Anders Strand

Phase Distribution of Resin and Fatty Acids in Colloidal Wood Pitch Emulsions at Different pH-Levels

The distribution of resin and fatty acids (RFAs) between the water phase and the lipophilic phase in colloidal pitch emulsions was determined as a function of pH. Model pitch emulsions were prepared and agitated at different pH, temperature, and NaCl concentration. After filtration, the concentration of dissolved RFAs in the water phase was determined. The experimental data were used for calculation of pKlw, that is, the pH at which 50% of the acids are dissolved in the water phase. At pH 3, all of the RFAs were associated with the colloidal droplets. The resin acids were dissolved at lower pH than the fatty acids. Among the resin acids, dehydroabietic acid had the lowest pKlw. The pKlw of fatty acids depended greatly on the chain length and degree of unsaturation. Fatty acids with more than 20 carbon atoms had a low water solubility even above pH 10. Increasing the NaCl concentration increased the pKlw. The kinetics of the phase distribution was very rapid.

Influence of Pitch Composition and Wood Substances on the Phase Distribution of Resin and Fatty Acids at Different pH Levels

Pitch emulsions were prepared to mimic the colloidal wood resin system in paper mill process waters. The phase distribution of resin and fatty acids (RFAs) between the colloidal lipophilic droplets (l) and the water phase (w) were determined as pKlw values. The effect of triglyceride to RFA ratio on pKlw values was studied, to determine if seasonal variations in wood extractives influence their phase distribution. The effect of water-soluble hemicelluloses on pKlw values was also determined. The pKlw values of the RFAs were lower in emulsions with a low triglyceride to RFA ratio. Addition of water-soluble galactoglucomannans also lowered the pKlw values of the RFAs.

Selective purification of bleached spruce TMP process water by induced air flotation (IAF)

Abstract The environmentally benign closure of water systems in paper mills leads to the problem of accumulation of dissolved and colloidal wood substances (DCS) in process water. Notably, pitch affects the pulp and paper production negatively and increases the demand for additional treatment of the process water. In the present article, the purification of thermomechanical pulping process water from the alkaline peroxide bleaching stage has been investigated, with the induced air flotation (IAF) in focus. The following parameters were considered concerning the IAF efficiency to remove detrimental substances: concentration of cationic foaming agent, pH value, calcium concentration, and temperature. The amounts and characteristics of residual DCS were determined by gas chromatography and turbidity measurements. Residual concentrations of the foaming agent dodecyltrimetylammonium chloride were determined by electrospray ionization mass spectrometry. Up to 90% of pitch was removed, whereas hemicelluloses, which are important in preventing pitch problems, remained in the waters. Up to 70% of the pectic acids accounted for the high cationic demand of the process waters were removed by optimization of the IAF parameters. The presented separation process gives new opportunities to a selective purification of the process waters.

The use of calcium hydroxide as alkali source in peroxide bleaching of kraft pulp

The feasibility of replacing sodium hydroxide with calcium hydroxide in peroxide bleaching of kraft pulp was assessed. The bleaching experiments were carried out in small scale on two different starting pulps, with a preliminary study and a more narrow follow-up study. The preliminary study showed that the required amount of Ca(OH)2 was quite low compared to NaOH. The follow-up study showed that the same brightness gain and decrease in yellowness as 1% NaOH were achieved with 0.25% Ca(OH)2, which could result in savings of 80-85% on the cost of bleaching alkali. Replacing NaOH with Ca(OH)2 resulted in similar optical and mechanical properties as the reference pulp. The concentration of total organic carbon in the bleaching waters was in the same size range with NaOH and Ca(OH)2. This study indicates that alternative alkali sources can be used in the peroxide bleaching stage of

The effect of chemical additives on the strength, stiffness and elongation potential of paper - OPEN ACCESS

The effects of wet-end additions of cationic starches and/or carboxymethyl cellulose (CMC) on paper properties was determined by papermaking trials. The aim of this study was to mitigate the distinctive decrease in strength and stiffness due to unrestrained drying by addition of wet-end additives, while maintaining the extraordinarily high stretch potential of papers after unrestrained drying. Addition of the different polysaccharides increased the tensile index and density of the paper. The largest incgtreases in tensile index and stiffness were seen when combining cationic starches with CMC. With certain combinations of cationic starch and CMC, it was possible to increase the tensile index and stiffness of the paper, while maintaining the high elongation at break after unrestrained drying. To complement the results from the papermaking trials, adsorption of cationic starches and CMC onto cellulose nanofibril model surfaces was studied by QCM-D and SPR techniques. The additives adsorbed onto cellulose surfaces as soft gels, containing a large amount of coupled water. Adsorption of soft and malleable polysaccharide layers in the fiber-fiber joints enhanced the paper properties significantly on a macroscopic level. The softest and most swollen polysaccharide layers resulted in the largest increases in tensile index and stiffness of paper ADDRESSES OF THE AUTHORS: Anders Strand (anders.strand@abo.fi), Anna Sundberg (anna.sundberg@abo.fi), The Laboratory of Wood and Paper Chemistry, Åbo Akademi University, Porthaninkatu 3, FI-20500, Turku, Finland. Elias Retulainen (elias.retulainen@vtt.fi), Kristian Salminen (kristian.salminen@vtt.fi), Antti Oksanen (antti.oksanen@vtt.fi), Jarmo Kouko (jarmo.kouko@ vtt.fi), Annika Ketola (Annika.ketola@vtt.fi), VTT, Koivurannantie 1, FI-40400 Jyväskylä, Finland. Alexey Khakalo (alexey.khakalo@aalto.fi), Orlando Rojas (orlando.rojas@aalto.fi), Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, FI-00076, Espoo, Finland Corresponding author: Anders Strand