Florica Papa
@icf.ro
Surface Chemistry and Catalysis / "Ilie Murgulescu" Institute of Physical Chemistry of Romanian Academy
"Ilie Murgulescu" Institute of Physical Chemistry of Romanian Academy
RESEARCH, TEACHING, or OTHER INTERESTS
Chemistry, Catalysis, Process Chemistry and Technology, Inorganic Chemistry
Scopus Publications
Scopus Publications
Gianina Dobrescu, Ramona Georgescu-State, Florica Papa, Jacobus (Koos) Frederick van Staden, and Razvan Nicolae State
MDPI AG
The fractal properties of carbon paste electrodes (CPEs) and carbon paste electrodes modified with ionic liquid (IL), AuTiO2/graphene oxide, and IL/AuTiO2/graphene oxide were investigated using scanning electron microscopy (SEM), and cyclic voltammetry (CV). The impact of fractal dimensions and self-similarity ranges on electrochemical responses was underlined. It was proved that a higher fractal dimension and a broad self-similarity domain lead to a higher electrochemical response. Results indicated that IL/AuTiO2/graphene oxide composite-modified CPEs are a great candidate to be used as electrochemical sensors, with a high fractal dimension and large self-similarity domain.
Gabriela Petcu, Elena Maria Anghel, Irina Atkinson, Daniela C. Culita, Nicoleta G. Apostol, Andrei Kuncser, Florica Papa, Adriana Baran, Jean-Luc Blin, and Viorica Parvulescu
MDPI AG
Ti-aluminosilicate gels were used as supports for the immobilization of Fe, Co, and Ni oxides (5%) by impregnation and synthesis of efficient photocatalysts for the degradation of β-lactam antibiotics from water. Titanium oxide (1 and 2%) was incorporated into the zeolite network by modifying the gel during the zeolitization process. The formation of the zeolite Y structure and its microporous structure were evidenced by X-ray diffraction and N2 physisorption. The structure, composition, reduction, and optical properties were studied by X-ray diffraction, H2-TPR, XPS, Raman, photoluminescence, and UV–Vis spectroscopy. The obtained results indicated a zeolite Y structure for all photocatalysts with tetracoordinated Ti4+ sites. The second transitional metals supported by the post-synthesis method were obtained in various forms, such as oxides and/or in the metallic state. A red shift of the absorption edge was observed in the UV–Vis spectra of photocatalysts upon the addition of Fe, Co, or Ni species. The photocatalytic performances were evaluated for the degradation of cefuroxime in water under visible light irradiation. The best results were obtained for iron-immobilized photocatalysts. Scavenger experiments explained the photocatalytic results and their mechanisms. A different contribution of the active species to the photocatalytic reactions was evidenced.
Gabriela Petcu, Florica Papa, Irina Atkinson, Adriana Baran, Nicoleta G. Apostol, Simona Petrescu, Lionel Richaudeau, Jean-Luc Blin, and Viorica Parvulescu
MDPI AG
Zeolite Y samples with microporous and hierarchical structures containing Ti–Ni and Ti–Co oxides were obtained as active photocatalysts. Different Ti amounts (5, 10% TiO2) were supported, followed by the loading of Ni or Co oxides (5%). X-ray diffraction evidenced the presence of TiO2 as an anatase. N2 adsorption–desorption results showed type IV isotherms for hierarchical zeolite Y samples, and a combination of type IV and I isotherms for zeolite Y samples. UV–Vis diffuse reflectance spectra showed a shift in the absorption band to visible with increasing Ti loading and especially after Co and Ni addition. A significant effect of the support was evidenced for Ti and its interaction with Co/Ni species. The zeolite Y support stabilized Ti in the 4+ oxidation state while hierarchical zeolite Y support favored the formation of Ti3+ species, Ni0 and Ni2+ and the oxidation of Co to 3+ oxidation state. Photocatalytic activity, under UV and visible light irradiation, was evaluated by the degradation of amoxicillin, used as a model test. The photocatalytic mechanism was investigated using ethanol, p-benzoquinone and KI as ·OH and ·O2− radicals and hole (h+) scavengers. The best results were obtained for the immobilized Ni-Ti species on the hierarchical zeolite Y support.
Gabriela Petcu, Florica Papa, Elena Maria Anghel, Irina Atkinson, Silviu Preda, Simona Somacescu, Daniela C. Culita, Adriana Baran, Elena Madalina Ciobanu, Luiza Maria Jecu,et al.
