ABSTRACT
Oils are subject to several reactions that lead to physical-chemical, sensory and nutritional deterioration. This deterioration process is called rancidity or lipid oxidation, a spontaneous and irreversible phenomenon that can be delayed by the addition of antioxidants. Usually, vegetable oil producers choose to add antioxidants to the upper limit permitted by applicable law as it is not entirely clear the ideal dosages of pure or combined antioxidants designated for this purpose. In order to determine the optimum dosage of antioxidants that minimizes the impact of lipid oxidation of soybean oil bottled in PET (ethylene terephthalate) and replace the traditional antioxidant tert-Butylhydroquinone (TBHQ), an accelerated oven shelf-life test was performed. The antioxidants ascorbyl palmitate (AP), mix of tocopherols and rosemary extract (RE) were evaluated, pure and in combination, at different dosages. Most of the evaluated antioxidants delayed lipid oxidation of soybean oil, but a mixture containing AP and RE presented results of TOTOX statistically lower (higher oxidative stability) than that with TBHQ. One the other hand, regarding OSI at 120 °C, the result obtained by that mixture was statistically lower (less oxidative stability) than that obtained with TBHQ, in both evaluated dosages.
ABSTRACT
In this study, ozonation of raw textile wastewater was conducted in a pilot-scale plant and the efficiency of this treatment was evaluated based on the parameters color removal and soluble organic matter measured as chemical oxygen demand (COD), at two pH values (9.1 and 3.0). Identification of intermediate and final degradation products of ozone pre-treatment, as well as the evaluation of the final ecotoxicity (Lumistox test) of pre-treated wastewater, was also carried out. After 4h of ozone treatment with wastewater recirculation (flow rate of 0.45 m(3)h(-1)) the average efficiencies for color removal were 67.5% (pH 9.1) and 40.6% (pH 3.0), while COD reduction was 25.5% (pH 9.1) and 18.7% (pH 3.0) for an ozone production capacity of 20 g h(-1). Furthermore, ozonation enhances the biodegradability of textile wastewater (BOD(5)/COD ratios) by a factor of up to 6.8-fold. A GC-MS analysis of pre-treated textile wastewater showed that some products were present at the end of the pre-treatment time. In spite of this fact, the bacterial luminescence inhibition test (Lumistox test) showed a significant toxicity reduction on comparing the raw and treated textile wastewater. In conclusion, pre-ozonation of textile wastewater is an important step in terms of improving wastewater biodegradability, as well as reducing acute ecotoxicity, which should be removed completely through sequential biological treatment.
