Improving the competitiveness of electrolytic Zinc process by chemical reaction engineering approach

This doctoral thesis describes the development work performed on the leachand purification sections in the electrolytic zinc plant in Kokkola to increase the efficiency in these two stages, and thus the competitiveness of the plant. Since metallic zinc is a typical bulk product, the improvement of the competitiveness of a plant was mostly an issue of decreasing unit costs. The problems in the leaching were low recovery of valuable metals from raw materials, and that the available technology offered complicated and expensive processes to overcome this problem. In the purification, the main problem was consumption of zinc powder - up to four to six times the stoichiometric demand. This reduced the capacity of the plant as this zinc is re-circulated through the electrolysis, which is the absolute bottleneck in a zinc plant. Low selectivity gave low-grade and low-value precipitates for further processing to metallic copper, cadmium, cobalt and nickel. Knowledge of the underlying chemistry was poor and process interruptions causing losses of zinc production were frequent. Studies on leaching comprised the kinetics of ferrite leaching and jarosite precipitation, as well as the stability of jarosite in acidic plant solutions. A breakthrough came with the finding that jarosite could precipitate under conditions where ferrite would leach satisfactorily. Based on this discovery, a one-step process for the treatment of ferrite was developed. In the plant, the new process almost doubled the recovery of zinc from ferrite in the same equipment as the two-step jarosite process was operated in at that time. In a later expansion of the plant, investment savings were substantial compared to other technologies available. In the solution purification, the key finding was that Co, Ni, and Cu formed specific arsenides in the “hot arsenic zinc dust” step. This was utilized for the development of a three-step purification stage based on fluidized bed technology in all three steps, i.e. removal of Cu, Co and Cd. Both precipitation rates and selectivity increased, which strongly decreased the zinc powder consumption through a substantially suppressed hydrogen gas evolution. Better selectivity improved the value of the precipitates: cadmium, which caused environmental problems in the copper smelter, was reduced from 1-3% reported normally down to 0.05 %, and a cobalt cake with 15 % Co was easily produced in laboratory experiments in the cobalt removal. The zinc powder consumption in the plant for a solution containing Cu, Co, Ni and Cd (1000, 25, 30 and 350 mg/l, respectively), was around 1.8 g/l; i.e. only 1.4 times the stoichiometric demand – or, about 60% saving in powder consumption. Two processes for direct leaching of the concentrate under atmospheric conditions were developed, one of which was implemented in the Kokkola zinc plant. Compared to the existing pressure leach technology, savings were obtained mostly in investment. The scientific basis for the most important processes and process improvements is given in the doctoral thesis. This includes mathematical modeling and thermodynamic evaluation of experimental results and hypotheses developed. Five of the processes developed in this research and development program were implemented in the plant and are still operated. Even though these processes were developed with the focus on the plant in Kokkola, they can also be implemented at low cost in most of the zinc plants globally, and have thus a great significance in the development of the electrolytic zinc process in general.

Fungal succession on leaves of Alchornea triplinervia (Spreng.) Muell. Arg. submerged in a stream of an Atlantic Rainforest in the state of São Paulo, Brazil

Leaves of Alchornea triplinervia (Spreng.) Muell. Arg. were submerged in a stream in an Atlantic Rainforest in São Paulo state, Brazil, from July/1988 to June/1989 and from July/1989 to May/1990. Fungi were isolated by the leaf disks washing technique followed by plating on culture media and also by using baiting techniques (using substrates with chitin, keratin and cellulose), what resulted on 565 fungal registers corresponding to 81 taxa. The most common species found during this study of the fungal succession were Trichoderma viride Pers. ex S.F. Gray and Fusarium oxysporum Schlecht emend. Snyd. & Hans. (23 registers), Penicillium hirsutum Dierckx (21 registers), Fusarium solani (Mart.) Appel & Wollenw. emend. Snyd. & Hans. (17), followed by 14 registers of: Cylindrocladium scoparium Morgan, Triscelophorus monosporus Ingold and Polychytrium aggregatum Ajello. Although the monthly obtained mycota had been composed by species of different taxonomic groups, the fungal succession was defined by the initial presence of typical terrestrial leaf inhabiting fungi (mostly Deuteromycotina), followed by species of Mastigomycotina and Zygomycotina. Combining culture methods and baiting techniques, it was possible to verify the presence of terrestrial fungi on the decomposition of submerged leaves and the importance of zoosporic fungi in the fungal succession. This is the first paper about the fungal succession on the decomposition of leaves submerged in a lotic ecosystem in Brazil.

