The rate constant ratios of the consecutive chlorination of p-xylene at 70 o C in a gas-liquid se... more The rate constant ratios of the consecutive chlorination of p-xylene at 70 o C in a gas-liquid semibatch reactor using molecular chlorine, dichloroethane as a solvent, and antimony pentachloride as a catalyst was investigated up to the fourth successive reaction (tetrachloro-p-xylene production). The rate ratios were determined with both mathematical expressions and a graphical method proposed recently in the literature by use of the maxima of the successive products. In addition, to this simple method that concerns only one pair of values of products (single-point maximum approach), another novel method is proposed and successfully applied concerning many pairs of corresponding values of intermediate products (multiple points maximum approach). This latter method permits the estimation of uncertainties and propagation of uncertainties that proved the usefulness and the possibilities of determining the parameters based on special points of the kinetic dependencies. The rate ratios found for monochloro-p-xylene (2-chloro-p-xylene), dichloro-p-xylene (the sum of 2,3-dichloro-p-xylene and 2,5-dichloro-p-xylene), trichloro-p-xylene (2,3,5-trichloro-p-xylene), and tetrachloro-p-xylene (2,3,5,6-tetrachloro-p-xylene) are k 2 /k 1 = 0.09741, k 3 /k 1 = 0.002685, and k 4 /k 1 = 0.000499. The ratio of the dichloro-isomers produced was also determined in the initial stages as 3.3 in favor of 2,5-dichloro-p-xylene, which is reasonable since 2,3-dichloro-p-xylene is highly hindered by the adjacent groups on the aromatic nucleus. Nevertheless, as the production of trichloro-p-xylene increased considerably, the proportion of 2,3-dichloro-p-xylene gradually diminished down to complete disappearance. This is attributed to the ease of this isomer to be further chlorinated to trichloroproduct since its available free sites on the nucleus are less hindered compared to 2,5-dichloro-p-xylene. The standard uncertainties of the rate constant ratios, the standard deviation of the means, as well as the expanded uncertainties of the means were calculated and proved statistically accepted. Finally, the propagation of uncertainties for the trichloro-p-xylene was estimated using the partial derivatives of this product for each of the rate constant ratios.
Pressurized gas pipelines may be endangered by accidental or intentional activities causing exces... more Pressurized gas pipelines may be endangered by accidental or intentional activities causing excess ground vibrations leading to failure. Thus, many papers have been published on this issue, yet most of these efforts suffer from complexity and inability to ascertain that all engaged factors are taken into account. These factors are attributed, namely, to explosion source, explosion-ground interaction, energy transfer through the ground, ground-pipeline interaction, and response of the pipeline. The deterministic method developed previously by the author has derived useful prediction mathematical formulas that can be used to calculate, either the stand-off distance of purposefully used explosives, or the maximum quantity of explosives to be used at a given distance, or the equivalent stress of a pipeline induced by an explosive charge at a given standoff distance. The method can also be applied to accidental blast events in factories or other activities. Yet, the complex formulas developed are hard to be used in the field and a simpler approach is needed to facilitate and accelerate in-field estimations. Thus, a nomogram was prepared to make the safety estimations easy and fast and taking into account all engaged critical factors starting from the explosion source through the integrity of the structure.
Given that p-xylene is an important chemical feedstock for many final products in the market from... more Given that p-xylene is an important chemical feedstock for many final products in the market from pesticides, pharmaceuticals, peroxides to dyes, its chlorinated derivatives are of interest in the chemical industry. In this paper, the rate constant ratios of the consecutive chlorination of p-xylene at 70 • C in a gasliquid semibatch reactor using molecular chlorine and iron(III) chloride as a catalyst was investigated up to the fourth successive reaction (tetrachloro-p-xylene production). The ratios were determined with both mathematical expressions
The determination of rate constants for consecutive irreversible reactions is a difficult and tim... more The determination of rate constants for consecutive irreversible reactions is a difficult and time-consuming problem, especially when the research extends up to many subsequent products. Thus, the derivation of proper mathematical expressions would greatly facilitate the determination of these rate constants when only the rate constant of the first consecutive reaction is known. Many authors have dealt with this problem in the past but the issue is still of interest to the scientific community judging from recent publications. This paper aims at extending our knowledge of mathematical expressions for rate constant ratios of consecutive reactions to more than three reactions, as is the situation now, and offering a simple graphical estimation of the rate constant ratios exploiting the maxima of each intermediate product. Furthermore, the method extends to the derivation of a generic formula for the estimation of the rate constant ratios based on this graphical approach. This approach for the estimation of rate constant ratios based on mathematical expressions and graphical estimations was validated against experimental data found in the literature.
