Mass Transport and Potential Studies in a Flow-through Porous Electrode Reactor

Abstract

This paper deals with the use of reticulated vitreous carbon (RVC) and graphite felt (GF) as porous electrode for the removal of 20 ppm Cu(II) in 0.5 mol dm -3 Na 2 SO 4 at pH 2 (which resembles a rinsing wastewater generated by a plating industry). The experimental mass transport characterization (k m a = bu c ) showed that for 100 ppi (RVC), the value of the coefficient b, associated with magnitude of porous electrode, is 0.88, while for (GF) is 3.38. On the other hand, c value for 100 ppi (RVC) is 0.06, while for (GF) is 0.62, indicating that the flow pattern is a complex function of the shape of the electrode. The experimental potential drop for 100 ppi (RVC) and (GF) (1.2 cm thick), indicated the absence of hydrogen evolution. Current efficiencies for RVC and GF were function of convection, giving values comprised between 45 ≤ φ ≤ 68% and 51 ≤ φ ≤ 73%, respectively, and energy consumption values of 0.3 < E cons < 1.7 and 0.4 < E c < 1.1 kWh m -3 , respectively. Theoretical number of identical cells in the stack (N) necessary to the cupric depletion from 20 to 1 ppm, for 100 ppi (RVC) and (GF) were calculated.

Determination of the mass-transport properties of vanadium ions through the porous electrodes of vanadium redox flow batteries

“…Another way is to electrochemically determine the mass-transfer coefficient by measuring the limiting current densities when the electrode operates under mass-transport control. [32][33][34][35] Nevertheless, as the porous electrode usually has a finite thickness (several millimeters), this approach can only be used to obtain the average masstransfer coefficient over the electrode surface.…”

The Influence of Galena Galvanic Interaction on the Reactivity of Chalcopyrite Flotation Concentrate

“…This is consistent with the analysis obtained by ASV in that no copper ions were detected in solution (Figure 3Ia). According to previous studies (1,7), this behavior indicates the presence of a passive non stoichiometric polysulfide (Cu 1-r Fe 1-s S 2-t ). On the other hand, the modified surface of the CPE-CC (Figure 4b) shows a reversible a1/b1 behavior , characteristic of the redox of an active non stoichiometric polysulfide Cu 1-x Fe 1-y S 2-z , (equation [1]) (7): Cu 1-x Fe 1-y S 2-z + 2bH + + 2(b-a)e -⇔ Cu 1-x Fe 1-y-a S 2-z-b + aFe 2+ + bH 2 S [1] In previous studies with pure chalcopyrite (7), it was proposed that the electrochemical oxidation, at low potentials, occurs in two stages: firstly, the formation of the passive non stoichiometric polysulfide and after, at higher potentials, this is Table I).…”

“…The voltammograms obtained for the carbon paste-pure chalcopyrite (CPE-CP, Figure 1a) and the carbon paste-chalcopyrite concentrate (CPE-CC, Figure 1b) show oxidation and reduction peaks that for the most part correspond to chalcopyrite [1,7,8], such as the pre-peak A1 (very small for the CPE-CP, Figure 1a), followed by an increase in the current, which corresponds to the complete oxidation of chalcopyrite, equation [1.4] Table I (7,8). The peaks C1, C2, C3 and C4 correspond to the reduction of the products formed during the oxidation of chalcopyrite, while in peaks A2, A3 and A4 oxidation processes occur, which are related with chalcocite (Cu 2 S), formed by the reduction of chalcopyrite (7)(8)(9).…”

“…The peaks C1, C2, C3 and C4 correspond to the reduction of the products formed during the oxidation of chalcopyrite, while in peaks A2, A3 and A4 oxidation processes occur, which are related with chalcocite (Cu 2 S), formed by the reduction of chalcopyrite (7)(8)(9). Additionally, the voltammogram that corresponds to the concentrate shows very particularly the formation of an anodic peak, pa1 (Figure 1b inset) related to the oxidation of metallic lead originating from the reduction of galena, PbS (10).…”

Rates of H2O2 electrogeneration by reduction of anodic O2 at RVC foam cathodes in batch and flow-through cells

“…Carbonaceous materials such as graphite [26,27], graphite felt [28], reticulated vitreous carbon (RVC) foam [29,30], activated carbon fiber (ACF) [31], and carbon sponge [32] are the most commonly used cathode materials for H 2 O 2 production via 2 electron O 2 reduction. However, there are limited studies on the application of direct H 2 O 2 electrogeneration in a flow-through cell.…”