M. P. Gorbacheva

Removal of 131I and 137Cs from aqueous and aqueous-organic solutions with porous polyvinyl formal

The removal of 131I and 137Cs from aqueous and aqueous-organic solutions with porous polyvinyl formal (PPVF) was studied. The degree of radionuclide removal from water with a PPVF sample is determined by the amount of water absorbed by the polymer and is not influenced by the concentration of salts in solution. Porous polyvinyl formal allows recovering 137Cs from aqueous-organic solutions with 70 to 99% efficiency.

Removal of 60Co and 137Cs from simulated NPP trap waters

The possibility of removing 60Co and 137Cs from simulated NPP trap waters by sorption and precipitation methods was examined. The use of layered double hydroxides (LDHs) of Mg and Nd, containing CO32− in the interlayer space, for removing 60Co from NPP trap waters is inefficient, especially in the presence of EDTA. After 2 h of contact of the solid and liquid phases, the degree of 60Co sorption does not exceed 12% at V/m = 500 mL g−1. Coprecipitation of 60Co with a complex precipitate of Fe3+ and triethylenediamine (CH2-CH2)3N2 from simulated NPP trap waters containing 0.03 M Co2+ allows ∼85% removal of the radionuclide. The 60CO coprecipitation with KFe[Fe(CN)6] from simulated NPP trap waters does not ensure its efficient removal. The degree of coprecipitation of 60CO with KFe[Fe(CN)6] varies from ∼55 to ∼85%. A procedure was suggested for removing 60Co and 137Cs from aqueous solutions by coprecipitation of the radionuclides with the solid phase of K+, Fe3+, and Ni2+ ferrocyanides formed by adding K4[Fe(CN)6], Fe(NO3)3, and Ni(NO3)2 in succession to the solution. The procedure ensures almost 100% removal of both radionuclides from simulated NPP trap waters.

Recovery of 131I and 137Cs from a solution simulating NPP trap waters

Sorption of 131I and 137Cs from a solution simulating NPP trap waters on various inorganic and organic sorbents was studied. The highest degree of 131I recovery (>99%) can be attained with Fizkhimin granulated sorbents based on coarsely porous silica gel containing Ag and Ni in 1: 4 ratio, with Kd for 131I exceeding 105 ml g−1 at V/m = 103 ml g−1 and contract time of the solid and liquid phases of 120 min. Elevation of the solution temperature to 40°C does not affect the degree of 131I and 137Cs recovery. The degree of 137Cs recovery in all the experiments did not exceed 35%. The degree of 131I recovery by coprecipitation with AgCl and Ag4[Fe(CN)6] was about ∼96% and only 65%, respectively.

Removal of 60Co and 137Cs from simulated NPP bottom residues on the solid phase of K+, Ni2+, and Fe3+ ferrocyanides

The possibility of simultaneous removal of 60Co and 137Cs from simulated NPP bottom residues by coprecipitation with the solid phase of K, Fe, and Ni ferrocyanides was examined. In coprecipitation of 60Co and 137Cs with the KFe[Fe(CN)6] solid phase, the degree of removal of the radionuclides from simulated bottom residue containing 300 g L−1 NaNO3 and 3.4 × 10−5 M EDTA does not exceed 80% for 60Co and 99% for 137Cs. The scheme based on coprecipitation of the radionuclides with the solid phase of K+, Fe3+, and Ni2+ ferrocyanides, formed by successive addition of K4[Fe(CN)6], Fe(NO3)3, and Ni(NO3)2 to the solution, ensures efficient removal of 60Co and 137Cs from simulated bottom residue containing simultaneously up to 400 g·L−1 NaNO3 and 3.4 × 10−5 M EDTA. The radionuclides are removed to more than 99%.

Coprecipitation of 60Co from aqueous solutions with solid phases of various coordination compounds

Coprecipitation of 60Co from aqueous solutions with solid phases of various coordination compounds was studied. Microamounts of 60Co do not noticeably coprecipitate with solid phases of [M(CE)]BPh4 (M = Na+, Cs+; CE = 12-crown-4, 15-crown-5, 18-crown-6) and of CsBPh4. 60Co can be efficiently removed from aqueous solutions containing 0.1 and 4.0 M NaNO3, 0.1 M EDTA, or 1.0 M H2C2O4 by coprecipitation with the KFe[Fe(CN)6] solid phase formed by successive addition of K4[Fe(CN)6] and Fe(NO3)3 into these solutions. The degree of 60Co removal varies from ∼80 to ∼99.9% depending on the experimental conditions. This procedure allows simultaneous removal of 137Cs from the same solution with no less than 97% efficiency.

