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 Chromium (VI) removal from aqueous solutions by purolite base anion-exchange resins with gel structure

2013 ◽  
Vol 19 (4) ◽  
pp. 615-628 ◽  
Author(s):  
Catalin Balan ◽  
Irina Volf ◽  
Doina Bilba
Keyword(s):  
Sorption Process ◽  
Isotherm Models ◽  
Order Kinetic ◽  
Gel Structure ◽  
Solution Ph ◽  
Sorption Data ◽  
Strong Base ◽  
Maximum Sorption Capacity ◽  
Chromium Vi ◽  
Exchange Resins

The removal of Cr (VI) from aqueous solution using two strong base anionic resins with gel structure, Purolite A-400 (styrene-divinylbenzene matrix) and Purolite A-850 (acrylic matrix) was investigated in batch technique. The sorption efficiency was determined as a function of phases contact time, solution pH, resin dose, temperature and initial Cr (VI) concentration. The percentage of Cr (VI) removed reaches maximum values (up to 99 %) in the pH range 4 - 5.3 under a resin dose of 6 g/L and of Cr (VI) concentration up to 100 mg/L. An increase in temperature has a positive effect on the Cr (VI) sorption process. The equilibrium sorption data were fitted with the Freundlich, Langmuir and Dubinin-Radushkevich isotherm models, using both linear and nonlinear regression method. The Langmuir model very well verifies the experimental data and gives the maximum sorption capacity of 120.55 mg Cr (VI)/g and 95.82 mg Cr (VI)/g for A-400 and A-850 resins, respectively. The thermodynamic study and mean free energy of sorption values calculated using Dubinin-Radushkevich equation indicated the sorption is a chemical endothermic process. The kinetic data were well described by pseudo-second order kinetic equation and the sorption process is controlled by external (film) diffusion and intraparticle diffusion.

Chromium Removal from Aqueous Solution by Microwave-Modified Phosphogypusum

2014 ◽  
Vol 955-959 ◽  
pp. 16-20 ◽  
Author(s):  
Ping Ning ◽  
Lei Shi ◽  
Yue Hong Yang ◽  
Yang Cheng
Keyword(s):  
Aqueous Solution ◽  
Contact Time ◽  
Adsorption Process ◽  
Maximum Adsorption Capacity ◽  
Solution Ph ◽  
Freundlich Model ◽  
Chromium Vi ◽  
Removal Capacity ◽  
Ph Range ◽  
Best Fit

The removal of chromium (VI) ions from aqueous solution by microwave-modified phosphogypsum was studied. The removal capacity of microwave-modified phosphogypsum for chromium (VI) ions was examined as a function of solution pH, contact time, adsorbent dosage. Before a series of the adsorption studies, phosphogypsum was pre-conditioned with microwave. It was observed that the adsorption of the chromium (VI) ions onto the phosphogypsum in the pH range of 2 and 11. The chromium (VI) adsorption process was described with the Langmuir and Freundlich theories, and the Freundlich model indicated the best fit to the adsorption process. Maximum adsorption capacity of microwave-modified phosphogypsum was found to be 3.126 mg g−1. The results proved that the microwave-modified phoshogypsum is a suitable adsorbent for the removal of chromium (VI) ions from aqueous solution.

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 &lt; 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.

scholarly journals Potentiating Effect of Mandelate and Lactate on Chemically Induced Germination in Members of Bacillus cereus Sensu Lato

2017 ◽  
Vol 83 (24) ◽  
Author(s):  
Alistair H. Bishop
Keyword(s):  
Bacillus Cereus ◽  
Large Scale ◽  
Germination Rate ◽  
Dependent Manner ◽  
Clostridium Sporogenes ◽  
Specific Chemical ◽  
Content Type ◽  
Ph Range ◽  
Significant Discovery ◽  
The Impact

ABSTRACT Endospores of the genus Bacillus can be triggered to germinate by a limited number of chemicals. Mandelate had powerful additive effects on the levels and rates of germination produced in non-heat-shocked spores of Bacillus anthracis strain Sterne, Bacillus cereus, and Bacillus thuringiensis when combined with l-alanine and inosine. Mandelate had no germinant effect on its own but was active with these germinants in a dose-dependent manner at concentrations higher than 0.5 mM. The maximum rate and extent of germination were produced in B. anthracis by 100 mM l-alanine with 10 mM inosine; this was equaled by just 25% of these germinants when supplemented with 10 mM mandelate. Half the maximal germination rate was produced by 40% of the optimum germinant concentrations or 15% of them when supplemented with 0.8 mM mandelate. Germination rates in B. thuringiensis were highest around neutrality, but the potentiating effect of mandelate was maintained over a wider pH range than was germination with l-alanine and inosine alone. For all species, lactate also promoted germination in the presence of l-alanine and inosine; this was further increased by mandelate. Ammonium ions also enhanced l-alanine- and inosine-induced germination but only when mandelate was present. In spite of the structural similarities, mandelate did not compete with phenylalanine as a germinant. Mandelate appeared to bind to spores while enhancing germination. There was no effect when mandelate was used in conjunction with nonnutrient germinants. No effect was produced with spores of Bacillus subtilis, Clostridium sporogenes, or C. difficile. IMPORTANCE The number of chemicals that can induce germination in the species related to Bacillus cereus has been defined for many years, and they conform to specific chemical types. Although not a germinant itself, mandelate has a structure that is different from these germination-active compounds, and its addition to this list represents a significant discovery in the fundamental biology of spore germination. This novel activity may also have important applied relevance given the impact of spores of B. cereus in foodborne disease and B. anthracis as a threat agent. The destruction of spores of B. anthracis, for example, particularly over large outdoor areas, poses significant scientific and logistical problems. The addition of mandelate and lactate to the established mixtures of l-alanine and inosine would decrease the amount of the established germinants required and increase the speed and level of germination achieved. The large-scale application of “germinate to decontaminate” strategy may thus become more practicable.

