Beneficiation of calcareous phosphate rocks using dilute acetic acid solutions: optimisation of operating conditions for Ruseifa (Jordan) phosphate

Large amounts of low-grade, carbonate-rich phosphate rocks have no direct use and are rejected all over the world. In this work, dilute acetic acid solution has been used for leaching of the carbonates contained in Ruseifa (Jordan) low-grade, carbonate-rich phosphate rocks. Phosphate samples from combined soft, combined hard and blends of these two grades have been included in this investigation. Acetic acid is a weak organic acid whose salts are highly soluble in water and are easily separated from the beneficiated solid phosphate by filtration. Dilute acetic acid solution has the capability to react with the carbonates, but not with the tricalcium phosphate (TCP) itself. In this work, the effect of acetic acid concentration, liquid/solid ratio (vol./wt. basis), and reaction time, on the average increase of TCP content in the beneficiated phosphate rock have been experimentally investigated. The results of this work showed that, by this technique, it is possible to obtain a phosphate product (-9+270 Tyler) of an average TCP content of 70 to 75%, depending on the reaction conditions and the size and nature of the leached phosphate rock. The overall weight recovery was in the range of 70 to 75%. The grade of the phosphate product becomes higher if a bigger cut size, say 200#, is used.