An O/N/S-rich porous Fe-based metal-organic framework (MOF) for gold recovery from the aqueous phase with excellent performance

• Published in: The Science of the total environment Vol. 927; p. 172160
• Main Authors: Yu, Xuefeng, Yan, Chuanhao, Zhang, Jinlong, He, Jinglei, Zhang, Meng, Guo, Xiaoying, Wu, Zhipeng, Liu, Junfeng, Wang, Xilong
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2024
• Subjects: Au(III) recovery; MOF; Reduction; Sorption selectivity; Au(III) recovery; Reduction; Sorption selectivity; MOF
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.172160

Recovering gold from wastewater has both economic and environmental benefits. However, how to effectively recover it is challenging. In this work, a novel Fe-based metal-organic framework (MOF) was synthesized and decorated with 2,5-thiophenedicarboxylic acid to have a well-developed porous architecture to effectively recover Au(III) from water. The maximum Au(III) sorption capacity by the finally-synthesized porous material MIL-101(Fe)-TDCA reached 2350 mg/g at pH = 6.00 ± 0.15, which is one of the highest among all literature-reported relevant materials including MOFs, and high sorption strength can be maintained within a wide pH range from 2.0 to 10.0. Besides, Au(III) sorption efficiency at low concentrations (i.e., 3.5 × 104 mg/mL) reached over 99%. Mechanically, outstanding Au(III) sorption by MIL-101(Fe)-TDCA resulted from the O/N/S-containing moieties on its surface, large surface area and porosity. The N- and S-containing functionalities (CS, CONH) served as electron donors to chelate Au(III). The O-containing (FeOFe, COFe, COOH, and coordinated H2O) and N-containing (CONH) moieties on MIL-101(Fe)-TDCA interacted with OH groups on the hydrolyzed species of Au(III) (AuCl3(OH)−, AuCl2(OH)2−, and AuCl(OH)3−) by hydrogen bond, which further increased Au(III) sorption. Furthermore, about 45.71% of Au(III) was reduced to gold nanoparticles by CS groups on the decorated 2,5-dithiophene dicarboxylic acid during sorption on MIL-101(Fe)-TDCA. Over 98.35% of Au(III) was selectively sorbed on MIL-101(Fe)-TDCA at pH 4.0, much higher than that of the coexisting heavy metal ions including Cu(II), Zn(II), Pb(II), and Ni(II) (< 5%), despite their same concentration at 0.01 mg/mL. Although sorption selectivity of a noble metal Pt(IV) by MIL-101(Fe)-TDCA is relatively poor (68.23%), it could be acceptable. Moreover, reusability of MIL-101(Fe)-TDCA is also excellent, since above 90.5% Au(III) still can be sorbed after two sorption-desorption cycles. Overall, excellent sorption performance and the roughly-calculated gold recycling benefits (26.30%) highlight that MIL-101(Fe)-TDCA is a promising porous material for gold recovery from the aqueous phase. [Display omitted] •A porous Fe-based MOF architecture was synthesized for efficient Au(III) recovery.•The maximum sorbed amount of Au(III) by MIL-101(Fe)-TDCA reached 2350 mg/g.•High Au(III) sorption performance by MIL-101(Fe)-TDCA was achieved within pH 2 – 10.•Outstanding Au(III) sorption selectivity by MIL-101(Fe)-TDCA at pH 4 is evident.•45.71% of Au(III) was reduced to elemental gold during sorption to MIL-101(Fe)-TDCA.