Caustic Treatment of the Pulp: Caustic Recovery by Reverse Osmosis, 2006 Engineering, Pulping, & Environmental Conference

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The overall objective of this study is a systematic analysis of caustic treatment of bleached pulp, including corresponding mass and energy balances. A major focus of this investigation is to evaluate the caustic recovery. This paper describes an initial evaluation of a membrane separation processes - reverse osmosis (RO) - as potential candidate for caustic recovery. This testing was designed to obtain initial values for better understanding of the process and investigate the feasibility of reverse osmosis application for diluted caustic soda (NaOH) solution processing.

The investigation demonstrated that the reverse osmosis process is capable of concentrating the diluted solution of NaOH. The membrane tested showed no deterioration in performance over the period of testing - in excess of 50 hours. In addition, the membrane retained its separation and performance characteristics after continuous exposure to NaOH solution for a period of 7 days.