Kinetics of phosphate adsorption on iron oxides formed under the influence of citrate

2000 ◽  
Vol 80 (3) ◽  
pp. 445-454 ◽  
Author(s):  
C. Liu ◽  
P. M. Huang
Keyword(s):  
Activation Energy ◽  
Citric Acid ◽  
Organic Acids ◽  
Surface Chemistry ◽  
Iron Oxides ◽  
Phosphate Adsorption ◽  
Exponential Factor ◽  
Structural Perturbation ◽  
Fe Oxides ◽  
The Impact

The influence of organic acids on the formation of Fe oxyhydroxides and oxides has been intensively studied. However, scant attention has been paid to the subsequent effect on surface chemistry of the Fe oxides formed. The kinetics and mechanisms of phosphate adsorption by the Fe oxides formed in the presence of citrate ligands at initial citrate/Fe(II) molar ratios (MR) of 0, 0.001, 0.01, and 0.1 were investigated using the conventional batch method. The adsorption studies were conducted at the initial phosphate concentration of 0.5 mM and pH 4.0 during the reaction period from 2 min to 56 h at 278, 288, 298, and 313 K. The results show that the phosphate adsorption followed multiple second-order kinetics and had two distinct rates in each reaction system. The amount, rate coefficient, activation energy and pre-exponential factor of phosphate adsorption by the Fe oxides formed greatly varied with their structural and surface properties. These properties, which included crystal structure, specific surface area, surface porosity, surface geometry, and point of zero salt effect (PZSE), differed significantly with the initial citrate/Fe(II) MR at which Fe oxides were formed. The results of this study have cast the light on the role of organic acids such as citric acid in influencing the surface chemistry of naturally occurring Fe oxides through fundamental structural perturbation and the impact on the dynamics of phosphate in terrestrial and aquatic environments. Key words: Kinetics, activation energy, pre-exponential factor, phosphate, iron oxides, citric acid, structural perturbation

scholarly journals Changes in the biochemical components of mandarin fruits after pest control in the Republic of Abkhazia

2021 ◽  
Vol 935 (1) ◽  
pp. 012009
Author(s):  
L Ayba ◽  
L Kulava ◽  
N Karpun ◽  
N Konnov ◽  
O Belous ◽  
...  
Keyword(s):  
Citric Acid ◽  
Organic Acids ◽  
Pest Control ◽  
Standard Treatment ◽  
Soluble Carbohydrates ◽  
Predominant Form ◽  
Biochemical Components ◽  
The Republic ◽  
The Impact ◽  
Acid Index

Abstract The study assessing biochemical components (sugars and organic acids) in mandarin fruits after pest control was carried out in matured plantings of cv. Unshiu mandarin in the Republic of Abkhazia in 2019-2020. The treated fruits contained a greater amount of soluble carbohydrates than the fruits in control. The predominant form of monosaccharides is fructose (17.78-17.85 g/l, with 11.89 g/l in the control) in the fruits from the standard treatment and in variant 6 (with a combination of Metamax, Vermitek and Karate Zeon), which is preferable, since it has the greatest sweetness (173 units), providing a sweeter taste of the fruit. According to the content of organic acids, variants 6 and 8 (four treatments with Diatomite, 6%) were distinguished, the content of citric acid on which was 11.86-11.3 mg/l. A more balanced taste of the fruit was in variants 6, 7 (four treatments with Diatomite, 3%) and 8 (sugar-acid index from 7.7 to 7.9 units). Taking into account the content of basic acids and sugars in mandarin fruits, it is possible to predict the impact of insecticides and their combinations on their basic taste properties.

