ABSTRACT
This study investigates the ozonation of 2-naphthalenesulfonate (2-NS) combined with ultraviolet (UV) radiation. Naphthalenesulfonic acids are of importance as dye intermediates for the dye and textile auxiliary industries. Its derivatives, such as 2-NS, have been found in rivers and tannery effluents causing pollution problems. Thus, the 2-NS is of concern for the aquatic pollution control especially in the surface and waste waters. Ozonation combined with UV radiation is employed for the removal of 2-NS in the aqueous solution. Semibatch ozonation experiments were proceeded under different reaction conditions to study the effects of ozone dosage and UV radiation on the oxidation of 2-NS. The concentrations of 2-NS and sulfate are analyzed at specified time intervals to elucidate the decomposition of 2-NS. In addition, values of pH and oxidation reduction potential are continuously measured in the course of experiments. Total organic carbon is chosen as a mineralization index of the ozonation of 2-NS. The mineralization of 2-NS via the ozonation is remarkably enhanced by the UV radiation. These results can provide useful information for the proper removal of 2-NS in the aqueous solution by the ozonation with UV radiation.
Subject(s)
Arylsulfonates/chemistry , Arylsulfonates/radiation effects , Ozone/chemistry , Ultraviolet Rays , Water/chemistry , Carbon/analysis , Coloring Agents/chemistry , Hydrogen-Ion Concentration , Industrial Waste , Oxidation-Reduction , Solutions/chemistry , Sulfates/chemistry , Time FactorsABSTRACT
This research investigates the aqueous toxicity occurring during color formation due to ozonation in a semi-batch reactor. The tested mono-substituted aromatic compounds were aniline, phenol (-NH2' -OH, electron-donating group), nitrobenzene and benzoic acid (-NO2' -COOH, electron-withdrawing group). The results revealed that the aqueous toxicity of the Microtox assay from oxidized samples during the early stage of ozonation increased when the color formation was observed, except in the case of nitrobenzene under high pH conditions. Toxicity typically reached a peak at or near the moment of maximum color intensity. Ozonation of these aromatic compounds showed a large increase in toxicity, and the 50% effective concentration (EC50) expressed as chemical oxygen demand (COD) (mg 1(-1)) decreased to 1.4 (aniline), 1.2 (benzoic acid), 0.8 (phenol) and 0.6 (nitrobenzene) orders-of-magnitude. Moreover, the aromatic compounds with an electron-donating group promoted color formation more than did the electron-withdrawing group substituted compounds.
Subject(s)
Aniline Compounds/toxicity , Benzoic Acid/toxicity , Carcinogens/toxicity , Nitrobenzenes/toxicity , Ozone/chemistry , Phenol/toxicity , Water Purification , Aniline Compounds/chemistry , Benzoic Acid/chemistry , Carcinogens/chemistry , Hydrogen-Ion Concentration , Nitrobenzenes/chemistry , Phenol/chemistry , Photobacterium , Toxicity TestsABSTRACT
This study was undertaken to investigate the color forming phenomena and biotoxicity related problems during the initial stage of ozonation in the wastewater containing phenol or aniline. Experimental results indicate that the phenol under alkaline condition and aniline in all pH conditions cause a serious color problem during the period of early initial ozonation. In addition, the ozonated aniline exhibited more severe color formation than the ozonated phenol did. Both of these compounds revealed that either a high compound concentration or low ozone dosage applied incurred a strong color forming phenomena. Moreover, according to the Microtox test, both ozonated byproducts increased the toxicity during early ozonation when the color formation occurred. The EC50-value as COD decreased from 0.72 (for phenol, pH = 7) to 1.38 (for aniline, pH = 4) orders-of-magnitude. This observation implies that the ozonated color formation would generate new toxicity problems if these colored matters were not further oxidized.
