Asian Journal of Applied Chemistry Research

The objective of the study was the treatment of the pollutants (dissolved chemical oxygen demand (COD_dis), total organic carbon (TOC) and total and individual polycyclic aromatic hydrocarbons (PAH)) present in the petrochemical industry wastewater (PCI) by sonication. The effects of increasing sonication times (0 min, 60 min, 120 and 150 min), sonication temperatures (25^oC, 30^oC and 60^oC), on the COD_dis, TOC and (PAH) removal efficiencies were researched at a sonication frequency of 35 kHz and a sonication power of 640. All the PAHs and their metabolites were measured by an gas chromatography (Agilent 6890 NC) equipped with a mass selective detector (Agilent 5973 inert MSD) with a capillary column (HP5-MS, 30 m, 0.25mm, 0.25µm)). The CH₄, CO₂ and H₂ gas analysis, COD_dis, TOC and the other pollutants were measured according to Standard Methods. As the sonication time and temperature were increased from 60 to 120 and 150 min, and from 25^oC to 30^oC and to 60^oC, the COD_dis, total PAH and TOC yields increased from 80.16% to 92.15%, from 78.37% to 94.23% and from 79.65% to 96.90%, respectively. The PAHs intermediates namely, 1–methylnaphthalene, 9–hydroxyfluorene, 9,10–phenanthrenequione, benzoic acid, 1,2,3–thiadiazole–4–carboxylic acid, naphthalene, p–hydroxybenzoic acid, fluorene, di–hydroxy pyrene, pyrene di–hydrodiol were sonodegraded with yields of 92.11%, 95.23%, 98.42%, 97.34%, 99.44%, 96.30%, 99.36%, 97.17%, 99.63% and 99.98% respectively, after 150 min, at 25^oC. The presence of CH₄, H₂ and CO₂ gases during sonication showed that the degradation mechanism of the PAHs is ‘‘pyrolysis”.