title: Membrane treatment of alkaline bleaching effluents from elementary chlorine free kraft softwood cellulose production.
abstract: This paper reports experimental results on the sequential use of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) to fractionate alkaline extraction bleaching effluents from kraft cellulose production. The aim was to unveil the way key pollutants are distributed when subjected to sequential UF/NF/RO membrane separation processes. Alkaline bleaching effluents were obtained from a local pinewood-based mill, featuring elementary chlorine free bleaching to produce high-brightness cellulose. The experimental system was based on a laboratory-scale membrane system, DSS LabStak® M20 Alfa Laval, using Alfa Laval UF and NF/RO membranes, operated at a constant transmembrane pressure (6 bar for UF membranes and 32 bar for NF/RO membranes), at 25°C. Results show that 78% chemical oxygen demand (COD) and total phenols, 82% adsorbable organic halogens (AOX) and 98% colour were retained by UF membranes which have molecular weight cut-off (MWCO) above 10 kDa. In all, 16% of original COD, total phenols and AOX, and the remaining 2% colour were retained by UF membranes within the 1 to 10 kDa MWCO range. Chloride ions were significantly present in all UF permeates, and RO was required to obtain a high-quality permeate with a view to water reuse. It is concluded that UF/NF/RO membranes offer a feasible option for water and chemicals recovery from alkaline bleaching effluents in kraft pulp production.
authors.affiliation: a Chemical Engineering Department , University of Concepción , P.O. Box 160-C, Correo 3, Concepción , Chile.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Oñate
authors.forename: Edgard
authors.initials: E
authors.lastname: Rodríguez
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Bórquez
authors.forename: Claudio
authors.initials: C
authors.lastname: Zaror
mesh_terms: D057886:Bleaching Agents / Q000302:isolation & purification*; D002482:Cellulose; D004785:Environmental Pollutants / Q000032:analysis; D008567:Membranes, Artificial; D008970:Molecular Weight; D014462:Ultrafiltration; D014865:Waste Disposal, Fluid / Q000379:methods*; D014876:Water Pollution / Q000517:prevention & control*; D014934:Wood
chemical_list: D057886:Bleaching Agents; D004785:Environmental Pollutants; D008567:Membranes, Artificial; D002482:Cellulose
keywords: alkaline bleaching effluent; chemicals recovery; elementary chlorine free cellulose; sequential UF/NF/RO membrane system; water recovery