Estudo de sorção e dessorção de hidroxicloroquina e ivermectina em lodo de esgoto da região Oeste do Paraná

Abstract

The presence of pharmaceuticals in ecosystems is considered an environmental concern because these substances present potential risks to human health and that of other species. The entry of pharmacological contaminants into the environment can occur in different ways, with domestic effluent being one of the main routes. With the COVID-19 pandemic, medications such as hydroxychloroquine (HCQ) and ivermectin (IVM) have shown an increase in consumption patterns, and little is known about the environmental impacts related to combating the disease around the world, as well as the behavior of these drugs in the environment. Therefore, in this research we aim to study the sorption and desorption of hydroxychloroquine and ivermectin in sewage sludge and thus contribute to the prospect of the interaction of these analytes in this environmental compartment. The samples used were collected at six different points in a wastewater treatment plant in Santa Helena, a city in the Western Region of Paraná and characterized after air drying during 30 days. The concentration measurements of the analytes in solution took place using molecular absorption spectrometry in ultraviolet region. The kinetic and equilibrium tests for sorption and desorption occurred using the batch method considering different temperatures. The kinetic data for the sorption of hydroxychloroquine presented adequate adjustments to the pseudo-first order (R²=0.89 to 0.99) and pseudo-second order (R²=0.92 to 0.99) kinetic models, while for ivermectin presented satisfactory fits to the pseudo-second order (R²=0.86 to 0.99) and Elovich (R²=0.90 to 0.99) models. The sorption isotherms evaluated at 20, 25, 30 and 35 °C were fitted to the Langmuir and Freundlich models. For both drugs, a better fit to the Langmuir model was observed (R²=0.30 to 0.86 for HCQ and R²=0.92 to 0.98 for IVM), indicating a greater chemical character of the sorption process of analytes in sludge of sewage. The specific sorption was 43.3 mg g-1 and 28.7 mg g-1 for hydroxychloroquine and ivermectin, respectively. The highest percentage of desorption obtained was 49.45%, obtained for hydroxychloroquine, while for ivermectin no desorption was observed under the study conditions. Thus, it was possible to confirm that both drugs are retained by sewage sludge. Hydroxychloroquine showed greater interaction with sample P3 (sludge from the reactor outlet) while ivermectin was adsorbed in greater quantities by sample P1 (raw sludge from the Parshall flume). The weakest interactions between adsorbent and adsorbate were observed for sample P2 (dry raw sludge from the Parshall flume cleaning box), when evaluating hydroxychloroquine, and sample P4 (sludge from the mineralization bed), when evaluating ivermectin. The thermodynamic study revealed that the adsorption of hydroxychloroquine is spontaneous, endothermic and involves increasing the randomness of the solid-liquid interface for all temperatures evaluated. A similar result was obtained for ivermectin, in which only the adsorption at P4 proved to be non-spontaneous, exothermic and with negative entropy variation. The characterization of the samples was essential for understanding the results acquired in the kinetic and equilibrium study and the mobility of this pharmaceuticals in wastewater treatment plants.