A cryo-SEM study of aggregate and floc structure changes during clay settling and raking processes
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| Title: | A cryo-SEM study of aggregate and floc structure changes during clay settling and raking processes |
|---|---|
| Authors: | Du, Jianhua1,2 Jianhua.Du@postgrads.unisa.edu.au, Pushkarova, Rada A.3, Smart, Roger St.C.1 |
| Source: | International Journal of Mineral Processing. Sep2009, Vol. 93 Issue 1, p66-72. 7p. |
| Subjects: | Structural analysis (Science), Kaolinite, Analysis of clay, Clustering of particles, Flocculation, Suspensions (Chemistry), Mineral processing, Cryochemistry, Settlement of structures, Scanning electron microscopy |
| Abstract: | Abstract: The destabilization of kaolinite suspension by anionic flocculant addition occurs in three zones; free settling, hindered settling and compression which usually includes a final bed raking process in mineral processing practice. This paper reports changes in the kaolinite aggregate and floc structures in the different settling and raking zones by cryo-vitrification/cryo-SEM techniques with image analysis combining micro- and macro-flocs. Cryo-SEM images indicate that, even during free settling, fine clay particles are bridged predominantly in edge–edge (E–E) with some face–face (F–F) configurations forming single, small flocs and some chain structures. When these small flocs and chains settle into the hindered settling zone, the collision between flocs and chains results in “honeycomb” network structures formed with lateral chain-like extension. The settled bed consists of these honeycomb structures with both inter-aggregate and intra-aggregate trapped water and has relatively low bed density (e.g. <12 wt.% for a 2 wt.% slurry). The effect of the raking process in dramatically improving thickener underflow solids has been extensively studied but the structural changes in flocs and aggregates in this process are less well defined. Raking the compression zone for 1 h at 3 rpm can release some of the trapped water in the “honeycomb” structure and the bed density for 2 wt.% slurry improves dramatically to more than 36 wt.%. Cryo-SEM illustrates the extensive restructuring of flocs from predominantly E–E to predominantly F–F in many areas. The STructural IMage ANalysis (STIMAN) software is used to combine a series of images at magnifications from 1000× to 8000×, including both macro- and micro-flocs. This structural analysis comparing the un-raked and raked bed samples gives increases in total particle area of 30% and in relative particle area of 6%. The relatively low energy rake action of the shear stress results in the disruption of the E–E chains and the honeycomb structure, partly releasing the trapped water and inducing some E–E to F–F aggregate restructuring are clearly illustrated in these results. [Copyright &y& Elsevier] |
| Copyright of International Journal of Mineral Processing is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
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| Header | DbId: egs DbLabel: Engineering Source An: 43769769 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: A cryo-SEM study of aggregate and floc structure changes during clay settling and raking processes – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Du%2C+Jianhua%22">Du, Jianhua</searchLink><relatesTo>1,2</relatesTo><i> Jianhua.Du@postgrads.unisa.edu.au</i><br /><searchLink fieldCode="AR" term="%22Pushkarova%2C+Rada+A%2E%22">Pushkarova, Rada A.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Smart%2C+Roger+St%2EC%2E%22">Smart, Roger St.C.</searchLink><relatesTo>1</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22International+Journal+of+Mineral+Processing%22">International Journal of Mineral Processing</searchLink>. Sep2009, Vol. 93 Issue 1, p66-72. 7p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Structural+analysis+%28Science%29%22">Structural analysis (Science)</searchLink><br /><searchLink fieldCode="DE" term="%22Kaolinite%22">Kaolinite</searchLink><br /><searchLink fieldCode="DE" term="%22Analysis+of+clay%22">Analysis of clay</searchLink><br /><searchLink fieldCode="DE" term="%22Clustering+of+particles%22">Clustering of particles</searchLink><br /><searchLink fieldCode="DE" term="%22Flocculation%22">Flocculation</searchLink><br /><searchLink fieldCode="DE" term="%22Suspensions+%28Chemistry%29%22">Suspensions (Chemistry)</searchLink><br /><searchLink fieldCode="DE" term="%22Mineral+processing%22">Mineral processing</searchLink><br /><searchLink fieldCode="DE" term="%22Cryochemistry%22">Cryochemistry</searchLink><br /><searchLink fieldCode="DE" term="%22Settlement+of+structures%22">Settlement of structures</searchLink><br /><searchLink fieldCode="DE" term="%22Scanning+electron+microscopy%22">Scanning electron microscopy</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Abstract: The destabilization of kaolinite suspension by anionic flocculant addition occurs in three zones; free settling, hindered settling and compression which usually includes a final bed raking process in mineral processing practice. This paper reports changes in the kaolinite aggregate and floc structures in the different settling and raking zones by cryo-vitrification/cryo-SEM techniques with image analysis combining micro- and macro-flocs. Cryo-SEM images indicate that, even during free settling, fine clay particles are bridged predominantly in edge–edge (E–E) with some face–face (F–F) configurations forming single, small flocs and some chain structures. When these small flocs and chains settle into the hindered settling zone, the collision between flocs and chains results in “honeycomb” network structures formed with lateral chain-like extension. The settled bed consists of these honeycomb structures with both inter-aggregate and intra-aggregate trapped water and has relatively low bed density (e.g. <12 wt.% for a 2 wt.% slurry). The effect of the raking process in dramatically improving thickener underflow solids has been extensively studied but the structural changes in flocs and aggregates in this process are less well defined. Raking the compression zone for 1 h at 3 rpm can release some of the trapped water in the “honeycomb” structure and the bed density for 2 wt.% slurry improves dramatically to more than 36 wt.%. Cryo-SEM illustrates the extensive restructuring of flocs from predominantly E–E to predominantly F–F in many areas. The STructural IMage ANalysis (STIMAN) software is used to combine a series of images at magnifications from 1000× to 8000×, including both macro- and micro-flocs. This structural analysis comparing the un-raked and raked bed samples gives increases in total particle area of 30% and in relative particle area of 6%. The relatively low energy rake action of the shear stress results in the disruption of the E–E chains and the honeycomb structure, partly releasing the trapped water and inducing some E–E to F–F aggregate restructuring are clearly illustrated in these results. [Copyright &y& Elsevier] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of International Journal of Mineral Processing is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1016/j.minpro.2009.06.004 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 7 StartPage: 66 Subjects: – SubjectFull: Structural analysis (Science) Type: general – SubjectFull: Kaolinite Type: general – SubjectFull: Analysis of clay Type: general – SubjectFull: Clustering of particles Type: general – SubjectFull: Flocculation Type: general – SubjectFull: Suspensions (Chemistry) Type: general – SubjectFull: Mineral processing Type: general – SubjectFull: Cryochemistry Type: general – SubjectFull: Settlement of structures Type: general – SubjectFull: Scanning electron microscopy Type: general Titles: – TitleFull: A cryo-SEM study of aggregate and floc structure changes during clay settling and raking processes Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Du, Jianhua – PersonEntity: Name: NameFull: Pushkarova, Rada A. – PersonEntity: Name: NameFull: Smart, Roger St.C. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 09 Text: Sep2009 Type: published Y: 2009 Identifiers: – Type: issn-print Value: 03017516 Numbering: – Type: volume Value: 93 – Type: issue Value: 1 Titles: – TitleFull: International Journal of Mineral Processing Type: main |
| ResultId | 1 |
