An official website of the United States government
Atmospheric pressure nonthermal plasma treatment can be a novel, green and low energy method to convert biomass to biobased chemicals. The unique physiochemistry of plasma discharge enables reactions within biomass that otherwise could not possibly occur under traditional conditions. In this study, we present a simple method of producing a high yield of levoglucosan from cellulose without using any catalysts, chemicals, solvents or vacuum, but by using plasma treatment to control the depolymerization mechanism of cellulose. Cellulose was first pretreated in a dielectric barrier discharge reactor operating in ambient air or argon for 10–60 s, followed by pyrolysis at 350–450 °C to produce up to 78.6% of levoglucosan. Without the plasma pretreatment, the maximum yield of levoglucosan from cellulose pyrolysis was 58.2%. The results of this study showed that the plasma pretreatment led to homolytic cleavage of glycosidic bonds. The resulting free radicals were then trapped within the cellulose structure when the plasma discharge stopped, allowing subsequent pyrolysis of the plasma-pretreated cellulose to proceed through a radical-based mechanism. The present results also revealed that although the radical-based mechanism is highly selective to levoglucosan formation, this pathway is usually discouraged when the untreated cellulose is pyrolyzed due to the high energy barrier for homolytic cleavage. Initiating homolytic cleavage during the plasma pretreatment also helped the pretreated cellulose to produce higher yields of levoglucosan using lower pyrolysis temperatures. At 375 °C, the levoglucosan yield was only 53.2% for the untreated cellulose, whereas the yield reached 77.6% for the argon-plasma pretreated cellulose.
more »
« less
The Influence of Thermal and Thermochemical Pre-treatment of Mine Tailings on their Solubility and Phase Composition for Geopolymerization Application
The largest hurdle for the reuse of mine tailings as a source material for geopolymerization and the production of construction materials is the tailings’ low reactivity. The highly crystalline tailings require a strongly basic alkali activator, which is user hazardous and unfavorable for industrial use. In order to increase the reactivity of the mine tailings, pre-treatment methods can be used to reduce the crystallinity and increase the solubility of aluminosili-cates. Thermal pretreatment was able to increase the solubility of silicon and aluminum, but this did not seem to be directly related to the increase in amorphous content. Thermochemical pre-treatment was even more effective than purely thermal pretreatment for increasing the quantity of amorphous phase and producing soluble aluminosilicates that can be available for geopolymerization reactions. The aluminum solubility of pretreated tailings is closely related to the quantity of muscovite present after the treatment. Further research is needed to assess the effectiveness of pretreatment for geopolymerization of mine tailings and to link the amorphous content to the solubility of aluminosilicates. Mechanical and durability evaluation of geopolymers made from pretreated mine tailings is ongoing.
more »
« less
- Award ID(s):
- 1950486
- PAR ID:
- 10479769
- Publisher / Repository:
- Tailings and Mine Waste
- Date Published:
- Journal Name:
- Tailings and Mine Waste
- Format(s):
- Medium: X
- Location:
- Denver
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Few investigations have focused on the potential uses of artisanal gold (Au) mine tailings, despite the fact that artisanal gold mining activity contributes to environmental issues such as greenhouse gas. Mineralogical characterizations of artisanal gold mine tailings in Miyove gold mine (Baradega and Masogwe) in Rwanda were investigated for potential utilization as a source of valuable gold, using the centrifugal separation technique. Results of X-ray diffraction analysis, energy dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, inductively coupled plasma–optical emission spectroscopy, and X-ray fluorescence showed that artisanal gold mine tailings samples have significant amounts of gold to justify economical gold extraction opportunity. The gold grades in the ores and artisanal gold mine tailings were in the ranges of 37–152 and 2–7 g t−1, respectively. Quartz was a major phase, with minor impurities in two different types of gold ores and their respective tailings. The beneficiation carried out using centrifugal separation, regarded as an extension of gravity separation, showed gold grades in the range of 535–1515 g t−1 for gold ores and 36–302 g t−1 for artisanal gold mine tailings. The gold recoveries for ores and artisanal gold mine tailings were in the range of 21.8–47.3% and 46.9–63.8%, respectively. The results showed that the centrifugal separation technique was more efficient in boosting gold recovery compared to the present panning approach employed at the site, which sometimes recover as low as 10%. The results suggest that mineralogical characterization of artisanal gold mine tailings allows for the development and design of a suitable methods for improving gold ore beneficiation and artisanal gold mine tailings reprocessing.more » « less
