Georgia Kaolin Research Articles

Total stress model of clay considering small strain characteristics

Saturated soft clay has the characteristics of high compressibility, low strength, and high structural sensitivity. Its small strain characteristics have a significant impact on the deformation development and long-term bearing capacity of ocean engineering foundations. A total stress model for undrained cyclic loading of clay considering small strain characteristics was created based on the Overlay model. The proposed model was used to simulate the static or dynamic triaxial test results of over consolidated Chicago clay, remoulded normally consolidated Georgia kaolin, and normally consolidated clay Malaysia kaolin, respectively. The results verified that the model can simulate the static shear characteristics of clay. The model can also simulate the weakening of soil strength and strain accumulation under cyclic loading, and is suitable for analyzing the response of ocean engineering foundations under long-term cyclic loading.

Rare-Earth Minerals in Kaolin Ore, Mine Tailings, and Sands – Central Georgia, Upper Coastal Plain

AbstractThe total concentrations of rare-earth elements (REE) in the mined kaolin (0.02–0.06 wt.%), kaolin mine tailings (0.03–1.9 wt.%), and the kaolin-associated Marion Member sand lithology (0.03–4.6 wt.%) opened questions regarding the modes of occurrence of the REE and the role(s) of chemical weathering and secondary processes to explain the presence of REE in these materials. The REE were hosted primarily by phosphate minerals (monazite, xenotime) based on mineralogic analyses (scanning electron microscopy, X-ray diffraction). Enrichments in the light rare-earth elements (LREE: La–Gd) and the high correlation coefficient values were noted between P and the total REE concentrations (r2 = 0.99) for the sands and the mine tailings. Lower correlation coefficient values were noted between total REE concentrations and Zr (r2 = 0.31). The coarse fractions of the mined kaolins were enriched in the heavy rare-earth elements (HREE: Y, Tb–Lu) relative to the kaolin-associated sand lithologies. The REE inventory cannot be explained solely by mineral inheritance within the mined kaolins. Lower correlation coefficient values between P and total REE, positive Eu/Eu* anomalies, and the presence of xenotime overgrowths on zircon showed the importance of the role of chemical weathering of the detrital minerals during post-depositional processes (such as diagenesis) leading to redistributed and fractionated REE within the mined kaolin. The possibility of adsorption of the REE to kaolin mineral surfaces in the fine fraction of the mined kaolins remains open and permits further study to characterize fully the multi-modal fractionation of REE possible in the Georgia kaolin deposits.

BASF will sell Georgia kaolin business

BASF will sell its kaolin clay business in the state of Georgia to the minerals supplier KaMin. The business has 440 employees and annual sales of kaolin—used in ceramics and paper, and as a filler—of about $175 million. A BASF refinery catalyst business located with the kaolin operations is not part of the deal. Earlier in November, BASF agreed to sell an electronic chemical business to Entegris for $90 million. And BASF recently sold its water treatment joint venture, Solenis, to Platinum Equity for $5.25 billion.

BASF will sell its Georgia kaolin businesses

BASF will sell its Georgia kaolin businesses

Sorption and desorption of radiocesium by muscovite separated from the Georgia kaolin

