Igor Crețescu - Academia.edu (original) (raw)

Papers by Igor Crețescu

Chemosphere

h i g h l i g h t s A. platensis is screened as a microalgae candidate for environment control in... more h i g h l i g h t s A. platensis is screened as a microalgae candidate for environment control in space. Air contaminated with multiple trace gaseous contaminants is addressed. Next-generation lighting technology is involved as illumination alternative. Biosystem diagnosis is efficiently performed via mathematical tools. More than 80% contaminants removal can be achieved.

Chemical Engineering Research & Design, May 1, 2017

Abstract Two activated carbons (ACs) derived from apple wood (AWAC) and peach stone (PSAC), and o... more Abstract Two activated carbons (ACs) derived from apple wood (AWAC) and peach stone (PSAC), and one keratinous material extracted from hydrolyzed wool (WHA) were tested for their adsorption capacity for Acid Red 337 (AR) and 1:2 chromium complex of Acid Blue 349 (AB). A commercial granular activated carbon (GAC) was chosen as reference sorbent. The sorbent characteristics, the dye concentration, the contact time and the working pH were the factors taken into consideration. The SEM images of AWAC and PSAC show different morphologies and pore structures. FTIR spectra of the WHA material did not indicate any drastic disruption of keratin macromolecule. The AR dye exhibited higher uptake as compared with the AB dye for all sorbents. The sorption capacity of the tested materials increased in sequence: AWAC

Revista De Chimie, Apr 9, 2008

The presence of oxygen and heavy metals naturally found in red wines, leads to the depreciation o... more The presence of oxygen and heavy metals naturally found in red wines, leads to the depreciation of their qualities, due to the malvidin-3-glucoside degradation. In this paper, the kinetic of the malvidin-3-glucoside degradation, in synthetic wine model solutions, in the presence of different concentrations of iron and copper, at a temperature of 70 o C and two pH values of the wines (2.9 and 3.4 respectively), was studied using the molecular absorption spectrophotometry method.

... COJOCARU DC, Enzimologie practică, Editura Tehnopress, Iaşi, 2005. GEORGESCU CC, ENE M., PETR... more ... COJOCARU DC, Enzimologie practică, Editura Tehnopress, Iaşi, 2005. GEORGESCU CC, ENE M., PETRESCU M., ŞTEFĂNESCU M., MIRON V., Bolile şi dăunătorii pădurilor. Biologie şi combatere, Editura Agro - Silvică de Stat, Bucureşti, 1957. JURCA VALENTINA, MANOLIU ...

BULETINUL INSTITUTULUI POLITEHNIC DIN IAȘI. Secția Matematica. Mecanică Teoretică. Fizică

The present research aimed to electrodeposit and characterize Ni-W alloys for different technolog... more The present research aimed to electrodeposit and characterize Ni-W alloys for different technological parameters, being an example of “induced co-deposition”, in which a certain metal (for example: Mo, W) can be co-deposited as an alloy, but it cannot be measured in its pure state. The investigated characteristics were the efficiency current, the average thickness, and the structural properties of the obtained deposits. The current efficiency decreases with an increased applied current density, and the tungsten content remains constant at around 11% for different current densities (10 mA·cm−2 and 16 mA·cm−2, respectively). An increase in the temperature of the electrolyte leads to the inclusion of more tungsten. The deposit tungsten content and the current efficiency are directly related to pH. The deposit hardness directly relates to the alloy composition, deposit morphology, and coating thickness. The higher hardness, approximatively 100 HV were measured and the optimal brightness...

Sustainability

This paper investigates the valorization potential of two biowaste types resulting from biotrickl... more This paper investigates the valorization potential of two biowaste types resulting from biotrickling filtration of volatile organic compounds (i.e., ethanol) and carbon dioxide from air by co-immobilized microalgae and compost heterotrophs, which were either attached on polypropylene spheres or entrapped within the alginate beads. In this regard, biomass samples from the surface of the packing spheres (S1) and the waste alginate beads (S2) underwent thermal and energy characterization via thermogravimetry and calorimetry techniques as a screening step for establishing some possible biomass valorization pathways. The heat release capacity (HRC) values for the samples S1 and S2 were 95.67 J/(g·K) and 44.11 J/(g·K), respectively, while the total heat release (THR) values were 11.03 kJ/g and 3.64 kJ/g, respectively. The results of this study indicate that the S1 biomass could be suitable for undergoing thermal decomposition processes-based applications, while the S2 biomass could have a...

