Preparative ion exchange for salt solutions

Työssä tutkittiin moniarvoisten metalliformiaattien valmistusta ioninvaihto-menetelmällä. Kirjallisuustutkimus käsitteleetunnettuja alumiiniformiaatin ja rautaformiaatin valmistusmenetelmiä, kationinvaihtohartsien ominaisuuksia, ioninvaihtohartsien selektiivisyyttä ja alumiinin, raudan, magnesiumin ja sinkin vesikemiaa. Laboratoriokokeiden avulla tutkittiin sinkki-, magnesium-, rauta(II)- ja alumiiniformiaattien valmistusta ioninvaihdolla. Kokeet suoritettiin kolonnissa, joka oli pakattu makrohuokoisella tai geelimäisellä vahvalla kationin-vaihtohartsilla. Hartsi vaihdettiin natriummuodosta metallimuotoon metallikloridi- tai metallisulfaattiliuoksella.Metalli eluoitiin hartsista natriumformiaatilla. Formiaattien valmistus onnistui makrohuokoista vahvaa kationinvaihtohartsia käyttämällä. Rauta(II)formiaatin valmistus oli vaikeampaa kuin muiden formiaattien, koska rauta(II) hapettui osittain rauta(III):ksi valmistuksen aikana. Alumiiniformiaattia valmistettiin käyttäen sekä makrohuokoista että geelimäistä hartsia. Makrohuokoisen hartsin havaittiin soveltuvan geelimäistä hartsia paremmin alumiiniformiaatin valmistukseen. Kungeelimäistä hartsia käytettiin, noin 30 % alumiinista jäi kiinni hartsiin eikä siten eluoitunut. Ioninvaihdon selektiivisyyskertoimien saamiseksi suoritettiin tasapainokokeita. Selektiivisyyskertoimia käytettiin ioninvaihtokolonnin dynaamisessa simuloinnissa. Ioninvaihdon simuloiminen dynaamisella kolonnimallilla onnistui hyvin.

Discription of a New Calculation Method for Determination of Stoichiometric Dissociation Constants of WeakAcid in Salt Solutions from Potentiometric Titration Data

A recently developed calculation method to determine stoichiometric dissociation constants of weak acids from potentiometric titration data is described. The titration data from three different weak acids in aqueous salt solutions at 25 °C were used as examples of the use of the method. The salt alone determined the ionic strength of the solutions considered in this study, and salt molalities up to 0,5 mol kg -1 were used.

Utilization of steelmaking waste materials for production of calcium carbonate (CaCO3)

