Navegando por Assunto "Contaminantes emergentes"

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Acesso aberto (Open Access)
Adsorção de ciprofloxacino e norfloxacino em solução aquosa por carvão ativado produzido a partir da casca do cupuaçu (theobroma grandiflorum)
(Universidade Federal do Pará, 2024-09-19) NASCIMENTO, Rafael Alves do; COSTA, Cristiane Maria Leal; http://lattes.cnpq.br/0581730621014796; FARIA, Lênio José Guerreiro de; http://lattes.cnpq.br/7428609361678173; https://orcid.org/0000-0002-9534-9998
The extensive use of antibiotics has caused several negative consequences for the environment and human health. Fluoroquinolones (FQs), present in the aquatic environment, are of particular concern. This study investigated the removal of ciprofloxacin (CIP) and norfloxacin (NOR) from aqueous solutions using activated carbon derived from cupuaçu bark (CAC), an unconventional and low-cost adsorbent. The CAC was characterized physicochemically and the adsorption experiments followed the Box-Behnken design, evaluating the effects of contact time, adsorbate concentration and adsorbent dosage on the removal and adsorption capacity of CIP and NOR. The optimal conditions of the adsorption process were determined by the desirability function, and under these conditions the kinetic, isothermal and thermodynamic adsorption experiments were carried out. CAC showed a similar yield (50.22%) to other activated carbons with H3PO4, low humidity (4.81%) and ash (4.27%). Acidic functional groups were identified in CAC in greater quantities (3.982 mg Eq/g) than basic ones (0.092 mg Eq/g), and the pHPcz was found to be 3.85. A high surface area was quantified (1335.66 m²/g), with an average pore volume and diameter of 0.753 cm³/g and 2.206 nm, respectively. Due to the zwitterionic characteristics of CIP and NOR, adsorption was more efficient at pH 5.0. In this condition, the CAC assumes a basic character and as the CIP and NOR molecules are predominantly in their cationic forms, the electrostatic interaction is facilitated. The optimal conditions for CIP adsorption were: time of 266.40 min, concentration of 192 mg/L and dosage of 0.57 g/L; for NOR, 273.60 min, 186 mg/L and 0.55 g/L. The pseudo-second order (PSO) model and the external mass transfer resistance (EMTR) model best fitted the experimental data, indicating that external mass diffusion was the controlling step of adsorption. The Langmuir model indicated that adsorption occurred in a monolayer, with CIP adsorption capacities of 6.02 mg/g and NOR of 5.70 mg/g. Thermodynamic analysis revealed that the adsorption of CIP and NOR on CAC predominantly involves physisorption. The suggested mechanism for the adsorption of CIP and NOR on CAC may involve electrostatic forces, π-π interactions and hydrogen bonds. CAC regeneration was more effective with NaOH, but after two cycles of use, the percentage of CIP and NOR removal decreased to less than 50%. Thus, CAC proved to be an effective and low-cost adsorbent for the removal of CIP and NOR, also contributing to the reuse of cupuaçu biomass.
Acesso aberto (Open Access)
Fotocatalisadores de dióxido de titânio dopados com metais de transição: síntese, caracterização e aplicação na fotodegradação de fármacos
(Universidade Federal do Pará, 2024-12-27) AZEVEDO, Carla Arnaud de; FARIA, Lênio José Guerreiro de; http://lattes.cnpq.br/7428609361678173
Heterogeneous photocatalysis has shown promise in ecological remediation and in the adequate treatment of pharmaceuticals as emerging contaminants. This study evaluated the photocatalytic activity of materials synthesized from the modification of the TiO₂ surface with transition metals (copper and cobalt) at concentrations of 0.5% and 1.5%, analyzing the physical, chemical and textural properties of the materials by N2 physisorption (BET) analysis, X-ray diffractometry (XRD), scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM-EDS) and Fourier transform infrared (FT-IR). The experimental tests were carried out in an annular photoreactor with UV mercury lamp, following the Box-Behnken design, to evaluate the influence of catalyst mass (50 – 150 mg.L-1 ), drug concentration (2 – 8 mg.L-1 ) and irradiation time (60 – 120 min) on the photodegradation of acetaminophen (ACT) and diclofenac sodium (DCF). The BET results indicated that the materials have a mesoporous structure with an average pore diameter of 14.52 nm. XRD characterization confirmed the mixed structure of anatase and rutile and the absence of metal oxide peaks. The SEM-EDS analysis revealed irregular surfaces formed by misshapen grains and small particles attributed to metal oxides. The FT-IR showed O-H and Ti-O stretching bands, characteristic of photocatalytic materials. The FTCu1.5 photocatalyst was chosen for use in the photodegradation tests of the drugs due to its surface area, porosity and good anatase and copper content. The photocatalysis tests, in comparison with the photolysis tests, showed superior results, evidencing the functionality of the photocatalyst used. The degradation percentages reached 100% for both drugs and the concentration of the pollutant solution had a negative effect on the response variables, indicating that degradation increases with the reduction of the initial concentration of this solution. The proposed polynomial models presented a coefficient of determination (R²) > 0.9 and good predictive capacity. The Response Surface Methodology (RSM) and Desirability Function analyses indicated that it is possible to obtain a substantial reduction in the amount of photocatalyst used, when combined with an adequate adjustment in the irradiation time. The optimal conditions within the experimental domain for ACT are mcat = 100 mg.L-1 , CFA = 2 mg.L-1 and tIRR = 75 minutes, resulting in EffACT(%) = 99.05% and for DCF, the optimal conditions were mcat = 72 mg.L-1 , CFA = 2 mg.L-1 and tIRR = 65 minutes, resulting in EffDCF(%) = 90.39%. The developed photocatalyst significantly degraded the drugs and demonstrated promise for photocatalysis applications.