The resulting solutions from the cotton fabrics dyeing using the trichromy Procion HEXL, with NaCl as electrolyte, were electrochemically treated. These dyes have two azo groups as chromophores and two monochlorotriazinic groups as reactive groups in their structure. The combined oxidation/reduction at 125 mA cm-2 in a filter-press cell without compartment separation was carried out using an anode of Ti/SnO2-Sb-Pt and a cathode of stainless steel. This procedure has been effective in previous experiments using sulphate as electrolyte. A significant decrease in total organic carbon (TOC), chemical oxygen demand (COD), and total nitrogen (TN) was obtained. Moreover, the process took place efficiently. The average oxidation state (AOS) and the carbon oxidation state (COS) data confirmed the presence of stable oxidized intermediates in the electrolysed solution. The chromatography and the UV-Visible spectrophotometry assays indicated that full decolourisation is obtained at a loaded charge of around 0.81 Ah L-1 which is associated with an electrical energy per order (EEO) of 1.20 kWh m-3.
Keywords: Chloride; Dyestuff wastewater; Electrochemical treatment; Tin dioxide anodes; Trichromy.
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