Hypoksisen fenotyypin pään ja kaulan alueen levyepiteelikarsinooman sädehoitoresistenssi

Pään ja kaulan alueen levyepiteelin syöpiä kutsutaan karsinoomiksi. Kasvaimet luokitellaan vaikeahoitoisiksi ja niihin liittyy korkea potilaskuolleisuus. Yleisimmät pään ja kaulan alueen levyepiteelikarsinooman hoitomenetelmät ovat säde- ja leikkaushoito, joihin liitetään yhdistelmänä kemoterapiaa. Kasvaimen morfologia, sen puutteellinen tai rakenteellisesti poikkeava verisuonitus voi aiheuttaa syöpäkudoksessa hapenpuutteesta kärsiviä hypoksisia alueita. Erityisesti syövässä hapenpuute toimii syöpäsolupopulaatiossa valintatekijänä. Muuttuneet olosuhteet suosivat solupopulaatioita, jotka pystyvät sopeuttamaan genotyyppinsä mukauttamana fenotyyppinsä vähähappiseen ympäristöön. Tämän katsotaan olevan potilaan hoitoennusteen kannalta huono prognostinen merkki. Hapenpuute indusoi soluissa voimakkaan HIF-1- eli hypoksian indusoiman transkriptiofaktori-1 stabilisaation ja ekspression kasvun. Proteiinin on havaittu oleva eräs merkittävin solun sisäisten vasteiden säätelijä hypoksiassa. HIF-1 koostuu kahdesta alayksiköstä, jonka alpha-alayksikön stabiliteetti on hapen osapaineen säätelemä. Mikäli happea on riittävä pitoisuus soluissa, HIF-1alfa hajoaa soluissa. Hypoksiassa alfa-domeeni sitoutuu beta-alayksikköön muodostaen stabiilin toiminnallisen geenien ilmentymiseen vaikuttavan transkriptiofaktorin. Pro gradu- tutkielmassa tarkasteltiin aluksi neljän pään ja kaulan alueen syöpäpotilaiden kasvaimista eristettyjen UT-SCC-solulinjojen (UT-SCC-8, -25, -34 ja -74A) morfologiaa ja kasvua. Solujen jakautumisnopeutta uudella alustalla tutkittiin PE(%)- eli plating efficiency-menetelmällä. Soluja siirrostettiin uudelle kasvualustalle, josta niiden määrä laskettiin vuorokauden kuluttua. UT-SCC-74A-linja sieti parhaiten uuden kasvuympäristön asettaman rasitteen. Sädeherkkyys määritettiin tutkimalla UT-SCC-74A-linjan solujen asteittaista vastetta erisuuruisiin sädeannoksiin (Gy). Tulosten perusteella laskettiin linjan sisäistä sädeherkkyyttä kuvaava AUC-arvo. Työn toisessa osassa tarkasteltiin HIF-1alfa:n ekspression riippuvuutta hapen läsnäolosta soluissa molekyylibiologisin menetelmin. UT-SCC-74A-solulinja osoittautui sädeherkkyysmäärityksessä AUC-arvonsa perusteella suhteellisen säderesistentiksi. Lisäksi kyseisen linjan soluista vaimennettiin HIF-1alfa-geeni, jonka ekspression häviäminen todennettiin hypoksia-altistuskokeiden jälkeen. Proteiinin puuttuminen vähähappisista olosuhteista huolimatta osoitti geeninhiljennyksen onnistuneen koejärjestelyissä.

