Thermodynamic and kinetic investigations of uranium adsorption on amberlite IR-118H resin.

The adsorption behavior of uranium(VI) on a strongly acidic cation exchanger amberlite IR-118H has been studied as a function of the solution concentration and temperature. Results have been analyzed by Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption 7.14kJmol(-1) was calculated from the D-R adsorption isotherm. In order to understand the significance of the diffusion mechanisms and to accurately estimate the diffusivities inside the adsorbent particles, a model for uranium(VI) adsorption on amberlite IR-118H was used. The rate constants have been calculated for 293, 313 and 333K using Lagergren equation and the activation energy (E(a)) was derived using the Arhenius equation. The thermodynamic quantities for the process of adsorption have been estimated by plotting Ln K(D) versus 1/T. The DeltaH(o) and DeltaG(o) values of uranium(VI) adsorption on amberlite IR-118H show endothermic heat of adsorption; higher temperatures favor the process.     

Radiotracer technique in adsorption study: Part XVII. Removal Behaviour of Alkali Metal (K- and Li-) Titanates for Cd(II)

Alkali metal (potassium and lithium) titanates were synthesized and employed for the efficient removal of Cd(II) ions from aqueous solutions using the radiotracer technique. The possible mechanism involved at the solid/solution interface was deduced with the help of various physico–chemical data, i.e. effect of adsorptive concentration temperature and pH. The effect of added cations and H⁺ (HCl/H₂SO₄) in the uptake process was also seen. The radiation stability of these materials in the adsorption process was assessed by employing a 11.1 GBq (Ra–Be) neutron source having an integral neutron flux of 3.85×10⁶ n·cm⁻² s⁻¹ and associated with a nominal γ-dose of ca. 1.72 Gy/h.     

Application of high resolution X-ray emission spectroscopy on the study of Cr ion adsorption by activated carbon

In this work granular activated carbon has been chosen as an absorbent in order to investigate the Cr(VI) reduced by adsorption experiments. Several batch chromium-sorption experiments were carried out using 0.25 g of granular activated carbon in 50 mL aqueous solution containing approximately 70 and 140 mg L^?1 of Cr(VI) and Cr(III), respectively. Cr–Kβ fluorescence spectra of Cr adsorbed in a carbon matrix and Cr reference materials were measured using a high-resolution Johann-type spectrometer. Based on evidence from the Cr–Kb satellite lines, the Cr(VI) reduction process has actually happened during metal adsorption by the activated carbon.     

Preparation of alpha-spectrometric sources by co-precipitation with Fe(OH)3: application to uranium

A coprecipitation method using Fe(OH)₃ as carrier, previously studied for preparation of alpha spectrometric sources of actinides, was applied to uranium samples. The results point to a special behaviour of U(VI). Although chemical recoveries were lower than those obtained for actinides such as plutonium, americium and thorium, they were strongly dependent on the concentration of U(VI) in the sample. Quantitative yields were obtained when the concentration of U(VI) exceeded 16 μg/ml. The influence of concentration on the FWHM obtained are also discussed.     

Radiation effects on rat testes. VIII. Kinetic properties of hydrolases following partial body gamma irradiation of rats.

Kinetic properties such as Michaelis constant (Km), maximum velocity (Vmax), temperature coefficient (Q10) and energy of activation (Ea) for hydrolysis of adenosine-5'-phosphate at pH 9.5 and sodium pyrophosphate at pH 8.35 by normal and radiated testes supernatants have been described. Kinetic parameters are related to respective phosphohydrolases (phosphatases). (1) Km values for 5'nucleotidase and inorganic pyrophosphatase of normal testis were determined as 1.25 X 10(-3)M and 0.81 X 10(-3)M respectively; (II) Vmax correspond to 318 mug P/15 min and 430 mug P/15 min for 100 mg tissue respectively; (III) Q10 for 5 nucleotidase is 1.7 and for inorganic pyrophosphatase is 4.2 at a temperature 10-30degreesC; (IV) Ea for hydrolysis of AMP and sodium pyrophosphate were calculated by Arrhenius plots as 17000 and 9000 cal/mol. (V) Km values for irradiated enzymes are similar to the control values suggesting that the binding capacities of these enzymes with their substrates remain unaffected after radiation; (VI) Vmax for radiated enzymes correspond to a value of 500 mug P/100 mg tissue/15 min for 5'nucleotidase and 118 mug P/100 mug tissue/15 min for inorganic pyrophosphatase; (VII) 110 for 5'nucleotidase is 2.2 and inorganic pyrophosphatase 1.16 at 10-30degreesC; (VIII) Ea for irradiated 5'nucleotidase is comparable to those of normal rats whereas for inorganic pyrophosphatase Ea is moderately declined. The observed changes have been related to the different types of metabolic activity in germinal and nongerminal cells of testes.     

