Calculation of viscosity–temperature curves for glass obtained from four wastewater treatment plants in Egypt

Abstract

This article establishes the relationship between the chemical composition, temperature and viscosity of glasses obtained from the four sludge treatment plants of urban and industrial wastewater from the Nile Delta in Egypt. In order to determine the working conditions of these glasses and their growth temperature, different techniques have been used: differential thermal analysis, hot stage microscopy and dilatometry. We used a prototype of hot stage microscopy, with the help of an image analysis programme developed in the present study. The chemical composition of major oxides sludge ranging from: SiO2 (36–48 wt%), Al2O3 (9–16 wt%), CaO (5–25 wt%), P2O5 (1.5–11 wt%), and Fe2O3 (~9 wt%), this composition is close to a basalt rock, being necessary to incorporate some raw materials to adjust it to the basalt rock that has a good viscosity-temperature curve. The glass transition temperatures of the four glasses obtained vary between 650 and 725 °C and the growth occurs between 938 and 1,033 °C. We also obtained the viscosity–temperature curves with the aid of the hot stage microscopy that has allowed us to determine the working temperatures of the four glasses, ranging from 926 to 1,419 °C, depending on the type of forming process used.