Hanna Kyllönen

Experimental Aspects of Scaling Control in Membrane Filtration of Mine Water

This study focused on membrane filtration of neutralized pond water, which may be necessary when good quality water is required for hydrometallurgical processes. Neutralized mine water can still have fairly high metal and sulphate levels, which can hinder discharge and reuse possibilities. Both nanofiltration and reverse osmosis are effective in removing metals and sulphate, but scaling can be a severe problem. Microfiltration as a pre-treatment method, although meant for particle removal, seemed to decrease the amount of scalants, thus delayed scaling on the membrane surface and increasing water recovery for both nanofiltration and reverse osmosis. It is possible that the presence of particles in the feed water promoted crystal growth in the turbulent flow and caused the removal of dissolved constituents. Alternatively, supersaturation could have occurred, allowing microfiltration to remove the scalants as particles. The Liqum sensor indicated that redox values started to increase again just before scaling began due to precipitation in the supersaturated membrane concentrate solution. Thus, the sensor seemed to provide real time, in-situ, early-stage scaling warning.ZusammenfassungDiese Studie untersucht die Membranfiltration von neutralisiertem Wasser, welche notwendig ist, um eine gute Wasserqualität für hydrometallurgische Prozesse zur Verfügung zu stellen. Auch neutralisiertes Grubenwasser kann hohe Metall- und Sulfatkonzentrationen enthalten, welche die Ausleitung und Wiederverwendungsmöglichkeiten einschränken. Sowohl die Nanofiltration als auch die Umkehrosmose sind effektive Verfahren zur Entfernung von Metallen und Sulfat. Aber die Krustenbildung stellt dabei ein ernstes Problem dar. Mikrofiltration als eine Vorreinigungsstufe, eigentlich zur Partikelentfernung gedacht, scheint die Menge der Krustenbildner zu verringern und somit die Krustenbildung an der Membranoberfläche, sowohl bei der Nanofiltration als auch beider Umkehrosmose, zu verzögern. Es ist möglich, dass das Vorhandensein von Partikeln im Zuflusswasser das Kristallwachstum in den turbulenten Strömen fördert und die Entfernung gelöster Bestandteile verursacht. Alternativ könnte bei der Mikrofiltration eine Übersättigung aufgetreten sein, welche die Entfernung von Krustenbildnern als Partikel zur Folge hat. Der Liqum Sensor zeigte an, dass kurz vor der Krustenbildung, die Redoxwerte durch die Ausfällung in der übersättigten Membranlösung stiegen. Somit scheint der Sensor eine in-situ-Echtzeitwarnung zu liefern.ResumenEste estudio se enfocó sobre la filtración por membrana de agua neutralizada que podría ser necesario cuando se requiere agua de buena calidad para procesos hidrometalúrgicos. El agua de mina neutralizada aún puede contener relativamente altos niveles de metales y sulfatos que pueden complicar su descarga y sus posibilidades de uso. La nanofiltración y la ósmosis inversa son efectivas en remover metales y sulfatos pero la precipitación de especies inorgánicas puede ser un serio problema. La microfiltración como un método de pretratamiento, aunque es válido para la remoción de partículas, parece disminuir la cantidad de incrustaciones, postergando así la precipitación de especies inorgánicas sobre la superficie de la membrana e incrementando la recuperación de agua tanto en nanofiltración como en ósmosis inversa. Es posible que la presencia de partículas en el agua de alimentación promueva el crecimiento de cristales en el flujo turbulento y cause la precipitación de los constituyentes disueltos. Alternativamente, podría haber ocurrido una supersaturación que remueva a los incrustantes como partículas. El sensor Liqum indicó que los valores redox comenzaban a crecer de nuevo justo antes que la incrustación comenzara debido a la precipitación en la solución supersaturada. Así, el sensor parece proveer una alarma temprana, in situ y en tiempo real, de generación de incrustaciones.水泥窑粉尘去除酸性废水金属离子机理

Sulphate removal from mine water with chemical, biological and membrane technologies

Chemical, physical and biological technologies for removal of sulphate from mine tailings pond water (8 g SO42-/L) were investigated. Sulphate concentrations of approximately 1,400, 700, 350 and 20 mg/L were obtained using gypsum precipitation, and ettringite precipitation, biological sulphate reduction or reverse osmosis (RO) after gypsum pre-treatment, respectively. Gypsum precipitation can be widely utilized as a pre-treatment method, as was shown in this study. Clearly the lowest sulphate concentrations were obtained using RO. However, RO cannot be the only water purification technology, because the concentrate needs to be treated. There would be advantages using biological sulphate reduction, when elemental sulphur could be produced as a sellable end product. Reagent and energy costs for 200 m3/h tailings pond water feed based on laboratory studies and process modelling were 1.1, 3.1, 1.2 and 2.7 MEur/year for gypsum precipitation, ettringite precipitation, RO and biological treatment after gypsum precipitation, respectively. The most appropriate technology or combination of technologies should be selected for every industrial site case by case.

TEMPERATURE SENSITIVE FUNCTIONALISED FILTER CLOTHS TO ENHANCE FILTER

. The stimuli-responsive polymers reviewed in this paper are able to change their volume by shrinking or swelling, and hydrophobicity/hydrophilicity balance as a function of temperature. The so-called Lower Critical Solution Temperature (LCST), where these thermo-responsive transitions happen, may be adjusted, for instance, by using different kinds of monomers or by copolymerizing different kinds of monomers together. Crosslinking agents are often used to adjust their structural and mechanical properties. Cellulose and hemicelluloses has also been used as starting compounds for stimuli-responsive materials or cellulose based membranes grafted with copolymer. They could be expected to have a potential application in drug release system, adsorption materials and functional filtration materials. This extremely interesting and growing research topic of stimuli-responsive materials is also very well reported in some articles, for example, published by Tomisic et al. 2012, Hao et al. 2009, Pan et al. 2010, Wandera et al. 2010 and Liu et al. 2010.