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Removal and recovery of heavy metal from multi-component metal effluent by reduction crystallization

- Phetla, P.T., Ntuli, F., Muzenda, E.

Parametric effects on leaching behavior of nickel-copper matte in ammonia

- Muzenda, E., Ramatsa, I. M., Ntuli, F., Abdulkareem, A. S., Afolabi, A. S.

The Removal of Cu (II) from aqueous solution using sodium borohydride as a reducing agent

- Sithole, N. T., Ntuli, F., Mashifana, T.

  • Authors: Sithole, N. T. , Ntuli, F. , Mashifana, T.
  • Date: 2018
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/270515 , uj:28754 , Citation: Sithole, N.T., Ntuli, F. & Mashifana, T. 2018. The Removal of Cu (II) from aqueous solution using sodium borohydride as a reducing agent.
  • Description: Abstract: The removal and recovery of metals from wastewater has been a subject of significant importance due the negative impact these toxic metals have on human health and the environment as a result of water and soil pollution. Increased use of the metals and chemicals in the process industries has resulted in generation of large quantity of effluents that contains high level of toxic metals and other pollutants. The objective of this work was to recover of Cu in its elemental form as metallic powder from aqueous solution using NaBH4 as a reducing agent. Reductive precipitation was achieved in a batch reactor at 65oC using Cu powder as a seeding material. This study also investigated the effect of concentration of sodium borohydride (NaBH4) as a reducing agent. The amount of NaBH4 was varied based on mole ratios which are 1:1, 1:0.25 and 1:0.1 to recover Cu from synthetic wastewater. The results obtained showed that sodium borohydride is an effective reducing agent to recover Cu from wastewater. The optimum concentration of NaBH4 that gives the best results the 1:1 molar ratio with over 99% Cu removal.
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An investigation into the effect of temperature on the leaching of copper-matte

- Muzenda, E., Ramatsa, I.M., Ntuli, F., Belaid, M., Tshwabi, P.M

Sulphate removal from acid rock drainage using steel slag

- Ntuli, F., Magwa, N. P.

Development of low content phosphogypsum waste composites modified by lime-fly ash-basic oxygen furnace slag

- Mashifana, T. P., Okonta, F. N., Ntuli, F.

  • Authors: Mashifana, T. P. , Okonta, F. N. , Ntuli, F.
  • Date: 2019
  • Subjects: Phosphogypsum , Hnvironment , Hydration
  • Language: English
  • Type: Article
  • Identifier: http://ujcontent.uj.ac.za8080/10210/363790 , http://hdl.handle.net/10210/297105 , uj:32382 , Citation: Mashifana, T.P., Okonta, F.N. & Ntuli, F. 2019. Development of low content phosphogypsum waste composites modified by lime-fly ash-basic oxygen furnace slag.
  • Description: Abstract: The generation and disposal of phosphogypsum (PG) is a worldwide challenge, due to the environmental pollution posed by the material. The contaminants laden in the material are the major limitations for the utilisation of PG. Other materials considered as wastes such as fly ash (FA) and basic oxygen furnace slag (BOF slag) are generated by numerous industrial activities and disposed into environment. This study investigated the use of three wastes materials for the development of a composite applicable for road construction. Two types of PG were investigated, namely citric acid treated PG (TPG), for the removal of the contaminants and raw PG (RPG). Lower content PG containing 20% and 30% were investigated and modified with FA, Lime (L) and BOF slag. The effect of particle size distribution (PSD) on unconfined compressive strength development, durability of the composites and hydration products contributing to strength development were studied. Modification of PG with FA-L-BOF slag significantly improved the unconfined compressive strength of PG. The PG content of 20% for the RPG and TPG yielded the highest strengths of 7.4 MPa and 5.4 MPa, respectively when cure at elevated temperatures. Normal curing of the composites over 7 days and 28 also showed an increase in strength development. Particle size played a significant role in the unconfined compressive strength development. Kieserite, calcium aluminium sulphate and calcite were the predominant hydration products formed during the curing process.
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Effect of attapulgite calcination on heavymetal adsorption from acid mine drainage

- Falayi, T., Ntuli, F.

