Recovery of organic acids with liquid-liquid extraction contactors

Liquid-liquid extraction is a mass transfer process for recovering the desired components from the liquid streams by contacting it to non-soluble liquid solvent. Literature part of this thesis deals with theory of the liquid-liquid extraction and the main steps of the extraction process design. The experimental part of this thesis investigates the extraction of organic acids from aqueous solution. The aim was to find the optimal solvent for recovering the organic acids from aqueous solutions. The other objective was to test the selected solvent in pilot scale with packed column and compare the effectiveness of the structured and the random packing, the effect of dispersed phase selection and the effect of packing material wettability properties. Experiments showed that selected solvent works well with dilute organic acid solutions. The random packing proved to be more efficient than the structured packing due to higher hold-up of the dispersed phase. Dispersing the phase that is present in larger volume proved to more efficient. With the random packing the material that was wetted by the dispersed phase was more efficient due to higher hold-up of the dispersed phase. According the literature, the behavior is usually opposite.

Konsentroitujen liuosten nanosuodatus

The aim of this thesis was to study the retentions of an organic acid and neutral components separately and in mixed solutions. The literature part of this study deals with factors affecting retention in nanofiltration. Nanofiltration is a complex process where many factors are affecting retention depending on the solution, molecule and membrane properties and their interactions. Concentrated model solutions were filtered with Desal-5 DL, NTR 7470 and NF 270 nanofiltration membranes in the experimental part of this work. The effects of pH, pressure and flux on retention were studied. Citric acid was used as the organic acid and the neutral components were inositol, betaine and xylitol. All components were filtered separately. The neutral compounds were also filtered together with citric acid. The filtrations were performed at Lappeenranta University of Technology using laboratory scale nanofiltration equipment. The retentions of neutral components were constant when filtered separately at different pH values. Citric acid had a significant influence on the retention of the neutral compounds. The retentions of neutral compounds decreased significantly when pH increased. The neutral compounds did not have any affect on the retention of citric acid. The retentions of model compounds increased when the flux increased.

Hydrometallurgical recovery of valuable metals from secondary raw materials

Wastes and side streams in the mining industry and different anthropogenic wastes often contain valuable metals in such concentrations their recovery may be economically viable. These raw materials are collectively called secondary raw materials. The recovery of metals from these materials is also environmentally favorable, since many of the metals, for example heavy metals, are hazardous to the environment. This has been noticed in legislative bodies, and strict regulations for handling both mining and anthropogenic wastes have been developed, mainly in the last decade. In the mining and metallurgy industry, important secondary raw materials include, for example, steelmaking dusts (recoverable metals e.g. Zn and Mo), zinc plant residues (Ag, Au, Ga, Ge, In) and waste slurry from Bayer process alumina production (Ga, REE, Ti, V). From anthropogenic wastes, waste electrical and electronic equipment (WEEE), among them LCD screens and fluorescent lamps, are clearly the most important from a metals recovery point of view. Metals that are commonly recovered from WEEE include, for example, Ag, Au, Cu, Pd and Pt. In LCD screens indium, and in fluorescent lamps, REEs, are possible target metals. Hydrometallurgical processing routes are highly suitable for the treatment of complex and/or low grade raw materials, as secondary raw materials often are. These solid or liquid raw materials often contain large amounts of base metals, for example. Thus, in order to recover valuable metals, with small concentrations, highly selective separation methods, such as hydrometallurgical routes, are needed. In addition, hydrometallurgical processes are also seen as more environmental friendly, and they have lower energy consumption, when compared to pyrometallurgical processes. In this thesis, solvent extraction and ion exchange are the most important hydrometallurgical separation methods studied. Solvent extraction is a mainstream unit operation in the metallurgical industry for all kinds of metals, but for ion exchange, practical applications are not as widespread. However, ion exchange is known to be particularly suitable for dilute feed solutions and complex separation tasks, which makes it a viable option, especially for processing secondary raw materials. Recovering valuable metals was studied with five different raw materials, which included liquid and solid side streams from metallurgical industries and WEEE. Recovery of high purity (99.7%) In, from LCD screens, was achieved by leaching with H2SO4, extracting In and Sn to D2EHPA, and selectively stripping In to HCl. In was also concentrated in the solvent extraction stage from 44 mg/L to 6.5 g/L. Ge was recovered as a side product from two different base metal process liquors with Nmethylglucamine functional chelating ion exchange resin (IRA-743). Based on equilibrium and dynamic modeling, a mechanism for this moderately complex adsorption process was suggested. Eu and Y were leached with high yields (91 and 83%) by 2 M H2SO4 from a fluorescent lamp precipitate of waste treatment plant. The waste also contained significant amounts of other REEs such as Gd and Tb, but these were not leached with common mineral acids in ambient conditions. Zn was selectively leached over Fe from steelmaking dusts with a controlled acidic leaching method, in which the pH did not go below, but was held close as possible to, 3. Mo was also present in the other studied dust, and was leached with pure water more effectively than with the acidic methods. Good yield and selectivity in the solvent extraction of Zn was achieved by D2EHPA. However, Fe needs to be eliminated in advance, either by the controlled leaching method or, for example, by precipitation. 100% Pure Mo/Cr product was achieved with quaternary ammonium salt (Aliquat 336) directly from the water leachate, without pH adjustment (pH 13.7). A Mo/Cr mixture was also obtained from H2SO4 leachates with hydroxyoxime LIX 84-I and trioctylamine (TOA), but the purities were 70% at most. However with Aliquat 336, again an over 99% pure mixture was obtained. High selectivity for Mo over Cr was not achieved with any of the studied reagents. Ag-NaCl solution was purified from divalent impurity metals by aminomethylphosphonium functional Lewatit TP-260 ion exchange resin. A novel preconditioning method, named controlled partial neutralization, with conjugate bases of weak organic acids, was used to control the pH in the column to avoid capacity losses or precipitations. Counter-current SMB was shown to be a better process configuration than either batch column operation or the cross-current operation conventionally used in the metallurgical industry. The raw materials used in this thesis were also evaluated from an economic point of view, and the precipitate from a waste fluorescent lamp treatment process was clearly shown to be the most promising.

