Background of This Series
Dispersing Powders in Liquids, by Ralph D. Nelson, Jr.
(Elsevier Science Publishers B.V., 1988) was originally published
to accompany courses that the author taught to industrial technologists
over a two-decade period. The book was quite popular. All copies
of the first edition were sold, the publisher re-issued it in 1993,
and most of the second printing were also sold. In 2001 the publisher
gave the copyright back to the author, who has now given
Educational Resources for Particle Technology a license
to post an updated version on the Web as a series of articles.
Dedication
The book and these articles are a memorial tribute to my colleagues
and companions in research and development from 1976 to 1981
at Du Pont's Colored Pigments Research Center at 256 Vanderpool Street in
Newark, New Jersey. I thank the senior scientists, who
provided a professional atmosphere and pleasant community within
which I learned much about dispersing powders in liquids:
Gerald H. Aldridge
Kenneth Batzaar
Albert R. Hanke
James Higgins
Julius Jackson
Edward Klenke
Howard Matrick
Benjamin H. Perkins
Ernest A. Stefancsik
Ronald L. Sweet
Robert F. White
I also thank my laboratory technicians, who worked on a very broad array
of laboratory experiments and plant trials with care,
perseverance, dignity, good-humor, and tolerance:
Anthony Barski
Ira van Emburgh
John Fox
John Gill
Joseph M. LoPrete
James J. A. O'Leary
Kenneth Ryder
Charles Tiazkun
Many others too numerous to note played supporting roles in introducing
me to the wonderful (and often frustrating) world that is the industrial
production of particulate material.
THE TOPIC UNDER DISCUSSION
A slurry (often called a dispersion) consists of small particles
suspended in a liquid. Since most untreated particles tend to
stick together when they collide, the preparation of a stable
dispersion requires that we add dispersants to prevent
agglomeration. Through thse articles I hope to help you understand
the factors that cause agglomeration and dispersion in a slurry
and to provide some guidance for selecting and optimizing the
dosage of a surfactant that will produce a stable dispersion of a
specific powder in a specific liquid.
The field of surface science has become very active over the past
quarter century. Several new categories of surfactants have been
developed and commercialized, allowing better control of industrial processes
and improved product performance. Many new instruments have been
developed to monitor low concentrations of surfactants in the
slurry environment and to better characterize particles in highly-loaded
dispersions. Improved process control techniques allow closer control
of slurry properties, better process operability, and better products.
This series of articles should be a useful resource for those who
teach slurry technology or powder dispersion courses to students who are
either engineers recently graduated from college or managers recently
transferred to plants that handle slurries. When Terence Allen asked me
to write a volume in the series titled Handbook of Powder Technology,
I welcomed the twin opportunities of improving my notes and reaching a wider
audience. The republication of the book as a series of articles on the
ERPT Web site allows revision based on longer experience and
also makes the material available around the globe.
I hope you enjoy the presentation.
A FEW WORDS ABOUT MYSELF
After earning degrees in chemistry from Colby College and
Princeton University, I spent two years as a post-doctoral fellow
with the U.S. National Bureau of Standards (which was later renamed
the National Institute of Science and Technology). For eight years I
professed physical and analytical chemistry at Middlebury College,
Brown University, and West Virginia University (where I
also earned a degree in Chemical Engineering). I then joined the
Du Pont company to practice chemical engineering. For eight
years I provided technical support to the manufacture of colored
pigments. In 1982 I became a company-wide consultant in
the field of slurry technology, gathering, teaching, and applying
the information, materials, equipment, and expert advice
required to solve slurry problems.
QUESTIONS ADDRESSED BY THIS TEXT
The six articles in this series address the following questions
at an introductory level and are intended to provide the reader
with a basic understanding of the concepts and terminology
found in the primary technical literature and in vendor advertizements.
Part 1
== a. Introduction:
What problems arise in industrial processes due to
the presence of particles in liquids or their interaction with
liquids? What resources are available to provide training,
information, discussion, or personal assistance in solving such
problems?
== b. Particle Structure:
What do the various structures found in clumps of
particles look like? What terms are commonly used to describe them?
== b. Annotated Bibliography [for the series]
Part 2
== a. Particle Physics:
How are atomic-level forces related to the attractions
and repulsions among particles? How do the various contributions
to particle interaction depend on slurry composition?
== b. Tables of Solid Properties
== c. Tables of Liquid Properties
== d. Units, Constants, and Symbols
Part 3
== a. Surface Chemistry:
What are the major chemical classes of particles,
liquids, and surfactants. What are the molecular structures of
typical commercial surfactants? What sorts of chain length
distributions and chemical mixes are present in industrial
surfactants?
== b. Tables of Surfactant Properties
== c. Surfactant Manufacturers
Part 4
== a. Surface Thermodynamics:
How is interfacial energy accounted for in
thermodynamic formulas? What factors affect adsorption from
solution onto a surface?
Part 5
== a. Flocculation and Coagulation:
How is the rate of flocculation of charged particles
related to solution composition? What factors affect micelle
formation and steric stabilization?
== b. Selecting a Dispersant:
What steps should be followed in selecting, testing,
and optimizing the dose of a dispersant?
Part 6
== Tests that Characterize a Dispersion:
What tests are available for characterizing the degree
of dispersion? What instruments can be used to analyze the
chemicals in the bulk and in the solid-liquid interface of a
slurry?
Sections of Part 1 of the Series
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