Feed Broth Research Articles

Speciation and Ammonia-Induced Precipitation of Neptunium and Uranium Ions.

The pH evolution and corresponding changes in the UV-Vis-NIR absorption spectra of oxygenated neptunium (NpO2+ and NpO22+) and uranyl ions (UO22+) in nitric acid are investigated during titration with an aqueous NH3 solution. The speciation and precipitation regimes between acidic (pH 1.5) and alkaline (pH 10) conditions at room temperature are discussed to assess the suitability of Np(V) or Np(VI) in sol-gel conversion processes for fuel target fabrication. Under the applied experimental conditions, Np(V) hydrolyzes and precipitates into the insoluble hydroxide NpO2OH only above pH values 7.5 and an increase up to pH 10.0 is required to precipitate quantitatively. Np(VI) displays changes in the coordination environment of NpO22+ ions in the pH interval 1.6-4.0, similar to what is observed for U(VI). Precipitation into NpO3·H2O or other hydroxide compounds takes place between pH 4.0 and 5.9, which overlaps largely with precipitation of ammonium diuranate species from the U(VI) solution. The use of concentrated NH3 aqueous solution, as commonly used in the external gelation process, will allow to quantitatively precipitate both Np(V) and Np(VI) species. Internal gelation process conditions, on the other hand, seem incompatible with the high pH required to precipitate Np(V) completely. For fabricating mixed-oxide (U,Np) targets using sol-gel conversion, a feed broth containing Np(VI) and U(VI) will be required to achieve homogeneous gelation.

Use of boiled hexamethylenetetramine and urea to increase the porosity of cerium dioxide microspheres formed in the internal gelation process

Cerium dioxide (CeO2) is a commonly used simulant for plutonium dioxide and for plutonium (Pu) in uranium (U) and Pu oxide [(U, Pu)O2] mixtures used in nuclear fuel development. This effort developed CeO2 microspheres with a various porosities and diameters. The internal gelation technique has only been used to produce CeO2 microspheres with limited initial porosity. Previous studies have shown that the crystallite size and porosity of mixed U and thorium oxide microspheres and the (U, Pu)O2 microspheres from the internal gelation process increased when an equal molar solution of hexamethylenetetramine (HMTA) and urea is gently boiled for 1 h prior to its use in the gelation process. In this study with cerium, the combination of ammonium cerium nitrate and 1-h boiled HMTA-urea failed to produce a stable feed broth. However, when the 1-h heated HMTA-urea was combined with unheated HMTA-urea in 1–3 vol ratio or the boiling time of the HMTA-urea was reduced to 15–20 min, a stable solution of HMTA, urea, and Ce was formed at 273 K. This new Ce solution produced very porous CeO2 microspheres, which are suitable simulants for uranium microspheres.

CO2 Life-Cycle Assessment of the Production of Algae-Based Liquid Fuel Compared to Crude Oil to Diesel

Life-cycle assessment for carbon dioxide emission was performed for an open pond microalgae based process to grow, harvest, extract, and produce a paraffinic hydrotreated algae oil (HTAO). The process was assumed to also produce a co-product of animal feed. A base case was defined using generally accepted parameter values for present technology and does not represent an optimized design. This base case process was compared to the CO2 equivalent emissions from conventional crude oil refining through the middle distillate (MD) of the atmospheric column of a refinery. Both MD and HTAO products were viewed as equivalent being diesel or nearly diesel. CO2 emissions from the HTAO process were strongly dominated by drying of lipid extracted biomass for animal feed containing 85% moisture and the CO2 emissions in producing purified CO2 for algal growth. Ammonia as a nutrient was also a major CO2 contributor followed by energy required for pond flow. In aggregate, utilities (heat and electric) were a greater contributor than the combination of raw materials and nutrients. A sensitivity analysis showed that the most impactful operating parameters on CO2 emission from the base case HTAO process are, in order of importance, (a) moisture content of the lipid extracted biomass feeding the animal feed dryer, (b) oil content of algae, (c) algae doubling time, (d) feed broth algae concentration, (e) pond depth, and (f) retention time in the pond. On the basis of “well-(or pond)-to-wheel” (WTW), it was found that the base case algal route to HTAO of this work did not reduce CO2 emission compared to production of conventional diesel, being worse than MD. However, if moisture content in the wet cake going to the animal feed dryer was reduced from 85% to 75% moisture and if a 10% improvement in operating parameters over the base case was made, the HTAO process was estimated to have WTW CO2 emissions which are ∼34% lower than MD. Since the base case is not optimized with respect to process integration and energy economization, still further improvement in the HTAO process is possible.