Biosolids Incorporation in Mediterranean Soils Increase Phosphate Adsorption

2021 ◽  
Author(s):  
Yaniv Freiberg ◽  
Pinchas Fine ◽  
Michael Borisover ◽  
Shahar Baram
Keyword(s):  
Adsorption Capacity ◽  
The Other ◽  
Solid Matrix ◽  
Phosphate Adsorption ◽  
Adsorption Parameters ◽  
Adsorption Sites ◽  
Fe Oxides ◽  
Wide Range ◽  
Mediterranean Soils ◽  
The Impact

<p>Contradictory data exists on the impact of biosolids incorporation on ortho-phosphate (IP) binding to arid and semi-arid Mediterranean soils. We used two mature organic amendments (OA) with low IP solubility to study the effect of OAs addition on the IP adsorption parameters of Mediterranean soils. Seven soils, encompassing a wide range of mechanical, chemical and mineralogical properties, were mixed with a biosolids compost (DSC) at 9:1 ratio (w/w dry weight basis). The soils and mixtures were either incubated for seven years under constant temperature (30℃) and moisture content (80% of 30 kPa tension) or were unincubated. IP adsorption parameters were also measured in not-incubated soil DSC mixtures at 97:3 ratio. In all the soils, DSC addition significantly increased the IP adsorption capacities (by Langmuir's model) from 126 to 397 mg IP kg<sup>-1</sup> in the soils to 254 through 669 mg IP kg<sup>-1 </sup>in the soil-DSC-mixtures. The increased capacities were accompanied by a significant decrease in the adsorption affinities, from values of 0.12 to 1.02 L kg<sup>-1</sup> in the soils to 0.05 and 0.25 L kg<sup>-1</sup> in the mixtures. Biosolids addition at 97:3 ratio had a similar effect on the IP adsorption parameters as the 9:1 ratio. These two IP adsorption parameters continued to change along the incubation. The other OA tested was a municipal solid waste compost (MSWC), which was mixed with two montmorillonitic soils at 97:3 ratio (soil:OA), one with high lime and low Al/Fe-oxides contents and the other with low lime and high Al/Fe-oxides content. OA addition increased the IP adsorption capacity in the lime-rich soil, while it did not affect the other. Overall, our results show that the solid matrix of the two OA's used by us embodied IP adsorption sites, most likely through metal bridging with Ca<sup>2+</sup>, which increases the total adsorption capacity of the soil-OA mixture. Concomitantly, DOM from the OAs competes with IP on adsorption sites reducing the soil's adsorption capacity. The magnitude of each one of these two processes depends on the soil and the added OA characteristic and will determine the overall change in the soil's capability to retain IP after biosolids incorporation.</p><p> </p>

Microscopic Interpretation of Arrhenius Parameters

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Transition State Theory ◽  
Average Energy ◽  
Zero Point ◽  
State Theory ◽  
Exponential Factor ◽  
Quantum Tunnelling ◽  
Microscopic Interpretation ◽  
The Difference

This chapter reviews the microscopic interpretation of the pre-exponential factor and the activation energy in rate constant expressions of the Arrhenius form. The pre-exponential factor of apparent unimolecular reactions is, roughly, expected to be of the order of a vibrational frequency, whereas the pre-exponential factor of bimolecular reactions, roughly, is related to the number of collisions per unit time and per unit volume. The activation energy of an elementary reaction can be interpreted as the average energy of the molecules that react minus the average energy of the reactants. Specializing to conventional transition-state theory, the activation energy is related to the classical barrier height of the potential energy surface plus the difference in zero-point energies and average internal energies between the activated complex and the reactants. When quantum tunnelling is included in transition-state theory, the activation energy is reduced, compared to the interpretation given in conventional transition-state theory.

scholarly journals The Role of Surface Chemistry in the Efficacy of Protein and DNA Microarrays for Label-Free Detection: An Overview

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1026
Author(s):  
Elisa Chiodi ◽  
Allison M. Marn ◽  
Matthew T. Geib ◽  
M. Selim Ünlü
Keyword(s):  
Surface Chemistry ◽  
Surface Functionalization ◽  
Dna Microarrays ◽  
Label Free ◽  
Polymeric Coatings ◽  
Label Free Detection ◽  
Particle Imaging ◽  
Single Particle Imaging ◽  
The Impact

The importance of microarrays in diagnostics and medicine has drastically increased in the last few years. Nevertheless, the efficiency of a microarray-based assay intrinsically depends on the density and functionality of the biorecognition elements immobilized onto each sensor spot. Recently, researchers have put effort into developing new functionalization strategies and technologies which provide efficient immobilization and stability of any sort of molecule. Here, we present an overview of the most widely used methods of surface functionalization of microarray substrates, as well as the most recent advances in the field, and compare their performance in terms of optimal immobilization of the bioreceptor molecules. We focus on label-free microarrays and, in particular, we aim to describe the impact of surface chemistry on two types of microarray-based sensors: microarrays for single particle imaging and for label-free measurements of binding kinetics. Both protein and DNA microarrays are taken into consideration, and the effect of different polymeric coatings on the molecules’ functionalities is critically analyzed.

