Martin A. Hubbe, PhD , North Carolina State University
Progress during Years 1-3 of Project
We achieved significant progress in evaluating factors affecting permeation of probe molecules into very small pores, representing those that exist within a mineral bed.
A breakthrough was achieved in observing, for the first time, a trend towards more negative streaming potentials following placement of silica gel conditioned with cationic polyelectrolytes into aqueous polyelectrolyte-free solution in the presence of salt. The inferred polymer desorption is not ordinarily observed in cases where polyelectrolytes adsorb onto the outer surfaces of granular materials, but recent thermodynamic studies and simulation work have predicted such behavior in the case of pores that are smaller than the bulk-phase radius of gyration of a polyelectrolyte.
Our preliminary observations indicated that the presence of a layer of a high-mass polyelectrolyte coating the exterior surface of a nanoporous material can inhibit penetration of lower-mass probe molecules having the same electrical charge. Understanding and controlling such phenomenon can help to influence the progress of different solutes permeating through different zones of an oilfield operation.
Further project work concentrated on kinetic effects, carrying out confirmatory tests in the form of adsorption isotherms. One major review article has been published related to the field of work. Three project-related peer-reviewed articles have been produced.
Final Phase of Work: Practical Application
To derive further benefits of the work, application tests were carried out using selected cellulosic fibers as model mesoporous materials for sorption of simulated crude petroleum. The following factors were considered: type of fiber (including type of pulping, lignin removal, etc.), whether the substrate was dry or pre-wetted by water, the purposeful deposition of hydrophobic lignin onto the surfaces of fibers, and derivatization of fiber surfaces with long-chain alkyl agents. All the dry fibers were highly effective for uptake of the “spilled oil”, though hydrophobization generally had a negative effect on oil uptake. Hydrophobization by lignin deposition or alkylization favored oil uptake by pre-wetted fibers.
Impact of Work on Career of Investigator and Students
As a result of the PRF-funded project work, the principal investigators have been able to improve the fundamental depth of our research efforts. The technical content of the current work – related to permeation of polyelectrolytes in narrow pore spaces – has also been beneficial to us in forging some new research initiatives in the areas of environmental remediation and in the efficient dewatering of cellulosic fiber suspensions.
The graduate student who has undertaken most of the project work has benefitted greatly from the opportunity. In addition to learning to run gel permeation chromatography (GPC), streaming potential analysis, and adsorption isotherm experiments, she has become fluent in the analysis and interpretation of the data produced by such methods. She has earned a Master of Science degree, and will be very well prepared to start PhD work. A graduate student and two undergraduate students benefited from participation in the final phase of research.