Improvement of pyrolysis oil quality by scrubbing

Diplomityössä tutkittiin kuuman pyrolyysihöyryn puhdistamista haisevista ja kevyistä haihtuvista yhdisteistä. Työn kirjallisuusosassa selvitettiin pyrolyysiöljyn kannattavuutta uusiutuvana energialähteenä. Lisäksi eri pesurityyppejä tarkasteltiin ja ja vertailtiin. Työn kokeellisessa osassa käytettiin kahta erilaista koelaitteistoa. Tuotteen talteenotossa vertailtiin reaktorilämpötilan ja raaka-aineen kosteuden vaikutusta pyrolyysisaantoihin. Komponenttien talteenotossa tutkittiin epästabiilien ja pistävän hajuisten yhdisteiden poistamista kuumasta pyrolyysihöyrystä. Raaka-aineena käytettiin kuusen metsätäh-dehaketta, joka sisältää runsaasti neulasia ja kaarnaa. Kokeet toteutettiin lämpötila-alueella 460 - 520 °C. Koelaitteistot koostuivat kaasun (N2) syöttöjärjestelmään kytketystä kuumasta ja kyl-mästä puolesta. Tuotteen talteenotossa kuuma pyrolyysihöyry jäähdytettiin ja otettiin talteen. Komponenttien talteenotossa tuote kerättiin suodattimelle ja metyleeniklo-ridiloukkuun. Tuotteiden koostumukset analysoitiin kaasukromatokrafilla. Korkeimmat orgaaniset saannot saatiin 480 °C reaktorilämpötilalla ja 8-9 p-% raaka-ainekosteudella. Pyrolyysiveden määrä putosi raaka-aineen kosteutta nostettaessa. Eri reaktorilämpötiloilla ja raaka-ainekosteuksilla ei ollut vaikutusta hiiltosaantoihin. Kaasusaannot (pääosin CO2, CO ja hiilivedyt) olivat noin 10 p-%. Komponenttien talteenotossa suodatin tukkeutui matalissa (< 250 °C) lämpötiloissa. Suodattimelle jäänyt materiaali oli pääosin neulasista ja kaarnasta peräisin olevia uuteaineita (pääosin hartsi- rasvahappoja) ja sokereita. Korkeimmissa lämpötiloissa (> 250 °C) uuteaineet läpäisivät suodattimen paremmin. 250 ja 300 °C:n lämpötiloissa suuri määrä lyhytketjuisia helposti haihtuvia epästabiileja ja haisevia yhdisteitä (ketoneja, furaani- ja furfuraalijohdannaisia jne.) jäi metyleenikloridi- ja metanoliloukkuihin.

Puupohjaisten kuitukomposiittien materiaalitekniset mahdollisuudet veneteollisuudessa

Tämän diplomityön tavoitteena oli selvittää puupohjaisten kuitukomposiittimateriaalien soveltuvuutta veneteollisuuden valmistusmateriaaliksi. Huviveneiden rakennusta säätelee huvivenedirektiivi ja lukuisat standardit. Standardien mukaan uusien materiaalien käyttö veneenrakennuksessa on mahdollista, mikäli materiaalin ominaisuudet todetaan muun muassa laboratoriotesteissä soveltuviksi kyseiseen käyttötarkoitukseen. Tutkimusta varten valmistettiin kuusi erilaista kuitukomposiittimateriaalia. Tutkimuksessa käytettiin myös neljän kaupallisen puumuovikomposiittivalmistajan materiaalia. Vertailumateriaaleiksi valittiin puuraaka-aineista mänty, saarni ja mahonki sekä muoviraakaaineista ABS – muovi. Tarkisteltaville materiaaleille määriteltiin standardien mukaisin testein taivutuslujuus, vetolujuus, Charpy – iskulujuus, Brinell – kovuus, veden absorptio sekä paksuusturpoama. Saatuja arvoja vertailtiin vertailumateriaalien kirjallisuudessa mainittuihin arvoihin. Puupohjaisten kuitukomposiittien ominaisuudet jäivät vertailumateriaalien vastaavista lukuun ottamatta Brinell – kovuutta. Taivutus- ja vetolujuuden osalta eräiden kaupallisten puumuovikomposiittivalmistajien ilmoittamat lujuusarvot olivat lähellä veneenrakennuksessa käytettyjen materiaalien vastaavia. Suurimpana yksittäisenä haasteena puukuitupohjaisilla kuitukomposiiteilla havaittiin Charpy – iskulujuus. Myös veden absorption saattaminen alhaiseksi havaittiin tärkeäksi veneilysovelluksissa. Ominaisuuksien kehittäminen on kuitenkin käytettävissä olevan tutkimustiedon perusteella mahdollista. Diplomityössä saatujen tulosten perusteella on puupohjaisilla kuitukomposiiteilla potentiaalia veneteollisuudessa. Jatkotutkimusta tulisikin kohdistaa materiaalin ominaisuuksien kehittämiseen.

