Improving the Treatment Efficiency and Lowering the Operating Costs of Electrochemical Advanced Oxidation Processes

Abstract

Electrochemical advanced oxidation processes (EAOP®) are promising technologies for the decentralized treatment of water and will be important elements in achieving a circular economy. To overcome the drawback of the high operational expenses of EAOP® systems, two novel reactors based on a next-generation boron-doped diamond (BDD) anode and a stainless steel cathode or a hydrogen-peroxide-generating gas diffusion electrode (GDE) are presented. This reactor design ensures the long-term stability of BDD anodes. The application potential of the novel reactors is evaluated with artificial wastewater containing phenol (COD of 2000 mg L−1); the reactors are compared to each other and to ozone and peroxone systems. The investigations show that the BDD anode can be optimized for a service life of up to 18 years, reducing the costs for EAOP® significantly. The process comparison shows a degradation efficiency for the BDD–GDE system of up to 135% in comparison to the BDD–stainless steel electrode combination, showing only 75%, 14%, and 8% of the energy consumption of the BDD–stainless steel, ozonation, and peroxonation systems, respectively. Treatment efficiencies of nearly 100% are achieved with both novel electrolysis reactors. Due to the current density adaptation and the GDE integration, which result in energy savings as well as the improvements that significantly extend the lifetime of the BDD electrode, less resources and raw materials are consumed for the power generation and electrode manufacturing processes.

Electrooxidation of Phenol on Boron-doped Diamond and Mixed-metal Oxide Anodes: Process Evaluation, Transformation By-products, and Ecotoxicity

“…In the study by Santos et al, 20 the same efficiency was reached (99.9%), but in the presence of 20 g l −1 NaCl and EC was 7.33 kWh kg phenol −1 . Similar result was achieved in a study by Muddemann et al 4 where EC was 103.02 kWh kg −1 with almost complete mineralization (>99% COD), using BDD anode and SS cathode, but with 9 g l −1 Na 2 SO 4 . Some studies have shown very high energy consumption as, for example, in the case of treatment of phenolic wastewaters from cashew-nut processing industry with BDD anode by applying 20 mA cm −2 .…”

“…Similarly, Oliveira et al 19 showed high efficiency of Ti/RuO 2 -TiO 2 anode. However, BDD anode might have other advantages such as lifespan of up to 18 years, significantly reducing the cost of EO, as claimed by Muddemann et al 4 Energy consumption.-The lowest energy consumption (EC) was recorded in electrolyte NaCl, and was 116.6 kWh kg phenol −1 at E f 99.9% (Fig. 4).…”

“…Electrochemical oxidation (EO) is important as one of the more eco-friendy AOPs. 4,5 EO is used for removal of pollutants from wastewaters because of its significant advantages: it is based on the in situ production of the hydroxyl radical. 6 The most important parameter affecting mechanism of EO is the anode material [7][8][9] which can be active (i.e.…”

Combining α-Al2O3 Packing Material and a ZnO Nanocatalyst in an Ozonized Bubble Column Reactor to Increase the Phenol Degradation from Wastewater

“…BCRs are one of the most applied gas-liquid and gas-liquid-solid multiphase reactors in industrial processes. They are characterized by many benefits such as easy operation, efficient mixing, high heat and mass-transfer rates, low maintenance costs, and low energy consumption [11][12][13][14][15].…”

PbO2 modified BDD electrode by dicationic ionic liquids assisted electrodeposition for efficient electrocatalytic degradation of pesticide wastewater

“…When the OEP of the anode is lower than the direct electron transfer potential of organic pollutants, the oxygen evolution reaction occurs first in the anode during the electrolysis (Rodriguez-Narvaez et al 2021). This reduces the rate of • OH generated and the current efficiency, and prolongs the electrolysis duration, resulting in higher energy consumption (Muddemann et al 2021). Therefore, the choice of anode material is extremely critical.…”