Interaction and stabilization of organic radioactive waste in geopolymer

Research Project

Project/Area Number	21K04207
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 22010:Civil engineering material, execution and construction management-related
Research Institution	Hokkaido University
Principal Investigator	Y Elakneswaran 北海道大学, 工学研究院, 准教授 (60769090)
Project Period (FY)	2021-04-01 – 2024-03-31
Project Status	Granted (Fiscal Year 2022)
Budget Amount *help	¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000) Fiscal Year 2023: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000) Fiscal Year 2022: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000) Fiscal Year 2021: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Keywords	Cement chemistry / Geopolymer / Radioactive waste / Oil / Modelling
Outline of Research at the Start	Aim of this research project is to propose geopolymer for solidification and stabilisation of the liquid organic radioactive waste. Initially, the surface chemistry of polymers and minerals will be studied to understand the interaction between the organic compound and inorganic geopolymer. The characteristics of geopolymers and oil-in-water emulsion will be used to select the most appropriate geopolymer. The properties and the long-term durability performance of geopolymer-organic composites will be evaluated through various experimental techniques and modelling approaches.
Outline of Annual Research Achievements	This year research work focused on solidifying organic compounds in geopolymer. Metakaolin (MK) from Sobueclay, Japan, potassium silicate alkali activated solution (AAS), and lubricant oil from ENEOS FBK turbine 32 were used to prepare the geopolymer-oil composite (GPOIL). The AAS was prepared by mixing the potassium silicate (originally containing 29.1 wt.% SiO2, 21.9 wt.% K2O, 49.0 wt.% H2O), potassium hydroxide, and purified water. The alkaline solutions synthesising the geopolymer samples are defined as K2O: SiO2: H2O (molar ratio) 1:1:13. AAS was mixed with oil (0-50% by volume) for 5 min at 10,000 rpm to produce an emulsion. CetylTrimethylAmonium Bromide (CTAB) cationic surfactant was used, which was mixed with AAS and oil (1 g of surfactant for 100 mL of AAS). The prepared geopolymer-oil composite was cured at 20 C and RH 99% for 7 and 28 days. The metakaolin-based geopolymer could not solidify the oil. However, the geopolymer can successfully solidify oil content with the help of a surfactant that changes the surface of the oil from negative to positive, allowing it to interact with the opposing surface of the geopolymer. The compression strength test was conducted on GPOIL-surfactant with oil content from 0% to 50%. As the oil content increased, the compressive strength of the composite decreased due to increment of porosity induced by the presence of oil. This can be attributed to the fact that as the oil content and porosity increased, the number of effective bonding points decreased, resulting in a decrease in strength.
Current Status of Research Progress	Current Status of Research Progress 2: Research has progressed on the whole more than it was originally planned. Reason The research is going smoothly as proposed. I have achieved some important results and plan to present at a conference.
Strategy for Future Research Activity	FY 2023 WP 3: Properties and durability of geopolymer-organic composites Various experimental techniques will be used to evaluate the presence of organic phase in the geopolymerisation kinetics and to estimate the physicochemical and mechanical properties of the hardened composites. In addition, the leaching performance of the composites in various exposure solutions will be examined.