Mari Kallioinen

Recovery of galactoglucomannan from wood hydrolysate using regenerated cellulose ultrafiltration membranes.

Hemicelluloses show promise as a renewable source of raw material for various industrial processes. In this study, galactoglucomannan was recovered from pressurized hot water extract of spruce-sawdust in two steps using hydrophilic regenerated cellulose ultrafiltration membranes having different molecular weight cut-off values. The first step was concentration of galactoglucomannan (GGM) by ultrafiltration using a flat sheet unit and the second step was purification of the retained galactoglucomannan by diafiltration using reverse osmosis filtered water. The highest GGM retention (88%), purity (63%) and recovery (70%) were achieved with the UC005 membrane (cut-off value 5-kDa) at a volume reduction (VR%) of 86%. The UC010 and UC030 membranes (cut-off values 10- and 30-kDa, respectively) partly separated xylan from GGM. Generally, diafiltration did not improve the purity of the GGM due to overlapping of the GGM and lignin molar mass distributions and the fact that most of free low molar mass lignin had already been removed in the concentration filtration step. However, by diafiltration, partial removal of xylan and complete removal of monosaccharides from the GGM rich concentrate was achieved.

Enhanced membrane filtration of wood hydrolysates for hemicelluloses recovery by pretreatment with polymeric adsorbents

In this study adsorption of foulants from birch and pine/eucalyptus wood hydrolysates on two polymeric adsorbents was studied aiming to reduce the membrane fouling. The effect of the pretreatment of hydrolysate on polyethersulphone membrane performance was studied in dead-end filtration experiments. Adsorption pretreatment improved significantly filtration capacity and decreased membrane fouling. Especially high-molecular weight lignin was efficiently removed. A multistep adsorption pretreatment was found to reduce the amount of adsorbent required. While large adsorbent amount was shown to increase flux in filtration, it was found also to cause significant hemicellulose losses.

Production and recovery of monosaccharides from lignocellulose hot water extracts in a pulp mill biorefinery.

Processing of hemicelluloses obtained with pressurized hot water extraction (PHWE) from Scots pine to monosaccharides and other chemicals was investigated experimentally. A process scheme consisting of ultrafiltration, acid hydrolysis, and chromatographic separation was proposed and evaluated. A two-stage ultrafiltration was found necessary for efficient fractionation of the wood extract. It was shown that the monosaccharides can be released from a concentrated hemicellulose fraction with sulfuric acid hydrolysis without a significant loss of yield due to decomposition of monosaccharides. Acid hydrolysate was successfully fractionated with ion exchange chromatography and the hydrolysis acid was recovered for reuse. The product fractions obtained include polyphenols and high molar mass hemicelluloses (from UF stage 1), arabinose (from UF stage 2), as well as acetic acid and a mixture of monosaccharides (xylose, galactose, mannose, glucose) from chromatography.

Influence of Ultrasonic Treatment on Various Membrane Materials: A Review

Ultrasound treatment is a feasible option for membrane cleaning but its exploitation is possible only if membranes withstand the treatment. In this review an overview of the literature concerning the membrane tolerance to ultrasonic irradiation is provided. The amount of available information concerning stability of membranes under exposure to ultrasound is limited. The tolerance to ultrasonic irradiation has been evaluated only for some membrane materials. The most examined material, polyvinylidenefluoride, stands up well to ultrasonic treatment compared to other tested materials. However, experimental arrangements differ significantly from each other and the comparison of membrane tolerances is challenging. The results of the review reveal that standardized test methods are needed for getting comparable information on membrane tolerances to ultrasound.

Effect of High Filtration Temperature on Regenerated Cellulose Ultrafiltration Membranes

Abstract The hydrophilicity of regenerated cellulose (RC) ultrafiltration (UF) membranes could be utilized in industrial processes even more than today if there was more information on their thermal stability. Therefore, in this study two different RC UF membranes were used in a temperature range from 15 to 70°C in order to evaluate their performance stability at high temperature. The experiments were performed in neutral, alkaline, and acidic conditions. The influence of temperature on pure water permeability, observed Dextran retention, and membrane structure were used as evaluation criteria. According to the results the tested membranes could be used at 70°C in the tested conditions for several days. The results, however, indicated also that the use in acidic and alkaline conditions at 70°C might shorten the operational life of the membranes.

Industrial membrane processes in the treatment of process waters and liquors.

