Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Michigan, 1921.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references. Also available on the Internet.

No description available.

<p> The nature of the coloured solutions of selenium and tellurium in sulfuric acid has been investigated using mainly cryoscopic, conductimetric, and spectrophotometric techniques. Evidence has been obtained for the new species Se₈²⁺ and Se₄²⁺ in the green and yellow solutions of selenium respectively. Evidence on red solutions of tellurium seems consistent with the formulation Te₄²⁺. Solid compounds analysing as Se₄S₄O₁₃, Se₄(HS₂O₇)₂ and TeO(HS₂O₇)₂ have been prepared and characterised. </p> <P> Solutions of some selenium(IV) and selenium(VI) compounds have been examined. It is shown that a number of phosphates and arsenates ionise in sulfuric acid to give the P(OH)₄⁺ and As(OH)₄⁺ ions respectively. Ammonium metavanadate and vanadium pentoxide ionise to give the complex acid H[VO(HSO₄)₄]. Potassium chromate and dichromate ionise to give the compound CrO₂(HSO₄)₂ and potassium permanganate ionises to give the non-electrolyte MnO₃∙SO₄H. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.

The present thesis presents new renewable, antimicrobial and biodegradable superabsorbent polymers (SAPs), produced from the cell wall of zygomycetes fungi. The cell wall was characterized and chitosan, being one of the most important ingredients, was extracted, purified, and converted to SAP for use in disposable personal care products designed for absorption of different body fluids. The cell wall of zygomycetes fungi was characterized by subsequent hydrolysis with sulfuric and nitrous acids and analyses of the products. The main ingredients of the cell wall were found to be polyphosphates (4-20%) and copolymers of glucosamine and N-acetyl glucosamine, i.e. chitin and chitosan (45-85%). The proportion of each of these components was significantly affected by the fungal strain and also the cultivation conditions. Moreover, dual functions of dilute sulfuric acid in relation to chitosan, i.e. dissolution at high temperatures and precipitation at lowered temperatures, were discovered and thus used as a basis for development of a new method for extraction and purification of the fungal chitosan. Treatment of the cell wall with dilute sulfuric acid at room temperature resulted in considerable dissolution of the cell wall polyphosphates, while chitosan and chitin remained intact in the cell wall residue. Further treatment of this cell wall residue, with fresh acid at 120°C, resulted in dissolution of chitosan and its separation from the remaining chitin/chitosan of the cell wall skeleton which was not soluble in hot acid. Finally, the purified fungal chitosan (0.34 g/g cell wall) was recovered by precipitation at lowered temperatures and pH 8-10. The purity and the yield of fungal chitosan in the new method were significantly higher than that were obtained in the traditional acetic acid extraction method. As a reference to pure chitosan, SAP from shellfish chitosan, was produced by conversion of this biopolymer into water soluble carboxymethyl chitosan (CMCS), gelation of CMCS with glutaraldehyde in aqueous solutions (1-2%), and drying the resultant gel. Effects of carboxymethylation, gelation and drying conditions on the water binding capacity (WBC) of the final products, were investigated. Finally, choosing the best condition, a biological superabsorbent was produced from zygomycetes chitosan. The CMCS-based SAPs were able to absorb up to 200 g water/g SAP. The WBC of the best SAP in urine and saline solutions was 40 and 32 g/g respectively, which is comparable to the WBC of commercially acceptable SAPs under identical conditions (34-57 and 30-37 g/g respectively). / <p>Disputationen sker fredagen den 1 oktober kl. 10.00 i KA-salen, Kemigården 4, Chalmers, Göteborg</p>

No description available.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Abstract Zinc is a common metal, and has a central role in the production of galvanised bulk products, battery applications and fertilisers. Its production relies mainly on the leaching of zinc minerals with sulfuric acid, followed by purification and electrowinning. In this thesis an internally consistent thermodynamic model for the industrially important ZnSO₄-H₂SO₄-H₂O system was developed. Model parameters were optimised using available literature data and new experimental freezing point and density data determined in this work. With Gibbs energy minimisation algorithms embedded in commercial software, such as ChemSheet and FactSage, the developed model can be used to calculate easily phase equilibria and thermodynamic properties of aqueous zinc sulfate solutions and solid zinc sulfate phases, including activity coefficients, enthalpy changes, heat capacities, densities and solubilities, in a wide range of temperature, pressure and sulfuric acid concentrations. Solution non-ideality was treated with the original Pitzer model with electrostatic mixing terms included. Applicability of thermodynamic approach and the developed model was demonstrated by two separate case studies on the hydrometallurgical zinc process. Precipitation of amorphous silica during hot acid leach was studied experimentally. Its solubility in the process solution was also successfully predicted using the thermodynamic approach. To study crystallisation of gypsum during the gypsum precipitation stage, the model was expanded by addition of the Ca²⁺ ion. The model calculations showed good agreement with the experienced Ca²⁺ levels. The results of this thesis have found immediate use in understanding the various stages of the electrolytic zinc process. The obtained results also form a basis on which new, more advanced tools for managing and studying the process can be developed. / Tiivistelmä Sinkki on yleinen metalli, ja sillä on keskeinen rooli sinkittyjen terästuotteiden, paristojen ja jopa lannoitteiden valmistuksessa. Sen tuotanto perustuu sinkkipitoisten mineraalien rikkihappoliuotukseen, muodostuneen prossessiliuoksen puhdistukseen ja lopulta metallisen sinkin elektrolyysitalteenottoon. Tässä työssä kehitettiin termodynaaminen malli teollisesti tärkeälle ZnSO₄-H₂SO₄-H₂O -systeemille. Malliparametrit määritettiin kirjallisuudessa esitetyistä tuloksista ja tässä työssä tehdyistä uusista jäätymispiste- ja tiheysmittauksista. Käyttämällä kaupallisia Gibbsin energian minimointialgoritmiin perustuvia ohjelmistoja, kuten ChemSheet tai FactSage, tässä työssä kehitetyllä mallilla voidaan helposti kuvata sinkkisulfaattipitoisten vesiliuosten faasitasapainoja ja laskea systeemin termodynaamisia ominaisuuksia. Malliin sisällytettyihin ominaisuuksiin kuuluvat systeemin komponenttien aktiivisuudet, entalpiamuutokset, lämpökapasiteetit sekä tiheydet laajalla lämpötila-, paine- ja rikkihapon pitoisuusalueella. Liuoksen epäideaalisuutta kuvattiin Pitzerin ioniaktiivisuusmallilla. Työssä sinkkisulfaattiliuoksille kehitettyä mallia testattiin kahdessa sinkintuotannon kannalta keskeisessä tapaustutkimuksessa. Amorfisen piidioksidin saostumista vahvahappoliuotuksen aikana tutkittiin kokeellisesti ja laskennallisesti. Amorfisen piidioksidin liukoisuus prosessiliuokseen ennustettiin onnistuneesti. Kipsinpoistoprosessin tutkimusta varten mallia laajennettiin lisäämällä siihen Ca²⁺-ioni. Mallilla laskettiin kipsin liukoisuus prosessiliuokseen. Saadut tulokset vastasivat hyvin käytännössä havaittuja arvoja. Tutkimuksen tuloksia on suoraan hyödynnetty sinkintuotantoprosessin ymmärtämisessä. Ne myös mahdollistavat jatkossa edistyneempien työkalujen kehittämisen niin prosessin hallintaan kuin tutkimukseenkin.