Production of vitreous materials from mineral coal bottom ash to minimize the pollution resulting from the waste generated by the thermoelectrical industry

Abstract

Mineral coal bottom ash exerts a great impact on the environment due to the presence of heavy metals in its composition and the lack of an adequate area for disposal. Vitreous materials were synthesized from bottom ash to be employed as a by-product. The bottom ash was subjected to an X-ray fluorescence (XRF) analysis to evaluate the oxide composition present in the material. To study the effect of bottom ash in the attainment of glass, a simplex lattice design for experiments with blends was employed. The elements considered in the design were: bottom ash; sodium carbonate (Na2CO3) and calcium oxide (CaO), both used as melting agents; magnesium oxide (MgO), which was used as a stabilizer for the vitreous network. For the characterization of the glasses, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectrometry (FTIR) were carried out. Ten different formulations were tested. The results indicated that two out of the ten formulations formed a crystalline phase, which is undesirable for a vitreous material. In the statistical analyses, the Pareto Diagram and the response surface showed that the glass transition and softening temperatures were strongly influenced by the level of calcium oxide and magnesium oxide, as well as that of bottom ash, resulting in an increase in the softening and glass transition temperatures.