scholarly journals The effect of pH, organic ligand chemistry and mineralogy on the sorption of beryllium over time

2016 ◽  
Vol 13 (4) ◽  
pp. 711 ◽  
Author(s):  
Vanessa Boschi ◽  
Jane K. Willenbring
Keyword(s):  
Organic Ligand ◽  
Oxide Content ◽  
Soil Composition ◽  
Phosphorus Oxide ◽  
Solution Ph ◽  
Surface Stability ◽  
Kd Values ◽  
Geochemical Tracer ◽  
Ph Range ◽  
Strong Control

Environmental contextBeryllium is a toxic environmental contaminant but has many industrial and scientific applications. Our work explores the effects of soil composition on beryllium retention, focussing on organic matter, mineralogy and pH and concludes that phosphorus and sulfur oxides in addition to soil acidity are strong controls on beryllium mobility. These results aid in future predictions regarding the fate of beryllium in the environment. AbstractUnderstanding the chemical controls on beryllium sorption is fundamental when assessing its mobility as a pollutant and interpreting its concentration as a geochemical tracer of erosion, weathering and landscape surface stability. In order to evaluate the interactions of beryllium with soil- and aquatic-related materials, we selected model organic compounds and minerals to perform sorption experiments. The retention of beryllium by each of these compounds and minerals was evaluated over a pH range of 3–6 and at various equilibration times to determine which conditions allowed the greatest retention of beryllium. We conclude that most beryllium sorption occurred within 24h for both organic and mineral materials. However, equilibration required longer periods of time and was dependent on the solution pH and sorbent material. The pH exhibited a strong control on beryllium sorption with distribution coefficient (Kd) values increasing non-linearly with increasing pH. A system with a pH of 6 is likely to retain 79–2270% more beryllium than the same system at a pH of 4. Phosphonate retained the greatest amount of beryllium, with Kd values 2–30× greater than all other materials tested at a pH of 6. Therefore, soils containing larger amounts of phosphorus-bearing minerals could result in greater retention of beryllium relative to phosphorus-limited soils. Overall, soil composition, with an emphasis on phosphorus oxide content and pH, is an important property to consider when evaluating the capacity of a system to retain beryllium.

Kinetic of oxidation of methyl orange by vanadium(V) under conditions VO2+ and decavanadates coexist: Catalysis by Triton X-100 micellar medium

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Methyl Orange ◽  
Solution Ph ◽  
Vanadium Concentration ◽  
Limiting Behavior ◽  
First Order ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetic Pattern ◽  
Triton X ◽  
Kinetics Of

The kinetics of oxidation of methyl orange by vanadium(V) {V(V)} has been investigated in the pH range 2.3-3.79. In this pH range V(V) exists both in the form of decavanadates and VO2+. The kinetic results are distinctly different from the results obtained for the same reaction in highly acidic solution (pH < 1) where V(V) exists only in the form of VO2+. The reaction obeys first order kinetics with respect to methyl orange but the rate has very little dependence on total vanadium concentration. The reaction is accelerated by H+ ion but the dependence of rate on [H+] is less than that corresponding to first order dependence. The equilibrium between decavanadates and VO2+ explains the different kinetic pattern observed in this pH range. The reaction is markedly accelerated by Triton X-100 micelles. The rate-[surfactant] profile shows a limiting behavior indicative of a unimolecular pathway in the micellar pseudophase.

pH-induced hysteretic properties of phosphofructokinase purified from rat myocardium

1986 ◽  
Vol 250 (3) ◽  
pp. R505-R511 ◽  
Author(s):  
S. C. Hand ◽  
J. F. Carpenter
Keyword(s):  
Catalytic Activity ◽  
Metabolic Regulation ◽  
Inverse Correlation ◽  
Rat Myocardium ◽  
Solution Ph ◽  
Reversible Inactivation ◽  
Ph Range ◽  
Hysteretic Loss ◽  
Fructose 1,6 Bisphosphate