Kaupallisten komposiittituotteiden materiaaliominaisuuksien määritys ja vertailu

Tässä kandidaatintyössä tutkittiin viiden kaupallisen puu-muovikomposiittituotteen säänkestävyyttä kolmen eri materiaaliominaisuuden avulla. Tuotteet olivat Suomessa markkinoilla olevia terassirakentamisen tuotteita ja niiltä mitattiin Charpy -iskulujuutta, veden absorptiokykyä ja värinmuutosta. Tuloksia verrattiin sekä keskenään, että muualla maailmassa tutkittujen kaupallisten tuotteiden kanssa. Tulosten perusteella havaittiin, että Suomen markkinoilla olevien tuotteiden säänkestävyys on erinomainen.

Surface characterization of chemically modified fiber, wood and paper

Inorganic-organic sol-gel hybrid coatings can be used for improving and modifying properties of wood-based materials. By selecting a proper precursor, wood can be made water repellent, decay-, moisture- or UV-resistant. However, to control the barrier properties of sol-gel coatings on wood substrates against moisture uptake and weathering, an understanding of the surface morphology and chemistry of the deposited sol-gel coatings on wood substrates is needed. Mechanical pulp is used in production of wood-containing printing papers. The physical and chemical fiber surface characteristics, as created in the chosen mechanical pulp manufacturing process, play a key role in controlling the properties of the end-use product. A detailed understanding of how process parameters influence fiber surfaces can help improving cost-effectiveness of pulp and paper production. The current work focuses on physico-chemical characterization of modified wood-based materials with surface sensitive analytical tools. The overall objectives were, through advanced microscopy and chemical analysis techniques, (i) to collect versatile information about the surface structures of Norway spruce thermomechanical pulp fiber walls and understand how they are influenced by the selected chemical treatments, and (ii) to clarify the effect of various sol-gel coatings on surface structural and chemical properties of wood-based substrates. A special emphasis was on understanding the effect of sol-gel coatings on the water repellency of modified wood and paper surfaces. In the first part of the work, effects of chemical treatment on micro- and nano-scale surface structure of 1st stage TMP latewood fibers from Norway spruce were investigated. The chemicals applied were buffered sodium oxalate and hydrochloric acid. The outer and the inner fiber wall layers of the untreated and chemically treated fibers were separately analyzed by light microscopy, atomic force microscopy and field-emission scanning electron microscopy. The selected characterization methods enabled the demonstration of the effect of different treatments on the fiber surface structure, both visually and quantitatively. The outer fiber wall areas appeared as intact bands surrounding the fiber and they were clearly rougher than areas of exposed inner fiber wall. The roughness of the outer fiber wall areas increased most in the sodium oxalate treatment. The results indicated formation of more surface pores on the exposed inner fiber wall areas than on the corresponding outer fiber wall areas as a result of the chemical treatments. The hydrochloric acid treatment seemed to increase the surface porosity of the inner wall areas. In the second part of the work, three silane-based sol-gel hybrid coatings were selected in order to improve moisture resistance of wood and paper substrates. The coatings differed from each other in terms of having different alkyl (CH3–, CH3-(CH2)7–) and fluorocarbon (CF3–) chains attached to the trialkoxysilane sol-gel precursor. The sol-gel coatings were deposited by a wet coating method, i.e. spraying or spreading by brush. The effect of solgel coatings on surface structural and chemical properties of wood-based substrates was studied by using advanced surface analyzing tools: atomic force microscopy, X-ray photoelectron spectroscopy and time-of-flight secondary ion spectroscopy. The results show that the applied sol-gel coatings, deposited as thin films or particulate coatings, have different effects on surface characteristics of wood and wood-based materials. The coating which has a long hydrocarbon chain (CH3-(CH2)7–) attached to the silane backbone (octyltriethoxysilane) produced the highest hydrophobicity for wood and wood-based materials.

