Date of Award

12-2006

Degree Name

Master of Science

Department

Chemical and Paper Engineering

Department

Paper Engineering, Chemical Engineering and Imaging

First Advisor

Dr. John Cameron

Second Advisor

Dr. Peter Parker

Third Advisor

Dr. Jan Pekarovic

Access Setting

Masters Thesis-Open Access

Abstract

The benefit of caustic treatment on changing cellulose properties has long been known. When the treated pulp is later intended for use in personal or in health care product industries, it is important that all residual chemicals are removed and that the pure cellulose or carbohydrate portion of the pulp remains. The removal is usually facilitated by washing. Due to the low caustic concentration in the washing filtrates the removal of the excess water by standard techniques such as evaporation would not be economical.

The main objective of this investigation was to evaluate the concept of using reverse osmosis for recovery of caustic soda (NaOH) from filtrates generated by washing of the treated pulp. This was achieved by assessing membrane separation effectiveness (selectivity) and productivity (flux) measured at different levels of caustic solution concentration. In addition, initial testing of the membrane longevity in retaining both separation selectivity and productivity was evaluated.

Initial investigation demonstrated that the reverse osmosis is capable of concentrating the diluted solution of NaOH. The flux values for 1 % NaOH solution at 800 psi transmembrane pressure and an average temperature of 25°C was measured at 85 l/hr.m2 range with over 85% salt rejection. The membrane tested showed no deterioration in performance over the period of 50 hours of running and retained its performance characteristics after exposure to NaOH solution for period of 45 days.

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