Chemical and Mechanical Factors on Phosphorus Dissolution Behavior from P-concentrated Slag

Since it has been urgently demanded to secure the secondary phosphorus resources domestically in addition to the establishment of a stable supplying path of phosphate ore from overseas, the recovery of phosphorus from steelmaking slags is attracting attention. The phosphorus-enriched slag obtained by dephosphorizing the high phosphorus hot metal, which was prepared by the reduction of conventional steelmaking slag, is thought to be useful as a raw phosphorus resource. It was reported in our previous paper that phosphorus can be effectively separated from P-enriched slag by the citric acid leaching method. In this study, the effects of citric acid concentration in solution, solution temperature, slag/solution mass ratio, and P-enriched slag composition on phosphorus dissolution behavior were additively investigated. A phosphorus dissolution from the P-enriched slag was significantly promoted by increasing the citric acid concentration in solution. However, even if the solution temperature was increased during leaching, the speed and ratio of phosphorus dissolution from the P-enriched slag did not change. With increasing the slag/solution mass ratio, the concentration of each element in solution increased, while their dissolution ratios decreased. Furthermore, the phosphorus dissolution ratio was suppressed in the case of the P-enriched slag with low CaO and high P2O5 concentrations. Appropriate conditions for various factors affecting phosphorus dissolution behavior from P-enriched slag were discussed.