Thermodynamics of Cu (II) adsorption onto South African clinoptilolite from synthetic solution by ion exchange process.
- Kabuba, John, Ntuli, Freeman, Muzenda, Edison, Mollagee, Mansoor
- Authors: Kabuba, John , Ntuli, Freeman , Muzenda, Edison , Mollagee, Mansoor
- Date: 2011
- Subjects: Clinoptilolite , Adsorption , Thermodynamics , Langmuir isotherm
- Type: Article
- Identifier: uj:6250 , ISSN 2010-4618 , http://hdl.handle.net/10210/8194
- Description: The adsorption of Cu (II) ions from aqueous solution onto clinoptilolite from synthetic solutions by ion exchange was investigated. The effects of solution pH and temperature were examined. The Langmuir isotherm model was employed to calculate the different thermodynamics parameters. Thermodynamics studies revealed that the adsorption behavior of Cu (II) ions onto clinoptilolite was a spontaneous and endothermic process, resulting in higher adsorption capacities at higher temperatures.
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- Authors: Kabuba, John , Ntuli, Freeman , Muzenda, Edison , Mollagee, Mansoor
- Date: 2011
- Subjects: Clinoptilolite , Adsorption , Thermodynamics , Langmuir isotherm
- Type: Article
- Identifier: uj:6250 , ISSN 2010-4618 , http://hdl.handle.net/10210/8194
- Description: The adsorption of Cu (II) ions from aqueous solution onto clinoptilolite from synthetic solutions by ion exchange was investigated. The effects of solution pH and temperature were examined. The Langmuir isotherm model was employed to calculate the different thermodynamics parameters. Thermodynamics studies revealed that the adsorption behavior of Cu (II) ions onto clinoptilolite was a spontaneous and endothermic process, resulting in higher adsorption capacities at higher temperatures.
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Volatile organic compounds – biphenyl thermodynamic interactions
- Authors: Muzenda, Edison
- Date: 2014
- Subjects: Absorption , Activity coefficient , Phase equilibrium , Volatile organic compounds , Thermodynamics
- Type: Article
- Identifier: uj:4989 , ISSN 2078-0966 , http://hdl.handle.net/10210/13124
- Description: This work focused on the thermodynamic interactions involving volatile organic compounds (VOCs) and biphenyl. The solubility of 60 VOCs in biphenyl was studied using group contribution methods. The modified UNIFAC Dortmund and Lyngby were used to compute the required phase equilibrium in the form of infinite dilution activity coefficients. Six family groups were studied mainly alkanes, alkenes, alkynes, aldehydes, alcohols, and carboxylic acids. The Modified UNIFAC Dortmund performed better than the Modified UNIFAC Lyngby. Biphenyl showed excellent absorption affinity for all VOCs in particular for alkynes and aldehydes. The solubility decreased with increase in VOC molecular weight.
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- Authors: Muzenda, Edison
- Date: 2014
- Subjects: Absorption , Activity coefficient , Phase equilibrium , Volatile organic compounds , Thermodynamics
- Type: Article
- Identifier: uj:4989 , ISSN 2078-0966 , http://hdl.handle.net/10210/13124
- Description: This work focused on the thermodynamic interactions involving volatile organic compounds (VOCs) and biphenyl. The solubility of 60 VOCs in biphenyl was studied using group contribution methods. The modified UNIFAC Dortmund and Lyngby were used to compute the required phase equilibrium in the form of infinite dilution activity coefficients. Six family groups were studied mainly alkanes, alkenes, alkynes, aldehydes, alcohols, and carboxylic acids. The Modified UNIFAC Dortmund performed better than the Modified UNIFAC Lyngby. Biphenyl showed excellent absorption affinity for all VOCs in particular for alkynes and aldehydes. The solubility decreased with increase in VOC molecular weight.
