Na_2O-CaO-Al_2O_3-SiO_2-H_2O系水化物凝胶对Cs~+的吸附机理

在35℃恒温水化反应90d条件下,制备了Na2O-CaO-Al2O3-SiO2-H2O系水化物凝胶,探讨了水化物凝胶的化学组成对Cs+吸附性能的影响;讨论了水化物凝胶对Cs+的吸附热力学行为。结果表明,当化学组成为n(CaO+Na2O)/n(SiO2+Al2O3)=0.66,n(Al2O3)/n(SiO2)=0.3时,凝胶对Cs+的3d吸附量可达10.6936mg/g;温度越低,吸附量越大,凝胶对Cs+的吸附近似服从Freudlich、Langmuir和D-R吸附等温式,反应为放热反应,且以离子交换吸附为主;吉布斯自由能和吸附熵为均为负值,反应能自发进行。吸附动力学符合Lagergren假二级速率方程模型。

Adsorption Mechanism of Cs+ in Hydration Products Gel from NazO-CaO-Al2O3-SiO2-H2O System

The adsorption mechanism of Cs+ in hydration products gel from Na2O-CaO-Al2O3-SiO2-H2O system was studied. The hydration products gel were synthesized at 35 ℃ for 90 d. The influence of material compositions on adsorption capacity of Cs+ was discussed. The adsorption thermodynamics of Cs+ in hydration products gel were investigated. The results showed that the adsorption capacity of Cs+ was 10.693 6 mg/g in hydration products gel which chemical composition was n(CaO+Na2O)/n(SiO2+Al2O3)= 0.66, n(Al2O3)/n(SiO2) = 0.3 after 3 d. The adsorption capacity of Cs+ in hydration products gel increased with the decrease of temperature. The adsorption isothermal curve of Cs+ in hydration products gel was approximately in conformity to Freudlich,Longmuir and D-R formula,adsorption processes appeared to be exothermic and controlled by the ion exchange. The negative Gibbs values implied that adsorption reaction was a spontaneous process. The entropy change was found to be negative. The adsorp-tion kinetics of Cs+ in hydration products gel was found to follow Lagergren pseudo second-order dynamic equation.