Methyl and ethyl chloride synthesis in microreactors

Methyl chloride is an important chemical intermediate with a variety of applications. It is produced today in large units and shipped to the endusers. Most of the derived products are harmless, as silicones, butyl rubber and methyl cellulose. However, methyl chloride is highly toxic and flammable. On-site production in the required quantities is desirable to reduce the risks involved in transportation and storage. Ethyl chloride is a smaller-scale chemical intermediate that is mainly used in the production of cellulose derivatives. Thus, the combination of onsite production of methyl and ethyl chloride is attractive for the cellulose processing industry, e.g. current and future biorefineries. Both alkyl chlorides can be produced by hydrochlorination of the corresponding alcohol, ethanol or methanol. Microreactors are attractive for the on-site production as the reactions are very fast and involve toxic chemicals. In microreactors, the diffusion limitations can be suppressed and the process safety can be improved. The modular setup of microreactors is flexible to adjust the production capacity as needed. Although methyl and ethyl chloride are important chemical intermediates, the literature available on potential catalysts and reaction kinetics is limited. Thus the thesis includes an extensive catalyst screening and characterization, along with kinetic studies and engineering the hydrochlorination process in microreactors. A range of zeolite and alumina based catalysts, neat and impregnated with ZnCl2, were screened for the methanol hydrochlorination. The influence of zinc loading, support, zinc precursor and pH was investigated. The catalysts were characterized with FTIR, TEM, XPS, nitrogen physisorption, XRD and EDX to identify the relationship between the catalyst characteristics and the activity and selectivity in the methyl chloride synthesis. The acidic properties of the catalyst were strongly influenced upon the ZnCl2 modification. In both cases, alumina and zeolite supports, zinc reacted to a certain amount with specific surface sites, which resulted in a decrease of strong and medium Brønsted and Lewis acid sites and the formation of zinc-based weak Lewis acid sites. The latter are highly active and selective in methanol hydrochlorination. Along with the molecular zinc sites, bulk zinc species are present on the support material. Zinc modified zeolite catalysts exhibited the highest activity also at low temperatures (ca 200 °C), however, showing deactivation with time-onstream. Zn/H-ZSM-5 zeolite catalysts had a higher stability than ZnCl2 modified H-Beta and they could be regenerated by burning the coke in air at 400 °C. Neat alumina and zinc modified alumina catalysts were active and selective at 300 °C and higher temperatures. However, zeolite catalysts can be suitable for methyl chloride synthesis at lower temperatures, i.e. 200 °C. Neat γ-alumina was found to be the most stable catalyst when coated in a microreactor channel and it was thus used as the catalyst for systematic kinetic studies in the microreactor. A binder-free and reproducible catalyst coating technique was developed. The uniformity, thickness and stability of the coatings were extensively characterized by SEM, confocal microscopy and EDX analysis. A stable coating could be obtained by thermally pretreating the microreactor platelets and ball milling the alumina to obtain a small particle size. Slurry aging and slow drying improved the coating uniformity. Methyl chloride synthesis from methanol and hydrochloric acid was performed in an alumina-coated microreactor. Conversions from 4% to 83% were achieved in the investigated temperature range of 280-340 °C. This demonstrated that the reaction is fast enough to be successfully performed in a microreactor system. The performance of the microreactor was compared with a tubular fixed bed reactor. The results obtained with both reactors were comparable, but the microreactor allows a rapid catalytic screening with low consumption of chemicals. As a complete conversion of methanol could not be reached in a single microreactor, a second microreactor was coupled in series. A maximum conversion of 97.6 % and a selectivity of 98.8 % were reached at 340°C, which is close to the calculated values at a thermodynamic equilibrium. A kinetic model based on kinetic experiments and thermodynamic calculations was developed. The model was based on a Langmuir Hinshelwood-type mechanism and a plug flow model for the microreactor. The influence of the reactant adsorption on the catalyst surface was investigated by performing transient experiments and comparing different kinetic models. The obtained activation energy for methyl chloride was ca. two fold higher than the previously published, indicating diffusion limitations in the previous studies. A detailed modeling of the diffusion in the porous catalyst layer revealed that severe diffusion limitations occur starting from catalyst coating thicknesses of 50 μm. At a catalyst coating thickness of ca 15 μm as in the microreactor, the conditions of intrinsic kinetics prevail. Ethanol hydrochlorination was performed successfully in the microreactor system. The reaction temperature was 240-340°C. An almost complete conversion of ethanol was achieved at 340°C. The product distribution was broader than for methanol hydrochlorination. Ethylene, diethyl ether and acetaldehyde were detected as by-products, ethylene being the most dominant by-product. A kinetic model including a thorough thermodynamic analysis was developed and the influence of adsorbed HCl on the reaction rate of ethanol dehydration reactions was demonstrated. The separation of methyl chloride using condensers was investigated. The proposed microreactor-condenser concept enables the production of methyl chloride with a high purity of 99%.

