| Summary: | Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-03-31T23:01:39Z
No. of bitstreams: 1
GislanePinhoDeOliveira_DISSERT.pdf: 2585969 bytes, checksum: 5a2ec44dfa4024c61a2f9bad2b0cc474 (MD5) === Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-04-04T22:09:35Z (GMT) No. of bitstreams: 1
GislanePinhoDeOliveira_DISSERT.pdf: 2585969 bytes, checksum: 5a2ec44dfa4024c61a2f9bad2b0cc474 (MD5) === Made available in DSpace on 2016-04-04T22:09:35Z (GMT). No. of bitstreams: 1
GislanePinhoDeOliveira_DISSERT.pdf: 2585969 bytes, checksum: 5a2ec44dfa4024c61a2f9bad2b0cc474 (MD5)
Previous issue date: 2015-06-25 === Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES === O progresso industrial moderno vem incorporando compostos fen?licos entre as
impurezas encontradas na ?gua. Por se tratar de uma subst?ncia t?xica e cancer?gena, ?
imprescind?vel que a mesma seja reduzida ? concentra??es toler?veis, determinadas pelo
CONAMA. Neste contexto, este trabalho tem como objetivo o tratamento e caracteriza??o de
catalisadores oriundos do biocarv?o, subproduto da pir?lise de biomassa (avel?s e p? de
madeira), assim como sua avalia??o na degrada??o fotocatal?tica do fenol. Os ensaios foram
realizados em um reator leito de lama, com medi??es instant?neas da temperatura, pH e
oxig?nio dissolvido. Os experimentos foram realizados nas seguintes condi??es operacionais:
temperatura igual a 50 ?C, vaz?o de oxig?nio igual a 410 mL min-1
, volume de solu??o reagente
igual a 3,2 L, l?mpada UV de 400 W, press?o de 1 atm e tempo de rea??o de 2 horas. Os
par?metros avaliados foram o pH do meio reacional (3,0; 6,9 e 10,7), concentra??o inicial de
fenol comercial (250, 500 e 1000 ppm), concentra??o de catalisador (0, 1, 2 e 3 g L-1
) e natureza
do catalisador (carv?o do aveloz ativado e lavado com diclorometano, CAADCM, e carv?o da
madeira ativado e lavado com diclorometano, CMADCM). Os resultados de FRX, DRX e BET
comprovaram a presen?a de ferro e pot?ssio em quantidades satisfat?rias para o catalisador
CAADCM e em quantidades reduzidas no catalisador CMADCM, e o aumento da ?rea
superficial dos materiais ap?s a ativa??o qu?mica e f?sica. As curvas de degrada??o do fenol
indicam que o pH tem uma influ?ncia significativa na convers?o do fenol, apresentando
melhores resultados para os valores de pH mais reduzidos. A concentra??o ?tima de catalisador
observada foi de 1 g L-1
e o aumento da concentra??o inicial de fenol exerce uma influ?ncia
negativa na condu??o da rea??o. Tamb?m foi observado o efeito positivo da presen?a de ferro
e pot?ssio na estrutura do catalisador: obteve-se convers?es melhores para os ensaios realizados
com o catalisador CAADCM, quando comparado com o catalisador CMADCM nas mesmas
condi??es. A maior convers?o foi obtida para o ensaio realizado em pH ?cido (3,0), com uma
concentra??o inicial de fenol igual a 250 ppm na presen?a do catalisador CAADCM a 1 g L-1
.
As amostras l?quidas retiradas a cada 15 minutos foram analisadas por cromatografia l?quida
identificando e quantificando a hidroquinona, p-benzoquinona, catecol e ?cido maleico.
Finalmente um mecanismo do processo reacional foi proposto, considerando que o fenol ?
transformado em fase homog?nea e os demais reagem na superf?cie do catalisador. Aplicandose
o modelo de Langmuir-Hinshelwood juntamente com um balan?o de massa, obteve-se um
sistema de equa??es diferenciais que foi resolvido utilizando o m?todo de Runge-Kutta de 4?
ordem associado a uma rotina de otimiza??o SWARM (enxame de part?culas), visando
minimizar a fun??o objetivo de m?nimos quadrados para estima??o dos par?metros cin?ticos e
de adsor??o. Obteve-se constantes cin?ticas da ordem de grandeza de 10-3
para a degrada??o do
fenol, 10-4
? 10-2
para a forma??o de ?cidos, 10-6
? 10-9
para a mineraliza??o dos quin?nicos
(hidroquinona, p-benzoquinona e catecol), 10-3
? 102 para a mineraliza??o dos ?cidos. === The modern industrial progress has been contaminating water with phenolic
compounds. These are toxic and carcinogenic substances and it is essential to reduce its
concentration in water to a tolerable one, determined by CONAMA, in order to protect the
living organisms. In this context, this work focuses on the treatment and characterization of
catalysts derived from the bio-coal, by-product of biomass pyrolysis (avel?s and wood dust) as
well as its evaluation in the phenol photocatalytic degradation reaction. Assays were carried out
in a slurry bed reactor, which enables instantaneous measurements of temperature, pH and
dissolved oxygen. The experiments were performed in the following operating conditions:
temperature of 50 ?C, oxygen flow equals to 410 mL min-1
, volume of reagent solution equals
to 3.2 L, 400 W UV lamp, at 1 atm pressure, with a 2 hours run. The parameters evaluated were
the pH (3.0, 6.9 and 10.7), initial concentration of commercial phenol (250, 500 and 1000 ppm),
catalyst concentration (0, 1, 2, and 3 g L-1
), nature of the catalyst (activated avel?s carbon
washed with dichloromethane, CAADCM, and CMADCM, activated dust wood carbon washed
with dichloromethane). The results of XRF, XRD and BET confirmed the presence of iron and
potassium in satisfactory amounts to the CAADCM catalyst and on a reduced amount to
CMADCM catalyst, and also the surface area increase of the materials after a chemical and
physical activation. The phenol degradation curves indicate that pH has a significant effect on
the phenol conversion, showing better results for lowers pH. The optimum concentration of
catalyst is observed equals to 1 g L-1
, and the increase of the initial phenol concentration exerts
a negative influence in the reaction execution. It was also observed positive effect of the
presence of iron and potassium in the catalyst structure: betters conversions were observed for
tests conducted with the catalyst CAADCM compared to CMADCM catalyst under the same
conditions. The higher conversion was achieved for the test carried out at acid pH (3.0) with an
initial concentration of phenol at 250 ppm catalyst in the presence of CAADCM at 1 g L-1
. The
liquid samples taken every 15 minutes were analyzed by liquid chromatography identifying and
quantifying hydroquinone, p-benzoquinone, catechol and maleic acid. Finally, a reaction
mechanism is proposed, cogitating the phenol is transformed into the homogeneous phase and
the others react on the catalyst surface. Applying the model of Langmuir-Hinshelwood along
with a mass balance it was obtained a system of differential equations that were solved using
the Runge-Kutta 4th order method associated with a optimization routine called SWARM
(particle swarm) aiming to minimize the least square objective function for obtaining the
kinetic and adsorption parameters. Related to the kinetic rate constant, it was obtained a
magnitude of 10-3
for the phenol degradation, 10-4
to 10-2
for forming the acids, 10-6
to 10-9
for
the mineralization of quinones (hydroquinone, p-benzoquinone and catechol), 10-3
to 10-2
for
the mineralization of acids.
|
|---|