-
Abstract PremiseThe preservation of plant tissues in ethanol is conventionally viewed as problematic. Here, we show that leaf preservation in ethanol combined with proteinase digestion can provide high‐quality DNA extracts. Additionally, as a pretreatment, ethanol can facilitate DNA extraction for recalcitrant samples. MethodsDNA was isolated from leaves preserved with 96% ethanol or from silica‐desiccated leaf samples and herbarium fragments that were pretreated with ethanol. DNA was extracted from herbarium tissues using a special ethanol pretreatment protocol, and these extracts were compared with those obtained using the standard cetyltrimethylammonium bromide (CTAB) method. ResultsDNA extracted from tissue preserved in, or pretreated with, ethanol was less fragmented than DNA from tissues without pretreatment. Adding proteinase digestion to the lysis step increased the amount of DNA obtained from the ethanol‐pretreated tissues. The combination of the ethanol pretreatment with liquid nitrogen freezing and a sorbitol wash prior to cell lysis greatly improved the quality and yield of DNA from the herbarium tissue samples. DiscussionThis study critically reevaluates the consequences of ethanol for plant tissue preservation and expands the utility of pretreatment methods for molecular and phylogenomic studies.more » « less
-
Abstract Integrating multidisciplinary research in plant genetic engineering and renewable deep eutectic solvents (DESs) can facilitate a sustainable and economic biorefinery. Herein, we leveraged a plant genetic engineering approach to specifically incorporate C6C1monomers into the lignin structure. By expressing the bacterialubiCgene in sorghum,p‐hydroxybenzoic acid (PB)‐rich lignin was incorporated into the plant cell wall while this monomer was completely absent in the lignin of the wild‐type (WT) biomass. A DES was synthesized with choline chloride (ChCl) and PB and applied to the pretreatment of the PB‐rich mutant biomass for a sustainable biorefinery. The release of fermentable sugars was significantly enhanced (∼190 % increase) compared to untreated biomass by the DES pretreatment. In particular, the glucose released from the pretreated mutant biomass was up to 12 % higher than that from the pretreated WT biomass. Lignin was effectively removed from the biomass with the preservation of more than half of the β‐Ο‐4 linkages without condensed aromatic structures. Hydrogenolysis of the fractionated lignin was conducted to demonstrate the potential of phenolic compound production. In addition, a simple hydrothermal treatment could selectively extract PB from the same engineered lignin, showing a possible circular biorefinery. These results suggest that the combination of PB‐based DES and engineered PB‐rich biomass is a promising strategy to achieve a sustainable closed‐loop biorefinery.more » « less
-
Understanding the cyclic response of mine tailings is key for areas with moderate to high seismicity and an active mining industry (e.g. the United States, Peru, and Chile). However, assessing the cyclic response of mine tailings still relies on procedures and correlations developed for natural soils (i.e. sands and clays). This is due to information on the cyclic response of mine tailings being rather scarce compared to natural soils. Hence, it remains unclear if more efficient approaches can be implemented. This study presents an experimental database focused on the cyclic response of mine tailings compiled from various sources. The database is organized considering three classes, where all three contain cyclic simple shear (CSS) information. Class A also includes triaxial (Tx) and cone penetration testing (CPTu) information, Class B has Tx or CPTu information, and Class C contains no additional information beyond CSS. Most materials belong to Class A. It is worth noting that Class C (only cyclic information) is comparable with most databases for natural soils, hence highlighting the uniqueness of our database. In total, the database contains 129 CSS tests on 20 materials that represent a broad range of mine tailings. Thirteen materials belong to Class A, 5 to Class B, and 2 to Class C. In discussing the database, key information (e.g. the range of liquefaction resistance curves) is shared. In addition, potential assessments that can be conducted with the database are illustrated. The study closes by presenting the database organization and discussing potential uses. The database is available under the following DOI: https://doi.org/10.17603/ds2-1k0a-dt17more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Proceeding:
- The DOI is not currently available.
