scholarly journals Modification of pillared layered clays for scavenging radiostrontium from acidic aqueous environments

2020 ◽  
Vol 9 ◽  
pp. 331
Author(s):  
C. A. Papachristodoulou ◽  
P. A. Assimakopoulos ◽  
N.-H. Gangas ◽  
D. T. Karamanis
Keyword(s):  
Exchange Effect ◽  
Fast Kinetics ◽  
Acidic Solutions ◽  
Ph Values ◽  
Hydronium Ions ◽  
Layered Clays ◽  
Aqueous Environments ◽  
Back Exchange ◽  
Ph Range ◽  
Layered Clay

A Pillared Layered Clay (PILC), code-named FREZEN, has been developed as a potential antidote for trapping radiostrontium in the gastrointestinal tract of ruminants. The ion exchange behaviour of FREZEN has been studied, with particular emphasis on Sr+2 exchange in acidic solutions. As for most sorbents and ion ex­ changers, strontium uptake by FREZEN remains sufficiently good over a pH range of 5-11, but a sharp diminution is observed at pH values below 4. Furthermore, at lower pH values, hydronium ions (H3O+) successfully compete with strontium cations already uptaken by FREZEN. An extended "back-exchange" effect, charac­terized by fast kinetics, is thus observed. In order to impede the diffusion and prevalence of Η3Ο+, a modification of the microporous space in FREZEN has been carried out via intercalation of suitable organic molecules. Work currently underway reveals that this approach is capable of improving the performance properties of the PILC. Experimental results with glycerol as the intercalated organic agen will be presented and discussed.

scholarly journals Effects of pH on the stability of cyanidin and cyanidin 3-O-β-glucopyranoside in aqueous solution

2015 ◽  
Vol 69 (5) ◽  
pp. 511-522 ◽  
Author(s):  
Violeta Rakic ◽  
Mihaela Skrt ◽  
Milena Miljkovic ◽  
Danijela Kostic ◽  
Dusan Sokolovic ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Visible Range ◽  
Colour Intensity ◽  
Colour Variation ◽  
Acidic Solutions ◽  
Absorbance Maximum ◽  
Ph Values ◽  
Effects Of Ph ◽  
The Stability ◽  
Ph Range

The colour variation, colour intensity and stability at various pH values (2.0, 4.0, 7.0 and 9.0) of cyanidin 3-O-?-glucopyranoside (Cy3Glc) and its aglycone cyanidin was investigated during a period of 8 hours storage at 25?C. Our data showed that pH of aqueous solution had impact on spectroscopic profile of cyanidin and Cy3Glc. Beginning with the most acidic solutions, increasing the pH induce bathochromic shifts of absorbance maximum in the visible range for all examined pH values (with the exception pH 4.0 for cyanidin), while the presence of the 3-glucosidic substitution induce hypsochromic shift. Compared to cyanidin, Cy3Glc has higher colour intensity and higher stability in the whole pH range, except at pH 7.0. The 3-glucosidic substitution influences on the colour intensity of Cy3Glc in the alkaline region. After 8-hour incubation of Cy3Glc and cyanidin at pH 2.0 and 25 ?C, 99% of Cy3Glc and only 27% of cyanidin remained unchanged.

Sorption and precipitation of iron on kaolinite. III. The solubility of iron(III) hydroxides precipated in the presence of kaolinite

Soil Research ◽  
1970 ◽  
Vol 8 (1) ◽  
pp. 107 ◽  
Author(s):  
AW Fordham
Keyword(s):  
Electron Microscope ◽  
Solubility Product ◽  
Reaction Times ◽  
Ionic Species ◽  
Total Iron ◽  
X Ray ◽  
Acidic Solutions ◽  
Ph Values ◽  
Solubility Products ◽  
Ph Range

Iron(111) hydroxides were precipitated upon kaolinite suspended in acidic solutions of either 0.15M NaCl or 0.15M NaClO4. The progress of the reaction was followed for up to 15 weeks by periodic measurements of pH values and total iron(111) concentrations in solution. Total iron(m) concentrations varied from 1 0 - 3 ~ to 2 x 10-7 and pH values from 2.2 to 4.4. In NaCl media, steady state conditions were reached within 4-5 weeks. Allowing for the various iron(III) ionic species present in the solution phase, the solubility product *K++S2 (= [Fe(OH)+2]/aH+) was found to be 4.9 x 10-3 (S.D. = 0.7 x 10-3 log*K++S2 = - 2.31; log Kso = - 38.9). Although the initial precipitates were amorphous, the presence of �-FeOOH in aged suspensions was detected by X-ray analysis, in agreement with electron microscope observations. In NaClO4 media, the solubility of precipitates decreased rapidly during the first 3 weeks and relatively slowly thereafter. Although equilibrium was obviously not established within 5 weeks and possibly not within 15 weeks, values of solubility products, constant over the whole pH range, were derived from results at both reaction times. For suspensions aged for 5 weeks, *K++S2 was 4.85 x 10-3 (S.D. = 0.75 x 10-3 ; logKso = -38.9), whilst for those at 15 weeks, *K++S2 was 2.45 x 10-3 (S.D. = 0.3 x 10-3; log Kso = -39.2). X-ray and infra-red analyses and electron microscope examination indicated the presence of lepidocrocite in the aged products. There was no evidence that either the type or the solubility of products formed on aging was influenced by the presence of kaolinite, although the clay accelerated the rate of crystal growth.

