Immobilization of strontium and cesium by aluminosilicate ceramics derived from metakaolin geopolymer-zeolite A composites via 1100 °C heating treatment

Abstract

In this work, K-based metakaolin geopolymer-zeolite A composites doped with strontium and cesium radionuclides have been subjected to 1100 °C to prepare aluminosilicate ceramic waste forms. Serial analysis of mineral characterization, physical properties and leaching resistance have been adopted to investigate the immobilization performance of aluminosilicate ceramic waste forms for strontium and cesium radionuclides. Compared to geopolymer-zeolite A composites, the obtained ceramic waste forms exhibit preferable mechanical property and leaching resistance (in deionized water, brine solutions and silicate solutions). The compressive strengths of aluminosilicate ceramic waste forms (Sr/Cs-loaded matrix) are both above 80 MPa, which are far higher than that of geopolymer-zeolite composites solidification matrices. Owing to the viscous sintering under 1100 °C heating treatment, even compact and dense ceramic waste forms have been successfully synthesized, accompanied by the main crystalline phase transformation in monoliths from zeolite A to leucite. Cs-leucite and Sr-feldspar also have been detected by XRD and TEM analyses, which are conducive to capturing strontium and cesium radionuclides in ceramic monoliths. All findings have proven that the ceramics waste forms derived from metakaolin geopolymer-zeolite A composites could be an ideal option for nuclear wastes immobilization.