Phosphofructokinase (PFK) purified from the rat myocardium is reversibly inactivated under a pH regime approximating that reported for ischemic hearts. At pH 6.5 and 37 degrees C, the enzyme displays a hysteretic loss of activity during 60-min incubations, declining to 48% of control (pH 7.1, 37 degrees C) values. Citric acid increases the degree of inactivation (28% of control), whereas fructose 1,6-bisphosphate reduces the decline in activity. Simultaneous measurements of 90 decreases light scattering and catalytic activity suggest the inactivation is temporally linked to dissociation of active tetrameric enzyme into an inactive form of lower molecular weight. Fluorescence enhancement of the extrinsic probe sodium mansate, which binds preferentially to dimeric PFK, indicates that the equilibrium dimer concentration (cp1 infinity) increases as pH is lowered. This increase in cp1 infinity exhibits a strong inverse correlation (r = 0.984) with catalytic activity across the pH range of 8.0 to 6.5. Returning solution pH to 7.0 or above promotes a time-dependent reactivation and repolymerization of PFK. The rate of reactivation is increased at higher enzyme concentrations and in the presence of trimethylamine-N-oxide, a nitrogenous osmolyte noted for its ability to promote protein aggregation reactions. Thus these results demonstrate the capacity of rat heart PFK to undergo reversible inactivation and dissociation in vitro and represent the first phase of a two-part study testing the hypothesis that these pH-induced hysteretic processes are operative in the ischemic myocardium. The data are evaluated in terms of the potential roles of hysteretic enzymes in metabolic regulation.

scholarly journals Human insulin polymorphism upon ligand binding and pH variation: the case of 4-ethylresorcinol

IUCrJ ◽  
2015 ◽  
Vol 2 (5) ◽  
pp. 534-544 ◽  
Author(s):  
S. Fili ◽  
A. Valmas ◽  
M. Norrman ◽  
G. Schluckebier ◽  
D. Beckers ◽  
...  
Keyword(s):  
Human Insulin ◽  
Organic Ligand ◽  
European Synchrotron Radiation Facility ◽  
X Ray Diffraction ◽  
Ph Variation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Swiss Light Source ◽  
Crystallization Experiments ◽  
Ph Range

This study focuses on the effects of the organic ligand 4-ethylresorcinol on the crystal structure of human insulin using powder X-ray crystallography. For this purpose, systematic crystallization experiments have been conducted in the presence of the organic ligand and zinc ions within the pH range 4.50–8.20, while observing crystallization behaviour around the isoelectric point of insulin. High-throughput crystal screening was performed using a laboratory X-ray diffraction system. The most representative samples were selected for synchrotron X-ray diffraction measurements, which took place at the European Synchrotron Radiation Facility (ESRF) and the Swiss Light Source (SLS). Four different crystalline polymorphs have been identified. Among these, two new phases with monoclinic symmetry have been found, which are targets for the future development of microcrystalline insulin drugs.

scholarly journals Adsorption of selected azo dyes from an aqueous solution by activated carbon derived from Monotheca buxifolia waste seeds

2020 ◽  
Vol 15 (No. 3) ◽  
pp. 166-172 ◽  
Author(s):  
Ruqia Nazir ◽  
Muslim Khan ◽  
Riaz Ur Rehman ◽  
Shaukat Shujah ◽  
Mansoor Khan ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Activated Carbon ◽  
Azo Dyes ◽  
Solution Ph ◽  
Electron Microscopic ◽  
Adsorption Models ◽  
Electron Microscopic Image ◽  
Monotheca Buxifolia ◽  
Ph Range ◽  
Scanning Electron Microscopic Image

In this study, activated carbon derived from Monotheca buxifolia waste seeds was used for the adsorptive removal of a number of selected azo dyes such as Eriochrome Black T (EBT), Remazol brilliant blue (RBB), Remazol yellow (RY) and Remazol brilliant orange (RBO) from an aqueous solution by changing the initial dye concentration, adsorbent dosage, solution pH, contact time and temperature. A Fourier transform infrared spectroscopic analysis of the activated carbon showed the existence of hydroxyls, methyl, methylene, carbonyls, alkane and alkenes groups while the scanning electron microscopic image displayed the gradual formation of cavities and open pores on the surface. The results showed that as the amount of the adsorbent and the shaking time were increased, the removal percentage of the dye increased accordingly. Higher adsorption percentages were observed at a lower dye concentration and temperature in an acidic media at a pH range (1–5). The investigated data were evaluated with the Langmuir and Freundlich adsorption models. The maximum adsorption capacities obtained from the Langmuir model were 112.36, 96.34, 97.65 and 90.91 mg/g for EBT, RBB, RY and RBO, respectively. The results indicated that the electrostatic interaction was the main cause of the adsorption of these anionic azo dyes on the surface of the activated carbon.