A review on pulp and paper industrial membrane processes using a variety of modules and processes is presented. Membranes are mostly used today to purify process waters and to recover coating colours. Ultrafiltration using tubular membrane modules or cross-rotational (CR) filtration has been widely applied for the purification of process waters. The reuse of UF membrane permeate has decreased the fresh water consumption to lower than 6 m³/t of paper in some paper machines. Some industrial membrane processes also recover valuable products from different streams (e.g lignosulphonates). Membranes are also combined with biological degradation processes in some paper mills. Nanofiltration has been used to purify the effluents discharged from the activated sludge process. At least two reverse osmosis plants purify river water to be used as raw water in the mill. Furthermore, advantages of different membrane modules and the current ways to treat membrane concentrate are discussed.

Assessment of the micellar-enhanced ultrafiltration process with a tight UF membrane for the removal of aniline from water

AbstractMicellar-enhanced ultrafiltration (MEUF) is a promising method to remove low molecular weight (LMW) organic contaminants from water. In this work, a series of experiments were conducted in order to evaluate the efficiency of an MEUF process for the removal of aniline (as LMW organic contamination) using a 1 kDa molecular weight cut-off polyethersulfone membrane and sodium dodecyl sulfate (SDS) as an anionic surfactant. Furthermore, the effect of various parameters such as aniline and surfactant concentration, operating pressure, temperature, agitation velocity, the presence of a nonionic surfactant (Brij 35), and the pH of feed on the rejection of aniline and SDS, and relative permeation flux have been examined. In the presence of a nonionic surfactant, the maximum rejection of aniline (approximately 80%) was obtained. The results of this study also revealed that although the complete retention of aniline was not achievable, the MEUF process could, however, be utilized to facilitate aniline remova...

Membrane technologies for water treatment and reuse in the pulp and paper industries

Water and water quality are an essential part of the production of pulp, cardboard, and paper. In this chapter some possibilities for using membranes to purify effluents and recirculate waste and process waters are reviewed. Driving forces to use membranes and barriers as well as challenges are discussed in the introduction. Furthermore, a discussion on process water and effluent quality leads readers to understand the demands that pulp and paper industry process waters and effluents set on membranes and filters. In this chapter mostly industrial applications are reviewed, focusing on membrane processes and their performances in specific applications. The applications are divided into the following main topics, depending on the aim of the applied membrane process: purification of wastewaters, membrane processes to circulate process waters, the simultaneous purification of water and recovery of valuable materials, and the purification of raw water.

Comparative evaluation of various lignin determination methods on hemicellulose- rich fractions of spruce and birch obtained by pressurized hot-water extraction (PHWE) and subsequent ultrafiltration (UF)

Abstract Various lignin determination methods have been applied to hemicellulose-rich wood extracts obtained after pressurized hot-water extraction (PHWE) and membrane ultrafiltration (UF). In focus were the chlorine number (Cl no.) method, the acetyl bromide method, and the four modifications of the Klason lignin determination, such as the KCL, TAPPI, LAP, and Goldschmid methods. The furfural (F) and hydroxymethylfurfural (HMF) concentrations in the acid hydrolysates were also determined. The mass balances of the fraction were calculated with respect to the contents of dry solids and lignin, including the acid-soluble lignin. The reliability of the methods was evaluated based on the lignin mass balances and the gross chemical composition of the extracts. Although the results were dependent on the method applied, the lignin mass balance calculations yielded similar results in general.

High Precision UTDR Measurements by Sonic Velocity Compensation with Reference Transducer

An ultrasonic sensor design with sonic velocity compensation is developed to improve the accuracy of distance measurement in membrane modules. High accuracy real-time distance measurements are needed in membrane fouling and compaction studies. The benefits of the sonic velocity compensation with a reference transducer are compared to the sonic velocity calculated with the measured temperature and pressure using the model by Belogolskii, Sekoyan et al. In the experiments the temperature was changed from 25 to 60 °C at pressures of 0.1, 0.3 and 0.5 MPa. The set measurement distance was 17.8 mm. Distance measurements with sonic velocity compensation were over ten times more accurate than the ones calculated based on the model. Using the reference transducer measured sonic velocity, the standard deviations for the distance measurements varied from 0.6 to 2.0 μm, while using the calculated sonic velocity the standard deviations were 21–39 μm. In industrial liquors, not only the temperature and the pressure, which were studied in this paper, but also the properties of the filtered solution, such as solute concentration, density, viscosity, etc., may vary greatly, leading to inaccuracy in the use of the Belogolskii, Sekoyan et al. model. Therefore, calibration of the sonic velocity with reference transducers is needed for accurate distance measurements.