scholarly journals A Model for Bias Potential Effects on the Effective Langmuir Adsorption–Desorption Processes

2021 ◽  
Vol 2 (2) ◽  
pp. 125-141
Author(s):  
Luiz Roberto Evangelista ◽  
Giovanni Barbero ◽  
Anca Luiza Alexe-Ionescu
Keyword(s):  
Electrical Response ◽  
Electrolytic Cell ◽  
Balance Equations ◽  
Adsorption Phenomenon ◽  
Langmuir Adsorption ◽  
Bias Potential ◽  
Effective Coefficients ◽  
Current Densities ◽  
Phenomenological Coefficients ◽  
Adsorption Desorption

We discuss the foundations of a model based on an extension of the Langmuir approximation for the adsorption–desorption phenomena, in which the phenomenological coefficients depend on the bias potential, in addition to their dependence on the adsorption energy. The theoretical analysis focuses on the effect of these effective coefficients on the electrical response of an electrolytic cell to an external electric field, as predicted by the Poisson–Nernst–Planck model. Kinetic balance equations govern the current densities on the electrodes when the adsorption phenomenon occurs in the presence of an electric bias. The influence of the phenomenological parameters entering the model, as well as of the symmetry of the cell on the cyclic voltammetry, is investigated.

Experimental evidence for the adsorption-desorption phenomenon on the spectroscopy impedance measurements of an electrolytic cell

2007 ◽  
Vol 101 (4) ◽  
pp. 044102 ◽  
Author(s):  
G. Barbero ◽  
M. Becchi ◽  
A. Strigazzi ◽  
J. Le Digabel ◽  
A. M. Figueiredo Neto
Keyword(s):  
Experimental Evidence ◽  
Electrolytic Cell ◽  
Impedance Measurements ◽  
Adsorption Desorption

INVESTIGATION OF ADSORPTION AND INHIBITIVE EFFECT OF CALIXARENE DERIVATIVE NEWLY SYNTHESIZED TOWARDS C38 STEEL IN MOLAR HCl

2009 ◽  
Vol 16 (03) ◽  
pp. 401-406 ◽  
Author(s):  
R. SOUANE ◽  
M. KADDOURI ◽  
M. BOUKLAH ◽  
N. CHERIAA ◽  
B. HAMMOUTI ◽  
...  
Keyword(s):  
Weight Loss ◽  
Inhibition Efficiency ◽  
Langmuir Adsorption Isotherm ◽  
Enthalpy Of Adsorption ◽  
Langmuir Adsorption ◽  
Corrosion Phenomenon ◽  
Calixarene Derivative ◽  
Current Densities ◽  
C38 Steel ◽  
Mixed Type Inhibitor

The focus of this study is to synthesize a new calixarene derivative namely calix[6]arene (C21) and to test its performance as corrosion inhibitor of C38 steel in molar HCl at 308 K. Polarization and weight loss measurements were used. Weight loss tests show that C21 retards until to stop corrosion phenomenon at 5 × 10-5 M . C21 is an excellent inhibitor and its inhibition efficiency increases with its concentration to reach 100% since 5 × 10-5 M . Polarization curves revealed that C21 affects both cathodic and anodic domains by decreasing current densities and then it may be classified as a mixed type inhibitor. The calixarene tested is adsorbed on the surface according to the Langmuir adsorption isotherm. Free enthalpy of adsorption reveals that C21 acts from chemisorption onto the steel surface.

scholarly journals Modified Rate Law for Bimolecular Reactions: Applicable to Surface as well as Non-surface Reactions

2021 ◽  
Vol 37 (6) ◽  
pp. 1429-1433
Author(s):  
Gami Girishkumar Bhagavanbhai ◽  
Rawesh Kumar
Keyword(s):  
Reaction Rate ◽  
Surface Reaction ◽  
Catalyst Surface ◽  
Chemical Species ◽  
Bimolecular Reaction ◽  
Rate Equations ◽  
Bimolecular Reactions ◽  
Rate Law ◽  
Langmuir Adsorption ◽  
Adsorption Desorption