Optical spectroscopy of organic material based on C60

The structure and optical properties of thin films based on C60 materials are studied. Reproducible vacuum method of thin fullerene films production with Cd impurity on Si, glass and mica surfaces is developed. Surface morphology of the films are investigated by AFM and SEM methods. The ab initio quantum - chemical calculations of the geometry, total energy and excited energy states of complex fullerene- cadmium telluride supramolecules are performed. Photoluminescence spectra of composite thin films based on C60 before and after X-ray irradiation were measured. The intensity of additional peaks is defined as the charge composition due to the type of substrate. These results are interpreted as an appearance of the dipole-allowed transitions in the fullerene excited singlet states spectrum cause of an interference with cadmium telluride. X-ray irradiated films were investigated, and additional peaks in photoluminescence spectra were detected. These peaks appear as a result of molecular complexes formation from C60CdTe mixture and dimerization of the films. Density functional B3LYP quantum-chemical calculations for C60CdTe, molecular complexes, (C60)2 and C120O dimers were performed to elucidate some experimental results.

Pharmacology and toxicology of diphenyl diselenide in several biological models

The pharmacology of synthetic organoselenium compounds indicates that they can be used as antioxidants, enzyme inhibitors, neuroprotectors, anti-tumor and anti-infectious agents, and immunomodulators. In this review, we focus on the effects of diphenyl diselenide (DPDS) in various biological model organisms. DPDS possesses antioxidant activity, confirmed in several in vitro and in vivo systems, and thus has a protective effect against hepatic, renal and gastric injuries, in addition to its neuroprotective activity. The activity of the compound on the central nervous system has been studied since DPDS has lipophilic characteristics, increasing adenylyl cyclase activity and inhibiting glutamate and MK-801 binding to rat synaptic membranes. Systemic administration facilitates the formation of long-term object recognition memory in mice and has a protective effect against brain ischemia and on reserpine-induced orofacial dyskinesia in rats. On the other hand, DPDS may be toxic, mainly because of its interaction with thiol groups. In the yeast Saccharomyces cerevisiae, the molecule acts as a pro-oxidant by depleting free glutathione. Administration to mice during cadmium intoxication has the opposite effect, reducing oxidative stress in various tissues. DPDS is a potent inhibitor of d-aminolevulinate dehydratase and chronic exposure to high doses of this compound has central effects on mouse brain, as well as liver and renal toxicity. Genotoxicity of this compound has been assessed in bacteria, haploid and diploid yeast and in a tumor cell line.

Bacterial ecology of tilapia fresh fillets and some factors that can influence their microbial quality

The purpose of research was to investigate the bacterial ecology of tilapia (Oreochromis niloticus) fresh fillets and some factors that can influence its microbial quality. Samples of fish cultivation water (n = 20), tilapia tegument and gut (n = 20) and fresh fillets (n = 20) were collected in an experimental tilapia aquaculture located in the city of Lavras, Minas Gerais, Brazil. Staphylococcus spp., Aeromonas spp., Enterococcus spp. and Enterobacteriaceae were quantified using selective plating. For the enumeration of Pseudomonas spp., the most probable number technique (MPN) was utilized. Bacterial colonies (n = 198) were identified by Gram strain and biochemical tests. Aeromonas spp., Pseudomonas spp., Enterococcus spp. and Enterobacteriaceae were found in the cultivation water (water from a fishpond cultivation), tegument, gut, and fresh fillets. Staphylococcus spp. was not isolated in the cultivation water. Salmonella spp. was not detected. The count variable of 10 to 10³ CFU or MPN.(g or mL)-1. Associated to freshwater tilapia fillet processing, there is a large variety of microorganisms related to foodborne illnesses and fish products deterioration.

Heavy metals investigation in bovine tissues in Brazil

The aim of this study was to investigate the presence of arsenic, lead, and cadmium residues in samples of liver, kidney, and muscle of cattle during the years of 2002 to 2008. A total of 1017 samples from 20 Brazilian States were used. The samples were analyzed at the National Agricultural Laboratory using the atomic absorption spectrometry technique. Arsenic residues were detected in 15.7% of liver samples and 28.7% of kidney samples although no results have exceeded the MRL. With regard to lead, 16 samples of liver and 74 samples of kidney were contaminated (5.2 and 10.9%, respectively). Among these samples, only one liver and two of kidney samples had lead levels above the MRL. Cadmium was found with levels below the MRL in 12.5% of the liver samples, and only 3 samples (1%) were quantified above the MRL. Among the kidney samples, 420 (60.8% of the total tested) had cadmium residues, and five of them exceeded the limits established by legislation. It is concluded that the Brazilian meat meets the legislation requirements without putting consumer's healthy at risk since as it satisfies the national and international food-safety conditions.

