Recrystallization of 223Ra with barium sulfate

In this work, the kinetics of barium sulfate recrystallization has been studied in acidic 0.01 mol dm^?3 sodium sulfate solution using ²²³Ra and ¹³³Ba tracers at very low total radium concentration, i.e. less than 10^?13 mol dm^?3. It was found that the system follows the homogeneous recrystallization model and that recrystallization rates, inferred by the decrease of ²²³Ra and ¹³³Ba in the aqueous solution, are fast. Therefore, even at very low concentrations, below the solubility limit, radium will be retained by barium sulfate—a mineral present in the deep underground repository.     

Uranium ore processing: Kinetics of the growth and dissolution of a potential host solid from a model surface

As part of an investigation concerning the fate of²²⁶Ra during uranium ore milling and long-term tailings storage, we have investigated the growth of potential host solids-barium sulfate and lead sulfate-on mica, a model surface. The kinetics of dissolution of barium sulfate-and of a barium sulfate solid containing²²⁸Ra as a trace component into 10^–3M sulfuric acid were subsequently investigated using a flow-cell and radiotracer techniques. It was found that ther dissolution of both the barium sulfate host and the²²⁸Ra trace component was congruent. The dissolution reaction appears to be surface controlled.     

Determination of sulfate in river water by flow injection analysis

Sulfate ion in river water is determined by flow injection analysis at a rate of 30 samples per hour; the sulfate contents are typically less than 30 ppm. The reagent solution contains dimethylsulfonazo-III, barium chloride, potassium nitrate and chloroacetate buffer in 70% ($\text{v}\text{v}$) ethanol, and is saturated with barium sulfate. The aqueous carrier stream is also saturated with barium sulfate. The sample is filtered and treated with Amberlite IR120-B cation-exchanger before injection into the carrier stream, and the decoloration of the barium—dimethylsulfonazo-III complex by sulfate is measured at 662 nm. The calibration graph is linear over the range 0–30 μg ml^-1 for sulfate in water.     

The formation of hetero-epitaxial deposits of lead,barium and (barium/lead) sulfates on mica surfaces

As part of an investigation concerning the fate of²²⁶Ra during uranium ore milling and long-term tailings storage we have grown hetero-epitaxial deposits of barium sulfate, lead sulfate and mixed barium/lead sulfate on mica surfaces. The deposits formed readily on the substrate from supersaturated aqueous solutions of the parent ions and may be strongly adherent. Calcium sulfate formed deposits on mica at very much greater levels of supersaturation than lead or barium sulfate.     

The formation of hetero-epitaxial deposits of lead,barium and (barium/lead) sulfates on quartz surfaces

As a continuation of an investigation concerning the fate of²²⁶Ra during uranium ore milling and long-term tailings storage we have grown hetero-epitaxial deposits of barium sulfate, lead sulfate and mixed barium/lead sulfate on sawn quartz surfaces of differing crystallographic orientations. The deposits formed readily on the substrate from supersaturated aqueous solutions of the parent ions and appear to be strongly adherent. Calcium sulfate formed deposits on quartz at very much greater levels of supersaturation than lead or barium sulfate.     

Solubility and solubility constant of barium sulfate in aqueous sodium sulfate solutions between 0 and 80°C

The solubilities of barium sulfate in aqueous solutions of sodium sulfate were studied at ionic strengths from 0.0005 to 0.02 mol-kg^–1 and at 0, 20, 40, 60, and 80°C. The solubility data were used to calculate the solubility constants using an extrapolation method. The solubility constant obtained were in good agreement with literature data. The mean activity coefficients of barium sulfate in aqueous solutions of sodium sulfate were also studied.     

Radiometric determination of sulfate

A radiometric procedure for the determination of sulfate based upon the precipitation of barium sulfate is described with a sensitivity of about 0.01 μg/ml. Carrier-free³⁵SO₄ is added to the sample to measure the chemical recovery. The sulfate is precipitated with an excess of barium having a known specific activity of¹³³Ba. The amount of¹³³Ba determined by gamma counting is directly related by stoichiometry to the amount of sulfate in the precipitate.     

Morphology and internal structure of barium sulfate--derivation of a new growth mechanism

Particle formation is the decisive step to control crystal morphology. Besides the classical primary processes, nucleation and molecular growth, the particle size can also increase by aggregation. The special case of self-assembled aggregation leads to the formation of highly ordered particles which often possess a porous internal structure. In the experiments of these studies the particle formation of barium sulfate has been investigated. SEM analysis shows a large variety of growth forms including plate-like, star-like, and spherical particles, whereas TEM exposures reveal the porous internal structure at all investigated supersaturation levels. The pore size and the volume fraction can be influenced by changing the supersaturation ratio. By means of a fast sampling technique in combination with cryo-TEM analysis it has been shown that the particles at the early stages of growth shortly after the beginning of nucleation consist of many small nanocrystallites which have aggregated in a highly ordered manner. The diffraction pattern indicates many small-angle grain boundaries, whereas the particles at the end of the precipitation process are monocrystalline. This leads to the conclusion that barium sulfate grows according to a self-assembled aggregation mechanism followed by a fast recrystallization process.     

