Biosorption of U(VI) by the green algae Chlorella vulgaris in dependence of pH value and cell activity

• Published in: The Science of the total environment Vol. 409; no. 2; pp. 384 - 395
• Main Authors: Vogel, M., Günther, A., Rossberg, A., Li, B., Bernhard, G., Raff, J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.12.2010; [Amsterdam; New York]: Elsevier Science; Elsevier
• Subjects: Algae; Animal, plant and microbial ecology; Applied ecology; ATR–FTIR; Biological and medical sciences; Biomass; Chlorella vulgaris; Chlorella vulgaris - chemistry; Chlorella vulgaris - metabolism; Chlorella vulgaris - radiation effects; Complexation; Drying; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; EXAFS; Fine structure; Fresh Water - chemistry; Fundamental and applied biological sciences. Psychology; Green algae; Hydrogen-Ion Concentration; Sorption; Spectroscopy; TRLFS; Uranium; Uranium - chemistry; Uranium - metabolism; Uranium - toxicity; Uranium(VI); Water Pollutants, Radioactive - chemistry; Water Pollutants, Radioactive - metabolism; Water Pollutants, Radioactive - toxicity; Sorption; Green algae; ATR–FTIR; TRLFS; Uranium(VI); EXAFS; Vegetals; ATR-FTIR; Algae; Chlorella vulgaris; Radioisotope; Chlorophyceae; Experimental study; Absorption; Uranium; Chlorophyta; pH
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2010.10.011

Biosorption of uranium(VI) by the green alga Chlorella vulgaris was studied at varying uranium concentrations from 5 μM to 1 mM, and in the environmentally relevant pH range of 4.4 to 7.0. Living cells bind in a 0.1 mM uranium solution at pH 4.4 within 5 min 14.3 ± 5.5 mg U/g dry biomass and dead cells 28.3 ± 0.6 mg U/g dry biomass which corresponds to 45% and 90% of total uranium in solution, respectively. During 96 h of incubation with uranium initially living cells died off and with 26.6 ± 2.1 mg U/g dry biomass bound similar amounts of uranium compared to dead cells, binding 27.0 ± 0.7 mg U/g dry biomass. In both cases, these amounts correspond to around 85% of the initially applied uranium. Interestingly, at a lower and more environmentally relevant uranium concentration of 5 μM, living cells firstly bind with 1.3 ± 0.2 mg U/g dry biomass to 1.4 ± 0.1 mg U/g dry biomass almost all uranium within the first 5 min of incubation. But then algal cells again mobilize up to 80% of the bound uranium during ongoing incubation in the time from 48 h to 96 h. The release of metabolism related substances is suggested to cause this mobilization of uranium. As potential leachates for algal-bound uranium oxalate, citrate and ATP were tested and found to be able to mobilize more than 50% of the algal-bound uranium within 24 h. Differences in complexation of uranium by active and inactive algae cells were investigated with a combination of time-resolved laser-induced fluorescence spectroscopy (TRLFS), extended X-ray absorption fine structure (EXAFS) spectroscopy and attenuated total reflection Fourier transform infrared (ATR–FTIR) spectroscopy. Obtained results demonstrated an involvement of carboxylic and organic/inorganic phosphate groups in the uranium complexation with varying contributions dependent on cell status, uranium concentration and pH.