616 research outputs found
Fitting Biochars and Activated Carbons from Residues of the Olive Oil Industry as Supports of FeCatalysts for the Heterogeneous Fenton-Like Treatment of Simulated Olive Mill Wastewater
Bruno Esteves is grateful to FCT for financial support through the PhD grant
(SFRH/BD/129235/2017), with financing from National and the European Social Funds through the Human
Capital Operational Programme (POCH). Sergio Morales-Torres acknowledges the financial support from the
University of Granada (Reincorporación Plan Propio).A series of biochars and activated carbons (ACs) was prepared combining carbonization
and physical or chemical activation of cheap and abundant residues of the olive oil industry.
These materials were used as Fe-support to develop low-cost catalysts for the heterogeneous
Fenton-like oxidation of simulated olive mill wastewater (OMW), the highly pollutant effluent
generated by this agroindustry. Commercial ACs were also used as reference. All catalysts prepared
were extensively characterized and results related with their performances in the catalytic wet
peroxide oxidation (CWPO). Results showed a linear relationship of the textural properties of the
catalysts with the adsorptive and catalytic performance, as well as the preferential adsorption and
degradation of some phenolic compounds (caffeic and gallic acids) by specific interactions with the
catalysts’ surface. Despite the best performance of catalysts developed using commercial supports,
those prepared from agro-industrial residues present some advantages, including a smaller catalyst
deactivation by iron leaching. CWPO results show that catalysts from physically activated olive
stones are the most promising materials, reaching total organic carbon and toxicity reductions of
35% and 60%, respectively, as well an efficient use of H2O2, comparable with those obtained using
commercial supports. This approach showed that the optimized treatment of this type of residues
will allow their integration in the circular economic process of the olive oil production.Laboratory for Process Engineering, Environment, Biotechnology and Energy-LEPABE - FCT/MCTES (PIDDAC) - European Regional Development Funds (ERDF) through North Portugal Regional Operational Programme (NORTE 2020)
UIDB/00511/2020
NORTE-01-0247-FEDER-39789Spanish Project from ERDF/Ministry of Science, Innovation and Universities-State Research Agency
RTI2018-099224-B-I0
Nanotubos e grafeno: os primos mais jovens na família do carbono!
O carbono é o sexto elemento mais abundante do universo, encontrando-se presente tanto na forma orgânica, como em materiais inorgânicos. Além das três formas alotrópicas que ocorrem naturalmente (carbono amorfo, grafite e diamante), podem ser também sintetizadas estruturas de carbono com dimensões nanométricas. Nos últimos anos foram descobertas e caracterizadas novas e interessantes nanoestruturas de carbono, incluindo os nanotubos de carbono e o grafeno. Este breve artigo faz uma resenha sobre os métodos de síntese e caracterização destes dois materiais, aludindo a algumas das suas propriedades mais extraordinárias, bem como às suas aplicações mais recentes e de maior impacto em diversos domínios da ciência e da tecnologia, permitindo, de uma forma simples, introduzir os leitores menos familiarizados com o tema no fascinante mundo destas duas nanoestruturas de carbono
Integration of catalytic wet peroxidation and membrane distillation processes for olive mill wastewater treatment and water recovery
The degradation of organic matter present in olive mill wastewater (OMW) and the recovery of water were
studied by the integration of catalytic wet peroxidation (CWPO) and direct contact membrane distillation
(DCMD) for the first time. The oxidation step was performed in a fixed–bed reactor (FBR) working in continuous
mode (pH0 = 4.0 ± 0.2, 60 ◦C, Q = 0.75 mL/min, [H2O2]/[COD]feed = 2.3 ± 0.1 g H2O2/g O2). Samples of OMW
diluted by 5– and 7.5–fold were used (OMW–5× and OMW–7.5×, respectively), corresponding to inlet chemical
oxygen demand (COD) values of 3562 ± 68 and 2335 ± 54 mg/L, total phenolic content (TPh) of 177 ± 17 and
143 ± 7 mg GAeq/L, and total organic carbon (TOC) of 1258 ± 63 and 842 ± 45 mg/L, respectively. The FBR
was loaded with 2.0 g of a Fe–activated carbon derived–catalyst, prepared by using olive stones as the precursor,
in line with a circular economy model approach. The catalyst was selected based on the activity and stability
towards polyphenolic synthetic solutions shown in previous works of the team, while actual OMW samples were
used in this work. CWPO–treated samples of OMW allowed the operation of the DCMD unit at higher fluxes than
with the analogous untreated ones, also showing higher rejections of organic matter from the feed solution upon
DCMD, highlighting the beneficial effect of this novel configuration. Using a pre-treated sample of OMW–7.5× as
feed solution (Q = 100 mL/min, Tpermeate ≈ 18 ◦C, Tfeed ≈ 66 ◦C), the produced permeate water stream presented
several parameters well–below the legislated thresholds required for direct discharge for crops irrigation,
including total suspended solids (TSS < 10 mg/L), TPh (<0.01 mg GAeq/L), biochemical oxygen demand (BOD5
