The Coadsorptive Kinetics Of Strontium And Cesium In Red Soil In Southwest Of China

With the rapid development of nuclear technique large of radial waste has beenproduced inevitably. Radioactivity of nuclear waste menaces human and theirenvironment. A retired nuclear engineering produced some very low radioactive waste.This paper studied the adsorption capability of the soil of a primary election nuclearwaste disposal to Sr and Cs. The author established some adsorption kineticsequations and ascertained the adsorption capability of Sr and Cs in the soil. Theinfluence of Sr and Cs to each other was researched in this paper. All research is tomake sure the security of the nuclear waste repository.In this paper, the influence of Sr and Cs to each other was researched. Accordingto the red soil characteristics in some place of Southwest, the characteristics ofkinetics absorption of Sr and Cs in soil were studied by batch technique and columnmethod. According to the experimental results, the characteristics of migration andadsorption mechanism of Sr and Cs in soil can be determined. Meanwhile the placefor storing up the radial waste containing Sr and Cs can be selected. The researchresults are showed following.1. Sr and Cs contest against each other in the absorption of soil. When one partenters the soil, the absorption of the other will be restrained. In the absorption of Srand Cs, the ability of absorption of Cs is stronger than that of Sr. The transportcondition is opposite. When the absorption reached certain extent, the competitiveaction can make Sr desorbed from the absorption and make the transportconcentration higher than the concentration in the environment. It was named afterCoordination Effect.2. The saturation absorption capacities of Sr in soil were 8.90 mg/g, 10.36 mg/g,11.74 mg/g and 12.44 mg/g respectively with the value of pH of 4, 6, 8 and 10 bybatch technique when Sr:Cs=1:1(mole ratio). Some conclusions could be gained bycolumn method when Sr:Cs=1:1. The results indicated that the dynamic absorption capacities of Sr in soil increased with the increase of pH value, from 6.24 mg/g whenpH=4 to 9.78 mg/g when pH=10. The dynamic absorption capacities of Sr in soilincreased with the increase of the initial concentration of the shower solution, from8.90 mg/g when the shower solution contained Sr 8.76 mg/L and Cs 13.29 mg/L to21.43 mg/g when the shower solution contained Sr 43.80 mg/L and Cs 66.45 mg/L.The dynamic absorption capacities of Sr in soil increased with the increase of the flux,from 7.15 mg/g when the flux was 60 ml/h to 11.02 mg/g when flux was 240 ml/h.The dynamic absorption capacities of Sr in soil decreased with the increase of thesample soil granularities, from 10.22 mg/g when the soil is between 80-100granularities to 5.39 mg/g when the soil is between 20-40 granularities.3. The saturation absorption capacities of Cs in soil were 17.68 mg/g, 18.70 mg/g,20.16 mg/g and 21.24 mg/g respectively with the value of pH of 4, 6, 8 and 10 bybatch technique when Sr:Cs=1:1(mole ratio). The results indicated that the dynamicabsorption capacities of Cs in soil increased with the increase of pH value, from 7.31mg/g when pH=4 to 11.12 mg/g when pH=10. The dynamic absorption capacities ofCs in soil increased with the increase of the initial concentration of the showersolution, from 9.80 mg/g when the shower solution contained 8.76 mg/L Sr and 13.29mg/L Cs to 24.68 mg/g when the shower solution contained 43.80 mg/L Sr and 66.45mg/L Cs. The dynamic absorption capacities of Cs in soil increased with the increaseof the flux, from 8.78 mg/g when the flux was 60 ml/h to 14.09 mg/g when the fluxwas 240 ml/h. The dynamic absorption capacities of Cs in soil decreased with theincrease of the sample soil granularities, from 11.15 mg/g when the soil is between80-100 granularities to 6.51 mg/g when the soil is between 20-40 granularities.4. The Elovich equation, parabola equation, double constant equation andfirst-order equation were used to simulate the adsorption of Sr and Cs in red soil. Theresults indicated that Elovich equation(X=alnt+b) was the best dynamic model todescribe the adsorption of Sr and Cs in red soil.5. The regression equation is simulated between dynamic absorption capacitiesand pH value, initial concentration, flux and soil granularities. The linearity is good.The regression equation of the dynamic absorption capacities of Sr is Y=-0.7850X₁+0.1196X₃+0.007319X₄-6.8071X₅+0.4554X₆+10.0938. The regression equation ofthe dynamic absorption capacities of Cs is Y=1.0654X₁+0.0514X₃+0.0164X₄-3.0017X₅+0.9342X₆-10.4015.6. The main components of the red soil are montmorillonite, illite, quartz and feldspar by XRD. The percentage is 40 %, 19 %, 28 % and 13 % respectively.The minerals adsorbing Sr mainly are montmorillonite and feldspar.The mineralsadsorbing Cs mainly are montmorillonite, illite and feldspar. Chemical absorption isthe main way in the soil absorption.