Adsorption of hydrogen sulfide by modified cellulose nano/microcrystals

Hydrogen sulfide is toxic and hazardous pollutant. It has been under great interest for past few years because of all the time tighten environmental regulations and increased interest of mining. Hydrogen sulfide gas originates from mining and wastewater treatment systems have caused death in two cases. It also causes acid rains and corrosion for wastewater pipelines. The aim of this master thesis was to study if chemically modified cellulose nanocrystals could be used as adsorbents to purify hydrogen sulfide out from water and what are the adsorption capacities of these adsorbents. The effects of pH and backgrounds on adsorption capacities of different adsorbents are tested. In theoretical section hydrogen sulfide, its properties and different purification methods are presented. Also analytical detection methods for hydrogen sulfide are presented. Cellulose nano/microcrystals, properties, application and different modification methods are discussed and finally theory of adsorption and modeling of adsorption is shortly discussed. In experimental section different cellulose nanocrystals based adsorbents are prepared and tested at different hydrogen sulfide concentrations and in different conditions. Result of experimental section was that the highest adsorption capacity at one component adsorption had wet MFC/CaCO3. At different pH the adsorption capacities of adsorbents changed quite dramatically. Also change of hydrogen sulfide solution background did have effect on adsorption capacities. Although, when tested adsorbents’ adsorption capacities are compared to those find in literatures, it seems that more development of MFC based adsorbents is needed.

Polymeeriadsorbenttien käyttö kromatografisessa erotuksessa

Polymeeriadsorbentteja valmistetaan silloittamalla styreeniä, akrylaattia tai fenoliformaldehydiä. Useimmiten ristisilloittajana toimii divinyylibentseeni. Polymeeriadsorbenteissa ei itsessään ole ioninvaihtoryhmiä, joten ne sopivat ionittomien ja heikosti ionisoitujen aineiden adsorptioon. Usein polymeeriadsorbentteja käytetään vaihtoehtona aktiivihiilelle eri sovelluksissa. Työn kirjallisuusosassa on katsaus polymeeriadsorbenttien sovelluksiin lähinnä elintarviketeollisuudessa. Lisäksi siinä selvitetään polymeeriadsorbenttien rakennetta ja synteesimenetelmiä. Kokeellisessa osassa tutkittiin valittujen styreeni- ja akrylaattipohjaisten polymeeriadsorbenttien soveltuvuutta kromatografisen erotuksen stationaarifaasiksi. Kromatografia-ajoissa käytettiin eluenttina vettä, jonka lämpötila oli pääasiassa joko 75 tai 125 °C. Jälkimmäisessä lämpötilassa vesi on paineistettua neste, jota kutsutaan myös alikriittiseksi vedeksi. Malliaineina oli eri sokereita, aminohappoja sekä bentsoehappoa ja bentsyylialkoholia. Kromatografisen soveltuvuuden lisäksi selvitettiin adsorbenttien termistä kestävyyttä ja rakennetta. Termisesti polymeeriadsorbentit kestivät hyvin lämpötiloja 125 °C:eseen saakka. Polymeeriadsorbenteilla, joilla on suuri ominaispinta-ala, on myös suuri adsorptiokapasiteetti. Styreenipohjaiset adsorbentit erottivat kaikkia tutkittuja malliaineita akrylaattipohjaisia paremmin. Jotkut adsorbentit eivät erottaneet mitään tutkituista yhdisteistä. Lämpötilan nostaminen kavensi piikkejä ja nopeutti malliaineiden retentoitumista, mutta ei parantanut erottumista.

