scholarly journals Combination of Thermal, Hydrometallurgical and Electrochemical Tannery Waste Treatment for Cr(III) Recovery

2021 ◽  
Vol 11 (2) ◽  
pp. 532
Author(s):  
Evgenios Kokkinos ◽  
Aggeliki Banti ◽  
Ioanna Mintsouli ◽  
Aikaterini Touni ◽  
Sotiris Sotiropoulos ◽  
...  
Keyword(s):  
Extraction Efficiency ◽  
Waste Treatment ◽  
Constant Current ◽  
Vitreous Carbon ◽  
Applied Potential ◽  
Disc Electrode ◽  
Rotating Disc ◽  
Reduction Efficiency ◽  
Scale Reactor ◽  
Initial Conversion

A combination of thermal (500–750 °C in air) and hydrometallurgical (acidic) treatments have been applied to dried tannery sludge, resulting in the initial conversion of Cr(III) to Cr(VI) and its subsequent leaching as wastewater with high Cr(VI) concentration content (3000–6000 mg/L), presenting an extraction efficiency over 90%. The optimal electrochemical conditions for the subsequent Cr(VI) reduction with respect to acid concentration and acid kind were established by applying appropriate rotating disc electrode (RDE) experiments, using a glassy carbon (GC) electrode, and found to be equal or higher than 0.5 M H2SO4 (for the respective Cr(III) concentration range studied). The result from leaching Cr(VI) wastewater was further treated in small electrochemical bench-scale reactor for its conversion back to Cr(III) form, potentially reusable in the tanning industry. Ti-based anodes and a reticulated vitreous carbon (RVC) cathode were used to treat small (350–800 mL) samples in batch, as well as in batch-recirculation prototype electrochemical reactors, under the application of constant current or appropriately applied potential to achieve Cr(VI) conversion/reduction efficiency over 95%.

Bromate Reaction on a Rotating Disc Electrode: A New Method of Obtaining Approximate Analytical Solutions for Stationary Regime

2018 ◽  
Vol 483 (1) ◽  
pp. 256-260
Author(s):  
M. A. Vorotyntsev ◽  
A. E. Antipov ◽  
M. M. Petrov ◽  
R. D. Pichugov ◽  
E. I. Borisevich ◽  
...  
Keyword(s):  
Analytical Solutions ◽  
Stationary Regime ◽  
New Method ◽  
Rotating Disc Electrode ◽  
Disc Electrode ◽  
Rotating Disc ◽  
Approximate Analytical Solutions

scholarly journals Redox Property Tuning in Bipyridinium Salts

2021 ◽  
Vol 8 ◽  
Author(s):  
Zuzana Burešová ◽  
Milan Klikar ◽  
Petr Mazúr ◽  
Michaela Mikešová ◽  
Jaroslav Kvíčala ◽  
...  
Keyword(s):  
Redox Processes ◽  
Rotating Disc Electrode ◽  
Structure Property ◽  
Disc Electrode ◽  
Rotating Disc ◽  
Half Cell ◽  
Redox Flow Batteries ◽  
Structure Property Relationships ◽  
Reversible Redox ◽  
Small Capacity

Bipyridinium salts are currently very popular due to their perspective applications in redox flow batteries. Hence, we designed and prepared a series of bipyridiniums based on 2,2′-, 3,3′-, and 4,4′-bipyridine and 2,2′-bipyrimidine. The straightforward synthesis utilizes commercially or readily available starting compounds and their direct N-alkylation, mostly using 1,3-propanesultone. All eleven target derivatives with systematically evolved structure were investigated by cyclic voltammetry, which allowed elucidating thorough structure-property relationships. The electrochemical behavior depends primarily on the parent scaffold, type of N-alkylation, number of quaternized nitrogen atoms, planarity, counter ion as well as the used media. Two derivatives featuring quasi-reversible redox processes were further tested on rotating disc electrode and in a flow battery half-cell. 4,4′-Bipyridinium derivative bearing two sultone residues showed better performance and stability in the flow half-cell with small capacity decays of 0.09/0.15% per reduction-oxidation cycle, based on the number of the utilized redox processes (one/two).

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