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Abstract

The deposition rate of colloidal pitch onto hydrophobic and hydrophilic model surfaces was measured
at the solid–liquid interface by impinging jet microscopy (IJM) and the effect of cation specificity in
solution on deposition was quantified. On both model surfaces, the pitch deposition was slightly faster
with calcium ions than with magnesium at the same concentration (800 mg/L). This concentration is
around twice the critical coagulation concentration.
The rate of colloidal pitch deposition on hydrophobic surfaces was far greater (up to a 2.5 times) than on
hydrophilic surfaces for both salts. Contact angle measurements inferred that in the air-surface environment,
the hydrophobicity of the surface does not affect its affinity for pitch suggesting molecular mobility
within the pitch colloid. IJM shows variation in the pitch shape on the model surfaces. On hydrophilic
surfaces, the pitch particle size for both salts ranges from 0.33 to 0.35 m while for hydrophobic surfaces
the particle size is 5 times higher for calcium salt than for magnesium salt. Film thinning or spreading
of the pitch particles occurred on the hydrophobic surfaces with calcium and to a lesser extent with
magnesium salt.

Item Type:	Article
Authors/Creators:	Lee, R and Garnier, G and Lewis, T and Richardson, DE and Van de Ven, TGM and Stack, KR
Keywords:	Pitch Impinging jet Liquid solid interface Hydrophilic Hydrophobic Deposition Soft colloid Surface Cation
Journal or Publication Title:	Colloids and Surfaces A: Physicochemical and Engineering Aspects
ISSN:	0927-7757
DOI / ID Number:
Additional Information:	The definitive version is available at http://www.sciencedirect.com
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