ИСТИНА

Stone wool fibers are amorphous aluminosilicate glassy material which is widely used in many industrial and construction applications for heat and fire insulation, fillers, filters and horticultural growth media. The chemical stability and biosolubility of stone wool glass depend on its resistance to dissolution, which is related to the properties of the glass fiber surface. The ability of the surface to react might also depend on the properties of the surface –OH groups, their concentration, pK a and ability to bind ligands from the aqueous media. Surface complexation modelling has been used for decades to describe and predict the dissolution behavior of minerals, including aluminosilicates, such as ligand-promoted dissolution of anorthite [1], pH-promoted dissolution of kaolinite [2] and montmorillonite [3] and many others. Following Stumm et al., [4], the dissolution rate of mineral, R diss , can be described as a function of surface protonation and the amount of adsorbed ligand: R diss = f ( [>XOH2+]^m + [>XO-]^n + [>XLH],[>XL-], …) In this work, we applied a similar approach to describe the dissolution rate of amorphous stone wool fibers in the pH range from 3 to 12 and citrate concentration ranging from 0 – 0.5 mM, used as a ligand. First, the dissolution rates were measured in flow-through dissolution tests, using high fluid flow-to-solid surface area (F/A) ratio. This allowed us to obtain dissolution rates that are least affected by solution feedback through accumulation of dissolved species. Then, we performed acid-base titrations of fiber suspensions, where we monitored concentration of leached elements and citrate adsorption, followed by calculating the distribution of surface proton and citrate complexes using FITEQL program. The obtained distribution of surface complexes over pH/citrate concentration was used to describe the dissolution rates in the flow-through experiments. Our results demonstrated that modelling allowed differentiation between surface silanols, >SiOH and aluminols, >AlOH, present on the stone wool surface and thus potentially, to describe the dissolution of different stone wool samples with a range of Al/Si ratio. Further work will aim at applying surface complexation modelling for predicting dissolution behavior of amorphous glassy stone wool fibers under batch (static) dissolution conditions.