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A revisit and review of experimental variables affecting chromatographic organics - polydimethylsiloxane interactions
- Authors: Muzenda, Edison
- Date: 2012
- Subjects: Absorption , Liquid loading , Polymers , Sorption mechanism , Specific retention volume , Thermodynamics
- Type: Article
- Identifier: uj:5339 , ISSN 2277 – 4394 , http://hdl.handle.net/10210/8909
- Description: Please refer to full text to view abstract
- Full Text:
- Authors: Muzenda, Edison
- Date: 2012
- Subjects: Absorption , Liquid loading , Polymers , Sorption mechanism , Specific retention volume , Thermodynamics
- Type: Article
- Identifier: uj:5339 , ISSN 2277 – 4394 , http://hdl.handle.net/10210/8909
- Description: Please refer to full text to view abstract
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Alkenes - ester polymeric solvents thermodynamic interactions - part 2
- Scheepers, Jacques J., Muzenda, Edison, Belaid, Mohamed
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2012
- Subjects: Activity coefficients , Esters , Alkenes , Thermodynamics
- Type: Article
- Identifier: uj:5341 , http://hdl.handle.net/10210/9581
- Description: This paper is a continuation of our work reported previously [1] on the interaction between ester solvents and alkene volatile organic compounds (VOCs). The interactions were presented inform of infinite dilution activity coefficients. A Microsoft Excel spreadsheet for the modified UNIFAC Dortmund group contribution method [2] was designed and used in computing the required phase equilibrium. The size of the solvent molecule (biodiesel) relative to the VOC molecule influenced the thermodynamic interactions. The degree of ester (biodiesel) bond saturation influenced the ease in which cyclic VOCs interacted with the solvent compared to their straight chain counterparts. The location of branches such as methyl branches in relation to the double-bonded carbons had an impact on the predicted infinite dilution activity coefficients.
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- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2012
- Subjects: Activity coefficients , Esters , Alkenes , Thermodynamics
- Type: Article
- Identifier: uj:5341 , http://hdl.handle.net/10210/9581
- Description: This paper is a continuation of our work reported previously [1] on the interaction between ester solvents and alkene volatile organic compounds (VOCs). The interactions were presented inform of infinite dilution activity coefficients. A Microsoft Excel spreadsheet for the modified UNIFAC Dortmund group contribution method [2] was designed and used in computing the required phase equilibrium. The size of the solvent molecule (biodiesel) relative to the VOC molecule influenced the thermodynamic interactions. The degree of ester (biodiesel) bond saturation influenced the ease in which cyclic VOCs interacted with the solvent compared to their straight chain counterparts. The location of branches such as methyl branches in relation to the double-bonded carbons had an impact on the predicted infinite dilution activity coefficients.
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Alkenes - ester polymeric solvents thermodynamic interactions - Part 1
- Scheepers, Jacques J., Muzenda, Edison
- Authors: Scheepers, Jacques J. , Muzenda, Edison
- Date: 2012
- Subjects: Activity coefficients , Esters , Alkenes , Thermodynamics , Solubility
- Type: Article
- Identifier: uj:6274 , http://hdl.handle.net/10210/8914
- Description: This work focused on the interactions between ester solvents and volatile organic compounds of alkene in nature. Infinite dilution activity coefficients of alkenes in various fatty acid ester solvents were predicted in order to study and thermodynamically understand the nature and effect of the bond interactions involved. Activity coefficients were computed using Microsoft Excel model specifically designed for this purpose. The ester solvent chain length and saturation influenced the solubility of alkene organics. Saturated and longer ester chains gave better absorption performance. Alkenes were found to be more soluble than their alkane counterparts of similar carbon count.
- Full Text:
- Authors: Scheepers, Jacques J. , Muzenda, Edison
- Date: 2012
- Subjects: Activity coefficients , Esters , Alkenes , Thermodynamics , Solubility
- Type: Article
- Identifier: uj:6274 , http://hdl.handle.net/10210/8914
- Description: This work focused on the interactions between ester solvents and volatile organic compounds of alkene in nature. Infinite dilution activity coefficients of alkenes in various fatty acid ester solvents were predicted in order to study and thermodynamically understand the nature and effect of the bond interactions involved. Activity coefficients were computed using Microsoft Excel model specifically designed for this purpose. The ester solvent chain length and saturation influenced the solubility of alkene organics. Saturated and longer ester chains gave better absorption performance. Alkenes were found to be more soluble than their alkane counterparts of similar carbon count.