Radiotracer technique in adsorption study: Part XVII. Removal Behaviour of Alkali Metal (K- and Li-) Titanates for Cd(II)

Alkali metal (potassium and lithium) titanates were synthesized and employed for the efficient removal of Cd(II) ions from aqueous solutions using the radiotracer technique. The possible mechanism involved at the solid/solution interface was deduced with the help of various physico–chemical data, i.e. effect of adsorptive concentration temperature and pH. The effect of added cations and H⁺ (HCl/H₂SO₄) in the uptake process was also seen. The radiation stability of these materials in the adsorption process was assessed by employing a 11.1 GBq (Ra–Be) neutron source having an integral neutron flux of 3.85×10⁶ n·cm⁻² s⁻¹ and associated with a nominal γ-dose of ca. 1.72 Gy/h.     

99mTc bone scanning agents--II. Adsorption of 99mTc(Sn)pyrophosphate complexes on the mineral phase of bone

The adsorption of pyrophosphate, tin-pyrophosphate and 99mTc(Sn)pyrophosphate on Ca3(PO4)2 was investigated at pH 4.0 and pH 7.4. All components were radioactively labeled. Tin and reduced technetium were in most cases almost completely bound. The adsorption of pyrophosphate, tin(II) and technetium-99m at pH 4.0 was higher than at pH 7.4. The presence of tin gave rise to an increase of the pyrophosphate adsorption that was much larger than can be accounted for by a stoichiometric adsorption of tin-pyrophosphate. It is concluded that tin and technetium are bound as negatively charged complexes with pyrophosphate. Finally it is argued that the fraction of the bone scanning agent that reaches the bone surface is adsorbed completely by the mineral phase.     

60Co aqueous speciation and pH effect on the adsorption behavior on inorganic materials.

The adsorption of radioactive cobalt from aqueous solution on MgO, MnO(2), TiO(2), SnO, activated carbon and calcined hydrotalcite was studied under static conditions as a function of pH (1, 3, 5, 7, and 10) of the (60)Co solution. It was found that under the experimental conditions, (60)Co was significantly adsorbed on MnO(2), TiO(2) and activated carbon and in smaller quantities on MgO, SnO and calcined hydrotalcite. The adsorption of (60)Co species on MgO, MnO(2), TiO(2) and SnO can be attributed to the direct exchange of ions with a specific group on the adsorbing surface, in accordance with the concept of zero point charge (zpc). The radionuclide content was determined by gamma-spectrometry. The (60)Co chemical species present in aqueous solutions with different pH values were surveyed by using high-voltage electrophoresis. It was also found that (60)Co was present only as a cationic species at pH 1, 3, 5 and 7 and a neutral species at alkaline pH.     

Biosorptive behaviour of Mango (Mangifera indica) and Neem (Azadirachta indica) bark for Hg2+, Cr3+ and Cd2+ toxic ions from aqueous solutions: a radiotracer study

Biosorption of Hg²⁺ and Cr³⁺ on dead biomass Mango (Mangifera indica) and Neem (Azadirachta indica) bark has been assessed at micro to tracer level concentrations from aqueous solutions employing the `radiotracer technique'. A high level of uptake of metal ions on these solid surfaces occurs within ca. 4 h of contact time reaching apparent saturation. The increase of sorptive concentration (10⁻⁸ to 10⁻² mol dm⁻³), temperature (293–323 K) and pH (ca. 3 to 10) favoured the removal process of these ions; but in the case of Hg²⁺ on Neem bark, there was seemingly no temperature effect. The uptake process follows first order rate law and obeys the Freundlich adsorption isotherm. Added anions and cations in the bulk solution inhibit to some extent the removal of these toxic ions. Similarly the inhibition in the uptake was also observed when both biomasses were irradiated by neutron and γ-rays prior to being employed as sorbents. No significant sorption of Cd²⁺ was observed on these dead biomass solid surfaces under various physical–chemical conditions.     

