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6CCVD Research

Comparison of homogeneous and heterogeneous electrochemical advanced oxidation processes for treatment of textile industry wastewater

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2022-06-09
JournalJournal of Hazardous Materials
AuthorsSié Alain Hien, Clément Trellu, Nihal Oturan, Alain Stéphane Assémian, Bi Gouessé Henri Briton
InstitutionsInstitut National Polytechnique Félix Houphouët-Boigny, Université Gustave Eiffel
Citations52
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This study compares homogeneous (Electro-Fenton, EF) and heterogeneous (Anodic Oxidation, AO) Electrochemical Advanced Oxidation Processes (EAOPs) for the mineralization of real, highly alkaline textile wastewater.

  • Superior Mineralization: The combined EF/BDD process achieved the highest Total Organic Carbon (TOC) removal (95% in 6 hours), benefiting from both bulk (homogeneous) and surface (heterogeneous) generation of hydroxyl radicals (‱OH).
  • Kinetic Behavior: AO/BDD followed pseudo-zero order kinetics, indicating the process was limited by current supply relative to the high organic load. EF processes followed pseudo-first order kinetics, dependent on organic concentration.
  • Energy Efficiency (EC): EF/BDD demonstrated lower energy consumption (EC) compared to AO/BDD (e.g., 55 vs 90 kWh (kgTOC)-1 after 4 hours at 200 mA), highlighting the benefit of bulk oxidant generation.
  • pH Flexibility: AO/BDD was highly effective at the effluent’s natural, highly alkaline pH (13.4), eliminating the significant cost associated with pH adjustment required for conventional EF (pH 3).
  • By-product Control: A critical drawback of using the non-active BDD anode in chloride-rich water was the high formation of toxic chlorate (ClO3-) and perchlorate (ClO4-).
  • Mitigation Strategy: Using an active anode (Pt) in the EF/Pt configuration strongly suppressed ClO3-/ClO4- formation, maintaining concentrations below 0.5% of the initial chloride load at low current density.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Initial pH (Raw Effluent)13.40-Highly alkaline
Initial TOC0.45g/LOrganic load
Initial COD1.10gO2/LOrganic load
Initial Chloride [Cl-]0.44g/LHigh salinity
Conductivity9.31mS/cmSuitable for electrochemical treatment
Anode Material (AO)BDD on Nb6 x 4 cm2Non-active electrode
Cathode Material (EF)Carbon Felt16 x 5 cm2For H2O2 generation
Current Density (Low)8.3mA cm-2200 mA operation
Current Density (High)21mA cm-2500 mA operation
Max TOC Removal (6 h)95%EF/BDD process
AO/BDD Mineralization KineticPseudo-zero order-k0 = 50 mg L-1 h-1
EF/BDD Mineralization KineticPseudo-first order-k1 = 0.38 h-1
EC (EF/BDD, 4 h, 200 mA)55kWh (kgTOC)-1Energy consumption per TOC removed
EC (AO/BDD, 4 h, 200 mA)90kWh (kgTOC)-1Energy consumption per TOC removed
ClO4- Formation (EF/Pt, 200 mA)Below detection limit-Strong suppression of toxic by-products

Key Methodologies

Section titled “Key Methodologies”

The study utilized an undivided cylindrical open batch reactor (230 mL) to compare three electrochemical configurations under galvanostatic control.

  1. Anode Materials: Boron-Doped Diamond (BDD) thin film on Niobium (Nb) was used as the non-active anode for Anodic Oxidation (AO/BDD) and hybrid Electro-Fenton (EF/BDD). Platinum (Pt) was used as the active anode for comparison (EF/Pt).
  2. Cathode Materials: Stainless steel (AISI 304) was used as the cathode for AO/BDD. Carbon felt was used as the cathode for EF processes to facilitate the two-electron reduction of dissolved O2 to generate H2O2.
  3. Electro-Fenton Conditions: EF experiments required the initial pH to be adjusted to 3.0 (using sulfuric acid) to maintain the iron catalyst (0.1 mM FeSO4‱7H2O) in solution and optimize Fenton’s reaction. Air was continuously bubbled into the solution.
  4. Anodic Oxidation Conditions: AO/BDD experiments were successfully performed at the effluent’s natural, highly alkaline pH (13.4), demonstrating operational flexibility.
  5. Kinetic Analysis: Mineralization kinetics were determined by monitoring TOC removal over 6 hours. Discoloration kinetics were monitored via UV-vis absorbance at 668 nm (the maximum absorbance wavelength for the main dye, Bezathren Dark Blue).
  6. By-product Monitoring: Ion Chromatography was employed to quantify the formation of toxic inorganic chlorinated species (ClO3- and ClO4-) resulting from the oxidation of the high concentration of initial chloride ions.

Commercial Applications

Section titled “Commercial Applications”

The findings provide critical engineering insights for the design and implementation of Advanced Oxidation Processes (AOPs) in industrial settings, particularly those dealing with complex, high-salinity effluents.

  • Textile and Dye Wastewater Treatment: Direct application for treating highly colored, high-TOC, and high-pH effluents, offering a non-selective mineralization route where biological methods fail.
  • BDD Electrode System Design: Validates the use of BDD anodes in hybrid EF/BDD systems to achieve high mineralization rates and energy efficiency, crucial for commercial viability.
  • Process Selection for Chloride Streams: Provides a trade-off analysis:
    • AO/BDD: Preferred when pH adjustment costs are prohibitive (high pH effluent).
    • EF/Pt: Preferred when minimizing the formation of toxic perchlorate (ClO4-) in chloride-rich water is paramount.
  • Refractory Industrial Effluents: Applicable to other complex industrial wastewaters (e.g., pharmaceutical, landfill leachate) requiring complete mineralization of recalcitrant organic compounds.
  • Future EAOP Development: Highlights the need for developing new electrode materials (like modified active anodes or heterogeneous EF catalysts) that function effectively across a wider pH range while suppressing toxic inorganic by-product formation.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2010 - Laboratory and pilot plant scale study on the electrochemical oxidation of landfill leachate [Crossref]
  2. 2016 - An integrated (electro- and bio-oxidation) approach for remediation of industrial wastewater containing azo-dyes: understanding the degradation mechanism and toxicity assessment [Crossref]
  3. 2018 - In-situ generation of effective coagulant to treat textile bio-refractory wastewater: optimization through response surface methodology [Crossref]
  4. 2017 - Kinetics of oxidative degradation/mineralization pathways of the antibiotic tetracycline by the novel heterogeneous electro-Fenton process with solid catalyst chalcopyrite [Crossref]
  5. 2006 - Decolorizing dye wastewater from the agate industry with Fenton oxidation process [Crossref]
  6. 2008 - An overview of the application of Fenton oxidation to industrial wastewaters treatment [Crossref]
  7. 2017 - Adsorption of Bezathren dyes onto sodic bentonite from aqueous solutions [Crossref]
  8. 2009 - The occurrence of perchlorate during drinking water electrolysis using BDD anodes [Crossref]
  9. 2015 - Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods. an updated review [Crossref]
  10. 2009 - Electro-Fenton process and related electrochemical technologies based on Fenton’s reaction chemistry [Crossref]

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