Date of Award
Master of Engineering (ME)
Dr. A. Benedek
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.
Horsti, Markku Seppo, "Ultrafiltration of Alkalilignin Through Dynamic Membranes Formed of Feed Constituents" (1976). Open Access Dissertations and Theses. Paper 418.