Adsorption of Se species on crushed granite: a direct linkage with its internal iron-related minerals.

The adsorption of selenium species on crushed granite is investigated directly linking to its internal iron-related minerals. Experimental results demonstrated that granite has higher affinity toward Se(IV) adsorption than Se(VI) adsorption. Se(IV) adsorption on granite is insensitive to background electrolytes while the effect of ionic strength on Se(VI) adsorption is not observed, which is attributed to the overloading of Se(VI) ions. Results of chemical sequential extraction showed that the removal of crystalline iron oxides dramatically reduces Se(IV) adsorption, which corresponds to the disappearance of goethite signal within XRD pattern. Based on our results, it is proposed that goethite within granite dominates Se adsorption in crushed granite. Although these goethites probably stem from some sample preparation processes including drilling in situ, crushing, washing and drying granite samples in laboratory, the formation of goethite enhances the granite affinity toward Se species adsorption. Images of SEM/EDS furthermore revealed that goethite is embedded within the fractures. In addition, quantification by standard addition method by spiking goethite suspension indicates that only around 20% of goethite minerals are available during Se(IV) adsorption.     

Adsorption of 241Am and 226Ra from natural water by wood charcoal.

The adsorption of (241)Am and (226)Ra from natural water by a granulated wood charcoal was investigated as a function of the solution pH, in the range 4-10, and of the water flow, in the range 3.5-42 cm(3)/min. The percentage adsorption of (241)Am (fairly constant at >80% for all pHs) was greater than that of (226)Ra (which increased with increasing pH from approximately 40% up to >80%). The results are explained by considering the different species of each radionuclide present at the pH values of the solution at the end of the adsorbent column, and the pH of the point of zero charge of the adsorbent. At pH 6, the elimination of (241)Am from natural water was independent of the water flow, while the elimination of (226)Ra declined linearly as the flow rate was increased.     

酰胺功能化石墨烯纳米带对铀的吸附性能研究

目的 制备酰胺功能化石墨烯纳米带（GONRs-AM）并研究其对铀的吸附性能。方法 对所制得的GONRs-AM进行扫描电镜（SEM）和傅里叶红外光谱（FT-IR）表征,并通过批处理吸附实验考察了溶液pH、吸附剂用量、吸附时间、铀初始浓度、温度和离子强度等因素对GONRs-AM吸附铀的影响。结果 GONRs-AM对铀的最大吸附容量为294.5 mg/g,该吸附过程是受pH影响的,自发的放热过程,并符合准二级动力学模型和Langmuir模型。结论 GONRs-AM对铀的吸附性能较好,可用于放射性废水中吸附分离铀。     

Ion exchangers in radioactive waste management. Part XI. Removal of barium and strontium ions from aqueous solutions by hydrous ferric oxide.

The uptake of Ba(II) and Sr(II) by hydrous ferric oxide (HFO) was studied as a function of contact time, concentration, temperature and pH of the respective adsorptive solutions employing the 'radiotracer technique'. The uptake of both the ions was found to increase with the increase in concentration, temperature and pH of the adsorptive solutions. Concentration dependence data fitted well to the Freundlich adsorption isotherm over the entire range of concentration (10(-2)-10(-7) M) and the uptake process followed first-order rate kinetics. The desorption experiments demonstrate the irreversible nature of the uptake process, however, in the presence of H+ ions, i.e. on acidification, an appreciable amount of metal ions were removed in the bulk solution. The radiation stability of hydrous ferric oxide towards the uptake of Ba(II) and Sr(II) was also examined by using samples of hydrous ferric oxide irradiated by neutrons and gamma-rays prior to be employing as sorbents. The presence of some mono- and divalent co-ions along with the studied ions suppressed their removal appreciably.     

