Stepwise precipitation of barium sulphate,chromate and vanadate by cation release

Sulphate is precipitated at pH4.5–5.0 by adding Ba-EDTA complex. Chromate and vanadate are sequentially precipitated from the filtrate at pH 6–7 and 9, respectively, by adding magnesium to displace barium from its EDTA complex. The analyses are completed gravimetrically.     

Indirect automatic atomic absorption determination of sulphate based on its precipitation with barium

A continuous precipitation flame atomization atomic absorption spectrometric method for the indirect determination of sulphate is proposed. By using a reversed flow-injection configuration for precipitation as barium sulphate, this anion was determined in the range 10–150 g/ml, with a relative standard deviation of 2.6%. The sensitivity was increased by a factor of seven by using a nitrous oxide-acetylene flame to measure barium.     

Facile synthesis of monodispersed barium sulphate particles via an in situ templated process

Monodispersed BaSO4 micrometer and submicrometer sized particles were produced by a simple precipitation reaction in the presence of poly(methacrylic acid) (PMAA) at the ambient temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electron diffraction (ED) were used to characterize the obtained BaSO4 particles, and polycrystalline nature of the BaSO4 products was revealed. A "polymer-M in situ template" model was proposed to elucidate the formation process of such polycrystalline BaSO4 particles.     

Assesment of dimethyl phthalate removal from aqueous phase using barium hexaferrite containing magnetic beads

The barium hexaferrite (BaFe(12)O(19)) containing magnetic poly (ethylene glycol dimethacrylate-vinyl pyridine; mag-poly [EGDMA-VP]) beads (average diameter=53-212 μm) were synthesized and characterized. Their use as an adsorbent in the removal of dimethyl phthalate (DMP) from an aqueous solution was investigated. The mag-poly (EGDMA-VP) beads were prepared by copolymerizing of 4-vinyl pyridine (VP) with ethylene glycol dimethacrylate (EGDMA). The mag-poly (EGDMA-VP) beads were characterized by N(2) adsorption/desorption isotherms (BET), vibrating sample magnetometer (VSM), X-ray powder diffraction (XRD), elemental analysis, scanning electron microscope (SEM), and swelling studies. At a fixed solid/solution ratio, the various factors affecting the adsorption of DMP from aqueous solutions such as pH, initial concentration, contact time, and temperature were analyzed. The maximum DMP adsorption capacity of the mag-poly (EGDMA-VP) beads was determined as 96.2 mg/g at pH 3.0, 25 °C. All the isotherm data can be fitted with both the Langmuir and the Dubinin-Radushkevich isotherm models. The pseudo-first-order, pseudo-second-order, Ritch-second-order, and intraparticle diffusion models were used to describe the adsorption kinetics. The thermodynamic parameters obtained indicated the exothermic nature of the adsorption. The DMP adsorption capacity did not change after 10 batch successive reactions, demonstrating the usefulness of the magnetic beads in applications.     

Electrospun polystyrene nanofibers as a novel adsorbent to transfer an organic phase from an aqueous phase

The aim of this work is to develop a simple phase‐transfer method for dispersive liquid–liquid microextraction. For this purpose, a polystyrene nanofiber was prepared by a facile electrospinning strategy and used for the first time as an adsorbent to transfer the organic phase in dispersive liquid–liquid microextraction procedure. The fiber was characterized and its chemical stability and excellent hydrophobicity enable it to selectively adsorb the organic solvent in an aqueous sample. High porosity and specific surface area provide a large adsorption capacity. Under the optimal conditions, the developed dispersive liquid–liquid microextraction with high‐performance liquid chromatography method was successfully applied to the analysis of aldehydes in environmental water samples. The merits of this approach are that it is easy‐to‐operate, low‐cost, time‐saving, and has satisfactory sensitivity. It provides an alternative way for fast and convenient phase transfer of the hydrophobic organic solvent from the aqueous phase.     

Electron microscope investigation of the thermal aging of barium sulphate precipitates

Barium sulphate precipitates, formed by four different analytical methods, dried and ignited at different temperatures, have been examined with an electron microscope. The study of the dissolution of precipitates has been found useful for the investigation of thermal aging. On heating the precipitates, diffusion, which takes place at temperatures depending on structure, permits structural changes such as reordering to take place. Consequently, the structure of the ignited precipitates approaches the ideal arrangement.     

