Browsing by Author "Vuorinen, Tapani"
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- Activation of TEMPO by ClO2 for oxidation of cellulose by hypochlorite — Fundamental and practical aspects of the catalytic system
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2017-06-30) Pääkkönen, Timo; Pönni, Raili; Dou, Jinze; Nuopponen, Markus; Vuorinen, TapaniBromide-free TEMPO-catalyzed oxidation of the primary alcohols by sodium hypochlorite (NaOCl) does not proceed without a prior activation of the catalyst. Here were demonstrate an immediate in situ activation of the catalyst with an equimolar addition of chlorine dioxide (ClO2) relative to TEMPO. Sodium bromide (NaBr) had a similar role in activating the catalyst although NaBr was needed in excess and the activation took several minutes depending on the dosage of NaBr. The activation method, or the concentration of NaBr, did not affect the bulk oxidation rate. The selectivity of the ClO2 initiated oxidation remained high up to NaOCl addition of 3 mol/kg bleached birch kraft pulp after which additional loss in yield and depolymerization of cellulose were emphasized with negligible increase in carboxylate content. A carboxylate content of 0.8–1 mol/kg, sufficient for easy mechanical fibrillation of the pulp, was achieved under mild conditions with NaOCl addition of 2-2.5 mol/kg pulp. - The activity and stability of tertiary amine catalysts in the presence of hypochlorous acid
Kemian tekniikan korkeakoulu | Master's thesis(2018-08-28) Dawson, OwainHypochlorous acid is an electrophilic oxidizing agent capable of reacting with a range of unsaturated organic substrates. Previously, these reactions have been shown to be catalysed by the use of a tertiary amine, and Hcat hardwood pulp bleaching stages using the tertiary amine DABCO, as well as its derivative CM-DABCO, have proved efficient. Within this work, a range of DABCO-derivative structures were synthesised, and their catalytic abilities and stabilities were tested via the use of stopped-flow UV-Vis spectroscopy. DABCO-derivatives produced in this work all involved mono-N-substitution, and generally high yields could be achieved in simple synthetic routes. Derivative structures tested included allyl (AL), carboxymethyl (CM), carboethoxymethyl (CEM), carbamoylmethyl (AA) and 2-hydroxyethyl (EA) groups. The pKa of the tertiary amine group within these were measured, and found to each be between 3.0 and 3.4, close to the second pKa of DABCO itself (2.97). Both pH and substrate structure were found to have a significant impact on the catalytic ability of all the tested structures. Due to the chlorinating action of Cl2 at pH 3, and the large difference between pH and DABCO-derivative catalyst pKa at pH 7, generally low catalytic factors were found at these pH values. At pH 5, higher catalytic factors could be found, with a catalyst pKa closer to 5 producing an increased catalytic ability. The substrate structure affects the rates of catalysis but not the order of activities between the different catalysts. CM-DABCO was the most active derivative for all substrates at pH 5, and it was concluded that further increases to the catalyst pKa could further improve the results obtained. Unlike DABCO, all the synthesised derivatives were shown to be close to fully stable for up to 10 seconds of pre-incubation with hypochlorous acid. Stability is concluded then to not be a concern in the selection and design of an optimal DABCO-derivative catalyst structure. - Addition of Ascorbic Acid or Purified Kraft Lignin in Pulp Refining
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2016-02) Vänskä, Emilia; Vihelä, Tuomas; Johansson, Leena-Sisko; Vuorinen, TapaniThe effects of two pulp pretreatments, impregnation with ascorbic acid (AA) or purified kraft lignin (KL), on bleached pulp refining were investigated by examining and testing handsheets made from these pulps. The AA pretreatment of the pulp amplified the depolymerization of the cellulose and notably impaired the strength properties of the pulp handsheets. The effects were enhanced upon the combination of the AA pretreatment and intensive refining. Furthermore, heat treatments (at 225 degrees C, 30 min, in water vapor atmospheres of 1 and 75% (v/v)) promoted the depolymerization of cellulose and the total color difference in the AA impregnated handsheets more than for the KL impregnated and reference handsheets. In contrast to AA, the KL pretreatment of the pulp improved the burst index stability of the refined pulp handsheets after the humid thermal treatment (75% (v/v)). In addition, the total color difference of the KL impregnated handsheets was lower than the AA impregnated and reference handsheets. - Advanced vibrational spectroscopy in surface analysis