Radiocesium (137Cs) sorption by moderately weathered, sand-sized muscovite, obtained as a byproduct of kaolin ore processing, was observed at various concentrations of added stable Cs (0–100 μmol/L) over a 130 d period. After 18 h of batch sorption with 1 mmol/L NaCl as background electrolyte, conditional 137Cs Kd values were near 2000 L/kg across the entire range of added stable Cs. Over four succeeding months, the Kd values increased by large factors for suspensions with little added Cs but increased only slightly for the suspensions with the most added Cs. The large grains of muscovite used in this study behaved distinctly differently than previously studied, much finer illite in that highly Cs-selective but low-abundance cation exchange sites appeared to be unavailable to the aqueous Cs during the first few days of the experiment. Diffusion pathways to highly Cs-selective sites were thought to be much longer in the muscovite than in frayed edges of illite, causing the highly Cs-selective sites to be isolated from the bulk solution. The longer diffusion pathways may be due to much greater stiffness of the material bounding interlayer wedges in the muscovite than in illite. This isolation from solution led to slow uptake at trace levels of Cs though the final Kd values (after 130 d) at those levels were comparable to those found for some illite. After 130 days, the original solutions were replaced by new electrolyte solutions containing no Cs, to observe 137Cs desorption over another 130 d period. There was no indication of desorption of 137Cs from the slowly accessible, highly Cs-selective sites apparently reached by most of the 137Cs during sorption at the low Cs levels. The byproduct mica from kaolin processing might serve effectively as a chemically stable sorbent to isolate accidently released radiocesium and to hold it until the 137Cs is virtually gone.

Effects of Physical Properties on Erosional and Yield Strengths of Fine-Grained Sediments

AbstractDue to interparticle forces between clay particles in fine-grained sediments, erodibility and transport mechanisms for fine sediments are different from those for coarse sediments, and the capability to predict the erosion resistance of fine sediments is still in question. In this study, sediment specimens with different kaolinite contents were prepared by mixing ground silica and Georgia kaolin with tap water. Geotechnical tests were carried out to obtain the sediment physical properties. The erosional and yield strengths of the specimens were determined through hydraulic flume experiments and rheometer tests, respectively. Relationships among the erosional and yield strengths and the sediment physical properties were developed. In dimensionless form, erosional and yield strengths of fine sediments are predicted by sediment properties including clay-size fraction and water content. In addition, a relationship is obtained to predict Shields’ parameter as a function of the corresponding dimensionle...

Evaluation of Laser-Induced Breakdown Spectroscopy (LIBS) for Measurement of Silica on Filter Samples of Coal Dust

Airborne silica dust (quartz) is common in coal mines and represents a respiratory hazard that can lead to silicosis, a potentially fatal lung disease. With an eye toward developing a portable monitoring device for rapid analysis of silica dust, laser-induced breakdown spectroscopy (LIBS) was used to quantify quartz in coal dust samples collected on filter media. Pure silica (Min-U-Sil™ 5), Georgia kaolin, and Pittsburgh-4 and Illinois-6 coal dusts were deposited separately and at multiple mass loadings onto 37-mm polyvinylchloride (PVC) filters. LIBS-generated silicon emission was monitored at 288.16 nm, and non-silica contributions to that signal from kaolinite were removed by simultaneously detecting aluminum. Measurements of the four samples were used to calculate limits of detection (LOD) for silicon and aluminum of approximately 0.08 μg/cm(2) and 0.05 μg/cm(2), respectively (corresponding to 0.16 μg/cm(2) and 0.20 μg/cm(2) for silica and kaolinite, respectively). Relative errors of prediction are around 10%. Results demonstrate that LIBS can dependably quantify silica on filter samples of coal dust and confirm that accurate quantification can be achieved for very lightly loaded samples, which supports the potential application of LIBS for rapid, in-field monitoring.

Organic Geochemical Composition of the Georgia Kaolins: Insights into Formation and Diagenetic Conditions

