Ovidiu Dumitrescu

Study on the Recycling of Borate Silicate Vitreous Waste with Capitalization of Heavy Metals Sludge

The paper follows both the national preservation and durable managing policy, as well as the European laws for the area of environmental protection (UE’s Directive 1999/31/EC – „landfill of waste” an the Council’s Directive no. 94/62/CE regarding the packaging and the packaging waste, amended by the Council’s Directive no. 2004/12/CE). The proposed technologies lead to reducing the need of both raw materials and energy in the process of obtaining various types of glass. The study proposes new ways of retrieving and eliminating waste that contains heavy metals alongside borosilicate shards. This paper also aims to increase the responsibility of the waste generating companies and to make the potential users more sensible.

Basicity-Gibbs Free Energy Relationships for Binary Alkali Silicates

In present paper there are presented such correlations for the silica-alkali systems (M2O – SiO2) where reliable thermodynamic data exists from the thermal equilibrium diagrams. It was observed that with the saturation of SiO2 tetrahedron with metal ions, the difference in basicity between the reactants is diminished, in the order SiO2 → disilicate → metasilicate → orthosilicate, and that confirms the role of driving force for these reactions of the acid-base interaction between oxides and the intermediate silicates formed. Also, there were proposed some correlations between the standard formation Gibbs free energy, (Gº298), and basicity percentage, pB, for the binary compounds from the same oxide systems. Considering the fact that for a system at equilibrium, reaction constant Kp depends on the reaction free Gibbs energy (rG0 298) and temperature, a correlation between basicity difference through basicity percentage, pB, and rG0 298 is proposed.