scholarly journals Switchable Coumarins for Ratiometric pH Sensing

2021 ◽  
Vol 8 ◽  
Author(s):  
Mercedes M. A. Mazza ◽  
Francesca Cardano ◽  
James D. Baker ◽  
Silvia Giordani ◽  
Françisco M. Raymo
Keyword(s):  
Photophysical Properties ◽  
Molecular Switches ◽  
Heterocyclic Ring ◽  
Ph Sensitive ◽  
Ph Sensing ◽  
Fast Kinetics ◽  
Fluorescence Measurements ◽  
Aqueous Environments ◽  
Ph Range ◽  
Ratiometric Ph Sensing

A fluorescent chromophore and a pH-sensitive heterocycle were integrated within a single covalent skeleton to generate four molecular switches with ratiometric fluorescence response. Upon acidification, the pH-sensitive heterocycle opens to shift bathochromically the absorption and emission bands of the fluorescent chromophore. As a result, an equilibrium between two species with resolved fluorescence is established with fast kinetics in aqueous environments. The relative amounts of the two interconverting forms and their relative emission intensities change with pH, providing the opportunity to probe this parameter ratiometrically with fluorescence measurements. Specifically, the resolved emissions of the two species can be collected in separate detection channels of the same microscope to map their ratio across a labeled sample and reconstruct its pH distribution ratiometrically with spatial resolution at the micrometer level. Additionally, the sensitivity of these molecular switches varies with the nature of the heterocyclic ring and with its substituents, allowing the possibility of regulating their response to a given pH range of interest with the aid of chemical synthesis. Thus, a family of valuable fluorescent probes for ratiometric pH sensing in a diversity of samples can emerge from the unique combination of structural and photophysical properties designed into our innovative molecular switches.

The Malachite Green Biodegradation in Bioreactors on Various pH Domains

2019 ◽  
Vol 70 (8) ◽  
pp. 2996-2999
Author(s):  
Viorel Gheorghe ◽  
Catalina Gabriela Gheorghe ◽  
Andreea Bondarev ◽  
Vasile Matei ◽  
Mihaela Bombos
Keyword(s):  
Malachite Green ◽  
Contact Time ◽  
Dominant Species ◽  
Wastewater Treatment Plants ◽  
Organic Substances ◽  
Biological Degradation ◽  
Growth Promoters ◽  
Ph Values ◽  
Biological Sludge ◽  
Ph Range

In the experimental study was studied the malachite green colorant biodegradation in biological sludge with biological activity. The biodegradability tests were carried out in laboratory bioreactors, on aqueous solutions of green malachite contacted with microorganisms in which the dominant species is Paramecium caudatum, in a pH range between 8 and 12, temperatures in the ranges 25-350C, using pH neutralizing substances and biomass growth promoters. The colorant initial concentrations and those obtained after biological degradation depending on the contact time, at certain pH values, were established through UV-Vis spectrometry. The studies have shown the measure of possible biological degradation of some organic substances with extended uses, with largely aromatic structure, resistance to biodegradation of microorganisms, commonly used in wastewater treatment plants.

scholarly journals Immobilization of Cd, Zn, and Pb from Soil Treated by Limestone with Variation of pH Using a Column Test

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Sung-Wook Yun ◽  
Chan Yu
Keyword(s):  
South Korea ◽  
Water Systems ◽  
Metal Mobility ◽  
Acid Solutions ◽  
Test Results ◽  
Column Test ◽  
Acidic Solutions ◽  
Ph Values ◽  
Metal Mines ◽  
Site Restoration

Decades of mining in South Korea have resulted in the contamination of large amounts of soil by metals. The most feasible approach to site restoration requires the use of a stabilization agent to reduce metal mobility. This study examined the leaching characteristics of limestone used as a stabilization agent when subjected to solutions of differing pH. In a laboratory-scale column test, solutions with pH values of 3.5, 4.6, and 5.6, representing acidic to nonacidic rainfall, were applied to soil mixed with limestone. Test results indicate that metal components can be released with the addition of acidic solutions, even if the soil is highly alkaline. Cd and Zn, in particular, exhibited abrupt or continuous leaching when exposed to acid solutions, indicating the potential for contamination of water systems as metal-laden soils are exposed to the slightly acidic rainfall typical of South Korea. Treatment using stabilization agents such as limestone may reduce leaching of metals from the contaminated soil. Stabilizing metal-contaminated farmland is an economical and feasible way to reduce pollutants around abandoned metal mines.

