blast furnace slag, stability, leaching, stabilization, demineralized water

Blast furnace slag represents waste product from the metallurgy which is commonly utilized in the construction industry as well as it is studied in the form of fine particles as potential material for removal of heavy metals ions from solutions. Milled blast furnace slag causes significant increase of the pH value of the suspension in the contact with demineralized water as well as soluble silicates (mainly due to hydrolysis), Ca(II) and Mg(II) ions are released to the solution. The reaction of CaO present in the material takes place in the early stages of contact with water, mainly Ca(II) ions are released to the solution. Hydrolysis and silicates release take place mainly after 24 hours of contact time. Equilibrium isreached after 7 days of contact. The ratio slag mass:water volume has negligible influence on the final pH value of the solution after contact but the amounts of released components (soluble SiO2, Ca(II) and Mg(II)) increase with increasing amount of water towards the constant mass of slag. Particle size has significant influence on the interaction of slag with demineralized water. The change of pH value as well as amount of released species increase with decreasing particle size. Only slight interaction between slag and water occurs for particles >0.5 mm, thus it can be stated that the material is relatively stable. Milling of slag to the form of fine particles (<0.5 mm) leads to the strong interaction with water, significant changes of solution pH values and release of the high amount of soluble SiO2 and Ca(II) ions were observed. Temperature has significant influence on the interaction of slag with water as well. Temperature influences mainly the hydrolysis of silicates. The released amounts of soluble SiO2 and Ca(II) ions increase significantly with increasing temperature kept during contact. Interactions of phases containing Mg(II) are not influenced by temperature. Finely milled blast furnace slag can be stabilized by addition of Al2O3 and su