Remoção de fármacos por adsorção utilizando argila organofílica comercial (cloisite 30b).

Abstract

Due to their widespread consumption, drugs represent an increasing share of this class of pollutants. These substances can have harmful effects on human health and ecosystems, mainly due to their potential for bioaccumulation and biomagnification. Despite the application of secondary treatments, effluents can still contain a large amount of contaminants, which are later released into water bodies. The main objective of this study was to evaluate the removal of drugs (Chlorhexidine and Nystatin) by means of adsorption, using the commercial organophilic clay Cloisite 30B. In addition, we sought to understand the affinity of different drugs with the mentioned adsorbent, in order to select the system with the highest removal efficiency. The commercial organophilic clay (Cloisite 30B) underwent X-ray Diffraction analysis (XRD) and Infrared Spectroscopy for its characterization. The adsorption capacity of the drugs was evaluated through pH variation studies, as well as adsorption tests under controlled conditions using a 23 factorial design. The objective was to determine the best conditions for the process, measuring the removal percentage (% Rem ) and the removal capacity at steady state (qeq) as responses. Chemical kinetics were determined and fitted using pseudo-first order and pseudo-second order models. Furthermore, adsorption equilibrium isotherms were constructed, which were fitted to the Langmuir, Freundlich, Sips, Temkin and Redlich-Peterson models. The results obtained showed that the pH of the synthetic solution containing Chlorhexidine and Nystatin did not significantly affect the removal percentage. Through the factorial design, a removal rate of approximately 95.77 % was identified for Chlorhexidine, and the statistical analysis indicated that the removal percentage (% Rem) is influenced only by the initial concentration. Furthermore, the adsorption capacity is impacted by variations in initial concentration, time and the interaction between these two variables. In the case of Nystatin, a removal rate of about 88.00 % was obtained and the statistical analysis indicated that the removal percentage (% Rem) is influenced only by the mass, while the adsorption capacity is impacted by variations in concentration initial weight, the mass and the interaction between these two variables. The investigation of the adsorption kinetics revealed that Chlorhexidine has a fast adsorption rate, which stabilizes in approximately 6 minutes. As for Nystatin, kinetic equilibrium occurs around 30 minutes. After kinetic adjustments, it was found that the model that best fits both Chlorhexidine and Nystatin is the pseudo-second order model, confirming that the rate control mechanism is chemical adsorption. The Sips isotherm described the adsorption equilibrium for both Chlorhexidine and Nystatin, showing that the adsorbent used is an excellent alternative for removing drugs from contaminated effluents.