The rate equations in kinematics are expressed through basic laws under surface reaction as well as non-surface reaction. Rate law is center theme of non-surface reaction whereas Langmuir adsorption isotherms are basis of surface reaction rate expressions. A modified rate equation for bimolecular reaction is presented which considers both catalyst surface affairs as well as fraction of successful collision of different reactant for cracking and forming bonds. The modified rate law for bimolecular reaction for surface as well as non-surface reaction is stated as “Rate of a reaction is directly proportional to concentration as well as catalyst surface affair of each reactant” as r = k ΩA[A] ΩB[B] where catalyst surface affair of ith species is defined as Ωi = Ki/(1+Ki[i] + Kj[j] + …). Here, Ki is the equilibrium constant of “i” species for adsorption-desorption processes over catalyst. i, j,… indicates the different adsorbed chemical species at uniform catalyst sites and the same [i], [j], … indicates the concentration of different adsorbed chemical species at uniform catalyst sites.

scholarly journals Antibacterial Inhibitor as an Expired Metoclopramide in 0.5M Phosphoric Acid

2019 ◽  
Vol 15 (1) ◽  
pp. 71-81 ◽  
Author(s):  
Rana Afif Anaee ◽  
Majed Hameed Abd Al-Majeed ◽  
Shaimaa Alaa Naser ◽  
Mustafa M. Kathem ◽  
Omer Akram Ahmed
Keyword(s):  
Carbon Steel ◽  
Langmuir Adsorption Isotherm ◽  
Efficient Inhibitor ◽  
X Ray ◽  
Langmuir Adsorption ◽  
Carbon Steel Surface ◽  
Adsorption Desorption ◽  
Expired Drug ◽  
Mixed Type Inhibitor

Expired drug Metoclopramide was investigated as an antibacterial corrosion inhibitor for carbon steel in 0.5M H3PO4 solution using the electrochemical method at 30oC and 60oC. The results showed that this drug is an efficient inhibitor for carbon steel and the efficiency reached to 82.244 % for 175 ppm at 30oC and 76.146% for 225 ppm at 60oC. The adsorption of drug on carbon steel surface follows Langmuir adsorption isotherm with small values of adsorption-desorption constant. The polarization plots revealed that Metoclopramide acts as mixed-type inhibitor. Some parameters of inhibition process were calculated and discussed. The surface morphology of the carbon steel specimens was analyzed using scanning electron microscope and energy dispersive X-ray analysis. Antibacterial activity of inhibitor was also tested. Fourier-transform infrared (FTIR) spectroscopy confirmed the inhibitive role of Metoclopramide drug.

scholarly journals Electrochemical Production of Bismuth in the KCl–PbCl2 Melt

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5653
Author(s):  
Pavel Alexandrovich Arkhipov ◽  
Yury Pavlovich Zaikov ◽  
Yuliya Rinatovna Khalimullina ◽  
Stepan Pavlovich Arkhipov
Keyword(s):  
Lead Concentration ◽  
Porous Ceramic ◽  
Electrolytic Cell ◽  
Anode Current ◽  
Metallic Lead ◽  
Anode Dissolution ◽  
Current Densities ◽  
Electrochemical Production ◽  
Pure Bismuth ◽  
Limiting Diffusion Current

An anode dissolution of binary metallic lead–bismuth alloys with different concentrations of components has been studied in the KCl–PbCl2 molten eutectic. The dissolution of lead is found to be a basic process for the alloys of Pb–Bi (59.3–40.7), Pb–Bi (32.5–67.5), Pb–Bi (7.0–93.0) compositions in the whole interval of studied anode current densities. A limiting diffusion current of lead dissolution was observed at 2 A/cm2 and 0.1 A/cm2 for the alloys of Pb–Bi (5.0–95.0) and Pb–Bi (3.0–97.0) compositions, respectively. The dissolution of bismuth takes place at the anode current densities exceeding the mentioned values. The number of electrons participating in the electrode reactions is detected for each mechanism. Based on the theoretical analysis, the experimental electrolysis of bismuth was performed in the laboratory-scale electrolytic cell with a porous ceramic diaphragm. The final product contained pure bismuth with a lead concentration of 3.5 wt.%.