Electrodeposition of Copper / Cuprous Oxide Nanocomposites

1996 ◽  
Vol 451 ◽  
Author(s):  
Jay A. Swrrzer ◽  
Eric W. Bohannan ◽  
Teresa D. Golden ◽  
Chen-Jen Hung ◽  
Ling-Yuang Huang ◽  
...  
Keyword(s):  
Phase Composition ◽  
Cuprous Oxide ◽  
Nanocomposite Films ◽  
Constant Current ◽  
Oxide Content ◽  
Copper Metal ◽  
Solution Ph ◽  
Mole Percent ◽  
Strong Function ◽  
Current Densities

ABSTRACTNanocomposite films of copper metal and cuprous oxide were electrodeposited at room temperature from an alkaline copper(11) lactate solution. The electrode potential oscillated spontaneously during constant-current deposition of the composites. The oscillations were periodic in a stirred solution, but became chaotic in unstirred solution. For a given current density the phase composition was a strong function of solution pH. As the pH was increased, the cuprous oxide content increased. At pH 12, no oscillations were observed, and pure cuprous oxide was deposited. At pH 9, the phase composition varied from pure cuprous oxide at current densities below 0.1 mA/cm2 to 96 mole percent copper at 2.5 mA/cm2.

Probing acid/base chemistry and adsorption mechanisms of hydrolysable Al(iii) species with a clay system in aqueous solution

RSC Advances ◽  
2016 ◽  
Vol 6 (115) ◽  
pp. 114171-114182 ◽  
Author(s):  
Yanfang Huang ◽  
Wencui Chai ◽  
Guihong Han ◽  
Jiongtian Liu ◽  
Hongyang Wu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Acid Base ◽  
Solution Ph ◽  
Adsorption Mechanisms ◽  
Clay System ◽  
Ph Range

The acid/base chemistry of hydrolysable Al(iii) species with a clay (bentonite and kaolin) system was investigated at 35 °C in the expanded solution pH range from 1 to 9.

Biosorption of Heavy Metals by Pseudomonas aeruginosa Isolated from a Petroleum Contaminated Site

2007 ◽  
Vol 20-21 ◽  
pp. 615-618 ◽  
Author(s):  
R. Maria Pérez ◽  
A. Abalos ◽  
José Manuel Gómez ◽  
Domingo Cantero
Keyword(s):  
Heavy Metals ◽  
Pseudomonas Aeruginosa ◽  
Contaminated Site ◽  
Metallic Ions ◽  
Solution Ph ◽  
Initial Concentration ◽  
Metal Biosorption ◽  
Ph Range ◽  
The Individual ◽  
A Site

The study describes the sorption of Cr, Cu, Mn and Zn by Pseudomonas aeruginosa AT18 isolated from a site contaminated with petroleum and heavy metals. The concentrations studied (mgL-1) were Cr-50, Cu-49, Mn-60 and Zn-70. The solution pH and ionic strength were very important factors in the metal biosorption performance and the biosorption capacity of Pseudomonas aeruginosa AT18 for Cr3+ Cu2+, Mn2+ and Zn2+. In aqueous solution the biosorption increased with increasing pH in the range 5.46-7.72. The results obtained in the experimental assays show that Pseudomonas aeruginosa AT18 has the capacity for biosorption of the metallic ions Cr3+, Cu2+ and Zn2+ in solutions, although its capacity for the sorption of manganese is low (22.39 mg Mn2+/g of biomass) in comparison to the Cr3+, Cu2+ and Zn2+ ions, as shown by the individual analyses. However, 20% of the manganese was removed from an initial concentration of 49.0 mgL- 1, with a Qm value similar to that obtained in solutions containing mixtures of Cr3+ Cu2+, Mn2+ and Zn2+. The chromium level sorbed by Pseudomonas aeruginosa AT18 biomass was higher than that for Cu, Mn and Zn, with 100% removal in the pH range 7.00-7.72 and a Qm of 121.90-200.00 mg of Cr3+/g of biomass. The remove of Cr, Cu and Zn are a result also of precipitation processes.

scholarly journals On the pH-dependent strontium adsorption by Al-PILCs, impregnated with carboxylate groups of various acid strengths

2019 ◽  
Vol 11 ◽  
Author(s):  
C. A. Papachristodoulou ◽  
P. A. Assimakopoulos ◽  
N-H. J. Gangas
Keyword(s):  
Acid Strength ◽  
Adsorption Properties ◽  
Solution Ph ◽  
Cation Uptake ◽  
Carboxylate Groups ◽  
Constant Ph ◽  
Strontium Ions ◽  
Ph Dependent ◽  
Ph Range