Sähkökoagulaatiolaitteiston kehittäminen pintakäsittelylaitoksen jäteveden käsittelyyn

Tässä työssä kehitetään sähkökoagulaatiolaitteisto metallipinnoituslaitoksen jätevesien puhdistamiseen. Sähkökoagulaatio on sähkökemiallinen vedenpuhdistusprosessi, jossa hyödynnetään liukenevaa metallianodia. Sähkövirta irrottaa anodilta metalli-ioneja, jotka yhdistyvät vapaiden hydroksidi-ionien kanssa. Syntyneet metallihydroksidit vetävät puoleensa veden epäpuhtauksia ja saostuvat. Tämän työn tavoitteena oli kehittää sähkökoagulaatiolaitteistosta korvaaja käytössä olleelle kemialliselle jätevedenpuhdistuslaitteistolle. Sähkökoaglaatiolaitteiston toivottiin parantavan jätevedenpuhdistuksen toimintavarmuutta ja pienentävän käyttökustannuksia. Prototyyppilaitteistolla suoritettujen kokeiden perusteella sähkökoagulaation todettiin olevan kemiallista jätevedenkäsittelyä toimintavarmempi. Käyttökustannusten todettiin olevan samaa tasoa tai korkeammat kuin kemiallisella menetelmällä. Laitteiston suunnittelussa sovellettiin järjestelmällistä koneensuunnittelua. Suunnittelussa saavutettiin sille asetetut tavoitteet. Osatoiminnoille löydettiin toimivat ratkaisut ja laite on helposti huollettavissa.

Jätteiden kemiallisten ominaisuuksien spektrometriset online-mittausmenetelmät

Tässä diplomityössä käsiteltiin spektrometrisia online-mittausmenetelmiä jätteiden kemiallisten ja fysikaalisten ominaisuuksien määrittämiseksi. Tavoitteena oli selvittää, mitä ominaisuuksia menetelmillä voidaan mitata ja kuinka luotettavia tuloksia mittauksilla saadaan. Diplomityössä suoritettiin kirjallisuuskatsaus, jossa käsiteltiin kolmen spektrometrisen menetelmän soveltuvuutta reaaliaikaisiin jätemittauksiin. Työn empiirisessä osassa FPXRFanalysaattorilla mitattiin neljän eri jätenäytteen alkuainepitoisuuksia. Mittauksen tarkoituksena oli selvittää, mitä alkuaineita menetelmällä voidaan mitata. FPXRF-analysaattorilla saatuja tuloksia verrattiin ICP-MS-menetelmällä saatuihin tuloksiin regressioanalyysin avulla. Työssä todettiin, että FPXRF-analysaattori sopii parhaiten kaliumin, kalsiumin, ja raudan pitoisuuksien määrittämiseen. Lisäksi lyijyn, sinkin, kromin, kloorin, kuparin, kadmiumin, arseenin, fosforin, molybdeenin ja vanadiinin määrittäminen on mahdollista, mutta tarkan pitoisuuden saamiseksi laboratoriomenetelmien käyttö voi olla tarpeen. Tutkituista jätenäytteistä menetelmä soveltui parhaiten tuhkalle ja kompostille niiden fyysisten ominaisuuksien, kuten homogeenisuuden ja kosteuspitoisuuden takia. Biojätteelle menetelmä soveltui huonosti. FPXRF-analysaattorin luotettavuuteen vaikuttaa näytteen kosteuspitoisuus, homogeenisuus, partikkelikoko, mittaustapa ja laitteen kalibrointi. Työssä tarkastelluilla menetelmillä ei voida tällä hetkellä täysin korvata laboratorioanalyyseja. FPXRF-analysaattoria voidaan kuitenkin käyttää kvalitatiiviseen tai semikvantitatiiviseen haitta-aineiden analysointiin, millä voidaan vähentää kalliiden laboratorioanalyysien tarvetta.

