| Ammonium molybdophosphate(AMP),the ammonium of heteropoly acid,is a kind of ammonium possessing high selectivity and high ion exchange capacity for 137 Cs.It is a good thermal stability and difficult to dissolve in strong acid environment.However,AMP is a very fine powder(0.5-6 μm),and its hydraulic performance is very poor,so can not be directly used for column operation.The compound of inorganic ion exchanger(SM-AMP20,20 wt% AMP)aiming at improving the performance of AMP was fabricated by the porous silica matrix synthesized.The static/dynamic adsorption properties and adsorption behavior of Cs+ on SM-AMP20 in simulated waste liquid were studied.Furthermore,the regeneration performance of SM-AMP20 was analyzed by the process of adsorption-desorption-adsorption,and the 137 Cs adsorption on SM-AMP20 in the low-level radioactive waste liquid that could provide data support for the engineering application was investigated.A new type of porous silica matrix was synthesized by using a “polymer template method”-“sequential annealing mechanism” viewing polyvinyl alcohol(PVA)and tetraethyl orthosilioate(TEOS)as the raw material s in acid condition,and SEM-EDS,FTIR,BET and other methods were used to characterize the structure of the composite matrix.The images of SEM-EDS showed that the hybridization of the PVA/TEOS composite matrix formed a specific network and porous structure.The analysis of BET revealed that its specific surface area was 60.53 m2/g.The Si-O-C covalent bond could be created by dehydration or transesterification between the hydroxyl group of silanol group from TEOS and PVA using FTIR.In addition,SEM-EDS,XRD,TEM,FTIR,TG-DTA and other methods were used to characterize the structure of the SM-AMP20 by “sequential annealing mechanism”-gel coprecipitation method.The results proved that the microcrystalline particles of AMP were loaded on the surface of porous silica matrix or inside the pore.The addition of porous silica matrix composite did not change the crystal properties and thermal stability of AMP.In summary,the novel method of “polymer template method”-“sequential annealing mechanism”-gel coprecipitation could be applied to the rapid preparation of porous inorganic ion exchanger-SM-AMP20.The effects of Cs+ adsorption properties on SM-AMP20 at different reaction time,initial Cs+ concentration,and solution acidity were studied by static adsorption experiments.The static saturated adsorption time tsat of SM-AMP20(neutral p H value,0.1 mol/L Cs+)for Cs+ was about 4 h,and the equilibrium adsorption capacity qe was 37.63 mg/g.The adsorption process was in accord with the pseudo first order kinetic model(R2 >0.99)and Langmuir isotherm adsorption model(R2 >0.98).The distribution coefficient Kd of SM-AMP20 in the HNO3 solution concentration of 0.001-3 mol/L was basically unchanged,which showed a good acid resistance.Dynamic adsorption experiments were carried out to study the adsorption behavior of SM-AMP20 at different Cs+ inlet concentration,inlet flow velocity of Q,column height of Z and the presence of coexisting ions.2.5 m L/min of Q,11 cm of Z,and 10 mg/L Cs+ solution in neutral p H,the breakthrough time of tbre was up to 26 h.The less of Q or more of Z,the longer of tbre and saturation time t?sat,the removal rate of Cs+ could reach 94.63 %(0.8 m L/min of Q,11 cm of Z).51.20 g/L Na+,16.50 g/L Al3+,17.40 g/L Fe3+ and 8.20 g/L Ni2+ coexisted with 1000 mg/L Cs+,and the adsorption capacity q0 for Cs+ on SM-AMP20 were 8.11,13.87,13.59 and 12.83 mg/g,respectively.It showed that the extraction and separation of SM-AMP20 for Cs+ had a relatively high selectivity.The q0 of Cs+ in simulated high level liquid waste(SHLLW)was 5.988 mg/g,and in accord with Thomas,Yoon-Nelson,Adamas-Bohart,BDST and other column dynamic models(R2 >0.99).The competitive adsorption experiments of Cs+ on SM-AMP20 with different NH4+ concentrations and regeneration after adsorption Cs+ were investigated.It determined that the 2-3 mol/L NH4NO3 solution was a good desorption agent for SM-AMP20.The recovery of Cs+ was 104.8~111.7 % in the three times of adsorption-desorption experiments,and the regenerated SM-AMP20 could still keep its good adsorption performance(q0,5.99~6.88 mg/g).The effect of 137 Cs static adsorption on SM-AMP20 in the low-level radioactive waste liquid was investigated.The static adsorption capacity(solid/liquid ratio of 1:200 g/m L)of 137 Cs on SM-AMP20 20 wt% AMP of was relatively significant(0.84?103 Bq/g)and the adsorption rate was 55.36 %(solid/liquid ratio of 1:50 g/m L). |
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