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A note on the dependence of volatile organic compounds specific retention volumes on temperature

- Muzenda, Edison, Ntuli, Freeman

  • Authors: Muzenda, Edison , Ntuli, Freeman
  • Date: 2011
  • Subjects: Volatile organic compounds , Gas liquid chromatography
  • Type: Article
  • Identifier: uj:6240 , http://hdl.handle.net/10210/8181
  • Description: This study investigated the influence of temperature on the specific retention volumes ( o g V ) of 13 volatile organic compounds (VOCs) in silicon oil as the liquid stationary phase using gas liquid chromatography (GLC). Temperature was varied from 303.15K to 423.15K to allow transport calculations for different seasons. Four PDMS polymers with average molecular weight ranging from 760 to 13 000 were used as solvents. Linear plots of log Vg against 1 T were obtained in all cases permitting predictions and interpolations to temperatures not studied here and also dependable enthalpies and entropies of solute transfer from the mobile phase to the stationary phase can be calculated. The specific retention volumes reported in this work are in agreement with literature for similar systems. Efforts were taken to ensure the best possible accuracy and trace the possible sources of error. We devised a gas liquid chromatographic system which secured a simple retention mechanism and showed reproducible solute retention over a long period of time.
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A study on the performance of sodium mercaptobenzothiazole (NMBT) collector on the flotation of Black Mountain ore

- Ikotun, Adeshina G., Muzenda, Edison, Ntuli, Freeman

  • Authors: Ikotun, Adeshina G. , Muzenda, Edison , Ntuli, Freeman
  • Date: 2012
  • Subjects: Black Mountain ore , Sodium mercaptobenzothiazole , Hydrogen-ion concentration
  • Type: Article
  • Identifier: uj:5329 , ISSN 2277 – 4394 , http://hdl.handle.net/10210/8630
  • 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 was recovered (±78% of the available copper in the ore), as an indication of the performance of NMBT.
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Adsorption of Cu and Ni from AMD using activated bentonite

- Ntuli, Freeman, Falayi, Thabo, Molala, Panelope

Adsorption, kinetic and thermodynamic study of Al, Mn and Fe adsorption with natural attapulgite

- Ntuli, Freeman, Falayi, Thabo, Mabasa, Cyril

  • Authors: Ntuli, Freeman , Falayi, Thabo , Mabasa, Cyril
  • Date: 2015
  • Subjects: Attapulgite , Aluminum , Manganese , Iron , Adsorption
  • Type: Article
  • Identifier: uj:5126 , ISBN 978-1-61804-270-5 , http://hdl.handle.net/10210/14089
  • Description: Natural attapulgite was utilized as an adsorbent for the removal of Al, Fe and Mn from a mixed metal effluent. Adsorption experiments were carried out by agitation of a fixed amount of attapulgite with a fixed volume of effluent waste stream in a thermostatic shaker for varying times. Attapulgite showed that it was capable of neutralising the acidic waste stream effluent as pH after 3 hour rose from 2 to 7.46. 4% solid loading of attapulgite could remove 85% Mn(II), 90% Al(III) and 100% Fe(III) The experimental data best fit Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models and the adsorption mechanism was physisorption. The adsorption process fitted well the pseudo second order kinetics for all metal ions studied. Thermodynamic data showed that Fe(III) and Mn(II) adsorption was thermodynamically spontaneous whilst Al(III) was not thermodynamically spontaneous. The process is endothermic for all metal ions. An increase in temperature resulted in an increase in spontaneity of the adsorption process. An increase in metal concentration resulted in an increase in amount of metal ion adsorbed per unit weight of attapulgite.
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An investigation into the effect of temperature on the leaching of copper-matte

- Muzenda, Edison, Ramatsa, I.M., Ntuli, Freeman, Belaid, Mohamed, Tshwabi, P.M.

  • 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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Analysis of the biogas productivity from dry anaerobic digestion of organic fraction of municipal solid waste

- Matheri, Anthony Njuguna, Sethunya, Vuiswa Lucia, Belaid, Mohamed, Muzenda, Edison, Ntuli, Freeman

Atmospheric oxidative and non-oxidative leaching of Ni-Cu matte by acidified ferric chloride solution