Modified nano- and microcellulose based adsorption materials in water treatment

In recent decades, industrial activity growth and increasing water usage worldwide have led to the release of various pollutants, such as toxic heavy metals and nutrients, into the aquatic environment. Modified nanocellulose and microcellulose-based adsorption materials have the potential to remove these contaminants from aqueous solutions. The present research consisted of the preparation of five different nano/microcellulose-based adsorbents, their characterization, the study of adsorption kinetics and isotherms, the determination of adsorption mechanisms, and an evaluation of adsorbents’ regeneration properties. The same well known reactions and modification methods that were used for modifying conventional cellulose also worked for microfibrillated cellulose (MFC). The use of succinic anhydride modified mercerized nanocellulose, and aminosilane and hydroxyapatite modified nanostructured MFC for the removal of heavy metals from aqueous solutions exhibited promising results. Aminosilane, epoxy and hydroxyapatite modified MFC could be used as a promising alternative for H2S removal from aqueous solutions. In addition, new knowledge about the adsorption properties of carbonated hydroxyapatite modified MFC as multifunctional adsorbent for the removal of both cations and anions ions from water was obtained. The maghemite nanoparticles (Fe3O4) modified MFC was found to be a highly promising adsorbent for the removal of As(V) from aqueous solutions due to its magnetic properties, high surface area, and high adsorption capacity . The maximum removal efficiencies of each adsorbent were studied in batch mode. The results of adsorption kinetics indicated very fast removal rates for all the studied pollutants. Modeling of adsorption isotherms and adsorption kinetics using various theoretical models provided information about the adsorbent’s surface properties and the adsorption mechanisms. This knowledge is important for instance, in designing water treatment units/plants. Furthermore, the correspondence between the theory behind the model and properties of the adsorbent as well as adsorption mechanisms were also discussed. On the whole, both the experimental results and theoretical considerations supported the potential applicability of the studied nano/microcellulose-based adsorbents in water treatment applications.

Adsorption of arsenic from ammonia containing waste water by ferrous hydroxide waste

Arsenic is a toxic substance. The amount of arsenic in waste water is a raising problem because of increasing mining industry. Arsenic is connected to cancers in areas where arsenic concentration in drinking water is higher than recommendations. The main object in this master’s thesis was to research how ferrous hydroxide waste material is adsorbed arsenic from ammonia containing waste water. In this master’s thesis there is two parts: theoretical and experimental part. In theoretical part harmful effects of arsenic, theory of adsorption, isotherms modeling of adsorption and analysis methods of arsenic are described. In experimental part adsorption capacity of ferrous hydroxide waste material and adsorption time with different concentrations of arsenic were studied. Waste material was modified with two modification methods. Based on experimental results the adsorption capacity of waste material was high. The problem with waste material was that at same time with arsenic adsorption sulfur was dissolving in solution. Waste material was purified from sulfur but purification methods were not efficient enough. Purification methods require more research.

Ammoniumin, fosfaatin ja nitraatin poisto adsorption avulla

Kiinnostus ravinneionien ammoniumin, fosfaatin ja nitraatin poistoon liittyy niiden ne-gatiivisiin ympäristövaikutuksiin ja niiden poistoon jätevesistä on olemassa erilaisia tekniikoita. Tässä työssä ionien poistoa tutkittiin adsorptiotekniikan avulla. Siinä perus-ajatuksena on ionin kiinnittyminen adsorbentin pintaan, jolloin sen poistaminen käsitel-tävästä vedestä on mahdollista. Tässä diplomityössä tutkittiin eri adsorbentteja ammoniumin, fosfaatin ja nitraatin poistoon, ja päämääränä oli niiden yhtäaikainen poistaminen. Kokeita tehtiin niin laboratoriossa valmistetuille ravinneliuoksille kuin Yara Suomi Oy:n Siilinjärven (Yara) toimipaikalta toimitetuille vesille. Yaran vesien osalta pääpaino oli ammoniumin poistossa. Tutkimuksen haasteina olivat ionien erilaiset varaukset, jolloin esimerkiksi positiivisesti varautunut ammoniumioni kiinnittyi negatiivisesti varautuneen adsorbentin pintaan hel-poiten. Toisaalta negatiivisesti varautuneet anionit fosfaatti ja nitraatti suosivat positiivi-sesti varautuneita adsorbentteja. Myös muiden ionin läsnäolo joko edisti tai esti adsorboitumista ja joissain tapauksissa pH:lla oli suuri merkitys prosessin onnistumiseen. Saatuja tuloksia tarkasteltiin tutkittujen ionien poistoprosenttien ja isotermimallinnuksien kautta unohtamatta muita esille tulleita seikkoja. Saatujen tulosten mukaan etenkin kalsinoitu hydrotalsiitti poisti fosfaattia ja nitraattia, mutta se ei mainittavasti toiminut ammoniumille. Ammoniumille sen sijaan toimi par-haiten zeoliitit ja bentoniitti, jotka vähensivät myös Yaran vesien ammoniumpitoisuutta. Ionien yhtäaikainen poistaminen oli haastavaa ja sen parempi ymmärtäminen edellyttää jatkotutkimuksia. Yksi jatkotutkimuskohde voisi olla eri adsorbenttien yhdistäminen keskenään, ja tästä saatiin jo alustavia, rohkaisevia tuloksia.

