Adsorção de diclofenaco sódico por óxido de grafeno, carvão ativado pulverizado e granulado
Recent studies developed in different countries reveal the presence of pharmaceuticals drugs in aquatic bodies. Among the main drugs detected, the antiinflammatory sodium diclofenac (SD) is considered to be of high ecotoxicity and was included in the list of priority substances for monitoring in the...
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| Format: | masterThesis |
| Language: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Online Access: | https://repositorio.ufrn.br/handle/123456789/45147 |
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| Summary: | Recent studies developed in different countries reveal the presence of
pharmaceuticals drugs in aquatic bodies. Among the main drugs detected, the antiinflammatory sodium diclofenac (SD) is considered to be of high ecotoxicity and was
included in the list of priority substances for monitoring in the field of water policy by
Directive 39/2013 of the European Union. Among the available water treatment
processes, an adsorption is an effective alternative from the technical and economic
aspects. In this context, this work aimed to evaluate, on a bench scale, the efficiency
of SD removal in three different adsorbents: graphene oxide (GO), pulverized activated
carbon (PAC) and granulated activated carbon (GAC). SD adsorption was analyzed
through the central composite design (CCD), using four factors: concentration of
sodium diclofenac (CSD), adsorbent concentration (ADSC), contact time (Ct) and pH.
The results supported the modeling of responses for adsorption capacity, adsorbate
removal, adsorption kinetics of pseudo-first order, pseudo-second order (PSO) and
intra-particle diffusion (IPD), Langmuir and Freundlich isotherms. In general, the three
adsorbents showed affinity for SD adsorption. The maximum experimental adsorption
capacities were: 669.50 mg.g-1 for GO (CSD of 450 mg.L-1, ADSC of 0.2 g.L-1, Ct of 34.3
min and pH 5); 169.39 mg.g-1 for PAC (CSD of 331.64 mg.L-1, ADSC of 0.2 g.L-1, Ct of
40.6 min and pH of 5); 77.73 mg.g-1 for GAC (CSD of 450 mg.L-1, ADSC of 0.2 g.L-1, Ct
of 25 min and pH of 9). The efficiency of the GO overlaps by 395% to the PAC and
861% to the GAC. These data were obtained in confirmation batches in duplicate and
represent the average of the values obtained. The data from the CCD-based models
showed estimates of average removal efficiencies that corroborate the preference of
the GO over the tested carbons. For all conditions applied (CSD from 50 to 450 mg.L-1,
ADSC from 1.4 to 5 g.L-1, Ct from 5 to 45 min and pH from 5 to 9), the removal of SD
by GO varied between 97.59% to 99.95%. The PAC obtained maximum removal
foreseen by the model of up to 100%, but limited to CSD between 50 and 150 mg.L-1.
For the GAC, the maximum removal expected was 43.50% for CSD of 50 mg.L-1. For
all adsorbents, the PSO kinetics showed a better fit to the data. The IPD model
indicated that the adsorption processes were controlled by the combination of intrafilm and intra-pore mechanisms, with GO being primarily associated with the intra-film
and the carbons with the intra-pore. The isotherms of the GO and GAC adapted to the
Freundlich model and the PAC to that of Langmuir. SD adsorption by GO was
characterized by chemisorption, while PAC and GAC by physisorption. In conclusion,
the GO proved to be an efficient material and an alternative for removing SD, and
aspects of the costs involved should be evaluated in the future. |
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