AbstractMost previous studies of the kaolin deposits in the southeastern United States have focused on their mineralogy and petrology to understand better the depositional and diagenetic environments of the kaolins. Many studies suggest, however, that much of the information held within the minerals was changed during extensive post-depositional groundwater and microbial alteration. Organic δ13C and biomarker analyses were used, therefore, to provide further information on the nature of the original sediments, the depositional environment(s), and the amount of diagenetic alteration that has occurred in Georgia kaolin deposits.Two different types of kaolin can be discerned, based on their total organic carbon contents: organic-lean kaolin and lignitic kaolin. The bulk organic δ13C in the Georgia kaolins ranges from ~−26 to −19% (VPDB, Vienna Pee Dee Belemnite standard), with a noticeable enrichment in 13C with decrease in organic carbon concentration. The lean kaolins are by far the more dominant types, with an organic-matter composition primarily of C16–C22n-alkanes, C16 and C18 fatty acids, and unresolved complex mixtures. Lignitic kaolin has a distinctly different organic matter (OM) composition. The lignitic material is primarily C15–C33n-alkanes with a greater abundance of C23–C31n-alkanes and lesser amounts of resinous and microbial constituents along with the oxidized forms of the saturated lipid fractions.Biomarker data suggest that the lignitic material is primarily terrestrially derived from conifers with minor input from microbial lipids. The OM in both types of kaolin shows strong signs of microbial decomposition that yield the organically lean kaolins. The oxidation of the detrital organic matter would subsequently yield organic acids that would have exerted significant influence on the mineralogy and metal mobility.

Influence of pigments and opacifiers on color stability of silicone maxillofacial elastomer

Objectives To determine the effects of opacifiers and silicone pigments on the color stability of silicone A-2000 maxillofacial prosthetic elastomers subjected to artificial aging. Methods Seventy-five groups ( n = 5) were made by various combinations (5%, 10%, and 15%) of four dry earth opacifiers (Georgia kaolin, Gk; calcined kaolin, Ck; Artskin white, Aw; titanium white dry pigment, Td); and 1 silicone pigment white (Sw) with one of 5 silicone pigments (no pigment (control), red (Pr), yellow (Py), burnt sienna (Po), and a mixture of Pr + Py + Po). A reflection spectrophotometer was used for color measurements. Color differences (Δ E*) between baseline and after an energy exposure of 450 kJ/m 2 in an artificial aging chamber were calculated. A Δ E* = 3.0 was used as 50:50% acceptability threshold in result interpretation, while Δ E* = 1.1 was used as 50:50% perceptibility threshold. Means were compared by Fisher's PLSD intervals at the 0.05 level of significance. Color differences after aging were subjected to three-way analysis of variance. Results Yellow ochre mixed with all opacifiers at all intervals had increased Δ E* values significantly from 0.7–2.1 up to 3.8–10.3. When mixed groups were considered, at 5%, Gk exhibited the smallest color changes, followed by Td < Aw = Sw < Ck, respectively. At 10%, Aw < Td < Gk < Sw = Ck. At 15%, Td < Aw < Gk = Sw < Ck (< indicates p < 0.0001 and = indicates p > 0.05). The smallest color differences, observed for opacifier groups, were recorded for Gk at 5%, and Td and Aw at 10% and 15%. Overall, 15% Td exhibited the smallest, whereas 5% Ck exhibited the most pronounced color change after artificial aging. All Δ E* values were below the 50:50% acceptability threshold, indicating acceptable color stability. Color differences for 10% and 15% of Aw and Td were below 50:50% perceptibility thresholds, indicating excellent color stability. Conclusion Silicone pigments mixed with 10% and 15% Artskin white and titanium white dry pigment opacifiers protected silicone A-2000 from color degradation over time. Yellow silicone pigment significantly affected color stability of all opacifiers especially silicone pigment white and calcined kaolin.

Simulating the stress–strain behavior of Georgia kaolin via recurrent neuronet approach

Many geotechnical engineering problems, such as slope stability analysis, require understanding of the constitutive behavior of clay under plane strain loading condition. Although studies on the mechanism of clay behavior had been carried out for many years, current theoretical accomplishments still cannot provide reliable simulations for clay under plane strain loading encountered in engineering practice. Traditional constitutive modeling, which involves building mathematical formulations with parameters determined from clay tests, seems to be an attractive approach. However, the complexity of the formulation, the large number of parameters involved, and the difficulty and time required to conduct clay tests make this approach impractical. As a result, there are no available reliable simulation models that can efficiently characterize the clay response under plane strain loading. Lack of appropriate simulation (constitutive) model for clay under plane strain loading greatly hinders the analysis, design, and construction with this material in engineering practice. Therefore, it is worthy to find another way to study the clay response under plane strain loading. In this paper, a recurrent neuronet-based model was developed in order to simulate clay behavior under plane strain loading conditions. This model was then used to investigate the effects of loading rate and stress history on clay response. The predicted responses showed that the developed neuronet-based model was successfully able to qualitatively assess the impact of strain rate and stress history on clay behavior. Accordingly, it is found that clay behavior is more sensitive to its consolidation stress history than to its strain loading rate.