Sähkötekniikan korkeakoulu | Licentiate thesis(2013) Kivioja, AnttiIn this licentiate thesis work a new non-destructive surface analysis method is introduced, which for the first time is based on total internal reflection (TIR) Raman spectroscopy and attenuated total reflectance infrared (ATR-IR) techniques. Together with the total internal reflection phenomenon, capable to acquiring information concerning the different molecular species present, the method creates opportunities to exploit new advanced applications. Over the past decades ATR-IR spectroscopy has become a well-known and routine method, and widely utilized in many laboratories, whereas the potential of TIR Raman spectroscopy has largely been neglected and therefore not fully exploited to date due to the predominant interest in other techniques, such as surface enhanced Raman spectroscopy (SERS). The principle of the method is illustrated in the first publication applied to the measurement of thin and ultra-thin polymer films (<100 nm). The technique was found to be an essential tool in analysing multi-layered polymer films, which have a soft substrate as the underlying layer. The separation/removal of ink components within a set thin offset ink film, following absorption into a porous coated paper substrate, is analysed in the second publication. Although the pore size distribution of the substrate was larger than the used probe depth the techniques provided information, regarding the retained portion of components in the ink film, which is an important advantage for paper design and print quality improvement. Critical design parameters, such as the required definition of providing sufficient capillary-driven offset ink component separation during setting, can be monitored to minimize the potential for printed image smearing and so to maximize the print rub resistance. - Amine catalysed HOC1 treatment for birch pulp
School of Chemical Engineering | Master's thesis(2012) Niinivaara, ElinaThe presence of hexenuronic acid (HexA) in pulp is disadvantageous. It has been found to cause an increased consumption of electrophilic bleaching chemicals, scaling in bleaching equipment and aid in the yellowing of pulp/paper, among others. Although methods such as hot acid hydrolysis exist with which to remove HexA, tertiary amine catalysis may have the potential to provide an alternative and equally, if not more, efficient method. The first objective of this work was to explore the possibility of using the tertiary amine, 1,4-diazabicyclo(2.2.2]octane (Dabco), to catalyse the removal of hexenuronic acid using hypochlorous acid. The second objective was to determine the possibility of bleaching oxygen delignified birch pulp to full brightness using two four-stage bleaching sequences. The sequences that were the focus of this thesis were A-EOP-D1-P and Dabco/H-EOP-D1-P. The sequence used as a reference was D0-EOP-D1-Ep-D2. The theoretical section of this thesis will describe the different components of wood, provide an introduction on kraft pulping and bleaching, describe the benefits of hexenuronic acid removal and will introduce the concept of tertiary amine catalysis. In the experimental section, two major topics were considered. The first of these was the optimization of the use of Dabco according to four key parameters; temperature, active chlorine charge, Dabco dosage and ph. The second was the exploration of the two four stage bleaching sequences already mentioned. It was found that Dabco was capable of extensively increasing the HexA removal potential of hypochlorous acid through a chlorammonium cation formed between Dabco and hypochlorous acid. The system was also capable of removing lignin from the pulp. As of yet, the four-stage bleaching sequences explored in this thesis were not able to bleach the oxygen delignified birch pulp to full brightness. - Anionic nanofibrillar cellulose production optimization
