Abstract
In this study, the potential use of waste diatomaceous earth from the production of diatomaceous earth for filtration purposes, as an alternative raw material for foam glass production, was explored. The chemical and mineralogical composition and the high temperature behavior of waste diatomite were studied to assess its suitability for foam glass production. Glass-ceramic foams were prepared using NaOH solution as a foaming agent, via a hydrate mechanism. The influence of different pretreatments and firing temperatures on the foam’s structure, bulk density and compressive strength was investigated. High temperature behavior was studied using TG/DTA analysis and high temperature microscopy. Phase composition was studied using X-ray diffraction analysis. Glass-ceramic foam samples of a high porosity comparable to conventional foam glass products were fabricated. The pretreatment temperature, foaming temperature and sintering holding time were found to have a significant influence on foam properties. With increased pretreatment temperature, pyrogenic carbon from the thermal decomposition of organic matter contained in the raw material acted as an additional foaming agent and remained partially unoxidized in prepared foams. The bulk densities of prepared samples ranged from 150 kg/m3 to 510 kg/m3 and their compressive strengths were between 140 and 1270 kPa.
Highlights
Foam glass is an inorganic thermal insulation material which was first introduced in the 1920s
This study explores the potential of solid waste generated during centrifugal classification and filter pressing, during filter diatomaceous earth production
Results temperature microscopy measurement of raw raw diatomite diatomite and and didiResults of the high temperature microscopy measurement measurement of of raw diatomite and diatomite mixed with solution are depicted in Figure as an 0 area change of the atomite mixed with solution are depicted in Figure as an area change of 0 change of the atomite mixed with NaOH solution are depicted in Figure 4 as an A/A0 area sample silhouette
Summary
Foam glass is an inorganic thermal insulation material which was first introduced in the 1920s. Mass production of foam glass for thermal insulation purposes is conducted exclusively using a powder sintering method due to its lower energy consumption and higher production capacity compared to other methods of porous glass preparation, such as direct melt foaming, sol-gel processes, high-pressure physical foaming or leaching of phase separated glasses. In this process, waste glass cullet or specially prepared and finely milled glass powder and a suitable foaming agent, are mixed and heated in a furnace [1]. The porous structure is fixed via rapid cooling and the resulting foams are either annealed and slowly cooled to allow for dissipation of stress in the case of foam glass blocks, or rapidly cooled to room temperature to cause the cracking and disintegration of the material to produce lightweight foam glass aggregate [1,2,3,4].
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