Removal of Procion Red MX-5B dye from wastewater by conductive-diamond electrochemical oxidation

Abstract

In this work, the removal of Procion Red MX-5B dye by electrochemical oxidation with boron doped diamond (BDD) anodes was investigated. The impact of current density, flow rate, initial pH, and supporting electrolyte was evaluated on dye and organic matter removal. Furthermore, the use of dimensionally stable anodes (DSA) was tested to evaluate process performance. Results show that after 240 minutes, it is possible to achieve full dye and COD (chemical oxygen demand) removal, regardless of applied current density. This is due to the generation of powerful oxidantsi.e. hydroxyl radicals and peroxodisulfate-, which attack the organic matter in the wastewater, promoting its complete degradation. However, process efficiency increases when using lower current densities (10 mA cm-2): electric charges of about 5 Ah dm-3 are sufficient to fully remove both dye and COD, while charges higher than 15 Ah dm-3 are required when working at higher current densities (> 30 mA cm-2). This fact is related to the production of large amounts of hydroxyl radicals, which are wasted in other reactions at higher current densities. On the other hand, higher flow rates (300 dm 3 h-1) promote Procion Red MX-5B and organic matter degradation, due to improved mass transfer within the system. Regarding the impact of initial pH on dye removal, no significant differences were observed. Conversely, COD is clearly affected by this parameter: it is only possible to fully remove the organic matter when working at natural pH. Finally, with DSA anodes, higher dye removal efficiencies are attained than with BDD electrodes, when 100 mg dm-3 chlorides are added to the supporting electrolyte. Likewise, higher chloride concentration (100-1000 mg dm-3) was observed to enhance process efficiency when using DSA as anode material. However, during electrolysis with both BDD and DSA, chloride ions in the supporting electrolyte promote the production of 3 intermediate organochlorinated compounds. Therefore, under these conditions, no full organic matter removal can be achieved, regardless of the anode material employed.

An electrocatalytic route for transformation of biomass-derived furfural into 5-hydroxy-2(5H)-furanone

“…Meanwhile, the highest double layer capacitance (C dl ) was achieved using the CuS/CP electrode (Table S1 †), suggesting the higher charge density around CuS/CP. Both more facile electron transfer and higher charge density were benecial for the generation of hydroxyl radicals (the active species for oxidation) from H 2 O electrolysis, [22][23][24][25][26][27] and thus enhanced furfural oxidation on the CuS/CP electrode. Additionally, no obvious difference was found in solution resistance (R s ) because the electrolyte with the same composition was employed for all reactions (Table 1), implying the negligible effect of R s on the different activity of the used electrodes.…”

“…[16][17][18][19][20][21] Moreover, some active species (e.g., hydroxyl radicals) for oxidation (especially in water treatment for waste oxidation) can be generated from H 2 O via electrocatalysis. [22][23][24][25][26][27] Considering the advantages of electrocatalysis, it may be a promising route for direct oxidation of furfural to HFO using H 2 O as the oxygen source, but this has not been reported to date.…”

Improvement of the Electrochemical Behavior of (Sb, Sn, Cu)O Ceramic Electrodes as Electrochemical Advanced Oxidation Anodes

“…A wide range of alternative processes have been studied in this context. [17] This technology uses electrical energy as a vector for environmental decontamination: the organic compounds are degraded either by direct electron transfer to the anodic electrode (i. e., direct oxidation pathway), or by oxidants that have been electrochemically generated in situ (i. e., indirect oxidation pathway). [4] The efficiency of these processes for removing recalcitrant pollutants from wastewaters has been widely reported in literature for a vast variety of recalcitrant pollutants: [5] pharmaceuticals, such as Propranolol and Diatrizoate; [6][7][8] dies, like Disperse Blue 3; [9,10] pesticides and herbicides, such as tebuthiuron and glyphosate; [11,12] and industrial compounds, like phenol, bisphenol A and EDTA.…”

“…[13][14][15][16] Electrochemical advanced oxidation processes (EAOPs) are a particular type of AOPs that have gained increasing attention. [17] This technology uses electrical energy as a vector for environmental decontamination: the organic compounds are degraded either by direct electron transfer to the anodic electrode (i. e., direct oxidation pathway), or by oxidants that have been electrochemically generated in situ (i. e., indirect oxidation pathway). [18] The wide diversity of effluents that have been successfully treated with this technology shows its great efficiency and flexibility.…”

Effect of the sp3/sp2 Ratio in Boron‐Doped Diamond Electrodes on the Degradation Pathway of Aniline by Anodic Oxidation

“…Electrochemical advanced oxidation processes (EAOPs) are wellknown green technologies that have been widely used in the last few years, [1][2][3][4] as they are able to eliminate pollutants of emerging concern and persistent pollutants, such as drugs, [5][6] pesticides or fungicides, [7][8] dyes, [9][10] as well as other organic compounds resistant to photo and biodegradation from aqueous matrices. [11][12] Anodic oxidation (AO) [13][14][15] is one of the most popular processes among EAOPs.…”