The impregnation of a PILC with carboxylate groups is proposed as a means to improve the adsorption properties of the material for strontium ions. The role of solution pH and carboxylate acid strength in the functionalization of the organic groups is probed by base titrations. In comparing the pristine-PILC with PILCs carrying either oxalate or acetate impregnates, enhanced strontium uptake is evidenced by the modified solids, initiated at pH 6 and 8 in the presence of oxalate and acetate, respectively. The effect on uptake is higher in the former case, amounting to an increase in strontium adsorption by a factor between two and three, depending on the pH range. To further elucidate the significance of the carboxylate acid strength in cation uptake phenomena, strontium adsorption isotherms are presented for PILCs carrying acetate, oxalate, malonate and citrate groups. The results demonstrate that, at constant pH, adsorption increases with increasing acid strength

scholarly journals Surface Complexation of Chromium(VI) on Iron(III) Hydroxide: Mechanisms and Stability Constants of Surfaces Complexes

2021 ◽  
Vol 21 (3) ◽  
pp. 679
Author(s):  
Mhamed Hmamou ◽  
Fatima Ezzahra Maarouf ◽  
Bouchaib Ammary ◽  
Abdelkebir Bellaouchou
Keyword(s):  
Chemical Nature ◽  
Chemical Interaction ◽  
Surface Complexation ◽  
Sorption Process ◽  
Solution Ph ◽  
Surface Complexes ◽  
Specific Chemical ◽  
Chromium Vi ◽  
Liquid Phases ◽  
Ph Range

The adsorption of chromate ions H2-yA (y = 1, 2, and A = CrO42–) on iron(III) hydroxide was conducted as a function of adsorbent mass, solution pH, and hydration time. The surface complexation technique, based on the examination of the chromate distribution between the solid and liquid phases, was adopted to predict the adsorption mechanism. To specify stoichiometry of the chromate surface complexes, the proton (n > 0), and hydroxyl (n < 0) ion-exchange was evaluated at a pH range of 2–12. The obtained “n” values are ranging between -1 and 1. As a result, the sorption process involved specific chemical interaction with surface sites, resulting in 1H+ and 1OH– release of the adsorbate molecule. The surface species identified were ; ; ; ; ; ; ;  and . The logarithmic values of their complexing constants were: log K00 = 1.81 ± 0.04; log K11 = -3.53 ± 0.07; log K21 = -1.03 ± 0.23, log K1-1 = 7.15 ± 0.14 and log K2-1 = 9.62 ± 0.53. The results showed that the chromate adsorption on Fe(III) hydroxide was of electrostatic and chemical nature at pH lower than 5.5, and only of chemical nature at pH superior to 5.5. Taking into account these considerations, Fe(III) hydroxide could be considered an excellent sorbent for the removal of Cr(VI) from wastewater solutions.

scholarly journals Acid-base transport model of interfacial reactions for dynamic pH response quantification and regulation

2021 ◽  
Author(s):  
Fengjun Yin ◽  
Xiaohui Yang ◽  
Lei Zheng ◽  
Ling Fang ◽  
Sha Wang ◽  
...  
Keyword(s):  
Transport Model ◽  
Interfacial Reactions ◽  
Limiting Current ◽  
Parameter Determination ◽  
Acid Base ◽  
Solution Ph ◽  
Model Calculations ◽  
Ph Response ◽  
Ph Range ◽  
Parameter Values

The dynamic pH response resulting from acid-base transport of interfacial reactions greatly influences the kinetic performance and process mechanism, but its theoretical foundation is lacked. Herein, a generalized acid-base transport model is established owing to the success in deriving buffer transport equations and is experimentally through the relationships of buffer transport limiting current versus solution pH and buffer concentration (CB). The relationships bring forth the parameter determination methods of buffers with the superiority of facile survey of practical parameter values. Based on model calculations, the dynamic pH response is drawn as a j‒pH diagram to show the buffer transport law in the full pH range, highlighting the rate-limiting effect. The buffer operation principles are graphically presented as CB‒ΔpH diagrams to aid economic buffer applications. This study has laid the foundation for quantification and regulation of dynamic pH response and is of wide interest to the chemistry encompassing interfacial processes.

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