Treatment of Fe-containing Acid Mine Waters in Fixed Bed Adsorption Column with Calcite Side-Stone

The acid mining drainage is considered the most significant environmental pollution problem around the world for the extensive formation acidic leachates containing heavy metals. Adsorption is widely used methods in water treatment due to it easy operation and the availability of a wide variety of commercial adsorbent (low cost). The primary goal of this thesis was to investigate the efficiency of neutralizing agents, CaCO3 and CaSiO3, and metal adsorption materials with unmodified limestone from Company Nordkalk Oy. In addition to this, the side materials of limestone mining were tested for iron adsorption from acidic model solution. This study was executed at Lappeenranta University of Technology, Finland. The work utilised fixed-bed adsorption column as the main equipment and large fluidized column. Atomic absorption spectroscopy (AAS) and x-ray diffraction (XRD) was used to determine ferric removal and the composition of material respectively. The results suggest a high potential for the studied materials to be used a low cost adsorbents in acid mine drainage treatment. From the two studied adsorbents, the FS material was more suitable than the Gotland material. Based on the findings, it is recommended that further studies might include detailed analysis of Gotland materials.

Titanium dioxide based nanomaterials for photocatalytic water treatment

Water treatment using photocatalysis has gained extensive attention in recent years. Photocatalysis is promising technology from green chemistry point of view. The most widely studied and used photocatalyst for decomposition of pollutants in water under ultraviolet irradiation is TiO2 because it is not toxic, relatively cheap and highly active in various reactions. Within this thesis unmodified and modified TiO2 materials (powders and thin films) were prepared. Physico-chemical properties of photocatalytic materials were characterized with UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), ellipsometry, time-of-flight secondary ion mass spectrometry (ToF-SIMS), Raman spectroscopy, goniometry, diffuse reflectance measurements, thermogravimetric analysis (TGA) and nitrogen adsorption/desorption. Photocatalytic activity of prepared samples in aqueous environment was tested using model compounds such as phenol, formic acid and metazachlor. Also purification of real pulp and paper wastewater effluent was studied. Concentration of chosen pollutants was measured with high pressure liquid chromatography (HPLC). Mineralization and oxidation of organic contaminants were monitored with total organic carbon (TOC) and chemical oxygen demand (COD) analysis. Titanium dioxide powders prepared via sol-gel method and doped with dysprosium and praseodymium were photocatalytically active for decomposition of metazachlor. The highest degradation rate of metazachlor was observed when Pr-TiO2 treated at 450ºC (8h) was used. The photocatalytic LED-based treatment of wastewater effluent from plywood mill using commercially available TiO2 was demonstrated to be promising post-treatment method (72% of COD and 60% of TOC was decreased after 60 min of irradiation). The TiO2 coatings prepared by atomic layer deposition technique on aluminium foam were photocatalytically active for degradation of formic and phenol, however suppression of activity was observed. Photocatalytic activity of TiO2/SiO2 films doped with gold bipyramid-like nanoparticles was about two times higher than reference, which was not the case when gold nanospheres were used.