Ravinnepitoisen teollisen jäteveden tuotteistaminen

Tässä työssä selvitettiin ravinnepitoisen jäteveden väkevöintiä erityisesti ammoniumtypen ja orgaanisten happojen osalta. Konsentrointiin käytettiin pääasiassa käänteisosmoosia sekä haihdutusta, mutta myös nanosuodatusta tutkittiin. Jätevesi oli Honkajoki Oy:n lauhdevettä. Kirjallisuusosassa esiteltiin Honkajoki Oy:n toimintaa, membraanierotus-prosesseja, lihantuotannossa syntyvän jätteen ominaisuuksia sekä sen puhdistamista. Keskeisimmät suodatukset tehtiin DOW FILMTEC SW30HR -membraanilla, ja käytetty laitteisto oli DSS LabStak M20. Suodatuksia tehtiin eri pH-olosuhteissa typen ja orgaanisten happojen erottumisen kannalta optimaalisten olosuhteiden löytämiseksi. Lisäksi tutkittiin, kuinka puhtaaksi permeaatti voidaan saada uudelleensuodatuksen avulla. Työssä käytettiin myös haihdutusta lauhteen väkevöintiin. Ammoniumtypen konsentroituminen suodatuksissa oli tehokkainta pH:n ollessa 7 tai sen alle. Kaksivaiheisella suodatuksella permeaatin laatu alitti selvästi Karvianjokeen laskettaville jätevesille asetetut laatu- ja kuormitusrajat. Yhdistämällä suodatus- ja haihdutusprosessit, pystyttiin valmistamaan liuosta, jonka ammoniumtyppipitoisuus oli noin 7,6 %. Tuolloin suodatus tehtiin pH 7:ssä ja haihdutus pH 3:ssa rotavaporilla 26 mbar paineessa ja 50 °C lämpötilassa. Syöttöliuoksen tilavuuden alenema oli noin 65-kertainen. Haihdutuksessa muodostuneessa lauhteessa oli paljon orgaanisia happoja ja käytännössä ei lainkaan ammoniumtyppeä. Tuotejakeita saatiin siten kaksi kappaletta: ammoniumtyppijae ja orgaanisia happoja sisältävä jae.

Development and characterization of thin printed films for gas sensing applications

The monitoring and control of hydrogen sulfide (H2S) level is of great interest for a wide range of application areas including food quality control, defense and antiterrorist applications and air quality monitoring e.g. in mines. H2S is a very poisonous and flammable gas. Exposure to low concentrations of H2S can result in eye irritation, a sore throat and cough, shortness of breath, and fluid retention in the lungs. These symptoms usually disappear in a few weeks. Long-term, low-level exposure may result in fatigue, loss of appetite, headache, irritability, poor memory, and dizziness. Higher concentrations of 700 - 800 ppm tend to be fatal. H2S has a characteristic smell of rotten egg. However, because of temporary paralysis of olfactory nerves, the smelling capability at concentrations higher than 100 ppm is severely compromised. In addition, volatile H2S is one of the main products during the spoilage of poultry meat in anaerobic conditions. Currently, no commercial H2S sensor is available which can operate under anaerobic conditions and can be easily integrated in the food packaging. This thesis presents a step-wise progress in the development of printed H2S gas sensors. Efforts were made in the formulation, characterization and optimization of functional printable inks and coating pastes based on composites of a polymer and a metal salt as well as a composite of a metal salt and an organic acid. Different processing techniques including inkjet printing, flexographic printing, screen printing and spray coating were utilized in the fabrication of H2S sensors. The dispersions were characterized by measuring turbidity, surface tension, viscosity and particle size. The sensing films were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy and an electrical multimeter. Thin and thick printed or coated films were developed for gas sensing applications with the aim of monitoring the H2S concentrations in real life applications. Initially, a H2S gas sensor based on a composite of polyaniline and metal salt was developed. Both aqueous and solvent-based dispersions were developed and characterized. These dispersions were then utilized in the fabrication of roll-to-roll printed H2S gas sensors. However, the humidity background, long term instability and comparatively lower detection limit made these sensors less favourable for real practical applications. To overcome these problems, copper acetate based sensors were developed for H2S gas sensing. Stable inks with excellent printability were developed by tuning the surface tension, viscosity and particle size. This enabled the formation of inkjet-printed high quality copper acetate films with excellent sensitivity towards H2S. Furthermore, these sensors showed negligible humidity effects and improved selectivity, response time, lower limit of detection and coefficient of variation. The lower limit of detection of copper acetate based sensors was further improved to sub-ppm level by incorporation of catalytic gold nano-particles and subsequent plasma treatment of the sensing film. These sensors were further integrated in an inexpensive wirelessly readable RLC-circuit (where R is resistor, L is inductor and C is capacitor). The performance of these sensors towards biogenic H2S produced during the spoilage of poultry meat in the modified atmosphere package was also demonstrated in this thesis. This serves as a proof of concept that these sensors can be utilized in real life applications.