MDPI AG
The present work reports the synthesis of efficient Ti–Au/zeolite Y photocatalysts by different processing of aluminosilicate gel and studies the effect of titania content on the structural, morphological, textural, and optical properties of the materials. The best characteristics of zeolite Y were obtained by aging the synthesis gel in static conditions and mixing the precursors under magnetic stirring. Titania (5, 10, 20%) and gold (1%) species were incorporated in zeolite Y support by the post-synthesis method. The samples were characterized by X-ray diffraction, N2-physisorption, SEM, Raman, UV–Vis and photoluminescence spectroscopy, XPS, H2-TPR, and CO2-TPD. The photocatalyst with the lowest TiO2 loading shows only metallic Au on the outermost surface layer, while a higher content favors the formation of additional species such as: cluster type Au, Au1+, and Au3+. A high TiO2 content contributes to increasing the lifetime of photogenerated charge careers, and the adsorption capacity of the pollutant. Therefore, an increase in the photocatalytic performances (evaluated in degradation of amoxicillin in water under UV and visible light) was evidenced with the titania content. The effect is more significant in visible light due to the surface plasmon resonance (SPR) effect of gold interacting with the supported titania.
Mihaela Filip, Elena Maria Anghel, Vasile Rednic, Florica Papa, Simona Somacescu, Cornel Munteanu, Nicolae Aldea, Jing Zhang, and Viorica Parvulescu
MDPI AG
The control of catalytic performance using synthesis conditions is one of the main goals of catalytic research. Two series of Pt-Ti/SBA-15 catalysts with different TiO2 percentages (n = 1, 5, 10, 30 wt.%) were obtained from tetrabutylorthotitanate (TBOT) and peroxotitanate (PT), as titania precursors and Pt impregnation. The obtained catalysts were characterized using X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), N2 sorption, Raman, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), hydrogen temperature-programmed reduction (H2-TPR) and H2-chemisorption measurements. Raman spectroscopy showed framework titanium species in low TiO2 loading samples. The anatase phase was evidenced for samples with higher titania loading, obtained from TBOT, and a mixture of rutile and anatase for those synthesized by PT. The rutile phase prevails in rich TiO2 catalysts obtained from PT. Variable concentrations of Pt0 as a result of the stronger interaction of PtO with anatase and the weaker interaction with rutile were depicted using XPS. TiO2 loading and precursors influenced the concentration of Pt species, while the effect on Pt nanoparticles’ size and uniform distribution on support was insignificant. The Pt/PtO ratio and their concentration on the surface were the result of strong metal–support interaction, and this influenced catalytic performance in the complete oxidation of methane at a low temperature. The highest conversion was obtained for sample prepared from PT with 30% TiO2.
Alexandru-Tudor Toderaşc, Irina Atkinson, Daniela Cristina Culiţă, Paul Emil Mereuţă, Florica Papa, Adriana Urdă, and Ioan-Cezar Marcu
Elsevier BV
Gianina Dobrescu, Florica Papa, Daniela Culita, Ioan Balint, and Niculae I. Ionescu
MDPI AG
The close link between the roughness of a surface and its adsorptive properties in Cerofolini’s model yields, with an adequate choice of adsorption energy, the well-known Dubinin-Radushkevich or Freundlich adsorption isotherms. Assuming fractal behavior concerning both energetic and geometric surface heterogeneities described by the power-law expressions and fractal dimensions, the paper will develop some fractal adsorption isotherms. Using our theoretical approach, fractal isotherms will provide insights not only into the fractal behavior of the surface geometry but also into the fractal energetic heterogeneities, implying that a sorbent does not need to be porous to apply a fractal isotherm: adsorption on “flat” surfaces can also be described by fractal isotherms and fractal dimensions related to energetic disorders. For example, the theory will be applied to computing the energetic fractal dimensions of some nanoparticle catalysts, Rh/Al2O3, Rh/TiO2, and Rh/WO3.
Monica Pavel, Crina Anastasescu, Razvan-Nicolae State, Anca Vasile, Florica Papa, and Ioan Balint
MDPI AG
It is well-documented that large-scale pollution generated by human activity has a dramatic impact on ecosystems. In this context, removing harmful chemicals via photocatalysis has tremendous potential as a depollution method, utilizing freely available solar light and catalytic materials with low or negligible ecotoxicity. The main drawbacks, which aren’t often addressed in the available literature, are the formation of harmful intermediate products, low reaction rates, limited catalyst stability, and difficult catalyst recovery. In most cases, published works assess the efficiency of tested photocatalysts from pollutant degradation studies, whereas identifying and quantifying by-products is not often conducted. This review summarizes the recent advances reported for the photocatalytic removal of some organic (e.g., alcohols, carboxylic acids, volatile organic compounds, phenol) and inorganic (e.g., NO3−) contaminants. The efficiency of various UV- and visible-light active photocatalysts and the reaction degradation pathways were explained, emphasizing the main factors contributing to their mineralization. The reaction mechanisms, the identification and quantification of degradation intermediates, and the implication of reactive active species (ROS) were discussed and analyzed for each category of model target pollutant. Additionally, the actual challenges and future photocatalytic approaches to improve environmental remediation were presented.
