Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Decomposition Kinetics of Titania Slag in Eutectic NaOH-NaNO3 System

The decomposition kinetics and mechanism of titania slag in eutectic NaOH-NaNO3 system were studied in the temperature range 623 K to 723 K (350 A degrees C to 450 A degrees C). Decomposed products were examined using X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. It has been identified that the main product is Na2TiO3 and the decomposition kinetics of titania slag followed a shrinking unreacted core model. It is proposed that the chemical reaction process was the rate determining step with apparent activation energy of 62.4 kJ/mol. NaNO3 was mainly acted as oxygen carrier and mass transport agent to lower the viscosity of the system. The purity of TiO2 obtained in the product was up to 99.3 pct. A flow diagram to produce TiO2 and to recycle the media was proposed

Treatment of tionite residue from titanium oxide industry for recovery of TiO2 and removal of silica

Solid waste tionite generated in the sulfate process for TiO2 production is a secondary titanium resource with high silicon content. To recover titanium and remove silicon from the tionite, a process involving hydrothermal conversion, water washing, and acid leaching was proposed. To avoid Na2O loss, the formation of Na2TiSiO5 by-product was prevented by adding CaO. XRD, ICP-OES and FT-IR were used to examine the transformation of the titanium and silicon. The optimum hydrothermal conditions are NaOH/tionite mass ratio of 4:1 and Ca/Si molar ratio of 1:1 in 45% NaOH solution at 240 degrees C for 1 h. Under these conditions, the titanium conversion was 97.3% with Na2TiO3 as the main titanium phase, while most silicon was converted to Ca(2)Sia(4), and katoite, and NaCaHSiO4, instead of Na2TiSiO5. About 97.5% of the Na2O was recovered after washing the hydrothermal products with water, and 93.1% of the silicon retained in the washed solution was removed by adding CaO. After leaching the washed products with 40% H2SO4 solution at 60 degrees C, about 97% of the titanium was easily recovered, forming the titanyl sulfate solution that was employed for TiO2 production. The Ca and Si components formed CaSO4 and silica gel, which were then separated from the acid leaching solution. (C) 2015 Elsevier B.V. All rights reserved

Ind. Eng. Chem. Res.

Rutile titanium dioxide (TiO(2)) white pigment has been prepared by doping and calcination of metatitanic acid (H(2)TiO(3)) obtained by the NaOH molten salt method. It was found that the properties of the rutile TiO(2) sample prepared were improved by adding K(2)O, P(2)O(5), Al(2)O(3), and rutile nuclei. The X-ray diffraction (XRD) results show the rutile content of the rutile TiO(2) sample prepared is 97%, and scanning electron microscopy (SEM) results show that the rutile TiO(2) particles prepared have well-shaped morphology and narrow particle size distribution. The purity and color performance of the rutile TiO(2) sample prepared approached the commercial TiO(2) pigment standards.Rutile titanium dioxide (TiO(2)) white pigment has been prepared by doping and calcination of metatitanic acid (H(2)TiO(3)) obtained by the NaOH molten salt method. It was found that the properties of the rutile TiO(2) sample prepared were improved by adding K(2)O, P(2)O(5), Al(2)O(3), and rutile nuclei. The X-ray diffraction (XRD) results show the rutile content of the rutile TiO(2) sample prepared is 97%, and scanning electron microscopy (SEM) results show that the rutile TiO(2) particles prepared have well-shaped morphology and narrow particle size distribution. The purity and color performance of the rutile TiO(2) sample prepared approached the commercial TiO(2) pigment standards

Recovery of titanium from undissolved residue (tionite) in titanium oxide industry via NaOH hydrothermal conversion and H_2SO_4 leaching

To recover titanium from tionite, a new process consisting of NaOH hydrothermal conversion, water washing, and H_2SO_4 leaching for TiO_2 preparation was developed. The experimental results show that under the optimum hydrothermal conversion conditions, i.e., 50% NaOH (mass fraction) solution, NaOH/tionite mass ratio of 4:1, reaction temperature of 240 °C, reaction time of 1 h and oxygen partial pressure of 0.25 MPa, the titanium was mainly converted into Na_2TiO_3, and the conversion was 97.2%. The unwanted product Na_2TiSiO_5 remained stable in water washing, and its formation was prevented by improving NaOH concentration. In water washing process, about 97.6% of Na~+ could be recycled by washing the hydrothermal product. The NaOH solutions could be reused after concentration. 96.7% of titanium in the washed product was easily leached in H_2SO_4 solution at low temperatures, forming titanyl sulfate solution to further prepare TiO_2

Sep. Purif. Technol.

