National Academy of Sciences of Ukraine Sr and Cs selective calixarene-based sorbents: analytical application in environmental chemistry

Radionuclides normalized in water of economical and drinking water supply sources* RadionuclideТ 1/2, yearsMCL, Bk/L Natural radionuclides 222 Rn3,82 days Ra Ra5,751 U, isotope sum1 Artificial nuclides, falling out as a result of an accidents 90 Sr Cs Pu (total activity) 240 Pu Pu14,4 210 Po139 days 241 Am232 *Норми радіаційної безпеки України (НРБУ-97); Державні гігієнічні нормативи. – Київ: Відділ поліграфії українського центру держсанепіднагляду МОЗ України, – 125с. 2

Composite materials for α- and β- emitting nuclides determination in water The existing methods for radionuclide determination in natural waters are not sufficiently sensitive and precise Goal of the work : - Obtaining materials, combining radionuclide concentration and detection processes for utilization in radiation monitoring - Development of their application methods for selective determination of radionuclide content in natural waters Ways of accuracy improvement Preliminary concentration of small amounts of radionuclides from large volume of investigated solution Use of 4π-geometry emission registration 3

MethodsDrawbacks Flow detectors in combination with extraction or chromatography Short counting time; poor resolution;detection limits for α-emitters -500 Bk/L, for β-emitters – 350 Bk/L Liquid scintillating detectors in combination with extraction or chromatography Deterioration of scintillation characteristics when large volume of water is used; high detection limits. Porous scintillators with branchy surface 2-π registration geometry; clogging up of surface with radionuclides. Radiochemical methods21 stage of a sample preparation;activity measurement directly after separation stage and in 2-4 weeks, that is after equilibrium between Sr-90 and Y-90 is achieved. 4

Aim of the work –creating material with the specified properties: selectivity towards radionuclide or radionuclide family; presence of through pores of desired size and location; high light output and registration efficiency; analysis performance and low cost. Analyzed solution Pore forming agent Sorbent Radionuclide Scintillator 5

Material composition Optimal scintillating matrix p- Terphenyl(PTF) activated 1,3-diphenylbutadiene-1,4 PTF characteristics: λmax= 420nm t f = 3-5 ns Zef = 5.8 PTF Advantages: Short luminiscence time; Stability in characteristics under influence if atmosphere and radiation; Light output stability in broad temperature range (-60º…+140ºС); Absence of scintillation characteristics anisotropy throughout volume; Possibility of growing crystals with the diameter up to 80 mm. Optimal pore forming agent NH 4 HCO 3. Tdec.= 36ºC. Optimal sorbent Sorbent characteristics: high exchange capacity; mechanical durability; color absence; absence of own luminescence; thermo- and radiation stability. For the determination of Sr and Cs we have used calixarene- impregnated polymer matrix and zeolite. 6

R O CH 2 O N 6 Alk Al k The structures of calixarenes with different functionality used in the present work as highly selective chelating agents Compounds were given by V.I. Kalchenko, Corresponding Member of the National Academy of Sciences of Ukraine, Professor, Vice-director of the Institute of Organic Chemistry, Kyiv, Ukraine 7

8 SEM images of polymer spheres cross-section in back-scattered electron mode

9 Investigation methods Inductively coupled plasma atomic emission spectrometry (ICP-AES), Thermo Jarrell Ash, USA Operating conditions λ (Sr) / nm RF Power1150 Wt Plasma gas flow14 L/min Auxiliary gas flow1 L/min Nebulizer gas flow36 psi (2,5 atm) Pump rate100 rpm Solution uptake rate1,85 mL/min Integration time2s Flame atomic emission spectrometry Saturn, USSR λ (Cs)852.1 nm FlameAcetylene-Air Integration time1s Slit width0.2 nm Grating density1200 nm -1 Operating conditions

pH Recovery rate, % Sr (a) and Cs (b) extraction rate dependencies on pH Recovery rate, % pH (a) (b) Divinyl bezene-styrene co- polymer impregnated with calix [6]-areneamide Divinyl bezene-styrene co- polymer impregnated with calix [4]-arene-crown-6 10

0 0,5 1 1,5 2 2,5 3 3,5 4 4, C, мg/l А, mg/g (a) (b), Langmuir model (eq. a) Metal cation К L, l/мgА ∞, мg/gR2R2 Sr ,992 Cs Freindlich model (eq. b) Metal cation К F, мg/gnR2R2 Sr Cs C – ion equilibrium concentration, mg/l; A – equilibrium sorption capacity, mg/g; A∞ - maximum sorption capacity, mg/g; К L - Langmuir constant, l/mg К F – Freindlich constant, mg/g; n – Freindlich isotherm constant, indicating sorption intensity where Absorption isotherm of Sr 2+ on the calix[6]areneamide impregnated polymer 11 Absorption isotherm of Cs + on the calix[4]crown[6]arene impregnated polymer Absorption isotherms

12 Mordenite in -Na form d < mm Removing diluent at 100ºC Drying at 120ºC 1g of calix[6]arene dissolved in 10 ml of CH 2 Cl 2 Mordenite soaked in NaCl solution during 24 hours at ambient temperature Washing with distilled water Washing with methanol Treated actively during 60 min Drying at 50ºC during 3 hours Impregnation tri-n-butyl phosphate dissolved in CH 2 Cl 2 Scheme of mordenite impregnation with calix[6]arene

13 IR spectra of mordenite before and after impregnation with calix[6]arene Distilled water40% Model solution4% Without calixarene, model solution 8% Sr recovery rates in systems containing calixarene-impregnated mordenite

14 Prospective work Design of highly selective scintillating sorbent with the use of materials investigated Investigation and optimization of physicochemical parameters of the composite materials obtained Developing the experimental technique for measuring the radionuclide concentration in water samples with the use of porous scintillator obtained The work is supported by STCU Grant No 4955 “Composite materials on the basis of highly selective calixarene sorbents for determination of radionuclides in environments”

Thank you very much for your kind attention! 15