Stabilization of the ionic form of weak acid cation exchange resins

Weak acid cation exchange (WAC) resins are used in the chromatographic separation of betaine from vinasse, a by-product of sugar industry. The ionic form of the resin determines the elution time of betaine. When a WAC-resin is in hydrogen form, the retention time of betaine is the longest and betaine elutes as the last component of vi-nasse from the chromatographic column. If the feed solution contains salts and its pH is not acidic enough to keep the resin undissociated, the ionic form of the hydrogen form resin starts to alter. Vinasse contains salts and its pH is around 5, it also contains weak acids. To keep the metal ion content (Na/H ratio) of the resin low enough to ensure successful separation of betaine, acid has to be added to either eluent (water) or vinasse. The aim of the present work was to examine by laboratory experiments which option requires less acid. Also the retention mechanism of betaine was investigated by measuring retention volumes of acetic acid and choline in different Na/H ratios of the resin. It was found that the resulting ionic form of the resin is the same regardless of whether the regeneration acid is added to the eluent or the feed solution (vinasse). Be-sides the salt concentration and the pH of vinasse, also the concentration of weak acids in the feed affects the resulting ionic form of the resin. The more buffering capacity vinasse has, the more acid is required to keep the ionic form of the resin desired. Vinasse was found to be quite strong buffer solution, which means relatively high amounts of acid are required to prevent the Na/H ratio from increasing too much. It is known that the retention volume of betaine decreases significantly, when the Na/H ratio increases. This is assumed to occur, because the amount of hydrogen bonds between the carboxylic groups of betaine and the resin decreases. Same behavior was not found with acetic acid. Choline has the same molecular structure as betaine, but instead of carboxylic group it has hydroxide group. The retention volume of choline increased as the Na/H ratio of the resin increased, because of the ion exchange reaction between choline cation and dissociated carboxylic group of the resin. Since the retention behavior of choline on the resin is opposite to the behavior of be-taine, the strong affinity of betaine towards hydrogen form WAC-resin has to be based on its carboxylic group. It is probable that the quaternary ammonium groups also affect the behavior of the carboxylic groups of betaine, causing them to form hydrogen bonds with the carboxylic groups of the resin.

Potentiometric titration as a method of determining the stoichiometric dissociation constants of weak acids from the thermodynamic dissociation constants of aqueous solutions at 298.15 K

The simple single-ion activity coefficient equation originating from the Debye-Hückel theory was used to determine the thermodynamic and stoichiometric dissociation constants of weak acids from data concerning galvanic cells. Electromotive force data from galvanic cells without liquid junctions, which was obtained from literature, was studied in conjuction with the potentiometric titration data relating to aqueous solutions at 298.15 K. The dissociation constants of weak acids could be determined by the presented techniques and almost all the experimental data studied could be interpreted within the range of experimental error. Potentiometric titration has been used here and the calculation methods were developed to obtain the thermodynamic and stoichiometric dissociation constants of some weak acids in aqueous solutions at 298.15 K. The ionic strength of titrated solutions were adjusted using an inert electrolyte, namely, sodium or potassium chloride. Salt content alonedetermines the ionic strength. The ionic strength of the solutions studied varied from 0.059 mol kg-1 to 0.37 mol kg-1, and in some cases up to 1.0 mol kg-1. The following substances were investigated using potentiometric titration: aceticacid, propionic acid, L-aspartic acid, L-glutamic acid and bis(2,2-dimethyl-3-oxopropanol) amine.

