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
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Alkenes - ester polymeric solvents thermodynamic interactions - Part 1
- 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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Alkenes - ester polymeric solvents thermodynamic interactions - part 2
- 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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Measurement of infinite dilution activity coefficients of selected environmentally important volatile organic compounds in polydimethylsiloxane using gas – liquid chromatography
- 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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Thermodynamics of Cu (II) adsorption onto South African clinoptilolite from synthetic solution by ion exchange process.
- 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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