Adsorption of radium‐226 by biological origin absorbents

Abstract

Selected samples of waste microbial biomass used in industrial fermentation processes and wastewater biological treatment plants have been studied for their radium biosorption ability from aqueous solutions. Equilibrium biosorption isotherms have been used to quantify the radium uptake capacity of the various types of biomass which were also compared to two types of activated carbon. Solution pH affected the observed uptake significantly. In general, the biomass types that showed appreciable sorption capacity exhibited maximum uptake between pH 7 and 10. The uptake was reduced considerably at pH 4 and little or no uptake was observed at pH 2. Radium biosorptive uptake capacities of the order of 4.5 x 10(4) nCi/g, at pH 7 and at an equilibrium radium concentration of 1000 pCi/L, were determined for a mixed culture, while the biomass of Penicillium chrysogenum adsorbed 5 x 10(4) nCi/g radium under the same conditions. The highest uptake value for a sample of F-400 granular activated carbon was 3600 nCi/g at pH 7 and 1000 pCi/L radium concentration. The biosorptive radium uptake of microbial biomass is compared to literature values for other types of adsorbents. The most effective biomass types studied exhibited radium removals in excess of 99% of the radium in solution.

Adsorption of radium‐226 from solution by the container walls

“…At pH 2 the observed radium adsorption by the glass flasks was low, about 2% of initial radium solution concentration at 500 pCi/mL. At pH 4 and 7, radium adsorption occurred ranging from 5% to 14% of the initial radium solution concentration at 500 pCi/mL, and at pH 9 to 10, variable adsorption was experienced reaching 35% of the initial radium solution concentration, at 500 pCi/mL (Tsezos and Keller, 1983). Polyethylene has a lower critical surface tension than glass (Table I).…”

“…A distilled water rinse followed by 48 hours 1 M HCl soaking was adopted as the standard cleaning procedure for all subsequent experimental work with radium solutions. In other work it has also proven to be satisfactory (Tsezos and Keller, 1983).…”

“…It was experimentally observed that the container walls, where the adsorption experiments are carried out, exhibit an uptake of radium. The uptake of radium by glass surfaces at neutral to basic pH has already been reported (Tsezos and Keller, 1983). This uptake leads to an appreciable amount of radium adsorption, particularly for a flask that is used at high solution pH values.…”

“…It has been shown (Vdovenko and Dubasov, 1975) that EDTA at this pH is an excellent leaching agent for radium. The resulting radium-EDTA solution was then analyzed for radium-226 content, using a y-ray spectroscopy technique monitoring bismuth-214 for the higher concentration radium solutions (Tsezos and Keller, 1983), or the radon emanation technique (Rushing, 1978) for the low level radium concentration solutions From this analysis, an estimate of the residual radium left on the flask walls, following each cleaning procedure, was obtained. The bismuth-214 technique permitted measurements with 2.5% precision over a 500 to 4000 s counting period, with a limit of detection of 1 pCi/mL at 4000 s counting period.…”

Remediation of Radionuclide Pollutants through Biosorption – an Overview

“…Cell walls of bacteria are principally composed of peptidoglycans which consist of linear chains of the disaccharide N ‐acetylglucosamine‐β‐1,4‐ N ‐acetylmuramic acid with peptide chains. Fungal cell walls contain chitin and chitosan, which have been shown to sequester metal ions 47.…”