Mircea Stefan - Academia.edu (original) (raw)

Papers by Mircea Stefan

Research paper thumbnail of The binding of Violamycin BI to poly-C

Biophysical Chemistry, Dec 1, 1996

The binding constant Kst of Violamycin BI (VBI) to poly-C at small and medium values of the conce... more The binding constant Kst of Violamycin BI (VBI) to poly-C at small and medium values of the concentration ratio p (0-12) is determined using the procedure of Schwarz under two different conditions: at constant C(VBIo) and variable C(po), and at p = C(po)/C(VBIo) = const. The average value obtained for Kst is 3.3 +/- 0.1 x 10(4) M-1, whereas the cooperativity parameter q of 13 characterizes a moderate cooperative interaction between adjacent bound ligands. In contrast, at large values of p (12-355) the formation of isolated bound dimers on the poly-C chain is observed. At pH 7, VBI dimerizes in solution with a dimerization constant strongly dependent on ionic strength: Kd = 732 +/- 20 M-1 and (9.3 +/- 0.2) x 10(3) M-1 at I = 0.02 M and 0.2 M respectively. The lower and upper boundaries for the binding constant of the dimer to the polynucleotide at large values of p are 1.0 x 10(-5) M-1 and 6.25 x 10(-6) M-1 respectively.

Research paper thumbnail of ChemInform Abstract: Optimization of Hydrogen Production from Water Using Proflavine as Photosensitizer

Research paper thumbnail of Sound power determination for centrifugal pumps used for local agricultural irrigation in Romania

E3S Web of Conferences, 2020

Technological enhancements in the domain of agriculture have led to easing the burden of physical... more Technological enhancements in the domain of agriculture have led to easing the burden of physical work and increased productivity. Irrigation has always been one of the most crucial elements needed for a high yielding crop, given the current uncertainty of climate change, where climate is increasing in unpredictability. Even though a wide array of methods has been developed in recent years, for the Romanian local agricultural irrigation, a popular method remains using motor-pumps. But the issue with this type of equipment is that during active functioning, it produces high sustained levels of noise pollution, and the risk of operator hearing damage is relatively unknown for long term exposures (years). In this paper, the levels of acoustic power of an irrigation motor-pump model WHT-60 were determined, taking into consideration the required standards, and directives, necessary for this activity, imposed by the European Union for all member countries.

Research paper thumbnail of Treatment and Management of Distillery Fermented Fruit Spent Marc. I. Processing Into Compacted Solid Fuel

Environmental Engineering and Management Journal, 2009

The study presents the processing possibilities for marc resulted as still residue from the disti... more The study presents the processing possibilities for marc resulted as still residue from the distillation of fermented fruits in view to obtain a compacted solid fuel. Initial marc composition (carbon, hydrogen, nitrogen, sulphur and oxygen contents) determined by elemental analysis is evidenced, as well as technical characterisation (ash and moisture contents) and ash's qualitative composition, chemical characterisation of the liquid phase (pH, total phosphorus, acidity and conductivity). The biomass was initially dried in natural conditions (at 20 o C and 50% humidity) and then at 105 o C in a drying stove, until constant mass was reached. Dried biomass was chopped into small pieces of different sizes in the range 0÷5 mm and moistened at different moisture degrees: 15%, 20% and 25%. Cylindrical briquettes were prepared, from three types of material, using a piston press with hydraulic action at pressures of either 600 kgf•cm-2 or 900 kgf•cm-2. The obtained briquettes were characterized in order to determine the heating power, their behaviour in the presence of water and also the mechanical properties (falling and bending strengths). The good values of heating power (12.72 MJ•kg-1 at 15 % moisture) and bending strength (up to 150 kgf•cm-2) of the briquettes obtained at 900 kgf•cm-2 pressure recommend their use as domestic fuel.

Research paper thumbnail of Review of Soil Quality Improvement Using Biopolymers from Leather Waste

Polymers, May 9, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Assessment of Heavy Metals Pollution of Snagov Lake, Romania

Revista De Chimie, Mar 15, 2017

Distribution of heavy metals and trace elements from anthropogenic origin in water, sediments, aq... more Distribution of heavy metals and trace elements from anthropogenic origin in water, sediments, aquatic plants and different tissues of fish from Snagov Lake, Romania. has been investigated. The concentration of Cu, Zn, Cd, Ti, V, Cr, Mo, Co and Ni, was collected from three sites of the lake, during spring time from water, sediments, Ceratophyllum demersum, Phragmites australis reed, and Scardinius Erytrophtalmus fish. The fish samples were taken from gills, muscles, scales and bones. The ecological risk index has been assesed and bio-concentration factor, (BCF), of metals in anatomical tissues of studied fishes to be used as a diagnostic tool for lake pollution Experiments have shown that Ti and Zn had the highest concentration in water, sediments, aquatic plants and fish samples. Also, the metals bio-concentration is increased in branchiae and scales, compared with muscles and bones.