Bioligand-mediated partitioning of radionuclides to the aqueous phase

The aqueous-phase partitioning of ⁵⁹Fe, ¹⁴⁷Pm, ²³⁴Th and ²⁴¹Am by complexing compounds from subsurface bacteria has previously been studied in the presence of quartz sand. In this study the aqueous-phase partitioning of pico-to submicromolar amounts of ⁵⁹Fe, ¹⁴⁷Pm, ²³⁴Th and ²⁴¹Am was analyzed in the presence of TiO₂ and exudates from three species of subsurface bacteria: Pseudomonas fluorescens, Pseudomonas stutzeri, and Shewanella putrefaciens. All were grown under aerobic conditions and P. stutzeri and S. putrefaciens were grown under anaerobic conditions as well. The supernatants of the aerobic and anaerobic cultures were collected and radionuclide was added. TiO₂, with BET surface area of 49.9 m²·g⁻¹, was added to the supernatant radionuclide mix, and the pH was adjusted to approximately 8. After incubation, the amount of radionuclide in the liquid phase of the samples and controls was analyzed using scintillation method. Two types of values were calculated: solution% = the activity maintained in solution relative to the total activity, and Q-values = the quotient between the activity in samples and the activity in controls. Aerobic supernatants had solution% values between 89% and 100% for ⁵⁹Fe and between 18 and 43% for ²³⁴Th. The solution% values for ²⁴¹Am and ¹⁴⁷Pm were less than 2% overall, but the Q-values were between 34 and 115 times more ²⁴¹Am in bacterial supernatants than in controls. The corresponding values for ¹⁴⁷Pm ranged from 6 to 20 times more than in the control. The solution% values for all elements in the presence of anaerobic supernatants were below 2%, but the Q-values clustered around 7 for ⁵⁹Fe and ranging from 2 to 29 for ^234Th, indicated that anaerobic supernatants partitioned these elements to the aqueous phase. Both aerobic and anaerobic supernatants tested positive for complexing compounds when analyzed, using the Chrome Azurol S assay. Complexation with excreted organic ligands is most likely the reason for the higher amounts of metals in samples than in the controls. Hence, aerobically and anaerobically excreted organic ligands seem able to influence the mobility of radionuclides in aerobic and anaerobic environments contaminated with these compounds.     

AloeVera as an effective biosorbent for the removal of thorium and barium from aqueous solutions

Journal of Radioanalytical and Nuclear Chemistry - The use of three biosorbents based on AloeVera wastes for the removal of thorium and barium from aqueous solutions (Cinit:...     

Structure of liquid films of an ordered foam confined in a narrow channel

A bamboo foam is the simplest case of an ordered foam confined in a narrow channel. It is made of a regular film distribution, arranged perpendicularly to the channel. Our work consists of studying the structural properties of several films taken in a drained foam. X-ray experiments highlighted the equality of the equilibrium thickness for each film within a foam. The same thickness was found as by measurements of disjoining pressure isotherms, proving as well that films of a bamboo foam behave like isolated ones. The refinement of X-ray data by a simple model of specular reflectivity showed a significant variation of the electronic distribution of the surfactant layer for a common black film forwarding from one equilibrium state to another. A discussion on the organization of the surfactant molecules to the gas/liquid interface and film is proposed.     

Spectrophotometric determination of chloride in barium sulphate precipitates following isolation of the analyte

A spectrophotometric method was developed for the determination of chloride concentrations between 0.2 and 5 mgL^?1 in barium sulphate precipitates, obtained by precipitation of sulphate in concentrations of 50 to 250 mgL^?1 or even lower. The proposed method involves prior dissolution of the barium sulphate precipitate in hot conc. sulphuric acid and collection of the released hydrogen chloride by means of gaseous nitrogen. The analytical calibration function was obtained by the least-squares procedure from 10 determinations at each of three concentration levels of a standard solution of chloride. The lack of fit of experimental points to the least-squares straight line was found to be negligible at a significance level of 5%. Blank measurements were required in all instances as the blank absorbance varied with time.     

Antisolvent precipitation of hydrophobic functionalized multiwall carbon nanotubes in an aqueous environment

The possibility of antisolvent precipitation of hydrophobic, organic soluble functionalized carbon nanotubes (f-CNTs), where water acts as an antisolvent is presented. Octadecylamine functionalized multiwall carbon nanotubes (MWCNT-ODA) was used as the model compound and was found to form highly stable dispersions in different water/solvent systems, and the particle sizes ranged from 170 to 400 nm. Colloidal behavior was studied using dynamic light scattering and particle aggregation was found to increase with the addition of electrolytes, with tetrahydrofuran (THF) and ethanol showing the maximum effect. The aggregation behavior of the antisolvent precipitated system did not follow the conventional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which was different from what has been reported previously for hydrophilic, water soluble f-CNTs. Based on this study, it is evident that hydrophobic f-CNTs are potential water pollutants.     

Radioanalytical monitoring of the formation of barium sulfate in aqueous solutions

The formation of barium sulfate in aqueous media causes problems of insoluble scale formation. On the other hand, the coprecipitation of uranium and transuranium elements with barium sulfate has been suggested for the determination of these elements in environmental monitoring processes. Therefore, the study of barium sulfate crystal growth is required. The investigations done so far suffer from the low sensitivity of the analytical methods used. In the present work we have overcome this problem by using¹³¹Ba for the preparation of supersaturated solutions. Thus kinetics parameters such as induction time and precipitation rates were measured. The polynuclear mechanism was found to be operative at high and the spiral growth at low supersaturations.     