Model Studies for the Direct Effect of High-energy Irradiation on DNA. Mechanism of Strand Break Formation Induced by Laser Photoionization of Poly U in Aqueous Solution

Summary

Laser flash photolysis of polyuridylic acid (poly U) in anoxic aqueous solutions leads to biphotonic photoionization of the uracil moiety followed by the formation of single strand breaks (ssb). The rate constant for ssb formation (1·0 s^?1, obtained from the slow component of conductivity increase at 23°C and pH 6·8) increases with decreasing pH to 235 s^?1 at pH 3·5. The activation energy (pre-exponential factor) was measured to be 66 kJ mol^?1 (5 × 10¹¹ s^?1) at pH 6·8. Addition of dithiothreitol (DTT) or glutathione (GSH) prevents ssb formation by reacting with a poly U intermediate (rate constant = 1·2 × 10⁶ and 0·16 × 10⁶ dm³ mol^?1 s^?1, respectively). Since with OH radicals as initiators very similar data have been obtained for the kinetics of ssb formation and for the reaction with DTT, we conclude that photoionization of the uracil moiety in poly U leads eventually to the same chemical pathway for ssb formation as that induced by OH radicals. Furthermore, we propose that protection by DTT and GSH occurs via H donation to the C-4′ radicals of the sugar moiety of DNA and to the C-4′ and the C-2′ radicals of poly U.     

Effect of exogenous thyroxin on renal ion-regulating and acid-secreting functions in white rats

Experimental hyperthyreosis was stimulated by intraventricular injections of sodium solithyroxin (T4) suspension on 1% starch gel during 10 days at a dose of 10 microg/100 g of body mass (n = 15) or 20 microg/100 g of body mass (n = 15). Renal function was tested by 5 % water loading after 24 hrs. since the last T4 injection. Urine and blood plasma samples were analyzed for creatinine; in addition, urine was analyzed for sodium and potassium ions of titrated acids, ammonium cations, and pH. Thyroxin was found to decrease creatinine clearance and expedite renal excretion of sodium and potassium ions irrespective of the amount of exogenous T4; at the same time, exaggerated excretion of titrated acids and ammonium cations correlated with T4 dose.     

Effect of changing visual condition and frequency of horizontal oscillations on postural balance of standing healthy subjects

The goal of this study was to describe the movement pattern of the body-segment rotations of healthy subjects in the horizontal plane while they were standing on a supporting platform that imposed steady sinusoidal horizontal rotations under three visual conditions: (a) eyes closed with no instructions (EC–NI), (b) eyes open with instructions to gaze at a stationary black dot located at eye level on a wall surface about four meters in front of them (EO–WI), and (c) eyes closed with instructions to imagine looking at the same target (EC–WI). The selected input signal was a sinusoid with an amplitude of ±45 deg at different frequencies equal to 0.25, 0.50 and 0.75 Hz, which were referred to as L, M and H. Bipedal balance measurements were taken in 10 adult subjects (mean age 30 ± 9 years; three men and seven women).Subjects’ kinematics were analyzed with an optoelectronic system. Under the three visual conditions, the movements of the pelvis, the trunk, and the head decreased and were inversely dependent on platform frequency; specifically, both the head and the trunk decreased their gain rotation of about 1.8–2.9 times from L to H, while the pelvis decreased its by about 1.3 times. However, the arm oscillations showed a gain and phase tendency opposite to that of the other body segments, with the gain rotation having increased of about 1.8–3.7 times from L to H.Comparing the three visual conditions, the finding suggests that the subjects were able to stabilize their head as a reference frame to maintain postural balance in a similar way under the EC–WI and EO–WI conditions. Instead, in the EC–NI trials, the subjects compensated less, in particular at the hip, the external perturbation producing higher absolute body rotations and lower relative body rotations. In fact, the head rotation was about four and three times the one showed in EC–WI and EO–WI, while for the trunk and the pelvis it was always equal to two and 1.5 times the correspondent rotation observed under the WI conditions. These results provide a quantitative assessment of compensatory balance reactions in healthy subjects to periodical horizontal perturbations.     