  • Authors: Falayi, T. , Ntuli, F.
  • Date: 2014-09-11
  • Subjects: Acid mine drainage , Attapulgite , Calcination , Heavy metal removal
  • Type: Article
  • Identifier: uj:5114 , ISSN 0256-1115 , http://hdl.handle.net/10210/13949
  • Description: Attapulgite calcined at 973.15K was characterized and utilized as an adsorbent for the removal of heavy metals and neutralization of acid mine drainage (AMD) from a gold mine. Batch adsorption experiments were carried out using a thermostatic shaker. Activated attapulgite showed that it can neutralize AMD as it raised the pH from 2.6 to 7.3 after a residence time of 2 h. Metal ion removal after 2 h was 100% for Cu (II), 99.46% for Fe (II), 96.20% for Co (II), 86.92% for Ni (II) and 71.52% for Mn (II) using a 2.5% w/v activated attapulgite loading. The adsorption best fit the Langmuir isotherm; however, Cu (II), Co (II), and Fe (II) data fit the Freundlich isotherm as well. Calcination at 973.15 K resulted in the reduction of the equilibrium residence time from 4 to 2 h, solid loading reduction from 10 to 2.5% m/v and an increase in maximum adsorption capacity compared with unactivated attapulgite.
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Reduction crystallization of Ni, Cu, Fe and Co from a mixed metal effluent

- Phetla, T.P., Ntuli, F., Muzenda, E.

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

- Sithole, N.T., Ntuli, F., Falayi, T.

The geotechnical and microstructural properties of desilicated fly ash lime stabilised expansive soil

- Falayi, T., Okonta, F.N., Ntuli, F.

Effect of ethylene maleic anhydride on the particulate processes during hydrogen reduction of nickel ammine sulphate solutions

- Iloy, R.A., Ntuli, F.

  • Authors: Iloy, R.A. , Ntuli, F.
  • Date: 2016
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/213748 , uj:21191 , Citation: Iloy, R.A & Ntuli, F. 2016. Effect of ethylene maleic anhydride on the particulate processes during hydrogen reduction of nickel ammine sulphate solutions.
  • Description: Abstract: The use of additives in the precipitation of nickel with hydrogen is known to influence the particulate processes and, by extension, powder properties such as morphology, microstructure and particle size distribution. Controlling these properties is crucial for some downstream processes. The present study assesses the effect of ethylene maleic anhydride on the particulate processes taking place during the reduction of nickel ammine sulphate solutions by hydrogen gas. Reactions were carried out in an autoclave operated at 28 bar and 180°C under stirring conditions of 850 rpm. Particulate processes were studied by analysing the particle size distribution and the corresponding normalized moments. These were further validated by scanning electron microscopy and nitrogen physisorption analyses. The powder phase identification and purity were determined by means of X-ray diffraction and X-ray fluorescence, respectively. Ethylene maleic anhydride acted as a growth inhibitor and an anti-agglomerating agent, thus acting as a reduction catalyst by maintaining the available surface area for reduction. The system was dominated by agglomeration at low concentration (2–5 mg/L) of ethylene maleic anhydride while breakage became the dominant particulate process at higher concentration (7–10 mg/L), as validated by scanning electron micrographs.
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Use of desilicated fly ash as an adsorbent for heavy metals in acid mine drainage

- Falayi, T., Ngobeni, V., Ntuli, F.

  • Authors: Falayi, T. , Ngobeni, V. , Ntuli, F.
  • Date: 2015-04-19
  • Subjects: Desilicated fly ash , Adsorption , Acid mine drainage
  • Type: Thesis
  • Identifier: uj:5108 , ISBN 978-988-19988-9-7 , http://hdl.handle.net/10210/13932
  • Description: Desilicated fly ash (DFA), the residue from leaching of silica from fly ash, was used as an adsorbent for metals from acid mine drainage (AMD). DFA was found to be an impure phillipsite K zeolite. Batch adsorption experiments were carried out using a thermoshaker. A 0.6% m/v solid loading of DFA removed over 95% of Mn, Al and Cu from AMD. The adsorption process followed the Langmuir adsorption isotherm model and pseudo second order kinetics. The maximum adsorption capacities for Mn, Al and Cu were 14.3, 7.1 and 7.6 mg/g respectively at 25°C. The adsorption of Mn, Al and Cu onto DFA was found to be endothermic and with a positive entropy energy. The Gibbs free energy for the adsorption was found to be -1.7, -7.0 and -11.2 kJ/mol for Mn, Al and Cu. The preference for adsorption was found to be Cu>Al>Mn.
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Effect of calcium lignosulphonate on the particulate processes during hydrogen reduction of nickel ammine sulphate solutions

- Iloy, R.A., Ntuli, F.

