Tuning, mechanistic routes and performance amplification of microwave-responsive iron/copper carbonaceous heterostructures in the degradation of pharmaceutical substances
Fecha
2024-02-22Primeiro coorientador
Zanella, Renato
Primeiro membro da banca
Pinto, Luiz Antonio de Almeida
Segundo membro da banca
Badawi, Michael
Terceiro membro da banca
Köhler, Mateus Henrique
Quarto membro da banca
Mello, Paola de Azevedo
Metadatos
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The occurrence of pharmaceuticals as pollutants of many ecosystems worldwide has
escalated of the years, especially due to increased use of these substances and the fact that
water and wastewater treatment plants were not developed to remove them. In this
context, the use of microwave (MW) as an energy source for environmental catalysis has
gained research interest due to its ability to provide both thermal and non-thermal effects
that result in shorter reaction times, synergistic effects and high mineralization rates. The
challenge, however, is to develop versatile materials with high MW absorption properties,
capable of generating hot spots and reactive oxygen species simultaneously. In this work,
we started by investigating wastewater samples that pointed to high values (mg L-1
) of
16 substances, indicating a possible direct disposal of expired pharmaceuticals into the
urban sewer system. The viability of using MW technology was tested by employing a
reaction catalyzed by Fe0
, achieving total mineralization of 1212.2 ± 0.2 mg L-1
of total
organic carbon (TOC) after 60 min. In order to optimize these results, two
heterostructures were produced by assembling chalcopyrite (CuFeS2) to carbonaceous
structures and intensively tested for the efficient degradation of diclofenac (DCF),
ibuprofen (IBP), naproxen (NPX), acetaminophen (ACT) and ketoprofen (KTP). The first
catalyst produced consisted of CuFeS2 assembled to activated carbon (AC), being named
ACFS. The catalyst reached total mineralization of IBP, KTP and DCF at 30 min under
a MW power of 598 W with less than 2% of Fe and Cu leaching after 10 cyclic reuses.
The degradation mechanisms of IBP, KTP and DCF pointed that ACFS was able to
promote oxidative and reductive catalytic routes, where surface phenomena between the
CuFeS2 particles and the AC structure contributed to effective charge transfer and balance
as •OH species was generated. As it was then known that surface phenomena can heavily
impact on the stability of the heterostructure, the second catalyst was developed using
multi-walled carbon nanotubes (MWCNTs) as support, being named MWCNT/CPT. Due
to its ordered structure, MWCNT/CPT catalyst was stable during 20 cyclic reuses, where
a 50% decrease of its kinetic rate was observed but full mineralization of ACT and NPX
was still reached. The MWCNT/CPT presented remarkable results, providing total
mineralization of the two compounds studied after only 16 min. Again, the degradation
mechanisms pointed a high contribution of the surface to charge transfer phenomena,
being observed two different mechanisms for molecular degradation and for TOC
removal. Thus, this work provides valuable information on how the surface of a catalyst
can heavily weigh in the catalytic efficiency under MW irradiation, proving that high
performance can be achieved by the fine tuning between morphological and synergistic
parameters.
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