Sonication of pulp and paper effluent.
Final effluent from a pulp and paper kraft mill was exposed to power ultrasound at 357kHz with the aim of reducing color, turbidity, and chemical oxygen demand (COD). Absorbance measurements showed a bleaching of the effluent at wavelengths above 250nm, indicating loss of aromatic chromophores. Effluent turbidity also decreased. Surprisingly, there was no observable decrease in COD, within experimental error. This is attributed to the presence of bicarbonate and sulfate ions in the final effluent, which react with hydroxyl radicals and effectively block the oxidation of organics in the effluent. This was demonstrated by sonicating solutions of potassium hydrogen phthalate (KHP) containing chloride, bicarbonate, or sulfate ions, which are the major inorganic ions in the final effluent studied. A solution containing only 2.3mM KHP showed a 19% reduction in COD after 6h of sonication. An identical solution with 200ppm chloride also showed a 19% COD reduction. However, solutions with 700ppm sulfate and 400ppm bicarbonate showed COD reductions of 11% and 3%, respectively.
Shaw
Lawton E
LE
Centre for Science, Athabasca University, 1 University Drive, Athabasca, AB, Canada T9S 3A3. lawtons@athabascau.ca
Lee
Dana
D
D001639:Bicarbonates / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007220:Industrial Waste; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010209:Paper; D013010:Sonication; D013431:Sulfates / Q000737:chemistry; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D001639:Bicarbonates; D007220:Industrial Waste; D013431:Sulfates; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical; D010100:Oxygen