Materials

Fly ash wastes (silica, aluminum and iron-rich materials) could be smartly valorized by their inc... more Fly ash wastes (silica, aluminum and iron-rich materials) could be smartly valorized by their incorporation in concrete formulation, partly replacing the cement. The necessary binding properties can be accomplished by a simple procedure: an alkali activation process, involving partial hydrolysis, followed by gel formation and polycondensation. The correlations between the experimental fly ash processing conditions, particle characteristics (size and morphology) and the compressive strength values of the concrete prepared using this material were investigated by performing a parametric optimization study to deduce the optimal processing set of conditions. The alkali activation procedure included the variation of the NaOH solutions concentration (8–12 M), temperature values (25–65 °C) and the liquid/solid ratio (1–3). The activation led to important modifications of the crystallography of the samples (shown by powder XRD analysis), their morphologies (seen by SEM), particle size distr...

In this paper, the study of obtaining new coordination compounds of Cr (III) using as ligand, suc... more In this paper, the study of obtaining new coordination compounds of Cr (III) using as ligand, succinimide and the stability constants, were presented. Conductometric, pH-metric and spectrophotometric studies of Cr(III)-succinimide system were carried out in aqueous medium. The "molar ratio" method was used to study the complex formation in solution and for determine the stability constants was used Harvey-Manning method.From experimental data resulted that the combination ratio of the ligand succinimide with central metallic atoms was: 1:1, 2:1 and respectively 3:1.

Environmental Engineering and Management Journal, 2002

This paper shows results of tests in which clinoptilolite powders were evaluated for treating the... more This paper shows results of tests in which clinoptilolite powders were evaluated for treating the radioactive wastes streams. The objective of this study was to examine the ion-exchange characteristics and the abilities to uptake radioisotopes of indigene clinoptilolite from Marsid area-Romania. The effect of particle size and contacting time on K d and radioactivity removal was studied.

The bis-Schiff base, N,N’-bis(salicylidene)-methylenediamine, (H2L1) known as Salmen, forms toget... more The bis-Schiff base, N,N’-bis(salicylidene)-methylenediamine, (H2L1) known as Salmen, forms together Fe(III) at low acid pH a brown precipitate, which is stable at room temperature. Study of the IR spectroscopy and the chemical analysis has evidenced that the precipitation form is a complex and the combination ratio of M:L is 1:1. The precipitation form will be used as a method for the gravimetric determination of Fe(III) with Salmen. The precipitate was dried at room temperature at constant weight and weighed as C15H12O2N2Fe(OH).2H2O. The analytical application presents an average relative error of + 0.5 %, and interferences with Cu(II), Zn(II), Cr(III), Mn(II), Ni(II), U(VI) and Co(II).

Revista De Chimie, 2020

The radon isotope, Rn, has a significant impact on human beings due to the irradiation caused ill... more The radon isotope, Rn, has a significant impact on human beings due to the irradiation caused illnesses. The article deals with the process of radon entering into residential buildings and its residential exposure level related to changes in environmental parameters such as temperature, pressure and moisture content. Dependence of the indoor radon activity on environmental factors has been studied at three sites: two multi-storey and one low-rise buildings in autumn (September – November 2014) period. During the study period radon activity values in low-rise house constructed in 2009, in Lithuania at Ukmergė district, Jogvilų village, ranged from 73 ± 13 to 747 ± 134 Bq m and the average value was 382 ± 76 Bq m. This value is higher than the allowed average activity value of 300 Bq m and could present a radiological risk for inhabitants if the above mentioned parameters are not taken into account.