The determination of rate constants for consecutive irreversible reactions is a difficult and tim... more The determination of rate constants for consecutive irreversible reactions is a difficult and time-consuming problem, especially when the research extends up to many subsequent products. Thus, the derivation of proper mathematical expressions would greatly facilitate the determination of these rate constants when only the rate constant of the first consecutive reaction is known. Many authors have dealt with this problem in the past but the issue is still of interest to the scientific community judging from recent publications. This paper aims at extending our knowledge of mathematical expressions for rate constant ratios of consecutive reactions to more than three reactions, as is the situation now, and offering a simple graphical estimation of the rate constant ratios exploiting the maxima of each intermediate product. Furthermore, the method extends to the derivation of a generic formula for the estimation of the rate constant ratios based on this graphical approach. This approach for the estimation of rate constant ratios based on mathematical expressions and graphical estimations was validated against experimental data found in the literature.
Efficient software was used for the comparison of five alternative scenarios for the treatment of... more Efficient software was used for the comparison of five alternative scenarios for the treatment of cheese whey wastewater resulting from a Cheddar cheese factory. Scenario 1 deals with a cheese whey wastewater treatment plant that produces butter, whey protein concentrate and food-grade ethanol. In scenario 2 the butter-making section is similar to the basic process (scenario 1) with some differences
Polymeric Hydrogels were prepared with the capacity to absorb quantities of water multiple times ... more Polymeric Hydrogels were prepared with the capacity to absorb quantities of water multiple times their weight. A technique of trapping the water-soluble fertilizers of the trade, with the ability to convert them into Controlled-Release Fertilizers (CRF), has also been developed. In this research a comparative testing of these materials and of their equivalent commercial water-soluble fertilizers was held out. A tomato growth experiment in closed pots was carried out for this purpose. Two different types of fertilizers were used, that is the CRFs we prepared and their equivalent water-solubles of the trade, in two different doses (N,P,K). The fertilizations were combined with dry mass polymeric hydrogel mixed with the soil in two levels, 0% and 0.2%. During the experiment that lasted for 14 weeks, there were four samplings of leaves to determine the levels of the N,P,K. At the end of the experiment, the plant yield was measured on a dry mass basis. The findings showed that the additi...
Technium Romanian Journal of Applied Sciences and Technology
In the science or industrial practice of chemical processes, iron (III) is sometimes used as a ca... more In the science or industrial practice of chemical processes, iron (III) is sometimes used as a catalyst in organic compound chlorinations due to its effectiveness and low cost. Thus, a fast and easy method of determination in the system is useful especially when metallic iron is used as a precursor which is readily converted into iron (III) chloride by the gaseous chlorine used in the chlorination reactor. In the latter case, the determination of the produced catalytically effective iron (III) is a prerequisite for controlling the kinetic progress of chlorination. In this work, a method for the spectrophotometric determination of iron (III) chloride in organic media after complexation with methyl ethyl ketone is investigated. The formation of a strong o-complex of iron (III) with methyl ethyl ketone allows direct determination of iron at 360 nm.Beer’s law is valid up to absorbance 2.42, where the iron (III) concentration is 20.7 mg·L-1, with molar absorptivity (e) equal to 6.532×103...
The biodegradation of Lindane by the edible fungus Pleurotus ostreatus was studied in a soil-stra... more The biodegradation of Lindane by the edible fungus Pleurotus ostreatus was studied in a soil-straw bench-scale system. A fractional orthogonal Central Composite Design of Experiments (2 5-1 ) was applied to construct second order response surfaces with lag time, Biodegradation rate, Massive Growth rate, Biomass/Growth as optimization parameters. Temperature, air humidity, straw content, Lindane content and nitrogen content were used as design factors. The dependence of all responses on factors found was used to locate optimal conditions after mathematically treatment of the results of experimentation.
