Hanna Valkama
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Hanna Valkama has a total of 4 co-authors. Here are the top co-authors by number of shared publications:
- Buddhika Rathnayake
Environmental and Chemical Engineering Research Unit, Faculty of Technology, University of Oulu, P.O. Box 4300, FI-90014 Oulu, Finland
1 shared publication - Jasmiina Haverinen
Unit of Measurement Technology, Kajaani University Consortium, University of Oulu, P.O. Box 127, FI-87400 Kajaani, Finland
1 shared publication - Markku Ohenoja
Faculty of Technology Environmental and Chemical Engineering Research Unit Control Engineering Group University of Oulu P.O.Box 4300 90014 Oulu Finland
1 shared publication - Riitta Liisa Keiski
Environmental and Chemical Engineering, Faculty of Technology, University of Oulu, P.O. Box 4300, FI-90014 Oulu, Finland
1 shared publication
Latest Publications
- Open Access
Evaluation of Nanofiltration Membranes for the Purification of Monosaccharides: Influence of pH, Temperature, and Sulfates on the Solute Retention and Fouling
Furfural, acetic acid, and sulfates are found in the hemicellulose (HMC) fraction of lignocellulosic biomass. Separation of furfural, acetic acid, and sulfates from monosaccharides by four nanofiltration (NF) membranes was evaluated with a model solution of glucose, xylose, furfural, acetic acid, and sulfates. Results showed that Alfa Laval NF99HF is the most promising membrane to purify monosaccharides, with the retentions of xylose (85%), glucose (95%), and with the minimum sulfate retention. pH has the highest impact on the retention of all solutes and there is no significant effect of temperature on the retentions of sulphates and acetic acid. Lower pH and temperature are favored to maximize the monosaccharide retention and to remove acetic acid while retaining more furfural with the monosaccharides. Moreover, fouling tendency is maximized at lower pH and higher temperatures. According to the statistical analysis, the retentions of glucose, xylose, furfural, sulfates, and acetic acid are 95%, 90%, 20%, 88%, and 0%, respectively at pH 3 and 25 °C. The presence of sulfates favors the separation of acetic acid and furfural from monosaccharides.
Open AccessEvaluation of Nanofiltration Membranes for the Purification of Monosaccharides: Influence of pH, Temperature, and Sulfates on the Solute Retention and Fouling
Furfural, acetic acid, and sulfates are found in the hemicellulose (HMC) fraction of lignocellulosic biomass. Separation of furfural, acetic acid, and sulfates from monosaccharides by four nanofiltration (NF) membranes was evaluated with a model solution of glucose, xylose, furfural, acetic acid, and sulfates. Results showed that Alfa Laval NF99HF is the most promising membrane to purify monosaccharides, with the retentions of xylose (85%), glucose (95%), and with the minimum sulfate retention. pH has the highest impact on the retention of all solutes and there is no significant effect of temperature on the retentions of sulphates and acetic acid. Lower pH and temperature are favored to maximize the monosaccharide retention and to remove acetic acid while retaining more furfural with the monosaccharides. Moreover, fouling tendency is maximized at lower pH and higher temperatures. According to the statistical analysis, the retentions of glucose, xylose, furfural, sulfates, and acetic acid are 95%, 90%, 20%, 88%, and 0%, respectively at pH 3 and 25 °C. The presence of sulfates favors the separation of acetic acid and furfural from monosaccharides.