Electrochemical Sensors Technology, 2017

This chapter aims a comprehensive presentation of the most common electrochemical sensors used in... more This chapter aims a comprehensive presentation of the most common electrochemical sensors used in the real monitoring applications of air purity testing. Oxygen, hydrogen, hydrogen sulfide, nitrogen oxides, carbon monoxide and carbon dioxide are gases, which can be accurately detected and measured. Too high or too low oxygen concentration levels make the air improper for breathing. Hydrogen sulfide and carbon monoxide are dangerous species; any leakage needs to be pinpointed. A calibrated network of sensors for monitoring gas detection makes it possible to easily locate the source of gas escape during indoor air monitoring. The air quality monitoring stations based on electrochemical sensors are nowadays used to determine the global pollution index of the atmospheric air, in order to prevent the risks toward the human health and damage of environment, especially in the highly populated and industrialized urban areas.

Environmental Engineering and Management Journal, 2017

The paper presents a study concerning the influence of the hydraulic and hydrological connectivit... more The paper presents a study concerning the influence of the hydraulic and hydrological connectivity among the oxbow lakes and the restoration of riparian-zones have on aging. Interconnectivity oxbow lakes emerge after complex regulating works for the protection of the shores and bottom of the lakes. Research has analyzed the influence of the hydraulic connectivity of three lakes located in northern Poland on the structure of associated bottom invertebrates-elements that monitor the conditions in habitats. The structure and functioning of ecosystems in wetlands, including in oxbow lakes, are direct or indirect in connection to fluctuations in water levels during floods or flow pulsations. Hydrological processes cause changes in the chemical composition of the water in oxbow lakes and sediment dispersion due to the exchange between water and sediments. In the lentic habitats (disconnected from the main river), the retention time is longer than in the semi-and lotic oxbow lakes whereas the productivity of the ecosystem is only internal and limited. The use of macrozoobenthos as bioindicators in reconnected oxbow lakes in small river valleys indicates that, on the long-term period (5 years), it does not have as a result the improvement of the environmental conditions of those habitats. This is shown by the monitoring indicators. The main reason seems to be the loss of the full connectivity between the oxbow lakes and the main river channel within 3 to 4 years, having as a result only systems of semilotic oxbow lakes and rivers. This hampers the free exchange of waters between ecosystems, the washing out of nutrients accumulated in sediments, the removal of bottom sediments, as well as the migration of hydrobionts. Therefore, the improvement of the ecological condition of the oxbow lake habitats and the permanence of those changes depend on the possibility of keeping the full hydrological connectivity to the river.

Environmental Engineering and Management Journal, 2019

TiO2-assisted photocatalysis is used in numerous environmental applications and for the manufactu... more TiO2-assisted photocatalysis is used in numerous environmental applications and for the manufacturing of different products. Agdoped TiO2 nanoparticles were synthesized by impregnation using silver nitrate solution on TiO2 obtained by sol-gel method and on commercial Degusa P25 (Evonik). Silver is widely studied as a dopant for semiconductor materials, due to its antibacterial properties. In addition to this, it acts as electron sink and donor for photogenerated electrons, enhancing the photocatalytic activity. The physical properties of the samples calcined at different temperatures were investigated by XRD, XRF, SEM, TEM, SAED and EDAX techniques. The calcination temperature of 650 o C led to the total transformation of titanium dioxide (anatase) to rutile phase when commercial P25 was doped with Ag. In the case of samples produced by sol-gel method, the anatase is still the major phase even at this temperature. The photocatalytic activity of the synthesized catalysts was evaluated in the UV-assisted photodegradation of Rhodamine 6G and Congo Red dyes. The conversion yield of Rhodamine 6G reached 66.5% and that of Congo Red was 53% after 120 minutes of irradiation.