Kemian tekniikan korkeakoulu | Master's thesis(2023-12-12) Porvali, VilleAnionic nanofibrillated cellulose (aNFC) is a wood-based nanomaterial characterized by its remarkable mechanical and shear-thinning properties, high surface area, transparency, and exceptional biocompatibility. aNFC is produced from selectively oxidized cellulose by wet processing methods, which lead to a hydrogel composed of an entangled network of cellulose nanofibers, that can be used as a scaffold for 3D cell culture and tissue engineering. The nanofibers mimic ECM (extracellular matrix) and provide structural support for cell attachment and subsequent tissue development. This thesis focused on the optimization of the aNFC manufacturing process, with a particular focus on its TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation process, nanofibrillation of the oxidized cellulose, and the removal of air bubbles, all while remaining aseptic manufacturing practices. Target of the TEMPO-mediated oxidation optimization was to increase the degree of oxidation and to shorten the duration of it by adjusting the reaction conditions. Target of the nanofibrillation optimization was to study how the modified oxidation conditions, and degree of oxidation, affect the nanofibrillation efficiency and the aNFC. Moreover, the target was to reduce fluctuations in aNFC consistency that had been observed to occur during the manufacturing process. Target of the air bubble removal was to remove entrapped air bubbles from the aNFC without compromising homogeneity of the hydrogel. The target degree of oxidation was reached, and the duration of the oxidation was reduced by half. Two alternative methods with lower chemical dosages and longer oxidation durations were also introduced. All of the methods yielded aNFC with high transparency, good rheometric properties, efficient nanofibrillation and provided excellent cell viability ratio for the studied HepG2 human liver cancer cell line. Consistency fluctuations of the aNFC were also significantly decreased, although the underlaying factors contributing to this phenomenon remain unknown. Furthermore, preheating of aNFC syringes was observed to aid removal of air. In summary, the research conducted on this thesis significantly enhances the quality and efficiency of aNFC manufacturing for biomedical applications. The optimized process provides significantly faster manufacturing with significantly lower consistency fluctuations, and yields aNFC with significantly higher rheometric properties, and slightly lower turbidity in comparison with the production methods employed prior to this thesis. - Antioxidant effect of phenols in the oxidation of reducing sugars by oxygen
School of Chemical Engineering | Master's thesis(2010) Björk, CarolinaThe oxidation of reducing sugars under alkaline conditions has been studied in this work. The main reason for this is the need to reduce the degradation 01 carbohydrates during the pulping and bleaching processes. Many theories have been presented based on kinetic research and product analysis. The latest research asserts that the oxidation of reducing sugars under alkaline conditions happens in two steps via enediol ions and radicals. The antioxidant effect of phenols is usually based on donation of a hydrogen atom to the radical and thus stopping the radical chain reaction. This work resulted in significantiy improved measurement repeatability, the repeatability of the experiments was initially poor. In the course of the work, it emerged that oxygen was dissolving in the measured solution during the measurement. Based on this problem, a new reactor was planned in which the measured solution would not be in direct contact with the surrounding air. The measurements with dihydroxy acetone had weak repeatability. This was most likely not caused by the measurement