Haihtuvien rasvahappojen analysoiminen nestekromatografisesti

Tämä opinnäytetyö käsittelee nestekromatografian käyttöä haihtuvien orgaanisten happojen (VFA) määrityksessä. Työ sisältää kirjallisuuskatsauksen ja kokeellisen osan. Aluksi tutkittiin kirjallisuuden perusteella bioreaktorin tuotevirrassa esiintyvän VFA:n määrityksen merkitystä reaktorin toiminnalle ja säädölle. Erityisesti tarkasteltiin haihtuvien orgaanisten happojen merkitystä biokaasuntuotannossa. Todettiin, että VFA:n määrä biokaasulaitoksen nestemäisessä tuotevirrassa on hyvä, mutta usein hitaasti määritettävä ilmaisin reaktorin kehittyville toimintahäiriöille, sillä VFA:n määrän kasvu on useimmiten merkki reaktorissa tapahtuvasta inhibitiosta. Lisäksi kirjallisuusosassa esiteltiin perustietoja kromatografiasta menetelmänä. Kromatografiset menetelmät ovat erotusmenetelmiä, joissa liikkuvaan faasiin liuenneet yhdisteet erotetaan toisistaan niiden paikallaan pysyvässä faasissa viettämän ajan perusteella. Retentioajat ja yhdisteiden pitoisuudet luetaan kromatografin ohjelmiston piirtämältä kromatorammilta. Opinnäytetyön kokeellisessa osassa tutkittiin muutamien haihtuvien orgaanisten happojen erottamista annetulla nestekromatografisella laitteistolla kolmiosaisessa koejärjestelyssä. Tutkitut hapot olivat etikkahappo, propionihappo, voihappo, isovoihappo, valeriaanahappo, isovaleriaanahappo, heksaanihappo ja isoheksaanihappo. Kokeiden tarkoituksena oli selvittää, erottuvatko valitut hapot toisistaan riittävän selkeästi ja tarvittaessa kehittää menetelmää tarkoitukseen paremmin sopivaksi. Aluksi tutkittaville yhdisteille määritettiin retentioajat ajamalla ne kromatografille yksikomponenttiliuoksina. Toisessa vaiheessa valituista hapoista valmistettiin tunnetut liuokset, joiden avulla nestekromatografi kalibroitiin. Samalla määritettiin yhdisteille sopivat kalibrointialueet annetulla laitteistolla. Lopuksi valmistettiin yksikomponenttiliuokset natrium- ja etyyliasetaateista ja määritettiin niiden retentioajat. Kokeen tarkoituksena oli selvittää näkyvätkö kyseiset yhdisteet kromatogrammissa samalla paikalla etikkahapon kanssa. Ensimmäisten kokeiden tuloksina saatiin, että kaikki tutkitut hapot erosivat toisistaan käytetyllä menetelmällä riittävän hyvin. Toisessa kokeessa todettiin, että kalibroinnit onnistuivat enimmäkseen hyvin oletusasetuksilla muutamia poikkeuksia lukuun ottamatta. Kolmannen kokeen tuloksiksi saatiin, että natriumasetaatti näkyy kromatogrammilla etikkahapon piikissä, kun taas etyyliasetaatti hajosi erotuksen aikana muodostaen useita epäsymmetrisiä piikkejä

Effect of gypsum content on CSAB cement-based immobilization of Se and SO₄ from industrial filter sludge and sodium–selenium salts

Abstract Release of different heavy metals from various industries is a significant environmental hazard worldwide. In order to reduce the threat from these chemicals, different treatment methods are needed to make them harmless. This study approaches the problem by examining the effect of gypsum content for immobilization of selenium oxyanions selenite and selenate, and sulfate, with calcium sulfoaluminate belite (CSAB) cement-based ettringite binder systems. The study has two experimental sections. In the first section, an industrial filter sludge with high concentrations of selenium and sulfate is immobilized with CSAB and varying amounts of gypsum. The immobilization is efficient and reducing the gypsum amount in the hydrating mixture enhances the incorporation of both selenium and sulfate. The binding occurs through encapsulation and incorporation into ettringite and other hydrated phases. In the second section, two reagent grade sodium–selenium salts, sodium selenite and sodium selenate, are mixed with CSAB and varying amounts of gypsum. The immobilization is not effective and ettringite is not formed in large quantities, most likely due to high sodium content in the reacting system