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Development of a thermoacoustically driven thermoacoustic refrigerator
- Authors: Alcock, Adam Christopher
- Date: 2018
- Subjects: Thermodynamics , Refrigeration and refrigerating machinery
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284748 , uj:30763
- Description: M.Tech. (Mechanical Engineering) , Abstract: Thermoacoustic technology is proposed in this study as an alternative sustainable solution to current issues with vapour compression refrigerators because of its environmentally friendlier attributes. However, the main hindrance to the expansion of this technology is its current lack of efficiency. Hence, three experimental investigations were conducted in this study for three standing wave thermoacoustic systems. The influence of the geometrical configuration of the stack, which is described as the heart of the device, formed the main study of this work. The first device experimentally investigated was a simple thermoacoustic refrigerator. The device was equipped with different selected low-cost porous materials (honeycomb ceramic) for performance testing and studies. Porosity, length and position of the stack were parameters changed in the refrigerator. Sixteen ceramic stacks were considered and evaluated separately. Temperature readings across the stack were used to determine the performance and efficiency of a configuration. In addition, clarity on the relationship between stacks and their frequencies of the sound wave are highlighted The second thermoacoustic device experimentally investigated, was an adjustable thermoacoustic engine. The device incorporated a buffer volume, cooling heat exchanger, heating coil and six different honeycomb ceramic stacks. Stack parameters of two porosities, three lengths and three positions were studied. The pressure inside the engine for two types of gases were evaluated. Measurements of temperature difference across the stack and sound pressure levels were used to determine the performance of the device. Results showed that adjusting the resonator length of the engine changed frequency output. Results obtained in the previous studies aided in the design and construction of an adjustable prototype for a thermoacoustic system which couples the engine to the refrigerator. This device is known as a thermoacoustically driven thermoacoustic refrigerator (TADTAR). A final design was selected from three possible conceptual drawings. Details of the procedure used during the design are provided. The development of the adjustable TADTAR was performed by means of a third and final experiment. The device incorporated two heat exchangers, a heating coil and a stack sample of six different honeycomb ceramics. Stack parameters were changed at the refrigerator and engine. The prototype was pressurised and the operation for two different gases were compared. Measurements of temperature difference across the refrigerator stack were used for performance calculations. Adjusting the resonator length for the operation of the TADTAR had significant results on the performance of the device.
- Full Text:
- Authors: Alcock, Adam Christopher
- Date: 2018
- Subjects: Thermodynamics , Refrigeration and refrigerating machinery
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284748 , uj:30763
- Description: M.Tech. (Mechanical Engineering) , Abstract: Thermoacoustic technology is proposed in this study as an alternative sustainable solution to current issues with vapour compression refrigerators because of its environmentally friendlier attributes. However, the main hindrance to the expansion of this technology is its current lack of efficiency. Hence, three experimental investigations were conducted in this study for three standing wave thermoacoustic systems. The influence of the geometrical configuration of the stack, which is described as the heart of the device, formed the main study of this work. The first device experimentally investigated was a simple thermoacoustic refrigerator. The device was equipped with different selected low-cost porous materials (honeycomb ceramic) for performance testing and studies. Porosity, length and position of the stack were parameters changed in the refrigerator. Sixteen ceramic stacks were considered and evaluated separately. Temperature readings across the stack were used to determine the performance and efficiency of a configuration. In addition, clarity on the relationship between stacks and their frequencies of the sound wave are highlighted The second thermoacoustic device experimentally investigated, was an adjustable thermoacoustic engine. The device incorporated a buffer volume, cooling heat exchanger, heating coil and six different honeycomb ceramic stacks. Stack parameters of two porosities, three lengths and three positions were studied. The pressure inside the engine for two types of gases were evaluated. Measurements of temperature difference across the stack and sound pressure levels were used to determine the performance of the device. Results showed that adjusting the resonator length of the engine changed frequency output. Results obtained in the previous studies aided in the design and construction of an adjustable prototype for a thermoacoustic system which couples the engine to the refrigerator. This device is known as a thermoacoustically driven thermoacoustic refrigerator (TADTAR). A final design was selected from three possible conceptual drawings. Details of the procedure used during the design are provided. The development of the adjustable TADTAR was performed by means of a third and final experiment. The device incorporated two heat exchangers, a heating coil and a stack sample of six different honeycomb ceramics. Stack parameters were changed at the refrigerator and engine. The prototype was pressurised and the operation for two different gases were compared. Measurements of temperature difference across the refrigerator stack were used for performance calculations. Adjusting the resonator length for the operation of the TADTAR had significant results on the performance of the device.
