New articles published: V. 14 n. 2 (2026)

Use of geopolymer for cesium sorption

Abstract: The sand extraction plays a crucial role in economic development and the construction industry. However, the fine waste generated during the extraction process brings environmental impacts on this activity. In order to promote the reuse of this waste, the synthesis of geopolymers was proposed. Geopolymers are a class of inorganic materials composed of aluminosilicates arranged in a three-dimensional network, originally developed by Joseph Davidovits in 1978. These are silica–alumina materials with an amorphous to semi-crystalline three-dimensional structure, obtained through alkaline activation. The raw materials used for their synthesis can consist of natural sources of aluminosilicates or by-products from industrial processes, which react through an alkaline activation route, generally using sodium or potassium hydroxide and silicate solutions as activating agents. These materials can be applied in the treatment of liquid radioactive waste through the sorption of cesium, which is commonly present in such waste. The study involved the characterization of mining waste, including quantitative (mineralogical) and qualitative (degree of amorphization) analyses, followed by the synthesis of the geopolymer. After 28 days of curing, the material was ground in a jaw mill and further reduced in a pulverizing mill. Cesium sorption tests with the prepared material were then carried out. The ground geopolymer was characterized by FTIR (Fourier Transform Infrared Spectroscopy), XRD (X-ray Diffraction), XRF (X-ray Fluorescence), particle size analysis, and BET surface area measurement. Cesium sorption tests (using inactive CsCl) were performed using the batch equilibrium method, as described in the EPA Method 530. The results demonstrated that the grinding process was effective in adjusting grain size, enhancing the material’s surface area. Mineralogical characterization confirmed the presence of aluminosilicates such as kaolinite and muscovite, which have favorable sorption properties. Thermal analysis identified the temperature range at which the material reaches a stable chemical composition, as well as the regions associated with dehydration and dihydroxylation. The tests indicated that the geopolymer obtained from sand extraction waste showed high cesium sorption potential, as evidenced by the sorption isotherm results. Read full article.