Research paper thumbnail of Distribution of Metals in Water, Sediments, Aquatic Plants and Fish from Snagov Lake, Romania

Environmental Engineering and Management Journal, 2019

This paper discussed the results of studies regarding metal ions distribution in water, sediments... more This paper discussed the results of studies regarding metal ions distribution in water, sediments, aquatic plants and different tissues of fish from Snagov Lake, Romania, a natural lake situated 25-30 kilometers north from Bucharest, the capital of Romania. The concentration of several metal ions (Li, Ba, Al, Pb, As, Se) was measured in three points of the lake, namely receiving-input, middle and discharging-output ponds. The samples were collected during spring time from water, sediments, Ceratophyllum demersum, Phragmites australis reed, and Scardinius Erytrophtalmus fish. The ecological risk, the toxicity class based on the concentration of toxic metals into sediments, according to the Sediments Quality Guidelines (SQGs) and bio-concentration factor, (BCF), of metals in anatomical tissues of studied fishes were assessed. Experiments have shown that aluminum and barium had the highest concentration in water, sediments, aquatic plants and fish samples. Also, the metals bio-concentration is increased in branchiae and scales, compared with muscles and bones.

Research paper thumbnail of Comparative Study on Surface Water Treatment Using Aluminium Sulphate and Polyaluminium Chlorides as Coagulant Reagents

Environmental Engineering and Management Journal, 2009

The paper presents the comparative study regarding the turbidity removal using aluminium sulphate... more The paper presents the comparative study regarding the turbidity removal using aluminium sulphate Al 2 (SO4) 3 *18H 2 O and polyaluminum chlorides, Al n (OH) m Cl 3n-m , commercial name, Sachtoklarr 39, in water treatment plant from Covasna City. The parameters that influence the treatment process and the efficiency of turbidity removal were studied. The water characteristic parameters of Basca Mare and Covasna rivers-the two sources of water alimentation for Covasna water treatment plant were monitored along the year 2007. The turbidity varied from small values admitted by legislation during the winter months up to 753,8 NTU for Basca Mare river and up to 1076 NTU for Covasna river during June with abundant rain and flooding. The efficiency of turbidity removal was much better for polyaluminum chlorides comparatively to aluminium sulphate.

Research paper thumbnail of Study of Bisphenol A Degradation Using Ultrasound and Aditional Chemical Compounds

Bisphenol-A (BPA) represents an important co-monomer for obtaining polycarbonate, epoxy resins, f... more Bisphenol-A (BPA) represents an important co-monomer for obtaining polycarbonate, epoxy resins, flame retardants, in paint, and other chemicals products. Products containing BPA are widely used, and thus, we can find it in the environment: in the air, in the soil, in natural surface water and in sediments, underground water in landfills, and in wastewater. BPA disturbs human and animals’ health. This influences the enzymatic, androgenic, neurological, liver and reproductive systems at different stages of human life: like in fetal stage, children and adults’ stages. Taking these inconveniences into account, it is very important to remove BPA from water. Ultrasonic technology can be considered a verry sustainable and efficient method to remove BPA from water. The advantages of this method is easy to implement on existing water treatment and purification facilities, it does not produce residual compounds that produce sludge, the time required for degradation is of the order of 1-2 hour...

Research paper thumbnail of Clinoptilolite—A Sustainable Material for Removal of Bisphenol A from Water

Bisphenol A is a remarkable chemical compound for its many applications mainly in the plastics in... more Bisphenol A is a remarkable chemical compound for its many applications mainly in the plastics industry, but also for its toxic effects on the environment and human health. BPA (4,4-isopropylidenediphenol) is an anthropogenic compound, moderately soluble in water (120 – 300 mg/l) at room temperature, and highly soluble in alkaline solutions, ethanol and acetone. BPA can bioconcentrate, bioaccumulate and biomagnify through food webs until it reaches humans. To prevent this, effective strategies are sought to allow its removal from the environment, through physico-chemical or enzymatic methods, advanced oxidation, adsorption and biodegradation, ultrasonic degradation. This article shows a comparative study regarding adsorption of BPA on Active carbon and zeolitic tuff, ZTC. In this paper, the characterization of the zeolitic tuff Rupea adsorbent, was carried out from an elemental and mineralogical point of view, pore size and elemental distribution, using SEM, EDAX, and XRD analysis. ...

