ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Palm kernel fatty acid distillate as a benign organic solvent for Cu(II) extraction: stoichiometry, thermodynamic and structural studies

Siti Fatimah Abdul Halim, Norhashimah Morad, and Siu Hua Chang

Waste Management and Resource Recovery (WeResCue) Group, Chemical Engineering Studies, College of Engineering, Universiti Teknologi MARA, Permatang Pauh, Malaysia

E-mail: shchang@uitm.edu.my

Received: 17 April 2023  Accepted: 28 July 2023

Abstract:

Although palm kernel fatty acid distillate (PKFAD), a novel benign extractant rich in free fatty acids (FFAs), demonstrates efficient extraction of Cu(II) from aqueous solutions, the understanding of the stoichiometry, thermodynamics, and structure of the extracted species (Cu(II)-FFA complexes) remains unclear. Hence, this work aimed to investigate the stoichiometry, thermodynamics, and structure of Cu(II)-FFA complexes in PKFAD to gain fundamental insights into the extraction behavior of this new extractant. The stoichiometry study employed the equilibrium slope and numerical analyses, while the thermodynamic investigation was explored at different temperatures. The extraction thermodynamics of Cu(II) by PKFAD were utilized to determine the structure of the extracted species. Both the equilibrium slope and numerical analyses revealed a stoichiometry of 1:6 for Cu(II)-FFA complexes in PKFAD, while the thermodynamic study indicated that the extraction process was exothermic, nonspontaneous, and primarily driven by enthalpy over the temperature range studied. A plausible structure of Cu(II)-FFA complexes in PKFAD was also postulated based on the thermodynamic data obtained.

Graphical Abstract

Keywords: Stoichiometry; Thermodynamics; Structure; Cu(II); Free fatty acids; Palm kernel fatty acid distillate

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-023-03014-9

Chemical Papers 77 (11) 7237–7248 (2023)