Date of Award
Bachelor of Science
Paper Science and Engineering
When water is filtered through paper under constant pressure, the flow rate decreases with time, even if distilled water is used as the permeating fluid. On the basis of previous literature,·possible causes of this effect were thought to be fiber swelling, the presence of microscopic bubbles in the water, electrical forces, or structures formed by water molecules and ionic impurities.
Experimentation showed that there is a blocking agent present in the distilled water which causes the decrease in flow rate. These particulate agents are denser than water, and have a greater affinity for cellulose than for glass. The particulates have a positive charge associated with them, and it is possible that some amount of electrolyte may be physically or chemically bound to them.
It was observed that filtration of water through ordinary laboratory filter paper can result in decreasing the conductivity of t he water. Three possible mechanisms were proposed, although on the basis of this study alone the exact nature of the conductivity reducing effect can not be determined.
The electrical potential difference that may easily measured between the two side of a filter paper as water flows through it is actually a complex combination of the affects of several sources. The most important of these sources are the streaming potential and the accumulation of charged particulates.
Geddes, Daniel J., "Variables Influencing the Filtration of Water through Paper" (1980). Paper Engineering Senior Theses. 220.