Comparative study of the treatment of printing ink wastewater by conductive-diamond electrochemical oxidation, Fenton process, and ozonation
Sustain. Environ. Res., 24(1), 49-58 (2014)
Boulbaba Louhichi and Nasr Bensalah
Advanced oxidation processes, hydroxyl radicals, printing ink wastewater, degradation, mineralization
In this work, the treatment of organics present in printing ink wastewaters such as dyes (methylene blue and rhodamine B), surfactants (sodium dodecylbenzene sulfonate), and solvents (ethylene glycol), as well as actual printing ink wastewaters by advanced oxidation processes, namely conductive diamond electrochemical oxidation (CDEO), Fenton process and ozonation, has been investigated. To compare the efficiency of CDEO, Fenton process and ozonation in the removal of chemical oxygen demand (COD) and total organic carbon (TOC), oxygen-equivalent chemical-oxidation capacity (OCC) has been used to quantify the amount of oxidant utilized in each oxidation process for comparison purpose. Results have shown that CDEO technology has achieved high COD removal of > 95% and TOC of > 90%, however ozonation and Fenton process have been able only to achieve COD and TOC removals of 65-80%. CDEO process was found to utilize 12.9 kg O2 m-3 as OCC to totally remove COD and almost completely mineralize organics; however ozonation and Fenton oxidation utilize 3.3 and 7.1 kg O2 m-3 as OCC to reach 60-80% of COD and TOC removals. These results can be explained by the nature of oxidants involved in the mechanism of degradation of organics in each process. CDEO involves other oxidation pathways, such as anodic oxidation on the surface of Boron Doped Diamond electrode and mediated oxidation by electrogenerated oxidants, in addition to mediated oxidation by hydroxyl radicals. Operation cost analysis has shown that ozonation process has the lowest operation cost in treating actual printing ink wastewaters, while Fenton process was found to have the highest operation cost.