The steel industry produces, besides steel, also solid mineral by-products or slags, while it emits large quantities of carbon dioxide (CO2). Slags consist of various silicates and oxides which are formed in chemical reactions between the iron ore and the fluxing agents during the high temperature processing at the steel plant. Currently, these materials are recycled in the ironmaking processes, used as aggregates in construction, or landfilled as waste. The utilization rate of the steel slags can be increased by selectively extracting components from the mineral matrix. As an example, aqueous solutions of ammonium salts such as ammonium acetate, chloride and nitrate extract calcium quite selectively already at ambient temperature and pressure conditions. After the residual solids have been separated from the solution, calcium carbonate can be precipitated by feeding a CO2 flow through the solution. Precipitated calcium carbonate (PCC) is used in different applications as a filler material. Its largest consumer is the papermaking industry, which utilizes PCC because it enhances the optical properties of paper at a relatively low cost. Traditionally, PCC is manufactured from limestone, which is first calcined to calcium oxide, then slaked with water to calcium hydroxide and finally carbonated to PCC. This process emits large amounts of CO2, mainly because of the energy-intensive calcination step. This thesis presents research work on the scale-up of the above-mentioned ammonium salt based calcium extraction and carbonation method, named Slag2PCC. Extending the scope of the earlier studies, it is now shown that the parameters which mainly affect the calcium utilization efficiency are the solid-to-liquid ratio of steel slag and the ammonium salt solvent solution during extraction, the mean diameter of the slag particles, and the slag composition, especially the fractions of total calcium, silicon, vanadium and iron as well as the fraction of free calcium oxide. Regarding extraction kinetics, slag particle size, solid-to-liquid ratio and molar concentration of the solvent solution have the largest effect on the reaction rate. Solvent solution concentrations above 1 mol/L NH4Cl cause leaching of other elements besides calcium. Some of these such as iron and manganese result in solution coloring, which can be disadvantageous for the quality of the PCC product. Based on chemical composition analysis of the produced PCC samples, however, the product quality is mainly similar as in commercial products. Increasing the novelty of the work, other important parameters related to assessment of the PCC quality, such as particle size distribution and crystal morphology are studied as well. As in traditional PCC precipitation process, the ratio of calcium and carbonate ions controls the particle shape; a higher value for [Ca2+]/[CO32-] prefers precipitation of calcite polymorph, while vaterite forms when carbon species are present in excess. The third main polymorph, aragonite, is only formed at elevated temperatures, above 40-50 °C. In general, longer precipitation times cause transformation of vaterite to calcite or aragonite, but also result in particle agglomeration. The chemical equilibrium of ammonium and calcium ions and dissolved ammonia controlling the solution pH affects the particle sizes, too. Initial pH of 12-13 during the carbonation favors nonagglomerated particles with a diameter of 1 μm and smaller, while pH values of 9-10 generate more agglomerates of 10-20 μm. As a part of the research work, these findings are implemented in demonstrationscale experimental process setups. For the first time, the Slag2PCC technology is tested in scale of ~70 liters instead of laboratory scale only. Additionally, design of a setup of several hundreds of liters is discussed. For these purposes various process units such as inclined settlers and filters for solids separation, pumps and stirrers for material transfer and mixing as well as gas feeding equipment are dimensioned and developed. Overall emissions reduction of the current industrial processes and good product quality as the main targets, based on the performed partial life cycle assessment (LCA), it is most beneficial to utilize low concentration ammonium salt solutions for the Slag2PCC process. In this manner the post-treatment of the products does not require extensive use of washing and drying equipment, otherwise increasing the CO2 emissions of the process. The low solvent concentration Slag2PCC process causes negative CO2 emissions; thus, it can be seen as a carbon capture and utilization (CCU) method, which actually reduces the anthropogenic CO2 emissions compared to the alternative of not using the technology. Even if the amount of steel slag is too small for any substantial mitigation of global warming, the process can have both financial and environmental significance for individual steel manufacturers as a means to reduce the amounts of emitted CO2 and landfilled steel slag. Alternatively, it is possible to introduce the carbon dioxide directly into the mixture of steel slag and ammonium salt solution. The process would generate a 60-75% pure calcium carbonate mixture, the remaining 25-40% consisting of the residual steel slag. This calcium-rich material could be re-used in ironmaking as a fluxing agent instead of natural limestone. Even though this process option would require less process equipment compared to the Slag2PCC process, it still needs further studies regarding the practical usefulness of the products. Nevertheless, compared to several other CO2 emission reduction methods studied around the world, the within this thesis developed and studied processes have the advantage of existing markets for the produced materials, thus giving also a financial incentive for applying the technology in practice.

Jätevesien puhdistus jätevesialtaissa jäädyttämällä - Kartoitus potentiaalisista sovellutuksista Suomessa

