TY - JOUR

T1 - Physical properties controlling water repellency in synthesized granular solids

AU - Saulick, Y.

AU - Lourenço, S. D. N.

AU - Baudet, B. A.

AU - Woche, S. K.

AU - Bachmann, J.

N1 - Funding information: The first author thanks The University of Hong Kong (HKU) for the Postgraduate Scholarship. Financial support provided by the General Research Fund, Research Grants Council, Hong Kong (17221016 and 17203417) and HKU seed funds for basic research (201406159004 and 201511159205) are acknowledged.

PY - 2018/7/2

Y1 - 2018/7/2

N2 - The wettability of granular solids such as soil is known to depend primarily on two factors: their inherent chemistry and their physical properties, such as their particle size, particle shape and surface roughness. Nevertheless, the distinctive physical properties of such materials have not been fully explored to gauge their wettability. In this study, the difference in wettability between a flat solid (microscope slide) and three granular solids, namely glass beads (GB), Leighton Buzzard Sand (LBS) and crushed Glass (CG), which have different physical properties, were examined. The effect of chemistry was isolated by strongly hydrophobizing the above materials by treatment with dimethyldichlorosilane. Wettability measurements were made by measuring the water–solid contact angle (CA) by the sessile drop method after adhering one layer of uniformly oriented granular solids on to double-sided adhesive tape initially attached to a microscope slide. Techniques for particle characterization included sieving for particle size, dynamic image analysis for particle shape and confocal laser microscopy to determine surface roughness. Results show that all CAs of the granular solids exceeded that of the hydrophobized microscope slide (103°). The crushed glass had the largest CA (125°). With all three granular solids, there was an increase in CAs as particle size decreased. In addition, as particles became more angular, CAs increased. The influence of shape on wettability became more predominant as particle size decreased. The surface roughness parameter, Ra, was investigated and shown to be sensitive to both the size and shape of the particles. A decrease in Ra from 95.4 to 34.1 μm increased CAs from 107 to 125°. A similar change in CA was shown to correspond to an increase in void fraction from 40.7 to 77.4%. Our results have practical implications for the optimum use of soil by enhancing or suppressing water repellency. Highlights: How do the physical properties of granular solids such as soil influence their wettability? Effects of physical properties of particles on CAs were investigated when isolated from effect of chemistry. Particle shape becomes more important in gauging wettability as particle size decreases. Wettability of granular solids may be physically controlled by specific particle characteristics.

AB - The wettability of granular solids such as soil is known to depend primarily on two factors: their inherent chemistry and their physical properties, such as their particle size, particle shape and surface roughness. Nevertheless, the distinctive physical properties of such materials have not been fully explored to gauge their wettability. In this study, the difference in wettability between a flat solid (microscope slide) and three granular solids, namely glass beads (GB), Leighton Buzzard Sand (LBS) and crushed Glass (CG), which have different physical properties, were examined. The effect of chemistry was isolated by strongly hydrophobizing the above materials by treatment with dimethyldichlorosilane. Wettability measurements were made by measuring the water–solid contact angle (CA) by the sessile drop method after adhering one layer of uniformly oriented granular solids on to double-sided adhesive tape initially attached to a microscope slide. Techniques for particle characterization included sieving for particle size, dynamic image analysis for particle shape and confocal laser microscopy to determine surface roughness. Results show that all CAs of the granular solids exceeded that of the hydrophobized microscope slide (103°). The crushed glass had the largest CA (125°). With all three granular solids, there was an increase in CAs as particle size decreased. In addition, as particles became more angular, CAs increased. The influence of shape on wettability became more predominant as particle size decreased. The surface roughness parameter, Ra, was investigated and shown to be sensitive to both the size and shape of the particles. A decrease in Ra from 95.4 to 34.1 μm increased CAs from 107 to 125°. A similar change in CA was shown to correspond to an increase in void fraction from 40.7 to 77.4%. Our results have practical implications for the optimum use of soil by enhancing or suppressing water repellency. Highlights: How do the physical properties of granular solids such as soil influence their wettability? Effects of physical properties of particles on CAs were investigated when isolated from effect of chemistry. Particle shape becomes more important in gauging wettability as particle size decreases. Wettability of granular solids may be physically controlled by specific particle characteristics.

UR - http://www.scopus.com/inward/record.url?scp=85045407583&partnerID=8YFLogxK

U2 - 10.1111/ejss.12555

DO - 10.1111/ejss.12555

M3 - Article

AN - SCOPUS:85045407583

VL - 69

SP - 698

EP - 709

JO - European Journal of Soil Science

JF - European Journal of Soil Science

SN - 1351-0754

IS - 4

ER -