method, which was working well for glucose. The oxygen concentration was measured and reaction rates were calculated based on the oxygen consumption. The reaction rates were used to approximate the ratios between the reaction rate constants according to the reaction rate equation. The measurements with glucose were conducted in two temperatures to evaluate the effect of temperature changes on the oxidation reaction. The oxygen consumption rate for the glucose measurements was almost constant until all oxygen in the solution had been consumed. Usually, the reaction rate diminishes when the concentration of one reactant approaches zero. This work showed that phenols possess good ant oxidative properties in the oxidation of reducing sugars by oxygen. - Antioxidant properties of lignin in paper
Kemian tekniikan korkeakoulu | Master's thesis(2013-10-15) Vihelä, TuomasEnvironmental concerns have forced packing industry to consider alternative biodegradable raw materials replacing plastics in packages. Adapting of cellulosic fibers in the packages is limited due to their lack of thermal resistance. During mechanical treatment of fibers, the formation of highly reactive free radicals increases. These free radicals may degrade cellulose thus reducing strength properties of the paper. It has been proposed that under the mechanical stress lignin forms phenoxy radicals. The phenoxy radicals can act as a radical scavenger, reacting with the phenoxy or other radicals. This has led researchers to discuss whether antiradical properties of lignin exist when lignin is a component of the fiber matrix. Therefore, the objective of this study is to increase the knowledge of the possible antioxidant properties of lignin in a paper. Another objective is to investigate the mechanical and thermal degradation of lignin-containing pulp sheets. The mechanical treatments were applied to pulps containing different amount of residual lignin: unbleached (UNB), oxygen delignified (SBP) and fully bleached (FBP) softwood kraft pulps. Additionally fully bleached softwood kraft pulps with ascorbic acid (FBP-A) and alkali lignin (FBP-L) treatments were monitored. Refinings of UNB and SBP pulps were conducted with the industrial conical refiner, whereas the chemically treated pulps were refined with the laboratory Hollander refiner. Subsequently, the thermal treatments were conducted for pulp sheets made from these pulps at 225 ˚C and volume share of water vapor of 1 and 75%. The treatment times for UNB and SBP pulp sheets were 20 and 60 minutes, while FBP, FBP-A and FBP-L sheets were treated for 30 minutes in the presence of 1 and 75% water vapor. Finally, chemical, mechanical and optical properties of the pulp sheets were monitored with carbohydrate, viscosity, burst strength, tensile strength, zero-span, ISO-brightness and light adsorption coefficient analyses. Clear differences between thermal stability of UNB and SBP pulp sheets were not found in the analyses. However, the mechanical properties and viscosity of more lignin-containing UNB pulp sheets deteriorated less than SBP pulp sheets during thermal treatment in the presence of water vapor. According to the results from Hollander refined pulps, FBP-L pulp sheet had better mechanical properties and higher viscosity after the refining and thermal treatments than FBP and FBP-A pulp sheets. On the contrast, these properties for the ascorbic acid treated (FBP-A) pulp sheet were inferior. The thermal degradation of all the pulp sheets was accelerated by water vapor. The strength properties of the FBP-L pulp sheet indicated that lignin may have worked as an antioxidant against the mechanical and thermal degradation of the pulp sheet. - Application for electrochemically formed biocides in papermaking
Helsinki University of Technology | Master's thesis(2008) Sievänen, Jenni - AUTOMATED CHEMOMETRIC PROCEDURE FOR QUANTITATIVE AND QUALITATIVE ANALYSIS OF CONFOCAL RAMAN IMAGES