Journal of Loss Prevention in the Process Industries, May 1, 1998
... conditions explosive substances. Many accidental explosions in nitration industrial plants ha... more ... conditions explosive substances. Many accidental explosions in nitration industrial plants have been reported in the literature ([Evans et al., 1977], [SAFEX, 1987], [Urbanski, 1965], [Dolah, 1963] and [Fritz, 1969]). Nitric esters ...
Dyes released by the textile industries pose a threat to the public and environmental safety. Cur... more Dyes released by the textile industries pose a threat to the public and environmental safety. Currently, removal of dyes from effluents is accomplished by physico-chemical processes. Such methods are often very costly and although the dyes are removed, accumulation of concentrated wastes creates a disposal problem. Degradation of textile dyes through biological means has gained momentum as these are cheap and eco-friendly technology. The aim of the present study was to investigate and validate the process of decolorizing eight textile dyes by screening eleven basidiomycetes strains, belonging to the white-rot fungi genera Pleurotus, Ganoderma and Lentinula.
Microorganisms were isolated from the environment and cultivated in specific media that induce ca... more Microorganisms were isolated from the environment and cultivated in specific media that induce calcium carbonate precipitation. The formation of crystals was monitored with optical microscope and Scanning Electron Microscopy. Furthermore, X-ray Diffraction was utilized in order to verify the composition of the crystals formed. Here, we report preliminary results that indicate the pluralism of crystal structures that different microorganisms may develop under identical conditions, indicating their potential implementation towards the development of a bioremediation technique for monument protection.
ABSTRACT Many reports have shown that extracellular peroxidases and laccases oxidize persistent o... more ABSTRACT Many reports have shown that extracellular peroxidases and laccases oxidize persistent organic pollutants. In this study, the ligninolitic activities of selected strains were determined in a nitrogen-sufficient liquid medium. In order to determine the effect of temperature on ligninolytic activities, selected white rot fungi were incubated at different temperatures (15, 20, 25 and 30οC). The activities of manganese peroxidase and laccase were determined but no lignin peroxidase was detected for all strains. Significant differences were revealed among strains of the same species. The maximum laccase and manganese peroxidase activity was obtained by Pleurotus ostreatus sp.3 attaining 27.8 and 26 U/l after 11 and 13 days of cultivation at 30οC.
This paper deals with the computational simulation of atmospheric cloud dispersion resulting from... more This paper deals with the computational simulation of atmospheric cloud dispersion resulting from liquefied gas spills. Experimental data were taken from the Coyote series trials that involved large scale cryogenic natural gas releases. The data were used for checking ...
A commercial strain of the fungus Pleurotus ostreatus was used to mediate the degradation of lind... more A commercial strain of the fungus Pleurotus ostreatus was used to mediate the degradation of lindane, by landfarming technology during a 4 weeks statistical experiment. The Multilevel Factorial Design was used with two design factors, namely, straw content X 1 (%) and lindane content X 2 (ppm). The optimization parameters (responses) investigated were: biodegradation rate Y 1 (μg d −1), biomass growth rate Y 2 (mg d −1), biodegradation/biomass Y 3 (μg mg −1), total organic carbon Y 4 (%), total organic nitrogen Y 5 (%) and total organic carbon/total organic nitrogen Y 6. The optima of the adequate models obtained for the period of 2 and 4-weeks were found. An overall kinetic study, conducted in this work with the aid of experimental design, determined the optimum (maximum) specific lindane degradation rate to be 0.16 g kg −1 month −1 .
Journal of Loss Prevention in the Process Industries, 2006
This paper aims at contributing to the efficient design of explosion protection systems against c... more This paper aims at contributing to the efficient design of explosion protection systems against confined explosions. The issue addressed concerns the quantitative estimation of the protective effect of explosion relief vents in the case of confined explosions inside tunnels. A series of virtual experiments performed by computer simulation, revealed how the number of vents, their diameter, as well as the
The environment is considered the surroundings in which an organism operates, including air, wate... more The environment is considered the surroundings in which an organism operates, including air, water, land, natural resources, flora, fauna, humans and their interrelation. It is this environment which is both so valuable, on the one hand, and so endangered on the other. And it is people who are by and large ruining the environment both for themselves and for all other organisms. This book reviews the latest research in this field which is vital for everyone.
