Well-rounded grains are normally used as filtration media, because the spherical shape seems to be most suitable to get rapid
and efficient removal operations. In this sense, the direct use of natural clays as filtration media is problematic, due to
the plate-type shape of the particles. In this work, rounded grains of two natural clays processed by spray-drying are tested
as filtration media. The settling regime of the grains in a filtration column was determined and the chromium removal from
water was also tested. Sieved fractions now used (355–1680 μm) show settling behavior according to the transition regime.
Preliminary results of chromium removal by the selected 355–420 μm sieved fraction bed show interesting capabilities for the
Cr3+ species, while chromate (VI) retention is extremely low.
Received: 12 January 1998 Accepted: 2 April 1998 相似文献
One of the industrially important qualities of yeast is their ability to provide the cell-cell and cell-support interactions. This feature of yeast is responsible for technologically significant phenomena such as flocculation (brewing) and yeast biofilm formation (immobilization to supports), whereas these phenomena are time, environment, and strain dependent. Therefore, the goal of this work was to verify the possibility to predict and subsequently select yeast strains capable to colonize solid supports by using physicochemical adhesion models. Three different industrial yeast strains (Saccharomyces cerevisiae) were tested for their adhesion onto spent grain particles in the continuous gas-lift reactor. The cell adhesion energies were calculated, based on physicochemical characteristics of surfaces involved, according to three adhesion models (DLVO theory, thermodynamic approach, and extended DLVO theory). The role of physicochemical surface properties in the cell-cell and cell-support interactions was evaluated by comparing the computed predictions with experimental results. The best agreement between forecast and observation of the yeast adhesion to spent grains was achieved with the extended DLVO (XDLVO) theory, the most complex adhesion model applied in this study. Despite its relative comprehensiveness, the XDLVO theory does not take into account specific biochemical interactions. Consequently, additional understanding of the yeast adhesion mechanism was obtained by means of quantifying the expression of selected FLO genes. The presented approach provides tools to select the appropriately adhesive yeast strains and match them with solid supports of convenient surface properties in order to design immobilized biocatalysts exploitable in biotechnological processes. 相似文献
AgSt/AgC1 composite gains were prepared by adding chloride ions to a mixed solvent in which silver stearate (AgSt) grains were dispersed under the condition of controlled pH value and characterized by SEM, XRD, UV and DSC. The results showed that AgSt/AgC1 composite grains were composed of plateqike AgSt grains with small face-centered cubic AgC1 particles formed on the surface of AgSt. UV spectra displayed a red shift of absorption for AgSt/AgC1 relative to pure AgSt or AgC1. DSC showed a new thermal phase transition of AgSt/AgC1 grains. 相似文献
The dry-grind corn process is one of two technologies used to convert corn into ethanol. In his process, all kernel components
are processed through several sequential steps, including fermentation. Only one coproduct (distillers’ dried grains with
solubles [DDGS]) is available for marketing. DDGS provide income to offset costs of processing; issues that affect marketing
have implications in the economic viability of dry-grind plants. Two issues relate to elements in DDGS: high concentrations
and excessive variation. Data on element concentrations in dry-grind processing streams could be helpful in addressing these
concerns. The objective of this study was to determine element concentrations in primary process streams from dry-grind plants.
Samples of corn, ground corn, beer, wet grains, syrup, and DDGS were obtained from nine dry-grind plants, and element concentrations
were determinined. The concentrations of most elements in corn were not different among processing plants and were similar
to published data. However, for the processing streams, there were differences in several element concentrations among processing
plants. The concentrations of most elements in beer were about three times those of corn, due to the disappearance of starch
during fermentation. Syrup had the highest element concentrations. Variations in element contents of DDGS and parent streams
were due to processing conditions and not corn. Appropriate processing of thin stillage (the parent stream of syrup) could
reduce the element content of DDGS. 相似文献
Ethanol fermentations were conducted using both whole corn, and corn with 100% of the germ, and a portion (∼74%) of the fiber
removed. Ethanol production increased 11% in the germ and fiber-removed corn vs the whole corn. The protein content of distiller's
dried grains and solubles increased from 30 to 36%, and phosphate levels were 60% lower in corn with germ and fiber removed
vs whole corn. Removal of germ and fiber prior to fermentation allows higher starch loading and results in increased ethanol
production. The integration of germ and fiber removal in the dry-grind ethanol industry could increase capacity and add valuable
coproducts, resulting in increased productivity and profits. 相似文献
The results of the Marjalahti pallasite fission-track age determination are presented. Thorough examination of fossil tracks in the phosphate (whitlockite) crystals coupled with U-content determination in whitlockites can make it possible to estimate the contributions of all possible track sources to the total track density and to calculate a model fission-track age.
It is found that whitlockite crystals of the Marjalahti pallasite contain fossil tracks due to galactic cosmic rays (VH, VVH nuclei); fission of U and Th induced by cosmic rays; spontaneous fission of 238U; and spontaneous fission of extinct, short-lived 244Pu present in significant quantities in the early solar system.
A great track density attributed to the extinct 244Pu testifies to the high fission-track age. The model fission-track ages of (4.31±0.02)×109 yr for the Marjalahti pallasite are calculated. Petrographic studies allow us to interpret the fission-track age as the time of the last shock/thermal event in the cosmic history of the pallasite. 相似文献
We present the Raman spectra of nano-SnO_{2} grains with sizes from 4nm to 80nm excited by 532nm and 1.06μm lines. The enhanced Raman scattering of the nanograins is observed for both exciting lines when the grain size is less than 8nm. The less the grain size is, the more intensely the Raman scattering is enhanced. According to our results, the enhancements of the Raman intensity are a few tenfolds and different for different exciting lines when the grain size is 4nm. It can be attributed to enhanced Raman scattering by electron-hole pair excitations in the nanograins that originate from sub-microscopic (10nm) size and other defect- and surface-related features. A critical size that divides respective predominance of bulk properties and the defect-, surface-, and size-related features can be determined to be about 8nm. 相似文献
A multi-phase field model is established to simulate the growth competition and evolution behavior between seaweed and columnar dendrites during directional solidification.According to the effects of surface tension and interfacial energy,we quantitatively analyze the influences of factors such as inclination angles,pulling velocity,and anisotropic strength on twin growth.The results demonstrate that the pulling velocity and anisotropic strength have an important influence on the morphology and evolution of the seaweed and dendritic growth.The low pulling velocity and anisotropic strength are both key parameters for maintaining the stable morphology of seaweed during competitive growth in a bicrystal,showing that the lateral branching behavior is the root of the dendrites that can ultimately dominate the growth.And it is clarified that the lateral branching behavior and lateral blocking are the root causes of the final dominant growth of dendrites.With the increase of anisotropy strength,the seaweed is eliminated fastest in case 1,the seaweed is transformed into degenerate dendritic morphology,and eliminates the seaweed by promoting the generation and lateral growth of the lateral branches of the dendrites.The increase of pulling velocity is to increase the undercooling of favorable oriented grain and accelerate the growth rate of dendrites,thus producing more new primary dendrites for lateral expansion and accelerating the elimination rate of unfavorable oriented grain. 相似文献