Interaction of aqueous UO22+ solutions with sorbents based on modified silica gel containing Cu, Ni, and Zn

Interaction of aqueous UO22+ solutions with modified sorbents based on coarsely porous silica gel MSKG, containing Cu, Ni, and Zn ions, was studied. Uranyl ions are sorbed on all the sorbents. The decontamination factors of 10−2 M aqueous UO22+ solutions on straight MSKG and on MSKG modified with Cu, Ni, and Zn are of the same order of magnitude and do not exceed 100. In the case of 1.1 × 10−1 M UO22+ solutions, the decontamination factors on straight MSKG and on MSKG modified with Cu, Ni, and Zn are also of the same order of magnitude but do not exceed 10. Interaction of the modified Ni-containing sorbent with a UO22+ solution results in formation of a swamp-green precipitate of the composition NiU(OH)6·4N2H5OH, i.e., UO22+ is reduced to U4+.

Sorption of 85Sr, 137Cs, and 152Eu from solutions on mixed hexacyanoferrates of potassium and uranyl

Sorption of 85Sr, 137Cs, and 152Eu from neutral and acidic solutions on mixed hexacyanoferrates of potassium and uranyl K4(UO2)4[Fe(CN)6]3 · 4H2O and K2(UO2)5[Fe(CN)6]4 · 3H2O is studied. The distribution coefficients of 85Sr, 137Cs, and 152Eu between the solid phase of K2(UO2)5[Fe(CN)6]4 · 3H2O and the aqueous phase are determined to be 210±10, 3000±500, and 1100±250 ml g−1, respectively, at a contacting time of 120 min. For solid K4(UO2)4[Fe(CN)6]3 · 4H2O, the respective values are 6670±900, 5600±300, and 3300±250 ml g−1. The 85Sr, 137Cs, and 152Eu distribution coefficients Kd between the solid K4(UO2)4[Fe(CN)6]3 · 4H2O and the aqueous phase decrease with decreasing pH.

Use of Modified Sorbents Based on Activated Carbon BAU-A for the Extraction of Nonferrous Metals from Aqueous Solutions

The sorption of some nonferrous metals (Cu, Ni, Zn, Pb) from aqueous solutions by granular sorbents based on activated carbon BAU-A has been studied. The surface modification of BAU-A has been conducted by exposing it to a nitrating atmosphere (NOx–air or HNO3 (vapors)–air) at a temperature of 90–110°C for 4 h and impregnating it with 10 wt % of triethanolamine (TEA), tetraethylenediamine (TEDA), or carbamide (CH4N2O). It has been found that modification of BAU-A leads to a decrease in the sorption capacity of this material with respect to Cu2+, Ni2+, and Zn2+ and an increase with respect to Pb2+.

Coprecipitation of 60Co with d element sulfides from aqueous solutions in the presence of EDTA

Coprecipitation of 60Co microamounts from aqueous solutions with sulfides of d elements (Cu2+, Ni2+, Co2+) in the presence of 10−2 M EDTA was studied. Under these conditions, the initial solution can be efficiently decontaminated from 60Co by its coprecipitation with NiS. The degree of coprecipitation of 60Co microamounts with NiS exceeds 95% at [Na2S]: [Ni2+] = (5–10): 1.

Recovery of 137Cs, 90Sr, 90Y, and d-element ions from aqueous solutions with sorbents containing triethylenediamine

The possibility of using sorbents based on KSKG coarsely porous silica gel and containing triethylenediamine N(CH2-CH2)3N (TEDA) for recovering 137Cs, 90Sr, 90Y, and d-element ions (Cu2+, Ni2+) from aqueous solutions was examined. Both 90Sr, 90Y radionuclides and Cu2+, Ni2+ ions are sorbed on KSKG containing 0.01–6.72 wt % TEDA. However, on sorbents based on KSKG and containing complexes of Cu2+, Ni2+, and Zn2+ nitrates with TEDA, the 137Cs, 90Sr, and 90Y radionuclides are not sorbed. The equilibrium in the systems with these sorbents is attained within 3 h. The sorption capacity for Cu2+ and Ni2+ strongly depends on the conditions of the sorbent synthesis. The capacity of the sorbents for Cu2+ varies from 63 to 320 mg of metal per gram of sorbent. For Ni2+, the sorption capacity is considerably lower (no more than 130 mg of Ni2+ per gram of sorbent). The distribution coefficients of 90Sr and 90Y are 300–700 ml g−1 at the contact time of the solid and liquid phases of 96 h and V/m = 100 ml g−1.