7Be Recovery from Seawater by Sorbents of Various Types.

For the first time, a comprehensive study of sorbents based on manganese dioxide was carried out for beryllium sorption from seawater in laboratory and expeditionary conditions. The possibility of using several commercially available sorbents based on manganese dioxide (Modix, MDM, DMM, PAN-MnO2) and phosphorus(V) oxide (PD) for 7Be recovery from seawater for solving oceanological problems was evaluated. Beryllium sorption under static and dynamic conditions was studied. The distribution coefficients and dynamic and total dynamic exchange capacities were determined. Sorbents Modix (Kd = (2.2 ± 0.1) × 103 mL/g) and MDM (Kd = (2.4 ± 0.2) × 103 mL/g) showed high efficiency. The dependences of the degree of recovery on time (kinetics) and the capacity of the sorbent on the beryllium equilibrium concentration in solution (isotherm) were established. The data obtained were processed using kinetic models (intraparticle diffusion, pseudo-first and pseudo-second orders, Elovich model) and sorption isotherm equations (Langmuir, Freindlich, Dubinin-Radushkevich). The paper contains results of expeditionary studies to evaluate the sorption efficiency of 7Be from large volumes of the Black Sea water by various sorbents. We also compared the sorption efficiency of 7Be for the considered sorbents with aluminum oxide and previously obtained sorbents based on iron(III) hydroxide.

Radionuclides' Recovery from Seawater Using FIC and FIC A Sorbents.

To solve radioecological and oceanological problems (estimate the vertical transport, flows of particulate organic carbon, phosphorus biodynamics, submarine groundwater discharge, etc.), it is necessary to determine the natural values of the radionuclides' activity in seawater and particulate matter. For the first time, the radionuclides' sorption from seawater was studied using sorbents based on activated carbon modified with iron(III) ferrocyanide (FIC) and based on activated carbon modified with iron(III) hydroxide (FIC A-activated FIC) obtained by FIC sorbent treatment with sodium hydroxide solution. The possibility of trace amounts of phosphorus, beryllium, and cesium recovery in laboratory conditions has been investigated. Distribution coefficients, dynamic, and total dynamic exchange capacities were determined. The physicochemical regularities (isotherm and kinetics) of sorption have been studied. The results obtained are characterized via Langmuir, Freindlich, and Dubinin-Radushkevich isotherm equations, as well as pseudo-first and pseudo-second-order kinetic models, intraparticle diffusion, and the Elovich model. Under expeditionary conditions, the sorption efficiency of 137Cs using FIC sorbent, 7Be, 32P, and 33P-using FIC A sorbent with a single-column method by adding a stable tracer, as well as the sorption efficiency of radionuclides 210Pb and 234Th with their natural content by FIC A sorbent in a two-column mode from large volumes of seawater was assessed. High values of efficiency of their recovery by the studied sorbents were achieved.

Assessment of Seasonal Variability in Phosphorus Biodynamics by Cosmogenic Isotopes 32P, 33P around Balaklava Coast.

The sorption efficiency of phosphorus from seawater by aluminum oxide and sorbents based on Fe(OH)3 obtained by various methods (using prepared sodium ferrate or precipitation of Fe(OH)3 with ammonia) was assessed. It was shown that phosphorus was recovered most efficiently at a seawater flow rate of one-to-four column volumes per minute with a sorbent based on hydrolyzed polyacrylonitrile fiber with a precipitation of Fe(OH)3 with ammonia. Based on the results obtained, a method for phosphorus isotopes recovery with this sorbent was suggested. Using this method, the seasonal variability of phosphorus biodynamics in the Balaklava coastal area was estimated. For this purpose, the short-lived isotopes of cosmogenic origin 32P and 33P were used. Volumetric activity profiles of 32P and 33P in particulate and dissolved forms were obtained. Based on 32P and 33P volumetric activity, indicators of phosphorus biodynamics were calculated: the time, rate, and degree of phosphorus circulation to inorganic and particulate organic forms. In spring and summer, elevated values of phosphorus biodynamic parameters were determined. This is explained by the peculiarity of the economic and resort activities of Balaklava, which negatively affect the state of the marine ecosystem. The results obtained can be used to assess the dynamics of changes in the content of forms of dissolved and suspended phosphorus, and the biodynamic parameters when performing a comprehensive environmental assessment of the state of coastal waters.