Process for solubilizing residues of citrus fruit squeezing

The present invention refers to a process for the solubilization of residues of citrus fruit squeezing. In particular, the present invention refers to a process for the transformation of the exhausted citrus peels, for example those of orange, into an aqueous liquid product with low content in organic polluting load, easily purified or, alternatively, in a stable and storable product ready for all uses deriving from its composition (eg biomass). In particular, the present invention relates to a method for converting, with the aim of use or disposal, the solid waste from the orange processing industry into an aqueous liquid product. The waste, also called "citrus pulp", are the scraps of citrus fruit processing and consist mainly of exhausted peel, pulp and citrus seeds. The transformation of this solid mass of vegetable origin into an aqueous liquid allows: • disposal in the common biological waste water treatment plants, after removal of the intrinsic organic content; • storage after concentration, as well as all possible uses deriving from its composition. Then, the aim of the present invention is to provide a process for the solubilization of residues of citrus juices, in particular orange peels, hereinafter indicated with the acronym (OP), resulting from the citrus processing industry, able to overcome the limits of the technologies so far proposed. A further aim is to provide a method for solving the problems of disposal of (OP) through the implementation of an integrated process that consists in a first step of solubilization of the solid residue followed by a second step of catalytic oxidation of the substances dissolved in this solution. The first step consists in the solubilization of the orange peels by means of a basic treatment at T = 150-250 °C and the second step consists in the reduction of the pollutant load of peel previously solubilized by an oxidizing treatment in the presence of oxygen and of heterogeneous catalysts in bulk or supported on an inert support based on manganese and cerium (MnO2-CeO2, MnO2-CeO2-AC, etc.),at a temperature between 150 ° C and 240 ° C and an oxygen pressure between 9-27 bar. The twofold purpose of the process for the solubilization of citrus fruit juice residues of the invention is to convert the orange peel into a liquid aqueous product and subsequently to reduce its organic load in order to make such wastewater more suitable for disposal in sewage treatment plant. As an alternative the process can be stopped at the end of the first phase in which the transformation of the solid peel is realized in a water solution more easily manageable with respect to the starting solid. This solution, characterized by a low decrease of the initial organic content, can be used as biomass for the production of biogas and biofuels. Moreover, if subjected to concentration by the current evaporators, gives rise to a stable product easily storable.