Ammoniakin talteenottoprosessin kehitys

Diplomityössä kehitettiin ioninvaihtoon perustuva ammoniakin talteenottoprosessi NSSC (Neutral Sulphite Semi Chemical) -prosessin haihduttamon lauhteille. Tarkoituksena oli saada aallotuskartonkitehtaan kemi-kaalikiertoa suljettua ja sitä kautta ammoniakkipäästöjä vähennettyä. Ammoniakki tuli ottaa hyötymuodossa (ammoniakkihöyry tai ammoniumsulfiitti) talteen. Ammoniumsulfiittiliuosta käytetään NSSC-prosessissa keittonesteenä. Kirjallisuusosassa selvitetään strippaukseen perustuvia ammoniakin talteenottomahdollisuuksia. Tutkitaan ioninvaihdon teoriaa ja ammoniumin talteenottoon sopivien ioninvaihtomateriaalien ominaisuuksia ioninvaihtajina. Lisäksi esitetään ioninvaihtoprosesseihin liittyviä laitteistoratkaisuja ja prosessiolosuhteita. Työn kokeellisessa osassa on yleiskuvaus Powerflute Oy Savon Sellun prosesseista ja selvitetään ammoniakin merkitystä tehtaalle. Laboratoriokokein tutkittiin orgaanisten kationihartsien sekä epäorgaanisen luonnon zeoliitin soveltuvuutta ammoniumionien vaihtoon esihaihduttamon lauhteesta. Ammoniakin talteenottoprosessin toimivuutta teollisessa mittakaavassa selvitettiin rakennetulla pilotlaitteistolla suoritettujen kokeiden avulla. Lopuksi tehtiin ammoniakin talteenottoprosessin scale-up: laskettiin prosessin talteenottokapasiteetti, arvioitiin kustannuksia sekä annettiin lausunto prosessin toteutettavuudesta. Laboratoriokokeiden perusteella luonnon zeoliitti ja heikosti hapan ioninvaihtohartsi eivät sovellu ammoniumionien vaihtoon NSSC haihduttamon lauhteista. Vahvasti hapan kationihartsi toimi ammoniumin talteenotossa parhaiten, joten se valittiin pilotkokeiden ioninvaihtomateriaaliksi. Pilotkokeissa ioninvaihtomateriaaliin saatiin sidottua ammoniumia noin 30 g NH4+ / dm3 hartsia, kun materiaalin teoreettinen ioninvaihtokapasiteetti oli 32 g NH4+ / dm3 hartsia. Ammoniumin läpäisykäyrien muotoon vaikutti suuresti syöttölauhteen virtausnopeus ja ammoniumpitoisuus. Ioninvaihtomateriaalipedin syvyydellä ei ollut niinkään merkitystä. Pilotkokeiden regenerointitavoista tehokkaimmaksi osoittautui höyrystrippaus, jossa saavutettiin noin 90 %:n talteenottotehokkuus. Rikkihapokekäsittelyllä talteenottotehokkuus jäi 50 %:iin. Teollisen mittakaavan laitoksella voidaan vuosittain regenerointitavasta riippuen ottaa talteen esihaihdut-tamon lauhteesta noin 100-150 tonnia ammoniakkia. Prosessin käyttökustannukset ovat talteenotetusta ammoniakista saataviin säästöihin verrattuna suuret ja niihin vaikuttaa merkittävästi ioninvaihtohartsin käyttöikä sekä regenerointikemikaalien kulutus. Osittaisella kemikaalikierron sulkemisella saavutetaan NSSC-prosessissa sekundäärietuja, joiden vaikutuksen merkittävyys pitäisi tarkentaa lisätutkimuksilla.