Modelling and numerical simulation of liquid–solid circulating fluidized bed system for protein purification

A novel liquid–solid circulating fluidized bed (LSCFB) was modelled for protein recovery from the feed broth. A typical LSCFB system consists of downer and riser, integrating two different operations simultaneously. A general purpose, extensible, and dynamic model was written based on the tanks-in-series framework. The model allowed adjusting the degree of backmixing in each phase for both columns. The model was validated with previously published data on extraction of bovine serum albumin (BSA) as model protein. Detailed dynamic analysis was performed on the protein recovery operation. The interaction between the riser and downer were captured. Parametric studies on protein recovery in LSCFB system were carried out using the validated model to better understand the system behaviour. Simulation results have shown that both production rate and overall recovery increased with solids circulation rate, superficial liquid velocity in the downer and riser, and feed solution concentration. The model was flexible and could use various forms of ion exchange kinetics and could simulate different hydrodynamic behaviours. It was useful to gain insight into protein recovery processes. The general nature of the model made it useful to study other protein recovery operations for plant and animal proteins. It could also be useful for further multi-objective optimization studies to optimize the LSCFB system.

Effect of surfactants on the morphology of titania microspheres prepared by internal gelation process

Internal gelation process was employed for preparation of 0.3–1 mm sized microspheres of titania for their application in ion exchange columns. The conventional internal gelation process was modified by adding surfactant and oil emulsion in the feed broth, which introduced large pores in the structure of the material. The effects of concentration of hydrochloric acid, titanium, surfactant and hexamethylenetetramine to titanium ratio in the feed broth and temperature of calcination on the surface characteristics of the final product were studied. The conditions of preparation were optimized to obtain physically stable porous microspheres suitable for various applications. The resultant material was characterized by pore size distribution, pore volume, thermogravimetry, X-ray diffraction and SEM analyses. Ion exchange behaviour of the material was then studied by pH titration.

Preparation of porous titania–silica microspheres for treatment of radioactive waste

Titania–silica microspheres have been prepared by sol–gel process. Internal gelation route, which use hexamethylenetetramine as the source of ammonia was used for the preparation spherical gel particles. A cationic surfactant, cetrimide was added in the feed broth for introducing meso-porosity in the gel network. Further paraffin oil emulsion was incorporated in the feed broth before gelation for the formation of larger pores in the gel network. The spherical gel particles thus obtained were washed and heat treated under controlled conditions to remove the entrapped surfactant, paraffin oil and other organic compounds resulting in highly porous intact titania–silica microspheres. The material was characterized by surface area, porosity and by SEM photomicrographs. The ion exchange property of this material was studied using the sorption of plutonium on this material from carbonate medium by distribution coefficient studies and ion exchange column loading and elution experiments.

Recovery of plutonium from aqueous waste solutions using porous zirconia spherical particles

Porous zirconia spherical particles have been prepared by internal gelation process. During preparation of these spherical particles, a cationic surfactant, cetrimide was added in the feed broth to increase the surface area and porosity of the particles. The sorption behavior of plutonium was investigated on this material from different complexing aqueous media from the recovery point of view. Distribution ratio studies have been carried out to investigate the effect of varying concentrations of oxalic acid, phosphoric acid, sulphuric acid, nitric acid, sodium carbonate and sodium bicarbonate to optimize the conditions of sorption of plutonium on this ion exchange material.

Preparation of porous zirconia microspheres by internal gelation method

A modified internal gelation process for the preparation of porous zirconia microspheres has been developed. The conventional method has been modified by adding a surfactant in the feed broth. The effects of variation of surfactant concentration, washing techniques and temperature of calcination on the pore volume and the surface area of the microspheres have been studied. The conditions were optimized to obtain porous stable microspheres suitable for various applications. The microspheres were characterized by surface area analysis, pore volume analysis, thermogravimetric analysis and X-ray diffraction. The ion exchange behavior was studied using pH titration.