< 40 mg/L), and dissolved Fe (<0.06 mg/L). Moreover, the resulting concentrated OMW–retentate streams could
be recirculated to the FBR and maintain the same removal efficiencies obtained previously, despite the increased
initial organic loadings of the retentate after DCMD.Portuguese Foundation for Science and Technology LA/P/0045/2020
UIDB/00511/2020
UIDP/00511/2020European Regional Development Funds (ERDF) through North Portugal Regional Operational Programme (NORTE 2020) NORTE-01-0145-FEDER000069NORTE 2020 under the PORTUGAL 2020 Partnership Agreement through ERDF NORTE-01-0145-FEDER000069MCIN/AEI/FEDER "Una manera de hacer Europa" RTI2018-099224B-I00Portuguese Foundation for Science and Technology BaseUIDB/50020/2020
UIDP/50020/2020Portuguese Foundation for Science and TechnologyEuropean Commission SFRH/BD/129235/2017National and the European Social Funds through the Human Capital Operational Programme (POCH)
MCIN/AEI RYC-2019026634IEuropean Social Found (FSE) "El FSE invierte en tu futuro" RYC-2019026634
Specific adsorbents for the treatment of OMW phenolic compounds by activation of bio-residues from the olive oil industry
A series of adsorbents was developed by physical (CO2) and chemical (KOH) activation of two bio-residues: olive stones (OS) and wood from olive tree pruning (OTP). The physicochemical properties of such materials were determined and correlated with their adsorptive performance in the removal of phenolic compounds of olive mill wastewater (OMW). Adsorption isotherms and kinetics of single phenolic acids, as well as the kinetics for competitive multi-compound adsorption, were fitted by applying different models, though Langmuir and pseudosecond order models fitted better the experimental results, respectively. The intraparticle diffusion model pointed out that mesoporosity reduces the influence of phenolic compounds' restrictions in the external film diffusion of the adsorbent particle-solution interphase, but adsorption capacity linearly increases with the micropore volume accessible to N-2 at -196 degrees C (and also with BET surface area), while diffusion into ultramicropores (<0.7 nm, determined by CO2-adsorption) is slow and presents minor influence on the total adsorption capacity. After saturation, thermal regeneration of spent adsorbents allows the removal of adsorbed products, enabling the reuse of samples whilst maintaining a significant performance.Portuguese Foundation for Science and Technology UIDB/00511/2020European Regional Development Funds (ERDF) through North Portugal Regional Operational Programme (NORTE 2020) NORTE-01-0247-FEDER-39789Project "HealthyWaters -Identification, Elimination, Social Awareness and Education of Water Chemical and Biological Micropollutants with Health and Environmental Implications" - NORTE 2020, under the PORTUGAL2020 Partnership Agreement NORTE-01-0145-FEDER-000069MCIN/AEI/FEDER "Una manera de hacer Europa" RTI2018-099224-B-I00Portuguese Foundation for Science and TechnologyEuropean Commission SFRH/BD/129235/2017National Fund through the Human Capital Operational Programme (POCH)European Social Fund through the Human Capital Operational Programme (POCH)
MCIN/AEI RYC-2019-026634IEuropean Social Found (FSE) "El FSE invierte en tu futuro" RYC-2019-026634IUniversidad de Granada/CBU
Green chemistry and environmental processes
Funding Information: Acknowledgments: Portuguese FCT—Fundação para a Ciência e a Tecnologia, I.P., under the Scientific Employment Stimulus—Institutional Call (CEECINST/00102/2018) and Associate Laboratory for Green Chemistry—LAQV, financed by national funds from FCT/MCTES (UIDB/50006/2020 and UIDP/50006/2020) and the Spanish Project ref. RTI 2018-099224-B100 funded by ERDF/Ministry of Science, Innovation and Universities. S.M.-T. also acknowledges the Ramón y Cajal contract (RYC-2019-026634-I/AEI/10.13039/501100011033) from MINECO.publishersversionpublishe
Influence of Electrostatic Interactions During the Resorcinol-Formaldehyde Polymerization on the Characteristics of Mo-Doped Carbon Gels
The resorcinol (R)-formaldehyde (F) polymerization was carried out in different
experimental conditions to obtain RF/Mo doped carbon xerogels with different morphology, porosity
and nature and dispersion of metal. Attractive or repulsive electrostatic interactions were forced in the
starting aqueous solution of RF-monomers using different synthesis conditions, namely, combinations
of cationic or anionic surfactants, Mo-precursors and pH values. The results showed that when
both cationic surfactant and Mo-precursor were used at neutral pH, attractive interactions with
the anionic RF-macromolecules are favored during polymerization and the final carbon xerogel
exhibited the most developed porosity and the strongest Mo-organic phase interaction, leading to
deeper Mo-phase reduction during carbonization and the formation of highly-dispersed crystalline
nanoparticles of Mo2C. On the contrary, the use of both anionic surfactant and Mo-precursor leads
to repulsive interactions, which generates less porous carbon gels with a Mo-phase formed by
large MoO3 platelet structures and low Mo-surface contents. RF/Mo-doped gels with intermediate
properties were obtained by combining cationic and anionic surfactants, metal precursors or both.
