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6CCVD Research

Electrochemical Oxidation of Pollutants in Textile Wastewaters Using BDD and Ti-Based Anode Materials

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-11-15
JournalTextiles
AuthorsCĂ©sar Afonso, Carlos Y. Sousa, Daliany M. Farinon, Ana Lopes, Annabel Fernandes
InstitutionsUniversity of Beira Interior
Citations5
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This study evaluated the performance of Boron-Doped Diamond (BDD) and four commercial Titanium-based Mixed Metal Oxide (Ti/MMO) anodes for the electrochemical oxidation (EO) of real textile wastewater (TW).

  • BDD Superiority: BDD consistently achieved the best results, demonstrating the highest organic load removal rate and mineralization degree due to its “non-active” nature, which favors direct oxidation by weakly adsorbed hydroxyl radicals (‱OH).
  • Best MMO Alternative: Ti/RuO2-TiO2 was the most effective Ti/MMO anode, achieving approximately 61% Chemical Oxygen Demand (COD) removal and complete color removal after 8 hours at 300 A m-2.
  • Energy Efficiency: Ti/RuO2-TiO2 exhibited a Specific Energy Consumption (Esp) similar to BDD, particularly at the lower current density (100 A m-2), suggesting it is a feasible, lower-cost alternative despite lower mineralization rates.
  • Mineralization vs. Partial Oxidation: Ti/MMO anodes are “active” materials, promoting indirect oxidation via electrogenerated active chlorine species (e.g., HOCl, OCl-). This mechanism leads primarily to partial oxidation, resulting in significantly lower Dissolved Organic Carbon (DOC) removal compared to BDD.
  • Worst Performance: Ti/IrO2-Ta2O5 showed the poorest performance, yielding negligible organic load removal and an Esp four times superior to BDD.
  • Color Removal Mechanism: Complete color removal was achieved rapidly by both BDD and Ti/RuO2-TiO2, primarily attributed to the effectiveness of active chlorine species generated from the high initial chloride concentration (756 mg L-1).

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Initial Chemical Oxygen Demand (COD)738 ± 7mg L-1Textile Wastewater (TW) Sample
Initial Biochemical Oxygen Demand (BOD5)214 ± 1mg L-1TW Sample
Biodegradability Index (BOD5/COD)0.29-Indicates microbial inhibition
Initial Chloride Concentration (Cl-)756 ± 1mg L-1High concentration favors active chlorine generation
Initial pH9.6 ± 0.4-Alkaline TW sample
Primary Applied Current Density (j)300A m-2Standard test condition
Secondary Applied Current Density (j)100A m-2Optimized test condition
Anode Immersed Area10cm2Electrochemical cell setup
COD Removal (BDD, 300 A m-2)~70%Highest removal achieved
COD Removal (Ti/RuO2-TiO2, 300 A m-2)~61%Best MMO performance
Lowest Specific Energy Consumption (Esp)~100W h gCOD-1Achieved by Ti/RuO2-TiO2 at 100 A m-2
Highest Specific Energy Consumption (Esp)~550W h gCOD-1Ti/IrO2-Ta2O5 at 300 A m-2

Key Methodologies

Section titled “Key Methodologies”

The electrochemical oxidation (EO) experiments were conducted using the following parameters and materials:

  1. Wastewater Matrix: Real textile wastewater (TW) characterized by high COD (738 mg L-1) and low biodegradability (index 0.29).
  2. Electrochemical Setup: Undivided glass cell containing 200 mL of TW, operated in batch mode for 8 hours.
  3. Anode Materials Tested:
    • Non-Active Reference: Boron-Doped Diamond (BDD).
    • Active Ti/MMO Anodes: Ti/RuO2-TiO2, Ti/IrO2-Ta2O5, Ti/IrO2-RuO2, and Ti/RuO2/IrO2-Pt.
  4. Cathode Material: Stainless-steel plate.
  5. Electrode Geometry: Anode and cathode positioned parallel with a 0.5 cm gap; immersed area of 10 cm2 for both.
  6. Operational Conditions:
    • Constant current density (j) applied at 300 A m-2 for initial screening.
    • Optimized testing conducted at 100 A m-2 for BDD and the best MMO (Ti/RuO2-TiO2).
    • Continuous magnetic stirring maintained at 300 rpm to ensure adequate mass transport.
  7. Performance Metrics: Pollutant removal assessed via COD, DOC, and color decay; energy efficiency evaluated using Specific Energy Consumption (Esp) calculated in W h gCOD-1.

Commercial Applications

Section titled “Commercial Applications”

The findings directly support the engineering and deployment of electrochemical systems in industrial water management, focusing on highly recalcitrant waste streams.

  • Textile and Dyeing Industry: Direct application for treating highly colored and poorly biodegradable effluents, enabling compliance with discharge limits and supporting water reuse initiatives.
  • Industrial Wastewater Treatment (IWW): EO using BDD or optimized Ti/MMO serves as a robust tertiary treatment step for complex industrial matrices containing persistent organic pollutants (POPs).
  • Electrode Material Selection: Provides critical performance and cost trade-off data for selecting anodes:
    • BDD: Preferred for high mineralization requirements (complete DOC removal) despite high initial cost.
    • Ti/RuO2-TiO2: Recommended as a cost-effective alternative for applications prioritizing high COD and color removal where complete mineralization is not strictly required.
  • Advanced Oxidation Processes (AOPs): Integration of EO into existing treatment trains (e.g., complementing biological treatment inhibited by high toxicity or low biodegradability).
  • Water Disinfection: The high efficiency of active chlorine generation, particularly by Ti/MMO anodes, ensures simultaneous color removal and water disinfection.
View Original Abstract

This study aims to evaluate the electrochemical oxidation of real textile wastewater using boron-doped diamond (BDD) and different titanium-based mixed metal oxide (Ti/MMO) commercial anodes, namely Ti/RuO2-TiO2, Ti/IrO2-Ta2O5, Ti/IrO2-RuO2, and Ti/RuO2/IrO2-Pt. Experiments were conducted in batch mode, with stirring, at different applied current densities. The results showed that BDD attained the best results, followed by Ti/RuO2-TiO2, which achieved total color removal, a chemical oxygen removal of 61% with some mineralization of organic compounds, and a similar specific energy consumption to BDD. The worst performance was observed for Ti/IrO2-Ta2O5, with a specific energy consumption four times superior to BDD due to a negligible organic load removal.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2014 - The Status of Water Reuse in European Textile Sector [Crossref]
  2. 2007 - Electrochemical Oxidation of Textile Wastewater and Its Reuse [Crossref]
  3. 1999 - A Review of Electrochemical Treatments for Colour Elimination [Crossref]
  4. 2023 - Wastewater Treatment by Anodic Oxidation in Electrochemical Advanced Oxidation Process: Advance in Mechanism, Direct and Indirect Oxidation Detection Methods [Crossref]
  5. 2023 - A Comprehensive Review on Electro-Oxidation and Its Types for Wastewater Treatment [Crossref]
  6. 2021 - Anodic Oxidation of Synthetic Refinery Effluent on Lead Anode: Mass Transport and Charge Rate Balance [Crossref]
  7. 1994 - Electrocatalysis in the Electrochemical Conversion/Combustion of Organic Pollutants for Waste Water Treatment [Crossref]
  8. 2021 - Electrochemical Oxidation Technology to Treat Textile Wastewaters [Crossref]

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