RESUMO
This research investigated the adsorption of propranolol (PROP) by functionalized green carbon nanotubes (MWCNT-B), assessing the influence of pH, in addition to kinetic, equilibrium, and thermodynamic studies and reuse of the material. For this purpose, speciation of PROP and the point of zero charge (pHPZC) of MWCNT-B were performed, indicating a pKa of 9.67 and pHPZC of 3.31. The adsorption tests at different pH values revealed that in the range of pH 3 to 9, there is no significant variation in PROP uptake, despite this, at pH 11, the removal decreases. Regarding PROP adsorption, the equilibrium time ranged from 30 to 90 min, and the PFO model best represented the kinetic data. The Langmuir model was more predictive in representing isotherms (R2 > 0.95), and the adsorption process was spontaneous and favorable (ΔG < - 20 kJ mol-1) and indicated exothermic behavior (ΔH = - 33 kJ mol-1) for PROP removal. In addition, the material showed satisfactory thermal regeneration results and can be reused for four cycles. The results suggest that MWCNT-B is an attractive adsorbent and exhibits effective removal of propranolol from aqueous matrices.
RESUMO
Cefazolin (CFZ) is a ubiquitous antibiotic in hospital settings and has been recognized as an emerging contaminant due to its ecotoxicity. Despite the growing concern around this compound, the literature addressing feasible advanced techniques for CFZ uptake from aqueous matrices is still scarce. Thus, the objective of this work was to evaluate the adsorption of cefazolin on Spectrogel® organoclay in a batch system as an efficient remediation method. The optimization of experimental conditions was determined by a central composite rotational design. A pH study, as well as equilibrium, kinetic, and thermodynamic assays, was performed to assess the adsorption of CFZ on Spectrogel®. The kinetic and equilibrium models that best described the system were the external mass transfer resistance and Sips models, respectively. A removal efficiency above 80% was achieved, and the maximum adsorption capacity at 25 °C was 398.6 mg g-1. The post-process contaminated organoclay was thermally regenerated. The outcomes of this work indicate that Spectrogel® is an environmentally friendly adsorbent for the removal of cefazolin from wastewater.
Assuntos
Águas Residuárias , Poluentes Químicos da Água , Adsorção , Antibacterianos , Cefazolina , Concentração de Íons de Hidrogênio , Cinética , Projetos de Pesquisa , Termodinâmica , Águas Residuárias/química , Poluentes Químicos da Água/análiseRESUMO
Cefazolin (CFZ) is an antibiotic widely used in veterinary and human medicine that has been detected in high residual levels in the environment and is therefore considered an emerging contaminant. This work evaluated the adsorption of this contaminant by Spectrogel® type C organoclay, in continuous mode using a fixed-bed column. The fluid dynamics and the effect of the CFZ concentration were evaluated. In addition, prior and post-process organoclay were characterized. The continuous system under the conditions of C0 = 0.3 mmol/L and Q = 0.1 mL/min presented lower values of mass transfer zone (5.88 cm), whereas the system with C0 = 0.5 mmol/L and Q = 0.1 mL/min achieved higher CFZ adsorption capacity (20 µmol/g). Phenomenological and mass-transfer models were applied to the experimental data. The dual-site diffusion (DualSD) model better described the breakthrough (BTC) data. Furthermore, density functional theory (DFT) calculation was performed at the molecular level to provide a better comprehension of CFZ adsorption.