Research paper thumbnail of Comparative Study of Useful Compounds Extracted from Lophanthus anisatus by Green Extraction

Molecules

Essential oils were obtained from different parts of Agastache foeniculum (Lophanthus anisatus) p... more Essential oils were obtained from different parts of Agastache foeniculum (Lophanthus anisatus) plants by means of extraction: green extraction using hydro-distillation (HD) and bio-solvent distillation, BiAD, discontinuous distillation, and supercritical fluid extraction, in two stages: (1) with CO2, and (2) with CO2 and ethanol co-solvent. The extraction yields were determined. The yield values varied for different parts of the plant, as well as the method of extraction. Thus, they had the values of 0.62 ± 0.020 and 0.92 ± 0.015 g/100 g for the samples from the whole aerial plant, 0.75 ± 0.008 and 1.06 ± 0.005 g/100 g for the samples of leaves, and 1.22 ± 0.011 and 1.60 ± 0.049 g/100 g for the samples of flowers for HD and BiAD, respectively. The yield values for supercritical fluid extraction were of 0.94 ± 0.010 and 0.32 ± 0.007 g/100 g for the samples of whole aerial plant, 0.9 ± 0.010 and 1.14 ± 0.008 g/100 g for the samples of leaves, and 1.94 ± 0.030 and 0.57 ± 0.003 g/100 g...

Research paper thumbnail of Methods for Natural and Synthetic Polymers Recovery from Textile Waste

Polymers

Trends in the textile industry show a continuous increase in the production and sale of textile m... more Trends in the textile industry show a continuous increase in the production and sale of textile materials, which in turn generates a huge amount of discarded clothing every year. This has a negative impact on the environment, on one side, by consuming resources—some of them non-renewables (to produce synthetic polymers)—and on the other side, by polluting the environment through the emission of GHGs (greenhouse gases), the generation of microplastics, and the release of toxic chemicals in the environment (dyes, chemical reagents, etc.). When natural polymers (e.g., cellulose, protein fibers) are used for the manufacturing of clothes, the negative impact is transferred to soil pollution (e.g., by using pesticides, fertilizers). In addition, for the manufacture of clothes from natural fibers, large amounts of water are consumed for irrigation. According to the European Environment Agency (EEA), the consumption of clothing is expected to increase by 63%, from 62 million tonnes in 2019 ...

Research paper thumbnail of Influence of Internal Structure of the Sorbents on Diazepam Sorption from Simulated Intestinal Fluid

Applied Sciences

The capacity of natural Na-montmorillonite and activated charcoal for sorption of diazepam from s... more The capacity of natural Na-montmorillonite and activated charcoal for sorption of diazepam from simulated intestinal fluid (SIF) was studied. The main characteristics of the sorbents were determined. In order to characterize the sorption process of diazepam the influence of the pH, contact time and ethanol presence in SIF was analyzed. Adsorption isotherms for the diazepam-activated charcoal and diazepam-natural Na-montmorillonite systems were determined. The Langmuir isotherm model provided a very good description of diazepam sorption. Furthermore, the pH-drift method was used to determine the specific pH at zero point of charge (pHzpc) of the sorbents. The obtained results show that the internal structure of the sorbents and pH of the SIF solutions are very important for diazepam sorption. Both the surface of the activated charcoal and natural Na-montmorillonite are positively charged below the pHzpc so the sorption of diazepam is higher below this point and occur by van der Waals...

Research paper thumbnail of Review of Soil Quality Improvement Using Biopolymers from Leather Waste

Polymers

This paper reviews the advantages and disadvantages of the use of fertilizers obtained from leath... more This paper reviews the advantages and disadvantages of the use of fertilizers obtained from leather waste, to ameliorate the agricultural soil quality. The use of leather waste (hides and skins) as raw materials to obtain biopolymer-based fertilizers is an excellent example of a circular economy. This allows the recovery of a large quantity of the tanning agent in the case of tanned wastes, as well as the valorization of significant quantities of waste that would be otherwise disposed of by landfilling. The composition of organic biopolymers obtained from leather waste is a rich source of macronutrients (nitrogen, calcium, magnesium, sodium, potassium), and micronutrients (boron, chloride, copper, iron, manganese, molybdenum, nickel and zinc), necessary to improve the composition of agricultural soils, and to remediate the degraded soils. This enhances plant growth ensuring better crops. The nutrient release tests have demonstrated that, by using the biofertilizers with collagen or ...

Research paper thumbnail of Sorption of Phenobarbital and Amobarbital on Na-montmorillonite

Revista de Chimie, 2001

In order to characterize the sorption kinetics of phenobarbital sodium and amobarbital sodium on ... more In order to characterize the sorption kinetics of phenobarbital sodium and amobarbital sodium on natural Na � montmorillonite, the influence of the initial drug concentration and clay particles sizes was investigated. Equilibrium isotherms have been measured and analyzed using a Langmuir isotherm model. The affinity of drugs sorbed onto clay varied in the following descending order: phenobarbital sodium ] amobarbital sodium, respectively 11.2 and 9.1 mg/g. Also, sorption of phenobarbital sodium and amobarbital sodium on Na-montmorillonite was studied as a function of pH. The results show that adsorption of the drugs is highest below the pHZPC due the neutrality of the drugs which adsorbs via an attraction of the positively charged surface sites at lower pH by weak van der Waals forces.

