aqueous solutions at middle conditions has been demonstrated. The degradation and mineralization of the organic compounds, using this technology, is much better than the obtained using conventional Fenton process. However, from an economic point of view, the main problem this technology currently faces is the high noble metal content of the catalyst (>1 wt%). Therefore, in the present project continue researching in this promising technology, in order to be able to transfer it to the industry, will be pursued. In this sense, exploring the possibility of developing Pd and Pd/Fe nanoparticles to incorporate to solid supports and diminish the amount of noble metal needed to produce catalytically the hydrogen peroxide is an aim of the project. This project will also bring the opportunity to validate this technology with real industrial wastewaters.Furthermore, another objective is the opening a new line of research that combines the in-situ generation of hydrogen peroxide with photo-Fenton process, in order to check the efficiency of this new process in the treatment of wastewaters. From our best knowledge there are no studies about this subject yet. Finally, in this project the possibility of exploring the in situ photo-generation of H2O2 and its application in the photo-Fenton process will be investigated. In this case we will use TiO2-based catalysts (prepared by the UEX group) incorporating Fe or Cu active sites to promote the activation of the in-situ H2O2 to be tested in the in situ photo-generation of H2O2 and its application in the photo-Fenton process. In case that the efficiencies achieved are not very high, the effect of the addition of Pd to the catalyst and the presence of a soluble hydrogen source will also be studied.