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Characterization of effluent from textile wet finishing operations

A study of the variables in the optimisation of a platinum precipitation process

  • Authors: Phetla, Tebogo , Muzenda, Edison , Belaid, Mohamed
  • Date: 2010
  • Subjects: Platinum Group Metals (PGM) , Platinum precipitation
  • Type: Article
  • Identifier: uj:4700 , http://hdl.handle.net/10210/10936
  • Description: This study investigated possible ways to improve the efficiency of the platinum precipitation process using ammonium chloride by reducing the platinum content reporting to the effluent. The ore treated consist of five platinum group metals namely, ruthenium, rhodium, iridium, platinum, palladium and a precious metal gold. Gold, ruthenium, rhodium and iridium were extracted prior the platinum precipitation process. Temperature, reducing agent, flow rate and potential difference were the variables controlled to determine the operation conditions for optimum platinum precipitation efficiency. Hydrogen peroxide was added as the oxidizing agent at the temperature of 85-90oC and potential difference of 700-850mV was the variable used to check the oxidizing state of platinum. The platinum was further purified at temperature between 60-65oC, potential difference above 700 mV, ammonium chloride of 200 l, and at these conditions the platinum content reporting to the effluent was reduced to less than 300ppm, resulting in optimum platinum precipitation efficiency and purity of 99.9%.
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An investigation into the effect of temperature on the leaching of copper-matte

  • Authors: Muzenda, Edison , Ramatsa, I.M. , Ntuli, Freeman , Belaid, Mohamed , Tshwabi, P.M.
  • Date: 2011
  • Subjects: Coppermatte leaching - Effect of temperature , Leaching - Effect of temperature
  • Type: Article
  • Identifier: uj:4703 , http://hdl.handle.net/10210/10944
  • Description: A study was carried out to determine the influence of the temperature and the reaction involved on the leaching of coppermatte. Copper (Cu) bearing matte from Impala Refinery (Pty) Ltd was used in the investigation. The experiments were conducted in a leaching cell submerged in a water bath, with ammonia concentrations (leaching solution) of 3.0M, temperature of 50°C, 60°C and 70°C, pH of 11 and for a time period of 130 minutes. Leaching tests indicated that Cu recovery increased in the temperature range 50°C - 60°C, however at a temperature of 70°C Cu recovery decreases because of cementation process as nickel displace copper. The shrinking core model was used to determine if the leaching process was diffusion controlled, or chemical controlled, or even mixed controlled. It was found that the leaching process could not be determined using the shrinking core model due to the cementation process of Cu. It was concluded that an increase in temperature results in an increase in the Cu recovery however the temperature should not be too high as cementation process increase with increasing temperature.
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Estimating the absorption of volatile organic compounds in four biodiesels using the Unifac procedure

  • Authors: Mateescu, Corina M. , Muzenda, Edison , Belaid, Mohamed , Abdulkareem, Saka , Afolabi, Ayo S.
  • Date: 2011
  • Subjects: Biodiesel , Volatile organic compounds , Absorption
  • Type: Article
  • Identifier: http://ujcontent.uj.ac.za8080/10210/363185 , uj:4696 , http://hdl.handle.net/10210/10760
  • Description: This work considered the thermodynamic feasibility of scrubbing volatile organic compounds into biodiesel in view of designing a gas treatment process with this absorbent. A detailed vapour – liquid equilibrium investigation was performed using the original UNIFAC group contribution method. The four biodiesels studied in this work are methyl oleate, methyl palmitate, methyl linolenate and ethyl stearate. The original UNIFAC procedure was used to estimate the infinite dilution activity coefficients of 13 selected volatile organic compounds in the biodiesels. The calculations were done at the VOC mole fraction of 9.213x10-8. Ethyl stearate gave the most favourable phase equilibrium. A close agreement was found between the infinite dilution activity coefficient of toluene found in this work and those reported in literature. Thermodynamic models can efficiently be used to calculate vast amount of phase equilibrium behaviour using limited number of experimental data.
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Feasibility study for a castor oil extraction plant in South Africa