scholarly journals Ingredient-Dependent Extent of Lipid Oxidation in Margarine

Antioxidants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 105
Author(s):  
Sarah Fruehwirth ◽  
Sandra Egger ◽  
Dennis Kurzbach ◽  
Jakob Windisch ◽  
Franz Jirsa ◽  
...  
Keyword(s):  
Citric Acid ◽  
Lipid Oxidation ◽  
Oxidative Stability ◽  
Green Tea ◽  
Acyl Chain ◽  
Green Tea Extract ◽  
Tocopheryl Acetate ◽  
Tea Extract ◽  
The Impact ◽  
Β Carotene

This study reports the impact of margarine-representative ingredients on its oxidative stability and green tea extract as a promising antioxidant in margarine. Oil-in-water emulsions received much attention regarding factors that influence their oxidative stability, however, water-in-oil emulsions have only been scarcely investigated. Margarine, a widely consumed water-in-oil emulsion, consists of 80–90% fat and is thermally treated when used for baking. As different types of margarine contain varying additives, their impact on the oxidative stability of margarine during processing is of pressing importance. Thus, the influence of different ingredients, such as emulsifiers, antioxidants, citric acid, β-carotene and NaCl on the oxidative stability of margarine, heated at 80 °C for 1 h to accelerate lipid oxidation, was analyzed by the peroxide value and oxidation induction time. We found that monoglycerides influenced lipid oxidation depending on their fatty acyl chain. α-Tocopheryl acetate promoted lipid oxidation, while rosemary and green tea extract led to the opposite. Whereas green tea extract alone showed the most prominent antioxidant effect, combinations of green tea extract with citric acid, β-carotene or NaCl increased lipid oxidation in margarine. Complementary, NMR data suggested that polyphenols in green tea extracts might decrease lipid mobility at the surface of the water droplets, which might lead to chelating of transition metals at the interface and decreasing lipid oxidation.

Enrichment of hydrogen production from fruit waste biomass using ozonation assisted with citric acid

2021 ◽  
pp. 0734242X2110103
Author(s):  
Anbazhagan Sethupathy ◽  
Pushkar Kumar Pathak ◽  
Palani Sivashanmugam ◽  
Chelliah Arun ◽  
Jayakumar Rajesh banu ◽  
...  
Keyword(s):  
Citric Acid ◽  
Hydrogen Production ◽  
Suspended Solid ◽  
Net Energy ◽  
Waste Biomass ◽  
Acid Pretreatment ◽  
Disintegration Time ◽  
Fruit Waste ◽  
The Impact ◽  
Acid Dosage

In this study, the impact of ozonation abetted with the citric acid pretreatment (OZCAP) method on fruit waste was investigated for ameliorating hydrogen production. Initially, the ozonation pretreatment (OZP) method was performed by varying ozone (O3) dosage and disintegration time. At optimized conditions (O3 dosage (0.04 g/g suspended solid; SS) and disintegration time (40 minutes)), 17.6% of liquefied organics emancipate rate (LER) and 13.5% of SS reduction were perceived. Further augmenting LER of fruit waste, OZCAP method was proceeded by varying citric acid dosage and disintegration time at an optimized OZP dosage (0.04 g/g SS). A higher LER (24.4%) and SS reduction (19%) were described at an optimal citric acid dosage (0.03 g/g SS) and disintegration time (20 minutes). Then, the hydrogen production potential of OZCAP, OZP and raw fruit waste were evaluated in which OZCAP method exhibited a higher cumulative hydrogen production (30 mL/g volatile solids). Energy valuation reveals that OZCAP method exhibited a net energy of 3.7 kWh/kg of fruit waste.

scholarly journals Enhanced Electrokinetic Remediation for the Removal of Heavy Metals from Contaminated Soils

