Pretreatment of wood extract significantly improves ultrafiltration capacity

Membrane filtration can separate and recover valuable dissolved components such as hemicelluloses from wood. However, membrane filtration has a rapidly declining filtration capacity due to harmful compounds, such as lignin, which wood extracts contain. The dissertation by Elsi Strand, M.Sc.(Tech.), demonstrates that filtration capacity can in many cases be improved manifold by the pretreatment of wood extracts prior to filtration.

Hemicelluloses can be extracted from wood before the actual pulp manufacturing process. The amount of hemicelluloses must be minimised especially in the manufacture of dissolving pulp, which must have as high a cellulose content as possible. From such wood extracts, hemicelluloses can be recovered only by ultrafiltration. In ultrafiltration, pressure is applied to filter a solution through a semipermeable membrane.

Strand studied pretreatment methods which removed harmful compounds from a wood extract either by adsorption or oxidation. Oxidation degrades the compounds, whereas in adsorption liquid or gaseous substances attach themselves to the surface of a solid substance. Both methods yielded excellent results and significantly improved the filtration capacity when hemicelluloses were recovered from wood extracts.

In traditional pulp mills, a part of hemicelluloses are currently combusted for power generation. However, hemicelluloses are more useful in, for instance, the manufacture of bio-based products, as the amount of energy released in combustion is relatively small compared to power obtained from lignin, for example. 

Elsi Strand's dissertation in the field of chemical technology is entitled Enhancement of ultrafiltration process by pretreatment in recovery of hemicelluloses from wood extracts. It will undergo a public examination on 14 January 2016 at 12.00 noon at Lappeenranta University of Technology, auditorium 1383. The opponent is Docent Frank Lipnizki from Alfa Laval, Denmark. The custos is Professor Mika Mänttäri from LUT.

The dissertation has been published in the university's research series Acta Universitatis Lappeenrantaensis, publication number 679. ISBN 978-952-265-894-4 and ISSN 1456-4491. The dissertation is available in the LUTPub database of Lappeenranta University of Technology at Printed copies can be purchased from the Aalef bookstore, tel. +358 44 744 5511 or kirjakauppa(at), and online from LUT Shop,

Doctoral candidate
Name: Elsi Strand
Year and place of birth: 1986, Riihimäki
Domicile: Lappeenranta
Education: Master of Science (Technology), Chemical Technology
Career history: Doctoral Student, LUT, 2010-2014

Further information

Elsi Strand,, tel. +358 44 575 8159