Adsorption of a spent reactive dyebath by a chitosan bed: study of water reuse, bed regeneration, and UV /Fenton oxidation

In the present paper, a facile process combining chitosan bed adsorption and the UV /Fenton advanced oxidation process for treatment and reuse of spent reactive dyebath waste has been developed. The chitosan bed was very effective in decolouring spent reactive dyebath waste by adsorption enrichment of CI Reactive Red 195, and the water and sodium sulphate therein could easily permeate through the chitosan bed and then be recycled. Although the resulting recycled dyebaths were used 10 times as reconstituted dyebaths for dyeing with CI Reactive Red 195, the colour difference and the relative unlevelness index changes of the dyed samples still remained within acceptable levels. That was also true for CI Reactive Blue 19 in the 11th recycling cycle. As a result, an average saving of 60.4% and 93.4% for water and sodium sulphate, respectively, was achieved with the reuse process for the 11 dyebaths. The exhausted chitosan bed can be regenerated three times by dilute alkali without any significant sacrifice of adsorbability or mass. Emissions of the elution concentrates generated from three regeneration runs of the chitosan bed and then treated by UV /Fenton oxidation were found to meet the most stringent emission standards for both chemical oxygen demand and colour in China. Results reveal that the process combining chitosan bed adsorption and UV /Fenton advanced oxidation is promising for treatment and reuse of spent reactive dyebath waste, which can potentially benefit the environment and reduce operating costs.