Optimization of Phosphogypsum By-Production Using Orthophosphoric Acid as Leaching Solvent with DifferentTemperatures and Leaching Time Periods

Abstract

Phosphoric acid production generates unavoidable calcium sulfate by product (i.e. phosphogypsum (PG)) that is usually disposed either within a nearby located gypsum stacking system. However nowadays this type of industry has been faced with two main problems; these are the formation of huge stockpiles of phosphogypsum that affects the environment due to the presence of harmful radiations that is emitted from the uranium. In addition it contains P2O5>1.0 wt% and fluorine >0.18 wt%, which makes it not suitable for the cement industry. At the same time consuming large quantity of expensive sulphuric acid that becomes a hazardous waste material too. The production ratio of PG verses marketable P2O5 as acid in the world is high as much as 5 tons of PG are produced for each ton of P2O5; in Jordan the ratio is around 5.0 – 5.3 ton of PG / ton of P2O5 produced depending on the phosphate rock composition, which means a huge amount of PG will accumulate at the Fertilizer plant in Aqaba. The major advantages of using orthophosphoric acid as leaching solvent is the decreasing ratio of the residual materials verses marketable P2O5to be589 kg /ton of P2O5 produced. These results were obtained by utilizing the wet agitation leaching technique, compared with 5.0 – 5.3 ton of disposed PG/ton of P2O5produced by Jordan Phosphate Mines Company Ltd., (JPMC). However, this alternative technique resulted in lowerP2O5 extraction, but decrease in bulk of the residue. The disadvantage is the higher dissolution of calcium phosphate and thus considerable calcium well remain in solution.