Water pollution, particularly from elevated fluoride ion (F⁻) concentrations, is a significant challenge in many developing countries, particularly those relying on groundwater. The stable form of fluoride, F⁻, poses health risks, leading to concerns about various diseases and harmful effects. Despite global efforts, high F⁻ concentrations (>1.5 mg L⁻¹) persist in numerous countries, requiring effective and sustainable removal methods. Adsorption, known for its simplicity, cost-effectiveness, and efficiency, stands out as a promising technique for F⁻ removal from drinking water. Successful commercial implementation necessitates the optimization of separation conditions. This systematic literature review focuses on the adsorption process for F⁻ removal, exploring parameters such as temperature, adsorbent particle size, pH, adsorbent mass, and co-existing ions for efficient removal. Observations indicate that, despite the utilization of a diverse range of adsorbents, several limitations persist. These include low adsorption capacity, a sluggish adsorption rate, a restricted pH range, and high associated costs. The mechanistic understanding of adsorption and the ongoing development of novel adsorbents remain focal points for future research. Additionally, there is a need to explore alternative kinetic models grounded in statistical factors and give due consideration to thermodynamic studies.

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.

The present study investigated the application of functinalized adsorbents in the removal of tetracycline in water by adsorption. Activated carbon was impregnated with iron chloride, copper sulfate and hydrogen peroxide, in order to improve its adsorption properties. The solids were characterized by adsorption/desorption isotherms N₂, XRD, FTIR and SEM. The influence of pH, adsorbent concentration and contact time parameters was evaluated. The results using activated carbon as adsorbent and initial TC concentration of 20 mg.L⁻¹ showed that 93% TC removal was achieved at pH 4.0, contact time of 120 minutes and 30 g.L⁻¹ adsorbent concentration. Experiments applying the functionalized solids showed a faster initial adsorption kinetics. Also, no pH adjustment was required (pH 6.0). In addiction, a minimum of 50% reduction in adsorbent mass (15, 10 and 5 g.L⁻¹ for CA–H₂O₂, CA–Fe and CA–Cu, respectively) was observed, compared to the untreated solid. The pseudo-second-order kinetic model was chosen as the optimal model for the study. The application of FeCl₃, CuSO₄ and H₂O₂ composites as adsorbent solids are technically feasible for the removal of tetracycline in wastewater treatment.

Among all emerging contaminants, pharmaceutical compounds as tetracycline (TC) can cause potential environmental impact in water quality. In this work, the removal of TC drug on activated carbon from aqueous solution was studied and the best operating parameters were obtained. In addition, a real aqueous matrix was enriched with TC and the optimized conditions were applied to study the adsorption process efficiency. For this, the influence of pH, contact time between phases and dosage of adsorbent solid was evaluated. The investigation of kinetics, equilibrium and thermodynamic was also performed. The adsorbent material was characterized by SEM analysis and N₂ adsorption/desorption isotherms to confirm its properties. Batch experiments showed that the most suitable experimental conditions for adsorption in aqueous solution were: pH 4.0, contact time 90 min and dosage of adsorbent solid 30 g.L⁻¹. Under these conditions, it was possible to obtain 92.7% of TC removal with predominance of a spontaneous, favorable and endothermic chemisorption process. Adsorption experiments with real aqueous matrix provided 99.4% TC removal. These results show the potential of adsorption as a wastewater treatment applied to remove emerging pollutants as TC from real aqueous contaminated water.