Dissolution behavior of nutrient elements from dephosphorization slag in the weakly acidic solution

Abstract

Dephosphorization slag is primarily composed of CaO-SiO 2 -FeO-P 2 O 5 slag system. As it contains abundant valuable components, dephosphorization slag is considered a potential material to restore the degraded acid soil. To efficiently supply Ca, Si, Fe, and P elements for acid soil, the dissolution behavior of dephosphorization slag with high P 2 O 5 content in the weakly acidic solution was investigated. It was found that the existence of citric acid could significantly promote the dissolution of slag in the aqueous solution. Most of the Ca, Si, and P was dissolved from slag at pH 5, and the Fe dissolution ratio reached 36.9%. In this case, the precipitation of Fe 3 (PO 4 ) 2 •8H 2 O was suppressed, and the majority of C 2 S-C 3 P solid phase and matrix phase was dissolved while wustite remained in the residue. The dissolution ratios of main elements from slag decreased dramatically as the pH increased. Only in the weakly acidic solution, it could make full use of dephosphorization slag, and large amounts of nutrient elements were simultaneously supplied. The dissolution ratios of nutrient elements decreased with the increase in particle size. The dissolution kinetics of slag in the citric acid solution followed the shrinking core model.