After carbonization, the obtained materials would be suitable to be used directly as catalysts with
different physicochemical properties and active phases.Spanish Project from ERDF/Ministry of Science, Innovation and Universities-State Research Agency
RTI2018-099224-B-I0
Nanopartículas magnéticas como catalisadores no tratamento de águas utilizando o processo de foto-Fenton
O interesse nas aplicações de nanopartículas magnéticas tem crescido em quase todos os campos,
destacando-se mais recentemente a utilização de nanopartículas de óxidos de ferro para tratamento de águas. De
entre os óxidos de ferro existentes na natureza, destacam-se o a-Fe2O3, o g-Fe2O3 e o Fe3O4, que podem ser
preparados laboratorialmente por métodos de co-precipitação [1], decomposição térmica [2] e síntese hidrotérmica
[3]. As nanopartículas superparamagnéticas de óxido de ferro, também conhecidas como SPIONs -
superparamagnetic iron oxide nanoparticles, são um caso particular devido à relação entre a distribuição de
tamanhos das partículas e a carga superficial. A implementação destes materiais como catalisadores no tratamento
de águas e águas residuais pode revolucionar o conceito das tecnologias catalíticas de tratamento porque quando
estas nanopartículas, com propriedades magnéticas, são utilizadas em suspensão (i) proporcionam uma maior área
de contacto entre a fase ativa e o meio aquoso e (ii) podem ser rapidamente (e facilmente) separadas do meio
líquido por efeito de um campo magnético, ficando retidas no reator catalítico. Desta forma são ultrapassadas,
tanto a principal limitação encontrada quando são utilizados catalisadores sem propriedades magnéticas em
suspensão (difícil separação por processos de filtração), como a limitação associada à deposição de nanopartículas
em substratos fixos (típica diminuição da atividade catalítica).
Por outro lado, os compostos farmacêuticos são poluentes de maior relevância devido aos efeitos nefastos que
podem causar na saúde pública, nos ecossistemas e no ambiente em geral, onde aparecem como resultado do seu
consumo crescente e da sua difícil degradação em estações de tratamento de águas residuais. Estes compostos têm
sido encontrados em águas subterrâneas, águas de superfície e inclusivamente em águas utilizadas para consumo,
sendo esta última uma situação mais alarmante. Em particular, a difenidramina constituí o princípio ativo de
diversos produtos farmacêutico, como o Benadryl®, e é classificada como anti-histamínico de primeira geração
para formulações farmacêuticas utilizadas no tratamento de rinite, conjuntivite, insónia, picadas de insetos,
enjoos/ansiedade, entre outros. Aparece nas águas devido à sua baixa biodegradabilidade e tem demonstrado
efeitos tóxicos, cancerígenos e mutagénicos [4]. Por este motivo, no presente trabalho, foram preparados e
caracterizados materiais à base de óxido de ferro com propriedades magnéticas para serem testados na degradação
de difenidramina pelo processo de foto-Fenton, onde é utilizada uma mistura catalítica fortemente oxidante de um
agente contendo ferro e peróxido de hidrogénio (H2O2)
Photodegradation of cytostatic drugs by g-C3N4: Synthesis, properties and performance fitted by selecting the appropriate precursor
Graphitic carbon nitride (g-C3N4) was synthetized by a one-step thermal method from different N-rich precursors,
namely melamine, dicyandiamide, urea, thiourea and cyanamide. The structure, optical and physicochemical
properties of g-C3N4 materials were studied by transmission electron microscopy (TEM), X-ray
photoelectron spectroscopy (XPS) and Raman spectroscopy, among others. Both melamine and dicyandiamide
provided a less porous structure composed by large flake sheets, whereas urea and thiourea favoured g-C3N4
composed by small flat sheets and wrinkles with a larger porosity. The establishment of more condensed g-C3N4
networks with a reduced band gap was also evidenced for melamine and dicyandiamide precursors, while urea
favoured less condensed melem or melon structures. The photoactivity of the different g-C3N4 was assessed for
the removal of an aqueous solution containing 5-fluorouracil (5-FU), cyclophosphamide (CP) or a mixture of both
