Development of groundwater treatment method using radiation-induced graft polymerization adsorbent at the Mizunami Underground Research Laboratory. Annual report on 2007 fiscal year (Joint research)

The concentrations of fluorine (7.2-10mg/L) and boron (0.8-1.5mg/L) dissolved in groundwater pumped from shafts during excavation at the Mizunami Underground Research Laboratory (MIU), Tono Geoscience Centre, must be reduced to the levels below the environmental standards (fluorine:0.8mg/L, boron:1mg/L). Coagulation treatment and ion exchange treatment are applied for fluorine and boron at a current water treatment facility in MIU, respectively. A collaborative research on groundwater treatment for fluorine and boron was started by the Environment and Industrial Materials Research Division, Quantum Beam Science Directorate and the Tono Geoscientific Research Unit, Geological Isolation Research and Development Directorate in 2006. This is because the Quantum Beam Science Directorate has synthesized fibrous adsorbents with radiation-induced graft polymerization and applied them to collect rare metals dissolved in hot springs and sea water. Boron adsorbent synthesized by grafting showed higher removal rate than that of the ion-exchange resin. Additionally, the durability and the repetitive use of the boron adsorbent were evaluated to estimate the capacity of the boron adsorption. Therefore we produced a test equipment to do scale-up test of the adsorbent. Effects of flow rate and the repetitive use on the adsorption capacity of boron were investigated. As a result, it concluded that the adsorption capacity of the boron adsorbent did not change even when the flow rate increased from SV 50h-1 to 100h-1. In addition, enough durability was confirmed for the repetitive use of the adsorbent. The adsorption capacity of the adsorbent was affected by pH of the groundwater especially in high alkaline range above a pH of 10. (author)