Marius C. Stoian, Cosmin Romaniţan, Gabriel Crăciun, Daniela C. Culiţă, Florica Papa, Mihaela Badea, Cătălin Negrilă, Ionel Popescu, and Ioan-Cezar Marcu
Elsevier BV
Florica Papa, Anca Vasile, and Gianina Dobrescu
MDPI AG
Changing the composition and structure of a catalyst to obtain a positive impact on its performance is challenging [...]
Monica Raciulete, Crina Anastasescu, Florica Papa, Irina Atkinson, Corina Bradu, Catalin Negrila, Diana-Ioana Eftemie, Daniela C. Culita, Akane Miyazaki, Veronica Bratan,et al.
MDPI AG
A multi-step ion-exchange methodology was developed for the fabrication of Cu(LaTa2O7)2 lamellar architectures capable of wastewater depollution. The (001) diffraction line of RbLaTa2O7 depended on the guest species hosted by the starting material. SEM and TEM images confirmed the well-preserved lamellar structure for all intercalated layered perovskites. The UV–Vis, XPS, and photocurrent spectroscopies proved that Cu intercalation induces a red-shift band gap compared to the perovskite host. Moreover, the UV–Vis spectroscopy elucidated the copper ions environment in the Cu-modified layered perovskites. H2-TPR results confirmed that Cu species located on the surface are reduced at a lower temperature while those from the interlayer occur at higher temperature ranges. The photocatalytic degradation of phenol under simulated solar irradiation was used as a model reaction to assess the performances of the studied catalysts. Increased photocatalytic activity was observed for Cu-modified layered perovskites compared to RbLaTa2O7 pristine. This behavior resulted from the efficient separation of photogenerated charge carriers and light absorption induced by copper spacer insertion.
Ramona Georgescu State, Jacobus (Koos) Frederick van Staden, Razvan Nicolae State, and Florica Papa
Elsevier BV
Silviu Preda, Polona Umek, Maria Zaharescu, Crina Anastasescu, Simona Viorica Petrescu, Cătălina Gîfu, Diana-Ioana Eftemie, Razvan State, Florica Papa, and Ioan Balint
MDPI AG
Sodium titanate nanorods were synthesized by a hydrothermal method and subsequently modified with an iron precursor. For comparison, Fe2O3 nanocubes were also obtained through a similar hydrothermal treatment. Pristine, Fe-modified nanorods and Fe2O3 nanocubes were suspended in diluted ammonia solutions (20 ppm) and exposed to ozone and simulated light irradiation. Ammonia abatement, together with the resulting nitrogen-containing products (NO3−), was monitored by ion chromatography measurements. The generation of reactive oxygen species (·OH and O2−) in the investigated materials and their photoelectrochemical behaviour were also investigated. Morphological and structural characterizations (SEM, XRD, XRF, UV–Vis, H2-TPR, NH3-TPD, PL, PZC) of the studied catalysts were correlated with their activity for ammonia degradation with ozone- and photo-assisted oxidation. An increase in ammonia conversion and a decreasing amount of NO3− were achieved by combining the above-mentioned processes.
Anca Vasile, Florica Papa, Veronica Bratan, Cornel Munteanu, Mircea Teodorescu, Irina Atkinson, Mihai Anastasescu, Daisuke Kawamoto, Catalin Negrila, Cristian D. Ene,et al.