  • Authors: Belaid, Mohamed , Muzenda, Edison , Mitilene, Getrude , Mollagee, Mansoor
  • Date: 2011
  • Subjects: Castor oil extraction
  • Type: Article
  • Identifier: uj:4706 , http://hdl.handle.net/10210/10950
  • Description: A feasibility study for the design and construction of a pilot plant for the extraction of castor oil in South Africa was conducted. The study emphasized the four critical aspects of project feasibility analysis, namely technical, financial, market and managerial aspects. The technical aspect involved research on existing oil extraction technologies, namely: mechanical pressing and solvent extraction, as well as assessment of the proposed production site for both short and long term viability of the project. The site is on the outskirts of Nkomazi village in the Mpumalanga province, where connections for water and electricity are currently underway, potential raw material supply proves to be reliable since the province is known for its commercial farming. The managerial aspect was evaluated based on the fact that the current producer of castor oil will be fully involved in the project while receiving training and technical assistance from Sasol Technology, the TSC and SEDA. Market and financial aspects were evaluated and the project was considered financially viable with a Net Present Value (NPV) of R2 731 687 and an Internal Rate of Return (IRR) of 18% at an annual interest rate of 10.5%. The payback time is 6years for analysis over the first 10 years with a net income of R1 971 000 in the first year. The project was thus found to be feasible with high chance of success while contributing to socio-economic development. It was recommended for lab tests to be conducted to establish process kinetics that would be used in the initial design of the plant.
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Organics – biodiesel systems phase equilibrium computation : part 1

  • Authors: Nkosi, Nhlanhla P. , Mokoena, Phumzile , Muzenda, Edison , Belaid, Mohamed
  • Date: 2011
  • Subjects: Activity coefficient , Group contribution , Phase equilibrium , Solubility , Volatile organic compounds
  • Type: Article
  • Identifier: uj:4675 , http://hdl.handle.net/10210/10444
  • Description: The group contribution concept can be applied in the estimation of thermodynamic properties of pure compounds and mixtures. The Modified UNIFAC (Dortmund) is a successful and well-known group contribution model for phase equilibria prediction. In this paper the application of this model to the phase equilibrium of biodiesel - volatile organic compounds systems was tested. Infinite dilution activity coefficients of 30 selected volatile organic compounds (VOCs) in methyl linoleate and methyl palmitate were estimated. The VOCs groups covered in the selection were alkanes, alkenes, alkynes, aromatics, ethers and ketones. The estimated phase equilibrium is favourable for the absorption of these organics into methyl linoleate. The solubility was found to decrease with increase in molecular weight of the VOCs in each group. Saturation was also found to have an effect on solubility. Experimental data are often not available, at least for preliminary design and feasibility studies of absorption processes, group contribution methods can be utilized to predict the required phase equilibria.
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Phase equilibrium of volatile organic compounds in silicon oil using the UNIFAC procedure : an estimation

  • Authors: Muzenda, Edison , Simate, Geoffrey S. , Belaid, Mohamed , Ntuli, Freeman , Mollagee, Mansoor
  • Date: 2011
  • Subjects: Phase equilibrium , Thermodynamic models , Volatile organic compounds , Polydimethylsiloxane , Silicon oil
  • Type: Article
  • Identifier: uj:4699 , http://hdl.handle.net/10210/10934
  • Description: This paper focuses on the phase equilibrium of volatile organic compounds in silicon oil chemically known as PDMS (polydimethylsiloxane) at infinite dilution. Measurements can be expensive and time consuming, hence the need for thermodynamic models which allow the calculation of the phase equilibrium behavior using a limited number of experimental data. The objective of this study was to predict infinite dilution activity coefficients of selected VOCs (volatile organic compounds) in PDMS using the Original UNIFAC model. The predicted results show that PDMS can be used to abate volatile organic compounds from contaminated air streams. The results obtained in this work are comparable to those obtained by the same authors through measurements such as the static headspace and the dynamic gas liquid chromatographic techniques as well as other literature. Although the UNIFAC group contribution method over estimate the infinite dilution activity coefficients, the results of this work may be applied in preliminary phases of process design, simulation and feasibility studies.
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Reflecting on waste management strategies for South Africa

