Applied Colloid and Surface Chemistry

Richard M. Pashley, Marilyn E. Karaman

• Publisher: Wiley
• Year: 2021
• Print ISBN: 9781119739128
• eBook ISBN: 9781119740018
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Physical & Theoretical Chemistry

An updated guide to the interaction between solids, liquids, and gases and their application to numerous everyday processes 

The revised and updated second edition of Applied Colloid and Surface Chemistry offers a comprehensive introduction to this interdisciplinary field that takes a practical approach and includes information on applications drawn from a wide range of industries. The easy-to-follow text contains new content that focuses on applications such as the prevention of propeller cavitation, industrial explosives, PFAS contamination, and bubble column evaporators.  

With contributions from noted experts on the topic, the book contains keynote sections written by practicing industrial research scientists, who highlight real-world industrial examples. These examples range from water treatment through to soil management as well as examples from the coatings and photographic industries. Designed as an accessible resource, the book separates the more demanding mathematical derivations from the main text. The text features approachable, structured chapters, learning objectives, tutorial questions with answers, and explanatory notes. This important book: 

• Offers a combination of physicochemical background, industrial, and everyday applications and experiments 
• Underlines the importance of colloidal sciences in science and industry 
• Presents real-world industrial applications  
• Includes tried and tested laboratory experiments  

Written for students of chemistry, materials science, and engineering, Applied Colloid and Surface Chemistry, Second Edition offers an updated guide to soft matter presenting the bridge between science, with proven laboratory experiments, and real-world industrial applications. 

1
Introduction

Introduction to the nature of colloids and the linkage between colloids and surface properties. The importance of size and surface area. Introduction to wetting and the industrial importance of particle size and surface modifications.

INTRODUCTION TO THE NATURE OF COLLOIDAL SOLUTIONS

The difference between macroscopic and microscopic objects is clear from everyday experience. For example, a glass marble will sink rapidly in water; however, if we grind it into sub‐micron‐sized particles, these will float or disperse freely in water, producing a visibly cloudy ‘solution’, which can remain stable for hours or days. In this process we have, in fact, produced a ‘colloidal’ dispersion or solution. This dispersion of one (finely divided or microscopic) phase in another is quite different to the molecular mixtures or ‘true’ solutions formed when we dissolve ethanol or common salt in water. Microscopic particles of one phase dispersed in another are generally called colloidal solutions or dispersions. Both nature and industry have found many uses for this type of solution. We will see later that the properties of colloidal solutions are intimately linked to the high surface area of the dispersed phase, as well as to the chemical nature of the particle’s surface.

Historical note: The term ‘colloid’ is derived from the Greek word for glue, ‘kolla’. It was originally used for gelatinous polymer colloids, which were identified by Thomas Graham in 1860 in experiments on osmosis and diffusion.

It turns out to be very useful to dissolve (or more strictly disperse) solids, such as minerals and metals, in water. But how does it happen? We can see why from simple physics. Three fundamental forces operate on fine particles in solution:

1. A gravitational force, tending to settle or raise particles depending on their density relative to the solvent.
2. A viscous drag force, which arises as a resistance to motion, since the fluid has to be forced apart as the particle moves through it.
3. The ‘natural’ kinetic energy of particles and molecules, which causes random Brownian motion.

If we consider the first two non‐random forces, we can easily calculate the terminal or limiting velocity, V, (for settling or rising, depending on the particle’s density relative to, say, water) of a spherical particle of radius r. Under these conditions, the viscous drag force must equal the gravitational force. Thus, at a settling velocity, V, the viscous drag force is given by: F_drag = 6πrVη = 4πr³g(ρ_p − ρ_w)/3 = F_gravity, the gravitational force, where η is the viscosity of water and the density difference between particle and water is (ρ_p − ρ_w). Hence, if we assume a particle‐water density difference of +1 g cm^‐3, we obtain the results:

r/Å	100	1000	10,000	10^5	10^6
r/μm	0.01	0.1	1	10	100
V/cm/sec	2 × 10^−8	2 × 10^−6	2 ×10^‐4	2 × 10^−2	2

Clearly, from factors (1) and (2), small particles will take a very long time to settle, and so a fine dispersion will be stable almost indefinitely, even for materials denser than water. But what of factor (3)? Each particle, independent of size, will have a kinetic energy, on average, of around 1 kT. So the typical random speed (ν) of a particle (in any direction) will be roughly given by:

Again, if we assume that ρ_p = 2 g cm⁻³, then we obtain the results:

r/Å	100	1000	10,000	10^5	10^6
r/μm	0.01	0.1	1	10	100
ν/cm/sec	10^2	3	0.1	3 × 10^−3	1 × 10^‐4

These values suggest that kinetic random motion will dominate the behaviour of small particles, which will not settle, and the dispersion will be completely stable. However, this point is really the beginning of ‘colloid science’. Since these small particles have this kinetic energy they will, of course, collide with other particles in the dispersi...

Table of contents

• Cover
• Table of Contents
• Title Page
• Copyright Page
• Dedication Page
• Preface
• About the Companion Website
• 1 Introduction
• 2 Surface Tension and Wetting
• 3 The Prevention of Fluid Cavitation
• 4 Thermodynamics of Adsorption
• 5 Surfactants and Self‐Assembly
• 6 PFAS Contamination
• 7 Emulsions and Microemulsions
• 8 Charged Colloids
• 9 Van Der Waals Forces and Colloid Stability
• 10 Bubble Coalescence, Foams and Thin Surfactant Films
• 11 Bubble Column Evaporators
• Appendices
• Index
• End User License Agreement