Ion exchangers in radioactive waste management—V. A case of efficient removal of Ba(II) from aqueous solutions by TiO2 powder—radiotracer study

The adsorption behaviour of Ba(II) on titanium(IV) oxide in an aqueous solution was studied by means of batch technique as a function of Ba(II) concentration, temperature and solution pH using Ba-140 as radiotracer. The results show that adsorption is essentially complete in ca 2 h and that the steady state values of adsorption at various concentrations agree well with the classical Freundlich isotherm and follow first order kinetics. The pH and temperature of the solution markedly affect the extent of adsorption. The nature and mechanism of adsorption are discussed.     

Effects of 30-h sleep loss on cardiorespiratory functions at rest and in exercise

The effects of 30-h sleep deprivation on cardiorespiratory function either at rest or in exercise were studied in 15 young healthy male volunteers. All subjects performed 1-min incremental exercise tests on a bicycle ergometer until exhaustion and endurance exercise tests at 3/4 of their maximal work rates. Arterialized venous blood samples were withdrawn at rest and during exercise tests to investigate the influence of sleep loss on blood gases. In addition, resting plasma catecholamine levels were also measured in ten subjects. The results showed that 1) resting heart rate, plasma catecholamine levels, and blood pH were decreased while minute ventilation (VI) and CO2 production (VCO2) were increased after 30 h of sleep loss (P less than 0.05), and 2) the maximal exercise performance was reduced by sleeplessness, as indicated by the decreases in the maximal heart rate, peak VI, peak VCO2, peak O2 consumption, and time to exhaustion (P less than 0.05). However, no significant changes in exercise endurance, arterialized venous pH, and PCO2 were found in exercise after sleep deprivation either. We therefore conclude that 30-h sleep loss alters cardiorespiratory function at rest and the ability to perform maximal exercise but not exercise endurance.     

人源汉坦病毒H8205株S基因NP编码区的序列测定及其NP强抗原性的分子生物学分析

目的：确定人源汉坦病毒Ｈ８２０５株在汉坦病毒属中的分类地位及找出其核衣壳蛋白（ｎｕ－ｃｌｅｏｃａｐｓｉｄ,ＮＰ）强抗原性的分子生物学基础。方法：采用半套式ＲＴ－ＰＣＲ扩增Ｈ８２０５Ｓ基因核衣壳蛋白（ＮＰ）编码区,克隆于载体ｐＢＶ２２０中并进行序列测定,测序结果用ＰＣＧＥＮＥ分析。结果：Ｈ８２０５株Ｓ基因ＮＰ编码区为１２９０ｂｐ（含两端引物序列）,与７６－１１８株核苷酸的同源性为８３．０％,氨基酸的同源性为９６％;ＮＰ的亲水性结构图与７６－１１８株的相似,但３个最高峰不同,Ｈ８２０５株的ＮＰ在Ｎ端有一个高度亲水性结构中心,计算机分析预测此区为一个非常强的抗原决定簇。结论：本研究从分子生物学角度证实Ｈ８２０５为ＨＴＮ型,Ｈ８２０５株ＮＰ强抗原性和免疫原性可能与Ｎ端的高度亲水性结构中心有关     

Effect of soil humic and fulvic acids, pH and ionic strength on Th(IV) sorption to TiO2 nanoparticles.

Thorium is considered as a chemical analog of other tetravalent actinides. Herein, the sorption of Th(IV) on TiO(2) in the presence or absence of soil fulvic acid (FA)/humic acid (HA) as a function of pH, ionic strength and FA/HA concentration has been studied by a batch method. The morphology was characterized by scanning electron microscopy (SEM). The results indicate that sorption of Th(IV) on TiO(2) increases from 0% to approximately 94% at pH 1 approximately 4, and then maintains level with increasing pH values. Both FA and HA have a positive effect on Th(IV) sorption at low pH values and the contribution of FA on Th(IV) sorption is rather higher than that of HA at pH<4. The sorption is weakly dependent on the concentration of KNO(3) in solution, but the cations K(+), Na(+) and Li(+) influence Th(IV) sorption more obviously. The batch results indicate that the inner sphere complex formation is formed at bare surfaces or FA/HA-bound TiO(2) particle surfaces. Results of SEM analysis show that the particle sizes of TiO(2), Th-TiO(2) and Th-HA-TiO(2) colloids are quite different. Surface complexation may be considered as the main sorption mechanism.