Ultraviolet light protection and weathering properties of wood-polypropylene composites

The main aim of this thesis is to study the effect of pigments on the weathering properties of wood-polypropylene composites (WPC). The studied properties are color change, water absorption, thickness swelling and Charpy impact strength. The impact of weathering and UV exposure on WPCs was studied by using pigments and minerals as protective agents. The study shows that the pigments and/or mineral fillers can be used to improve the weathering properties of WPCs. The effect of pigments was found to vary with the type of pigment and the method of weathering. The black pigment, an inorganic carbon black master-batch, was found to be the most effective one in reduction of the discoloration of WPCs. By preventing discoloration, and further reducing the degradation of the surface of the WPC, the pigments were found to reduce the decrease in the impact strength after weathering. As well as UV protection, the moisture resistance is a significant factor affecting the durability of WPCs. The addition of mineral fillers was found to improve the moisture-related properties, such as water absorption and thickness swelling, of WPC significantly. According to the findings, addition of pigments and mineral fillers to wood-polypropylene composites appears to be beneficial: color stability and moisture resistance can be enhanced especially in outdoor weathering. The combined effect of black pigment (carbon black master-batch) and wollastonite as a mineral filler was found to bring about the most effective properties against weathering.

Research progress in wood-plastic composites: A review

The interest towards wood-plastic composites (WPCs) is growing due to growing interest in materials with novel properties, which can replace more traditional materials, such as wood and plastic. The use of recycled materials in manufacture is also a bonus. However, the application ofWPCs has been limited because of their often poor mechanical and barrier properties, which can be improved by incorporation of the reinforcing fillers. Nanosized fillers, having a large surface area, can significantly increase interfacial interactions in the composite on molecular level, leading to materials with new properties. The review summarizes the development trends in the use on nanofillers for WPC design, which were reported in accessible literature during the last decade. The effect of the nanofillers on the mechanical properties, thermal stability, flammability and wettability ofWPC is discussed.

Wet Oxidation of TMP Concentrated Paper Mill Process Water. Kinetics of the reaction

Työn tarkoituksena oli tutkia lämpötilan, paineen, pH:n ja katalyytin vaikutusta paperitehtaan TMP-konsentroidun prosessiveden märkähapetuksessa. Teoriaosio sisältää katsauksen sellu- ja paperiteollisuuteen, jätevesien käsittelyyn, nanosuodatuksen ja märkähapetusprosessin toimintaperiaatteet ja sovellukset hybriditeknologialle nanosuodatus-märkähapetuksessa. Empiirinen osa koostuu märkähapetuskokeista eri lämpötiloissa, paineissa, pH:ssa ja eri katalyyseillä. Työssä tutkittiin näiden vaikutusta kemialliseen hapenkulutukseen (COD), Biologiseen hapenkulutukseen (BOD), Välittömästi saatavana olevan biologisen hapenkulutukseen (IABOD), ligniiniin, täysin orgaanisen hiileen (TOC) ja rasvaliukoisten uuteaineiden (LWEs) pitoisuuteen. Tuloksina kokeellisesta työstä saatiin korkeimmat COD:n alenemat ja BOD/COD (biohajoavuus) suurimmilla lämpötilaolosuhteilla (COD:n alenema 70 % ja BOD/COD 97 % 200 °C:ssa ja hapen 10 bar osapaineella). Tutkimuksessa, jossa selvitettiin hapen osapaineen vaikutusta saatiin tuloksena, että hapen osapaineen kasvu parantaa orgaanisen kuormituksen poistoa: COD poisto oli olosuhteilla130°C, 5bar 5 %, olosuhteilla 130 °C, 15bar 15 %, olosuhteilla 170 °C, 5bar 20 % ja olosuhteilla 170 °C, 15bar 50 %. Lähes täydellinen LWEs –poisto saavutettiin 150 °C ja 10bar olosuhteilla, vaikka tässä lämpötilassa ei saavutettu korkeata orgaanisen kuormituksen poistoa. Emäksinen pH vaikutti suosivan hapettavia reaktioita, koska korkein COD:n poisto saavutettiin näissä olosuhteilla; kuitenkin alkalisen väliaineen tehokkuudelle löydettiin tärkeä lämpötilariippuvuus.

