Abstract
Waste of Phosphoric acid industry, which called phosphogypsum consists of 65% gypsum, 25% water and 10% impurities. Phosphogypsum can only be used up to 15% and the rest is thrown away. The objective purpose of this study is to reduce the content of P2O5 and F using best variable CaO and stirring during coagulation process, flocculation and sedimentation. The method of this experiment is conducted by using the ratio of phosphogypsum and variable distilled water 1:1, 1:2 and 1:3, and then put it into a jar test using the variable stirring of 100 and 150 rpm. Then 11, 12 and 13 gram CaO and 50 ml distilled water is added as variables for coagulation – flocculation process. pH is kept at 6 by adding 4% NaOH. Polyalumunium chloride (PAC) 0.1% as much as 1.75 mg/l is added into the mixture and stirred at 30 rpm for 20 minutes. The separation of P2O5 and F, is done by the sedimentation process. These experimental results show that variable 1:2 (w/v), 12 gram CaO and 150 rpm stirring able to reduce fluoride and P2O5 up to 98.5% and 50% from phospogypsum.
Highlights
Phosphogypsum (PG) is a byproduct of industrial phosphoric acid and gypsum consists of 65-70% gypsum,25-30% water and 5-10% water impurities, ie phosphoric acid and its salts, hydrofluoric acid and its compounds, R2O3 (Al2O3 + Fe2O3), Quartz, apatite, alkali, organic matter, and others
Some of dirt as P2O5 and F can be found in three different forms, namely in the gypsum crystal surface as water-soluble compounds (H3PO4, Ca (H2PO4)2
This study aims to reduce the content of P2O5 and F impurities especially in phosphogypsum by performing physical and chemical treatment and determine the effect of such treatment on the set parameters
Summary
Phosphogypsum (PG) is a byproduct of industrial phosphoric acid and gypsum consists of 65-70% gypsum ,25-30% water and 5-10% water impurities, ie phosphoric acid and its salts, hydrofluoric acid and its compounds, R2O3 (Al2O3 + Fe2O3), Quartz, apatite, alkali, organic matter, and others. Some of dirt as P2O5 and F can be found in three different forms, namely in the gypsum crystal surface as water-soluble compounds (H3PO4, Ca (H2PO4)2 H2O, H2SiF6), gypsum crystal lattice (solid solution CaHPO4 2H2O , SrSO4 or Na2SiF6) and insoluble compounds, namely apatite and quartz (Al-Hwaiti, 2015). Phosphogipsum can be used for industrial purposes and infrastructure needs, one of which is cement. If used in the manufacture of cement, such impurities can disrupt mechanical properties by altering the gypsum morphology that will harden. Various methods have been suggested to reduce the reactivity of the impurities., including washing simple with water or filter wash solution from phosphogypsum the heating hemihydrate anhydrite followed by washing or neutralization with Ca(OH) or the base material, and treating phosphogypsum with a mixture of Sulfuric acid and silica or hot ammonium sulfate solution (Singgh, 1992)
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