scholarly journals Adsorption of Pollutants from Aqueous Solutions Using Activated and Non-Activated Oak Shells: Parametric and Fractional Factorial Design Study. Part II. Removal of Phenol and Dyes

2003 ◽  
Vol 21 (2) ◽  
pp. 189-198
Author(s):  
Sameer Al-Asheh ◽  
Fawzi Banat ◽  
Rana Saeidi ◽  
Salam Abu Zaid
Keyword(s):  
Methylene Blue ◽  
Aqueous Solutions ◽  
Factorial Design ◽  
Fractional Factorial Design ◽  
Sorption Process ◽  
Fractional Factorial ◽  
Phenol Concentration ◽  
Blue Dye ◽  
Batch Adsorption ◽  
Solution Ph

As in Part I, non-activated (natural) and chemically activated oak shells were evaluated for their ability to remove phenol and Methylene Blue (as a typical dye component) from aqueous solutions. Batch adsorption experiments were conducted to investigate the effect of contact time, sorbent concentration, phenol concentration and the pH of the solution on the sorption process. Activated oak shells adsorbed more phenol than natural oak shells under the same conditions. A decrease in sorbent concentration or an increase in phenol concentration or solution pH resulted in an increase in phenol uptake by the oak shells. The uptake of Methylene Blue increased with decreasing sorbent concentration and with an increase in the dye concentration, but decreased significantly with solution pH. According to the fractional factorial design technique, the sorbent type employed (natural or activated) had the most significant influence on phenol or Methylene Blue uptake followed by sorbent concentration and then sorbate concentration. Interaction amongst the different operating variables played an important role in the uptake of phenol or Methylene Blue dye by the adsorbent considered.

Removal of Cr(VI) from Aqueous Solution by Acid Treated Fungal Biomass

2011 ◽  
Vol 197-198 ◽  
pp. 131-135
Author(s):  
Li Fang Zhang ◽  
Ying Ying Chen ◽  
Wen Jie Zhang
Keyword(s):  
Aqueous Solution ◽  
Fungal Biomass ◽  
Adsorption Model ◽  
Solution Ph ◽  
Initial Concentration ◽  
Biosorption Capacity ◽  
Penicillium Sp ◽  
Chromium Vi ◽  
Equilibrium Data ◽  
Biosorption Equilibrium

Biosorption of chromium (VI) ions from aqueous solution with fungal biomass Penicillium sp. was investigated in the batch system. The influence of contact time, solution pH, biosorbent concentration, initial concentration of Cr (VI) ions and temperature on biosorption capacity of Cr (VI) ions was studied. The uptake of Cr (VI) was highly pH dependent and the optimum pH for biosorption of Cr (VI) ions was found to be 2.0. Biosorption capacity of Cr (VI) ions decreased with increased biosorbent concentration and increased with increase in initial concentration of Cr (VI) ions. The experiment results also showed that high temperatures increased the biosorption capacity of Cr (VI) by fungal biomass. It was found that the biosorption equilibrium data were fitted very well to the kangmuir as well as to the Freundlich adsorption model. The maximum sorptive capacities obtained from the Langmuir equation at temperature of 20, 30 and 40°C were 25.91, 32.68 and 35.97 mg/g for Cr (VI) ions, respectively. The results of this study indicated that the fungal biomass of Penicillium sp. is a promising biosorbent for removal of chromium (VI) ions from the water.

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 Adsorption Study for Chromium (VI) on Iraqi Bentonite

2010 ◽  
Vol 7 (1) ◽  
pp. 745-756
Author(s):  
Baghdad Science Journal
Keyword(s):  
Adsorption Isotherm ◽  
Adsorption Process ◽  
Kinetic Equations ◽  
Bentonite Clay ◽  
Sorption Process ◽  
Adsorption Study ◽  
Chromium Vi ◽  
Freundlich Adsorption Isotherm ◽  
Different Temperatures ◽  
The Subject

The subject of this research involves studying adsorption to remove hexavalent chromium Cr(VI) from aqueous solutions. Adsorption process on bentonite clay as adsorbent was used in the Cr(VI) concentration range (10-100) ppm at different temperatures (298, 303, 308 and 313)K, for different periods of time. The adsorption isotherms were obtained by obeying Langmuir and Freundlich adsorption isotherm with R2 (0.9921-0.9060) and (0.994-0.9998), respectively. The thermodynamic parameters were calculated by using the adsorption process at four different temperatures the values of ?H, ?G and ?S was [(+6.582 ? +6.547) kJ.mol-1, (-284.560 ? -343.070) kJ.mol-1 and (+0.977 ? +1.117) kJ.K-1.mol-1] respectively. This data indicates the spontaneous sorption process. The kinetic study of adsorption process was studied depending on three kinetic equations: 1- Lagergren equation 2- Morris-Weber equation 3- Reichenberg equation

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.

scholarly journals Adsorption of Chromium (VI) on Calcium Phosphate: Mechanisms and Stability Constants of Surface Complexes

2017 ◽  
Vol 7 (3) ◽  
pp. 222 ◽  
Author(s):  
Ahmed Elyahyaoui ◽  
Kawtar Ellouzi ◽  
Hamzeh Al Zabadi ◽  
Brahim Razzouki ◽  
Saidati Bouhlassa ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Stability Constants ◽  
Surface Complexes ◽  
Chromium Vi
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