NANOFILTRATION OF BLEACHING PULP AND PAPER EFFLUENTS IN TUBULAR POLYMERIC MEMBRANES

A systematic investigation of the nanofiltration (NF) of alkaline blea ching effluent (El) from the pulp and paper industry is carried out th rough a first assessment of NF of model systems, namely, solutions of salts-NaCl and Na2SO4-and organic solutes-glucose, saccharose, and raf finose-which develop membrane-solute(s) interactions similar to those developed by the bleaching effluent. The ampholytic polymer of the mem brane active layer, under controlled feed conditions,develops a surfac e charge distribution which determines the membrane performance. The v erification of the effects of the anion valence and the feed concentra tion on the salts rejections, in accordance with the Donnan exclusion principle, is an important feature of this work. For the bleaching eff luent, the NF performance is strongly dependent on the pH due to the i nfluence of this parameter on the membrane surface charge. The contrib ution of this work toward the optimization of the NF operating conditi ons would allow for future scale-up of this separation process for E-1 effluent purification and water recovery in the pulp and paper indust ry.