Modeling reaction kinetics and mass transfer in ozonation in water solutions

This dissertation is based on four articles dealing with modeling of ozonation. The literature part of this considers some models for hydrodynamics in bubble column simulation. A literature review of methods for obtaining mass transfer coefficients is presented. The methods presented to obtain mass transfer are general models and can be applied to any gas-liquid system. Ozonation reaction models and methods for obtaining stoichiometric coefficients and reaction rate coefficients for ozonation reactions are discussed in the final section of the literature part. In the first article, ozone gas-liquid mass transfer into water in a bubble column was investigated for different pH values. A more general method for estimation of mass transfer and Henry’s coefficient was developed from the Beltrán method. The ozone volumetric mass transfer coefficient and the Henry’s coefficient were determined simultaneously by parameter estimation using a nonlinear optimization method. A minor dependence of the Henry’s law constant on pH was detected at the pH range 4 - 9. In the second article, a new method using the axial dispersion model for estimation of ozone self-decomposition kinetics in a semi-batch bubble column reactor was developed. The reaction rate coefficients for literature equations of ozone decomposition and the gas phase dispersion coefficient were estimated and compared with the literature data. The reaction order in the pH range 7-10 with respect to ozone 1.12 and 0.51 the hydroxyl ion were obtained, which is in good agreement with literature. The model parameters were determined by parameter estimation using a nonlinear optimization method. Sensitivity analysis was conducted using object function method to obtain information about the reliability and identifiability of the estimated parameters. In the third article, the reaction rate coefficients and the stoichiometric coefficients in the reaction of ozone with the model component p-nitrophenol were estimated at low pH of water using nonlinear optimization. A novel method for estimation of multireaction model parameters in ozonation was developed. In this method the concentration of unknown intermediate compounds is presented as a residual COD (chemical oxygen demand) calculated from the measured COD and the theoretical COD for the known species. The decomposition rate of p-nitrophenol on the pathway producing hydroquinone was found to be about two times faster than the p-nitrophenol decomposition rate on the pathway producing 4- nitrocatechol. In the fourth article, the reaction kinetics of p-nitrophenol ozonation was studied in a bubble column at pH 2. Using the new reaction kinetic model presented in the previous article, the reaction kinetic parameters, rate coefficients, and stoichiometric coefficients as well as the mass transfer coefficient were estimated with nonlinear estimation. The decomposition rate of pnitrophenol was found to be equal both on the pathway producing hydroquinone and on the path way producing 4-nitrocathecol. Comparison of the rate coefficients with the case at initial pH 5 indicates that the p-nitrophenol degradation producing 4- nitrocathecol is more selective towards molecular ozone than the reaction producing hydroquinone. The identifiability and reliability of the estimated parameters were analyzed with the Marcov chain Monte Carlo (MCMC) method. @All rights reserved. No part of the publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the author.

Influence of reactant absorption and dissolution in heterogeneous precipitation processes

In this research work, the aim was to investigate the volumetric mass transfer coefficient [kLa] of oxygen in stirred tank in the presence of solid particle experimentally. The kLa correlations as a function of propeller rotation speed and flow rate of gas feed were studied. The O2 and CO2 absorption in water and in solid-liquid suspensions and heterogeneous precipitation of MgCO3 were thoroughly examined. The absorption experiments of oxygen were conducted in various systems like pure water and in aqueous suspensions of quartz and calcium carbonate particles. Secondly, the precipitation kinetics of magnesium carbonate was also investigated. The experiments were performed to study the reactive crystallization with magnesium hydroxide slurry and carbon dioxide gas by varying the feed rates of carbon dioxide and rotation speeds of mixer. The results of absorption and precipitation are evaluated by titration, total carbon (TC analysis), and ionic chromatrography (IC). For calcium carbonate, the particle concentration was varied from 17.4 g to 2382 g with two size fractions: 5 µm and 45-63 µm sieves. The kLa and P/V values of 17.4 g CaCO3 with particle size of 5µm and 45-63 µm were 0.016 s-1 and 2400 W/m3. At 69.9 g concentration of CaCO3, the achieved kLa is 0.014 s-1 with particle size of 5 µm and 0.017 s-1 with particle size of 45 to 63 µm. Further increase in concentration of calcium carbonate, i.e. 870g and 2382g , does not affect volumetric mass transfer coeffienct of oxygen. It could be concluded from absorption results that maximum value of kLa is 0.016 s-1. Also particle size and concentration does affect the transfer rate to some extend. For precipitation experiments, the constant concentration of Mg(OH)2 was 100 g and the rotation speed varied from 560 to 750 rpm, whereas the used feed rates of CO2 were 1 and 9 L/min. At 560 rpm and feed rate of CO2 is 1 L/min, the maximum value of Mg ion and TC were 0.25 mol/litre and 0.12 mol/litre with the residence time of 40 min. When flow rate of CO2 increased to 9 L/min with same 560 rpm, the achieved value of Mg and TC were 0.3 mol/litre and 0.12 mol/L with shorter residence time of 30 min. It is concluded that feed rate of CO2 is dominant in precipitation experiments and it has a key role in dissociation and reaction of magnesium hydroxide in precipitation of magnesium carbonate.

