**3. The Results and Their Discussion**

*3.1. Mineral Wool Leachability Test Results*

Table 4 shows the leachability levels of harmful substances that may become an environmental hazard. The analysed mineral wool was slightly alkaline and had a relatively high leachability of chlorides and sulphates.

**Table 4.** Leachability of harmful substances and heavy metals from the tested mineral wool, expressed in mg/kg dry weight (except for pH).


Since the following values are exceeded: chloride (in both types of wool), sulphates (in glass wool), barium (in glass wool) and cadmium (in rock wool), it can be said that mineral wool does not qualify for storage at a landfill for inert waste. However, the situation is different in the case of non-hazardous and inert waste, which is not municipal waste. Based on the results, it can be concluded that the values obtained using the primary test for Rock wool (the ratio of liquid to solids equal: 10 L/kg) did not exceed the permissible leaching limits. Thus, rock wool can be stored in a landfill for non-hazardous and inert waste. On the other hand, too much barium in a tested sample of glass wool discriminates against it for storage in this landfill. Therefore, in this case, it must be deposited in a hazardous waste landfill to ensure that all results do not exceed the leaching limit values. As a curiosity in the use of waste mineral wool, the effect of using the addition of mineral wool can be cited from crops under cover and municipal sewage sludge on water retention and heavy metals. The average soil's leaching efficiency (Pb, Zn and Cd) was assessed. Sewage and mineral sludge Wool, widely used in many soil remediation technologies, has been found to have a beneficial and diversified influence on soil water properties and the mobility of heavy metals [56].

Table 5 presents the parameters considered as additional criteria allowing waste to be stored in non-hazardous and inert landfills. Again, a much more significant loss on ignition of glass wool relative to rock wool can be seen. On the other hand, the opposite situation occurs in the case of organic carbon, where rock wool has a much more significant amount (Rock wool contains more organic compounds than glass wool). Therefore, both glass wool and rock wool meet the requirements for waste destined for storage in landfills other than neutral and hazardous.

**Table 5.** Chemical properties of mineral wool that allow for depositing in landfills for non-hazardous and inert waste.


Determination of the ignition loss at 950 ◦C is an essential parameter for waste in construction. In addition, it is a fire safety parameter. Loss on ignition at 950 ◦C temperature for rock wool was at a loss of 4.59%, while it was at 7.88% for glass wool. The rock wool mineral residue had a loose consistency, and it can be stated that it was like sand (Figure 4a). On the other hand, glass wool at the temperature of 950 ◦C had a liquid consistency; it underwent vitrification (Figure 7b).

**Figure 7.** Residue from Loss on Ignition (LOI) at 950 ◦C, (**a**) rock wool, (**b**) glass wool; wool residue after thermal analysis at 815 ◦C without oxygen, (**c**) rock, (**d**) glass.

As part of the research, the content of volatile elements was determined. The volatile element content for Rock wool was at the level of 3.74%, while about 5.82% for glass wool. When analysing the samples after denoting, carbonisation of the samples was observed (Figure 4c,d). The conducted analyst in thermal transformation confirmed that the material is non-flammable rock wool is characterised by a higher leachability of selected elements than glass wool.

Only the content of phosphorus was higher for glass wool. The difference can be seen in the lithium content, almost 17 times higher in rock wool (Table 6). All the results met the required conditions regarding the acceptable limit values for waste intended to be stored in landfills.


**Table 6.** Leachability of selected elements (mg/L) from the tested waste.
