Electrochemical treatment of the pollutants generated in an ink-manufacturing process

The effluents of ink-manufacturing processes contain a large variety of pollutants such as dyes, surfactants, biocides, water soluble solvents, etc. In this work, the electrochemical oxidation of several dyes (methylene blue and rhodamine B), solvents (monoethylene glycol, diethylene glycol and glycerol) and surfactants (sodium dodecylbenzenesulfonate) has been studied. To carry out the electrolyses, a bench-scale plant with a single-compartment electrochemical flow-cell was used. Boron doped diamond (BDD) was used as anode and stainless steel (AISI 304) as cathode. For all the compounds tested, the conductive diamond electrooxidation allows achieving the almost complete removal of COD of the waste with a very high current efficiency. The efficiencies of the electrochemical processes seem to depend on the current density and on the nature of the anions contained in the waste (chlorine, sulphate, phosphate). Thus, it has been observed that the use of chloride media favours the treatment of dyes. On the contrary, the use of sulphate- or phosphate-containing solutions improves the removal of the aliphatic compounds studied (solvents). These results suggest an important role of the mediated electrochemical processes on the overall performance of the reaction system.