Practical applications of a systematic approach to the chemical abatement of pollutants in water and air

The present dissertation is devoted to the systematic approach to the development of organic toxic and refractory pollutants abatement by chemical decomposition methods in aqueous and gaseous phases. The systematic approach outlines the basic scenario of chemical decomposition process applications with a step-by-step approximation to the most effective result with a predictable outcome for the full-scale application, confirmed by successful experience. The strategy includes the following steps: chemistry studies, reaction kinetic studies in interaction with the mass transfer processes under conditions of different control parameters, contact equipment design and studies, mathematical description of the process for its modelling and simulation, processes integration into treatment technology and its optimisation, and the treatment plant design. The main idea of the systematic approach for oxidation process introduction consists of a search for the most effective combination between the chemical reaction and the treatment device, in which the reaction is supposed to take place. Under this strategy,a knowledge of the reaction pathways, its products, stoichiometry and kinetics is fundamental and, unfortunately, often unavailable from the preliminary knowledge. Therefore, research made in chemistry on novel treatment methods, comprisesnowadays a substantial part of the efforts. Chemical decomposition methods in the aqueous phase include oxidation by ozonation, ozone-associated methods (O3/H2O2, O3/UV, O3/TiO2), Fenton reagent (H2O2/Fe2+/3+) and photocatalytic oxidation (PCO). In the gaseous phase, PCO and catalytic hydrolysis over zero valent ironsare developed. The experimental studies within the described methodology involve aqueous phase oxidation of natural organic matter (NOM) of potable water, phenolic and aromatic amino compounds, ethylene glycol and its derivatives as de-icing agents, and oxygenated motor fuel additives ¿ methyl tert-butyl ether (MTBE) ¿ in leachates and polluted groundwater. Gas-phase chemical decomposition includes PCO of volatile organic compounds and dechlorination of chlorinated methane derivatives. The results of the research summarised here are presented in fifteenattachments (publications and papers submitted for publication and under preparation).

Catalytic Wet Oxidation of Paper Mill Debarking Water

The objective of the research was to study the influence of temperature, oxygen pressure, catalysts loading and initial COD concentration of debarking wastewater on the pollutants during the catalytic oxidation. More importantly, how the addition of catalyst affects the wet oxidation process. The whole work was divided into two main sections, theoretical and experimental parts. The theoretical part reviews the pulp and paper industry from wood processing to paper production as well as operations that generate wastes. Treatment methods applicable for industrial pulp and paper mill effluents were also discussed. Wet oxidation and catalytic wet oxidation processes including mechanism, reactions, kinetics and industrial applications were previewed. In the experimental part, catalytic wet oxidation process were studied at 120-180°C, 0-10 bar oxygen pressure, 0-1 g/L catalyst concentration and 1000-3000 mg/L initial COD concentration. Responses, such as Chemical oxygen demand (COD), Total organic carbon (TOC), colour, lignin/tannin, Biochemical oxygen demand (BOD) and pH were measured. In the experiment, the best conditions occurred at 180°C, 10 bar, l g/L catalyst concentration and 3000mg/L initial COD. At these conditions; 74% COD, 97% lignin/tannin, 54% TOC, 90% colour were removed from the wastewater. pH was greatly reduced from 7 to 4.6. Lignin/tannin was removed most. Lignin/tannin showed linear dependency with colour during oxidation. Temperature made the most impact in reducing contaminants in debarked wastewater.

