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1. Enhanced extraction of copper from electronic waste via induced morphological changes using supercritical CO2

   https://doi.org/10.1016/j.resconrec.2020.105296  

   Hsu, Emily ; Durning, Christopher J. ; West, Alan C. ; Park, Ah-Hyung Alissa ( May 2021 , Resources, Conservation and Recycling)

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2. Supercritical CO 2 -induced alteration of polymer-metal matrix and selective extraction of valuable metals from waste printed circuit boards

   https://doi.org/10.1039/D0GC02521F  

   Peng, Peng ; Park, Ah-Hyung Alissa ( January 2020 , Green Chemistry)

   The rapidly accumulating amounts of waste electrical and electronic equipment (WEEE) is one of the biggest environmental concerns in modern societies, and this problem will be further accelerated in the future. The use of supercritical CO2 (scCO2) mixed with acids has been proposed as a greener solvent system compared to conventional cyanide and aqua regia solvents, however, the mechanisms of scCO2 in metal extraction from WEEE are still poorly understood. Thus, this study focused on the physical, structural, and chemical interactions between scCO2/acid solvents and complex layered components in waste printed circuit boards (WPCBs), one of the common WEEEs. Our study showed that the use of scCO2-based pretreatment allows faster leaching of metals including copper (Cu) in the subsequent hydrometallurgical process using H2SO4 and H2O2, while allowing gold (Au) recovery as hydrometallurgically delaminated solids. This enhancement is due to the selective leaching of Ni and unique inner porous structures created by ScCO2/acid treatment via dissolving the Ca-silicate-bearing fiberglass within the WPCB. Thus, the scCO2-based pretreatment of WPCBs shows a multifaceted green chemistry potential relating to the reduction in solvent usage and targeted recovery of Au prior to shredding or grinding that would reduce any loss or dilution of Au in the subsequent waste stream. 

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3. Characterization of 14-Crown-4 Ethers for the Extraction of Lithium from Natural Brines: Synthesis, Solubility Measurements in Supercritical Carbon Dioxide, and Thermodynamic Modeling

   https://doi.org/10.1021/acs.iecr.1c00346  

   Pálsdóttir, Arna ; Alabi, Christopher A. ; Tester, Jefferson W. ( June 2021 , Industrial & Engineering Chemistry Research)
4. Effects of ethanol modified supercritical carbon dioxide extraction and particle size on the physical, chemical, and functional properties of yellow pea flour

   https://doi.org/10.1002/cche.10334  

   Vatansever, Serap ; Rao, Jiajia ; Hall, Clifford ( September 2020 , Cereal Chemistry)

   Supercritical carbon dioxide + ethanol (SC‐CO₂ + EtOH) extraction was previously found to improve organoleptic attributes of yellow pea (Pisum sativumL.) flour. However, the impact of this extraction, in combination with different flour particle sizes, on physical, chemical, and functional properties of yellow pea flour was not established and is thus the focus of this study.

   The interaction effect between SC‐CO₂ + EtOH extraction and yellow pea flour particle size lead to differences in physical, chemical, and functional properties. Extraction caused reductions in most chemical constituents and a lowering of functionality test values such as pasting viscosities. Variable impacts of particle size on flour composition and functionality were observed.

   The impacts of particle size on functionality were anticipated. The degree of differences in functionality between extracted and nonextracted yellow pea flour was not anticipated. Scanning electron micrographs supported protein‐rich particle adherence to the surface of starch granules of extracted pea flour. This observed modification may be responsible for differences in functionality between extracted and nonextracted flours.

   The SC‐CO₂ + EtOH extraction method combined with particle size can be an effective method to modify the functionality of yellow pea flour and ultimately diversifying its application in food systems.

    

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5. In‐situ extraction and impregnation of black walnut husk into polyethylene film using supercritical carbon dioxide with an ethanol modifier

   https://doi.org/10.1002/fsn3.1348  

   Wenzel, Jonathan E. ; Moorman, Veronica ; Wang, Lihua ; Spencer‐Williams, Isaiah ; Hall, Mitchell ; Samaniego, Cheryl S. ; Ammerman, Michelle L. ( December 2019 , Food Science & Nutrition)

   Walnuts are commonly cultivated for their kernel, which is a rich source of antioxidant phenolic compounds. The husk likewise contains antioxidant and antimicrobial compounds, but is typically discarded without further processing. Antioxidant compounds are useful in creating active packaging films, but typically decompose at melt extrusion temperatures in polymer processing. Due to carbon dioxide's low critical point and ability to swell polymer films, supercritical carbon dioxide may be used to impregnate phenolic compounds into polymers. For this study, a novel technique is used to simultaneously produce walnut husk extracts and impregnate the extract into polymer films in the same batch extractor using supercritical carbon dioxide with a 15 wt‐% ethanol modifier at 60°C at 19.4 MPa. The effect of varying the loading of walnut husk in the extractor upon impregnation mass was evaluated with the impregnation mass of the film increasing with walnut husk loading. It was determined by FTIR, as well as the reduction of the protein cytochromec, that antioxidant compounds may be extracted from walnut husks and impregnated into low‐density polyethylene film (LDPE) by this technique.

    

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