Uusia jäteveden puhdistusprosesseja kartoitetaan Suomessakin esimerkiksi kiristyvien päästömääräyksien vuoksi sekä parempia kustannus- ja energiatehokkuuksia tavoiteltaessa. Jätevesien puhdistus on Suomessa jo nykyään hyvällä tasolla, mutta muun muassa raskasmetallien, torjunta-aineiden, hormonien ja lääkeaineiden pitoisuuksien kasvut jätevesissä asettavat haasteita nykyisin käytössä oleville jäteveden puhdistusmenetelmille, sillä niitä ei ole suunniteltu näiden aineiden talteenottoon ja suurin osa aineista jää veteen. Lisäksi jätevedet halutaan nähdä enemmänkin resurssina kuin jätteenä, josta voidaan ottaa talteen hyödyllisiä komponentteja, kuten suoloja. Alueilla, joissa vuorokauden keskilämpötila pysyttelee edes osan vuodesta pakkasella, veden luonnollista jäätymisprosessia voidaan käyttää hyväksi jäteveden puhdistuksessa. Tässä työssä selvitettiin kiteytymisen teorian ja aikaisempien tutkimusten avulla, millaisten jätevesien puhdistukseen jäädytyskiteytys sopii sekä pohdittiin menetelmän potentiaalisia sovelluskohteita Suomessa. Jäädytyskiteytyksen todettiin olevan turvallinen ja energiatehokas ratkaisu monien koostumukseltaan erilaisien jätevesien puhdistukseen. Menetelmällä voitaneen puhdistaa öljyisiä, orgaanisia ja/tai epäorgaanisia epäpuhtauksia tai raskasmetalleja sisältäviä sekä myrkyllisiä jätevesiä. Olosuhteet prosessille ovat parhaat Pohjois-Suomessa, jossa vuorokauden keskilämpötila pysyttelee nollan alapuolella noin seitsemän kuukautta vuodesta. Etelä-Suomessa vastaava luku on kolme. Menetelmän potentiaalisia sovelluskohteita ovat esimerkiksi kaivosteollisuuden ja kaatopaikkojen jätevedet, joiden puhdistukseen jäädytyskiteytys saattaisi soveltua erinomaisesti. Jäädyttämällä voitaisiin myös puhdistaa tekstiili- ja nahkateollisuuden jätevesiä, sillä niiden sisältämien väriaineiden erottaminen vedestä on perinteisillä jäteveden puhdistusmenetelmillä usein vaikeaa tai jopa mahdotonta. Suolojen kiteyttämiseen vaadittavia korkeampia suolapitoisuuksia todettiin löytyvän lähinnä membraaniprosessien, kuten käänteisosmoosin, rejektivesistä. Sopivimmat eutektiset olosuhteet kiteyttämiseen ovat natriumsulfaatilla, kaliumsulfaatilla ja natriumkarbonaatilla. Veden luonnollisen jäätymisprosessin hyödyntäminen jätevedenpuhdistuksessa on huomionarvoinen idea. Prosessin käyttöönottoa haittaavat esimerkiksi korkeat investointikustannukset, mutta ne tulevat todennäköisesti ajan myötä teknologian kehittyessä laskemaan. Lisäksi monet prosessiin liittyvät käytännön asiat ovat vielä tutkimuksen alla. On myös huomattava, että Suomessakaan lämpötila ei pysyttele koko vuotta pakkasella, joten jäädytyksen rinnalla on oltava jokin toinen prosessi, jolla jätevedet puhdistetaan lämpötilan ollessa nollan yläpuolella.

Freezing Point Depressions of Dilute Solutions of Alkali Metal Chlorides and Bromides

Freezing point depressions (¿Tf) of dilute solutions of several alkali metal chlorides and bromides were calculated by means of the best activity coefficient equations. In the calculations, Hückel, Hamer and Pitzer equationswere used for activity coefficients. The experimental ¿Tf values available in the literature for dilute LiCl, NaCl and KBr solutions can be predicted within experimental error by the Hückel equations used. The experimental ¿Tf values for dilute LiCl and KBr solutions can also be accurately calculated by corresponding Pitzer equations and those for dilute NaCl solutions by the Hamer equation for this salt. Neither Hamer nor Pitzer equations predict accurately the freezing points reported in the literature for LiBr and NaBr solutions. The ¿Tf values available for dilute solutions of RbCl, CsCl or CsBr are not known at the moment accurately because the existing data for these solutions are not precise. The freezing point depressions are tabulated in the present study for LiCl, NaCl and KBr solutions at several rounded molalities. The ¿Tf values in this table can be highly recommended. The activity coefficient equations used in the calculation of these values have been tested with almost allhigh-precision electrochemical data measured at 298.15 K.

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.

Natural freeze crystallization : purification of aqueous Na2SO4 solutions with cold air

The aim of this thesis was to examine efficiency of freeze crystallization and eutectic freeze crystallization in purification of wastewater by imitating natural freezing. In addition, a mathematic model based on heat transfer to determine ice thickness and ice growth rate was examined. Also, the amount of sodium sulfate crystallized at the eutectic point was under investigation. In literature part, advantages and applications of the freeze crystallization are discussed, and possibility to apply it in Northern hemisphere winter weather conditions is under study. Furthermore, main sources of sodium sulfate from Finnish industries are described. The experiments were carried out in modified chest freezer, where a fan was placed in order to obtain laminar air flow inside. Picolog PT-104 data logger was used to monitor temperature changes in the salt-water solution, and constant temperature was maintained in the crystallizer with Lauda RP 850 thermostat. The impurity of formed ice layer was determined by weighing ice samples after experiment and again after 24 hours drying to full dryness in oven. Volume of salt-water solution was also measured after experiment. The highest purity of formed ice layer was obtained with small temperature difference and with long freezing time. On the other hand, the amount of crystallized sodium sulfate was its greatest with long freezing time and higher temperature difference. The results obtained by the mathematic model and empirical results did not differ significantly in most of the experiments. However, the difference increased when salt-water mixture reached its eutectic point, leading to simultaneous ice and salt crystallization. Eutectic point was reached only with the highest salt concentration with one exception. In these cases, calculated values were in many cases greater than the experimental ones. In winter weather conditions freeze crystallization is cost-effective wastewater treatment method and rather simple. Nonetheless, the efficiency and separation rate are strongly depended on ambient temperature and its changes

