Liquid-liquid extraction with fluorinated and non-fluorinated diethyl malonate

• Main Author: Koh, Norman Zhi Cong
• Other Authors: Alex Yan Qingyu
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/156801
• Institution: Nanyang Technological University

Electronic waste (E-waste) has snowballed throughout the years and has become the fastest-growing waste segment in the world. The number of laptops, phones, and other appliances, typically known as Waste Electrical and Electronic Equipment (WEEE), has doubled from 2009 to 2014 and reached 41.8 million tons in the united states. The current waste management strategy to recycle e-waste is through hydrometallurgy, which works by Liquid-Liquid extraction (LLE). Furthermore, with the advancement of technologies, more rare and precious metals (RPMs) are being used in modern-day electronics, causing them to be labeled as “urban mines,” giving rise to the demand for recycling. The main objective of this study is to serve as a preliminary examination, comparing the extraction efficiency of potential extractants that can be used in supercritical extraction (SCE), a green extraction technique, with their fluorinated counterpart. The extraction efficiency was determined using LLE as LLE has similar mechanism to SCE, where solvent-solute partition had to meet to enable the extraction process. Therefore, using LLE as a preliminary study can give critical insight before using the extractants for SCE. According to past literature, fluorinated malonamides, a type of β-diketone, are able to dissolve substantially in supercritical carbon dioxide (scCO2), which greatly improves the recovery of metals. The extractants used in this study are all malonamides and its derivative, which are , Diethyl 2-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl) malonate (DEMH2F8), 2-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluorodecyl)-malonic acid (MAH2F8) N1,N1,N3,N3-tetramethylmalonamide (TMMA), N,N´-dimethyl-N,N´-dioctyl-2,(2´-hexyloxyethyl) malonamide (DMDOHEMA), Diethyl 2-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl) malonate (TMMAH2F8) , and Diethyl malonate (DEM). Ultraviolet-visible spectroscopy (UV-Vis), X-ray fluorescence (XRF) was used as a semi-quantitative study of the extraction efficiency to serve as a comparison with Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis. The experiment results show that most of the fluorinated extractants did not have an improvement in extraction except fluorinated TMMA, TMMAH2F8. TMMAH2F8 had a good extraction selectivity and extraction efficiency for Pd. A kinetic study was done to compare TMMAH2F8 with a commercially used extractant, DMDOHEMA; however, emulsification and the formation of a gel-like compound during the preparation and extraction caused the analysis to be unsuccessful.