Low-grade, highly reactive V-Ti concentrate was obtained from V-bearing titanomagnetite via selective reduction-magnetic separation. The main phases of the concentrate are anosovite and pyroxene. Two-stage acid leaching was employed to remove the impurities in the concentrate. The leaching behavior of impurities Ca/Mg/Al/Si under different acid leaching conditions in the first stage was investigated in detail. The optimal leaching conditions of the first-stage were as follows: 383 K leaching temperature, 1.40 mol/L HCl concentration, 1/10 solid-liquid mass ratio, and 120 min leaching time, under which the residue obtained contained 79.54% of TiO2 and 2.50% of V2O5. The result of molecular structure simulation indicate that the Ti-O and Mg-O bonds in the anosovite phase are broken under oxygen pressure conditions in the second stage by reacted with HCl solution. The content of TiO2 in the Ti-enriched slag prepared by two-stage acid leaching can reach 92.5% with further removal of residual carbon. (C) 2014 Elsevier B.V. All rights reserved.Low-grade, highly reactive V-Ti concentrate was obtained from V-bearing titanomagnetite via selective reduction-magnetic separation. The main phases of the concentrate are anosovite and pyroxene. Two-stage acid leaching was employed to remove the impurities in the concentrate. The leaching behavior of impurities Ca/Mg/Al/Si under different acid leaching conditions in the first stage was investigated in detail. The optimal leaching conditions of the first-stage were as follows: 383 K leaching temperature, 1.40 mol/L HCl concentration, 1/10 solid-liquid mass ratio, and 120 min leaching time, under which the residue obtained contained 79.54% of TiO2 and 2.50% of V2O5. The result of molecular structure simulation indicate that the Ti-O and Mg-O bonds in the anosovite phase are broken under oxygen pressure conditions in the second stage by reacted with HCl solution. The content of TiO2 in the Ti-enriched slag prepared by two-stage acid leaching can reach 92.5% with further removal of residual carbon. (C) 2014 Elsevier B.V. All rights reserved

Activation pretreatment of low-grade Ti-slag by alkali roasting: anticaking technique and kinetics of decomposition

The caking of roasting products is a serious problem in the activation pretreatment of low-grade Ti-slag by alkali roasting, which could lead to low heat transfer efficiency and low Ti conversion. In this study, an efficient anticaking technique was developed. This technique involved low-grade Ti-slag desilication and anticaking additive introduction. Optimum Ti conversion conditions in alkali roasting with KMnO4 as an anticaking additive were obtained through an orthogonal test. Approximately 99% of titanium in the low-grade Ti-slag could be decomposed at a loosening extent of roasting products of >90% in the presence of 4wt% KMnO4 as an anticaking additive. Kinetic study showed that an unreacted shrinking core model could be used to describe the decomposition of low-grade Ti-slag in alkali roasting with KMnO4 as an anticaking additive. Decomposition kinetics were characterized in two sequential stages: decomposition occurred relatively fast in the initial stage and became slower in the second stage. A mechanism of two-stage decomposition was proposed, i.e.,the reaction rate was controlled by a chemical reaction initially and then was controlled by inner/ash layer diffusion. Apparent activation energies were 53.6kJ/mol in the first stage and 65.9kJ/mol in the second stage, respectively. (c) 2015 Curtin University of Technology and John Wiley & Sons, Ltd

decompositionofaciddissolvedtitaniumslagfromaustraliabysodiumhydroxide

The kinetics of the decomposition of acid dissolved titanium slag with a sodium hydroxide system under atmospheric pressure was studied. The effect of reaction temperature, particle size and NaOH-to-slag mass ratio on titanium extraction was investigated. The results show that temperature and particle size have significant influence on titanium extraction. The experimental data of titanium extraction show that the shrinking core model with chemical reaction controlled process is most applicable for the decomposition of slag, with an apparent activation energy of 62.4 kJ.mol(-1). Approximately 85 wt.%-90 wt.% of the titanium can be extracted from the slag under the optimal conditions. In addition, the purity of titanium dioxide obtained in the product is up to 98.5 wt.%

Influence of magnesium and aluminum salts on hydrolysis of titanyl sulfate solution

The influence of magnesium and aluminum salts as impurities on the hydrolysis of titanyl sulfate was investigated. The degree of TiOSO_4 conversion to hydrated titanium dioxide (HTD) and the particle size of HTD were measured as functions of the concentrations of MgSO_4 and Al_2(SO_4)_3 in the TiOSO_4 solution. The Boltzmann growth model, which focuses on two main parameters, namely the concentrations of Mg~(2+) and Al~(3+) (ρ(Mg~(2+)) and ρ(Al~(3+)), respectively), fits the data from the hydrolysis process well with R2>0.988. The samples were characterized by ICP, SEM, XRD, and laser particle size analyzer. It is found that the addition of MgSO_4 simultaneously improves the hydrolysis ratio and the hydrolysis rate, especially when F (the mass ratio of H_2SO_4 to TiO_2) is high, hydrolysis ratio increases from 42.8% to 83.0%, whereas the addition of Al2(SO_4)_3 has negligible effect on the chemical kinetics of HTD precipitation during the hydrolysis process, hydrolysis ratio increases from 42.8% to 51.9%. An investigation on the particle size of HTD reveals that the addition of MgSO_4 and Al2(SO_4)_3 clearly increases the size of the crystallites and decreases the size of the aggregates