Tecnologia supercrítica aplicada ao tratamento de águas contaminadas por fármacos
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2022-04-29
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Universidade Federal de Goiás
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The growth of the world population has led to the increased disposal of pharmaceutical products in the environment. Also, a wide variety of drugs used for the prevention and treatment of diseases have a low metabolic rate in humans and are often released into the environment in their unaltered form. These contaminants may offer potential risks to human health and the ecosystem. As a consequence, water is one of the most affected parts, because it is involved in various human activities. Currently, there are several processes used in water treatment, which use physical, chemical, and biological methods to remove pollutants from wastewater. However, methods of wastewater treatment have not demonstrated efficiency for the complete degradation of these compounds, or they are often impractical to treat a large volume of residues. With regard to the need to effectively treat these pollutants, this study presents the investigation of the supercritical water oxidation (SCWO) process applied in the treatment of aqueous residues contaminated with pharmaceuticals using a continuous flow reactor. For this purpose, it was investigated the degradation of amoxicillin in industrial pharmaceutical effluent, antibiotics, anxiolytics/antidepressants, and antihypertensive/cardiovascular drugs in an aqueous solution. Reaction tests were separated by therapeutic classes. In that way, a total of 20 drugs were evaluated. For all four scenarios related to each pharmaceutical class, the conditions of temperature, flow rate, and H2O2 concentration were optimized to maximize the total organic carbono removal rate (%RCOT). In the degradation of industrial effluent contaminated with amoxicillin, both temperature and flow parameters had the greatest effect on the %RCOT of the liquid phase, whose maximum value reached was 60.1%. In the gaseous product, the formation of H2, CO2, and CH4 stood out with a total volumetric flow of 6.45 mL/min. In the degradation of 6 antibiotics in an aqueous solution, the temperature was the most significant effect to achieve a %RCOT of 64.1%. The gaseous product, mostly H2 and CO2, had a total volumetric flow rate of 18 mL/min, a value almost 3 times greater than the feed flow rate. During the degradation of 5 anxiolytic/antidepressant contaminants, both parameters of temperature and H2O2 concentration had the greatest impact on %RCOT (85.9%). The total gas flow rate was 11 mL/min and, once again, among the 6 gases determined in the gaseous product, H2 and CO2 were more relevant. In the treatment of cardiovascular/antihypertensive drugs, the maximum %RCOT achieved was 92.1%, and both temperature and H2O2 concentration parameters had the greatest influence on this response. CO2 (98%) was the major constituent of the gas composition that had a total volumetric flow of 26.3 mL/min, which corresponds to twice the feed flow rate used. Briefly, for most of the four scenarios studied, the optimized conditions of temperature, flow rate, and H2O2 concentration were approximately 692°C, 6.6 mL/min, and 292% (m/m), respectively. With an exception in the cardiovascular/antihypertensive degradation condition that occurred at a lower temperature (601°C), intermediate flow rate (13.3 mL/min), and low H2O2 concentration (65%; m/m). Furthermore, for all cases evaluated, most of the limits recommended by national and international legislation regulating water quality were met. In the toxicity essays, exposure to the microcrustaceans Artemia salina revealed toxicity for some treated samples. The lethal concentration, in %(v/v), to kill 50% of the population (LC50) were approximately 12%, 555%, 32%, and 4% for industrial effluent with amoxicillin, and for all aqueous solution with antibiotics drugs, anxiolytic/antidepressant drugs, and cardiovascular/antihypertensive drugs, respectively. Given that, the SCWO technology applied to the treatment of wastewater contaminated with drugs revealed simultaneously, high oxidative power of organic matter and production of valuable energy gases, such as H2, methane, and synthesis gas. The toxicity of some molecules produced is a challenging issue to be addressed. However, due to the high oxidative power, volume and speed of waste processing, the positive contributions of SCWO in the treatment of aqueous waste are undeniable.
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DIAS, I. M. Tecnologia supercrítica aplicada ao tratamento de águas contaminadas por fármacos. 2022. 156 f. Tese (Doutorado em Química) - Universidade Federal de Goiás, Goiânia, 2022.