Research paper thumbnail of Removal of Antibiotics from Wastewater Using Photocatalytic Membranes

CRISTINA ORBECI1, MIRCEA STEFAN2*, ANNETTE MADELENE DANCILA1, MIHAI SILVIU TUDOSIE3,4 1 Universit... more CRISTINA ORBECI1, MIRCEA STEFAN2*, ANNETTE MADELENE DANCILA1, MIHAI SILVIU TUDOSIE3,4 1 University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, 1-7 Gh. Polizu Str., 011061, Bucharest, Romania 2. University Titu Maiorescu, Pharmacy Faculty, Bucharest, 22 Dâmbovnicului Str., 040441, Bucharest, Romania 3 University of Medicine and Pharmacy Carol Davila Bucharest, 8 Eroii Sanitari Blvd., 050474, Bucharest, Romania, 4 Army Center for Medical Research, Bucharest, Romania

Research paper thumbnail of Treatment and Management of Distillery Fermented Fruit Spent Marc. I. Processing Into Compacted Solid Fuel

Environmental Engineering and Management Journal, 2009

This paper presents a comparative study of natural and mechanically mixed composting processes of... more This paper presents a comparative study of natural and mechanically mixed composting processes of marc resulting as a byproduct during the production of alcohol obtained from fermented fruits. Moisture, temperature, pH values, soluble fraction, total organic carbon, Kjeldahl nitrogen and ash content were monitored for 60 days. During this period the atmospheric temperature varied from 18ºC to 21ºC. The composting process could be considered a combination of three stages: mesophilic, thermophilic, and maturation. The composting process need 34 days in mechanical stirred system and 46 days in the natural system. The biodegradation processes were stimulated by the mechanical stirring.

Research paper thumbnail of Distribution of Metals in Water, Sediments, Aquatic Plants and Fish from Snagov Lake, Romania

Environmental Engineering and Management Journal, 2019

This paper discussed the results of studies regarding metal ions distribution in water, sediments... more This paper discussed the results of studies regarding metal ions distribution in water, sediments, aquatic plants and different tissues of fish from Snagov Lake, Romania, a natural lake situated 25-30 kilometers north from Bucharest, the capital of Romania. The concentration of several metal ions (Li, Ba, Al, Pb, As, Se) was measured in three points of the lake, namely receiving-input, middle and discharging-output ponds. The samples were collected during spring time from water, sediments, Ceratophyllum demersum, Phragmites australis reed, and Scardinius Erytrophtalmus fish. The ecological risk, the toxicity class based on the concentration of toxic metals into sediments, according to the Sediments Quality Guidelines (SQGs) and bio-concentration factor, (BCF), of metals in anatomical tissues of studied fishes were assessed. Experiments have shown that aluminum and barium had the highest concentration in water, sediments, aquatic plants and fish samples. Also, the metals bio-concentration is increased in branchiae and scales, compared with muscles and bones.

Research paper thumbnail of Optimizing Enzymatic Biodegradation of Skins Waste Using Response Surface Methodology

Revista de Chimie, 2019

Response surface methodology (RSM) was employed to evaluate the optimum biodegradation of pelt sk... more Response surface methodology (RSM) was employed to evaluate the optimum biodegradation of pelt skin wastes (BPSW). The parameters investigated include the pH, temperature, and enzymes mixture ratio of hydrolases, proteases and oxide - reductases on biodegradation degree for Pelt skin waste. The pH varied between 4.00 � 0.2 and 7.00� 0.2 and temperature between 30-50�C. Was used three mixtures tested having the following composition expressed as ratio between E1:E2:E3. M1- (1:1:1); M2-(2:1:1) and M3-(3:1:1) expressed in mg/L. Response surface methodology (RSM) was used to evaluate the influence of each independent variable on the overall biodegradation efficiency of waste skin. Optimum biodegradation efficiency was achieved at pH=8.4, E1 concentration in the enzyme mixture 2 mg/L and temperature 42.4 0C. Biodegradation degree is 0.996. Very similar results could be obtained for optimal extraction conditions using the desirability profiles available also in STATISTICA software.

Research paper thumbnail of Assessment of Heavy Metals Pollution of Snagov Lake, Romania

Revista de Chimie, 2017

Distribution of heavy metals and trace elements from anthropogenic origin in water, sediments, aq... more Distribution of heavy metals and trace elements from anthropogenic origin in water, sediments, aquatic plants and different tissues of fish from Snagov Lake, Romania. has been investigated. The concentration of Cu, Zn, Cd, Ti, V, Cr, Mo, Co and Ni, was collected from three sites of the lake, during spring time from water, sediments, Ceratophyllum demersum, Phragmites australis reed, and Scardinius Erytrophtalmus fish. The fish samples were taken from gills, muscles, scales and bones. The ecological risk index has been assesed and bio-concentration factor, (BCF), of metals in anatomical tissues of studied fishes to be used as a diagnostic tool for lake pollution Experiments have shown that Ti and Zn had the highest concentration in water, sediments, aquatic plants and fish samples. Also, the metals bio-concentration is increased in branchiae and scales, compared with muscles and bones.