Gas-phase photocatalytic oxidation of volatile organic compounds

Substances emitted into the atmosphere by human activities in urban and industrial areas cause environmental problems such as air quality degradation, respiratory diseases, climate change, global warming, and stratospheric ozone depletion. Volatile organic compounds (VOCs) are major air pollutants, emitted largely by industry, transportation and households. Many VOCs are toxic, and some are considered to be carcinogenic, mutagenic, or teratogenic. A wide spectrum of VOCs is readily oxidized photocatalytically. Photocatalytic oxidation (PCO) over titanium dioxide may present a potential alternative to air treatment strategies currently in use, such as adsorption and thermal treatment, due to its advantageous activity under ambient conditions, although higher but still mild temperatures may also be applied. The objective of the present research was to disclose routes of chemical reactions, estimate the kinetics and the sensitivity of gas-phase PCO to reaction conditions in respect of air pollutants containing heteroatoms in their molecules. Deactivation of the photocatalyst and restoration of its activity was also taken under consideration to assess the practical possibility of the application of PCO to the treatment of air polluted with VOCs. UV-irradiated titanium dioxide was selected as a photocatalyst for its chemical inertness, non-toxic character and low cost. In the present work Degussa P25 TiO2 photocatalyst was mostly used. In transient studies platinized TiO2 was also studied. The experimental research into PCO of following VOCs was undertaken: - methyl tert-butyl ether (MTBE) as the basic oxygenated motor fuel additive and, thus, a major non-biodegradable pollutant of groundwater; - tert-butyl alcohol (TBA) as the primary product of MTBE hydrolysis and PCO; - ethyl mercaptan (ethanethiol) as one of the reduced sulphur pungent air pollutants in the pulp-and-paper industry; - methylamine (MA) and dimethylamine (DMA) as the amino compounds often emitted by various industries. The PCO of VOCs was studied using a continuous-flow mode. The PCO of MTBE and TBA was also studied by transient mode, in which carbon dioxide, water, and acetone were identified as the main gas-phase products. The volatile products of thermal catalytic oxidation (TCO) of MTBE included 2-methyl-1-propene (2-MP), carbon monoxide, carbon dioxide and water; TBA decomposed to 2-MP and water. Continuous PCO of 4 TBA proceeded faster in humid air than dry air. MTBE oxidation, however, was less sensitive to humidity. The TiO2 catalyst was stable during continuous PCO of MTBE and TBA above 373 K, but gradually lost activity below 373 K; the catalyst could be regenerated by UV irradiation in the absence of gas-phase VOCs. Sulphur dioxide, carbon monoxide, carbon dioxide and water were identified as ultimate products of PCO of ethanethiol. Acetic acid was identified as a photocatalytic oxidation by-product. The limits of ethanethiol concentration and temperature, at which the reactor performance was stable for indefinite time, were established. The apparent reaction kinetics appeared to be independent of the reaction temperature within the studied limits, 373 to 453 K. The catalyst was completely and irreversibly deactivated with ethanethiol TCO. Volatile PCO products of MA included ammonia, nitrogen dioxide, nitrous oxide, carbon dioxide and water. Formamide was observed among DMA PCO products together with others similar to the ones of MA. TCO for both substances resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide and water. No deactivation of the photocatalyst during the multiple long-run experiments was observed at the concentrations and temperatures used in the study. PCO of MA was also studied in the aqueous phase. Maximum efficiency was achieved in an alkaline media, where MA exhibited high fugitivity. Two mechanisms of aqueous PCO – decomposition to formate and ammonia, and oxidation of organic nitrogen directly to nitrite - lead ultimately to carbon dioxide, water, ammonia and nitrate: formate and nitrite were observed as intermediates. A part of the ammonia formed in the reaction was oxidized to nitrite and nitrate. This finding helped in better understanding of the gasphase PCO pathways. The PCO kinetic data for VOCs fitted well to the monomolecular Langmuir- Hinshelwood (L-H) model, whereas TCO kinetic behaviour matched the first order process for volatile amines and the L-H model for others. It should be noted that both LH and the first order equations were only the data fit, not the real description of the reaction kinetics. The dependence of the kinetic constants on temperature was established in the form of an Arrhenius equation.

Kinetic modeling of mechanisms of industrially important organic reactions in gas and liquid phase

This dissertation is based on 5 articles which deal with reaction mechanisms of the following selected industrially important organic reactions: 1. dehydrocyclization of n-butylbenzene to produce naphthalene 2. dehydrocyclization of 1-(p-tolyl)-2-methylbutane (MB) to produce 2,6-dimethylnaphthalene 3. esterification of neopentyl glycol (NPG) with different carboxylic acids to produce monoesters 4. skeletal isomerization of 1-pentene to produce 2-methyl-1-butene and 2-methyl-2-butene The results of initial- and integral-rate experiments of n-butylbenzene dehydrocyclization over selfmade chromia/alumina catalyst were applied when investigating reaction 2. Reaction 2 was performed using commercial chromia/alumina of different acidity, platina on silica and vanadium/calcium/alumina as catalysts. On all catalysts used for the dehydrocyclization, major reactions were fragmentation of MB and 1-(p-tolyl)-2-methylbutenes (MBes), dehydrogenation of MB, double bond transfer, hydrogenation and 1,6-cyclization of MBes. Minor reactions were 1,5-cyclization of MBes and methyl group fragmentation of 1,6- cyclization products. Esterification reactions of NPG were performed using three different carboxylic acids: propionic, isobutyric and 2-ethylhexanoic acid. Commercial heterogeneous gellular (Dowex 50WX2), macroreticular (Amberlyst 15) type resins and homogeneous para-toluene sulfonic acid were used as catalysts. At first NPG reacted with carboxylic acids to form corresponding monoester and water. Then monoester esterified with carboxylic acid to form corresponding diester. In disproportionation reaction two monoester molecules formed NPG and corresponding diester. All these three reactions can attain equilibrium. Concerning esterification, water was removed from the reactor in order to prevent backward reaction. Skeletal isomerization experiments of 1-pentene were performed over HZSM-22 catalyst. Isomerization reactions of three different kind were detected: double bond, cis-trans and skeletal isomerization. Minor side reaction were dimerization and fragmentation. Monomolecular and bimolecular reaction mechanisms for skeletal isomerization explained experimental results almost equally well. Pseudohomogeneous kinetic parameters of reactions 1 and 2 were estimated by usual least squares fitting. Concerning reactions 3 and 4 kinetic parameters were estimated by the leastsquares method, but also the possible cross-correlation and identifiability of parameters were determined using Markov chain Monte Carlo (MCMC) method. Finally using MCMC method, the estimation of model parameters and predictions were performed according to the Bayesian paradigm. According to the fitting results suggested reaction mechanisms explained experimental results rather well. When the possible cross-correlation and identifiability of parameters (Reactions 3 and 4) were determined using MCMC method, the parameters identified well, and no pathological cross-correlation could be seen between any parameter pair.

