A rapid dissolution procedure to aid initial nuclear forensics investigations of chemically refractory compounds and particles prior to gamma spectrometry

A rapid and effective preparative procedure has been evaluated for the accurate determination of low-energy (40–200 keV) gamma-emitting radionuclides (²¹⁰Pb, ²³⁴Th, ²²⁶Ra, ²³⁵U) in uranium ores and uranium ore concentrates (UOCs) using high-resolution gamma ray spectrometry. The measurement of low-energy gamma photons is complicated in heterogeneous samples containing high-density mineral phases and in such situations activity concentrations will be underestimated. This is because attenuation corrections, calculated based on sample mean density, do not properly correct where dense grains are dispersed within a less dense matrix (analogous to a nugget effect). The current method overcomes these problems using a lithium tetraborate fusion that readily dissolves all components including high-density, self-attenuating minerals/compounds. This is the ideal method for dissolving complex, non-volatile components in soils, rocks, mineral concentrates, and other materials where density reduction is required. Lithium borate fusion avoids the need for theoretical efficiency corrections or measurement of matrix matched calibration standards. The resulting homogeneous quenched glass produced can be quickly dissolved in nitric acid producing low-density solutions that can be counted by gamma spectrometry. The effectiveness of the technique is demonstrated using uranium-bearing Certified Reference Materials and provides accurate activity concentration determinations compared to the underestimated activity concentrations derived from direct measurements of a bulk sample. The procedure offers an effective solution for initial nuclear forensic studies where complex refractory minerals or matrices exist. It is also significantly faster, safer and simpler than alternative approaches.     

Investigating the kinetics of liquid-free,OSDA-free ZSM-5 zeolite synthesis from iron ore tailings

In this study, ZSM-5, which is a Mobil-type five-type zeolite with well-defined crystal morphology, is successfully synthesized via a seed-assisted, liquid-free method that uses iron ore tailings as a silica source. The ZSM-5 crystallization kinetics at 423, 433, and 443 K and different synthesis times are investigated to identify the nucleation and crystallization mechanisms of the synthesized ZSM-5 zeolites, and results suggest that the crystallization kinetics follow a Kolmogorov-Johnson-Mehl-Avrami-type behavior. The activation energies for the induction and transition periods are 112.38 and 58.35 kJ mol⁻¹, respectively. Furthermore, the Avrami exponent indicates three-dimensional crystal growth from both sporadic and instantaneous nucleation mechanisms. A comparison of our results with previous reports of the ZSM-5 crystallization mechanism demonstrates that the seed crystals play a significant role in nucleation and crystal growth. Finally, seed surface crystallization and new nuclei crystallization dual mechanism has been proposed to describe the crystallization process of ZSM-5.     

Highly efficient,economic, and recyclable glutathione decorated magnetically separable nanocomposite for uranium(VI) adsorption from aqueous solution

A green and environment-friendly magnetically separable nanocomposite, glutathione@magnetite was fabricated sonochemically through the functionalization of Fe₃O₄ by glutathione which was well characterized using Fourier-transform infrared spectroscopy, ultravoilet-visible spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometer, Brunauer-Emmett-Teller, and high-resolution transmission electron microscope. The parameters affecting adsorption including pH, temperature, contact time, initial adsorbate concentration, and adsorbent amount were optimized by batch experiments. The magnetic glutathione@magnetite was applied for the removal of uranium(VI) in water with maximum adsorption capacity found to be 333.33 mg/g in 120 min at a neutral pH at 25 °C showing high efficiency for U(VI) ions. Furthermore, adsorption results obtained from UV-vis spectroscopy were validated by inductively coupled plasma optical emission spectroscopy. The thermodynamic parameters, viz Gibbs free energy (ΔGº), standard enthalpy change (ΔHº), and standard entropy change (ΔSº) of the process were calculated using the Langmuir constants. The pseudo-second-order kinetics model is seen to be applicable for describing the uptake process using a kinetics test. Moreover, desorption studies reveals that glutathione@magnetite can be used repeatedly, and removal efficiency shows only a small decrease after six cycles. Thus, glutathione@magnetite acts as a potential adsorbent for the removal of U(VI) from the water with great adsorption performance.     

电感耦合等离子体原子发射光谱法(ICP-OES)测定铍铀伴生矿石中的铍

建立了电感耦合等离子体原子发射光谱法(ICP-OES)测定铍铀伴生矿石中的铍的方法,研究了酸溶-碱熔融法溶样过程中加入的焦硫酸钾,对ICP-OES法测定铍铀伴生矿石中的铍含量产生的基体干扰问题。主要阐述消除基体干扰的一些措施。从实验数据可知,控制称样量、焦硫酸钾加入量、定容体积和加标稀释倍数,能够有效消除焦硫酸钾对ICP-OES法测定结果的基体干扰,6次平行测定结果的相对标准偏差为3.4%,加标回收率为98.7%~104.4%,实验表明,方法准确、可靠。     