Interactions of pigments and opacifiers on color stability of MDX4-4210/type A maxillofacial elastomers subjected to artificial aging

The color instability and degradation of maxillofacial elastomers limit the function and cosmetic quality of facial prostheses. The purpose of this study was to measure the interactions of oil pigments plus dry earth opacifiers at 5%, 10%, and 15% by volume in stabilizing the color of MDX4-4210/type A silicone elastomers before and after artificial aging. In the first part of the study, each of 5 opacifiers (Georgia kaolin powder neutral, kaolin powder calcined, Artskin white, dry pigment titanium (Ti) white, or Ti white artists' oil color) at 10% concentrations were combined with each of 5 oil pigment types (no pigment, cadmium-barium red deep, yellow ochre, burnt sienna, or a mixture of the 3 pigments), for a total of 25 experimental groups of elastomers. In the second part of the study, 50 experimental groups of elastomers were made by combining 1 of 5 opacifiers at 5% and 15% concentrations with 1 of 5 oil pigments as in Part 1. Five specimens of each elastomer were tested, for a total of 375 specimens. In each part of the study, all specimens were aged in an artificial aging chamber. CIE L*a*b* values were measured by a spectrophotometer. The color differences (DeltaE*) were subjected to repeated-measures analysis of variance. Mean values were compared by Tukey-Kramer intervals (alpha = .05). In Part 1, when the opacifiers were tested at 10% concentration, Ti white oil color had the most color change, and dry pigment Ti white had the least; all other opacifiers were not significantly different from each other. In Part 2, at 5%, Ti white oil color had the most color change; all other opacifiers were not significantly different from the others. At 15%, Ti white oil color again had the most color change, followed by Artskin white, kaolin powder calcined, and Georgia kaolin; Ti white dry earth pigment had the least color change. Overall, 5% Artskin white had less color change than the 15%, whereas 15% dry pigment Ti white had less color change than the 5% (P < .001). The 5% and 15% of other opacifiers were not significantly different. At all 3 concentrations, oil pigments mixed with opacifiers helped protect the MDX4-4210/type A silicone elastomer from color degradation over time. Dry pigment Ti white remained the most color stable over time, followed by the pigments mixed with kaolin powder calcined, Georgia kaolin, Artskin white, and Ti white artists' oil color.

FIRST RECORD OF A CHIMAEROID FISH FROM THE EOCENE OF THE SOUTHEASTERN UNITED STATES

Although fossilized teeth of sharks and rays are common elements in Eocene nearshore marine sediments of the southeastern United States (Parmley and Cicimurri, 2003 and references within), fossil remains of chimaeroid fishes are unknown from this region. Here we provide the first report of an Eocene chimaeroid fish from the southeastern United States, consisting of a partial, well-preserved left mandibular tooth plate recovered from central Georgia. The specimen was collected from late Eocene (ca. 36.0–34.2 Ma; Parmley and Holman, 2003) Clinchfield Formation sediments exposed in an abandoned central Georgia kaolin mine formally known as the Hardie Mine (Westgate, 2001). The Hardie Mine is located approximately 3.9 km north-northeast of Gordon, Wilkinson County, Georgia. This site has yielded a relatively well-preserved and diverse nearshore marine vertebrate fauna consisting of sharks, rays, bony fishes, reptiles, and whales (Westgate, 2001; Parmley and Cicimurri, 2003; Parmley and Holman, 2003). Additionally, the vertebra of a colubrid snake (Parmley and Holman, 2003) and partial teeth of at least two species of land mammals (unstudied fossils in the paleontological collections of Georgia College and State University–GCVP) are known from the Hardie Mine site. The vast majority of fossils collected from the Hardie Mine were recovered from a series of spoil pile sediments. It has been shown, however, that these sediments were derived locally from nearby in situ fossiliferous Clinchfield Formation sediments exposed in the north wall of the mine (see Westgate, 2001; Parmley and Cicimurri, 2003; Parmley and Holman, 2003). For the purposes of this report we follow the descriptive terminology utilized by Stahl (1999), and a comprehensive classification scheme can be found in Stahl and Parris (2004). We utilized the histological terminology of Stahl (1999), but we did not perform any direct microscopic analyses of tissues. The specimen …

