Abstract

Electrochemical advanced oxidation processes such as electrooxidation (EO), electrooxidation with hydrogen peroxide generation (EO-H2O2) and electro-Fenton process (EF) have been investigated as alternative treatment techniques for complete removal of anionic surfactants and organic matters from real carwash wastewater. The electrochemical processes were performed with acidified real carwash wastewater using boron doped anode and carbon felt cathode. In all cases, the chemical oxygen demand (COD) removal efficiency was always increased with rise in applied current and complete organic matter decay was achieved at applied current of 500 mA or above after 6 h of electrolysis. Faster and higher COD decay was observed with EF compared to either EO or EO-H2O2 treatment, at all currents and electrolysis time. Besides, complete degradation of anionic surfactants – the major organic content of the wastewater could be achieved at all applied currents studied irrespective of the process used, indicating the efficacy of processes for total remediation of real carwash wastewater. The short-chain carboxylic acids formed as the final organic byproducts were identified and quantified by ion-exclusion chromatography. More so, lower energy consumption and higher current efficiency were achieved with EF compared to EO-H2O2. Electrochemical treatment was found to be a powerful technology for the complete abatement of organic matter in carwash wastewater for possible reuse.

Highlights

  • Electrochemical advanced oxidation processes (EAOPs) such as electrooxidation (EO) and electro-Fenton (EF) process have been widely studied for the remediation of persistent organic pollutants (POPs) from wastewater and soil (Brillas et al, 2009; Panizza and Cerisola, 2009; Rodrigo et al, 2014; Ganiyu et al, 2015; MartínezHuitle et al, 2015)

  • The elimination of organic matter in the wastewater was assessed from the decay of the chemical oxygen demand (COD), which was measured using pre-dosage HANNA®vials with 2 mL of sample

  • The decay of the anionic surfactants concentration, as the main organic constituent of the carwash wastewater, was determined during the electrochemical treatment by using a simplified spectrophotometric method based on the formation of ionic pair, anionic surfactant e methylene blue (AS-MB), following the procedure reported by Jurado et al (2006)

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Summary

Introduction

Electrochemical advanced oxidation processes (EAOPs) such as electrooxidation (EO) and electro-Fenton (EF) process have been. Widely studied for the remediation of persistent organic pollutants (POPs) from wastewater and soil (Brillas et al, 2009; Panizza and Cerisola, 2009; Rodrigo et al, 2014; Ganiyu et al, 2015; MartínezHuitle et al, 2015) These processes are highly efficient and versatile, requiring lowest amounts of chemicals or sometimes none, for producing oxidants, which make them safe and environmental friendly technologies. The influence of the type of electrochemical technology was evaluated on the elimination of the organic matter and anionic surfactants contained in a real carwash effluent obtained from one of the largest auto-wash companies in Natal (Brazil) Operation parameters such as applied current density and Fe2þ dosage and source were studied to determine the reuse viability. The data obtained were used to estimate the current efficiency and energy consumption for each of the electrochemical treatments

Chemicals
Electrolytic system
Analytical procedures
Effect of iron quantity and source on COD decay during EF
Energy consumption analysis
Evolution of short-chain carboxylic acids
Conclusions
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