Removal of plutonium from carbonate medium using titania microspheres prepared by sol-gel route

Spherical beads of titania were prepared by a sol-gel route. During the preparation a cationic surfactant was added in the feed broth to modify the surface characteristics of the microspheres. The absorption behavior of Pu(IV) from carbonate medium on these microspheres was studied by batch experiments. Loading and elution behavior of Pu(IV) on a bed of titania microspheres was studied and the practical capacity was determined.

Protein loading, elution, and resolution behavior in a novel device that integrates ultrafiltration and chromatographic separation.

Hollow fiber membranes and chromatographic resin beads are commonly employed in a variety of bioseparation processes. A new class of integrated separation devices is being studied in which the shell side of a hollow fiber device is filled with adsorbents/chromatographic resin beads. Such devices and the corresponding separation methods integrate feed broth clarification by the microfiltration/ultrafiltration membrane with bioproduct purification by the shell-side resin beads either as an adsorbent or as beads in elution chromatography. A mathematical model has been developed for the prediction of the chromatographic behavior of such an integrated device. Simulations have been done to study the effects of axial dispersion, feed flow rate, water permeation rate, fiber packing density, and void fraction. Numerical solutions were obtained by solving the governing equations. This model can reasonably describe the concentration profiles as well as the breakthrough and elution behaviors in the integrated device.

Fabrication of UO 2 pellets by gel pelletization technique without addition of carbon as pore former

High density UO 2 pellets for pressurised heavy water reactor fuel were fabricated by a gel pelletization technique from soft UO 2 microspheres prepared by an internal gelation process. Chemical and heat treatment parameters were determined for obtaining soft UO 2 microspheres with optimum properties required for making defect-free, high density, UO 2 pellets. Investigations reveal that a high uranium concentration in the feed broth during the preparation of UO 3 gel particles, conversion to UO 2 via U 3O 8, and optimized calcination and reduction temperatures, result in UO 2 microspheres suitable for obtaining good quality green compacts. Green pellets were densified by low temperature sintering in a C0 2 atmosphere at 1200°C to obtain high density UO 2+ x pellets and reduced at 800°C to UO 2.00 in Ar + 8%H 2 Resulting pellets were free from open porosity and black berry structure.

Inhibition of the Growth of Salmonella typhimurium and Escherichia coli O157:H7 on Chicken Feed Media by Bacteria Isolated from the Intestinal Microflora of Chickens

Two lactic acid-producing bacteria, one volatile fatty acid-producing bacterium, and one starch-hydrolyzing bacterium were isolated from the cecal contents of adult chickens. The ability of these bacteria to produce lactic and volatile fatty acids in 5% chicken feed broth media and to inhibit the growth of Salmonella typhimurium and Escherichia coli 0157:H7 on a 5% chicken feed agar media was determined. Inhibition of the growth of the enteropathogens was due to bacteriostatic or bactericidal substances that the cecal isolates produced in the media. Depending on which isolates were used, the inhibitory substances were either high concentrations of lactic acid that created an inhibitory pH in the media or inhibitory concentrations of acetic and propionic acids that the isolates produced in the media.

Nutritional control of nikkomycin and juglomycin production by Streptomyces tendae in continuous culture.

Continuous cultures with Streptomyces tendae revealed some interesting facts. In a continuous culture running for more than 2500 h the production of either nikkomycines or juglomycins could be selected by varying the feed composition. Decreasing the phosphate supply in the feed broth from the initial concentration of 2.5 mM to 1.0 mM enhanced the productivity of nikkomycins and decreased the productivity of juglomycins. When switching back to the initial conditions of the experiment after 2000 h nearly the same production behaviour as at the beginning of the fermentation could be observed. This indicated a stable behaviour of the population with regard to nikkomycin productivity. The long continuous fermentation showed the ability of S. tendae Tü 901/8c to produce nikkomycin at a high level for at least 1500 h. In a second continuous culture it was shown that the productivity of the nikkomycins and juglomycins decreased and increased, respectively, with increasing dilution rate. Comparing batch cultures with continuous fermentations, higher juglomycin productivity was found in the latter. These facts indicate that the strain responds to complex interacting physiological controls, by producing either nikkomycins or juglomycins in a higher amount.