Quantitative analysis of anatase in Georgia kaolins using Raman spectroscopy

Raman spectroscopy of Georgia kaolins ubiquitously show a strong E g frequency near 144 cm −1. Analysis of the band intensity shows that under specific source, sample, and optical conditions, peak area measurements are predictable and reproducible. Using standard additions, successful quantitative techniques have been developed that allow analysis of 25% solids water slurries, which achieve anatase detection limits down to 0.3% with a standard error of ±0.1%. Anatase was also studied with X-ray powder diffraction to examine the extent of crystal chemical variation. The a lattice dimensions of anatase from Georgia kaolins range from 0.3786 to 0.3796 nm. The mean coherent scattering length in the [100] direction range from 80 to 160 nm. Given the range of anatase particle sizes previously observed in Georgia kaolins (8000–150,000 nm), these parameters indicate an average defect density of 100 domains per crystal and structural formulae that range from Fe 0.03Ti 0.97O 1.97(OH) 0.03 to Fe 0.06Ti 0.93O 1.93(OH) 0.06. Quantitative estimates of anatase abundance using Raman require careful attention to background fluorescence effects due to the presence of hematite, goethite, and organic matter. Background fluorescence intensity in the regions of 400 and 600 cm −1 correlate with known additions of hematite and goethite, respectively. The removal of organic matter from gray clays by H 2O 2 treatment significantly reduced background fluorescence. The small variations in anatase crystal chemistry do not appear to have any first-order effects on Raman intensity of the 144 cm −1 band. The comparison of total TiO 2 using X-ray fluorescence techniques with anatase content reveals that, in many instances, there is a significant non-anatase TiO 2 component present in Georgia kaolins. The discrimination of Ti-phases has the potential to provide new insights into strategies for mineral separation techniques, kaolin reserve estimates, and understanding of the geologic history of the Georgia kaolin deposits.

Effect of opacifiers on color stability of pigmented maxillofacial silicone A‐2186 subjected to artificial aging