Far infrared optical properties of V and Cr doped Sb2Te3 /

The far infrared reflectance of Sb2Te3 , Sbi.97Vo.o3Te3 and Sbi.94Cr .o6Te3 was measured near normal incidence at different temperatures (between 45K and 300K). The direct current resistivities of the above samples were also measured between the temperatures of 4K and 300K. Also Kramers Kronig (KK) analyses were performed on the reflectance spectra to obtain the optical conductivities. In the doped samples, it was observed that a phonon at 62cm-1 softens to about 55cm-1 on decreasing the temperature from 295K to 45K. Also, it was observed that the plasma frequency of the doped samples is independent of doping. The scattering rate for the vanadium doped sample was seen to be greater than that for the chromium doped sample despite the fact that vanadium impurity density is less than that of chromium. The Drude-Lorentz model fits to the KK optical conductivity show that the samples used in this work are conventional metals. Definitive measurements of the temperature dependence of the scattering rate across the ferromagnetic transition await equipment changes allowing measurements at low temperature using the mercury cadmium telluride (MCT) detector.

Sample preparation and heavy metal determination by atomic spectrometry /

Microwave digestions of mercury in Standards Reference Material (SRM) coal samples with nitric acid and hydrogen peroxide in quartz vessels were compared with Teflon® vessel digestion by using flow injection cold vapor atomic absorption spectrometry. Teflon® vessels gave poor reproducibiUty and tended to deliver high values, while the digestion results from quartz vessel show good agreement with certificate values and better standard deviations. Trace level elements (Ag, Ba, Cd, Cr, Co, Cu, Fe, Mg, Mn, Mo, Pb, Sn, Ti, V and Zn) in used oil and residual oil samples were determined by inductively coupled plasma-optical emission spectrometry. Different microwave digestion programs were developed for each sample and most of the results are in good agreement with certified values. The disagreement with values for Ag was due to the precipitation of Ag in sample; while Sn, V and Zn values had good recoveries from the spike test, which suggests that these certified values might need to be reconsidered. Gold, silver, copper, cadmium, cobalt, nickel and zinc were determined by continuous hydride generation inductively coupled plasma-optical emission spectrometry. The performance of two sample introduction systems: MSIS™ and gas-liquid separator were compared. Under the respective optimum conditions, MSIS^"^ showed better sensitivity and lower detection limits for Ag, Cd, Cu, Co and similar values for Au, Ni and Zn to those for the gas-liquid separator.

Arsenic and germanium determination by hydride generation in the D.C. plasma optical emission spectrometer

Modifications to the commercial hydride generator, manufactured by Spectrametrics, resulted in improved operating procedure and enhancement of the arsenic and germanium signals. Experiments with arsenic(III) and arsenic(V) showed that identical reiults could be produced from both oxidation states. However, since arsenic(V) is reduced more slowly than arsenic(III), peak areas and not peak heights must be measured when the arsine is immediately stripped from the system (approximately 5 seconds reaction). When the reduction is allowed to proceed for 20 seconds before the arsine is stripped, peak heights may be used. For a 200 ng/mL solution, the relative standard deviation is 2.8% for As(III) and 3.8% for As(V). The detection limit for arsenic using the modified system is 0.50 ng/mL. Studies performed on As(V) standards show that the interferences from 1000 mg/L of nickel(II), cobalt(II), iron(III), copper(II), cadmium(II), and zinc(II) can be eliminated with the aid of 5 M Hel and 3% L-cystine. Conditions for the reduction of germanium to the corresponding hydride were investigated. The effect of different concentrations of HCl on the reduction of germanium to the covalent hydride in aqueous media by means of NaBH 4 solutions was assessed. Results show that the best response is accomplished at a pH of 1.7. The use of buffer solutions was similarly characterized. In both cases, results showed that the element is best reduced when the final pH of the solution after reaction is almost neutral. In addition, a more sensitive method, which includes the use of (NH4)2S208' has been developed. A 20% increase in the germanium signal is registered when compared to the signal achieved with Hel alone. Moreover, under these conditions, reduction of germanium could be accomplished, even when the solution's pH is neutral. For a 100 ng/mL germanium standard the rsd is 3%. The detection limit for germanium in 0.05 M Hel medium (pH 1.7) is 0.10 ng/mL and 0.09 ng/mL when ammonium persulphate is used in conjunction with Hel. Interferences from 1000 mg/L of iron(III), copper(II), cobalt(II), nickel(II), cadmium(II), lead(II), mercury(II), aluminum(III), tin(IV), arsenic(III), arsenic(V) and zinc(II) were studied and characterized. In this regard, the use of (NH4)ZS20S and Hel at a pH of 1.7 proved to be a successful mixture in the sbppression of the interferences caused by iron, copper, aluminum, tin, lead, and arsenic. The method was applied to the determination of germanium in cherts and iron ores. In addition, experiments with tin(IV) showed that a 15% increase in the tin signal can be accomplished in the presence of 1 mL of (NH4)2S20S 10% (m/V).