- Sekhukhune, L.M., Ntuli, Freeman, Muzenda, Edison

Characterisation of fruits and vegetables wastes in the city of Johannesburg

- Ayeleru, Olusola Olaitan, Ntuli, Freeman, Mbohwa, Charles

  • Authors: Ayeleru, Olusola Olaitan , Ntuli, Freeman , Mbohwa, Charles
  • Date: 2016
  • Subjects: Fruits , Johannesburg market , Vegetables
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://ujcontent.uj.ac.za8080/10210/388885 , http://hdl.handle.net/10210/214113 , uj:21237 , Citation: Ayeleru, O.O., Ntuli, F & Mbohwa, C. 2016. Characterisation of fruits and vegetables wastes in the city of Johannesburg.
  • Description: Abstract: Municipal solid waste (MSW) composition study is very important as a baseline to utilizing fresh fruit and vegetables (FFVs) wastes in waste to energy (WtE) project. The aim of this paper is to determine the composition of various waste components at the Johannesburg FFVs market. The study was conducted during the summer in 2015 to evaluate the various components of fruit and vegetable wastes (FVWs) generated at the market. This was done in order to evaluate the amount of FVWs that are generated daily at the market as a starting point for waste to energy (WtE) proposition for the City of Johannesburg (CoJ). Two international standards: ASTM D5231-92 - 2008 (American Standard Test Method) and UNEP/IETC -2009 (United Nations Environment Programme/International Environmental Technology Centre) were used as yardsticks for the procedure used. Samples were classified based on their colours; green (vegetables and fruits), blue/purple (vegetables and fruits), tan/brown (vegetables and fruits), yellow/orange (vegetables and fruits), red (vegetables and fruits) and other wastes which include corrugated boxes, metals, woods, plastic crates and other composite wastes. Samples were further classified into 135 classes in which some were not available due to seasonal variation and the samples were manually sorted by hands. From the results of the analysis, fruits constituted 55%, vegetables 38%, corrugated boxes and cartons 3%, metals, plastics, woods and other wastes all constituted 1% each.
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Characterization and pre-treatment of water from the Vaal River

- Vessal, Ali R., Ntuli, Freeman, Ngoie, Sonia K.

  • Authors: Vessal, Ali R. , Ntuli, Freeman , Ngoie, Sonia K.
  • Date: 2015-07-14
  • Subjects: Water quality , Vaal River (South Africa) , Water - Pollution - Control
  • Type: Article
  • Identifier: uj:5242 , http://hdl.handle.net/10210/14842
  • Description: Extensive urbanization, economic development, and industrialization coupled with water wastage are placing increased pressure on the quality of water from the Vaal River system. This research study was carried out to assess the water quality of the Vaal River in terms of physico-chemical parameters and heavy metals concentration. Three (3) locations were identified within the Upper Vaal Water Management Area (WMA) where water samples were collected in the months of July and September 2014. A total of eight water quality parameters namely pH, Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Total Hardness (CaCO3), Chemical Oxygen Demand (COD), Nitrate (NO3-), Phosphate (PO43-), Sulphate (SO42-) and Heavy Metals concentration were measured in the laboratory using standard analytical procedures. Values of measured parameters were then compared with the South African water quality guidelines for domestic use and aquatic ecosystems. The findings showed that all the physico-chemical parameters and heavy metals concentration measured were within the tolerable limits except nitrate which exceeded the recommended limit of 6 mg/l, with values ranging from 30-31 mg/l in July and 19-21 mg/l in September. The analytical data also indicated that after pre-treatment of the water sample by filtration and adsorption, the TSS level, TDS concentration, and nitrate content were significantly lowered. Nitrate was reduced to below the acceptable limit after treatment. It was therefore concluded that the river water in the Upper Vaal Water Management Area was not suitable for domestic purposes without any form of treatment and frequent monitoring of physico-chemical parameters is imperative in order to have a full representation of the variations in the water quality.
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Characterization of effluent from textile wet finishing operations

- Ntuli, Freeman, Ikhu-Omoregbe, Daniel, Kuipa, Pardon K., Muzenda, Edison, Belaid, Mohamed

Cu (II) removal from synthetic waste water by ion exchange process

- Muzenda, Edison, Kabuba, John, Ntuli, Freeman, Mollagee, Mansoor, Mulaba-Bafubiandi, Antoine F.

  • Authors: Muzenda, Edison , Kabuba, John , Ntuli, Freeman , Mollagee, Mansoor , Mulaba-Bafubiandi, Antoine F.
  • Date: 2011
  • Subjects: Clinoptilolite , Ion exchange , Synthetic waste water , Waste water treatment , Heavy metals - Removal
  • Type: Article
  • Identifier: uj:4708 , ISSN 2078-0966 , http://hdl.handle.net/10210/10953
  • Description: The objective of this study was to investigate the potential of acid activated South Africa clinoptilolite as an adsorbent in the ion-exchange process for the removal of cations from aqueous solutions. The kinetic parameters affecting the adsorption of Cu (II) ions were studied. The adsorption of Cu (II) from synthetic waste water was found to be dependent on pH, temperature, contact time and initial adsorbate concentration. The pH was varied from 2.5 to 6 and the optimum pH for Cu (II) removal was found to be 4.0. The removal of Cu (II) ions increased with time and attained saturation in about 60-70 min. The equilibrium data showed that the adsorption was endothermic nature. Kinetics data showed that at higher temperatures, the rate of adsorption is higher for the clinoptilolite natural zeolite and that Langmuir equation successfully described the adsorption process.
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Designing of sampling programmes for industrial effluent monitoring

