Utilization of phosphogypsum waste through a temperature swing recyclable acid process and its application for transesterification

Houli Li, Jin Hu, Yixiao Wang, Xuebin An, Mingzhu Tang, Zhiying Wang, Yunshan Wang, Gang Yang, Weijun Bao, Yong Sun

Research output: Journal PublicationArticlepeer-review

9 Citations (Scopus)


In this paper, a biodiesel catalyst was prepared from the phosphogypsum (PG) by a hybrid approach through temperature swing acid leaching/crystallization steps followed by the subsequent fluidized bed calcination. The impacts of acid leaching and crystallization were extensively analyzed via a supervised machine learning approach using a limited number of experimental runs to find out the optimal condition. The determined optimal conditions are X1-95 (ºC), X2-30 (min), X3-30 (wt%-H2SO4), and corresponding validation experimental result (at the optimal condition setting) shows± 5% uncertainties. The prepared catalyst predominately contains CaSO4 (98 wt%) with the impurities less than 0.3 wt% (i.e., P2O5- and F-). The numbers of acid leaching cycles (up to 10 cycles) were investigated, and result indicates a good contaminates recovery (P2O5:1.8 g/100 g PG, Mg2+: 0.3 g/100 g PG, Al3+: 0.3 g/100 g PG, Fe3+: 0.1 g/100 g PG) in the leachate through the downstream solvent extraction. The catalytic conversion reaches about 50% with approximately± 5% deactivation when catalyst was reused at the same transesterification condition. The decreased binding energies of S2p (169.6 eV) and O1st (533 eV) in used catalyst indicate the deactivation of surface catalytic sites. The key properties of the prepared biodiesel are comparable to the American society for testing and materials (ASTM) standards.

Original languageEnglish
Pages (from-to)295-303
Number of pages9
JournalProcess Safety and Environmental Protection
Publication statusPublished - Dec 2021


  • Biodiesel
  • Catalyst
  • Machine learning optimization
  • Phosphogypsum

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • General Chemical Engineering
  • Safety, Risk, Reliability and Quality


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