Revista de Chimie, 2008

The corrosion behaviour of nickel-based alloys (Heraenium, Verabond and V alloy) in simulated sal... more The corrosion behaviour of nickel-based alloys (Heraenium, Verabond and V alloy) in simulated saliva was studied by gravimetric, pH-metric and conductometric methods, as well as by potentiodynamic polarization and by electrochemical impedance spectroscopy (EIS). The main parameters of the corrosion process were established. Additionally, the results obtained with SEM and AAS analyses were reported. All alloys pass directly into a stable passive region, without exhibiting the usual active-passive transition. The EIS results show that a Ni-based alloy exhibits passivity at open circuit potential. The proposed equivalent circuit contains two R-CPE elements in parallel. The physical meaning given to the circuit is the association of the film/electrolyte interface with the passive film itself. The corrosion resistance of the studied non-precious alloys is in the following order: Heraenium alloy ] V alloy ] Verabond alloy.

Materiale Plastice, 2017

The aim of experiment was to evaluate the local impact of mercury accumulations, discharge from c... more The aim of experiment was to evaluate the local impact of mercury accumulations, discharge from coal power plants, by examining samples of ash, slag, soil, spontaneous vegetation and crop plants, using as analytical techniques the cold vapor atomic absorption spectroscopy. Mercury determined in samples of lignite (0.020 mg. Kg-1), is found in fly ash samples retained by filters (0.037 mg.Kg-1), bottom ash transported hydraulic in deposit (0.022 mg.Kg-1), adjacent soils landfill and the power plant (0.12 mg.Kg-1 or 0.049 mg.Kg-1). The mercury content in vegetation presents differentiated values depending on the bioavailability of plant, area and the positioning of the emission source, reaching values between 0.014 at 0.005 mg.Kg-1 in the wild flora and 0.022 mg.Kg-1 to 0.004 mg.Kg-1 for plants crop. Data obtained for plants, confirmed that most families tend to accumulate mercury plant in larger quantities in the roots (0.022 � 0.0016 mg.Kg-1) and moderate quantities in the foliar le...

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Environmental Engineering and Management Journal, 2012

Wireless local area networks (WLAN) are an increasingly used communication technology employing e... more Wireless local area networks (WLAN) are an increasingly used communication technology employing energy of radiofrequency (RF). Although the power emitted by WLAN systems is relatively small (in Europe, a maximum of 100 mW is permitted in the classic 2.4 GHz frequency band), concerns about possible health effects risks from exposure to radiofrequency (RF) fields originating on WLAN are sometimes expressed by the general public. In such a context, this paper presents results of a survey conducted in different office environments, with the aim to provide an overview of the RF exposure levels from common WLAN equipment, including access points and client stations.

Environmental Engineering and Management Journal, 2010

In order to obtain new complexes of Fe(III) with multiple uses, their characteristics, important ... more In order to obtain new complexes of Fe(III) with multiple uses, their characteristics, important applications and also the obtaining conditions are studied. The obtaining conditions consist in mixing solutions of the same concentrations of ligand 2 amino-6methoxy-benzothiazole sulphonic acid→1-naphtol-4-sulphonic acid with FeCl 3. The solutions are mixed in molar ratios of 1:1, 2:1 and 3:1 (ligand to central metallic atom). For determining the molar ratio ligand:central metallic atom, the methods applied were: pH-metry, conductometry, UV-VIS spectrophotometry. Also, the stability constants for new obtained compounds were determined using Molar Ratio method (J.H.Yoe and A.L.Jones), Continuous Variation method (Job) and Harvay-Manning method. The stability of the new obtained compounds is studied by varying the pH of its solution. The values are K 1 = 2.56•10 6 L/mol for FeL 1 ; K 2 = 19.76•10 13 L/mol for Fe L 2 and K 3 = 30.03•10 32 L/mol for Fe L 3. The higher value for stability is assigned to the compound with molar ratio 3:1 (ligand: metal) in the 1.5÷6.5 pH range. The maxim value for the absorbance was measured at λ max = 601 nm for FeL 1 , λ max = 601 nm for FeL 2 and respective λ max = 600 nm for FeL 3. The studied complexes are very stable in the above-mentioned pH range and could be used for spectrophotometric determination of Fe(III) in visible domain. Another practical importance is represented by wastewater treatments by membranar separation. Thus, the separation process is improved by increasing the volume of these complexes in comparison with both ligand and Fe(III) and further the iron recovery by calcinations was accomplished.

Environmental Engineering and Management Journal, 2008