Adsorptive removal of harmful organic compound from aqueous solutions

Adsorption is one of the most commonly used methods in water treatment processes. It is attractive due to it easy operation and the availability of a wide variety of commercial adsorbents. This doctoral thesis focuses on investigating and explaining the influence of external phase conditions (temperature, pH, ionic strength, acidity, presence of cosolutes) on adsorption phenomena. In order to cover a wide range of factors and phenomena, case studies were chosen from various fields where adsorption is applied. These include the adsorptive removal of surface active agents (used in cleaning chemicals, for example) from aqueous effluents, the removal of hormones (estradiol) from drinking water, and the adsorption of antibiotics onto silica. The latter can beused to predict the diffusion of antibiotics in the aquatic system if they are released into the environment. Also the adsorption of living cells on functionalized polymers to purify infected water streams was studied. In addition to these examples, the adsorptive separation of harmful compounds from internal water streams within a chemical process was investigated. The model system was removal of fermentation inhibitors from lignocelluloses hydrolyzates. The detoxification of the fermentation broth is an important step in the manufacture of bioethanol from wood, but has not been studied previously in connection with concentrated acid hydrolyzates. New knowledge on adsorption phenomena was generated for all of the applications investigated. In most cases, the results could be explained by combining classical theories for individual phenomena. As an example, it was demonstrated how liquid phase aggregation could explain abnormal-looking adsorption equilibrium data. In addition to the fundamental phenomena, also process performance was of interest. This aspect is often neglected in adsorption studies. It was demonstrated that adsorbents should not be selected for a target application based on their adsorption properties only, but regeneration of the spent adsorbent must be considered. It was found that using a suitable amount of organic co-solvent in the regeneration can significantly improve the productivity of the process.

Determination of sugars and organic acids in pulp samples by capillary electrophoresis with UV detection

This MSc work was done in the project of BIOMECON financed by Tekes. The prime target of the research was, to develop methods for separation and determination of carbohydrates (sugars), sugar acids and alcohols, and some other organic acids in hydrolyzed pulp samples by capillary electrophoresis (CE) using UV detection. Aspen, spruce, and birch pulps are commonly used for production of papers in Finland. Feedstock components in pulp predominantly consist of carbohydrates, organic acids, lignin, extractives, and proteins. Here in this study, pulps have been hydrolyzed in analytical chemistry laboratories of UPM Company and Lappeenranta University in order to convert them into sugars, acids, alcohols, and organic acids. Foremost objective of this study was to quantify and identify the main and by-products in the pulp samples. For the method development and optimization, increased precision in capillary electrophoresis was accomplished by calculating calibration data of 16 analytes such as D-(-)-fructose, D(+)-xylose, D(+)-mannose, D(+)-cellobiose, D-(+)-glucose, D-(+)-raffinose, D(-)-mannitol, sorbitol, rhamnose, sucrose, xylitol, galactose, maltose, arabinose, ribose, and, α-lactose monohydratesugars and 16 organic acids such as D-glucuronic, oxalic, acetic, propionic, formic, glycolic, malonic, maleic, citric, L-glutamic, tartaric, succinic, adipic, ascorbic, galacturonic, and glyoxylic acid. In carbohydrate and polyalcohol analyses, the experiments with CE coupled to direct UV detection and positive separation polarity was performed in 36 mM disodium hydrogen phosphate electrolyte solution. For acid analyses, CE coupled indirect UV detection, using negative polarity, and electrolyte solution made of 2,3 pyridinedicarboxylic acid, Ca2+ salt, Mg2+ salts, and myristyltrimethylammonium hydroxide in water was used. Under optimized conditions, limits of detection, relative standard deviations and correlation coefficients of each compound were measured. The optimized conditions were used for the identification and quantification of carbohydrates and acids produced by hydrolyses of pulp. The concentrations of the analytes varied between 1 mg – 0.138 g in liter hydrolysate.