- Ntuli, Freeman, Kuipa, P.K., Muzenda, Edison

  • Authors: Ntuli, Freeman , Kuipa, P.K. , Muzenda, Edison
  • Date: 2011
  • Subjects: Effluent monitoring , Sampling strategies , Water pollution control , Sampling (Statistics)
  • Type: Article
  • Identifier: uj:5313 , ISSN 0944-1344 , http://hdl.handle.net/10210/7736
  • Description: Monitoring of effluent discharges from industrial establishments discharging directly into municipality sewers is one of the major water pollution control activities conducted by municipalities. For largely industrialised municipalities the task can be quite expensive and not effective if sampling programmes are not properly designed. In most cases samples are randomly collected without proper knowledge of the discharge patterns of various industries. As a result the information obtained does not give a good reflection of the quality of effluent being discharged. These problems can be resolved by adapting a statistical approach to the design of sampling programmes. This approach is useful in determining the frequency of sampling, the number of samples needed to estimate the average concentration of target pollution indicator parameters and the magnitude of the uncertainty involved. The benefits and applications of this approach are demonstrated by a case study presented in this paper. It was found that the number of samples and cost of sample analysis can be greatly reduced by the use of systematic instead of random sampling. The statistical approach greatly improves the estimate of monthly means of pollution indicator parameters and is an effective approach for pollution control when coupled with the “polluter pays principle”.
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Development and size distribution of polystyrene/ZnO nanofillers

- Ayeleru, Olusola Olaitan, Dlova, Sisanda, Ntuli, Freeman, Kupolati, Williams Kehinde, Olubambi, Peter Apata

Effect of curing temperature and particle size distribution on unconfined compressive strength of raw and treated fly ash-lime modified phosphogypsum waste

- Mashifana, Tebogo, Okonta, Felix, Ntuli, Freeman

  • Authors: Mashifana, Tebogo , Okonta, Felix , Ntuli, Freeman
  • Date: 2019
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/402509 , uj:33686 , Citation: Mashifana, T., Okonta, F. & Ntuli, F. 2019. Effect of curing temperature and particle size distribution on unconfined compressive strength of raw and treated fly ash-lime modified phosphogypsum waste.
  • Description: Abstract: Voluminous quantity of phosphogypsum waste is generated by phosphoric acid manufacturing industry. Due to limited technologies available to treat the waste and render it useful, this waste is either landfilled or discharged into the sea in a form of slurry. It is critical that the focus shifts from landfilling or disposal into the sea as this result into environment contamination. This study was carried out to determine applications for raw and treated waste phosphogypsum in building and construction and determine the best conditions to produce the final product. Two significant, readily available waste materials namely phosphogypsum and fly ash were used and blended with hydrated lime. Conditions that yielded best strength from a mixture of phosphogypsum-lime-fly ash specimens were at elevated temperatures. The strengths obtained at the temperature of 80 0C were above the permissible strength for building masonry bricks of 3.5 MPa with unconfined compressive strength up to 4.8 MPa. At lower temperature of 40 0C the optimum strength obtained was at the minimal phosphogypsum content of 30%. The optimum strength was achieved at the PG content of 50% for raw PG and 60% for treated phosphogypsum at elevated temperatures. The strengths obtained for the treated phosphogypsum were lower than the minimum permissible load bearing strength due to the non-uniform particles distribution and the presence of impurities and forces of adhesion between citric acid and phosphogypsum. Increasing the curing temperature also reduced the radionuclides initially present in the raw PG without any prior treatment.
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Effect of pH on the recovery and grade of base metal sulphides (PGMs) by flotation

- Muzenda, Edison, Afolabi, Ayo S., Abdulkareem, Ambali S., Ntuli, Freeman

  • Authors: Muzenda, Edison , Afolabi, Ayo S. , Abdulkareem, Ambali S. , Ntuli, Freeman
  • Date: 2011
  • Subjects: Platinum Group Metals , Metal sulphides , Flotation
  • Type: Article
  • Identifier: uj:4713 , ISSN 2078-0966 , http://hdl.handle.net/10210/10959
  • Description: This study investigated the effect of pH on the recovery and grade of the Platinum Group Metals (PGMs) and base metal sulphides from the UG2 ore of the Bushveld Complex. This was achieved through running a series of test work in a Denver flotation cell at varying pH 6-11 at constant reagent dosage. The UG-2 reef is characterized by two predominant gangue phases i.e. chromite and silicate, that have significantly different physical and chemical properties. The test work was aimed at evaluating which pH gives best recoveries, and finding the effect of the chrome content in these recoveries. A pH of 9 gave the highest recovery compared to other pH ranges. However, the highest PGM grade was attained at a pH of 6 which is slightly acidic. Ideally this trend could be expected since the collectors (xanthates) are more stable in alkaline medium. The higher PGM recovery was also accompanied by higher chrome content as a result of their similar chemical properties.
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Examination of flotation reagents suitable for nickel concentrator plant

