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New approaches to the study of hydrophobicity and wetting of soils: methods and theories / Helen Balshaw

Swansea University Author: Helen Balshaw

DOI (Published version): 10.23889/Suthesis.52976

Abstract

New approaches to the study of hydrophobicity and wetting of soils were investigated with the following research objectives: 1) to evaluate the use of fluorescence probes, nile red and pyrene, as tools to assess the polarity and viscosity of organics adsorbed to soils; 2) to assess, using a variety...

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Published: Swansea 2019
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
Supervisor: Douglas, P. ; Doerr, S.H.
URI: https://cronfa.swan.ac.uk/Record/cronfa52976
first_indexed 2019-12-05T19:15:49Z
last_indexed 2021-02-09T04:14:54Z
id cronfa52976
recordtype RisThesis
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spelling 2021-02-08T13:03:16.7132575 v2 52976 2019-12-05 New approaches to the study of hydrophobicity and wetting of soils: methods and theories 6c3a767a810bbcf18dccb4b97445b164 Helen Balshaw Helen Balshaw true false 2019-12-05 New approaches to the study of hydrophobicity and wetting of soils were investigated with the following research objectives: 1) to evaluate the use of fluorescence probes, nile red and pyrene, as tools to assess the polarity and viscosity of organics adsorbed to soils; 2) to assess, using a variety of kinetic methods, what steps are involved in wetting soils; and 3) to assess the validity of current theories for the anomalously high contact angles often measured for water on soils, and investigate an alternative explanation based on the geometry of a water drop sitting on hydrophobic particles. Whilst it was possible to image nile red emission after adsorption to soils, issues of emission intensity and soil auto-luminescence suggest that nile red is not a useful probe for soil studies. Fluorescence measurements were made using pyrene as an in-situ polarity and viscosity/mobility probe. Using pyrene co-deposited with organics on acid-washed sand, excimer kinetics showed a decrease in environment mobility as the organic layer was changed from a liquid to a hard wax. Spectra from natural soils indicated varying environmental polarity and heterogeneity within the soil samples studied. A theoretical model for soil wetting, involving adhesional-immersional wetting followed by branching capillary wetting, is proposed, and a series of experiments to assess the validity of this model described. Methods used include: water drop penetration time (WDPT) test, mass of soil grains wetted over time; time taken for penetration of a water drop into different soil thicknesses; optical microscopy; WDPT measurements with salt solutions of different densities. An alternative interpretation of the anomalously high contact angles measured on soils is proposed based on a correction factor for water on particles. To assess this, measurements were made using regularly arranged ballpoint needles and metal spheres, and acid-washed sand and natural soil, coated in paraffin wax. E-Thesis Swansea Soil, water repellency, fluorescence, probes, wetting, contact angle, kinetics 5 12 2019 2019-12-05 10.23889/Suthesis.52976 A selection of third party content is redacted or is partially redacted from this thesis.ORCiD identifier https://orcid.org/ 0000-0002-0087-2170 COLLEGE NANME COLLEGE CODE Swansea University Douglas, P. ; Doerr, S.H. Doctoral Ph.D EPSRC, NCZ855 2021-02-08T13:03:16.7132575 2019-12-05T16:32:23.7645581 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Geography Helen Balshaw 1 52976__16049__d62296f06de340d0afb93eb02b51d535.pdf Balshaw_Helen_Redacted.pdf 2019-12-05T16:51:58.5349845 Output 10684522 application/pdf E-Thesis – open access true true
title New approaches to the study of hydrophobicity and wetting of soils: methods and theories
spellingShingle New approaches to the study of hydrophobicity and wetting of soils: methods and theories
Helen Balshaw
title_short New approaches to the study of hydrophobicity and wetting of soils: methods and theories
title_full New approaches to the study of hydrophobicity and wetting of soils: methods and theories
title_fullStr New approaches to the study of hydrophobicity and wetting of soils: methods and theories
title_full_unstemmed New approaches to the study of hydrophobicity and wetting of soils: methods and theories
title_sort New approaches to the study of hydrophobicity and wetting of soils: methods and theories
author_id_str_mv 6c3a767a810bbcf18dccb4b97445b164
author_id_fullname_str_mv 6c3a767a810bbcf18dccb4b97445b164_***_Helen Balshaw
author Helen Balshaw
author2 Helen Balshaw
format E-Thesis
publishDate 2019
institution Swansea University
doi_str_mv 10.23889/Suthesis.52976
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Geography{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Geography
document_store_str 1
active_str 0
description New approaches to the study of hydrophobicity and wetting of soils were investigated with the following research objectives: 1) to evaluate the use of fluorescence probes, nile red and pyrene, as tools to assess the polarity and viscosity of organics adsorbed to soils; 2) to assess, using a variety of kinetic methods, what steps are involved in wetting soils; and 3) to assess the validity of current theories for the anomalously high contact angles often measured for water on soils, and investigate an alternative explanation based on the geometry of a water drop sitting on hydrophobic particles. Whilst it was possible to image nile red emission after adsorption to soils, issues of emission intensity and soil auto-luminescence suggest that nile red is not a useful probe for soil studies. Fluorescence measurements were made using pyrene as an in-situ polarity and viscosity/mobility probe. Using pyrene co-deposited with organics on acid-washed sand, excimer kinetics showed a decrease in environment mobility as the organic layer was changed from a liquid to a hard wax. Spectra from natural soils indicated varying environmental polarity and heterogeneity within the soil samples studied. A theoretical model for soil wetting, involving adhesional-immersional wetting followed by branching capillary wetting, is proposed, and a series of experiments to assess the validity of this model described. Methods used include: water drop penetration time (WDPT) test, mass of soil grains wetted over time; time taken for penetration of a water drop into different soil thicknesses; optical microscopy; WDPT measurements with salt solutions of different densities. An alternative interpretation of the anomalously high contact angles measured on soils is proposed based on a correction factor for water on particles. To assess this, measurements were made using regularly arranged ballpoint needles and metal spheres, and acid-washed sand and natural soil, coated in paraffin wax.
published_date 2019-12-05T07:38:03Z
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score 11.056895

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