Synthesis and Physicochemical Characterization of Pure Monoammonium Phosphate (MAP) from Industrial Fertilizer

Monoammonium phosphate (MAP) is produced from crude phosphoric acid which contains Fe (Ⅲ), Al (Ⅲ) and Mg (Ⅱ) ions. In general, the fertilizers MAP was obtained by including various heavy metal micronutrients (Co, Cu, Fe, Mn, Mo, Ni and Zn), fluorine and heavy metals considered toxic (Al and Cd) in. The long-continued application of phosphate fertilizers (MAP) and their by products can redistribute and elevate heavy metal and fluorine concentrations in soil profiles. However, they are subsequently transferred into the human food chain because of their availability to plants, mainly in acid soils. Thus, it is important to eliminate the impurities in MAP. Purified MAP is three times more expensive than the same product before purification and is commonly used in a number of applications such as flame proofing (building materials, pulp and paper) and agriculture. Purified MAP is a key ingredient in specialty all-soluble dry fertilizers, waste water-nutrient for biological purification, fermentation and biotechnology-nutrient. The procedure for purification of industrial MAP is a recrystallization, by using several mixtures of solvents. The physicochemical characterization of this fertilizer upstream and downstream from the purification, through spectroscopic analyses and chemical analyses, shows that recrystallization can eliminate impurities. The physicochemical properties of the purified MAP obtained by recrystallization are comparable to those of the MAP obtained with a pure phosphoric acid.