A new method for the preconcentrations of U(VI) and Th(IV) by magnetized thermophilic bacteria as a novel biosorbent

Use of Chrysosporium/carbon nanotubes for preconcentration of ultra-trace cadmium levels from various samples after extensive studies on its adsorption properties

Carbon nanotubes were used to immobilize Chrysosporium fungus for building an adequate adsorbent to be used as an desirable sorbent for preconcentration and measurement of cadmium ultra-trace levels in various samples. After characterization, the potential of Chrysosporium/carbon nanotubes for the sorption of Cd(II) ions was scrutinized by the aid of central composite design, and comprehensive studies of sorption equilibrium, kinetics and thermodynamic aspects were accomplished. Then, the composite was utilized for preconcentration of ultra-trace cadmium levels, by a mini-column packed with Chrysosporium/carbon nanotubes, before its determination with ICP-OES. The outcomes vouchsafed that (i) Chrysosporium/carbon nanotube has a high tendency for selective and rapid sorption of cadmium ion, at pH 6.1, and (ii) kinetic, equilibrium, and thermodynamic studies showed a high affinity of the Chrysosporium/carbon nanotubes for cadmium ion. Also, the outcomes displayed that cadmium can quantitatively be sorbed at a flow speed lesser than 7.0 mL/min and a 1.0 M HCl solution (3.0 mL) was sufficient to desorbe the analyte. Eventually, preconcentration and measurement of Cd(II) in different foods and waters were successfully accomplished with good accuracy, high precision (RSDs ≤5.65%), and low limit of detection (0.015 μg/L).

Adsorption performance of Enterobacter cloacae towards U(VI) ion and application of Enterobacter cloacae/carbon nanotubes to preconcentration and determination of low-levels of U(VI) in water samples

Keeping the high potential of some microorganisms in adsorption of radionuclides in view, the adsorption properties of Enterobacter cloacae towards uranium were attentively scrutinized, and then it was used for preconcentration of uranium in different samples, using Enterobacter cloacae/carbon nanotube composite. First, using ultrasonic agitation, the effects of operational factors on biosorption of uranium on the inactive Enterobacter cloacae were appraised and modeled by central composite design, and a comprehensive study was performed on the equilibrium, kinetics, thermodynamic, and selectivity aspects of biosorption. The optimization studies along with the evaluations of the adsorption properties revealed that Enterobacter cloacae have a high affinity for fast and selective biosorption of uranium ions, at pH 5.1. Second, the Enterobacter cloacae/carbon nanotube was synthesized, characterized, and utilized for preconcentration of uranium in different samples, using a mini-column packed with the composite. The optimization of operational factors on recovery of uranium, using the central composite design, showed that uranium can be quantitively adsorbed at a sample flow rate lower than 4.5 mL min^-1 and the desorption could be accomplished with 3.0 mL HCl 0.6 M solution. Finally, the mini-column was exploited for preconcentration and determination of uranium in different samples. The results revealed the low detection limit (0.015 μg.L^-1), high precision (RSDs ≤3.92%), and good accuracy of the proposed procedure.