The rate constant ratios of the consecutive chlorination of p-xylene at 70 o C in a gas-liquid se... more The rate constant ratios of the consecutive chlorination of p-xylene at 70 o C in a gas-liquid semibatch reactor using molecular chlorine, dichloroethane as a solvent, and antimony pentachloride as a catalyst was investigated up to the fourth successive reaction (tetrachloro-p-xylene production). The rate ratios were determined with both mathematical expressions and a graphical method proposed recently in the literature by use of the maxima of the successive products. In addition, to this simple method that concerns only one pair of values of products (single-point maximum approach), another novel method is proposed and successfully applied concerning many pairs of corresponding values of intermediate products (multiple points maximum approach). This latter method permits the estimation of uncertainties and propagation of uncertainties that proved the usefulness and the possibilities of determining the parameters based on special points of the kinetic dependencies. The rate ratios found for monochloro-p-xylene (2-chloro-p-xylene), dichloro-p-xylene (the sum of 2,3-dichloro-p-xylene and 2,5-dichloro-p-xylene), trichloro-p-xylene (2,3,5-trichloro-p-xylene), and tetrachloro-p-xylene (2,3,5,6-tetrachloro-p-xylene) are k 2 /k 1 = 0.09741, k 3 /k 1 = 0.002685, and k 4 /k 1 = 0.000499. The ratio of the dichloro-isomers produced was also determined in the initial stages as 3.3 in favor of 2,5-dichloro-p-xylene, which is reasonable since 2,3-dichloro-p-xylene is highly hindered by the adjacent groups on the aromatic nucleus. Nevertheless, as the production of trichloro-p-xylene increased considerably, the proportion of 2,3-dichloro-p-xylene gradually diminished down to complete disappearance. This is attributed to the ease of this isomer to be further chlorinated to trichloroproduct since its available free sites on the nucleus are less hindered compared to 2,5-dichloro-p-xylene. The standard uncertainties of the rate constant ratios, the standard deviation of the means, as well as the expanded uncertainties of the means were calculated and proved statistically accepted. Finally, the propagation of uncertainties for the trichloro-p-xylene was estimated using the partial derivatives of this product for each of the rate constant ratios.
Pressurized gas pipelines may be endangered by accidental or intentional activities causing exces... more Pressurized gas pipelines may be endangered by accidental or intentional activities causing excess ground vibrations leading to failure. Thus, many papers have been published on this issue, yet most of these efforts suffer from complexity and inability to ascertain that all engaged factors are taken into account. These factors are attributed, namely, to explosion source, explosion-ground interaction, energy transfer through the ground, ground-pipeline interaction, and response of the pipeline. The deterministic method developed previously by the author has derived useful prediction mathematical formulas that can be used to calculate, either the stand-off distance of purposefully used explosives, or the maximum quantity of explosives to be used at a given distance, or the equivalent stress of a pipeline induced by an explosive charge at a given standoff distance. The method can also be applied to accidental blast events in factories or other activities. Yet, the complex formulas developed are hard to be used in the field and a simpler approach is needed to facilitate and accelerate in-field estimations. Thus, a nomogram was prepared to make the safety estimations easy and fast and taking into account all engaged critical factors starting from the explosion source through the integrity of the structure.
Given that p-xylene is an important chemical feedstock for many final products in the market from... more Given that p-xylene is an important chemical feedstock for many final products in the market from pesticides, pharmaceuticals, peroxides to dyes, its chlorinated derivatives are of interest in the chemical industry. In this paper, the rate constant ratios of the consecutive chlorination of p-xylene at 70 • C in a gasliquid semibatch reactor using molecular chlorine and iron(III) chloride as a catalyst was investigated up to the fourth successive reaction (tetrachloro-p-xylene production). The ratios were determined with both mathematical expressions
The determination of rate constants for consecutive irreversible reactions is a difficult and tim... more The determination of rate constants for consecutive irreversible reactions is a difficult and time-consuming problem, especially when the research extends up to many subsequent products. Thus, the derivation of proper mathematical expressions would greatly facilitate the determination of these rate constants when only the rate constant of the first consecutive reaction is known. Many authors have dealt with this problem in the past but the issue is still of interest to the scientific community judging from recent publications. This paper aims at extending our knowledge of mathematical expressions for rate constant ratios of consecutive reactions to more than three reactions, as is the situation now, and offering a simple graphical estimation of the rate constant ratios exploiting the maxima of each intermediate product. Furthermore, the method extends to the derivation of a generic formula for the estimation of the rate constant ratios based on this graphical approach. This approach for the estimation of rate constant ratios based on mathematical expressions and graphical estimations was validated against experimental data found in the literature.