Hazardous industrial filter sludge immobilization with mayenite and gypsum

Abstract Heavy metals escaping from industrial processes and industrial waste are a significant environmental hazard all around the globe. Since they cannot be destroyed, the only way to manage the pollution is to capture and contain the hazardous components. This study focuses on stabilization-solidification of a highly toxic industrial filter slag that contains a range of different heavy metals in extremely high quantities. The stabilization-solidification treatment was executed with a mayenite and gypsum based solid cementitious binder. The major components that were monitored during the study were selenium, lead and sulphate. Different ratios of gypsum addition were tested in order to observe the effect of total sulphate content in the system to the immobilization efficiency of anionic selenium and sulphate. During the experiments, all cationic heavy metals were immobilized efficiently, most of them achieving the immobilization efficiencies of more than 99.9%. By adjusting the sulphate content of the system, the immobilization efficiency of selenium was improved from 95.669% to 99.925% and the immobilization efficiency of sulphate raised from 96.069% to above 99.964%. Controversially, the immobilization of lead was at its highest (99.999%) with high sulphate content and dropped to 98.162% as the sulphate rate decreased. The results show clearly that mayenite has good potential for stabilization-solidification applications

Immobilization of heavy metals, selenate, and sulfate from a hazardous industrial side stream by using calcium sulfoaluminate-belite cement

Abstract Release of heavy metals from different industries and industrial waste is a major global threat for as well humans as ecosystems. In this study, immobilization of an industrial filter sludge (FS) with an extremely high content of several heavy metals (24.6 wt% Pb, 21.7 wt% Hg, and 9.00 wt% Se) and sulfate via calcium sulfoaluminate-belite (CSAB) cement was tested. The ratios of 25%, 50% and 75% of CSAB addition were tested, and the target was to achieve immobilization of the hazardous components. The leaching of Pb, Hg, SeO₄, SO₄, Ni, Cd, Cu, and As was monitored, and the structure of the immobilized materials was examined via X-ray powder diffraction (XRD) and field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM-EDS) analysis. It was observed that Hg, Cu, As, Cd, and Ni were immobilized completely and leaching of Pb was reduced by 69% from the theoretical release. On the other hand, the leaching of SeO₄ and SO₄ experienced major increase when CSAB was added. XRD indicated significant ettringite formation as the amount of added CSAB increased, and the formation of gypsum as the amount was decreased. FESEM-EDS indicated that the immobilization was largely based on encapsulation into the CSAB binder, but chemical immobilization into the ettringite binder was also observed. It was concluded that the increased release of SO₄ and SeO₄ might have resulted from an excess amount of sulfates (added gypsum) during hydration

One-part geopolymers from mining residues – effect of thermal treatment on three different tailings

Abstract Use of mine tailings as an aluminosilicate precursor in alkali activation is becoming an interesting alternative to manage the high-volume of waste generated from mining industries. However, very few tailings have so far been studied for their mineralogical properties and alkali activation potential. This study aims at understanding the ability of mine tailings from phosphate, kaolinite and lithium mines for their efficient participation in alkali activation. Biotite, muscovite, kaolinite, albite, and quartz were found to be the major minerals present in them. The impact of variation in mineralogy on silica and alumina solubility of these tailings was analyzed. The solubility was found to be high in impure kaolinite compared to the other two. Effectiveness of thermal treatment (750 °C and 900 °C) on improving the reactivity of these tailings in alkaline condition was also investigated. It was observed from the results that the effect of thermal treatment on the crystalline structure and solubility of an aluminosilicate material mainly depends on the mineral structure of the material, as well as the treatment temperature. Interestingly, thermal treatment reduced the solubility of lithium tailings with albite and quartz mineral. Effort has been made to relate the strength attained by alkali activation of mine tailings to their solubility values. However, despite of the higher solubility offered by impure kaolinite, phosphate tailings gives the maximum strength improvement by 62%. This can be due to the presence of calcium compounds in phosphate tailings that resulted in additional hydration products

Solidification/stabilization of gold mine tailings using calcium sulfoaluminate-belite cement

Abstract In this study, calcium sulfoaluminate-belite cement (CSAB) was used to stabilize gold mine tailings, which are challenging materials to effectively immobilize due to high heavy metal and sulfate content. The hydration of CSAB cement yields ettringite and monosulfate with good capability for immobilizing sulfates and oxyanions in their crystal structure, in addition to physical encapsulation/solidification in a cementitious matrix. Different mix designs of CSAB cement and mine tailings were prepared, and the samples were cured at room temperature. Mechanical strength and heavy metal leaching were analyzed after 7 days, 28 days, and 90 days of curing, and the phase composition (XRD), thermogravimetric analysis (TGA), and microstructure (FESEM) were also studied. All harmful elements (cationic and oxyanion elements) were effectively immobilized during 7 days of curing, and the heavy metal immobilization remained constant after longer curing, according to an environmental leaching test. High mechanical strength results and good sulfate immobilization were obtained with mine tailing content up to 50 w-% of total binder material. With higher mine tailing content (75 w-% and 90 w-%), the mechanical strength and immobilization ability substantially decreased