Influence of compositions of sodium nitrite waste liquids containing Cs⁺ on geopolymer waste-form’s mineral-phases under hydrothermally-sintered process

Sodium salt waste (SSW) liquid containing Cs-137 is characterized by complex chemical compositions. Based on the content variation of Cs⁺, NaNO₂ and NaOH in a simulated SSW liquid, the influence of SSW compositions on the structures of geopolymer waste-forms (GWF) was investigated. Especially, the immobilization of SSW liquid easily led to residual sodium salts and deteriorate the properties of GWF. Therefore, a hydrothermally-sintered hybrid process was exploited to remove residual salts to improve GWF’s mechanical properties and the ability to immobilize Cs⁺. The process also reduced the volatilization of Cs⁺ during sintering due to the presence of pollucite in GWF.