Abstract
This study aims to evaluate the ability of the graphite granules (GG) recycled from spent Zn-C batteries to act as 3D cathode for hydrogen peroxide (HP) electrosynthesis (HPE) in eco-friendly conditions (unbuffered 0.05 M Na2SO4 solution, air as O2 source). The performances of GG were compared to those of other usual carbonaceous cathode materials for HPE such as graphite bloc, graphite felt and reticulate vitreous carbon (RVC), using a divided filter-press electrochemical reactor. The operational parameters such as the polarization mode, electrolyte and air flow rates, applied potentials or imposed currents, and aeration mode were optimized by 1 h tests of electrosynthesized HP accumulation (EHPA). Considering as optimization criteria the best compromise between the final HP concentration, global current efficiency and electrical energy specific consumption, we find that the most efficient material for EHPA was RVC of 500 ppi, exploited in galvanostatic mode and using an original aeration system. In optimized conditions, for the GG cathode, very promising efficiency indicators were evaluated, suggesting that better results can be obtained by electrode geometry optimization and GG pretreatment.
Highlights
Hydrogen peroxide (HP) is an environmentally friendly reagent used in the chemical industry and environment protection
The influences of the Qel and applied W.E. potential (EW.E.) on the HP electrosynthesis (HPE) rates were evaluated for all tested cathodic materials
Because the instant HP concentration ([H2O2]t) evaluated with the flow-through hydrogen peroxide detector (FTHPD) strongly depends on the Qel, for a more relevant comparison, the recorded D.E. currents (ID.E.) were converted to instant generation rates (I.G.R.) values using the calibration data [40], the corresponding Qel values and the following equation: I .G.R
Summary
Hydrogen peroxide (HP) is an environmentally friendly reagent used in the chemical industry and environment protection. Among the EAOPs, the electro-Fenton process (EFP), based on the in-situ HP electrosynthesis (HPE) by the oxygen reduction reaction (ORR) and generation of the OH in the presence of Fe2+, represents a promising perspective for the treatment of waste waters [8]. The cathodic material essentially influences the HPE, the carbonaceous materials being preferred due to their high catalytic activity for ORR, chemical resistance and low catalytic activity for side reactions [12]. Carbonaceous materials such as graphite bloc (GB), [11, 13], graphite felt (GF) [6, 7, 11, 14], reticulated vitreous carbon (RVC) [11, 15, 16], unmodified [16] or activated [17, 18] carbon fibers, boron doped diamond [13] and glassy carbon pellets [19] were tested as cathodes for HPE. In order to increase the HPE efficiency, different physical [20-22], chemical [21, 23-26] or electrochemical [27] methods were tested to modify the surface of the raw carbonaceous materials
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