Removal of Azo Dyes Using a Coupled Adsorption and Electrochemical Oxidation Process—The Impact of Effluent Conditions

Azo dyes are a major cause of environmental pollution, but under lab-based conditions can be removed using a coupled adsorption and electrochemical oxidation process; the Nyex Rosalox™ (NR) process. However, wastewater effluents are more complex than tap water, indicating that there is a need to assess how altered effluent conditions affect the adsorption of azo dyes onto the adsorbent used (Nyex™ 2000) and overall removal efficiency of the NR process. Analysis indicates that higher temperatures, the addition of minor amounts of sodium chloride, or acidification increased adsorption, while the presence of dissolved organic carbon (DOC) only showed a minor impact if compared to baseline tap water conditions and appears to be dye-specific. Analyses further indicated that effluent conditions could have a major impact on the overall dye removal efficiency using the NR process, with up to 48% more being removed during acidic or saline conditions and, to a lesser extent, when DOC was present. Increased temperature or alkalinity had minimal impact, with inconsistent results across the dyes assessed. Combined, this highlights that effluent-specific conditions can have a major impact on the removal efficiency and should be considered during the planning stage of the azo dye treatment process.