The sorption of Th(IV) onto TiO2 was studied by the batch technique as a function of pH and ionic strength at moderate concentration (10-4-10-5 mol/l) and in the presence and absence of phosphate. It was found that the sorption rate of Th(IV) was relatively slow, the
sorption percent was abruptly increased from pH 2 to 4, and the sorption was decreased with increasing ionic strength as a
whole. In the concentration range of Th(IV) from trace concentration to 1.4 . 10-4 mol/l and in the absence of phosphate, the sorption isotherms were roughly fitted the Freundlich equation at different ionic
strengths and approximately constant pH. These sorption characteristics of Th(IV) onto TiO2 were compared with those of uranyl on the same sorbent. In addition, the positive effect of phosphate on the sorption of
Th(IV) onto TiO2 was demonstrated obviously and can be attributed to strong surface binding of phosphate, and the subsequent formation of
ternary surface complexes of Th(IV). The difference between the sorption characteristics of Th(IV) ions and uranyl ions onto
TiO2 is discussed.
The sorption of UO22+ on TiO2 was studied as a function of pH and ionic strength at moderate concentration (10-4-10-5mol/l) in the presence and absence of fulvic acid (FA, 20 mg/l). It was found that the sorption rates in the presence and
absence of FA are fast and similar, slowly and similarly increased with increasing pH from 2 to 10. The sorption in the absence
of FA increased with increasing ionic strength while, in the presence of FA it decreased. FA caused a relative enhancement
in the sorption at pH<6. The sorptions in the presence and absence of FA at constant pH followed the linear sorption isotherm,
and the distribution coefficients found are of the order of 10 to 103 ml/g.
Authors:Zuyi Tao, Wenming Dong, Jingzhou Du and Zhijun Guo
The effect of different solid components of calcareous soil on the retention of I was investigated by a batch technique and selective extraction method, and the effect of -irradiation was also investigated. The sorption and desorption isotherms of I on the one untreated, three treated soils and the calcareous soil irradiated with -rays were determined at 30 °C, pH 8.1±0.2 and in the presence of 1.0×10–4M or 0.67×10–5M CaCl2. It was found that the sorption-desorption hysteresis on the calcareous soil actually occurs on the same time scale, that iodine can be easily transported in the calcareous soil and that the exceptionally high contribution of organic matter to the iodine sorption is demonstrated.
Authors:Guo Zhijun, Wu Wangsuo, Shao Dadong and Tan Minyu
Two open-chain crown ethers 2,2'-(ethylenedioxy)bis[(8-quinolyloxymethyl)benzene], (L1), and 2,2'-(ethylenedioxy)bis[(8-quinaldyloxymethyl)benzene], (L2) have been prepared and characterized by using elemental analysis, IR spectra, 1H NMR spectra and positive-ion FAB mass spectra. The extraction of UO22+ and Th4+ by both open-chain crown ethers, L1 and L2 in chloroform as a diluent was studied at 25 °C. Extraction distribution ratios (D) of UO22+ and Th4+ were investigated as a function of pH, lithium picrate concentration, and extractant concentration. Based on the expertimental results, it was found that 1 : 1 complexes were formed involving either UO22+ or Th4+ with L1, and Th4+ with L2. The extractability of L1 for Th4+ is significantly higher than that for UO22+, the extractabilities of L1 and L2 for Th4+ being almost identical. L1 and L2 used here are not feasible for industry because of their relatively low extractabilities for Th4+ at pH<2.0 and for UO22+ at the extraction conditions used in this work.
Authors:Keliang Shi, Fuqiang Liu, Yuanlv Ye, Zhijun Guo and Wangsuo Wu
Metal ions sorption can be significantly affected by the presence of other sorbates, especially of complexing ligands. In
this study, the effect of Se(IV) on Eu(III) sorption onto TiO2 at different pH and Eu(III) concentration was investigated. Se(IV) was found to enhance Eu(III) sorption as a function of
Se(IV) concentration. Constant capacitance model was successfully used to interpret the sorption experimental data. The solubility
product of Eu2(SeO3)3 at ambient temperature was investigated to highlight the sorption mechanism of ternary sorption system. The pKsp value of Eu2(SeO3)3 was found to be 31.51 ± 0.95.
