Dissolution of Djebel Onk phosphate ore using sulfuric acid

• Phosphate rocks composition affects the quality of final products.
• Optimizing the reaction parameters, high phosphates decomposition is obtained.
• Djebel Onk phosphates are not deeply investigated.
• Djebel Onk phosphate rocks are high-grade ores with important reserves.
• The solubility studies in inorganic acids are limited.

The purpose of this study is to compare the P205 recovery of two phosphate rocks obtained by sulfuric acid attack. These phosphate rocks with different chemical composition, are extracted from the same deposit (Djebel Onk, Algeria). Experience shows that, for the two phosphate rocks, the reaction is faster during the first 20 min. For both phosphates, the P205 recovery remains almost stable after 40 min of reaction. But when the phosphates are attacked by 70 wt% of concentrated H2SO4, this rate is about 96%.By optimizing the reaction parameters, we managed to get a high decomposition of phosphates. Therefore, the maximum P205 recovery are, respectively, 96.19% for the first phosphate (65.38% BPL) and 94.46% for the second phosphate (53.75% BPL). These maximum values are obtained when the following parameters are used: (1) Sulfuric acid concentration: 96 wt%; (2) Reaction time:50 min; (3) Stirring speed: 200 rpm; (4) Phosphate particle size: 88 μm (−170 mesh).The production of phosphoric acid or the SSP (single superphosphate) requires prior knowledge of the effect of some parameters on the performance of the reaction; hence, the importance of this work for the fertilizer industry as it helps to have an idea about the behavior of this type of phosphate rock at its dissolution by sulfuric acid.