Avaliação numérica e experimental de poluentes emergentes no processo de adsorção

Abstract

The increasing consumption of pharmaceuticals by urban society, coupled with inadequate disposal, has led to the contamination of water bodies by pharmaceuticals. These emerging contaminants have a high potential for accumulation in the environment and can cause toxic effects and pose risks to aquatic ecosystems and human life, as they may end up being consumed inappropriately. These medications, such as Caffeine, Sodium Diclofenac, and Paracetamol, are relatively low-cost and easily accessible to the population, and they are among the most commonly used drugs in Brazil, especially for everyday use. However, the misuse of these medications, inadequate disposal, and the absence of specific regulations have brought to light a problem that is still poorly studied, as the potential long-term harmful impact of these pollutants on the environment is unknown. In this study, the feasibility of using activated carbon from bovine bones as an adsorbent for the removal if three contaminants, namely Caffeine, Sodium Diclofenac, and Paracetamol, was investigated. Adsorption is a versatile method with relatively low cost, and in this case, activated carbon is a widely used material in this technique, mainly due to its well-developed porous structure and high surface area. For this study, activated carbon from bovine bones was used in particle sizes of 0.1 mm and 0.297 mm. The adsorption process showed Paracetamol as a pollutant with high affinity for activated carbon from bovine bones, achieving a removal efficiency of 83.85%. Furthermore, an increase in the removal of this pollutant of approximately 16.5% was recorded when the finer particle size of 0.1 mm was used. The kinetic test showed that the removal equilibrium is reached in about 5 minutes. In terms of kinetic models, both pseudo-first-order and pseudo-second-order models were used, and both exhibited excellent fits, with R² values close to 1 and low values of mean relative error. Isothermal tests indicated that an increase in temperature impairs the removal efficiency of Paracetamol, with 30°C being the optimal operating temperature in terms of efficiency. The Langmuir model was chosen due to its simplicity and good fit to the experimental data. At 30°C and an initial concentration of 50 mg/L of Paracetamol, a maximum adsorption capacity of 10.40 mg/g was obtained for the 0.1 mm carbon, achieving a removal exceeding 83%. The calculation of thermodynamic parameters indicated that the adsorption process is exothermic, with predominant physisorption, in agreement with the results of the kinetic experiments. Simulation of the fixed-bed process using the Aspen Adsorption V8.8software package showed that activated carbon from bovine bones can be used as an alternative for continuous treatment of Paracetamol.