Photoinhibition of Photosystem II. Kinetics, Photoprotection and Mechanism

Photosystem II (PSII) is susceptible to light-induced damage defined as photoinhibition. In natural conditions, plants are capable of repairing the photoinhibited PSII by on-going degradation and re-synthesis of the D1 reaction centre protein of PSII. Photoinhibition is induced by both visible and ultraviolet light and photoinhibition occurs under all light intensities with the same efficiency per photon. In my thesis work, I studied the reaction kinetics and mechanism of photoinhibition of PSII, as well as photoprotection in leaves of higher plants. Action spectroscopy was used to identify photoreceptors of photoinhibition. I found that the action spectrum of photoinhibition in vivo shows resemblance to the absorption spectra of manganese model compounds of the oxygen evolving complex (OEC) suggesting a role for manganese as a photoreceptor of photoinhibition under UV and visible light. In order to study the protective effect of non-photochemical quenching, the action spectrum was measured from leaves of wild type Arabidopsis thaliana and two mutants impaired in nonphotochemical quenching of chlorophyll a excitations. The findings of action spectroscopy and simulations of chlorophyll-based photoinhibition mechanisms suggested that quenching of antenna excitations protects less efficiently than would be expected if antenna chlorophylls were the only photoreceptors of photoinhibition. The reaction kinetics of prolonged photoinhibition was studied in leaves of Cucurbita maxima and Capsicum annuum. The results indicated that photoinhibitory decrease in both the oxygen evolution activity and ratio of variable to maximum fluorescence follows firstorder kinetics in vivo. The persistence of first-order kinetics suggests that already photoinhibited reaction centres do not protect against photoinhibition and that the mechanism of photoinhibition does not have a reversible intermediate. When Cucurbita maxima leaves were photoinhibited with saturating single-turnover flashes and continuous light, the light response curve of photoinhibition was found to be essentially a straight line with both types of illumination, suggesting that similar photoinhibition mechanisms might function during illumination with continuous light and during illumination with short flashes.

Development of an environmentally friendly method of starch oxidation by hydrogen peroxide and a complex water-soluble Iron catalyst

Oxidized starch is a key component in the paper industry, where it is used as both surfacing sizer and filler. Large quantities are annually used for this purpose; however, the methods for the oxidation are not environmentally friendly. In our research, we have studied the possibility to replace the harmful oxidation agents, such as hypochlorite or iodates and transition metal catalysts, with a more environmentally friendly oxidant, hydrogen peroxide (H2O2), and a special metal complex catalyst (FePcS), of which only a small amount is needed. The work comprised batch and semi-batch studies by H2O2, ultrasound studies of starch particles, determination of low-molecular by-products and determination of the decomposition kinetics of H2O2 in the presence of starch and the catalyst. This resulted in a waste-free oxidation method, which only produces water and oxygen as side products. The starch oxidation was studied in both semi-batch and batch modes in respective to the oxidant (H2O2) addition. The semi-batch mode proved to yield a sufficient degree of substitution (COOH groups) for industrial purposes. Treatment of starch granules by ultrasound was found to improve the reactivity of starch. The kinetic results were found out to have a rather complex pattern – several oxidation phases were observed, apparently due to the fact that the oxidation reaction in the beginning only took place on the surface, whereas after a prolonged reaction time, partial degradation of the solid starch granules allowed further reaction in the interior parts. Batch-mode experiments enabled a more detailed study of the mechanisms of starch in the presence of H2O2 and the catalyst, but yielded less oxidized starch due to rapid decomposition of H2O2 due to its high concentrations. The effect of the solid-liquid (S/L) ratio in the reaction system was studied in batch experiments. These studies revealed that the presence of the catalyst and the starch enhance the H2O2 decomposition.