Investigation into the determination of arsenic by direct current plasma atomic emission spectrometer

Improvements have been made on the currently available hydride generator system manufactured by SpectraMetrics Incorporated, because the system was found to be unsatisfactory with respect to the following: 1. the drying agent, anhydrous calcium chloride, 2. the special sample tube, 3. the direction of argon flow through the Buchner funnel when it came to dealing with real sample, that is, with reference only to aqueous extracts of soil samples. Changes that were made on the system included the replacement of anhydrous calcium chloride with anhydrous calcium sulphate and the replacement of the special sample tube with a modified one made from silica. Re-directing the flow of argon through the top of the Buchner funnel appeared to make the system compatible with aqueous extracts of soil samples. The interferences from 1000 ~g/mL of nickel(II) , cobalt(II), iron(III), copper(II) have been eliminated with the aid of 1.4 M hydrochloric acid and 1% (weight/volume) L-cystine. Greater than 90% recovery of 0.3 ~g/mL arsenic signal was achieved in each case. Furthermore, 103% of arsenic signal was accomplished in the presence of 1000 ~g/mL cadmium with 5 M Hel. tVhen each of the interferents was present in solution at 1000 ppm, a recovery of 85% was achieved by using 5 M hydrochloric acid and 3% (weight/volume) L-cystine. Without L-cystine and when 1.4 M hydrochloric acid was used, the recoveries were 0% (Ni), 0% (Co), 88% (Fe), 15% (Cu), 18% (Cd). Similarly, a solution containing 1000 ppm of each interferent gave a zero percent recovery of arsenic. The reduction of trivalent and pentavalent arsenic at a pH less than one has also been investigated and shown to be quantitative if peak areas are measured. The reproducibility determination of a 0.3 Vg/mL standard arsenic solution by hydride generation shows a relative standard deviation of 3.4%. The detection limits with and without Porapak Q have been found to be 0.6 ng/mL and 1.0 ng/mL, respectively.

Synthesis of nanoporous materials for preconcentration and determination of trace elements by ICP-AES ; Investigation and elimination of the memory effects of mercury, gold, silver and boron in ICP-AES

Nanoporous materials with large surface area and well-ordered pore structure have been synthesized. Thiol groups were grafted on the materials' surface to make heavy metal ion pre-concentration media. The adsorption properties ofthe materials were explored. Mercury, gold and silver can be strongly adsorbed by these materials, even in the presence of alkaline earth metal ion. Though the materials can adsorb other heavy metal ions such as lead and copper, they show differential adsorption ability when several ions are present in solution. The adsorption sequence is: mercury> == silver> copper » lead and cadmium. In the second part of this work, the memory effects of mercury, gold, silver and boron were investigated. The addition of 2% L-cysteine and 1% thiourea eliminates the problems of the three metal ions completely. The wash-out time for mercury dropped from more than 20 minutes to 18 seconds, and the wash-out time for gold decreased from more than 30 minutes to 49 seconds. The memory effect of boron can be reduced by the use of mannitol.

The band structure of Cd0

The Augmented Pl ane Wave Method has been used to calculate the one-electron energy band structure of CdO. Energy eigenva l ues were calculated along three symmetry lines and for some other general wave-vectors of interest.