Coulometric and Chronoamperometric Studies on Bisulfite Reduction at a Surfactant/Myoglobin Film on Glassy Carbon Electrode
Abdelatty Mohamed Radalla
Issue:
Volume 10, Issue 2, March 2022
Pages:
18-22
Received:
16 November 2021
Accepted:
3 December 2021
Published:
23 March 2022
Abstract: Background. The redox-active protein, myoglobin (Mb), exchanges electrons very slowly with bare electrodes. Just like on a highly oriented pyrolytic graphite (HOPG) bare electrode, electron transfer between myoglobin (Mb) and a bare glassy carbon (GC) electrode was not observed. The myoglobin (Mb) in di-dodecyl dimethyl ammonium bromide (DDAB) film immobilized on glassy carbon electrode surface had a good charge transport, allowing Mb to be used as a redox catalyst for multi-electron transfer reactions. Objective. We report here the myoglobin on a glassy carbon (GC) electrode as a catalyst for the multi-electron reduction of bisulfite in aqueous buffered solutions. Methods. Coulometry and chronoamperometry are used as tools to probe the Mb/DDAB film on GC electrode as an effective electro-catalyst for the multi-electron reduction of bisulfite. Results. Variation in current with time of bisulfite reduction followed first-order reaction kinetics. The heterogeneous electron transfer rate constant of the film and catalytic rate constant for the reduction of bisulfite were determined. Conclusion. The study confirmed that bisulfite was the reactive species and the catalytic reduction reaction at Mb/DDAB film followed the EC’ catalytic mechanism.
Abstract: Background. The redox-active protein, myoglobin (Mb), exchanges electrons very slowly with bare electrodes. Just like on a highly oriented pyrolytic graphite (HOPG) bare electrode, electron transfer between myoglobin (Mb) and a bare glassy carbon (GC) electrode was not observed. The myoglobin (Mb) in di-dodecyl dimethyl ammonium bromide (DDAB) film...
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Complexation Equilibria and Determination of Stability Constants of Some Divalent Metal Ion Complexes of L-Cysteine and Diphenylamine in Aqueous Media
Abdelatty Mohamed Radalla
Issue:
Volume 10, Issue 2, March 2022
Pages:
23-31
Received:
17 November 2021
Accepted:
2 December 2021
Published:
29 March 2022
Abstract: Background. Metal complexes of biologically active ligands had considerable interests. L-cysteinate residue, L-Cys, is a biologically abundant and important versatile binding site of proteins. Diphenylamine, DPA, is an important aromatic amine containing two phenyl groups. Complexation equilibria of the divalent metal ions, Ca2+ and Zn2+ with the bio- relevant α-amino acid, L-cysteine and the nitrogen-containing diphenylamine ligand were investigated by means of the potentiometric technique at 25.0 ± 0.1°C and constant ionic strength of 0.200 ± 0.001 mol·dm-3 NaNO3. Objective. The stability constants and standard free energy changes of the α-amino acid, L-cysteine and diphenylamine complex species were determined at 0.200 ± 0.001 mol·dm-3ionic strength. Methods. The formation of the different 1:1 and 1:2 binary complexes and 1:1:1 ternary complexes were inferred from the potentiometric titrations. Results. The concentration distribution of L-cysteine species formed in solution was evaluated. The dissociation constants of the α-amino acid and diphenylamine were determined at different ionic strength. The stability constants of these binary and ternary systems were calculated. The values of ∆ log10 K, percent relative stabilization, %R.S. and log10 X for the ternary systems were evaluated and discussed. Concussion. The ternary complex formation occurred in a stepwise manner with L-cysteine acting as the primary ligand. The obtained values of ∆ G0 indicated that Complex formation reactions are spontaneous. Also, for all systems studied, the ternary complexes formed are more thermodynamically stable than the binary complexes.
Abstract: Background. Metal complexes of biologically active ligands had considerable interests. L-cysteinate residue, L-Cys, is a biologically abundant and important versatile binding site of proteins. Diphenylamine, DPA, is an important aromatic amine containing two phenyl groups. Complexation equilibria of the divalent metal ions, Ca2+ and Zn2+ with the b...
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Regeneration and Reclamation of Mono-Ethylene Glycol (MEG) Used as a Hydrate Inhibitor: A Review
Edith Anwunli Odeigah,
Thunyaluk Pojtanabuntoeng
Issue:
Volume 10, Issue 2, March 2022
Pages:
32-45
Received:
13 March 2022
Accepted:
31 March 2022
Published:
14 April 2022
Abstract: The use of Mono-Ethylene Glycol (MEG) as a hydrate inhibitor in wet gas pipelines is increasingly becoming widespread, especially in deep-water long-tie back pipelines where the use of low dosage hydrate inhibitor (LDHI) is not practical. MEG is a commonly used thermodynamic hydrate inhibitor (THI), and it prevents hydrate formation by lowering hydrate formation temperature. One significant advantage of MEG over other THIs is that MEG can be regenerated and reused, which minimises the cost of chemicals as large volumes of THIs are usually required. Over the years, significant research advances have been made in MEG recovery and the MEG Recovery Unit (MRU) design. This paper presents a comprehensive review of the evolution of MEG regeneration systems over the years and introduces recent developments, particularly on energy conservation. The entire MEG recycle and regeneration process is reviewed as well as the various sections and their functions. The different MRU configuration are discussed and factors that affect the performance of the MRU as well as Corrosion and corrosion mitigation in the MRU. This review shows that there are a number of new improvements in the MRU application that are yet to be fully explored as well as some technical challenges that are yet to be fully understood.
Abstract: The use of Mono-Ethylene Glycol (MEG) as a hydrate inhibitor in wet gas pipelines is increasingly becoming widespread, especially in deep-water long-tie back pipelines where the use of low dosage hydrate inhibitor (LDHI) is not practical. MEG is a commonly used thermodynamic hydrate inhibitor (THI), and it prevents hydrate formation by lowering hyd...
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