  • Authors: Muzenda, Edison , Belaid, Mohamed , Mollagee, Mansoor , Motampane, Ntemi , Ntuli, Freeman
  • Date: 2011
  • Subjects: Waste management - South Africa
  • Type: Article
  • Identifier: uj:4710 , ISSN 2078-0966 , http://hdl.handle.net/10210/10956
  • Description: The energy crisis, global warming and a cleaner environment are arguably amongst the most pressing issues at present facing modern society. Before devising a suitable strategy to convert a proportion of the waste into useful product, categorization of waste types is of great significance to any more detailed study. The population of the world continues to grow, as does the average standard of living, increasing demand for food, water and energy which places increasing pressure on the environment. This paper attempts to parameterize waste generation within a South African context in order provide a theoretical foundation for such work to take place. Organic materials, which includes wood, leaves, grass, food, paper, plastic, cotton, synthetic fabrics, sewage sludge, animal remains, bacteria, any carbohydrates or hydrocarbons. These are all materials sent to landfills (with the exception of metal, ceramics and glass). The Gauteng province was chosen for this preliminary study as it constituted 42% of SA’s waste in 2010 making it by far the country’s biggest waste generator. The types of waste that were particularly targeted in lieu of the downstream research endeavoured were medical waste, plastics, tyres and sewage sludge.
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The effect of leaching time and ammonia concentration on the atmospheric leaching of copper

  • Authors: Ntuli, Freeman , Muzenda, Edison , Ramatsa, Ishmael , Belaid, Mohamed , Kabuba, John
  • Date: 2011
  • Subjects: Copper recovery , Leaching , Ammonia concentrations
  • Type: Article
  • Identifier: uj:5319 , ISSN 2010-4618 , http://hdl.handle.net/10210/8195
  • Description: The effects of ammonia concentration and leaching time were investigated to determine the optimum leaching conditions. The experiments were conducted in a leaching cell submerged in a water bath, with ammonia concentrations of 1.5 M, 2.0 M, 2.5 M and 3.0 M and varying leaching time from 0 to 300 min. Ni-Cu matte containing 23% by mass Cu was used in this experimental study. Increase in the concentration of the lixiviant was found to increase recovery when leaching for 130 minutes, with a recovery of 32.86% Cu using 3 M solution of ammonia. An increase in the leaching time resulted in more copper being leached for all lixiviant concentrations. However, leaching with 2 M ammonia solution gave a higher yield of copper compared to higher concentrations. This anomaly could be a result of cementation; Cu is displaced by Ni as Ni is a more electronegative metal than Cu .It was found that at higher concentrations more nickel was extracted.
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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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Influence of structure on fatty acid ester-alkane interactions

  • Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
  • Date: 2012
  • Subjects: Absorption , Activity coefficients , Biodiesel , Esters , Volatile organic compounds
  • Type: Article
  • Identifier: uj:4671 , ISSN 978-988-19252-2-0 , http://hdl.handle.net/10210/10436
  • Description: The activity coefficients of alkane structures in various types of fatty acid ester solvents was measured in order to determine the effect of bond interactions between these two chemical species. It is important to understand the mechanics of these interactions for absorber system design. Activity coefficients were determined by use of a Microsoft Excel spreadsheet designed for this purpose. It was determined that the length of the ester chain, as well as ester chain saturation had an impact on activity coefficients, in that saturated ester chains and longer ester chains yielded lower activity coefficients. Multiple branched cycloalkanes yielded lower activity coefficients than straight chain hydrocarbons and unbranched cycloalkanes. It was also noted that the location of the carboxyl group in the ester chain had no influence on activity coefficients.
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Influence of temperature and molecular structure on organics-biodiesel interactions using group contribution methods

  • Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
  • Date: 2012
  • Subjects: Group contribution method , Phase equilibrium , Solubility , Volatile organic compounds , Absorption , Activity coefficients
  • Type: Article
  • Identifier: uj:4672 , ISBN 978-93-82242-16-1 , http://hdl.handle.net/10210/10437
  • Description: Resulting from the trend of increasingly stringent environmental legislation, the drive to secure environmentally friendly absorption solvents has gained much impetus in recent times. In order to design and operate separation processes units, it is essential that the engineer has accurate and reliable knowledge of the phase equilibrium behaviour of the system in question. Since obtaining experimental data on the system can be time-consuming, the use of thermodynamic models is often useful in obtaining preliminary design and feasibility study information. This work examines the suitability of biodiesel (particularly the constituents methyl palmitate and methyl linolenate) as an absorbent solvent for the recovery of volatile organic compounds (VOCs) from waste process gas streams. In particular, activity coefficients were measured in the dilute region in an attempt to predict the effects of molecular structure and temperature on the solubility of the VOCs in the methyl esters under study. The group contribution methods UNIFAC and Modified UNIFAC Dortmund, set up on Microsoft Excel spreadsheets, were used to predict the required phase equilibrium at infinite dilution. The results obtaine
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Optimization of process parameters for castor oil production

Performance of sodium mercaptobenzothiazole (NMBT) collector on the flotation of Black Mountain ore

  • Authors: Ikotun, Adeshina G. , Muzenda, Edison , Ntuli, Freeman , Belaid, Mohamed
  • Date: 2012
  • Subjects: Black Mountain ore , Copper metal , Sodium mercaptobenzothiazole
  • Type: Article
  • Identifier: uj:4689 , http://hdl.handle.net/10210/10478
  • Description: This paper investigated the performance of Sodium Mercaptobenzothiazole (NMBT) as a collector in the flotation of Black Mountain ore. The ore contains metals such as lead, copper and zinc and the associated minerals of economic importance are chalcopyrite, galena and sphalerite respectively, with traces of silver. The study evaluated the effectiveness of the collector and how pH affects the recovery of minerals in particular copper. The performance of the collector was influenced by mineral surface chemistry. The experimental test work was conducted at varying pH levels using Denver flotation cell in order to investigate the collector performance in a basic medium. The experiments were conducted at two different test runs of slightly basic solutions of pH 8.5 and 9.0. The results of both fresh ore and floated ore samples were analysed using XRF. Although Black mountain ore contains small quantities of copper as compared to other ores, a significant amount w recovered (±78% of the available copper in the ore), as an indication of the performance of NMBT.
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Recovery of aluminium oxide from flint clay through H2SO4 leaching

The removal of Ni, Cu & Fe from a mixed metal system using sodium hypophosphite as a reducing agent

A review of the equations of state and their applicability in phase equilibrium modeling

  • Authors: Ramdharee, Sashay , Muzenda, Edison , Belaid, Mohamed
  • Date: 2013
  • Subjects: Equations of state , Phase equilibrium modeling
  • Type: Article
  • Identifier: uj:4757 , http://hdl.handle.net/10210/11743
  • Description: This short paper reviews the equations of state and their application to phase equilibrium modeling. The strengths, weaknesses and applicability of these equations will be assessed. Our intention is to test the applicability of the Peng Robinson equation of state in the computation of thermodynamic interactions of volatile organic compounds and biodiesel. Thermodynamic models are very useful in phase equilibrium prediction as measurements are costly and time consuming.
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Diisononyl phthalate – organics interactions : a phase equilibrium study using modified UNIFAC models

