Aplicação e otimização de métodos eletroquímicos combinados para remoção e determinação de cromo hexavalente em efluentes simulados
Hexavalent chromium is a heavy metal present in various industrial effluents, and depending on its concentration may cause irreparable damage to the environment and to humans. Facing this surrounding context, this study aimed on the application of electrochemical methods to determine and remove t...
Na minha lista:
| Autor principal: | |
|---|---|
| Outros Autores: | |
| Formato: | doctoralThesis |
| Idioma: | por |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
|
| Assuntos: | |
| Acesso em linha: | https://repositorio.ufrn.br/jspui/handle/123456789/20754 |
| Tags: |
Adicionar Tag
Sem tags, seja o primeiro a adicionar uma tag!
|
| Resumo: | Hexavalent chromium is a heavy metal present in various industrial effluents, and
depending on its concentration may cause irreparable damage to the environment
and to humans. Facing this surrounding context, this study aimed on the application
of electrochemical methods to determine and remove the hexavalent chromium (Cr6+)
in simulated wastewater. To determine was applied to cathodic stripping voltammetry
(CSV) using ultra trace graphite electrodes ultra trace (work), Ag/AgCl (reference)
and platinum (counter electrode), the samples were complexed with 1,5-
diphenylcarbazide and then subjected to analysis. The removal of Cr6+ was applied
electrocoagulation process (EC) using Fe and Al electrodes. The variables that
constituted the factorial design 24, applied to optimizing the EC process, were:
current density (5 and 10 mA.cm-2), temperature (25 and 60 ºC), concentration (50
and 100 ppm) and agitation rate (400 and 600 RPM). Through the preliminary test it
was possible the adequacy of applying the CSV for determining of Cr6+, removed
during the EC process. The Fe and Al electrodes as anodes sacrifice showed
satisfactory results in the EC process, however Fe favored complete removal in 30
min, whereas with Al occurred at 240 min. In the application of factorial design 24 and
analysis of Response Surface Methodology was possible to optimize the EC process
for removal of Cr6+ in H2SO4 solution (0.5 mol.L-1), in which the temperature, with
positive effect, was the variable that presented higher statistical significance
compared with other variables and interactions, while in optimizing the EC process
for removal of Cr6+ in NaCl solution (0.1 mol.L-1) the current density, with positive
effect, and concentration, with a negative effect were the variables that had greater
statistical significance with greater statistical significance compared with other
variables and interactions. The utilization of electrolytes supports NaCl and Na2SO4
showed no significant differences, however NaCl resulted in rapid improvement in
Cr6+ removal kinetics and increasing the NaCl concentration provided an increase in
conductivity of the solution, resulting in lower energy consumption. The wear of the
electrodes evaluated in all the process of EC showed that the Al in H2SO4 solution
(0.5 mol.L-1), undergoes during the process of anodization CE, then the experimental
mass loss is less than the theoretical mass loss, however, the Fe in the same
medium showed a loss of mass greater experimental estimated theoretically. This
fact is due to a spontaneous reaction of Fe with H2SO4, and when the reaction
medium was the NaCl and Na2SO4 loss experimental mass approached the
theoretical mass loss. Furthermore, it was observed the energy consumption of all
processes involved in this study had a low operating cost, thus enabling the
application of the EC process for treating industrial effluents. The results were
satisfactory, it was achieved complete removal of Cr6+ in all processes used in this
study. |
|---|