Gold and uranium recovery from electronic waste, soil and wastewater

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In a study, the metal coordination ability of α-CD was employed to complex gold and thus isolate and extract it from different matrices of acid-digests of electronic waste and soil [1]. The crude α-CD used was extracted from cassava and yam starch of the non-edible plant species using E. coli α-cyclodextrin glucanotransferase (α-CGTase), and n-butanol and n-octanol as selective complexants, with yields ≥ 62%. The crude α-CD extract without need for purification was refluxed with gold containing-electronic waste and soil predigested in a mixture of NaBr/HNO3 for 4 – 7 days. Recoveries of up to 22.9% and 70.8% gold were achieved from electronic waste and soil, respectively using 0.1 M α-CD. This approach is cheap, effective, and environmentally benign.

New maleic anhydride-β-cyclodextrin functionalized magnetic iron oxide nanoparticles (IONPs@MAH-β-CD) were prepared through the simple chemical coprecipitation method [2]. Macroscopic batch experiments were carried out to study its absorption behavior for uranium (VI) under different environmental conditions. Using the magnetic separation technique, it was possible to easily separate IONPs@MAH-β-CD from uranium-containing wastewater. The equilibrium for uranium (VI) adsorption was reached in 180 min. The results showed that the kinetics and isotherm of the adsorption process were consistent with the pseudo-second-order kinetic model and Langmuir model, respectively, indicating that it was a chemisorption process. Compared with pure IONPs, the maximum adsorption quantity of maleic anhydride-β-cyclodextrin-coated iron oxide nanoparticles for uranium (VI) was significantly improved, which could reach 163.93 mg g−1. The recyclability of the IONPs@MAH-β-CD was investigated, and FTIR and XPS characterization were used to explore the possible mechanism of U(VI) adsorption.

[1] Karume, I. , Tewolde, S. , Tebandeke, E. , Mukasa, I. and Mbabazi, R. (2022) Efficiency of Crude α-Cyclodextrin in Gold Recovery from Electronic Waste and Soil. Green and Sustainable Chemistry12, 73-82. doi: 10.4236/gsc.2022.123006.

[2] Xing Zhong, Qiaozhulin Yuan, Qiang Wang, Caixia Hu,,Kai Guo, Jinbo Ouyang, and Mingyang Chen (2022) Maleic Anhydride-β-Cyclodextrin Functionalized Magnetic Nanoparticles for the Removal of Uranium (VI) from Wastewater. Crystals 2022, 12(12), 1731;

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