Study on Controlling the Dissolution of Calcium Dihydrogen Phosphate Using Ternary Phase Diagrams to Improve the Production Process of Phosphoric Acid

Abstract

Phosphogypsum is a solid byproduct in the production of phosphoric acid in the traditional sulfuric acid process, and its output has caused a huge economic and environmental burden. In order to avoid the production of phosphogypsum and efficiently produce phosphoric acid, a novel study on the decomposition of phosphate ore by phosphoric acid was carried out. The influence of parameters on the decomposition efficiency of phosphate ore were explored systemically using response surface methodology (RSM). The concentration of phosphoric acid was the most important factor affecting the decomposition efficiency of phosphate ore in the phosphoric acid process, followed by reaction temperature and reaction time. The dissolution behavior of Ca(H 2 PO 4 ) 2 was studied using phase diagrams of ternary systems of P 2 O 5 −CaO−H 2 O. When the ratio of the practical doses of phosphoric acid to the theoretical/ stoichiometric doses of phosphoric acid (Ratio P/T ) was 3.3 and the phosphoric acid concentration (calculated as P 2 O 5 ) was 35%, the decomposition efficiency of phosphate ore reached 98.34%, and the proportion of Ca(H 2 PO 4 ) 2 dissolved in the leach liquor reached 98.54%. A high proportion of dissolved Ca(H 2 PO 4 ) 2 reduced the loss of phosphorus, and the generation of clean gypsum was obtained under these experimental conditions. Clean gypsum produced by the phosphoric acid process is regular long columnar crystal and has few impurities. This study provides an efficient strategy for the production of phosphoric acid by controlling the dissolution of Ca(H 2 PO 4 ) 2 , while avoiding the generation of phosphogypsum.

Viscosity Formation Mechanism and Viscosity Reduction Strategy for Ammoniated Slurry of Nitrophosphate Fertilizer

“…Phosphoric acid can be extracted from the digestion solution by solid–liquid separation. The process of sulfuric acid is simple, but it is difficult to deal with the mass solid waste phosphogypsum which brings increasingly serious environmental harm . The formation of phosphogypsum can be avoided by using nitric acid to decompose phosphate rock, and the reaction is shown in eq . , Water-soluble calcium nitrate is normally separated by freezing crystallization in the formation of valuable Ca­(NO 3 ) 2 ·4H 2 O.…”

Phosphorus recovery from phosphonate-contaminated wastewater by nonthermal plasma treatment prior to adsorption on granular iron-coated sand

“…However, excess phosphorus content in water bodies can lead to aquatic plant flourishing and eutrophication [1][2][3]. At present, the production of phosphorus is mainly obtained by decomposing phosphate ore, but this process is energy-intensive, environmentally harmful, and costly [4]. Removal and/or recovery of phosphorus from wastewater is regarded as a promising strategy to lower the burden of phosphorus production and prevent aquatic eutrophication.…”