Poster(2015) Bertinetto, Carlo; Galvis Rojas, Leonardo; Jokela, Anne; Vuorinen, Tapani; Virkajärvi, PerttuA chemometric procedure for the analysis of confocal Raman images of biological samples is presented. First, the data matrix undergoes a pre-processing consisting of: removal of cosmic ray peaks, baseline correction [1], wavenumber restriction, noise smoothing, normalization, Principal Component (PC) compression and cluster analysis. The pre-processed data is then unmixed using Band-Target Entropy Minimization (BTEM) [2], a multivariate algorithm for extracting the spectra of pure components within a mixture. It works by seeking the linear combination of PCs that satisfies the following criteria: i) non-negativity of spectral intensities; ii) minimum entropy (which implies maximum simplicity); iii) presence of a certain peak (band-target). BTEM is applied to the whole spectral matrix, as well as to cluster-averaged spectra: the clustering fuzzes some details on major components, but highlights information on other minor ones. All the obtained solutions (one for each band-target) are post-screened to discard replicates and incorrect outcomes. The final set of selected spectra is used to produce images of the relative concentration for each component by a least-squares fit. Several steps of this procedure are automated by in-house written algorithms to minimize user intervention and subjective determination of parameters. This methodology enables the non-invasive mapping of various substances on the same image. In the shown examples taken from various plant tissues, up to seven components were identified, including some with overlapping peaks or small concentration. No a priori chemical knowledge on the sample is needed, although it can be useful for the final post-screening. Because this procedure allows for finding out which compounds are present in a sample (provided that they give a Raman signal), it is also a powerful tool for qualitative analysis. Moreover, it can provide information on certain molecular bonds from relevant peaks in the extracted spectra and on the orientation of ordered structures from their anisotropic response [3] [1] C. G. Bertinetto, and T. Vuorinen, Applied spectroscopy, 68(2):155–164, 2014. [2] E. Widjaja, C. Li, W. Chew, and M. Garland, Analytical chemistry, 75(17):4499–4507, 2003. [3] L. Galvis, C. Bertinetto, U. Holopainen, T. Tamminen, and T. Vuorinen, Journal of Cereal Science. Submitted. - AUTOMATIC BASELINE RECOGNITION FOR FAST CORRECTION USING CONTINUOUS WAVELET TRANSFORM
Poster(2013) Bertinetto, Carlo; Vuorinen, TapaniA method to perform an automatic and quick recognition of peak and baseline regions in a spectrum is presented. Its characteristics make it especially suitable for the treatment of large amounts of data of similar type, such as those coming from a high-throughput instrument. This algorithm is based on the Continuous Wavelet Transform and is effective on any kind of spectrum in which the baseline is smoother than the rest of the signal. Its parameters are automatically determined using the criteria of Shannon entropy and statistical distribution of noise. If the data are properly grouped into sets of analogous measurements, no user intervention is required. This method was assessed on simulated spectra with different noise levels and baseline amplitudes. It can be combined with various fitting methods for baseline correction. In this study, it was used together with an iterative polynomial fitting to successfully process a real Raman image of 40000 pixels in about 2 1/2 hours. - Automatic Baseline Recognition for the Correction of Large Sets of Spectra Using Continuous Wavelet Transform and Iterative Fitting
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2014) Bertinetto, Carlo G.; Vuorinen, Tapani - Automatisoitu menetelmä sulfaattikeiton aikana liukenevien hiilihydraattipolymeerien määrittämiseksi