The determination of rate constants for consecutive irreversible reactions is a difficult and tim... more The determination of rate constants for consecutive irreversible reactions is a difficult and time-consuming problem, especially when the research extends up to many subsequent products. Thus, the derivation of proper mathematical expressions would greatly facilitate the determination of these rate constants when only the rate constant of the first consecutive reaction is known. Many authors have dealt with this problem in the past but the issue is still of interest to the scientific community judging from recent publications. This paper aims at extending our knowledge of mathematical expressions for rate constant ratios of consecutive reactions to more than three reactions, as is the situation now, and offering a simple graphical estimation of the rate constant ratios exploiting the maxima of each intermediate product. Furthermore, the method extends to the derivation of a generic formula for the estimation of the rate constant ratios based on this graphical approach. This approach for the estimation of rate constant ratios based on mathematical expressions and graphical estimations was validated against experimental data found in the literature.
Efficient software was used for the comparison of five alternative scenarios for the treatment of... more Efficient software was used for the comparison of five alternative scenarios for the treatment of cheese whey wastewater resulting from a Cheddar cheese factory. Scenario 1 deals with a cheese whey wastewater treatment plant that produces butter, whey protein concentrate and food-grade ethanol. In scenario 2 the butter-making section is similar to the basic process (scenario 1) with some differences
Polymeric Hydrogels were prepared with the capacity to absorb quantities of water multiple times ... more Polymeric Hydrogels were prepared with the capacity to absorb quantities of water multiple times their weight. A technique of trapping the water-soluble fertilizers of the trade, with the ability to convert them into Controlled-Release Fertilizers (CRF), has also been developed. In this research a comparative testing of these materials and of their equivalent commercial water-soluble fertilizers was held out. A tomato growth experiment in closed pots was carried out for this purpose. Two different types of fertilizers were used, that is the CRFs we prepared and their equivalent water-solubles of the trade, in two different doses (N,P,K). The fertilizations were combined with dry mass polymeric hydrogel mixed with the soil in two levels, 0% and 0.2%. During the experiment that lasted for 14 weeks, there were four samplings of leaves to determine the levels of the N,P,K. At the end of the experiment, the plant yield was measured on a dry mass basis. The findings showed that the additi...
Technium Romanian Journal of Applied Sciences and Technology
In the science or industrial practice of chemical processes, iron (III) is sometimes used as a ca... more In the science or industrial practice of chemical processes, iron (III) is sometimes used as a catalyst in organic compound chlorinations due to its effectiveness and low cost. Thus, a fast and easy method of determination in the system is useful especially when metallic iron is used as a precursor which is readily converted into iron (III) chloride by the gaseous chlorine used in the chlorination reactor. In the latter case, the determination of the produced catalytically effective iron (III) is a prerequisite for controlling the kinetic progress of chlorination. In this work, a method for the spectrophotometric determination of iron (III) chloride in organic media after complexation with methyl ethyl ketone is investigated. The formation of a strong o-complex of iron (III) with methyl ethyl ketone allows direct determination of iron at 360 nm.Beer’s law is valid up to absorbance 2.42, where the iron (III) concentration is 20.7 mg·L-1, with molar absorptivity (e) equal to 6.532×103...
The biodegradation of Lindane by the edible fungus Pleurotus ostreatus was studied in a soil-stra... more The biodegradation of Lindane by the edible fungus Pleurotus ostreatus was studied in a soil-straw bench-scale system. A fractional orthogonal Central Composite Design of Experiments (2 5-1 ) was applied to construct second order response surfaces with lag time, Biodegradation rate, Massive Growth rate, Biomass/Growth as optimization parameters. Temperature, air humidity, straw content, Lindane content and nitrogen content were used as design factors. The dependence of all responses on factors found was used to locate optimal conditions after mathematically treatment of the results of experimentation.