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Attainable regions for optimal reaction networks: application of ΔH-ΔG plot to direct synthesis of dimethyl ether from syngas
- Authors: Paepae, Thulane
- Date: 2015
- Subjects: Heat balance (Engineering) , Chemical processes , Thermodynamics , Thermodynamics - Industrial applications
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213511 , uj:21162
- Description: Abstract: Industrial processes pose a serious threat to the world’s natural resources for they consume them in high proportions as sources of energy for driving chemical processes that provide raw materials for many industrial chemicals. The chemical and petrochemical industries consume about 61% of global industrial energy and emit about 36% of carbon dioxide to the environment. A significant portion of the energy demand is entirely for feedstock, which cannot be reduced through energy efficiency measures. The responsibility therefore for cutting back on the amount of energy needed for chemical processes rests on improving the efficiency of the processes used. The purpose of this research is to demonstrate the use of a novel method of synthesizing process flowsheets, using a graphical tool called the GH-space and in particular to look at how it can be used to compare the reactions of a combined simultaneous process with regard to their thermodynamics. This allows us to synthesize flow-sheets that are reversible and which meet the process targets by implementing mass and energy integration. It also provides guidance on what design decisions would be best suited to developing new processes that are more effective and make lower demands on raw material and energy usage. The approach also provides useful information for evaluating processes through likely limiting extents with respect to the reaction pathways, and comparison between the research findings and their theoretical targets in order to identify any possible energy savings that can be made. The GH-space technique uses fundamental thermodynamic principles to allow the mass, energy and work balances locate the attainable region for chemical processes in a reactor. Furthermore, processes and unit operations can be defined as vectors in the GH-space. Using the targets, one can combine the vector processes in such a way as to approach the target. These vector processes, and the way they are combined, can then be interpreted in terms of flowsheets. This is opposite to what is normally done and allows the process balances to determine what the best flowsheet might look like, allowing for great innovation from the very start of a design. In addition to this, probably the greatest advantage of the GH-space technique is that processes of great complexity can all be analysed on a set of two-dimensional axes. After finding the attainable region, its boundaries can be interpreted in... , M.Tech. (Chemical Engineering)
- Full Text:
- Authors: Paepae, Thulane
- Date: 2015
- Subjects: Heat balance (Engineering) , Chemical processes , Thermodynamics , Thermodynamics - Industrial applications
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213511 , uj:21162
- Description: Abstract: Industrial processes pose a serious threat to the world’s natural resources for they consume them in high proportions as sources of energy for driving chemical processes that provide raw materials for many industrial chemicals. The chemical and petrochemical industries consume about 61% of global industrial energy and emit about 36% of carbon dioxide to the environment. A significant portion of the energy demand is entirely for feedstock, which cannot be reduced through energy efficiency measures. The responsibility therefore for cutting back on the amount of energy needed for chemical processes rests on improving the efficiency of the processes used. The purpose of this research is to demonstrate the use of a novel method of synthesizing process flowsheets, using a graphical tool called the GH-space and in particular to look at how it can be used to compare the reactions of a combined simultaneous process with regard to their thermodynamics. This allows us to synthesize flow-sheets that are reversible and which meet the process targets by implementing mass and energy integration. It also provides guidance on what design decisions would be best suited to developing new processes that are more effective and make lower demands on raw material and energy usage. The approach also provides useful information for evaluating processes through likely limiting extents with respect to the reaction pathways, and comparison between the research findings and their theoretical targets in order to identify any possible