John C. Berg
CHEM E 455
Laboratory techniques, equipment, and underlying fundamentals in surface and colloid science. Experiments in the measurement of surface tension, adsorption, wetting and spreading, colloid properties, emulsion preparation and stability, electrophoresis, and interfacial hydrodynamics. Recommended: CHEM E 326; CHEM E 330. Offered: ASp.
The behavior of fluid interface systems (capillarity), fine particle dispersions, fibers and thin films is dominated by the properties of their interfaces. Such systems play critical roles in many fields: chemical industry, biotechnology, chemical engineering, food science, material science, agriculture and medicine, to name a few. The underlying science of interfacial phenomena is rarely treated in university courses in chemistry, physics or engineering, and the practitioner is left to solve problems in the area without the needed background. This course seeks to develop the scientific background of the subject, to trace the consequences of the science into industrial practice and everyday experience, and to teach laboratory techniques for property measurement and system characterization.
Student learning goals
General method of instruction
The course may be taken for either one credit or for three credits. The one-credit option consists of two 50-minute lectures per week (with accompanying readings from a required textbook). Four, open-book 15-minute quizzes are given during the quarter. The three-credit option consists of the lectures plus one 4-hour laboratory session per week. A total of 20 experiments are provided, in four groups of five each. Each student will work on only one experiment per group, for a total of four during the quarter. The three-credit option has an enrollment limited to 20 students. Students work in lab teams of two students each, assigned by the instructor, and different for each experiment. Each experiment requires two weeks, and is followed with the preparation of a brief written report. In the final week of class, each student will prepare and deliver a 10-minute oral presentation to the group based on one of the experiments. A listing of the experiments follows:
I. Measurement of Surface and Interfacial Tension
A. Measurement of surface tension by detachment or partial immersion methods: the du NoŁy ring and Wilhelmy slide. B. Surface tension and adsorption isotherm of n-butanol/water solutions using the drop weight method. C. Interfacial tension between water and decane solutions of lauric acid using the drop volume method. D. Measurement of surface tension using the sessile drop method. E. Determination of the surface equation of state for a myristic acid monolayer on water using the Langmuir film balance.
II. Adsorption, Wetting and Spreading at the Solid-Fluid Interface
A. Determination of the wetting properties of solids using the contact angle goniometer. B. Measurement of advancing and receding contact angles using the fiber balance. C. Adsorption of acetic acid from solution onto activated carbon; surface area determination using the BET method. D. Separation by preferential wetting: flotation. E. Measurements of wicking rates in capillary tubes and in porous media.
III. Properties of Colloids and Dispersions
A. Determination of CMC by dye titration. B. Determination of CMC by conductivity. C. Aggregation of colloidal dispersions using electrolytes. D. Preparation of emulsions and testing for type; inversion and breaking. E. Determination of particle size distributions using the SediGraphģ and the disk centrifuge.
IV. Interfacial Hydrodynamics
A. Observation of the Marangoni effect during mass transfer using schlieren optics. B. Measurement of surface viscosity of surfactant monolayers using the deep channel method. C. Measurement of zeta potential by particle micro-electrophoresis. D. The extraction of a dye in an adsorptive bubble column. E. The influence of surface tension on the breakup of capillary jets.
The course desighned for seniors or graduate students in engineering or science curricula. University-level chemistry, physics and mathematics are essential. Undergraduate courses in thermodynamics and fluid mechanics are highly desirable.
Class assignments and grading
The lectures-only (one-credit) option has reading assignments, and four 15-minte quizzes; the full course option (three credits) has the same reading assignments and quizzes, plus four laboratory reports, and a 10-minute oral presentation.
Quizzes: 16% Written reports: 40% Lab. performance: 32% Oral report: 12% Attendance is also a factor.