This study was designed to determine the effect of opacifiers used at different ratios on the color stability of pigmented A-2186 silicone maxillofacial elastomers and to evaluate the color spectrophotometrically before and after artificial aging. Sixty experimental groups of elastomers were made using various concentrations (5%, 10%, and 15%) of 4 opacifiers (Georgia kaolin powder neutral, kaolin powder calcined, Artskin white, and dry pigment titanium white) with 1 of 5 dry earth cosmetic pigment groups (no pigment [control], red, yellow ochre, burnt sienna, and a mixture of all pigments). Five specimens of each elastomer were tested, for a total of 300 specimens. All specimens were placed in an aging chamber and artificially aged by exposure to light, water spray, fluctuating temperatures, and humidity. CIE L*a*b* values were measured by spectrophotometer. The color differences (Delta E*) at various exposure energies (150, 300, and 450 kJ/m(2)) were subjected to 4-way analysis of variance with repeated measures (super ANOVA). Mean values were compared with Tukey-Kramer intervals calculated at the 0.05 significance level. The trained human eye can detect color changes (Delta E*) greater than 1.0. Adding all pigments to any of the kaolin groups did not protect silicone A-2186 from color degradation over time. Mixing red pigment in all groups at all times drastically increased DeltaE* values ranging from 0.1 to 1.3 up to 16.6 to 49.6. Yellow ochre had an effect only with 10% and 15% concentrations of kaolin powder calcined, increasing the value of Delta E* to greater than 1.0. Burnt sienna had an effect only with a 15% concentration of kaolin powder calcined, increasing the value of Delta E* at 300 and 450 kJ/m(2) to greater than 11.0. At the 5% concentration, kaolin powder calcined had the smallest color changes, followed by, in order, dry pigment titanium white, Artskin white, and Georgia kaolin. At the 10% concentration, Artskin white had the smallest color changes, followed by, in order, dry pigment titanium white, kaolin powder calcined, and Georgia kaolin. At the 15% concentration, Artskin white again had the smallest color changes, followed by, in order, dry pigment titanium white, Georgia kaolin, and the kaolin powder calcined. The smallest color changes in each kaolin group were at the 10% concentration for Artskin white, dry pigment titanium white, and kaolin powder calcined and at the 5% concentration for Georgia kaolin. Mixing dry earth cosmetic pigments with opacifiers did not protect silicone A-2186 from color degradation over time, especially in the case of red pigment. The group in which pigments were mixed with 10% Artskin white had the smallest color changes over time, followed by, in order, the groups in which pigments were mixed with 10% dry pigment titanium white, 10% kaolin powder calcined, and 5% Georgia kaolin. Red pigment had a significant effect on all opacifiers, especially Georgia kaolin and kaolin powder calcined. Yellow ochre and burnt sienna had an effect only on 15% kaolin powder calcined. Among all the pigment groups tested, yellow ochre remained the most color stable over time.

Ti-Bearing Phases in the Huber Formation, an East Georgia Kaolin Deposit

AbstractSix kaolin samples from the Lower Tertiary Huber Formation near Wrens, Georgia were analyzed using transmission electron microscopy (TEM), electron diffraction (ED), powder X-ray diffraction (XRD), chemical analysis, and magnetic susceptibility to characterize the Ti-bearing phases. Selected samples were treated with 5 M NaOH to remove kaolinite and concentrate the Ti-bearing phases for additional analysis. TiO2 content in the bulk fraction ranges from 1.2 to 5.4 wt. %. There are at least three Ti-bearing phases, including anatase, rutile, and a poorly defined nanocrystalline form. Anatase is most abundant and is commonly found with {010} faces in association with kaolinite edge and basal faces. The nanocrystalline form occurs at 0–1 wt. %, and rutile occurs in trace amounts. Bulk XRD analysis correlates well with the bulk TiO2 chemical measurements. Average anatase unit-cell parameters are a = 0.37908 ± 0.0002 nm and c = 0.951 ± 0.001 nm. These parameters indicate an approximate chemical formula of Fe3+0.05Ti4+0.95O1.95(OH)0.05.The distribution of TiO2 content as a function of depth may be useful to obtain original grain-size variations associated with relative sea-level changes responsible for the deposition of the Huber Formation. Evidence for original depositional sediment properties can be seen in the occurrence of pseudomorphic replacement of micas and fecal pellets by kaolinite. Additional evidence for post-depositional changes includes the sub-micrometer euhedral character and low Fe content of the anatase (relative to soil-derived anatase). These observations for the Huber Formation are consistent with a previously published theory for kaolin genesis that includes biomineralization of originally coarser-grained aluminosilicates into a kaolinite-rich ore body.

Effects of Addition of Montmorillonite on the Plasticity of Georgia Kaolin.

