Geopolymerization as a Method of Stabilizing and Solidifying Hazardous Waste

The development of civilization is causing an increase in the amount of industrial waste, especially hazardous waste associated with the production and manufacture of metals, which pose a threat to the environment. Among the methods of utilization of this type of waste, the methods of stabilization and solidification deserve attention, which enable the transformation of hazardous waste and the heavy metals it contains into an environmentally safe form, i.e., immobilized. This paper proposes a method to stabilize and solidify galvanic sewage sludge using geopolymerization. The surface morphology was studied, and the chemical composition was analyzed using the SEM–EDS method. The presence of characteristic functional groups on the surface of the galvanic sludge and the geopolymer obtained on its basis was determined by FTIR spectroscopic analysis. Moreover, we evaluated the release of selected heavy metals (Cu, Mn, Pb, and Zn) were performed on the basis of leaching tests under static and dynamic conditions. Additionally, a sequential extraction method was used according to the procedure proposed by Tessier. It was found that, as a consequence of geopolymerization of galvanic sludge, this hazardous waste is transformed in such a way that the heavy metals it contains, which occur in the form of soluble compounds, are not leached but immobilized. In relation to the metals analyzed, the reduction in solubility and the decrease in leaching were obtained at a practical level of 100% for Zn and Mn, for the remaining metals, respectively, 94% for Cu and in the range of 40–90% for Pb. Analysis of the FTIR spectra showed that the ions of the metals studied were permanently immobilized in the aluminosilicate structure of the geopolymers obtained. This shows that galvanic sewage sludge is chemically transformed into inert waste that can be deposited in landfills. Transformed waste can also be used in the economy as building material because geopolymerization improves the physical properties of the waste, namely increases its mechanical strength. The proposed hazardous waste disposal process is safe for the environment and is consistent with the idea of sustainable development.