Salt content labelling of foods in supermarkets in Finland

Selostus: Suolamerkinnät valintamyymälöiden pakatuissa elintarvikkeissa

Saltiness of coarsely ground cooked ham with reduced salt content

Selostus: Suolapitoisuuden pienentämisen vaikutus kinkkuleikkeen aistittuun suolaisuuteen

Purification and fractionation by nanotiltration in dairy and sugar and sweetener industry applications

Nanotiltration is a membrane separation method known for its special characteristic of rejecting multivalent ions and passing monovalent ions. Thus, it is commonly applied with dilute aqueous solutions in partial salt removal, like in drinking water production. The possibilities of nanofiltration have been studied and the technique applied in a wide branch of industries, e.g. the pulp and paper, the textile and the chemical processing industry. However, most present applications and most of the potential applications studied involve dilute solutions, the permeating stream being generally water containing monovalent salts. In this study nanotiltration is investigated more as a fractionation method. A well-known application in the dairy industry is concentration and partial salt removal from whey. Concentration and partial demineralization is beneficial for futher processing of whey as whey concentrates are used e.g. in baby foods. In the experiments of this study nanotiltration effectively reduced the monovalent salts in the whey concentrate. The main concern in this application is lactose leakage into the permeate. With the nanofiltration membranes used the lactose retentions were practically ? 99%. Another dairy application studied was the purification and reuse of cleaning solutions. This is an environmentally driven application. An 80% COD reduction by nanofiltration was observed for alkaline cleaning-in-place solution. Nanofiltration is not as commonly applied in the sugar and sweeteners industry as in the dairy industry. In this study one potential application was investigated, namely xylose purification from hemicellulose hydrolyzate. Xylose is raw material for xylitol production. Xylose separation from glucose was initially studied with xylose-glucose model solutions. The ability of nanofiltration to partially separate xylose into the permeate from rather concentrated xylose-glucose solutions (10 w-% and 30 w-%) became evident. The difference in size between xylose and glucose molecules according to any size measure is small, e.g. the Stokes diameter of glucose is 0.73 nm compared to 0.65 nm for xylose. In further experiments, xylose was purified into nanoliltration permeate from a hemicellulose hydrolyzate solution. The xylose content in the total solids was increased by 1.4—1.7 fold depending on temperature, pressure and feed composition.

Photocatalytic oxidation of humic substances and lignins in aqueous solutions

Tässä tutkimuksessa tarkastellaan kahden yleisen, veden ympäristökuormitusta aiheuttavan kemikaaliryhmän, ligniinin ja humusaineiden, fotokatalyyttistahapetusta (photocatalytic oxidation, PCO) vesiliuoksessa. Fotokatalyyttina käytettiin titaanidioksidia, jota säteilytettiin ultraviolettivalolla. Työssä selvitettiin useiden eri olosuhdeparametrien vaikutusta fotokatalyysiin. Tutkittavia parametreja olivat mm. kontaminanttien alkukonsentraatio, pH, vetyperoksidilisäys, rauta-ionien lisäys, fotokatalyysimenetelmä, fotokatalyytin pintakonsentraatioja titaanidioksidin määrä lasisissa mikropartikkeleissa. Ultraviolettivalon lähteinä käytettiin sekä keinovaloa että auringonvaloa. Katalyytin kantoaineena käytettiin huokoisia lasisia mikropartikkeleita, joiden pintaan kiinnittynyt titaanidioksidi pystyi hyvin vähentämään kontaminanttien määrää vedessä. Fotokatalyysin tehokkuus kasvoi humusaine- ja ligniinikonsentraatioiden kasvaessa. Korkeimmat hapetustehokkuudet kumallakin kontaminantilla saavutettiin neutraaleissa jalievästi emäksisissä olosuhteissa huolimatta siitä, että paras adsorboituminen tapahtui happamissa olosuhteissa. Tämän perusteella voidaan olettaa, että humusaineiden ja ligniinin hapetus tapahtuu pääosin radikaalimekanismilla. Vetyperoksidin lisääminen humusaineliuokseen lisäsi hapettumisnopeutta, vaikka näennäinen hapetustehokkuus ei muuttunut. Tämän perusteella vetyperoksidi hapetti myös humusaineita referenssinäytteessä. Ligniinin fotokatalyyttinen hapettuminen parani vetyperoksidilisäyksellä happamissa olosuhteissa johtuen lisääntyneestä OH-radikaalien muodostumisesta. Ligniini ei hapettunut vetyperoksidilla, jos fotokatalyyttiä ei¿ollut läsnä. Rauta-ionit eivät lisänneet humushappojen fotokatalyyttistähapettumista, mutta Fe2+-ionien lisäys aina konsentraatioon 0.05 mM johti ligniinin hapettumistehokkuuden voimakkaaseen kasvuun. Rauta-ionikonsentraation kasvattaminen edelleen johti ligniinin hapetustehokkuuden alenemiseen.