scholarly journals On the Degradation of 17-β Estradiol Using Boron Doped Diamond Electrodes

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 710 ◽  
Author(s):  
Sandra Maldonado ◽  
Manuel Rodrigo ◽  
Pablo Cañizares ◽  
Gabriela Roa ◽  
Carlos Barrera ◽  
...  
Keyword(s):  
Uric Acid ◽  
Radical Scavenger ◽  
Direct Oxidation ◽  
Diamond Electrodes ◽  
Boron Doped Diamond ◽  
Oxidation Processes ◽  
Boron Doped ◽  
17Β Estradiol ◽  
Current Densities ◽  
Adsorption Desorption

This work focuses on the evaluation of the degradation of 17β-estradiol in a mixture of synthetic urine and methanol, trying to determine in which conditions the hormone can be more easily degraded than the urine compounds. This is in the frame of an overall study in which the pre-concentration stage with adsorption/desorption technology is evaluated to improve electrolysis efficiency. Results show that this pollutant can be efficiently removed from mixtures of urine/methanol by electrolysis with diamond electrodes. This removal is simultaneous with the removal of uric acid (used as a model of natural pollutants of urine) and leads to the formation of other organic species that behave as intermediates. This opens the possibility of using a concentration strategy based on the adsorption of pollutants using granular activated carbon and their later desorption in methanol. Despite methanol being a hydroxyl radical scavenger, the electrolysis is found to be very efficient and, in the best case, current charges lower than 7 kAh·m−3 were enough to completely deplete the hormone from urine. Increases in the operation current density lead to faster but less efficient removal of the 17β-estradiol, while increases in the operation flowrate do not markedly affect the efficiency in the removal. Degradation of 17β-estradiol is favored with respect to that of uric acid at low current densities and at high flowrates. In those conditions, direct oxidation processes on the surface of the anode are encouraged. This means that these direct processes can have a higher influence on the degradability of the hazardous species and opens the possibility for the development of selective oxidation processes, with a great economic impact on the degradation of the hazardousness of hospitalary wastewater.

Effect of Polarization Rate in Potentiokinetic Anodic Polarization of iron in 1N H2SO4

CORROSION ◽  
1970 ◽  
Vol 26 (4) ◽  
pp. 141-150 ◽  
Author(s):  
J. E. REINOEHL ◽  
F. H. BECK ◽  
M. G. FONTANA
Keyword(s):  
Anodic Polarization ◽  
Rate Sensitivity ◽  
Anodic Polarization Curve ◽  
Langmuir Adsorption ◽  
Polarization Rate ◽  
Dilute Sulfuric Acid ◽  
Current Densities ◽  
Physical Variables ◽  
Passive Current ◽  
Logarithmic Variation

Abstract Potentiokinetic data are reported for single crystal and polycrystalline specimens of high purity (56 ppm total impurities) and sulfurized (150 ppm sulfur) iron in 1N H2SO4. Eight polarization rates, ranging from 20 to 1100 mV/min, were investigated. The shape and position of potentiokinetic anodic polarization curves were found to vary appreciably and reproducibly with polarization rate. The observed logarithmic variation of three characteristic passive and transpassive current densities (ix) with polarization rate (η̇) can be expressed by a relation of the form where k and r are constants. The exponent r is given the name “polarization-rate-sensitivity.” At faster polarization rates, current densities tended to be higher and secondary passivity more pronounced. Secondary passivity merged with ordinary passivity at a material-dependent “critical” polarization rate, at which passive current densities were nearly independent of potential. Passive current densities increased with increasing potential at faster polarization rates, corresponding to Langmuir adsorption conditions, and decreased with increasing potential at slower polarization rates, corresponding to Temkin adsorption conditions. The presence and absence of sulfur and of grain boundaries had a negligible quantitative effect on the appearance of the potentiokinetic anodic polarization curve of iron in dilute sulfuric acid solution. However, a small effect of these chemical and physical variables could be expressed by different relations between currents and polarization rate.