Modified nano- and microcellulose based adsorption materials in water treatment

In recent decades, industrial activity growth and increasing water usage worldwide have led to the release of various pollutants, such as toxic heavy metals and nutrients, into the aquatic environment. Modified nanocellulose and microcellulose-based adsorption materials have the potential to remove these contaminants from aqueous solutions. The present research consisted of the preparation of five different nano/microcellulose-based adsorbents, their characterization, the study of adsorption kinetics and isotherms, the determination of adsorption mechanisms, and an evaluation of adsorbents’ regeneration properties. The same well known reactions and modification methods that were used for modifying conventional cellulose also worked for microfibrillated cellulose (MFC). The use of succinic anhydride modified mercerized nanocellulose, and aminosilane and hydroxyapatite modified nanostructured MFC for the removal of heavy metals from aqueous solutions exhibited promising results. Aminosilane, epoxy and hydroxyapatite modified MFC could be used as a promising alternative for H2S removal from aqueous solutions. In addition, new knowledge about the adsorption properties of carbonated hydroxyapatite modified MFC as multifunctional adsorbent for the removal of both cations and anions ions from water was obtained. The maghemite nanoparticles (Fe3O4) modified MFC was found to be a highly promising adsorbent for the removal of As(V) from aqueous solutions due to its magnetic properties, high surface area, and high adsorption capacity . The maximum removal efficiencies of each adsorbent were studied in batch mode. The results of adsorption kinetics indicated very fast removal rates for all the studied pollutants. Modeling of adsorption isotherms and adsorption kinetics using various theoretical models provided information about the adsorbent’s surface properties and the adsorption mechanisms. This knowledge is important for instance, in designing water treatment units/plants. Furthermore, the correspondence between the theory behind the model and properties of the adsorbent as well as adsorption mechanisms were also discussed. On the whole, both the experimental results and theoretical considerations supported the potential applicability of the studied nano/microcellulose-based adsorbents in water treatment applications.

Intensification of hemicellulose hot-water extraction from spruce wood by parameter tuning

The growing population on earth along with diminishing fossil deposits and the climate change debate calls out for a better utilization of renewable, bio-based materials. In a biorefinery perspective, the renewable biomass is converted into many different products such as fuels, chemicals, and materials, quite similar to the petroleum refinery industry. Since forests cover about one third of the land surface on earth, ligno-cellulosic biomass is the most abundant renewable resource available. The natural first step in a biorefinery is separation and isolation of the different compounds the biomass is comprised of. The major components in wood are cellulose, hemicellulose, and lignin, all of which can be made into various end-products. Today, focus normally lies on utilizing only one component, e.g., the cellulose in the Kraft pulping process. It would be highly desirable to utilize all the different compounds, both from an economical and environmental point of view. The separation process should therefore be optimized. Hemicelluloses can partly be extracted with hot-water prior to pulping. Depending in the severity of the extraction, the hemicelluloses are degraded to various degrees. In order to be able to choose from a variety of different end-products, the hemicelluloses should be as intact as possible after the extraction. The main focus of this work has been on preserving the hemicellulose molar mass throughout the extraction at a high yield by actively controlling the extraction pH at the high temperatures used. Since it has not been possible to measure pH during an extraction due to the high temperatures, the extraction pH has remained a “black box”. Therefore, a high-temperature in-line pH measuring system was developed, validated, and tested for hot-water wood extractions. One crucial step in the measurements is calibration, therefore extensive efforts was put on developing a reliable calibration procedure. Initial extractions with wood showed that the actual extraction pH was ~0.35 pH units higher than previously believed. The measuring system was also equipped with a controller connected to a pump. With this addition it was possible to control the extraction to any desired pH set point. When the pH dropped below the set point, the controller started pumping in alkali and by that the desired set point was maintained very accurately. Analyses of the extracted hemicelluloses showed that less hemicelluloses were extracted at higher pH but with a higher molar-mass. Monomer formation could, at a certain pH level, be completely inhibited. Increasing the temperature, but maintaining a specific pH set point, would speed up the extraction without degrading the molar-mass of the hemicelluloses and thereby intensifying the extraction. The diffusion of the dissolved hemicelluloses from the wood particle is a major part of the extraction process. Therefore, a particle size study ranging from 0.5 mm wood particles to industrial size wood chips was conducted to investigate the internal mass transfer of the hemicelluloses. Unsurprisingly, it showed that hemicelluloses were extracted faster from smaller wood particles than larger although it did not seem to have a substantial effect on the average molar mass of the extracted hemicelluloses. However, smaller particle sizes require more energy to manufacture and thus increases the economic cost. Since bark comprises 10 – 15 % of a tree, it is important to also consider it in a biorefinery concept. Spruce inner and outer bark was hot-water extracted separately to investigate the possibility to isolate the bark hemicelluloses. It was showed that the bark hemicelluloses comprised mostly of pectic material and differed considerably from the wood hemicelluloses. The bark hemicelluloses, or pectins, could be extracted at lower temperatures than the wood hemicelluloses. A chemical characterization, done separately on inner and outer bark, showed that inner bark contained over 10 % stilbene glucosides that could be extracted already at 100 °C with aqueous acetone.