Barium ion cross-linked alginate beads have shown great affinity to toxic hexavalent chromium ions in aqueous solution, in contrast to the traditionally used calcium alginate beads. Our adsorption experiments were carried out by the batch contact method. The optimal pH for removal was found to be pH 4. The equilibrium was established in 4 h, and the removal efficiency of chromium (VI) was found to be 95%. The adsorption data were applied to Langmuir, Freundlich, Dubinin–Redushkevich (D–R), and Temkin isotherm equations. Both Langmuir and Freundlich isotherm constants indicated a favorable adsorption. The value of mean sorption energy calculated from D–R isoterm indicates that the adsorption is essentially physical. The high maximum chromium (VI) adsorption capacity was determined from the Langmuir isotherm as 36.5 mg/g dry alginate beads. The chromium (VI) adsorption data were analyzed using several kinetic models such as the pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models, and the rate constants were quantified. Our study suggests that barium alginate beads can be used as cost-effective and efficient adsorbents for the removal of chromium (VI) from contaminated waters.

In this study, lactic acid production by repeated batch fermentation using cell entrapped methods was compared. Barium alginate beads, agar gel and polyurethane foam cubes were employed as carriers to immobilize Lactobacillus casei subsp. casei for the purpose of L (+)-lactic acid production. Increasing concentrations of lactic acid during fermentation were better tolerated by barium alginate entrapped cells. Alginate beads had a considerable effect on lactic acid production and reduced the fermentation time by half. The volumetric productivity with barium alginate and agar immobilized cells were 0.625 and 0.425 (g/lh) respectively, whereas it was 0.375 (g/lh) for conventional free-cell fermentation. Beside biocompatibility, barium alginate immobilized cells exhibited good mechanical strength during repetitive fermentations and could be used in repetitive batch cultures for more than 40 days. The novelty of this study is lactic acid production by repeated batch fermentation with immobilized L. casei using polyurethane foam (PUF) in an economical culture medium composed of whey and corn steep liquor supplemented by glucose.

Biocompatible materials, as efficient sorbent, are used for the removal of dyes and heavy metals ions from water and industrial wastewater. In this work, the optimal conditions for the maximum barium uptake in the formation process of Ba-alginate beads (Ba-ALG) were determined using the central composite design (CCD). The operational factors were evaluated for polymer/barium ratios of 1: 3, 1: 2, 1: 1, 2: 1, and 3: 1 and residence times of 20, 30, 75, 120, and 180 minutes. The optimal ratio of sodium alginate to barium concentration for cations uptake was obtained at 3: 1. Ba-ALG could not form a spherical and stable structure at higher polymer/cross-linker ratios. Validation tests illustrated the high accuracy of the selected model to determine the optimal experimental conditions in the barium uptake process. The maximum barium uptake is 88. 61%, which was achieved at XAB =1. 5 (optimal ratio of polymer to Ba+2) and Xt =1. 5 (180 min). The ability of Ba-ALG to adsorb dye was also evaluated. Kinetics, equilibrium, and thermodynamic studies for adsorption of malachite green (MG) by Ba-ALG were statistically described. The adsorption results match the pseudo-second-order kinetics, suggesting that there was MG dye uptake to the adsorbent in monolayers due to its chemical affinity. The thermodynamic parameters were also determined by the Gibbs free energy function, confirming that the adsorption process was spontaneous and accompanied by an endothermic reaction.

AbstractIntroduction: In this research, barium carbonate was synthesized via mechanochemical method from the mixture of barite concentrate-sodium carbonate. The producing of barium carbonate form barite concentrate and the evaluation of the phases/products were the goal of this research.Methods: After crushing the barite concentrate, the acid washing process was done with 1 N of HCl. The mixtures of barite concentrate-sodium carbonate with different molar ratios (BaSO4:Na2CO3=1:1, 1:2, 1:2.5) were prepared and milled in a planetary mill for different times (2 and 5 hours). The as-milled samples and the heated products were dissolved in distilled water and then the solid residues were dried in an oven. The isothermal heating of the samples was done into the alumina and zirconia crucibles. The unmilled mixture of barite concentrate-sodium carbonate was also prepared. The findings of this research were evaluated using XRF, XRD and STA methods and the microstructures of the samples were studied by SEM method.Findings: The2 and 5 h-milled mixtures showed the sign of chemical reaction between the starting materials (barite concentrate-sodium carbonate) at 720⁰C in STA results. This sign however was observed at 735 ͦC in the unmilled mixture. According to XRD patterns, the chemical reaction between barite concentrates and sodium carbonate was not completed in the milled mixtures. The signs of orthorhombic phase of barium carbonate were observed in the products after isothermal heating at700⁰C for 1 h. The results indicated that the isothermal heating of the milled mixture of barite concentrate-sodium carbonate with a molar ratio of 1:2.5 at 750⁰C for 2 h was the suitable conditions for synthesizing of barium carbonate. Additionally, the weak signs of an intermediate phase (Ca4Ba2Si6O18) were observed in the XRD patterns of the barite concentrate-sodium carbonate mixture. For comparison, the experiments were performed with pure barium sulfate sample (Barex). In the product of isothermal heating (750⁰C, 2 h) for the mixture of barium sulfate (Barex)-sodium carbonate (molar ratio :1:2.5), barium carbonate phase was produced and no trace of the intermediate phase was observed. The results of this research showed that it is possible to synthesis barium carbonate phase from the mixture of barite concentrate-sodium carbonate using ball milling process and isothermal heating.

