Browsing by Subject "tailings"

Wastewater produced by the mining industry can be very acidic and high in dissolved metals. If released to the environment, it initiates diverse issues some of which are increasing acidity and high heavy metal concentrations. Wastewater treatment is traditionally done by using manufactured chemicals which is neither environmentally nor economically sound. The use of industrial by-product geomaterials is a low-cost alternative wastewater treatment method as these materials are anyway produced in other industries. In wastewater treatment with geomaterials, the element removal mechanism is based on precipitation and surface adsorption which are highly pH dependent. In this study, acidic multimetal wastewater from Talvivaara was treated with three byproducts (steel slag, apatite mine tailings and Sachtofer PR) of Finnish industries. Waste water was incubated with geomaterials for 1, 7 and 21 days, then titrated to pH 7. Effect of geomaterials and time on waste water pH and base consumption required to increasing the pH, as well as on concentrations of iron, aluminum, nickel, zinc, manganese, sodium and sulfur were studied. Untreated wastewater pH decreased with time due to hydrolyses of metals. Oxidation of ferrous iron to ferric iron also seemed to contribute to acidification of wastewater. Thus the base consumption increased significantly with incubation time. Among the used solids, steel slag most efficiently increased pH and consequently decreased the consumed base. Steel slag also showed the best results in element removal. It removed all or significant amount of dissolved iron, aluminum, nickel, manganese and sulfur. Tailings and Sachtofer PR showed poor results regarding element concentration by releasing several elements to the solution.