2021 ◽  
Vol 11 (4) ◽  
pp. 1799
Author(s):  
Claudio Cameselle ◽  
Susana Gouveia ◽  
Adrian Cabo
Keyword(s):  
Heavy Metals ◽  
Citric Acid ◽  
Organic Acids ◽  
Contaminated Soils ◽  
Electrokinetic Remediation ◽  
Deionized Water ◽  
Soil Specimen ◽  
Removal Of Heavy Metals ◽  
Ph Conditions ◽  
Neutral Metal

The electrokinetic remediation of an agricultural soil contaminated with heavy metals was studied using organic acids as facilitating agents. The unenhanced electrokinetic treatment using deionized water as processing fluid did not show any significant mobilization and removal of heavy metals due to the low solubilization of metals and precipitation at high pH conditions close to the cathode. EDTA and citric acid 0.1 M were used as facilitating agents to favor the dissolution and transportation of metals. The organic acids were added to the catholyte and penetrated into the soil specimen by electromigration. EDTA formed negatively charged complexes. Citric acid formed neutral metal complexes in the soil pH conditions (pH = 2–4). Citric acid was much more effective in the dissolution and transportation out of the soil specimen of complexed metals. In order to enhance the removal of metals, the concentration of citric acid was increased up to 0.5 M, resulting in the removal of 78.7% of Cd, 78.6% of Co, 72.5% of Cu, 73.3% of Zn, 11.8% of Cr and 9.8% of Pb.

scholarly journals A Study of the Impact of Graphite on the Kinetics of SPS in Nano- and Submicron WC-10%Co Powder Compositions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 331-363
Author(s):  
Eugeniy Lantcev ◽  
Aleksey Nokhrin ◽  
Nataliya Malekhonova ◽  
Maksim Boldin ◽  
Vladimir Chuvil'deev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid Phase ◽  
Continuous Heating ◽  
Diffusion Creep ◽  
Hard Alloys ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Impact ◽  
Kinetics Of

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, QS(I). The value of QS(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, QS(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep).

The impact of harmfulness information on citric acid induced cough and urge-to-cough

2015 ◽  
Vol 31 ◽  
pp. 9-14 ◽  
Author(s):  
Thomas Janssens ◽  
Sarah Brepoels ◽  
Lieven Dupont ◽  
Omer Van den Bergh
Keyword(s):  
Citric Acid ◽  
The Impact

Physicochemical Characterization and Pyrolysis Kinetic Study of Sugarcane Bagasse Using Thermogravimetric Analysis

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Anil Kumar Varma ◽  
Prasenjit Mondal
Keyword(s):  
Activation Energy ◽  
Sugarcane Bagasse ◽  
Physicochemical Characterization ◽  
Maximum Error ◽  
Proximate Analysis ◽  
Pyrolysis Kinetics ◽  
Exponential Factor ◽  
Physiochemical Properties ◽  
Model Free ◽  
Complex Process

The present study was conducted to investigate the physicochemical properties and pyrolysis kinetics of sugarcane bagasse (SB). The physiochemical properties of SB were determined to examine its potential for pyrolysis. The physiochemical properties such as proximate analysis, ultimate analysis, heating values, lignocellulosic composition, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) of SB were investigated. The pyrolysis experiments were conducted in a nonisothermal thermogravimetric analyzer (TGA) to understand the thermal degradation behavior of SB. The activation energy (Ea) of SB pyrolysis was calculated by model-free Kissinger–Akahira–Sunose (KAS) and Ozawa–Flynn–Wall (OFW) methods. Average values of activation energy determined through KAS and OFW methods are found as 91.64 kJ/mol and 104.43 kJ/mol, respectively. Variation in the activation energy with degree of conversion was observed, which shows that pyrolysis is a complex process composed of several reactions. Coats–Redfern method was used to calculate the pre-exponential factor and reaction order. Conversion of SB due to heat treatment computed by using the kinetic parameters is found to be in good agreement with the experimental conversion data, and the maximum error limit between the experimental and predicted conversions is 8.5% for 5 °C/min, 6.0% for 10 °C/min, and 11.6% for 20 °C/min. The current investigation proves the suitability of SB as a potential feedstock for pyrolysis.

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