In this research, the effects of two kinds of additives in Barium Titanate ceramics were studied, in order to related the microstructure to electrical properties of the system. In the first series, the effects of Cerium (as a dopant) and in the second series the effects of Cerium along with lead on the electrical properties (with emphasis on the PTCR behavior) were evaluated. The amount of Ce was changed from 0.1% to 0.5% mole and the amount of Pb was 30% which was considered to be substituted to Ba sites. The first series were sintered from 1100 °C to 1350 °C and the second ones from 1100 °C to 1300 °C. After polishing and coating, the electrical properties were measured and analyzed. The results showed that Ce doping lowers the resistance of the systems (in both cases, without and with Pb) up to 0.3% mole and increased after that. The addition of Pb had increased the Tc of the system. The optimal sintering temperatures were about 1350 °C and 1200 °C in the first and second series respectively. In the first series, the Tc was about 125 °C and in the second series 180-200 °C. X-ray diffractometry showed that in the first series, the dominant phase was pure Barium Titanate and in the second series Barium Lead Titanate.

Recently, there has been an increase in the ability to adjust the optical band gap and enhance the brightness of luminescence in nanophosphors that are used in light-emitting diodes and detectors. In this study, a flexible nanocomposite of erbium-doped barium tungstate (BaWO4:Er-1at.%) thin film was  synthesized via co-precipitation method, and the structural and luminescence properties were investigated. The effect of excitation wavelength ( ) was studied on the optical properties of the synthesized composite at room temperature. Doped nanocomposite  showed the best visible emission in the blue-green range at excitation wavelength =250) of a xenon lamp and a strong violet emission under 980 nm laser excitation. The XRD results verified the presence of BWO, in the chitosan composite structure. FESEM images showed that the prepared hybrid nanocomposite's surface was smooth, consistent, and compact; The Er:BWO particles exhibited a flower-like morphology. These findings demonstrate the potential for employing this nanocomposite in the fabrication of high-performance optoelectronic devices.

BACKGROUND AND OBJECTIVE: Hirschspnmg's disease (HD) is a congenital defect in pediatric patients, which is manifested by bowel obstruction in neonates or constipation in children. The gold standard of diagnosis is absence of ganglionic cells in myenteric neural plexus and submucosa of bowel. With regard to barium enema is a simple, less invasive and more available method than rectal biopsy, diagnostic evaluation of barium enema compared with rectal biopsy (as a diagnostic method) in HD is important.METHODS: In a cross-sectional study, 84 children with clinical manifestations of HD that referred to Boo-Ali Sina hospital of Sari, Iran were assessed from 2004 through 2007. Barium enema and rectal biopsy were carried out for all cases. Patients divided into three age groups as follows: under 1 month. 1- 12 months, more than 12 months Patient with previous history of anorectal surgery and negative pathology of HD excluded from the study. Sensitivity, specificity, positive predictive value and negative predictive value, of barium enema were calculated for identifying of the HD.FINDINGS: From 84 studied children, 28(33.3%) were girl. The mean age of the children was 26.1 months. The sensitivity, specificity, positive predictive value and negative predictive value of barium enema for diagnosis of the HD were 63.5%, 78.1%, 82.5%, and 56.8%, respectively. Diagnostic value of barium enema was calculated according to age groups mentioned above, that; there were significant differences among them (p<0.05).CONCLUSION: The results of the study showed that the validity of barium enema for identifying of the HD is completely age related. This validity in specificity and positive predictive value are more significant than in sensitivity and negative predictive value. Therefore, it is recommended considering all three aspects of clinical manifestations, barium enema and rectal biopsy in diagnosis of HD. of course, the diagnostic value is related to rectal biopsy.