Date of Award

12-1976

Degree Type

Thesis

Degree Name

Master of Engineering (ME)

Department

Chemical Engineering

Supervisor

Dr. A. Benedek

Abstract

Membranes formed by constituents of ultrafiltration feed solutions on a support structure are called dynamic membranes. Lignin has the ability to form a self-rejecting membrane potentially useful for separating lignin from pulping wastes.

Lignin solutions and pulp mill wastes were circulated past support tubes at different operating conditions. A typical product flux was about 7 gal/ft²day with about 99% rejection. The effect of the feed solution concentration, the pore size of the support structure and the cross-flow velocity were small on the membrane performance. A temperature increase from 30ºC to 70ºC increased the product flux by 130%. A higher operating pressure increased the product flux only slightly above a critical pressure of about 80 psi. The product flux was highly dependent on the pH, being e.g. 30 gal/ft²day at pH2 and 7.5 gal/ftday at pH//.

Some chemical additives, reported to alter liquid conformation, were tested and the best results were given by addition of formaldehyde. It increased the product flux at pH2 from 30 gal/ft²day to 42 gal/ft²day. A pretreatment of the carbon support tubes by hydrochloric acid improved the product flux from 6 gal/ft²day to 16 gal/ft²day but the beneficial effect, in this case, was time dependent.


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