Barium Sulfate Effects on the Electrochemical Behaviors of Nanostructured Lead Dioxide and Commercial Positive Plates of Lead-Acid Batteries

Positive electrode with uniform lead dioxide nanostructures directly synthesized by cyclic voltammetry (CV) method on the lead substrate in 1 M sulfuric acid solution including different concentration of barium sulfate. The effect of potential scan rate, sulfuric acid and barium sulfate concentration were studied on the morphology and particle size of lead dioxide using scanning electron microscopy (SEM) and X-ray diffraction techniques (XRD). The effect of barium sulfate was studied on the CV parameters including anodic peak current (I _p^a), cathodic peak current (I _p^c), anodic peak potential (E _p^a) and cathodic peak potential (E _p^c) during synthesis process. Finally, the effect of barium sulfate on the discharge capacity and cycle life of nanostructured positive electrodes and commercial positive plates was investigated. Both CV and battery test results showed that barium sulfate with concentration of 1 × 10⁻⁵ M can be used as suitable additive for positive paste of lead-acid batteries.     

Potentialities of fibrous ion-exchange materials in the determination of sulfate ions by color reactions of barium with organic reagents on a solid phase

The possibility of the determination of sulfate ions with the use of fibrous materials filled with ion exchangers on the basis of color reactions of barium with the organic reagents Arsenazo III, Orthanilic B, and Orthanilic K on a solid phase was examined. A polyacrylonitrile fiber filled the cation exchanger KU-2; anion exchangers AB-17, A-5, ANKF-211, and EDE-10p; and polyampholyte ANKB-50 (PANV-ANKB-50) was used as the support. The study of the different techniques of the sorption of the reaction components demonstrated the efficiency of the two systems involving PANV-ANKB-50. The determination of sulfates is possible because of the sorption of the excess barium remaining after the reaction with sulfate ions in the solution and its detection on the solid phase with a solution of Arsenazo III or the detection of the excess barium remaining after the interaction with the solution of sulfate ions on the solid phase with a solution of Orthanilic K. The calibration plots are linear in the concentration range of sulfate ions 10^?4–10^?5 M.     

磷酸二氢铵转化法测定硫酸钡含量

针对目前重晶石中硫酸钡含量测定方法研究不多、进展缓慢的问题,提出了一种对重晶石预处理后测定硫酸钡的方法,采用磷酸二氢铵与重晶石在700℃发生复分解反应,将不溶于水且不溶于酸的硫酸钡转化为可溶于酸的磷酸钡盐,最后依据确定的磷钡比关系,根据总磷含量间接得到钡含量。实验结果表明,磷酸二氢铵与硫酸钡的物质的量之比为2.0,并在700℃的条件下高温煅烧,可使硫酸钡全部转化完全,形成偏磷酸钡,再经过氢氧化钠、双氧水处理,转变为正磷酸氢钡并溶于盐酸中,与喹钼柠酮试剂形成磷钼酸喹啉沉淀,根据沉淀质量可准确计算出样品中硫酸钡的含量。测定的结果准确、方法可行。对测定重晶石中硫酸钡的含量提出一种新的思路和解决方案,具有实际意义。     

Synthesis of Barium Sulfate Nanoparticles in Water-in-Oil Microemulsion Systems

Micellar solutions of poly(ethylene glycol) octylphenyl ether and n-hexyl alcohol in cyclohexane were used to study the formation of water-in-oil microemulsion system and to synthesize barium sulfate nanoparticles. Barium sulfate particles (the average diameter is 10 nm) were obtained by mixing two microemulsion systems containing Ba²⁺and SO^2– ₄ions. It was shown that the sizes of BaSO₄particles measured by the dynamic light scattering and electron microscopy are in good agreement with each other.     

New metallochromic indicator for barium: Determination of sulfate in water and soil extracts

A new metallochromic indicator for barium, Orthanilic NM, is synthesized and proposed. The color reaction of Orthanilic NM with barium ions is compared with the reactions of carboxyarsenazo and other orthanilic group reagents, such as Orthanilic K, nitchromazo, etc. The quantitative characteristics of the reactions are determined. It is shown that Orthanilic NM can be used for the titrimetric (down to 20 mg/L) and photometric (down to 0.2 mg/L) determinations of sulfate. Substantial amounts of conventional anions, alkali, alkaline-earth, and nonferrous metals do not interfere with the titrimetric determination (at pH 2.5). For the photometric determination, a 1:1 Ba²⁺-Orthanilic NM complex is used at pH 2. In these conditions, sulfite and phosphate do not interfere with the determination either. Procedures are developed for the determination of sulfate in various types of water and soil extracts. Examples of their practical application are given.     