  • Authors: Pheko, Given T , Muzenda, Edison , Belaid, Mohamed , Mateescu, Corina
  • Date: 2013
  • Subjects: Phase equilibrium , Volatile organic compounds , Diisononyl phthalate , Absorption abatement
  • Type: Article
  • Identifier: uj:4857 , http://hdl.handle.net/10210/12533
  • Description: Volatile organic compounds (VOCs) are a series of organic compounds that readily vaporize at room temperature. When emitted into the environment can affect climate change and plants growth, and cause long term human health risks. Absorption abatement technique has been the most preferred to reduce VOCs from contaminated gaseous streams, hence the need for a polymeric solvent with a greater affinity for end-pipe inventory. This phase equilibrium study investigated the ability of diisononyl phthalate (DINP) as an absorbent to 80 selected VOCs at infinite dilution. The solvent-solute(s) interactions were studied using modified UNIFAC Lyngby and Dortmund group contribution methods, with the latter being consistent and reliable, as its results are related to literature. Alkanes, alkanes, aldehydes and cyclo-alkanes with shorter carbon-chain length are highly soluble in DINP, with their solubility decreasing with increasing molecular weight or size, at infinite dilution. Alkynes, ketones, alcohols and carboxylic acids are less soluble in DINP, as a result of their dominating polarity compared to the DINP non-polarity structure. However, results could be improved with further studies and publication of solvent-solute(s) sub-groups interaction parameters, and thus further development of modified UNIFAC Lyngby model. DINP is a good absorbent for short-chained non-polar VOCs.
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Intermolecular dynamics between aromatic compounds and ester polymeric solvents

  • Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
  • Date: 2013
  • Subjects: Activity coefficients , Aromatic compounds , Solubility , Esters
  • Type: Article
  • Identifier: uj:4836 , http://hdl.handle.net/10210/12484
  • Description: This work focused on the interactions that occur between ester solvents and simple aromatic solutes. Solutes were selected from various functional groups in their simplest form, and predictions of activity coefficients at infinite dilution were made using the Modified UNIFAC Dortmund group contribution model. The model computation was set up on a Microsoft Excel spreadsheet specifically designed for this purpose. For polar aromatic solutes, solubility decreased with increase in size of the ester solvent molecule and the opposite was found to be true for non-polar solutes. For all aromatic/ ester solvent interactions there was a decrease in activity coefficients with an increase in the degree of ester unsaturation.
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Potential and technical basis for utilising coal beneficiation discards in power generation by applying circulating fluidised bed boilers

  • Authors: Belaid, Mohamed , Falcon, Rosemary , Vainikka, Pasi , Patsa, Kamohelo V.
  • Date: 2013
  • Subjects: Coal , Discard coal
  • Type: Article
  • Identifier: uj:4977 , http://hdl.handle.net/10210/13078
  • Description: Coal continues to remain South Africa’s prime energy source with coal fired power generation by ESKOM (62 %) and gasification by SASOL (23 %) leading local coal consumption. Beneficiated coal is also exported (70 million tonnes) while raw sized coal is also consumed for cooking and heating in South Africa’s townships. Discard coal is currently being produced at annual rates in excess of 60 million tonne per annum. This is estimated to have already accumulated to more than 1-billion tonnes. Discard coal is a major concern to the department of mineral and energy regarding the potential environmental impact in the future. It should also be seen as a major resource that could provide economic opportunity. The purpose of this paper is to estimate the production and reservoir volumes of SA coal discards and their technical and economic potential application in large scale power generation through CFB combustion. It was found that whilst discard is a poor material, its varying range in heating value and current production rate makes it a potentially viable material for beneficiation towards electricity generation. It’s been found that beneficiating discard coal could come with some challenges e.g initial costs, but on the other hand it could present techno economic opportunities e.g harnessing new technologies to create employment...
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