  • Authors: Iloy, R.A. , Ntuli, F.
  • Date: 2016
  • Subjects: Nickel reduction , Calcium lignosulphonate , Precipitation , Crystallization
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/93829 , uj:20396 , Citation: Iloy, R.A. & Ntuli, F. 2016. Effect of calcium lignosulphonate on the particulate processes during hydrogen reduction of nickel ammine sulphate solutions.
  • Description: Abstract: The use of additives in the precipitation of nickel with hydrogen is known to influence the particulate processes and by extension the powder properties such as morphology, microstructure and particle size distribution. Controlling these properties is crucial for some downstream processes. The present study assesses the effect of calcium lignosulphonate on the particulate processes taking place during the reduction of nickel ammine sulphate solutions by hydrogen gas. Reactions were carried out in an autoclave operated at 28 bar and 180°C under stirring conditions of 850 rpm. Particulate processes were studied by analysing the particle size distribution and the corresponding normalized moments. These were further validated by scanning electron microscopy and nitrogen physisorption analyses. The powder phase identification and purity were determined by means of X-ray diffraction and X-ray fluorescence respectively. Calcium lignosulphonate acted as a reduction catalyst, growth promoter and by extension agglomerating agent. At 2, 5 and 7 mg/L of calcium lignosulphonate, the system was found to be dominated by breakage while agglomeration was more pronounced at 10 mg/L, as validated by scanning electron micrographs. Furthermore the use of calcium lignosulphonate resulted in the increase of the reduction rate, indicating that this additive acted as a growth promoter.
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Removal of sulphates from acid mine drainage using desilicated fly ash slag

- Ntuli, F., Falayi, T., Thwanane, U.

Development of lightweight construction blocks by alkaline activation of BOF slag

- Sithole, N. T., Okonta, F., Ntuli, F.

  • Authors: Sithole, N. T. , Okonta, F. , Ntuli, F.
  • Date: 2019
  • Subjects: Basic oxygen furnace slag , Lightweight construction block , Alkaline activation
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/404841 , uj:33969 , Citation: Sithole, N.T., Okonta, F. & Ntuli, F. 2019. Development of lightweight construction blocks by alkaline activation of BOF slag.
  • Description: Abstract: Large quantities of basic oxygen furnace (BOFS) are dumped in landfills of which the available land for land-filling of large quantities of waste is reducing all over the world. It is therefore im-portant to develop processes which beneficiates solid waste; BOF slag specifically. The present study attempts to investigate the potential to synthesize BOF slag based light weight construc-tion blocks. The effects of several factors on the UCS of BOF slag based light weight construc-tion blocks (LWCB) was also investigated. The test variables were molarities of sodium hydrox-ide (NaOH) (5 M, 10 M and 15 M); the solid to liquid ratio (20 %, 25 % and 30 %); the sodium silicate (Na2SiO3) to Na! OH ratio (0.5:1, 1:1, 1.5:1, 2:1, 2.5:1 and 3:1); the curing temperature (40°C, 80°C and 100°C). It was found that optimum synthesis conditions were 5M NaOH, 80°C and 1:1 Sodium Silicate: NaOH ratio. The LWCB composite met the minimum requirements for ASTM C34-13, C129-14a and South African standard (SANS227: 2007).
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Synthesis and evaluation of basic oxygen furnace slag based geopolymers for removal of metals and sulphates from acidic industrial effluent-column study

- Sithole, N.T., Ntuli, F., Okonta, F.

  • Authors: Sithole, N.T. , Ntuli, F. , Okonta, F.
  • Date: 2020
  • Subjects: Basic oxygen furnace slag , Column study , Geopolymers
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/435430 , uj:37731 , Sithole, N.T., Ntuli, F., Okonta, F. 2020: Synthesis and evaluation of basic oxygen furnace slag based geopolymers for removal of metals and sulphates from acidic industrial effluent-column study. DOI: https://doi.org/10.1016/j.jwpe.2020.101518
  • Description: Abstract: , Basic Oxygen furnace slag (BOFS) based geopolymers with open porosity ranging from 21%–57 % and density between 1255 kg/m3-2432 kg/m3 were synthesized. The synthesized geopolymers potential; to be used as attenuators for metal removal and neutralization of Acid Mine Drainage (AMD); were assessed and evaluated through column test studies conducted over a period of 133 days. The results show that BOFS based geopolymer composites can be used as attenuators as over 99 % metals were removed during the first 50 days. The results also revealed that higher porosity promoted greater neutralizing ability by dissolution of soluble salts from the BOFS based geopolymer; which improves the removal efficiencies of sulphates, metals and neutralization of AMD. Characterization of the composites after contact with AMD revealed that gypsum was the main mineral phase in the geopolymers indicating that precipitation was the major mechanism that enhanced metal and sulphates removal. BOFS based geopolymers can be used to replace armoring neutralizing agents such as limestone. The research contributes to sustainable development by addressing the environmental pollution posed by AMD and utilization of BOFS as a medium for remediation of AMD. The utilization of BOFS for remediation of AMD mitigates and responds to the environmental problems and demands associated with such waste.
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Synthesis and evaluation of basic oxygen furnace slag based geopolymers for removal of metals and sulphates from acidic industrial effluent-column study

- Sithole, N. T., Ntuli, F., Okonta, F.

