Toward a Green Generation of Oxidant on Demand: Practical Electrosynthesis of Ammonium Persulfate

Abstract

The electrolysis of aqueous solution of ammonium sulfate has been systematically investigated in a two-compartment electrolytic flow cell for the potential applications for green and efficient synthesis of ammonium persulfate. A commercial boron-doped diamond (BDD) coated anode (active area of 10 cm 2 ) was used and electrolysis was operated under batch recirculation. Under a flow rate of 3.33 mL min −1 , the flow pattern is well described by a flow model with axial dispersion in the reaction compartment. The electrosynthesis was found not to be mass transport-limited in the present system at flow rates of ≥50 mL min −1 with a current density of ≤150 mA cm −2 . The charge transfer-controlled reaction was subsequently modeled, taking into account bubble coverage effects. Thereafter, the productivity of persulfate was investigated under different current densities, electrolyte compositions and concentrations. It was found that a high current efficiency can be obtained at the initial stage (∼93%, 150 mA cm −2 , ≤1 h), which deteriorated with time. By altering the volume and concentration of the anolyte, up to 1.31 M (150 mA cm −2 , 3 h) of oxidant solution can be delivered for ondemand applications. The hydrogen of high purity was produced as a valuable byproduct of the process.

Ambient methane functionalization initiated by electrochemical oxidation of a vanadium (V)-oxo dimer

“…2c). It further corroborates that no gaseous or liquid products other than CH 3 OSO 3 H were generated from CH 4 oxidation, and solvent oxidation into O 2 and possibly trace persulfate 29,30 is the only plausible side reaction (vide infra). The Arrhenius plot between ln(j CH4 ) and 1/T yields an apparent activation energy (E a ) as low as 10.8 ± 0.6 kcal mol −1 (Fig.…”

Experimental Study on Four Cation Exchange Membranes in Electrosynthesis of Ammonium Persulfate

“…4 shows the current efficiency of the PGN membrane, JCM-II ® membrane, Nafion ® 324 membrane and CMI-7000 ® membrane as a function of electrolyte flow rate at the cell voltage of 4.5 V, 4.5 V, 5 V and 5.5 V, respectively. The current efficiency of the PGN membrane, JCM-II ® membrane, Nafion ® 324 membrane and CMI-7000 ® membrane increased with the electrolyte flow rate increasing and reached their maximum values, 94.85%, 80.73%, 77.76% and 73.22%, respectively, at the electrolyte flow of 70 mL min -1 and there was no significant increase in the current efficiency of the four membranes at the electrolyte flow rate from 60 mL min -1 to 70 mL min -1 suggesting that the mass transfer was not the reaction rate determining step at the electrolyte flow rate between 60 mL min -1 and 70 mL min -1 in the present system apparatus [15]. Fig.…”

“…But the Nafion ® 117 membrane was not easy to install in an electrolytic cell because of its low mechanical strength without reinforced mesh. J. Zhao et al [15] improved the current efficiency to 80% using a Nafion ® 427 membrane but the energy consumption reached 2000 kWh t -1 due to the low electrolyte conductivity caused by the low reaction temperature of 15 o C. Besides, the low electrolyte temperature would reduce the solubility of ammonium persulfate, which would reduce the electrosynthesis rate of ammonium persulfate.…”

“…J. Zhu et al [15] used the Nafion 424 cation exchange membrane, with a mixture of 456 g L -1 (NH 4 ) 2 SO 4 in 196 g L -1 H 2 SO 4 as electrolytes, improved current efficiency to 93% in the electrosynthesis of ammonium persulfate at the temperature less than 15 o C, whereas the strong electrolyte acid made ammonium persulfate easy to decompose [20] and required electrolysis equipments with high corrosion resistance. With regard to the composite membrane of perfluorosulfonic acid and perfluorocarboxylic acid, the carboxylic salt layer turns into carboxylic acid layer when the pH of the anolyte is less than 2 in the electrosynthesis of ammonium persulfate, which results in serious reduction of conductive performance, the increase of the cell voltage, even blisters of the membrane and holes of the perfluorocarboxylic acid layer.…”

“…In recent years, ion exchange membranes have played a significant role in improving current efficiency and decreasing energy consumption of the electrosynthesis of ammonium persulfate [14]. The ion exchange membranes widely researched usually involve the membranes widely-used in chemical industries such as Nafion ® 424 [15][16] and Nafion ® 117 [17], newly developed membranes and other commercial ion exchange membranes [18].…”