Studies on chemoenzymatic synthesis: Lipase-catalyzed acylation in multistep organic synthesis

In this thesis, biocatalysis is defined as the science of using enzymes as catalysts in organic synthesis. Environmental aspects and the continuously expanding repertoire of available enzymes have firmly established biocatalysis as a prominent means of chemo-, regio- and stereoselective synthesis. Yet, no single methodology can solve all the challenges faced by a synthetic chemist. Therefore, the knowledge and the skills to combine different synthetic methods are relevant. Lipases are highly useful enzymes in organic synthesis. In this thesis, an effort is being made to form a coherent picture of when and how can lipases be incorporated into nonenzymatic synthesis. This is attempted both in the literature review and in the discussion of the results presented in the original publications contained in the thesis. In addition to lipases, oxynitrilases were also used in the work. The experimental part of the thesis comprises of the results reported in four peer-reviewed publications and one manuscript. Selected amines, amino acids and sugar-derived cyanohydrins or their acylated derivatives were each prepared in enantio- or diastereomerically enriched form. Where applicable, attempts were made to combine the enzymatic reactions to other synthetic steps either by the application of completely separate sequential reactions with isolated intermediates (kinetic and functional kinetic resolution of amines), simultaneously occurring reactions without intermediate isolation (dynamic kinetic resolution of amino acid esters) or sequential reactions but without isolating the intermediates (hydrocyanation of sugar aldehydes with subsequent diastereoresolution). In all cases, lipase-catalyzed acylation was the key step by which stereoselectivity was achieved. Lipase from Burkholderia cepacia was a highly selective enzyme with each substrate category, but careful selection of the acyl donor and the solvent was important as well.

Spatial modeling techniques for mapping and characterization of acid sulfate soils

Acid sulfate (a.s.) soils constitute a major environmental issue. Severe ecological damage results from the considerable amounts of acidity and metals leached by these soils in the recipient watercourses. As even small hot spots may affect large areas of coastal waters, mapping represents a fundamental step in the management and mitigation of a.s. soil environmental risks (i.e. to target strategic areas). Traditional mapping in the field is time-consuming and therefore expensive. Additional more cost-effective techniques have, thus, to be developed in order to narrow down and define in detail the areas of interest. The primary aim of this thesis was to assess different spatial modeling techniques for a.s. soil mapping, and the characterization of soil properties relevant for a.s. soil environmental risk management, using all available data: soil and water samples, as well as datalayers (e.g. geological and geophysical). Different spatial modeling techniques were applied at catchment or regional scale. Two artificial neural networks were assessed on the Sirppujoki River catchment (c. 440 km2) located in southwestern Finland, while fuzzy logic was assessed on several areas along the Finnish coast. Quaternary geology, aerogeophysics and slope data (derived from a digital elevation model) were utilized as evidential datalayers. The methods also required the use of point datasets (i.e. soil profiles corresponding to known a.s. or non-a.s. soil occurrences) for training and/or validation within the modeling processes. Applying these methods, various maps were generated: probability maps for a.s. soil occurrence, as well as predictive maps for different soil properties (sulfur content, organic matter content and critical sulfide depth). The two assessed artificial neural networks (ANNs) demonstrated good classification abilities for a.s. soil probability mapping at catchment scale. Slightly better results were achieved using a Radial Basis Function (RBF) -based ANN than a Radial Basis Functional Link Net (RBFLN) method, narrowing down more accurately the most probable areas for a.s. soil occurrence and defining more properly the least probable areas. The RBF-based ANN also demonstrated promising results for the characterization of different soil properties in the most probable a.s. soil areas at catchment scale. Since a.s. soil areas constitute highly productive lands for agricultural purpose, the combination of a probability map with more specific soil property predictive maps offers a valuable toolset to more precisely target strategic areas for subsequent environmental risk management. Notably, the use of laser scanning (i.e. Light Detection And Ranging, LiDAR) data enabled a more precise definition of a.s. soil probability areas, as well as the soil property modeling classes for sulfur content and the critical sulfide depth. Given suitable training/validation points, ANNs can be trained to yield a more precise modeling of the occurrence of a.s. soils and their properties. By contrast, fuzzy logic represents a simple, fast and objective alternative to carry out preliminary surveys, at catchment or regional scale, in areas offering a limited amount of data. This method enables delimiting and prioritizing the most probable areas for a.s soil occurrence, which can be particularly useful in the field. Being easily transferable from area to area, fuzzy logic modeling can be carried out at regional scale. Mapping at this scale would be extremely time-consuming through manual assessment. The use of spatial modeling techniques enables the creation of valid and comparable maps, which represents an important development within the a.s. soil mapping process. The a.s. soil mapping was also assessed using water chemistry data for 24 different catchments along the Finnish coast (in all, covering c. 21,300 km2) which were mapped with different methods (i.e. conventional mapping, fuzzy logic and an artificial neural network). Two a.s. soil related indicators measured in the river water (sulfate content and sulfate/chloride ratio) were compared to the extent of the most probable areas for a.s. soils in the surveyed catchments. High sulfate contents and sulfate/chloride ratios measured in most of the rivers demonstrated the presence of a.s. soils in the corresponding catchments. The calculated extent of the most probable a.s. soil areas is supported by independent data on water chemistry, suggesting that the a.s. soil probability maps created with different methods are reliable and comparable.