Multiwall carbon nanotubes (MWCNTs) oxidized by nitric acid solution were used to investigate the adsorption behavior of strontium
from aqueous solutions similar to the nuclear waste media. The physical properties of both as produced and oxidized MWCNTs
were studied by Boehm’s titration method and nitrogen adsorption/desorption. The results showed that the surface properties
of MWCNTs such as specific surface area, functional groups and the total number of acid sites were improved after oxidation.
Furthermore, the effect of solution conditions such as initial concentration of strontium(II), pH, ionic strength, MWCNT concentration
and contact time were studied at room temperature. The results of this study showed that the adsorption of strontium(II) was
significantly influenced by the pH value and the solution ionic strength. According to the Langmuir model, the maximum adsorption
capacities of strontium(II) onto the as produced and oxidized MWCNTs were obtained as 1.62 and 6.62 mg g−1, respectively. The contact time to reach equilibrium was 100 min. The good adsorption of strontium(II) on oxidized MWCNTs
at the lower ionic strength, the relatively high pH and the short equilibrium time indicate that the oxidized MWCNTs have
great potential applications in the field of the environmental protection.
Preparation conditions of composite ion-exchanger based on stannic molybdophosphate (SMP) and poly-acrylamide (PAA) have been
described. Batch distribution coefficients for some ions were investigated at 25 °C. Sodium ion exchange capacity and breakthrough
curves of cesium and strontium ions have also been determined. The results obtained from the experiments showed that the selectivity
of SMP-PAA for cesium and strontium was greater than for other ions. Adsorption amounts of both ions were higher than 99%
in demineralized water and their uptake rate were relatively rapid.
Multiwall carbon nanotubes (MWCNTs) were modified by nitric acid solution and then used to study the adsorption of cesium
from aqueous solution using a batch technique under ambient conditions. As produced and oxidized MWCNTs were characterized
by nitrogen adsorption/desorption, Boehm’s titration method and Fourier transform infrared spectroscopy. The physical properties
of MWCNTs such as functional groups, total number of acid sites and specific surface area were greatly improved after oxidation,
and these were responsible for more sorption of cesium from aqueous solution and made them more dispersible in water. The
adsorption of cesium ions as a function of contact time, initial concentration of cesium, pH, ionic strength and oxidized MWCNT concentrations was also investigated. The results showed that cesium adsorption percentage
strongly depended on the pH value, oxidized MWCNT content and on the solution ionic strength. Kinetic data indicated that
the adsorption process achieved equilibrium within 80 min. Equilibrium data for as produced and oxidized MWCNTs was well described
by both Freundlich and Langmuir isotherms. The dominant mechanism of cesium adsorption on oxidized MWCNTs may be mainly attributed
to ion exchange. This study suggests that oxidized MWCNTs can be a promising candidate for the removal of cesium from nuclear
Authors:R. Yavari, Y. Huang, S. Ahmadi, and G. Bagheri
This study investigates uptake of cesium and strontium from aqueous solution similar to nuclear waste on three samples of
titanium molybdophosphate (TMP) synthesized under various conditions. Effects of concentration of sodium nitrate, pH and contact
time on the uptake of cesium and strontium have been studied by bath method. The results showed that TMP has high affinity
toward cesium and strontium at pH > 2 and relatively low concentration of sodium nitrate. Kinetic data indicated that cesium
uptake process to achieve equilibrium was faster than strontium. Cesium and strontium breakthrough curves were examined at
25 °C using column packed with H3O+ form of TMP and breakthrough curves showed symmetrical S-shaped profiles. At the same time, the calculated breakthrough capacity
for cesium was higher than strontium. The results of desorption studies showed that over 99% of cesium and strontium was washed
out of column by using 4 M NH4Cl solution. This study suggests that TMP can have great potential applications for the removal of strontium and specially
cesium from nuclear waste solution.
Authors:R. Yavari, A. R. Khanchi, M. G. Maragheh, and S. Waqif-Husain
Samples of a new inorganic ion-exchanger thorium tungstophosphate have been prepared under various conditions. The ion exchange
capacity, IR, XRD, thermogravimetry and sorption of the radionuclides have been studied. Separation of Sr-Nd, Sr-Ce, Cr-Mo
and Cs-Nd have been developed on columns of this ion-exchanger.
Authors:H. Sepehrian, M. Ghannadi-Maragheh, S. Waqif-Husain, R. Yavari, and A. Khanchi
Five different samples of a new sorbent, modified mesoporous cerium(IV) silicate have been prepared with various mole ratios
of Si/Ce and Cetyltrimethylammonium bromide (CTMABr) as template. XRD, nitrogen sorption, SEM, IR, thermogravimetry and sorption
of radionuclides have been studied. Separation of Hg(II)-Th(IV), Hg(II)-Zr(IV) and Rb(I)-Zr(IV) have been developed on columns
of this novel sorbent.