Helsinki University of Technology | Master's thesis(1998) Österman, KirstiTämä diplomityö liittyy TEKESin hiilihydraattiohjelmaan, jossa selvitetään mm. puun polysakkaridien fysikaalisen käyttäytymisen ja ligniinihiilihydraattikompleksien esiintymisen ja muodostumisen merkitystä ligniinin liukenemista hidastavina tekijöinä. Tämän työn tavoitteena on kehittää sulfaattikeittoliuoksen polysakkarideille selektiivinen määritysmenetelmä ja soveltaa sitä edelleen. Mustalipeän hiilihydraattipitoisuuden määrittämiseen kokeiltiin kahta tapaa. Polysakkarideista muodostuu perjodaattihapetuksessa ja sitä seuraavassa happamassa hydrolyysissä glyoksaalia ja tetroosia tai glyseraldehydiä. Toinen määritysmenetelmistä perustuu glyoksaalin ja 3,4-diaminobentsoehapon kondensoitumistuotteen aiheuttaman absorption spektrofotometriseen mittaukseen (330 nm). Vaihtoehtoinen tapa oli määrittää syntyneiden tetroosin tai glyseraldehydin pitoisuudet neokuproiinitestissä. Se perustuu testissä käytetyn kuparin hapetusluvun muutokseen. Menetelmässä Cu[2+]-ioni pelkistyy Cu[+]-ioniksi. Tämä pelkistyminen havaitaan värinmuutoksesta ja absorbanssilukeman muutoksesta 450 nm:n kohdalla UV:lla. Glyoksaalin ja 3,4-diaminobentsoehapon kondensoitumiseen perustuva menetelmä toimi hyvin koeputkiolosuhteissa, mutta automaattisella virtausanalysaattorilla tämä tapa ei antanut hyväksyttäviä tuloksia. Neokuproiinitesti onnistui malliainekokeissa koeputkioloissa. Virtausanalysaattorilla dekstraanikokeet antoivat luotettavat tulokset. Mustalipeänäytteitä analysoitiin kaksi sarjaa: koivukeitto- ja mäntykeittosarjat. Koivukeiton mustalipeänäytteiden hiilihydraattipitoisuuden määritykset onnistuivat selvästi paremmin kuin mäntykeiton keittoliuosmääritykset. Analysaattorin tulosten tarkkuus kontrolloitiin samoista näytteistä tehdyillä vertailumäärityksillä, jotka suoritettiin kaasukromatografisesti. - Availability of the feedstocks for scalable advanced biofuel production in Finland
Kemian tekniikan korkeakoulu | Master's thesis(2020-08-18) Yliaho, EssiEU’s renewable energy policies are aiming to increase the share of renewable energy in transportation. With respect to the EU policies, Finland, among the other Member States, has implemented its own advanced biofuel targets to be achieved during the 2020s. Tightening legislation is increasing advanced biofuel demand among the Member States, and new production capacity is required in order to achieve the targets. However, there are techno-economic challenges related to the advanced biofuel production which must be overcome in order to enable sustainable and profitable advanced biofuel production. One of the biggest challenges are the feedstocks, and especially their availability. In this thesis, advanced biofuel feedstock options in Finland were examined. Investigation covered different forest industry by-products, including forestry residues, bark, sawdust and sawdust-based pellets, forest industry sludges, black liquor and kraft lignin, and pre-hydrolysis liquor from the dissolving pulp production. The feedstocks were investigated through secondary and primary market research in order to understand feedstocks’ availability and techno-economic properties. According to the multi-criteria decision analysis conducted based on the market research results, forest industry sludges, forestry residues, bark and sawdust showed the highest potential for the advanced biofuel production in Finland. These feedstocks were further investigated through scenario analysis in order to understand the most likely development patterns of the feedstock availability and price. - Uuteaineiden käyttäytyminen koivusulfaattisellun valmistuksessa
Helsinki University of Technology | Master's thesis(2003) Lehtimaa, Tuula - Bioproducts from filtrate oxidation
Kemian tekniikan korkeakoulu | Master's thesis(2022-10-18) Heikkilä, Roni - Bioproducts from lignin oxidation
Kemian tekniikan korkeakoulu | Master's thesis(2021-08-24) Vehmaa, Kaisa - Bioproducts from pulp mill side streams
Kemian tekniikan korkeakoulu | Master's thesis(2023-08-22) Hakim, Md Azizul - Bleaching of eucalyptus kraft and soda-anthraquinone pulps