Study on desorption of Mn, Fe, and Mg from TMP and evaluation of the complexing strength of different chelating agents using side reaction coefficients 10th EWLP, Stockholm, Sweden, August 25–28, 2008

Holzforschung ◽  
2009 ◽  
Vol 63 (6) ◽  
Author(s):  
Kim Granholm ◽  
Pingping Su ◽  
Leo Harju ◽  
Ari Ivaska
Keyword(s):  
Citric Acid ◽  
Metal Ions ◽  
Chelating Agents ◽  
Side Reaction ◽  
Sodium Dithionite ◽  
Thermomechanical Pulp ◽  
Peroxide Bleaching ◽  
Ph Values ◽  
Reducing Environment ◽  
Ph Range

Abstract Chelation of thermomechanical pulp (TMP) was studied in this work. The desorption of Mn, Fe, and Mg due to their impact on peroxide bleaching was investigated. The desorption experiments were performed with EDTA, citric acid, oxalic acid, and formic acid as chelating agents at different pH. Chelation experiments with EDTA were carried out at pH 3–11. Sodium dithionite was used as the reducing agent in studying chelation with EDTA in a reducing environment. Mn was very effectively desorbed with EDTA from TMP at pH <10 and the reducing environment further improved the removal of all the studied metal ions from TMP with EDTA. Citric acid also removed Mn effectively from TMP at pH 5. The thermodynamic stability constants of different metal chelates do not present the correct picture of how strongly the metal ions are bound by the chelating agents in different conditions. But by means of the side reaction coefficients (α M(L)-coefficients) it is also theoretically possible to evaluate and compare the real binding strengths between the metal ions and different chelating agents at varying pH values and other solution conditions. In this study, a theory is given for the calculation of side reaction coefficients. Values of the α M(L)-coefficients, for the pH range 0–14, are presented for EDTA, DTPA, and also for some other new potential environmentally friendly chelating agents.

scholarly journals Effects of pH and Aeration on Sclerotium rolfsii sacc. Mycelial Growth, Sclerotial Production and Germination

2018 ◽  
Vol 7 (3) ◽  
pp. 123-129 ◽  
Author(s):  
Fakher Ayed ◽  
Hayfa Jabnoun-Khiareddine ◽  
Rania Aydi-Ben-Abdallah ◽  
Mejda Daami-Remadi
Keyword(s):  
Mycelial Growth ◽  
Sclerotium Rolfsii ◽  
Dry Weight ◽  
Ph Values ◽  
Effects Of Ph ◽  
Ph Range ◽  
Sclerotial Development ◽  
Sclerotial Germination

Sclerotium rolfsii is one of the devastating soilborne fungus responsible for significant plant losses. The effects of pH and aeration on pathogen mycelial growth, sclerotial production and germination were investigated for three Tunisian isolates. Optimal mycelial growth occurred at pH 6 for Sr2 and Sr3 isolates and at pH 6-7 for Sr1. Dry mycelial growth was optimum at pH values ranging between 4 and 7. Sclerotial initiation started on the 3rd day of incubation at all pH values tested and mature sclerotia were formed after 6 to 12 days. Optimal sclerotial production was noted at pH 5. The dry weight of 100 sclerotia varied depending on isolates and pH and occurred at pH range 4-7. At pH 9, mycelial growth, sclerotial production and dry weight of 100 sclerotia were restricted. The optimum sclerotial germination, noted after 24 h of incubation, varied depending on isolates and pH and occurred at pH 4-9. Mycelial growth was optimum in aerated plates with a significant isolates x aeration treatments interaction. Sclerotial initiation occurred at the 3rd day of incubation and mature sclerotia were observed after 6-9 days. Sclerotial development was very slow in completely sealed plates and dark sclerotia were produced only after 15 days of incubation. The highest sclerotial yields were noted in aerated plates. The highest dry weight of 100 sclerotia for Sr1 isolate was recorded in ½ sealed, no sealed and completely sealed plates, while for Sr2, it was noted in ½ and ⅔ sealed plates. For Sr3, the maximum dry weight of 100 sclerotia was recorded in ½, ⅔ and completely sealed plates. Germination of S. rolfsii sclerotia, after 24 h of incubation, did not vary significantly depending on aeration treatments and ranged from 90 to 100% for all isolates.

