Carbon dioxide for fine coal flotation: Final report, September 1985--December 1987. [With CO/sub 2/ pretreatment in a pressure filter]
A detailed research effort on the fundamentals of coal flotation by carbon dioxide was initiated. Research has been carried out on different aspects of the problem including hydrophobic characterization, bench-scale flotation, carbon dioxide adsorption, electrokinetic behavior, and FTIR spectroscopy for coals of different rank. Coal hydrophobicity as defined by contact angle and bubble attachment time measurements also can be characterized by diffuse reflectance FTIR spectroscopic criterion---the hydrophilicity index---which contrasts the relative abundance of surface hydrophilic groups with the relative abundance of surface hydrophobic groups. This index can be used to predict or estimate the flotation behavior of coals of different rank. Rank-dependence of coal hydrophobicity established by macroscopic characterization and FTIR spectroscopy can be verified by XPS for dry coals and in-situ ATR-FTIR spectroscopy for wet coals. Contact-angle and bubble attachment-time measurements as well as FTIR spectroscopy reveal the enhanced hydrophobicity of CO/sub 2/-treated coal and explain the improved flotation response with carbon dioxide flotation. BET measurements, differential scanning calorimetry, and FTIR spectroscopy confirmed that CO/sub 2/ is specifically adsorbed at the coal surface. In-situ FTIR studies suggest that carbon dioxide adsorbed on both the internal and external surface of coal is polarized. Partial solvation of the first layer of adsorbed CO/sub 2/ results in a CO/sub 2/-covered coal surface, which appears to convert some of the hydrophilic sites into hydrophobic sites. The high specific affinity of coal for CO/sub 2/ results in the displacement of pore water and leads to nanobubble formation at the coal surface during flotation. Specific adsorption and the nanobubble formation contribute to the enhanced flotation response. 67 refs., 33 figs., 16 tabs.
- Research Organization:
- Utah Univ., Salt Lake City (USA). Dept. of Metallurgy and Metallurgical Engineering
- DOE Contract Number:
- FG22-85PC80530
- OSTI ID:
- 6983844
- Report Number(s):
- DOE/PC/80530-T7; ON: DE88005659
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON DIOXIDE
ADSORPTION
COAL
CHEMICAL PROPERTIES
FLOTATION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
AFFINITY
AGING
ASH CONTENT
BENCH-SCALE EXPERIMENTS
BUBBLES
CALORIMETRY
CHEMICAL COMPOSITION
COAL PREPARATION
COAL RANK
MEASURING METHODS
PHOTOELECTRON SPECTROSCOPY
PROGRESS REPORT
SOLVATION
SPECIFICITY
SPECTROSCOPY
SURFACES
CARBON COMPOUNDS
CARBON OXIDES
CARBONACEOUS MATERIALS
CHALCOGENIDES
DOCUMENT TYPES
ELECTRON SPECTROSCOPY
ENERGY SOURCES
FOSSIL FUELS
FUELS
MATERIALS
OXIDES
OXYGEN COMPOUNDS
SEPARATION PROCESSES
SORPTION
010300* - Coal
Lignite
& Peat- Preparation- (1987-)
400201 - Chemical & Physicochemical Properties
010600 - Coal
Lignite
& Peat- Properties & Composition