scholarly journals Poly(amidoamine) dendrimer modified superparamagnetic nanoparticles as an efficient adsorbent for Cr(VI) removal: Effect of high-generation dendrimer on adsorption performance

2021 ◽  
Author(s):  
Can Cui ◽  
Yadian Xie ◽  
Jiaojiao Niu ◽  
Hailiang Hu ◽  
Sen Lin
Keyword(s):  
Adsorption Capacity ◽  
Pamam Dendrimer ◽  
Superparamagnetic Nanoparticles ◽  
Batch Adsorption ◽  
Adsorption Model ◽  
Langmuir Adsorption ◽  
Pseudo Second Order ◽  
Modified Adsorbents ◽  
Adsorption Desorption ◽  
Efficient Adsorbent

Abstract Heavy metal ions pollution is one of the most dangerous and critical threats to human health and environment. In this work, three different generations of PAMAM dendrimer decorated on magnetic Fe 3 O 4 composites (Fe 3 O 4 @SiO 2 –G1, Fe 3 O 4 @SiO 2 –G3, Fe 3 O 4 @SiO 2 –G5) were fabricated and characterized by FTIR, XRD, TEM, and TGA. The obtained composites were used for Cr(VI) removal. Batch adsorption studies showed that the adsorption reached equilibrium within 60 min, and the optimal pH was 3.0. The result of adsorption kinetics was simulated by the pseudo–second-order model. The adsorption equilibrium isotherm was well fitted with the Langmuir adsorption model. Furthermore, thermodynamics calculations revealed that the adsorption process was endothermic and spontaneous. Importantly, adsorption capacity of Cr(VI) obey the sequence of Fe 3 O 4 @SiO 2 –G1＜Fe 3 O 4 @SiO 2 –G5＜Fe 3 O 4 @SiO 2 –G3, 3 generation of PAMAM (3G) is the optimal for adsorption capacity of Cr(VI). The maximum theoretical Cr(VI) adsorption capacity ( q m ) of Fe 3 O 4 @SiO 2 –G3 was 334.45 mg/g, and removal ration remained above 89.5% after five cycles of adsorption–desorption. Thus, Fe 3 O 4 @SiO 2 –G3 is predicted to be an efficient adsorbent for the adsorption of Cr(VI) from aqueous solution, and the obtained results can help in the generation optimization during fabrication of dendrimer modified adsorbents.

Comparative study on the supercapacitive properties of PANI nanofibers, nanotubes, and nanospheres

2019 ◽  
Vol 32 (5) ◽  
pp. 600-608 ◽  
Author(s):  
Shanxin Xiong ◽  
Yong Zhang ◽  
Yuyun Wang ◽  
Bohua Wu ◽  
Jia Chu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Interfacial Polymerization ◽  
Electrochemical Impedance ◽  
Rate Capability ◽  
Electrochemical Performances ◽  
Synthesis Methods ◽  
Chemical Structures ◽  
Transmission Electron ◽  
Current Densities ◽  
Adsorption Desorption

In this study, polyaniline (PANI) nanostructures with different morphologies (nanofibers, nanotubes, and nanospheres) were obtained via interfacial polymerization, rapid mixing reaction, and hydrothermal method. The influences of the synthesis methods on the morphologies and supercapacitive properties of PANI nanostructures were investigated. The chemical structures of materials were characterized by Fourier-transform infrared and Raman spectroscopies. Scanning electron microscopy and transmission electron microscopy images were used to explore the morphologies of PANI nanostructures. N2 adsorption–desorption isotherm, cyclic voltammetry, charge–discharge test, and electrochemical impedance spectroscopy were used to characterize the pore distribution, electrochemical, and supercapacitive properties of PANI nanostructures. The results show that PANI nanotubes (PANI-T) exhibit the best electrochemical performances among three kinds of PANI nanostructures. The PANI-T exhibits high specific capacitances of 648 and 290 F g−1 at current densities of 0.5 and 10 A g−1, respectively, indicating its good supercapacitive property and rate capability. The enhanced electrochemical and supercapacitive performances can be attributed to its hollow nanotube structure.

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