ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Technological condition optimization and kinetic study on the electrochemical soluble manganese(III) production in H₂SO₄

Jinfang Chen, Sihao Liu, and Yan Wang

Wuhan Institute of Technology, Wuhan, People’s Republic of China

E-mail: wylzrfd@163.com

Abstract: Soluble trivalent manganese solution can be used as an electrolyte for manganese redox flow battery (MRFB), due to its low cost, environmental friendliness and multiple states of charge. However, poor stability of soluble trivalent manganese solution and low trivalent manganese concentration are the disadvantages of electrolyte. To optimize the stability and conductivity of soluble trivalent manganese solution, the sulfuric acid concentration, one of the major influence factors, should be firstly improved. Two-compartment cell electrolysis technology was successfully used in this work. Moreover, to improve the concentration of Mn³⁺, some key factors, such as the concentration of MnSO₄, current density, electrolysis time and temperature, should be further adjusted. The results demonstrated that the concentration of this produced trivalent manganese (≧ 0.3 M in 6 M H₂SO₄;≧ 0.4 M in 5 M H₂SO₄;≧ 0.5 M in 4 M H₂SO₄) is much higher than that have been reported. Solid product of manganese(III) sulfate was also firstly prepared. For the formation of soluble trivalent manganese, the 5 mol/L H₂SO₄ is the optimal acidity and 10.9 mA/cm² is the best current density at 273 K for 3 h. Some electrochemical kinetics parameters had also been calculated (electrolyte is 5 M H₂SO₄ and 0.4 M MnSO₄), e.g., diffusion coefficient of Mn²⁺ is 5.3057 × 10⁻⁶ cm²/s, transfer coefficient of electrode reaction is 0.3782, and exchange current density is 1.5662 × 10⁻⁴ A/cm². The CV results demonstrated that the redox process of Mn(III)/Mn(II) is the quasi-reversible process.

Keywords: Electrochemical synthesis ; Anodic oxidation ; Manganese(III) ; Kinetic study 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-018-0633-1

Chemical Papers 73 (4) 821–831 (2019)