Elsevier BV
Cristina Silvia Stoicescu, Dana Culita, Nicolae Stanica, Florica Papa, Razvan Nicolae State, and Gabriel Munteanu
Elsevier BV
Gianina Dobrescu, Florica Papa, Razvan State, Monica Raciulete, Daniela Berger, Ioan Balint, and Niculae I. Ionescu
MDPI AG
Obtaining high-area catalysts is in demand in heterogeneous catalysis as it influences the ratio between the number of active surface sites and the number of total surface sites of the catalysts. From this point of view, fractal theory seems to be a suitable instrument to characterize catalysts’ surfaces. Moreover, catalysts with higher fractal dimensions will perform better in catalytic reactions. Modifying catalysts to increase their fractal dimension is a constant concern in heterogeneous catalysis. In this paper, scientific results related to oxide catalysts, such as lanthanum cobaltites and ferrites with perovskite structure, and nanoparticle catalysts (such as Pt, Rh, Pt-Cu, etc.) will be reviewed, emphasizing their fractal properties and the influence of their modification on both fractal and catalytic properties. Some of the methods used to compute the fractal dimension of the catalysts (micrograph fractal analysis and the adsorption isotherm method) and the computed fractal dimensions will be presented and discussed.
Madalina Ciobanu, Gabriela Petcu, Elena M. Anghel, Florica Papa, Nicoleta G. Apostol, Daniela C. Culita, Irina Atkinson, Silviya Todorova, Maya Shopska, Anton Naydenov,et al.
Elsevier BV
Ştefan-Bogdan Ivan, Ioana Fechete, Florica Papa, and Ioan-Cezar Marcu
Elsevier BV
Alexandra Sandulescu, Crina Anastasescu, Florica Papa, Monica Raciulete, Anca Vasile, Tanta Spataru, Monica Scarisoreanu, Claudiu Fleaca, Cristian N. Mihailescu, Valentin S. Teodorescu,et al.
MDPI AG
The specific roles played by both support and noble metals in light absorption, charge separation, and the formation of ·OH and O2− (ROS) are analyzed for light-triggered oxidation of phenol (Ph) over pristine and over noble metal (Ag, Au, Pt) -loaded TiO2. Experiments show that the supported noble metals act as a light visible absorber, assist the separation of photo-charges and reduction of O2 to O2−. The O2− oxidizes mildly Ph to oxygenated products (hydroquinone, benzoquinone, and 1,2-dihydroxibenzene). In a parallel process, ·OH radicals, yielded by TiO2, mineralize Ph to CO2 by fast reaction sequences. Radical quenching and photo electrochemical measurements (surface photovoltage) confirm independently that the production of ·OH and O2− scale with oxidative conversion of Ph. The selectivity to CO2 and mild oxidation products is the result of the interplay between catalyst activity for ·OH and for O2− production.
Marius-Alexandru Mihai, Daniela Cristina Culita, Irina Atkinson, Florica Papa, Ionel Popescu, and Ioan-Cezar Marcu
Elsevier BV
Monica Raciulete, Florica Papa, Catalin Negrila, Veronica Bratan, Cornel Munteanu, Jeanina Pandele-Cusu, Daniela C. Culita, Irina Atkinson, and Ioan Balint
MDPI AG
We have explored an efficient strategy to enhance the overall photocatalytic performances of layered perovskites by increasing the density of hydroxyl group by protonation. The experimental procedure consisted of the slow replacement of interlayer Rb+ cation of RbLaTa2O7 Dion-Jacobson (DJ) perovskite by H+ via acid treatment. Two layered perovskites synthesized by mild (1200 °C for 18 h) and harsh (950 and 1200 °C, for 36 h) annealing treatment routes were used as starting materials. The successful intercalation of proton into D-J interlayer galleries was confirmed by FTIR spectroscopy, thermal analyses, ion chromatography and XPS results. In addition, the ion-exchange route was effective to enlarge the specific surface area, thus enhancing the supply of photocharges able to participate in redox processes involved in the degradation of organic pollutants. HLaTa_01 protonated layered perovskite is reported as a efficient photocatalyst for photomineralization of trichloroethylene (TCE) to Cl− and CO2 under simulated solar light. The enhanced activity is attributed to combined beneficial roles played by the increased specific surface area and high density of hydroxyl groups, leading to an efficiency of TCE mineralization of 68% moles after 5 h of irradiation.
Nicoleta Cioatera, Elena-Adriana Voinea, Petre Osiceanu, Florica Papa, Alina Duță, Ionut Resceanu, and Cezar-Ionut Spinu
Elsevier BV
Monica Raciulete, Florica Papa, Daisuke Kawamoto, Cornel Munteanu, Daniela C. Culita, Catalin Negrila, Irina Atkinson, Veronica Bratan, Jeanina Pandele-Cusu, and Ioan Balint
Elsevier BV
Corina Bradu, Constantin Căpăţ, Florica Papa, Ligia Frunza, Elena-Alina Olaru, Grégorio Crini, Nadia Morin-Crini, Élise Euvrard, Ioan Balint, Irina Zgura,et al.
Elsevier BV