Research paper thumbnail of The binding of Violamycin BI to poly-C

Biophysical Chemistry, Dec 1, 1996

The binding constant Kst of Violamycin BI (VBI) to poly-C at small and medium values of the conce... more The binding constant Kst of Violamycin BI (VBI) to poly-C at small and medium values of the concentration ratio p (0-12) is determined using the procedure of Schwarz under two different conditions: at constant C(VBIo) and variable C(po), and at p = C(po)/C(VBIo) = const. The average value obtained for Kst is 3.3 +/- 0.1 x 10(4) M-1, whereas the cooperativity parameter q of 13 characterizes a moderate cooperative interaction between adjacent bound ligands. In contrast, at large values of p (12-355) the formation of isolated bound dimers on the poly-C chain is observed. At pH 7, VBI dimerizes in solution with a dimerization constant strongly dependent on ionic strength: Kd = 732 +/- 20 M-1 and (9.3 +/- 0.2) x 10(3) M-1 at I = 0.02 M and 0.2 M respectively. The lower and upper boundaries for the binding constant of the dimer to the polynucleotide at large values of p are 1.0 x 10(-5) M-1 and 6.25 x 10(-6) M-1 respectively.

Research paper thumbnail of ChemInform Abstract: Optimization of Hydrogen Production from Water Using Proflavine as Photosensitizer

Research paper thumbnail of Sound power determination for centrifugal pumps used for local agricultural irrigation in Romania

E3S Web of Conferences, 2020

Technological enhancements in the domain of agriculture have led to easing the burden of physical... more Technological enhancements in the domain of agriculture have led to easing the burden of physical work and increased productivity. Irrigation has always been one of the most crucial elements needed for a high yielding crop, given the current uncertainty of climate change, where climate is increasing in unpredictability. Even though a wide array of methods has been developed in recent years, for the Romanian local agricultural irrigation, a popular method remains using motor-pumps. But the issue with this type of equipment is that during active functioning, it produces high sustained levels of noise pollution, and the risk of operator hearing damage is relatively unknown for long term exposures (years). In this paper, the levels of acoustic power of an irrigation motor-pump model WHT-60 were determined, taking into consideration the required standards, and directives, necessary for this activity, imposed by the European Union for all member countries.

Research paper thumbnail of Treatment and Management of Distillery Fermented Fruit Spent Marc. I. Processing Into Compacted Solid Fuel

Environmental Engineering and Management Journal, 2009

The study presents the processing possibilities for marc resulted as still residue from the disti... more The study presents the processing possibilities for marc resulted as still residue from the distillation of fermented fruits in view to obtain a compacted solid fuel. Initial marc composition (carbon, hydrogen, nitrogen, sulphur and oxygen contents) determined by elemental analysis is evidenced, as well as technical characterisation (ash and moisture contents) and ash's qualitative composition, chemical characterisation of the liquid phase (pH, total phosphorus, acidity and conductivity). The biomass was initially dried in natural conditions (at 20 o C and 50% humidity) and then at 105 o C in a drying stove, until constant mass was reached. Dried biomass was chopped into small pieces of different sizes in the range 0÷5 mm and moistened at different moisture degrees: 15%, 20% and 25%. Cylindrical briquettes were prepared, from three types of material, using a piston press with hydraulic action at pressures of either 600 kgf•cm-2 or 900 kgf•cm-2. The obtained briquettes were characterized in order to determine the heating power, their behaviour in the presence of water and also the mechanical properties (falling and bending strengths). The good values of heating power (12.72 MJ•kg-1 at 15 % moisture) and bending strength (up to 150 kgf•cm-2) of the briquettes obtained at 900 kgf•cm-2 pressure recommend their use as domestic fuel.

Research paper thumbnail of Review of Soil Quality Improvement Using Biopolymers from Leather Waste

Polymers, May 9, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Assessment of Heavy Metals Pollution of Snagov Lake, Romania

Revista De Chimie, Mar 15, 2017

Distribution of heavy metals and trace elements from anthropogenic origin in water, sediments, aq... more Distribution of heavy metals and trace elements from anthropogenic origin in water, sediments, aquatic plants and different tissues of fish from Snagov Lake, Romania. has been investigated. The concentration of Cu, Zn, Cd, Ti, V, Cr, Mo, Co and Ni, was collected from three sites of the lake, during spring time from water, sediments, Ceratophyllum demersum, Phragmites australis reed, and Scardinius Erytrophtalmus fish. The fish samples were taken from gills, muscles, scales and bones. The ecological risk index has been assesed and bio-concentration factor, (BCF), of metals in anatomical tissues of studied fishes to be used as a diagnostic tool for lake pollution Experiments have shown that Ti and Zn had the highest concentration in water, sediments, aquatic plants and fish samples. Also, the metals bio-concentration is increased in branchiae and scales, compared with muscles and bones.