Authors:Yaling Chi, Yuantao Chen, Xia Liu, Zhijun Guo and Linsen Cai
The sorption of UO22+ from aqueous solution on attapulgite was investigated as a function of contact time, solid content, pH, ionic strength, foreign
ions, humic acid (HA), and fulvic acid (FA) under ambient conditions by using batch technique. The attapulgite sample was
characterized by XRD and FTIR in detail. The results indicated that the sorption of UO22+ was strongly dependent on pH and ionic strength. The sorption of UO22+ on attapulgite increased quickly with rising pH at pH < 6.5, and decreased with increasing pH at pH > 6.5. The presence of
HA or FA enhanced the sorption of UO22+ on attapulgite obviously at low pH because of the strong complexation of surface adsorbed HA/FA with UO22+ on attapulgite surface. Sorption of UO22+ on attapulgite was mainly dominated by ion-exchange or outer-sphere surface complexation at low pH values, but by inner-sphere
surface complexation at high pH values. The results indicate that attapulgite is a very suitable adsorbent for the preconcentration
and solidification of UO22+ from large volumes of aqueous solutions because of its negative surface charge and large surface areas.
Authors:Liu Xia, Chen Yuantao, Chi Yaling, Guo Zhijun and Cai Linsen
In this article, a series of batch experiments were carried out to investigate the effect of various environmental factors
such as contact time, solid content, pH, ionic strength, foreign ions, temperature and coexisting humic acid on the sorption
behavior radionuclide 60Co(II) on illite. The results indicated that the sorption of Co(II) was strongly dependent on pH, ionic strength and temperature.
At low pH, the sorption was dominated by outer-sphere surface complexation and ion exchange on illite surfaces, whereas inner-sphere
surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models
were used to simulate the sorption isotherms at three different temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic
data (∆G0, ∆S0, ∆H0) were calculated from the temperature dependent sorption isotherms and the results suggested that the sorption process of
Co(II) on illite was an endothermic and spontaneous process. The sorption test revealed that the illite can be as a cost-effective
adsorbent suitable for pre-concentration of Co(II) from large volumes of aqueous solutions.
Authors:Guo Zhijun, Niu Yanning, Zhang Weiguang and Tan Minyu
N,N,N',N',N'',N''-Hexaethyl-2,2′,2''-(nitrilotrisethyleneoxy-2-benzyloxy)tris(acetamide) (L3) has been prepared and characterized
by using IR, 1H NMR and positive-ion FAB mass spectra. The extraction of Th4+ and UO22+ with N,N,N',N',N'',N''-hexaethyl-2,2',2''- (nitrilo-trisethyleneoxy)tris(acetamide) (L1), N,N,N',N',N'',N''-hexaisopropyl-2,2',2''-(nitrilotrisethyleneoxy)tris(acetamide)
(L2), and L3 was studied at 20±1 °C as a function of diluent, concentration of free extractant in organic phase and concentration
of picrate in aqueous phase. It was found that the extracting powers of L1 and L2 for Th4+ are almost identical. The extracting power of L2 for UO22+ was slightly higher than that of L1. The difference in terminal
groups (ethyl or isopropyl) of the extractants (L1 and L2) with same backbone has a little effect on the extracting power
for both Th4+ and UO22+. The extracting powers of L3 for both Th4+ and UO22+ were larger than those of L1 and L2. The extractants
(L1 and L3) having the same terminal group (ethyl) with different backbones have obviously different extracting powers for
Th4+ or UO22+. The extracting powers of all three extractants L1, L2, and L3 for Th4+ were larger than those for UO22+. The
compositions of extracted species in organic phase were predominantly ThL(Pic)3NO3 and UO2L(Pic)NO3, respectively (L denotes
L1, L2 and L3).
U(VI) sorption on kaolinite was studied as functions of contact time, pH, U(VI) concentration, solid-to-liquid ratio (m/V) by using a batch experimental method. The effects of sulfate and phosphate on U(VI) sorption were also investigated. It
was found that the sorption kinetics of U(VI) can be described by a pseudo-second-order model. Potentiometric titrations at
variable ionic strengths indicated that the titration curves of kaolinite were not sensitive to ionic strength, and that the
pH of the zero net proton charge (pHPZNPC) was at 6.9. The sorption of U(VI) on kaolinite increased with pH up to 6.5 and reached a plateau at pH >6.5. The presence
of phosphate strongly increased U(VI) sorption especially at pH <5.5, which may be due to formation of ternary surface complexes
involving phosphate. In contrast, the presence of sulfate did not cause any apparent effect on U(VI) sorption. A double layer
model was used to interpret both results of potentiometric titrations and U(VI) sorption on kaolinite.