Wet synthesis of high purity crystalline urea phosphate from untreated Moroccan industrial phosphoric acid

Abstract

The phosphorus-nitrogen fertilizer family improves the availability of phosphorus and nitrogen for efficient crop growth. Urea phosphate 17-44-0 (N-P 2 O 5 -K 2 O%) is considered as a binary fertilizer characterized by its high purity and it is easily soluble in water. In addition, urea phosphate can be used in other fields as a high-quality food additive, finishing agent for metals and fermentation food. As a fertilizer, it is suitable for alkaline soils. In this work, a new process for the synthesis of urea phosphate by the wet route is developed. It consists in directly producing crystalline urea phosphate by the chemical reaction between Moroccan industrial phosphoric acid (54 % P 2 O 5 ) and solid urea (46 %). The synthesis is carried out by mixing the solid urea with a stoichiometric amount of untreated Moroccan industrial phosphoric acid. The chemical reaction is complete for optimal conditions which are a temperature of 50 °C and a duration of 90 min. After cooling, the urea phosphate crystals are formed without any additional treatment and are easily recovered. Analysis of the residual liquor after recovery of the urea phosphate crystals confirms that the majority of impurities which may be harmful to the environment pass into the liquid phase