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

Ulrich Kunz,Rieke Neuber,Mohammad Issa,Dennis Haupt,Marius Enstrup,Thorsten Matthée,Michael Sievers,Fabian Bienen,Jonatan Möller,Tobias Graßl,Thorben Muddemann

doi:10.3390/pr9091482

Ulrich Kunz, Rieke Neuber + Show 9 more

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https://doi.org/10.3390/pr9091482

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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.

Highlights

Electrochemical advanced oxidation processes (EAOP® ) are promising key elements for achieving a circular economy
The electron transfer between the organic compound and the electrode occurs at the electrode surface with the direct electrochemical oxidation
The first aim of this study is to reduce the anodic diamond wear off, enabling a long boron-doped diamond (BDD)

Summary

Introduction

Electrochemical advanced oxidation processes (EAOP® ) are promising key elements for achieving a circular economy. EAOP® provide versatile, efficient, and clean methods for wastewater treatment through the use of electrons and their ability to oxidize wastewater pollutants either directly or indirectly [1]. The electron transfer between the organic compound and the electrode occurs at the electrode surface with the direct electrochemical oxidation. Indirect electrochemical oxidation involves intermediates that perform the electron exchange between the organics and the electrode in the bulk of the electrolyte [1]. “Active” and “non-active” anodes are used for oxidation, whereby “active”. Anodes with low oxygen overpotentials (OVP), e.g., dimensionally stable anodes or Pt, favor the selective oxidation of organic species and are preferred for the generation of reactive chlorine species [2,3].

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