Performance assessment of membrane separation technologies to recover water and chemical resources from segregated ECF bleaching effluents in Pinus radiata kraft pulp production

摘要

The aim of this study was to assess the performance of membrane separation to recover water and chemical resources from segregated bleaching effluents in cellulose production. Acid and alkaline effluents from Pinus radiata kraft pulp bleaching were obtained from local mills, and subjected to ultrafiltration (UF), nanofiltration (NF) and Reverse osmosis (RO) using a membrane filtration system Alfa Laval LabStak ® M20 with a range of 0.036-0.72 m2 of membrane area. UF cutoffs around 1, 2, 5, 10 and 20 KDa were used, whereas NF featured retention ≥ 98% MgSO4 and 90-98% NaCl for RO. Experiments were conducted in «concentration mode» and «recirculation mode». Fouling, and solid-liquid interaction, such as z potential and contact angles were determined. Membranes surface morphology was determined by scanning electron spectroscopy. In the case of UF and NF processes complete blockage, standard, intermediate, cake filtration models, and combined models at constant pressure and flow were determined. The Chen fouling potential model was used to describe RO performance. All permeate and retentate effluents were characterized on the basis of physicochemical and toxicological parameters. Results show that alkaline and acid lines present quite different responses to membrane separation. The application of membrane separation processes as part of a water and chemicals recovery strategies is discussed under the light of experimental findings obtained here. It is concluded that such technologies could be applied providing that membrane physical-chemical properties are carefully selected according to the type of effluent to be treated.