Evaluation of existing technologies in manufacturing of decorative solutions

Matkapuhelinvalmistajien välinen kilpailu kiristyy jatkuvasti. Tuotteiden ollessa teknisiltä ominaisuuksiltaan lähes samanvertaisia, asiakkaat alkavat kiinnittää huomiota myös puhelimen muihin ominaisuuksiin.Puhelimen koristeellisuudesta ja mandollisuudesta personoida matkapuhelin, on muodostumassa entistä tärkeämpiä tekijöitä puhelinvalmistajien välisessä kilpailussa. Asiakas ei myöskään ole valmis odottamaan puhelintaan, vaan haluaa puhelimensa nopesti. Lyhyt läpimenoaika on puhelinvalmistajille elintärkeä kilpailutekijä. Tämän työn tehtävänä on tutkija puhelinvalmistajien alihankkijan teknologisiamandollisuuksia laajentaa tuotevalikoimaansa vastaamaan tämän päivän tarpeita koristella matkaviestimiä. Teknologioioden sovellukset, Tuotantokustannukset, läpimenoajat ja teknologoiden riskit ovat tutkimuksen pääkohteet. Tavoitteena on saavuttaa käsitys kohdeyrityksen mandollisuuksista vastata asiakkaansa tarpeisiin olemassa olevilla teknologioilla ja niiden kombinaatioililla.

Calculation of Activity Coefficients of Uni-Univalent Electrolytes by Equations Containing No Adjustable Parameters in Aqueous Solutions at 298.15 K

Normally either the Güntelberg or Davies equation is used to predict activity coefficients of electrolytes in dilute solutions when no better equation is available. The validity of these equations and, additionally, of the parameter-free equations used in the Bates-Guggenheim convention and in the Pitzerformalism for activity coefficients were tested with experimentally determined activity coefficients of HCl, HBr, HI, LiCl, NaCl, KCl, RbCl, CsCl, NH4Cl, LiBr,NaBr and KBr in aqueous solutions at 298.15 K. The experimental activity coefficients of these electrolytes can be usually reproduced within experimental errorby means of a two-parameter equation of the Hückel type. The best Hückel equations were also determined for all electrolytes considered. The data used in the calculations of this study cover almost all reliable galvanic cell results available in the literature for the electrolytes considered. The results of the calculations reveal that the parameter-free activity coefficient equations can only beused for very dilute electrolyte solutions in thermodynamic studies.

Calculation of Activity Coefficients of Electrolytes of Other Charge Types than 1-1 by Equations Containing No Adjustable Parameters in Aqueous Solutions at 25 0C

Normally either the Güntelberg or Davies equation is used to predict activity coefficients of electrolytes in dilute solutions when no betterequation is available. The validity of these equations and, additionally, of the parameter-free equation used in the Bates-Guggenheim convention for activity coefficients were tested with experimentally determined activity coefficients of LaCl3, CaCl2, SrCl2 and BaCl2 in aqueous solutions at 298.15 K. The experimentalactivity coefficients of these electrolytes can be usually reproduced within experimental error by means of a two-parameter equation of the Hückel type. The best Hückel equations were also determined for all electrolytes considered. The data used in the calculations of this study cover almost all reliable galvanic cell results available in the literature for the electrolytes considered. The results of the calculations reveal that the parameter-free activity coefficient equations can only be used for very dilute electrolyte solutions in thermodynamic studies