Helsinki University of Technology | Master's thesis(2009) Rauhala, TiinaTässä diplomityössä tutkittiin kahta eri sellunkeittomenetelmää, jotka olivat perinteinen sulfaattikeitto ja sooda-antrakinonikeitto (SAQ). SAQ-keiton ongelma on sen huonompi valkaistavuus verrattuna sulfaattikeittoon, eräänlainen vaaleuden yläraja, jota on vaikea ylittää. Tässä työssä tutkittiin, voidaanko SAQ-sellun vaaleutta lisätä korkealämpöisen happaman hydrolyysin (A-vaihe) avulla. Työn kirjallisuusosa keskittyy ligniinikemiaan keiton aikana sekä sulfaattikeiton ja SAQ-keiton eroihin. Työssä on myös tutkittu kirjallisuutta, joka käsittelee ligniinin ja heksenuronihapon (HexA) reaktioita happaman hydrolyysin aikana, sekä kirjallisuutta valkaisun kemiasta. Kokeellisessa osassa eukalyptushakkeesta tehtiin kaksi eri keittoa (sulfaatti ja SAQ) ja keiton jälkeen sellu valkaistiin seuraavalla sekvenssillä: O-A-Eop-D. A-vaiheen lämpötilaa ja kestoa vaihdettiin. Jokaisen valkaisuvaiheen jälkeen sellu analysoitiin perinteisin menetelmin: kappa, ISO-vaaleus, viskositeetti ja suodoksen väri. Lisäksi HexA:n määrä mitattiin 0- ja A-vaiheiden jälkeen. Sellunäytteet mitattiin myös spektrosopisin menetelmin, jotta saataisiin selville tapahtuuko ligniinissä ja HexA:ssa muutoksia valkaisun aikana. Tulokset osoittivat, että SAQ-sellu ei saavuta yhtä korkeaa vaaleutta kuin sulfaattisellu, vaikkakin SAQ-sellun vaaleus nousi suhteellisesti enemmän. SAQ-ligniini on tummempaa johtuen keitto-olosuhteista. SAQ-sellussa on luultavasti myös enemmän muita värillisiä rakenteita. Näytteet, joille oli tehty korkeassa lämpötilassa A-vaihe, saavuttivat korkeamman vaaleuden. Lopullinen vaaleus ei kuitenkaan riipu A-vaiheessa poistuneen HexA:n määrästä vaan luultavasti korkean lämpötilan A-vaiheen aikana HexA tai ligniini reagoi tuntemattomalla tavalla. Toinen syy sulfaattisellun helpompaan valkaistavuuteen on, että siinä on enemmän syringyylirakenteita, mikä tekee ligniinistä helpommin valkaistavaa. Syringyylirakenteiden suurempi määrä johtuu lievemmistä keitto-olosuhteista. - Eukalyptussulfaattimassan valkaisu A/D-, D/A- ja Z/D alkuisilla sekvensseillä
Helsinki University of Technology | Master's thesis(2003) Pekkanen, LauriTämän työn tavoitteena oli tutkia A/D-, kuumaa D- ja Z/D-vaihetta ensimmäisenä vaiheena, valkaistaessa happidelignifiotua eucalyptussulfaattimassaa. Tavoitteena oli löytää eri menetelmillä suoritettavien laboratoriovalkaisujen eroja ja tutkia niiden suuruusluokkaa. Lisäksi haluttiin tutkia suodosten kierrätyksen avulla valkaisun vesikierron sulkemisen vaikutusta vaaleuteen ja suodoksien COD-tasoon. Kirjallisuuskatsauksessa käydään läpi alkuvalkaisusekvensseihin liittyviä asioita. Tähän sisältyvät heksenuronihappojen selektiivinen poisto A-vaiheen ja kuuman klooridioksidivaiheen avulla sekä klooridioksidi- ja otsonivaiheen yleiset toimintamekanismit. Lisäksi kirjallisuusosa käsittelee A-, D ja Z-vaiheiden yhteisvaikutusta A/D-, D/A- (kuuma D-vaihe), Z/D-ja D/Z-vaiheissa lyhyiden valkaisusekvenssien ensimmäisenä vaiheena. Valkaisukokeissa selvitettiin A/D- ja kuuman D-vaiheen sekä Z/D-vaiheen optimaaliset kemikaaliannokset. Valkaisumenetelmiä tutkittiin erilaisilla muovipussissa ja MC-mikserissä suoritetuilla valkaisukokeilla. Menetelmäkokeissa pidettiin kemikaaliannokset samoina alkuvalkaisun ajan ja pyrittiin muuttamaan lähinnä esi- ja välipesujen avulla valkaisun suoritusta, sekä muovipussivalkaisuissa että mikserissä suoritetuissa valkaisuissa. Suodosten kierrätyskokeissa kierrätettiin suodosta A/D-, D/A- ja Z/D-vaiheista aina takaisin kyseisen vaiheen laimennukseen. Ensimmäisten valkaisuvaiheiden jälkeen massat valkaistiin loppuvaaleuteen EpD-sekvenssillä, jossa haettiin tavoitevaaleutta 89 % -ISO. Tutkittaessa kokonaisklooridioksidin kulutusta havaittiin että menetelmäkokeissa optimaalinen klooridioksidiannos pitäisi aina määrittää koko sekvenssin loppuvaaleuden pohjalta. Havaittiin että työssä suoritetuista valkaisuista monet eivät olleet optimaalisia, kun oli pyritty yhtenäistämään annostusta useille koesarjoille. Kunkin tyyppiselle menetelmälle on olemassa oma optimijako klooridioksidin annostuksessa vaikka sekvenssit olisivat hyvin lähellä toisiaan rakenteellisesti. Verrattaessa kaikkia menetelmäkokeita havaittiin, että muovipussivalkaisut eivät yltäneet halutulle vaaleustasolle samalla D0-vaiheen ClO2-annoksella, kuin MC-mikserissä suoritetut valkaisut. Suodoksen kierrätys A/D ja kuuman D vaiheen sekvensseillä aiheutti n. 30 % kasvun kokonais- ClO2-annoksessa. Voitiin vahvistaa että A/D vaihe s8astaa n. 30 % ja kuuma D-vaihe n. 20 % klooridioksidia, verrattaessa konventionaaliseen D vaiheeseen. Tuloksista näkyi myös, että kuuman D-vaiheen COD taso oli jostain syystä merkittävästi A/D-vaiheiden tasoa suurempi.