Research paper thumbnail of Distribution of Metals in Water, Sediments, Aquatic Plants and Fish from Snagov Lake, Romania

Environmental Engineering and Management Journal, 2019

This paper discussed the results of studies regarding metal ions distribution in water, sediments... more This paper discussed the results of studies regarding metal ions distribution in water, sediments, aquatic plants and different tissues of fish from Snagov Lake, Romania, a natural lake situated 25-30 kilometers north from Bucharest, the capital of Romania. The concentration of several metal ions (Li, Ba, Al, Pb, As, Se) was measured in three points of the lake, namely receiving-input, middle and discharging-output ponds. The samples were collected during spring time from water, sediments, Ceratophyllum demersum, Phragmites australis reed, and Scardinius Erytrophtalmus fish. The ecological risk, the toxicity class based on the concentration of toxic metals into sediments, according to the Sediments Quality Guidelines (SQGs) and bio-concentration factor, (BCF), of metals in anatomical tissues of studied fishes were assessed. Experiments have shown that aluminum and barium had the highest concentration in water, sediments, aquatic plants and fish samples. Also, the metals bio-concentration is increased in branchiae and scales, compared with muscles and bones.

Research paper thumbnail of Comparative Study on Surface Water Treatment Using Aluminium Sulphate and Polyaluminium Chlorides as Coagulant Reagents

Environmental Engineering and Management Journal, 2009

The paper presents the comparative study regarding the turbidity removal using aluminium sulphate... more The paper presents the comparative study regarding the turbidity removal using aluminium sulphate Al 2 (SO4) 3 *18H 2 O and polyaluminum chlorides, Al n (OH) m Cl 3n-m , commercial name, Sachtoklarr 39, in water treatment plant from Covasna City. The parameters that influence the treatment process and the efficiency of turbidity removal were studied. The water characteristic parameters of Basca Mare and Covasna rivers-the two sources of water alimentation for Covasna water treatment plant were monitored along the year 2007. The turbidity varied from small values admitted by legislation during the winter months up to 753,8 NTU for Basca Mare river and up to 1076 NTU for Covasna river during June with abundant rain and flooding. The efficiency of turbidity removal was much better for polyaluminum chlorides comparatively to aluminium sulphate.

Research paper thumbnail of Study of Bisphenol A Degradation Using Ultrasound and Aditional Chemical Compounds

Bisphenol-A (BPA) represents an important co-monomer for obtaining polycarbonate, epoxy resins, f... more Bisphenol-A (BPA) represents an important co-monomer for obtaining polycarbonate, epoxy resins, flame retardants, in paint, and other chemicals products. Products containing BPA are widely used, and thus, we can find it in the environment: in the air, in the soil, in natural surface water and in sediments, underground water in landfills, and in wastewater. BPA disturbs human and animals’ health. This influences the enzymatic, androgenic, neurological, liver and reproductive systems at different stages of human life: like in fetal stage, children and adults’ stages. Taking these inconveniences into account, it is very important to remove BPA from water. Ultrasonic technology can be considered a verry sustainable and efficient method to remove BPA from water. The advantages of this method is easy to implement on existing water treatment and purification facilities, it does not produce residual compounds that produce sludge, the time required for degradation is of the order of 1-2 hour...

Research paper thumbnail of Clinoptilolite—A Sustainable Material for Removal of Bisphenol A from Water

Bisphenol A is a remarkable chemical compound for its many applications mainly in the plastics in... more Bisphenol A is a remarkable chemical compound for its many applications mainly in the plastics industry, but also for its toxic effects on the environment and human health. BPA (4,4-isopropylidenediphenol) is an anthropogenic compound, moderately soluble in water (120 – 300 mg/l) at room temperature, and highly soluble in alkaline solutions, ethanol and acetone. BPA can bioconcentrate, bioaccumulate and biomagnify through food webs until it reaches humans. To prevent this, effective strategies are sought to allow its removal from the environment, through physico-chemical or enzymatic methods, advanced oxidation, adsorption and biodegradation, ultrasonic degradation. This article shows a comparative study regarding adsorption of BPA on Active carbon and zeolitic tuff, ZTC. In this paper, the characterization of the zeolitic tuff Rupea adsorbent, was carried out from an elemental and mineralogical point of view, pore size and elemental distribution, using SEM, EDAX, and XRD analysis. ...