微波消解-磷钼蓝分光光度法测定钨矿石中的磷含量

针对钨矿石中的微量元素磷,采用混合酸快速微波消解结合磷钼蓝分光光度法进行测定。经选择优化样品的微波消解和实验测定条件,结果表明:HCl+HNO3+HF的混合酸微波消解后的样品,在硫酸介质中,有钼酸铵存在时,用抗坏血酸将磷还原成磷钼蓝络合物,在825nm处比色测定。方法的加标回收率为98.9%~101.6%,结果准确可靠。硅在熔样过程中挥发除去不会干扰测定,砷会干扰实验,可在酸介质中加入碘化钾,使砷还原至低价而不干扰磷的测定。     

火试金法测定铜硫矿中的金和银量的研究

本文针对铜硫矿中铜含量较高的特性,建立了适合该试样的配料比、高温熔融,金、银与铅形成合金,利用其比重悬殊与熔渣分离,将铅扣灰吹得金、银合粒,用硝酸分金,用重量法测定金量,用容量法测定银量。方法的相对标准偏差0.66%到4.78%,加标回收率96.5%到100.6%。     

锌粉-硼砂-硼酸熔融-碘酸钾滴定法测定高硅锡精矿中的锡

针对高硅锡精矿中锡的测定时通常用锌粉-氢氧化钠熔融,精密度差,不能满足分析要求的问题,建立了锌粉-硼砂-硼酸熔融,盐酸浸取,铝粒将锡还原,碘酸钾滴定法测定高硅锡精矿中锡的分析方法。方法结果稳定,精密度好,相对标准偏差在0.19%~0.55%,加标回收率在96.9%~105%。分析结果能够满足高硅锡精矿中锡的测定要求。     

Removal of uranium (VI) from nuclear effluents onto aluminophosphate and silicoaluminophosphate molecular sieves

Aluminophosphate and silicoaluminophosphate molecular sieves with both five (AFI) and eleven (AEL) type structures are synthesized by hydrothermal crystallization at 473 K, using tripropylamine and dipropylamine as a structure-directing template. The as-prepared AFI and AEL sieves are characterized and then assessed as sorbents for uranium (VI) from radioactive effluents. The sorption process is used to reduce the volumes of effluents and convert them into a stable solid waste. The batch experimental studies are carried out to evaluate the AEL and AFI structure effect on the removal of uranium. The AlPO₄-5, SAPO-5, AlPO₄-11 and SAPO-11 are applied to radioactive effluents with different activities obtained from Nuclear Research Center of Draria, Algeria. Important decontamination factor values are obtained for AFI sorbents. Thermodynamic parameters, namely, the enthalpy (ΔH), entropy (ΔS) and free energy (ΔG) for each sorption process are calculated. The collected results indicated that sorbents are effective materials for the removal of uranium (VI) ions, the sorbent with AFI structure being a highly effective material for the removal of uranium (VI) ions from nuclear effluents.     

Determination of carbonate content in barite ore by headspace gas chromatography

This paper reports a method for determining the carbonate content in barite ore using headspace gas chromatography. Based on the acidification reaction, the carbonate in the barite ore was converted to CO₂ in a closed headspace vial. When the carbonate content was significant, the pressure caused changes in the CO₂ and O₂ signals and affected the measurement accuracy. It was found that carbonate content is proportional to the intensity ratio of the CO₂ to O₂ signals. Thus, the carbonate content in barite ore can be measured indirectly using a theoretical model. The results showed that the carbonate in 3 g of barite ore sample with a particle size of 74 μm could react completely with a hydrochloric acid solution (2 mol/L) at 65°C for 5 min. The method described herein had good precision (relative standard deviation < 4.14%) and accuracy (relative differences < 6.12%). Further, the limit of quantification was 0.07 mol/L. Owing to its simplicity and speed, this method can be used for the batch determination of carbonate content in barite ore.     

Si内标-X射线衍射法定量测定铁矿中Fe3O4、Fe2O3和SiO2

铁矿物相的准确定量对矿物价值评价及选冶工艺研究有重要作用,现有化学法流程复杂效率低,X射线衍射全谱拟合法可溯源性差,结果准确性难以评价和验证。本研究建立了以Si为内标,以Cu靶X射线为辐射光源,步进扫描方式获得衍射谱图,以待测相含量为横坐标,待测相与内标相峰面积比值为纵坐标建立校准曲线,以曲线对铁矿中Fe3O4、Fe2O3和SiO2物相进行定量的方法。试验对制样条件、扫描参数、内标物选择、积分方式、重叠峰校正等进行了优化选择,结果表明,试样全部通过45 μm标准筛,Si内标比例为10%,步进长度0.01°,步进时间30S,选择对Fe3O4（311）、Fe2O3（104）、SiO2（011）和Si（111）的衍射峰进行积分强度计算,可获得最优结果。在选定工作条件下,Fe3O4在1.07～100%范围内线性相关系数(R2)为0.9953,相对标准偏差(RSD)1.1%～13.2% (n=6),加标回收率99.7 %~114.8 %,检出限(LOD)4.29%;Fe2O3在1.51～100%范围内线性相关系数(R2)为0.9991,相对标准偏差(RSD)2.8%～10.6% (n=6),加标回收率87.1%~112.2%,检出限(LOD)2.56%;SiO2在0.79～29.72 %范围内线性相关系数(R2)为0.9957,相对标准偏差(RSD)3.2%～10.3% (n=6),加标回收率86.6%~98.9%,检出限(LOD)0.68%。方法易溯源、准确性易评价和验证,适合开展标准化检测和应用。