The effect of partial acidulation of Asphord Rock Phosphate with Phosphoric Acid towards its effectivness

Treatment of rock phosphate with acid, is a promising technique to increase phosphorus release from rock phosphate. That is why in this research,two samples of rock phosphate from Asfordi mine were prepared for comparison. One of them was Raw and the other was concentrated. Solubility tests were done for measuring amount of water soluble phosphorus, citrate soluble and none citrate soluble phosphorus in the treatments. Samples of Raw rock phosphate and concentrated rock phosphate were treated with Phosphoric acid in three different concentrations (10,20,40%) with two different temperatures (25 & 75'c) in three replications. To evaluate the effect of different periods of time (1,10,20,40 days) on dissolution of rock phosphate, samples were incubated for the mentioned times. Analysis of data performed with MSTATC software. The results showed that the effects of four treatments on water soluble phosphorus and citrate soluble and none citrate soluble phosphorus, were significant. The acid concentration in 40% phosphoric acid increased water soluble phosphorus and none citrate soluble phosphorus more than 20% and 10% concentration but the amount of citrate soluble phosphorus in the samples which treated with (10%) concentrations of phosphoric acid was more than other treatments. The effect of rock phosphate on increasing water soluble phosphorus and none citrate soluble phosphorus, in concentrated rock phosphate was more than Raw rock phosphate but citrate soluble phosphorus in Raw rock phosphate was more than concentrated rock phosphate. In this research, both of the temperatures have the same effect on phosphorus dissolution in all treatments. The amount of water soluble phosphorus, in one day after treatment was maximum and with increasing temperature and time intervals, the amount of water soluble phosphorus, decreased but the amount of citrate soluble phosphorus in 10 day from treatment were maximum and with increasing temperature and time intervals, increased. The amount of none citrate soluble phosphorus in 40 day from treatment were maximum and with increasing temperature and time intervals, decreased significantly. Keywords: rock phosphate, phosphoric acid, acidulation