Journal of Loss Prevention in the Process Industries, May 1, 1998
... conditions explosive substances. Many accidental explosions in nitration industrial plants ha... more ... conditions explosive substances. Many accidental explosions in nitration industrial plants have been reported in the literature ([Evans et al., 1977], [SAFEX, 1987], [Urbanski, 1965], [Dolah, 1963] and [Fritz, 1969]). Nitric esters ...
Dyes released by the textile industries pose a threat to the public and environmental safety. Cur... more Dyes released by the textile industries pose a threat to the public and environmental safety. Currently, removal of dyes from effluents is accomplished by physico-chemical processes. Such methods are often very costly and although the dyes are removed, accumulation of concentrated wastes creates a disposal problem. Degradation of textile dyes through biological means has gained momentum as these are cheap and eco-friendly technology. The aim of the present study was to investigate and validate the process of decolorizing eight textile dyes by screening eleven basidiomycetes strains, belonging to the white-rot fungi genera Pleurotus, Ganoderma and Lentinula.
Microorganisms were isolated from the environment and cultivated in specific media that induce ca... more Microorganisms were isolated from the environment and cultivated in specific media that induce calcium carbonate precipitation. The formation of crystals was monitored with optical microscope and Scanning Electron Microscopy. Furthermore, X-ray Diffraction was utilized in order to verify the composition of the crystals formed. Here, we report preliminary results that indicate the pluralism of crystal structures that different microorganisms may develop under identical conditions, indicating their potential implementation towards the development of a bioremediation technique for monument protection.
ABSTRACT Many reports have shown that extracellular peroxidases and laccases oxidize persistent o... more ABSTRACT Many reports have shown that extracellular peroxidases and laccases oxidize persistent organic pollutants. In this study, the ligninolitic activities of selected strains were determined in a nitrogen-sufficient liquid medium. In order to determine the effect of temperature on ligninolytic activities, selected white rot fungi were incubated at different temperatures (15, 20, 25 and 30οC). The activities of manganese peroxidase and laccase were determined but no lignin peroxidase was detected for all strains. Significant differences were revealed among strains of the same species. The maximum laccase and manganese peroxidase activity was obtained by Pleurotus ostreatus sp.3 attaining 27.8 and 26 U/l after 11 and 13 days of cultivation at 30οC.
This paper deals with the computational simulation of atmospheric cloud dispersion resulting from... more This paper deals with the computational simulation of atmospheric cloud dispersion resulting from liquefied gas spills. Experimental data were taken from the Coyote series trials that involved large scale cryogenic natural gas releases. The data were used for checking ...
A commercial strain of the fungus Pleurotus ostreatus was used to mediate the degradation of lind... more A commercial strain of the fungus Pleurotus ostreatus was used to mediate the degradation of lindane, by landfarming technology during a 4 weeks statistical experiment. The Multilevel Factorial Design was used with two design factors, namely, straw content X 1 (%) and lindane content X 2 (ppm). The optimization parameters (responses) investigated were: biodegradation rate Y 1 (μg d −1), biomass growth rate Y 2 (mg d −1), biodegradation/biomass Y 3 (μg mg −1), total organic carbon Y 4 (%), total organic nitrogen Y 5 (%) and total organic carbon/total organic nitrogen Y 6. The optima of the adequate models obtained for the period of 2 and 4-weeks were found. An overall kinetic study, conducted in this work with the aid of experimental design, determined the optimum (maximum) specific lindane degradation rate to be 0.16 g kg −1 month −1 .
Journal of Loss Prevention in the Process Industries, 2006
This paper aims at contributing to the efficient design of explosion protection systems against c... more This paper aims at contributing to the efficient design of explosion protection systems against confined explosions. The issue addressed concerns the quantitative estimation of the protective effect of explosion relief vents in the case of confined explosions inside tunnels. A series of virtual experiments performed by computer simulation, revealed how the number of vents, their diameter, as well as the
The environment is considered the surroundings in which an organism operates, including air, wate... more The environment is considered the surroundings in which an organism operates, including air, water, land, natural resources, flora, fauna, humans and their interrelation. It is this environment which is both so valuable, on the one hand, and so endangered on the other. And it is people who are by and large ruining the environment both for themselves and for all other organisms. This book reviews the latest research in this field which is vital for everyone.
Uploads
Papers by Fotis Rigas