cytostatic drugs, under near UV-Vis and solar-LED irradiations. The best performing photocatalysts under near
UV-Vis irradiation, were those prepared from melamine (kapp = 14.6 × 10–2 min–1 for 5-FU) and thiourea (kapp =
2.5 × 10–2 min–1 for CP), while urea was the most active under solar-LED irradiation (kapp = 0.183 × 10–2 min–1
for 5-FU). In addition, CP was more resistant to be degraded than 5-FU, and a competitive effect for the generated
hydroxyl radicals was evidenced when both pollutant molecules were in the same solution. The photoactivity of
g-C3N4 materials was justified by the combination of various effects: (i) surface area, (ii) well-connected and
condensed g-C3N4 structures and (iii) high surface C/N ratios with nitrogen vacanciesSpanish Projects from MCIN/AEI/FEDER "Una manera de hacer Europa" RTI2018-099224-B-I00FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades B-RNM-486-UGR20Junta de Andalucia-Consejeria de Universidad, Investigacion e Innovacion -Proyecto P21_00208MICIN/AEIEuropean Social Found (FSE) PRE2019-087946MICIN/AEI RYC-2019-026634-IFSE "El FSE invierte en tu futuro"Universidad de Granada/CBU
Functionalized Graphene Derivatives and TiO2 for High Visible Light Photodegradation of Azo Dyes
Functionalized graphene derivatives including graphene oxide (GO), reduced graphene
oxide (rGO), and heteroatom (nitrogen/sulphur (N/S) or boron (B))-doped graphene were used to
synthesize composites with TiO2 (T). The photocatalytic performance of composites was assessed
for the degradation of Orange G dye (OG) under simulated solar light. All the prepared graphene
derivatives—TiO2 composites showed better photocatalytic performance than bare TiO2. A higher
photocatalytic activity was found for the composites containing GO and N/S co-doped rGO
(kapp = 109.2 × 10−3 and 48.4 × 10−3 min−1
, for GO-T and rGONS-T, respectively). The influence of
both initial solution pH and the reactive species involved in the OG degradation pathway were
studied. The photocatalytic activity of the samples decreased with the increase of the initial pH
(from 3.0 to 10.0) due to the occurrence of electrostatic repulsive forces between the photocatalysts
surface and the molecules of OG, both negatively charged. The use of selective scavengers showed
that although the photogenerated holes dominate the degradation mechanism, radicals and singlet
oxygen also participate in the OG degradation pathway. In addition, reutilization experiments
indicated that the samples were stable under the reaction conditions used.ERDF/Ministry of Science, Innovation and Universities-State Research Agency
RTI2018-099224-B-I0
Coupling Noble Metals and Carbon Supports in the Development of Combustion Catalysts for the Abatement of BTX Compounds in Air Streams
The catalytic combustion of volatile organic compounds (VOCs) is one of the most important techniques to remove these pollutants from the air stream, but it should be carried out at the lowest possible temperature, saving energy and avoiding the simultaneous formation of nitrogen oxides (NOx). Under these experimental conditions, the chemisorption of water generated from VOCs combustion may inhibit hydrophilic catalysts. Nowadays, a wide variety of carbon materials is available to be used in catalysis. The behavior of these hydrophobic materials in the development of highly active and selective combustion catalysts is analyzed in this manuscript. The support characteristics (porosity, hydrophobicity, structure, surface chemistry, etc.) and the active phase nature (noble metals: Pt, Pd) and dispersion were analyzed by several techniques and the results correlated with the dual adsorptive and/or catalytic performance of the corresponding catalysts. The coupling of highly active phases and carbon materials (activated carbons, honeycomb coated monoliths, carbon aerogels, etc.) with tuneable physicochemical properties leads to the complete abatement of benzene, toluene and xylenes (BTX) from dilute air streams, being selectively oxidized to CO2 at low temperatures
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