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

Abstract

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.

RAS ID

42760

Document Type

Journal Article

Date of Publication

12-1-2021

Volume

156

Funding Information

Key Laboratory of Carbonaceous Wastes Processing and Process Intensification of Zhejiang Province

National Key Research and Development Program of China

Qianjiang Talent Scheme

Ningbo Science and Technology Innovation 2025 Key Project

Ningbo Municipal Commonweal Key Program

School

School of Engineering

Copyright

subscription content

Publisher

Elsevier

Comments

Li, H., Hu, J., Wang, Y., An, X., Tang, M., Wang, Z., . . . Sun, Y. (2021). Utilization of phosphogypsum waste through a temperature swing recyclable acid process and its application for transesterification. Process Safety and Environmental Protection, 156, article 295-303.

https://doi.org/10.1016/j.psep.2021.10.023

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Link to publisher version (DOI)

10.1016/j.psep.2021.10.023