Effects of addition of montmollironite on the plasticity of kaolinitic clay, Georgia kaolin, was studied by a uniaxial compression test. It was found that the plasticity of Georgia kaolin was affected by the addition of montmorillonite. From the relation of stress-aspect ratio curve appeared by a uniaxial compression test, the relationship between yield point, which represented a fluidity of the plasticity, and water content was studied. It was suggested that the fluidity was improved when montmorillonite was added in Georgia kaolin. When the forming retention of Georgia kaolin added with montmorillonite was compared with that of Georgia kaolin, the forming retention of Georgia kaolin added with montmorillonite was smaller than that of Georgia kaolin. The relationship between the forming retention and the fluidity of Georgia kaolin added with montmorillonite and Georgia kaolin was investigated. The forming retention of paste added montmorillonite in Georgia kaolin was increased when the fluidity value was same. The plasticity of a Georgia kaolin green body added with montmorillonite improved on that of Georgia kaolin green body.

Factors Affecting the Plasticity of Georgia Kaolin Green Body.

The plasticity of Georgia kaolin was studied to clarify the factors affecting the uniaxial compression behavior before and after ion-exchange in 1N CH3COONH4 solution. Georgia kaolin, a kaolinitic clay, showed a very small amount of dissolution of divalent cations and a similar zeta-potential change before and after the ion-exchange. According to an analysis of the uniaxial compression test, the plasticity degraded at pH 7, however, improved at pH 4.9. It was found that the plasticity was more affected by the pH and zeta-potential value than by the adsorbed ions.

Influence of Heat Treatment on the Plasticity of Georgia Kaolin.

Plasticity of clay dough is strongly influenced by the formation of buffer domain consisted of clay aggregates. Change in plasticity of Georgia kaolin along with heat treatment was analyzed by examining the variation of the particle packing structure of the dough. The plastic behavior did not change by the heat treatment up to 350°C. However, above 350°C, plasticity was reduced together with micron sized pores existing among aggregates. The lower plasticity arose from destruction of buffer domains, caused by the increase of particle size upon sintering.

Low-cost experimental unit and growth medium for testing soil effects on shrimp culture

PVC pipes, 10 cm in diameter and 46 cm long, sealed at one end and filled with 18 ppt of artificial seawater and a 6-cm layer of substrate, were tested as experimental units for the culturing of penaeid shrimp. The growth substrate was prepared by mixing 70% quartz sand, 24% Georgia kaolin, 5% Gonzales bentonite and 1% Bermuda grass hay. One juvenile Penaeus vannamei was placed in each container and shrimp weight gain was monitored. In the first study (four replicates), shrimp grew to 8.15 g within 8 weeks at a rate of ≈1 g week −1 with no mortality; thereafter, growth decreased and 25% mortality was observed. In the second study (seven replicates), the average weight of shrimp was 8.66 g in 10 weeks, with 29% mortality occurring between the seventh and eighth week. Experimental unit cost was $3.30.

X-ray Absorption Fine-Structure Spectroscopy Study of Photocatalyzed, Heterogeneous As(III) Oxidation on Kaolin and Anatase

We have used X-ray absorption fine-structure spectroscopy (XAFS) to investigate As(III) adsorption on bulk Georgia kaolin (KGa-1b), Wyoming smectite (SWy-2), anatase (TiO2), gibbsite [Al(OH)3], and amorphous silica (am-SiO2) with the goal of identifying the oxidants responsible for As(III) oxidation in KGa-1b. After 30 h of reaction, ≥30% of the added As(III) was oxidized to As(V) in KGa-1b and anatase experiments, whereas only ≈10% of the added As(III) was oxidized in experiments using bulk SWy-2 and gibbsite. As(III) oxidation was negligible in experiments using am-SiO2. The proportion of As(III) oxidized by KGa-1b increased with increasing equilibration time, decreased significantly with increasing pH (up to pH 8), and decreased slightly with increasing ionic strength. Although Mn has been proposed as the potential oxidant of As(III) in KGa-1b, it can account for only ≈2% of the As(V) produced under the conditions of our experiments because of its low concentration in this material (3 ppm). Proof that ...