Recovery of heavy metals and phosphate with urine or sewage

Abstract

The aim of this study was to recover phosphoric acid and rare earths simultaneously. Dysprosium (Dy), yttrium (Y), and europium (Eu) were selected as rare earth elements. Since urine was expected to have pH buffering capacity, we also examined whether phosphoric acid and heavy metals could be recovered from acidic aqueous metal solutions by this method. Rare earths and phosphoric acid were precipitated and recovered not only from urine but also from sewage. In terms of the molar ratio, the efficiency was higher in sewage than in urine. The precipitation occurred even when the Dy solution was acidic, and the pH of the supernatant solution was close to that of urine, indicating that pH adjustment before and after precipitation was not necessary. These results indicate that this method, which utilizes the pH buffering effect of urine, can recover the heavy metals and phosphoric acid.