RECOVERY AND ENRICHMENT OF AQUEOUS PHOSPHATE FROM THE SLAG RELEASED BY A CHEMICAL FACTORY

Abstract

The elution behaviors of phosphate from the slag released by a chemical factory using various eluates were examined. Since this slag was covered with organic species, two pretreatment methods for the slag one the calcination of the slag and the other the trituration of the slag were employed to strip away the organic species from the slag. Since the elution rate from the pre-triturated slag was evidently greater than that from the pre-calcined slag, the elution behavior of the former was mainly examined in the present study. For the efficient elution of phosphate from the slag, the use of 1M HNO3 as an eluate and 30 min of trituration time were suitable. Unfortunately, together with the elution of phosphate from the slag, some cationic species were simultaneously eluted. In the present study, the removal behavior of iron cation, which was a main contaminant in the slag, using calcium hydroxyapatite (CaHAp) was also examined. Even when the solution obtained by the elution of the slag was employed for the removal of Fe using CaHAp, the Fe could be favorably removed from the solution. Results from the present study suggests that unused phosphate in slag is a potential source of raw material for rare