Performance of poly-γ-glutamic acid–calcium hydroxide treatment for phosphate removal and applicability of the resulting flocculant as a phosphate-based fertilizer

Abstract

Herein, we focused on poly-γ-glutamic acid (PG) as a bioresource material for phosphate removal and assessed the efficiency of a combined PG and calcium hydroxide (CH) treatment via elemental distribution and X-ray diffraction analysis. Additionally, this study briefly assessed the applicability of the flocculants obtained from the phosphate removal process as phosphate-based fertilizers. The results showed that phosphate removal capacity was higher when treated with the PG–CH mixture than that with pure PG or CH. Additionally, the phosphate removal treatment with the PG–CH mixture had the advantage of straightforward separation of the supernatant from the flocculant. Moreover, the mechanism of phosphate removal by the PG + CH treatment was evaluated on the basis of elemental distribution and X-ray diffraction analysis. Finally, the flocculants obtained from the PG + CH treatment had 20.5% citric acid-soluble content, indicating their potential as phosphate-based fertilizers.