Decline of Mysis relicta During the Acidification of Lake 223

1983 ◽  
Vol 40 (11) ◽  
pp. 1905-1911 ◽  
Author(s):  
R. W. Nero ◽  
D. W. Schindler
Keyword(s):  
Confidence Limits ◽  
Experimental Lakes Area ◽  
Mysis Relicta ◽  
Ph Values ◽  
Northwestern Ontario ◽  
Population Comparisons ◽  
Acidification Of Lake ◽  
Ph Range ◽  
Shield Lakes ◽  
Direct Toxicity

The population size of Mysis relicta in Lake 223 of the Experimental Lakes Area, northwestern Ontario, decreased from 6 700 000 ± 1 330 000 (± 95% confidence limits) during August of 1978, to 270 000 ± 75 000 during August of 1979, a 96% decrease. Because Mysis, a cold stenotherm, is restricted to the metalimnion and hypolimnion of lakes during summer, the pH range encountered by the population was 5.51 to 6.32 in 1978 and 5.23 to 6.10 in 1979, even though mean pH values in epilimnion waters for the 2 yr were 5.84 and 5.60. A decrease in pH of its habitat from 6.2 to 5.6 during fall overturn in 1979 caused the elimination of the remaining 4% of the population. Comparisons with four control lakes suggested that the decline and disappearance were not normal occurrences in unstressed lakes. Concentrations of Zn, Al, Mn, Fe, Cd, Cu, Ni, and Hg in Lake 223 water were low, and concentrations in Mysis were less than or equal to those in animals from five control lakes, suggesting that the decline in this species was not due to the toxic effects of metals. All size classes were affected, so that direct toxicity of hydrogen ion may be responsible for this abrupt population collapse. These results suggest that Mysis may be a useful early indicator of acidification damage to Precambrian Shield lakes.

Surface charge on kaolinites in aqueous suspension

Soil Research ◽  
1976 ◽  
Vol 14 (2) ◽  
pp. 197 ◽  
Author(s):  
MDA Bolland ◽  
AM Posner ◽  
JP Quirk
Keyword(s):  
Surface Charge ◽  
Positive Charge ◽  
Aqueous Suspension ◽  
Isomorphous Substitution ◽  
Ph Values ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Decreasing Ph ◽  
Ph Range ◽  
Exchange Technique

The surface charge of several natural kaolinites was measured in the pH range 3-10 using an exchange technique. The positive charge was found to increase with decreasing pH and sometimes to increase with increasing ionic strength; it occurred on the kaolinites at pH values as high as 9 and 10 and was particularly evident at high ionic strengths. The positive surface charge on kaolinites is thought to be due to exposed alumina such as is found on oxide surfaces. Aluminium was found to dissolve from kaolinite at pH values beiow about 6.5. Aluminium dissolution increased with decreasing pH and time. When the proportion of dissolved aluminium ions balancing negative surface charge was taken into account, the negative and net negative surface charge on kaolinite was concluded to be largely due to pH independent charge resulting from isomorphous substitution, together with some pH dependent charge due to exposed SiOH sites. If Na+ was the index cation, dissolved aluminium ions from the clay replaced some of the Na+ balancing the negative surface charge. However, when Cs+ was the index cation, less Cs+ balancing the negative surface charge on the clay was replaced by dissolved aluminium. As the concentration of either Na+ or Cs+ was increased, less dissolved aluminium replaced the index cation as a counteraction to the negative surface charge.

scholarly journals Optimal pH in chlorinated swimming pools – balancing formation of by-products

2013 ◽  
Vol 11 (3) ◽  
pp. 465-472 ◽  
Author(s):  
Kamilla M. S. Hansen ◽  
Hans-Jørgen Albrechtsen ◽  
Henrik R. Andersen
Keyword(s):  
Body Fluid ◽  
Product Formation ◽  
Swimming Pools ◽  
Batch Experiments ◽  
Ph Values ◽  
Precursor Ratio ◽  
Decreasing Ph ◽  
Ph Range ◽  
By Products ◽  
Optimal Ph

In order to identify the optimal pH range for chlorinated swimming pools, the formation of trihalomethanes, haloacetonitriles and trichloramine was investigated in the pH-range 6.5–7.5 in batch experiments. An artificial body fluid analogue was used to simulate bather load as the precursor for by-products. The chlorine-to-precursor ratio used in the batch experiments influenced the amounts of by-products formed, but regardless of the ratio the same trends in the effect of pH were observed. Trihalomethane formation was reduced by decreasing pH, but haloacetonitrile and trichloramine formation increased. To evaluate the significance of the increase and decrease of the investigated organic by-products at the different pH values, the genotoxicity was calculated based on literature values. The calculated genotoxicity was approximately at the same level in the pH range 6.8–7.5 and increased when pH was 6.7 or lower. An optimal pH range for by-products formation in swimming pools was identified at pH 7.0–7.2. In the wider pH range (pH 6.8–7.5), the effect on by-product formation was negligible. Swimming pools should never be maintained at lower pH than 6.8 since formation of both haloacetonitriles and trichloramine increase significantly below this value.

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