A novel process approach of a circular economy practice in the production of hydroxyapatite from phosphogypsum


Avşar C., ERTUNÇ S.

PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS, vol.199, no.7-9, pp.628-634, 2024 (SCI-Expanded, Scopus)

  • Publication Type: Article / Article
  • Volume: 199 Issue: 7-9
  • Publication Date: 2024
  • Doi Number: 10.1080/10426507.2024.2410867
  • Journal Name: PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Chemical Abstracts Core
  • Page Numbers: pp.628-634
  • Keywords: Calcium phosphate, hydrothermal synthesis, hydroxyapatite, phosphogypsum
  • Ankara University Affiliated: Yes

Abstract

Phosphogypsum (PG), a by-product of phosphate fertilizer industry, is chemically impure gypsum (CaSO4 2 H2O) containing phosphate residues. Provided by the calcium and phosphorus content, PG can be considered as a precursor for synthetic hydroxyapatite (s-HAp) production. This study proposes a two-step alkali route for s-HAp production from PG. Resulting samples were characterized by ICP-OES, SEM, XRD and FT-IR analyses in comparison with bone ash (BA) sample. Ca/P ratio (wt%) was determined as 2.46 and 2.78 for s-HAp and BA samples, respectively. SEM analysis showed the uniform distribution of spherical shaped particles in BA samples; however s-HAp particles showed irregular distribution of nearly spherical-like particles agglomerated as platelets on the surface. XRD analysis indicated that s-HAp particles possessed low crystallinity and ICDD references showed the appearance of apatite-CaOH phases. FT-IR spectrum showed the vibration bands of PO43- bands in the range of 1018-601 cm(-1). According to characterization analyses, s-HAp samples show lower Ca/P ratio, irregular morphology, and low crystallinity due to possible impurities. Thus, further downstream operations regarding to impurity removal should be employed to develop a promising route to synthetic HAp production and employ a CE approach on industrial scale to evaluate s-HAp samples as a commercial substitute to BA.