Research paper thumbnail of Comparative Study of Useful Compounds Extracted from Lophanthus anisatus by Green Extraction

Molecules

Essential oils were obtained from different parts of Agastache foeniculum (Lophanthus anisatus) p... more Essential oils were obtained from different parts of Agastache foeniculum (Lophanthus anisatus) plants by means of extraction: green extraction using hydro-distillation (HD) and bio-solvent distillation, BiAD, discontinuous distillation, and supercritical fluid extraction, in two stages: (1) with CO2, and (2) with CO2 and ethanol co-solvent. The extraction yields were determined. The yield values varied for different parts of the plant, as well as the method of extraction. Thus, they had the values of 0.62 ± 0.020 and 0.92 ± 0.015 g/100 g for the samples from the whole aerial plant, 0.75 ± 0.008 and 1.06 ± 0.005 g/100 g for the samples of leaves, and 1.22 ± 0.011 and 1.60 ± 0.049 g/100 g for the samples of flowers for HD and BiAD, respectively. The yield values for supercritical fluid extraction were of 0.94 ± 0.010 and 0.32 ± 0.007 g/100 g for the samples of whole aerial plant, 0.9 ± 0.010 and 1.14 ± 0.008 g/100 g for the samples of leaves, and 1.94 ± 0.030 and 0.57 ± 0.003 g/100 g...

Research paper thumbnail of Methods for Natural and Synthetic Polymers Recovery from Textile Waste

Polymers

Trends in the textile industry show a continuous increase in the production and sale of textile m... more Trends in the textile industry show a continuous increase in the production and sale of textile materials, which in turn generates a huge amount of discarded clothing every year. This has a negative impact on the environment, on one side, by consuming resources—some of them non-renewables (to produce synthetic polymers)—and on the other side, by polluting the environment through the emission of GHGs (greenhouse gases), the generation of microplastics, and the release of toxic chemicals in the environment (dyes, chemical reagents, etc.). When natural polymers (e.g., cellulose, protein fibers) are used for the manufacturing of clothes, the negative impact is transferred to soil pollution (e.g., by using pesticides, fertilizers). In addition, for the manufacture of clothes from natural fibers, large amounts of water are consumed for irrigation. According to the European Environment Agency (EEA), the consumption of clothing is expected to increase by 63%, from 62 million tonnes in 2019 ...

Research paper thumbnail of Influence of Internal Structure of the Sorbents on Diazepam Sorption from Simulated Intestinal Fluid

Applied Sciences

The capacity of natural Na-montmorillonite and activated charcoal for sorption of diazepam from s... more The capacity of natural Na-montmorillonite and activated charcoal for sorption of diazepam from simulated intestinal fluid (SIF) was studied. The main characteristics of the sorbents were determined. In order to characterize the sorption process of diazepam the influence of the pH, contact time and ethanol presence in SIF was analyzed. Adsorption isotherms for the diazepam-activated charcoal and diazepam-natural Na-montmorillonite systems were determined. The Langmuir isotherm model provided a very good description of diazepam sorption. Furthermore, the pH-drift method was used to determine the specific pH at zero point of charge (pHzpc) of the sorbents. The obtained results show that the internal structure of the sorbents and pH of the SIF solutions are very important for diazepam sorption. Both the surface of the activated charcoal and natural Na-montmorillonite are positively charged below the pHzpc so the sorption of diazepam is higher below this point and occur by van der Waals...

Research paper thumbnail of Review of Soil Quality Improvement Using Biopolymers from Leather Waste

Polymers

This paper reviews the advantages and disadvantages of the use of fertilizers obtained from leath... more This paper reviews the advantages and disadvantages of the use of fertilizers obtained from leather waste, to ameliorate the agricultural soil quality. The use of leather waste (hides and skins) as raw materials to obtain biopolymer-based fertilizers is an excellent example of a circular economy. This allows the recovery of a large quantity of the tanning agent in the case of tanned wastes, as well as the valorization of significant quantities of waste that would be otherwise disposed of by landfilling. The composition of organic biopolymers obtained from leather waste is a rich source of macronutrients (nitrogen, calcium, magnesium, sodium, potassium), and micronutrients (boron, chloride, copper, iron, manganese, molybdenum, nickel and zinc), necessary to improve the composition of agricultural soils, and to remediate the degraded soils. This enhances plant growth ensuring better crops. The nutrient release tests have demonstrated that, by using the biofertilizers with collagen or ...

Research paper thumbnail of Sorption of Phenobarbital and Amobarbital on Na-montmorillonite

Revista de Chimie, 2001

In order to characterize the sorption kinetics of phenobarbital sodium and amobarbital sodium on ... more In order to characterize the sorption kinetics of phenobarbital sodium and amobarbital sodium on natural Na � montmorillonite, the influence of the initial drug concentration and clay particles sizes was investigated. Equilibrium isotherms have been measured and analyzed using a Langmuir isotherm model. The affinity of drugs sorbed onto clay varied in the following descending order: phenobarbital sodium ] amobarbital sodium, respectively 11.2 and 9.1 mg/g. Also, sorption of phenobarbital sodium and amobarbital sodium on Na-montmorillonite was studied as a function of pH. The results show that adsorption of the drugs is highest below the pHZPC due the neutrality of the drugs which adsorbs via an attraction of the positively charged surface sites at lower pH by weak van der Waals forces.