energy savings that can be made. The GH-space technique uses fundamental thermodynamic principles to allow the mass, energy and work balances locate the attainable region for chemical processes in a reactor. Furthermore, processes and unit operations can be defined as vectors in the GH-space. Using the targets, one can combine the vector processes in such a way as to approach the target. These vector processes, and the way they are combined, can then be interpreted in terms of flowsheets. This is opposite to what is normally done and allows the process balances to determine what the best flowsheet might look like, allowing for great innovation from the very start of a design. In addition to this, probably the greatest advantage of the GH-space technique is that processes of great complexity can all be analysed on a set of two-dimensional axes. After finding the attainable region, its boundaries can be interpreted in... , M.Tech. (Chemical Engineering)
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Measurement of infinite dilution activity coefficients of selected environmentally important volatile organic compounds in polydimethylsiloxane using gas – liquid chromatography
- Muzenda, Edison, Belaid, M., Ntuli, Freeman
- Authors: Muzenda, Edison , Belaid, M. , Ntuli, Freeman
- Date: 2010
- Subjects: Thermodynamics , Polydimethylsiloxane , Activity coefficients , Volatile organic compounds absorption
- Type: Article
- Identifier: uj:5306 , http://hdl.handle.net/10210/5284
- Description: Silicon oil chemically known as polydimethylsiloxane (PDMS) is a high boiling point solvent highly suitable for volatile organic compounds (VOCs) absorption. In order to use PDMS as an absorption solvent for a specific waste gas problem, it is important to determine the infinite dilution activity coefficients of the VOCs to be separated with PDMS. This work reports activity coefficients at infinite dilution of 13 VOCs in polydimethysiloxane determined by the dynamic gas liquid chromatographic technique. The measurements were carried out at various temperatures (i.e, 303.15, 313.15, 323.15., 333.15, 353.15, 373.15, 393.15 and 423.15K). Four PDMS polymers with average molecular weight ranging from 760 to 13 000 were used as solvents. A control column packed by Perkin Elmer to our specifications was used to validate the coating and packing methods. Flow rate dependence of the elution peaks was also investigated by varying it from 10 – 50 ml/min. Precision was improved by reproducing the results using columns with different liquid loading, thus also studying the retention mechanism. The results compare well with the data from previous work using simple headspace and UNIFAC predictions and literature values. The successful comparison gives an indication of the GLC as a rapid, simple and accurate method for studying the thermodynamics of the interaction of a volatile solute with a non volatile solvent.
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- Authors: Muzenda, Edison , Belaid, M. , Ntuli, Freeman
- Date: 2010
- Subjects: Thermodynamics , Polydimethylsiloxane , Activity coefficients , Volatile organic compounds absorption
- Type: Article
- Identifier: uj:5306 , http://hdl.handle.net/10210/5284
- Description: Silicon oil chemically known as polydimethylsiloxane (PDMS) is a high boiling point solvent highly suitable for volatile organic compounds (VOCs) absorption. In order to use PDMS as an absorption solvent for a specific waste gas problem, it is important to determine the infinite dilution activity coefficients of the VOCs to be separated with PDMS. This work reports activity coefficients at infinite dilution of 13 VOCs in polydimethysiloxane determined by the dynamic gas liquid chromatographic technique. The measurements were carried out at various temperatures (i.e, 303.15, 313.15, 323.15., 333.15, 353.15, 373.15, 393.15 and 423.15K). Four PDMS polymers with average molecular weight ranging from 760 to 13 000 were used as solvents. A control column packed by Perkin Elmer to our specifications was used to validate the coating and packing methods. Flow rate dependence of the elution peaks was also investigated by varying it from 10 – 50 ml/min. Precision was improved by reproducing the results using columns with different liquid loading, thus also studying the retention mechanism. The results compare well with the data from previous work using simple headspace and UNIFAC predictions and literature values. The successful comparison gives an indication of the GLC as a rapid, simple and accurate method for studying the thermodynamics of the interaction of a volatile solute with a non volatile solvent.
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