Shunzhong Luo

Biosorption of uranium on Bacillus sp. dwc-2: preliminary investigation on mechanism

In this paper, the biosorption mechanisms of uranium on an aerobic Bacillus sp. dwc-2, isolated from a potential disposal site for (ultra-) low uraniferous radioactive waste in Southwest China, was explored by transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, FT-IR spectroscopy, proton induced X-ray emission (PIXE) and enhanced proton backscattering spectrometry (EPBS). The biosorption experiments for uranium were carried out at a low pH (pH 3.0), where the uranium solution speciation is dominated by highly mobile uranyl ions. The bioaccumulation was found to be the potential mechanism involved in uranium biosorption by Bacillus sp. dwc-2, and the bioaccumulated uranium was deposited in the cell interior as needle shaped particles at pH 3.0, as revealed by TEM analysis as well as EDX spectra. FTIR analysis further suggested that the absorbed uranium was bound to amino, phosphate and carboxyl groups of bacterial cells. Additionally, PIXE and EPBS results confirmed that ion-exchange also contributed to the adsorption process of uranium. All the results implied that the biosorption mechanism of uranium on Bacillus sp. is complicated and at least involves bioaccumulation, ion exchange and complexation process.

Biosorption of americium-241 by Saccharomyces cerevisiae

The biosorption of radionuclide 241Am from solution by Saccharomyces cerevisiae (S. cerevisiae), and the effects of experimental conditions on the adsorption were investigated. The preliminary results showed thatS. cerevisiae is a very efficient biosorbent. An average of more than 99% of the total 241Am could be removed by S. cerevisiae of 2.1 g/l (dry weight) from 241Am solutions of 17.54–4386.0 mg/l (2.22 MBq/l–555 MBq/l) with adsorption capacities of 7.45–1880.0 mg/g biomass (dry weight) (0.94 MBq/g–237.9 MBq/g). The adsorption equilibrium was achieved within 1 hour and the optimum pH ranged 1–3. No significant differences on 241Am adsorption were observed at 10–45 °C, or in solutions containing Au3+ or Ag+, even 2000 times above 241Am concentration. The relationship between concentrations and adsorption capacities of 241Am indicated the biosorption process should be described by the Freundlich adsorption isotherm.

CMPO-calix[4]arenes with spacer containing intramolecular hydrogen bonding: effect of local rigidification on solvent extraction toward f-block elements.

To understand intramolecular hydrogen bonding in effecting liquid-liquid extraction behavior of CMPO-calixarenes, three CMPO-modified calix[4]arenes (CMPO-CA) 5a-5c with hydrogen-bonded spacer were designed and synthesized. The impact of spacer rotation that is hindered by introduction of intramolecular hydrogen bonding upon extraction of La(3+), Eu(3+), Yb(3+), Th(4+), and UO2(2+) has been examined. The results show that 5b and 5c containing only one hydrogen bond with a less hindered rotation spacer extract La(3+) more efficiently than 5a containing two hydrogen bonds with a more hindered rotation spacer, demonstrating the importance of local rigidification of spacer in the design of extractants in influencing the coordination environment. The large difference in extractability between La(3+) and Yb(3+) (or Eu(3+)) by 5b (or 5c), and the small difference by 5a, suggests intramolecular hydrogen bonding do exert pronounced influence upon selective extraction of light and heavy lanthanides. Log-log plot analysis indicates a 1:1, 2:1 and 1:1 stoichiometry (ligand/metal) for the extracted complex formed between 5b and La(3+), Th(4+), UO2(2+), respectively. Additionally, their corresponding acyclic analogs 7a-7c exhibit negligible extraction toward these metal ions. These results reveal the possibility of selective extraction via tuning local chelating surroundings of CMPO-CA by aid of intramolecular hydrogen bonding.

A simple and convenient method for production of (89)Zr with high purity.