- Kabuba, John, Muzenda, Edison, Ntuli, Freeman

  • Authors: Kabuba, John , Muzenda, Edison , Ntuli, Freeman
  • Date: 2011
  • Subjects: Nickel concentrator plant , Flotation reagents - Evaluation , Frother , Magnetic separation
  • Type: Article
  • Identifier: uj:6249 , ISSN 2010-4618 , http://hdl.handle.net/10210/8193
  • Description: Examination of flotation reagents suitable for a nickel concentrator plant was investigated using nickel sulphide ore. A number of different new reagents were examined for the best suit for the nickel concentrator plant. It was found that more nickel was found on the magnetic particles, which were assumed to be mostly pyrrhotite. A dosage of 50 g/t was found to be a suitable dose for the collector Betacol 380 AC and gave the best results, however, it was found to be expensive. Betacol 380 AB was found to be suitable at a dose of 75% g/t. There was no flotation improvement when depressants were used in conjunction with Betacol 380 AC. An activator (copper sulphate) was found to improve the grade of copper, nickel and iron meaning it activated pentlandite. The ions improved the flotability of sulfides at the normal process pH after grinding in steel mill.
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Extraction and precipitation of phosphorous from sewage sludge : a feasibility study.

- Ntuli, Freeman, Falayi, Thabo, Mhlungu, Mbalenhle, Thifhelimbilu, Portia

  • Authors: Ntuli, Freeman , Falayi, Thabo , Mhlungu, Mbalenhle , Thifhelimbilu, Portia
  • Date: 2013
  • Subjects: Sewage sludge , Phosphorous
  • Type: Article
  • Identifier: uj:4855 , http://hdl.handle.net/10210/12531
  • Description: Sewage sludge from ERWAT (East Rand Water Care Company) was investigated to determine its potential as a source of P. The raw sewage sludge was found to be a potential source of P. At least 84% P could be leached from the raw sewage sludge after 60 min using either HCl or H2SO4. Selective precipitation of P as magnesium tetraphosphate could be achieved using ammonia and magnesium oxide to give yield a 92.2% pure magnesium tetraphosphate and 9.8% P.
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Influence of frothers on the flotation of black mountain ore

- Muzenda, Edison, Ikotun, Adeshina G., Ntuli, Freeman

Influence of open porosity, hydration products and extent of hydration on the strength of desilicated lime fly ash composites

- Falayi, Thabo, Okonta, Felix Ndubisi, Ntuli, Freeman

  • Authors: Falayi, Thabo , Okonta, Felix Ndubisi , Ntuli, Freeman
  • Date: 2017
  • Subjects: Multivariate analysis , Hydration products , Open porosity
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/249019 , uj:25908 , Citation: Falayi, T., Okonta, F.N. & Ntuli, F. 2017. Influence of open porosity, hydration products and extent of hydration on the strength of desilicated lime fly ash composites.
  • Description: Abstract: The prediction of strength of lime ash composites is critical for quality control, material performance monitoring and material serviceability limit state. A study was conducted to investigate the influence of open porosity (an index of micro grain alignment and macro particle parking), sum of hydration products and extent of hydration of desilicated fly ash (DFA) on the unconfined compressive strength (UCS) of DFA lime composites. A comparison with as received fly ash (FA) was also done. The wet and dry cycle durability of DFA and as received FA composites was also investigated. The DFA and FA composites were found to have a UCS of 8.6 MPa and 7.9 MPa respectively. The FA composite was found to be more durable than the DFA composite as after 10 wet and dry cycles the composites had a UCS of 3.5 and 1.8 MPa respectively. Statistical correlation between UCS and open porosity, extent of FA/DFA hydration and sum of hydration products was implemented by Multivariate analysis. For both FA and DFA it was observed that the three parameters combined (open porosity, extent of FA/DFA hydration and sum of hydration products) had the greatest influence on the UCS than individually. This study shows that no single parameter on its own can adequately be used to predict UCS of FA/DFA lime composites. Correlation coefficients above 0.98 were found to describe the relationship between the three parameters and UCS for each composite. Thus could account for differences in durability or soaked strength of materials with equal initial dry strength.
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Influence of residence time and fine grinding on PGMS recovery and grade using a float characteristic test rig

- Muzenda, Edison, Kabuba, John, Ntuli, Freeman, Mollagee, Mansoor

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