Evaluation of efficiency and capacity of thermal, chemical and ultrasonic regeneration of tetracycline exhausted activated carbon.

Emerging pollutants have received increasing attention because of their potential environmental risks. As conventional treatment processes are not able to completely remove emerging pollutants, such as drugs, for example, the adsorption process is considered a complementary treatment. However, after some time of use, the adsorbent solids used in this type of process become saturated and there may be a higher demand for replacement of these materials, resulting in a large amount of solid waste. In this context, the objective of this study was to evaluate regeneration techniques of adsorbent solid depleted with emerging tetracycline pollutant. For this, tests were performed using three regenerative methods - thermal, chemical and ultrasonic, where through them were analyzed the influence of temperature, type of solvent and sonification time, respectively. Virgin, saturated and regenerated solids were characterized by their physical structure, micro and mesopore distribution and scanning electron microscopy. For all techniques employed, the regeneration efficiency reached values ⁣⁣above 85%. Thermal treatments at 200°C, 100% methanol solution, 100% deionized water with 60 °C heating and ultrasonic treatment at 5 and 20 minutes were chosen as the most viable methods for the study of adsorption/desorption cycles. Compared to the others, the heat treatment at 200°C remained with consistent results until the sixth cycle, presenting a regenerative capacity of 90%. Therefore, it has been selected as the most suitable regenerative agent, ensuring that CAG can be regenerated and used repeatedly in the treatment of tetracycline contaminated waters.