A simple and convenient method for radiochemical separation 89Zr with no harmful substance was explored. The separated 89Zr was found to be [89Zr]Zr-chloride, and the recovery of the radioactivity was 85%±3% with high radionuclidic purity (99.99%). The yields of 89Zr via the reaction of (p, n) or (d, 2n) on Y target were also evaluated on CS-30 cyclotron, indicating the latter was more favorable for the production of 89Zr with a yield of 58±4 MBq/μA·h.

Biosorption of 241Am by Rhizopus arrihizus: preliminary investigation and evaluation

The biosorption of 241Am from solution by a fungus-Rhizopus Arrihizus (R. arrihizus), and the effect of experimental conditions on the adsorption were investigated. The preliminary results showed that the biosorption of 241Am by R. arrihizus is very efficient. An average of more than 99% of the total 241Am was removed by R. arrihizus of 1.3 g/l (dry weight) from 241Am solutions of 5.6-111 MBq/l (44.3-877.2 microg/l) (C0), with adsorption capacities (W) of 4.2-79.4 MBq/g biomass (dry weight) (33.2-627.5 microg/g). The biosorption equilibrium was achieved within 1 h and the optimum pH ranged from 1 to 3. No significant differences in 241Am biosorption were observed at 10-45 degrees C, or in solutions containing Au3+ or Ag+, even 2,000 times above 241Am concentration. The relationship between concentrations and adsorption capacities of 241Am indicated that the 241Am biosorption by R. arrihizus obeys the Freundlich adsorption equation.

Sorption of 241Am by Aspergillus niger spore and hyphae

Biosorption of 241Am by a fungus A. niger, including the spore and hyphae, was investigated. The preliminary results showed that the adsorption of 241Am by the microorganism was efficient. More than 96% of the total 241Am could be removed from 241Am solutions of 5.6-111 MBq/l (Co) by spore and hyphaeof A. niger, with adsorbed 241Am metal (Q) of 7.2-142.4 MBq/g biomass, and 5.2-106.5 MBq/g, respectively. The biosorption equilibrium was achieved within 1 hour and the optimum pH range was pH 1-3. No obvious effects on 241Am adsorption by the fungus were observed at 10-45 °C, or in solutions containing Au3+ or Ag+, even 2000 times above the 241Am concentration. The 241Am biosorption by the fungus obeys the Freundlich adsorption equation. There was no significant difference between the adsorption behavior of A. nigerspore and hyphae.

Biosorption of americium-241 by Candida sp.

Summary As an important radioisotope in nuclear industry and other fields, americium-241 is one of the most serious contamination concerns duo to its high toxicity and long half-life. In this experiment, the biosorption of 241Am from solution by Candida sp., and the effects of various experimental conditions on the adsorption were investigated. The preliminary results showed that the adsorption of 241Am by Candida sp. was efficient. 241Am could be removed by Candida sp. of 0.82g/L (dry weight) from 241Am solutions of 5.6-111MBq/L (44.3-877.2μg/L)(C0), with maximum adsorption rate (R) of 98 and maximum adsorption capacities (W) of 63.5MBq/g biomass (dry weight) (501.8μg/g). The biosorption equilibrium was achieved within 4 hour and the optimum pH was pH=2. No significant differences on 241Am adsorption were observed at 10°C–45°C, or in solutions containing Au3+ or Ag+, even 1500 times or 4500 times above the 241Am concentration, respectively. The relationship between concentrations and adsorption capacities of 241Am indicated the biosorption process should be described by a Langmuir adsorption isotherm.

Highly selective extraction of Pd(II) with 5-octyloxymethyl-7-bromo-8-quinolinol from acidic solution

A novel extractant, 5-octyloxymethyl-7-bromo-8-quinolinol (HBrO8Q), was employed to extract Pd(II) from low-acidity aqueous solution. The extraction behaviors indicated that HBrO8Q had high extraction efficiency and selectivity for Pd(II) under the experimental conditions, and the stoichiometry of Pd(II) with HBrO8Q was found to be 1:1 by means of mole ratio method and Job’s method. The thermodynamic study indicated that the extraction process was endothermic and spontaneous. Additionally, complete back extraction of palladium could be achieved by using acidic thiourea solution.