Conventional and photocatalytic degradation of aromatic amines from nitrite determination wastes

Abstract

Different methods such as KMnO4 oxidation, TiO2-photocatalysis and photo-Fenton reaction have been employed for the degradation of wastes from the spectrophotometric determination of in seawater. The optimisation of the degradation process was determined by total organic carbon (TOC) measurements. Experimental parameters such as pH, TiO2, H2O2, Fe3+ or Fe2+ concentrations have been checked. The highest TOC reduction was achieved by applying the photo-Fenton reaction with 0.02 g of FeSO4 and 3 mL of H2O2 for every 100 mL of sample. Mean TOC reductions of about 78 and 47% were achieved by photo-Fenton reaction and TiO2-photocatalysis, respectively. The addition of potassium oxalate to the photo-Fenton reaction enhanced the mineralisation efficiency. The mineralisation of individual components of the samples by photo-Fenton reaction was also attempted. Sulphanilamide was degraded to a large extent since TOC reductions of about 83% were achieved. In contrast N-(1-naphtyl-)-ethylenediamine degradation was negligible and TOC reduction was never larger than 6%. Degradation of N-(1-naphtyl-)-ethylenediamine by KMnO4 yielded a TOC reduction of 40.89%. The application of a KMnO4 pretreatment enhances the oxalate--photo-Fenton reaction efficiency by greatly reducing the irradiation time. The solar photo-Fenton reaction of the sample gave a TOC reduction of about 70%. After the treatment wastes lose their characteristic pink colour becoming nearly transparent or showing a very subtle yellowish colour.