A contribution to the use of thorin as an analytical reagent: spectrophotometric study of its complexation with barium and application to sulphate determination in atmospheric particulates

The complexation of Ba(2+) by Thorin in the pH range 2-9 in aqueous ethanol medium has been investigated. The dissociation constants of Thorin in the ethanolic medium have been determined spectrophotometrically and the distribution of the protonated species has been used to explain the behaviour of the apparent complexation constant. On the basis of the apparent constants found, and mass-balances, the effect of sulphate on the absorbance has been calculated, and the best conditions for determination of sulphate have been established. Cation and anion interferences have been studied and means of overcoming them are proposed. The method developed has been applied to sulphate determination in atmospheric particulates. As little as 1 mug of sulphate can be measured.     

Amperometric study of some effects in the precipitation of lead and barium chromates

Amperometric titration has been applied to study parameters determining the extent of mutual co-precipitation of lead and barium in the formation of their chromates. The anomalous behaviour of dichromate due to repulsion at the dropping mercury electrode, which severely affects the precision of the measurements, has been eliminated by addition of tetrabutylammonium hydroxide. By this modification the amperometric end-point detection has been extended to higher concentrations of the reagent and a wider pH range of the medium as required for this study. Shifts in the distribution of chromium species, slow evolution of the precipitate and, in the case of lead, its varying composition, all depend on pH and ionic strength. They have been identified as limiting factors in the amperometric titration of lead and barium and optimum conditions found for their determination. The applicability of the technique to practical analysis is limited, but in the absence of ions which precipitate at the required pH, it permits precise and accurate titration of lead in the presence of barium at pH 2-3 and of their sum at pH 5-6.     

Characterization of barium sulphate as a TLC material for the separation of plant carboxylic acids

Summary A mixture of barium sulphate and calcium sulphate has been shown to be a good TLC material for the detection and the quantification of a variety of carboxylic acids known to be plant growth regulators and carboxylic acids of importance in the citrus fruit industry.     

Optimization of the precipitation of Plantaglyutsid from evaporated aqueous extracts

The optimization of one of the stages of the technology of Plantaglyutsid — its precipitation from the evaporated aqueous extract with ethanol — has been optimized by the methods of mathematical statistics. Information has been obtained on the optimum parameters for performing the process with the aim of achieving the maximum yield of preparation and lowering the consumption of raw material.Tashkent Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 312–315, May–June, 1985.     

Electrostimulated shift of the precipitation temperature of aqueous polyzwitterionic solutions

The precipitation temperature (T_pr) value of aqueous poly(dimethylamino-ethoxyacryloyl-propylsulphonate) (PDMAPS) solutions decreases with the rise of electric field intensity both in the absence and in the presence of a low molecular salt. This electrostimulated T_pr shift is explained qualitatively by means of the model taking into account both the dominating intermacromolecular dipole-dipole interaction and the dipole cluster formation.     

A novel barium polymeric membrane sensor for selective determination of barium and sulphate ions based on the complex ion associate barium(II)-Rose Bengal as neutral ionophore

A simple, long life, rapid response and sensitive barium(II)-PVC membrane sensor that typically follows Nernstian behavior has been developed for the assay of barium(II) ions. The developed sensor has been made by incorporating the complex ion associate of barium(II)-Rose Bengal (Ba-RB) as an ionophore into a plasticized PVC matrix. The sensor is stable and exhibited fast potential response of 20 s and gave a good linear response with a Nernstian slope of 28.5 ± 0.4 mV/decade of activity within the concentration range 5 × 10⁻⁵ to 10⁻¹ M over a wide range of pH 4.5-10.0 for barium(II) ions. The developed sensor showed comparatively good selectivity for barium(II) ions with respect to other alkali, alkaline earth, transition and heavy metal ions. The plasticizer o-nitrophenyloctyl ether controlled significantly the calibration slope and the lifetime of the fabricated sensor. The proposed sensor was used successfully for the analysis of barium(II) ions in wastewater samples and in lithophone pigment with excellent recovery percentages in the range 98.9-99.8 ± 1.6%. The determination of sulphate in fresh and potable water samples with the developed sensor has been also achieved successfully. The described sensor provides a reliable means with good correlation with the data obtained by atomic absorption spectrometry (AAS) and other spectrophotometric methods for the analysis of trace amounts of barium(II) and/or sulphate ions in different matrices.     

Application of an electrochemical membrane reactor to the thermochemical water splitting IS process for hydrogen production

The Bunsen reaction (SO₂ + I₂ + 2H₂O = H₂SO₄ + 2HI) in the thermochemical IS process to produce hydrogen was successfully employed using an electrochemical membrane reactor. H₂SO₄ and HI were concentrated in the anode side and the cathode side of the reactor, respectively. I₂ is the dominant bulk of the recycling chemicals in this process, and I₂ concentration at the outlet of the reactor was reduced ca. 93% by using this technique. The electric energy consumption for the reaction was about 50% smaller by reducing the concentration of I₂ indicating that the IS process can be operate efficiently at low I₂ concentration. The reaction was carried out for 4 h, and the HI concentration was increased by 26%. This amount was the same within 10% as the values calculated from the total loaded electricity. In order to decrease the overpotential at the anode side, small amount of HI was added to the anode side solution. The total voltage was reduced by 0.03 V by the addition of HI.