PROCESS FOR TREATMENT OF PHOSPHATE BY LEACHING WITH PHOSPHORIC ACID

Abstract

The invention relates to a treatment process for reducing the concentration of metallic elements, particularly heavy metals, and especially cadmium, in phosphate rock, comprising the following steps: • Leaching the phosphate rock with concentrated phosphoric acid, followed by solid-liquid separation and washing and drying of the treated phosphate. • Demetallization of the phosphate rock. • Regeneration and recycling of the phosphoric acid in the process or other application. The various characteristics of the process include: The use of concentrated phosphoric acid, with a specific gravity greater than 1000 g / l, possibly greater than 1060 g / l. A leaching treatment carried out at a temperature between 10 and 80°C, with a residence time between one minute and four hours. Filtration or decantation to separate the phosphate rock from the leachate. Washing the phosphate rock to remove traces of adsorbed leachate. Regeneration of the acid. Phosphoric acid from leachate, a mixture of leachate and acid water from washing phosphate rock, or a mixture of leachate and acid water from subsequent washing of phosphate rock and gypsum. The regeneration stream reacts with an acid, preferably sulfuric acid. The regeneration temperature is below 90°C. The concentration of the acid used for regeneration is between 1 and 10 M, with better performance between 2 and 6 M. The regenerated phosphoric acid is separated from the precipitate, followed by washing the precipitate. The regenerated phosphoric acid is recirculated to the leaching stage, with the possibility of concentration or dilution as required.