RESUMEN
The removal of the widely used antibiotic norfloxacin (NOR), the presence of which has been reported in natural water, was evaluated using rice (RH) and coffee (CH) husk wastes as adsorbents. Low particle sizes and natural pH in distilled water favored NOR elimination in both materials. In order to investigate the type of adsorption, the data was adjusted to the Langmuir, Freundlich and Redlich-Peterson isotherms. The best fit for the Langmuir and Redlich-Peterson isotherms suggested a monolayer-type adsorption model. Kinetic models of pseudo first and second order were also evaluated, the latter being the most suitable to represent the NOR adsorption phenomenon. Meanwhile, the intraparticle diffusion model indicated that the adsorption of NOR occurs both at the surface and within the pores of the material. Studies performed on thermodynamic aspects such as activation energy (Ea), enthalpy change (ΔHË) and Gibbs free energy change (ΔGË) suggest that the physisorption of the pollutant takes place through a spontaneous endothermic process. Additionally, PZC determination, Boehm method, chemical composition, thermodynamic analysis, and FTIR spectra before and after the adsorption of the antibiotic suggest that in CH adsorbents this occurred mainly through electrostatic interactions, while in RH hydrogen bonds also contributed significantly. Finally, the efficiency of natural adsorbents for the removal of NOR was evaluated in synthetic matrices of municipal wastewater and urine, and promising results were obtained despite the complexity of these matrices. The results presented in this work show the potential application of RH and CH residues as a low-cost alternative for the removal of NOR even in complex matrices. However, despite the similarities between the materials, CH waste showed better properties for the removal of the tested NOR due to its higher surface area, lower PZC and higher number of acid groups.
Asunto(s)
Norfloxacino/aislamiento & purificación , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua , Adsorción , Coffea , Café , Concentración de Iones de Hidrógeno , Cinética , Oryza , Temperatura , Termodinámica , Agua , Abastecimiento de AguaRESUMEN
The electrochemical degradation of the fluoroquinolone antibiotic norfloxacin (NOR) on Ti/IrO2 anodes, in several aqueous matrices was evaluated. For this purpose, initially the performance and degradation routes of the technology at several pH values (3.0, 6.5, 7.5 and 9.0) and in the presence of some of the most common anions in real water matrices (Cl-, HCO3-, SO42- and NO3-) were determined. The results showed that the degradation of NOR can occur through both direct elimination at the electrode surface and mediated oxidation, via the electrogeneration of oxidative agents, such as active chlorine species and percarbonate ions, which come from chloride and bicarbonate oxidation, respectively. Conversely, nitrate ions showed to inhibit the efficiency of the system. Concerning the pH, the efficiency of the process in the presence of chloride ions followed the order: 9.0>7.5>6.5>3.0; showing a strong dependence of the NOR speciation, and being the anionic form of the antibiotic the more susceptible to be oxidized. Furthermore, the identification of three primary NOR by-products demonstrated that the initial attack of the active chlorine species, mainly HOCl, occurred at the secondary amine of the piperazine ring followed by chlorination of the benzene ring. The precedent findings were crucial to understand the efficiency of the technology to eliminate NOR in synthetic complex matrices such as seawater, municipal wastewater and urine. The electrochemical oxidation showed to be promissory to eliminate NOR, and its associated antimicrobial activity, in such complexes matrices. Waters at basic pH containing chloride or bicarbonate ions, such as seawater or municipal wastewater showed to be the most adapted to the application of the technology. Additionally, nitrate ions or urea, found in some matrices like fresh urine, reduce the efficiency of the process.
Asunto(s)
Antibacterianos/aislamiento & purificación , Norfloxacino/aislamiento & purificación , Aguas Residuales , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodos , Electrodos , Oxidación-ReducciónRESUMEN
Foi analisada a sensibilidade in vitro à fluorquinolona norfloxacina de 224 microrganismos isolados de 213 culturas consecutivas obtidas junto ao Laboratório de Patologia Externa da Escola Paulista de Medicina no período de agosto de 1989 a julho de 1990. Os microorganismos foram isolados de infecçöes oculares (blefarite, blefaroconjuntivite, conjuntivite, úlcera de córnea, dacriocistite, endoftalmite e meibomite), sendo submetidos ao antibiograma para norfloxacina, tobramicina, gentamicina, cefalotina e amicacina. A norfloxacina foi eficaz contra S. epidemidis, teve atividade similar à gentamicina contra espécies de Pseudomonas e Haemophilus. Sua eficácia ficou aquém da gentamicina para P. mirabilis e P.vugaris. Também näo mostrou atividade superior à cefalotina para S.aureus e S.pneumoniae