Investigating sodium sulphate as a phosphate depressant in acidic media

• Sodium sulphate was used, as a phosphate depressant, using oleic acid as a collector.
• Experimental design was used to determine the main controlling factors.
• pH and solid % play a vital role in achieving a good concentrate grade and recovery.
• A concentrate containing 32% P2O5 with a recovery exceeds 84% was achieved.

Reverse flotation is a commonly used technique for separating carbonate impurities from sedimentary phosphate ores using fatty acids collectors. Although, oleic acid represents one of the famous fatty acids that have been used as a collector in phosphate flotation circuits, it is a non-selective collector. Therefore, the selection of depressing agent is the most controlling factor. In this study, sodium sulphate was used as a phosphate depressant. The role of sodium sulphate in separating phosphate from its impurities and producing an acceptable concentrate grade for phosphoric acid production (equals or more than 30% P2O5) was evaluated using augmented factorial design. The collector dose, depressant dose, solid %, flotation time and pH were chosen as main affecting variables. The results showed that the addition of sodium sulphate improves the phosphate grade and recovery especially at highly acidic pH. They showed also that the solid % and the pH represent additional key factors in achieving a good grade concentrate due to their role in controlling the amount of ionic species in the flotation pulp. A concentrate contains >32% P2O5 was obtained with a recovery ranges from 84% to 87%.

Phosphate reverse flotation by oleic acid in presence of sodium sulphate was tested using statistical design of experiments. The solid % and pH were found to be the most significant factors. A concentrate containing 32% P2O5 with a recovery >84% was achieved at slightly acidic pH.Figure optionsDownload as PowerPoint slide