  • Authors: Sithole, N. T. , Ntuli, F. , Okonta, F.
  • Date: 2020
  • Subjects: Basic oxygen furnace slag , Column studyGeopolymers , Geopolymers
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/436153 , uj:37822 , Sithole, N.T., Ntuli, F., Okonta, F. 2020: Synthesis and evaluation of basic oxygen furnace slag based geopolymers for removal of metals and sulphates from acidic industrial effluent-column study. DOI://doi.org/10.1016/j.jwpe.2020.101518
  • Description: Abstract: , Basic Oxygen furnace slag (BOFS) based geopolymers with open porosity ranging from 21%–57 % and density between 1255 kg/m3-2432 kg/m3 were synthesized. The synthesized geopolymers potential; to be used as attenuators for metal removal and neutralization of Acid Mine Drainage (AMD); were assessed and evaluated through column test studies conducted over a period of 133 days. The results show that BOFS based geopolymer composites can be used as attenuators as over 99 % metals were removed during the first 50 days. The results also revealed that higher porosity promoted greater neutralizing ability by dissolution of soluble salts from the BOFS based geopolymer; which improves the removal efficiencies of sulphates, metals and neutralization of AMD. Characterization of the composites after contact with AMD revealed that gypsum was the main mineral phase in the geopolymers indicating that precipitation was the major mechanism that enhanced metal and sulphates removal. BOFS based geopolymers can be used to replace armoring neutralizing agents such as limestone. The research contributes to sustainable development by addressing the environmental pollution posed by AMD and utilization of BOFS as a medium for remediation of AMD. The utilization of BOFS for remediation of AMD mitigates and responds to the environmental problems and demands associated with such waste
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Fixed bed column studies for decontamination of acidic mineral effluent using porous fly ash-basic oxygen furnace slag based geopolymers

- Sithole, N.T., Ntuli, F., Okonta, F.

Mechanical properties and structure of Fly ash modified Basic Oxygen Furnace Slag based geopolymer masonry blocks

- Sithole, N. T., Okonta, F., Ntuli, F.

  • Authors: Sithole, N. T. , Okonta, F. , Ntuli, F.
  • Date: 2020
  • Subjects: Basic oxygen furnace slag , Fly Ash , Geopolymer
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/453509 , uj:40040 , Citation: Sithole, N.T., Okonta, F. & Ntuli, F. 2020. Mechanical properties and structure of Fly ash modified Basic Oxygen Furnace Slag based geopolymer masonry blocks.
  • Description: Abstract: The objective of this research was to investigate the effect of Fly ash as a source of Si and Na on the mechanical performance of the Basic Oxygen Furnace Slag based (BOFS) geopolymer. BOFS has the lowest SiO2, Al2O3, Na2O content compared to other aluminosilicate sources (fly ash, metakaolin, granulated blast furnace slag and mine tailings); which have been used to effectively in geopolymer synthesis. SiO2 and Al2O3, contents of BOFS are respectively 5-7 times and 6-8 times lower than those of fly ash, metakaolin and granulated furnace slag (GBFS). This study evaluated the potential use of fly ash as a source of Si and Al to improve the mechanical performance of a BOFS based geopolymer. The influence of varying amount of Coal Fly Ash (FA) (10–50%) on UCS was studied. The effects of several factors on the UCS of BOFS geopolymer were also investigated. The test variables were molarities of sodium hydroxide (NaOH) (5 M, 10 M and 15 M); the solid to liquid ratio (20 %, 25 % and 30 %); and the curing temperature (20°C, 40°C, 80°C and 100°C). It was established that most favorable conditions for the geopolymer synthesis were FA was 10% of the mixture, 5M NaOH and 80°C curing temperature. Attempts has been made to relate the microstructure of BOFS/FA based composite with properties of geopolymer. Aggregation was identified as the main particulate process as established by the evolution of the particle size distribution (PSD) and its derived moments during the geopolymerisation process. The morphology of the particles appeared flaky and fluffy. The developed composite met the minimum requirement of ASTM C34-13 for a structural clay load bearing non exposed masonry and load bearing exposed side construction masonry.
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Influence of pyrolyzed sludge use as an adsorbent in removal of selected trace metals from wastewater treatment

- Matheri, A. N., Ngila, J. C., Ntuli, F., Eloko, N. S.

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