Waste and Solar Energy: An Eco-Friendly Way for Glass Melting

Abstract

In this work, concentrated solar energy (CSE) was applied to an energy-intensive process such as the vitrification of waste with the aim of manufacturing glasses. Different types of waste were used as raw materials: a hazardous waste from the aluminum industry as aluminum source; two residues from the food industry (eggshell and mussel shell) and dolomite ore as calcium source; quartz sand was also employed as glass network former. The use of CSE allowed obtaining glasses in the SiO2-Al2O3-CaO system at exposure time as short as 15 min. The raw materials, their mixtures, and the resulting glasses were characterized by means of X-ray fluorescence, X-ray diffraction, and differential thermal analysis. The feasibility of combining a renewable energy, as solar energy and different waste for the manufacture of glasses, would highly contribute to circular economy and environmental sustainability.

Glass Lightweight Aggregates from Glass Cullet and Mining and Food Industry Carbonate Waste

“…The carbonate residues from the food industry (ES and MS) are composed mainly of calcium carbonate (CaCO 3 ) ( Figure 1 ). The X–ray diffractogram of the eggshell residue indicates the presence of calcite as the only crystalline phase, while the mussel shell waste is composed of a mixture of the polymorphs calcite and aragonite [ 46 , 49 ]. Their DTA curves show an endothermic drop from 700 to 750 °C, leading to a peak centered at approximately 935 °C, which corresponds to the decarbonation of CaCO 3 ( Figure 2 ).…”

“…Thus, the lowest values of both properties were obtained when mussel shell was used as an additive. This result can be attributed to the presence of aragonite, a calcite polymorph with prismatic crystals that can hinder the intimate link between the particles in the initial pressed pellets [ 46 ]. Most of the compositions (2.5–10%) prepared with CF waste from mining produced LWAs with excellent properties.…”