Research paper thumbnail of Removal of Antibiotics from Wastewater Using Photocatalytic Membranes

CRISTINA ORBECI1, MIRCEA STEFAN2*, ANNETTE MADELENE DANCILA1, MIHAI SILVIU TUDOSIE3,4 1 Universit... more CRISTINA ORBECI1, MIRCEA STEFAN2*, ANNETTE MADELENE DANCILA1, MIHAI SILVIU TUDOSIE3,4 1 University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, 1-7 Gh. Polizu Str., 011061, Bucharest, Romania 2. University Titu Maiorescu, Pharmacy Faculty, Bucharest, 22 Dâmbovnicului Str., 040441, Bucharest, Romania 3 University of Medicine and Pharmacy Carol Davila Bucharest, 8 Eroii Sanitari Blvd., 050474, Bucharest, Romania, 4 Army Center for Medical Research, Bucharest, Romania

Research paper thumbnail of Treatment and Management of Distillery Fermented Fruit Spent Marc. I. Processing Into Compacted Solid Fuel

Environmental Engineering and Management Journal, 2009

This paper presents a comparative study of natural and mechanically mixed composting processes of... more This paper presents a comparative study of natural and mechanically mixed composting processes of marc resulting as a byproduct during the production of alcohol obtained from fermented fruits. Moisture, temperature, pH values, soluble fraction, total organic carbon, Kjeldahl nitrogen and ash content were monitored for 60 days. During this period the atmospheric temperature varied from 18ºC to 21ºC. The composting process could be considered a combination of three stages: mesophilic, thermophilic, and maturation. The composting process need 34 days in mechanical stirred system and 46 days in the natural system. The biodegradation processes were stimulated by the mechanical stirring.

Research paper thumbnail of Distribution of Metals in Water, Sediments, Aquatic Plants and Fish from Snagov Lake, Romania

Environmental Engineering and Management Journal, 2019

This paper discussed the results of studies regarding metal ions distribution in water, sediments... more This paper discussed the results of studies regarding metal ions distribution in water, sediments, aquatic plants and different tissues of fish from Snagov Lake, Romania, a natural lake situated 25-30 kilometers north from Bucharest, the capital of Romania. The concentration of several metal ions (Li, Ba, Al, Pb, As, Se) was measured in three points of the lake, namely receiving-input, middle and discharging-output ponds. The samples were collected during spring time from water, sediments, Ceratophyllum demersum, Phragmites australis reed, and Scardinius Erytrophtalmus fish. The ecological risk, the toxicity class based on the concentration of toxic metals into sediments, according to the Sediments Quality Guidelines (SQGs) and bio-concentration factor, (BCF), of metals in anatomical tissues of studied fishes were assessed. Experiments have shown that aluminum and barium had the highest concentration in water, sediments, aquatic plants and fish samples. Also, the metals bio-concentration is increased in branchiae and scales, compared with muscles and bones.

Research paper thumbnail of Optimizing Enzymatic Biodegradation of Skins Waste Using Response Surface Methodology

Revista de Chimie, 2019

Response surface methodology (RSM) was employed to evaluate the optimum biodegradation of pelt sk... more Response surface methodology (RSM) was employed to evaluate the optimum biodegradation of pelt skin wastes (BPSW). The parameters investigated include the pH, temperature, and enzymes mixture ratio of hydrolases, proteases and oxide - reductases on biodegradation degree for Pelt skin waste. The pH varied between 4.00 � 0.2 and 7.00� 0.2 and temperature between 30-50�C. Was used three mixtures tested having the following composition expressed as ratio between E1:E2:E3. M1- (1:1:1); M2-(2:1:1) and M3-(3:1:1) expressed in mg/L. Response surface methodology (RSM) was used to evaluate the influence of each independent variable on the overall biodegradation efficiency of waste skin. Optimum biodegradation efficiency was achieved at pH=8.4, E1 concentration in the enzyme mixture 2 mg/L and temperature 42.4 0C. Biodegradation degree is 0.996. Very similar results could be obtained for optimal extraction conditions using the desirability profiles available also in STATISTICA software.

Research paper thumbnail of Assessment of Heavy Metals Pollution of Snagov Lake, Romania

Revista de Chimie, 2017

Distribution of heavy metals and trace elements from anthropogenic origin in water, sediments, aq... more Distribution of heavy metals and trace elements from anthropogenic origin in water, sediments, aquatic plants and different tissues of fish from Snagov Lake, Romania. has been investigated. The concentration of Cu, Zn, Cd, Ti, V, Cr, Mo, Co and Ni, was collected from three sites of the lake, during spring time from water, sediments, Ceratophyllum demersum, Phragmites australis reed, and Scardinius Erytrophtalmus fish. The fish samples were taken from gills, muscles, scales and bones. The ecological risk index has been assesed and bio-concentration factor, (BCF), of metals in anatomical tissues of studied fishes to be used as a diagnostic tool for lake pollution Experiments have shown that Ti and Zn had the highest concentration in water, sediments, aquatic plants and fish samples. Also, the metals bio-concentration is increased in branchiae and scales, compared with muscles and bones.