Influence of current density on oxygen transfer in an electroflotation cell

Abstract

The objective of this work is to study the transfer of oxygen from gas to liquid phase in an electroflotation cell. The measurements were performed in a laboratory scale cell using insoluble electrodes, titanium coated with ruthenium oxide as anode and stainless steel as cathode. The volumetric mass transfer coefficient K L a, was characterized for clean tap water as liquid phase for different values of current density (J). The global coefficient of mass transfer based on the liquid film, K L , and the specific interfacial area, a, were characterized. A model which relates K L a to current density was established. Different evaluation criteria of oxygen transfer in electroflotation process were determined and compared with other aeration process.Keywords Current density Á Electroflotation Á Oxygen transfer Nomenclature a specific interfacial area (m 2 m -3 ) A gas-liquid interface area (m 2 ) C oxygen concentration in the liquid (g m -3 ) C * oxygen equilibrium concentration in the liquid (g m -3 ) C 0 initial dissolved oxygen concentration (g m -3 ) J current density (A m -2 ) d B bubble diameter (lm) F Faraday constant (C mol -1 ) H S static height of the liquid bed (m) H T total height of the gas -liquid bed (m) K L global coefficient of mass transfer based on liquid film (m s -1 ) K L a volumetric mass transfer coefficient (s -1 ) m O 2 oxygen flow rate (g s -1 ) M O 2 oxygen molar mass (g mol -1 ) OC oxygenation capacity (g m -3 h -1 ) RO oxygenation efficiency (%) S surface of the electrodes (m 2 ) T temperature of the liquid phase (°C) V aerated liquid volume (m 3 )Greek symbols e g gas hold-up (%) h empirical coefficient in Eq. (7)

Ultrafine Kaolinite Removal in Recycled Water from the Overflow of Thickener Using Electroflotation: A Novel Application of Saline Water Splitting in Mineral Processing

“…Ti electrodes play a fundamental role in the removal of kaolinite. The generated bubbles and flocs are created according to electrochemical reactions shown in Equations ( 3)-( 6) [53][54][55][56][57]. The microbubbles of H2 and O2 generated on the surface of the Ti electrodes in contact with a saline electrolyte during the EF process proceed via specific mechanisms of H2 evolution reaction (HER) and O2 evolution reaction (OER) in Equations ( 3) and (5), For NaCl electrolytes, the high R MF values observed at runs with 20 V/SHE and 20 min indicates large amounts of Ti flocs that were efficiently removed.…”

The effect of temperature on the efficiency of wastewater treatment by electroflotation process supplied by solar energy

“…Chen [7] found a proportionality term between the current density and the mass of the formed bubbles. In this same context, other researches [8][9][10][11] related the bubble behavior and the hydrodynamic regime with the separation efficiency. In fact, it was proved that the high separation efficiency could only be obtained in bubbly laminar regime [12].…”