Nanoparticle precipitation in reverse microemulsions: particle formation dynamics and tailoring of particle size distributions

In this work, a detailed experimental analysis of the nanoparticle formation dynamics and the formation mechanism in a reverse microemulsion system is given. The precipitation of barium sulfate nanoparticles inside microemulsion droplets is investigated at the molecular scale with respect to the evolution of the particle size distribution and the particle morphology by an extensive transmission electron microscope (TEM) analysis. Different mixing procedures (feeding strategies) of two reactants, barium chloride and potassium sulfate, are evaluated concerning their ability for a tailored particle design under consideration of the complete particle size distribution (modality and polydispersity). It is shown that improved knowledge about the particle formation mechanisms, the dynamics, and the influence of the colloidal microemulsion structure could be used for a tailored design of particles,for example, controlled synthesis of nanoparticles with a bimodal particle size distribution by the application of a sophisticated feeding strategy.     

Barium Sulfate Nanoparticles as a Coating for Solid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons in Aqueous Samples

Owing to the high toxicity of polycyclic aromatic hydrocarbons (PAHs) and their low content in the environment, the development of efficient analysis methods is very important. In this work, an extraction tube was developed through filling barium sulfate nanoparticle-coated basalt fibers (BFs) in a poly(ether ether ketone) (PEEK) tube. According to the characterization result by scanning electron microscopy, BFs were evenly covered with barium sulfate nanoparticles, and their diameter was about 11 µm. To sensitively determine PAHs, the extraction tube was connected to a high-performance liquid chromatography instrument with diode array detector for an online enrichment and detection method. By optimizing sampling volume, sampling rate, the content of methanol in sample and desorption time, the analysis method provided a wide linear range (0.30–20 µg L^??1) and high enrichment ratio (71–2095), and was useful for the efficient detection of PAHs in environmental aqueous samples.     

The interaction of EDTA with barium sulfate

Ethylenediaminetetraacetic acid (EDTA) is a known complexing agent that interacts with a host of cations. In this paper, various techniques are used to elucidate the mechanism of interaction between EDTA and barium sulfate surfaces. It is shown that complexation with metal ions is not sufficient to explain the inhibition of barite crystallization but that other processes such as chemisorption must also occur. EDTA is shown to always adsorb as the mono-protonated species - suggesting that the molecule is able to lose a proton when it adsorbs at lower pH. Molecular modelling shows that the interaction of the surface barium ions with the carboxylate group is an important one. Finally, in situ turbidity measurements provide information about the mechanism of nucleation/growth modification. It is found that the EDTA molecule inhibits barium sulfate nucleation and that this could be its primary means of inhibiting precipitation of barium sulfate.     

A Novel Sulfate Polymeric Membrane Sensor Based on a New Bis‐Pyrylium Derivative

A novel ion‐selective polymeric membrane sensor based on pyrylium‐4,4‐(1,4‐phenylen) bis[2,6‐bis(2‐naphthyl)]‐bis[tetrafluoroborate] (PBGNB) as an excellent sensing material is successfully developed. The electrode possesses the advantages of a very low detection limit (5.0×10^?8 M), a wide working concentration range (1.0×10^?8?1.0×10^?1 M) and specially, a high sulfate selectivity over most common organic and inorganic anions. The sensor displays Nernstian behavior (slope of 29.5±0.5 mV per decade) in a wide pH range (3.0–8.5). It shows a short response time in the whole concentration range (ca. 10 s). The electrode was used as an indicator electrode in the potentiometric titration of sulfate ions with barium ions. The proposed sensor was successfully applied to the direct determination of salbutamol sulfate and paromomycin sulfate.     

Highly Selective PVC‐Based Membrane Electrode Based on 2,6‐Diphenylpyrylium Fluoroborate

A highly selective PVC‐membrane electrode based on 2,6‐diphenylpyrylium fluoroborate is presented. The electrode reveals a Nernstian potentiometric response for sulfate ion over a wide concentration range (5.0 × 10^?6‐1.0 × 10^?1 M). The electrode has a response time of about 10 s and can be used for at least 2 months without any divergence. The proposed sensor revealed very good selectivities for sulfate over a wide variety of common organic and inorganic anions and could be used over a wide pH range (2.5–9.5). The detection limit of the sensor is 3.0 × 10^?6 M. It was successfully applied to the direct determination of salbutamol, paramomycin tablets, and as an indicator electrode for potentiometric titration of sulfate ions with barium ions.     

Localization of acoustic energy in gel systems on solid-phase inhomogeneities

The thermal effects of ultrasound on an agarose gel containing nanoparticles of iron(III) hydroxide and barium sulfate are comparatively studied. The agarose matrix is shown to interact differently with iron(III) hydroxide and barium sulfate. The relative change in ultrasound absorption due to modifier particles located in the gel is estimated. The highest thermal effect is observed for systems in which modifiers are located on separate elements of the matrix bulk. Production of “containers” with ultrasound-controlled drug release on the basis of thermosensitive gels containing solid-phase inclusions is discussed as an example of possible application of the effects described.