Adsorption of arsenic on lanthanum and cerium nanoparticles adsorbents during hydrometallurgical extraction of copper
- Authors: Bamidele, Emmanuel Anuoluwa
- Date: 2019
- Subjects: Lanthanum , Copper , Cerium , Nanoparticles , Extraction (Chemistry) , Arsenic - Absorption and adsorption
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/413042 , uj:34782
- Description: M.Tech. (Extraction Metallurgy) , Abstract: Various activities of mining, mineral processing and extraction releases arsenic into the environment. The reported presence of high concentration of arsenic in lakes surrounding a selected silver, cobalt and copper mines has gained serious attention of the scientific community. This research encompasses the characterization of a low-grade copper oxide ore using atomic absorption spectrometer, x-ray fluorescence (XRF), x-ray diffractometer (XRD), SEM-EDS and Induced Coupled Plasma Mass Spectroscopy (ICP-MS). Leaching and adsorption of the copper ore sample was carried out using sulphuric acid of varying molarity -3M, 2M, 1.5M, 1M and 0.5M – and two Lanthanum and Cerium nanoparticles adsorbents were prepared for the adsorption of arsenic from the ore sample during the hydrometallurgical extraction of copper -leaching- process. This study revealed that there is a direct relationship between the concentration of acid and arsenic dissolution. The %As adsorption on Lanthanum nanoparticles adsorbent is lower at higher acid molarity and higher at lower sulphuric acid molarity. While in the case of Cerium adsorbent, there is a deviation. The Cerium ions were able to actively react with arsenic at higher acid molarity hence causing higher adsorption at higher molarity of acid than lower molar mass. Arsenate removal efficiency increases sharply with increasing adsorbent dosage, though there were some anomalies which were observed to be because of competing ions on the adsorption. The increase in temperature was found to reduce the adsorption efficiency of both the Cerium and Lanthanum nanoparticles adsorbents. The effect of acid molarity, adsorbent dosage and temperature were also studied on copper and iron dissolution in the extraction process. Low copper dissolution rate was achieved due to the activation of active binding sites by the Cerium and Lanthanum adsorbents which might have attracted some copper ions. The copper dissolution rate obtained when Cerium impregnated adsorbent was used gave better copper recovery than when Lanthanum adsorbents were applied. The values of RL obtained for each of the adsorption carried out shows that the nature of Langmuir model is unfavourable for Lanthanum nanoparticles, but the linear value obtained for RL in the case of Cerium nanoparticles makes it fit into the model. It is important to note that Cerium nanoparticles adsorbent performs better with increasing acid molarity while Lanthanum nanoparticles adsorbent performs better with increasing adsorbent dosage. Considering the findings obtained from studying different parameters such as acid molarity, temperature and adsorbent dosage, it can be concluded that Cerium nano adsorbent is a better adsorbent than Lanthanum nano adsorbent.
- Full Text:
- Authors: Bamidele, Emmanuel Anuoluwa
- Date: 2019
- Subjects: Lanthanum , Copper , Cerium , Nanoparticles , Extraction (Chemistry) , Arsenic - Absorption and adsorption
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/413042 , uj:34782
- Description: M.Tech. (Extraction Metallurgy) , Abstract: Various activities of mining, mineral processing and extraction releases arsenic into the environment. The reported presence of high concentration of arsenic in lakes surrounding a selected silver, cobalt and copper mines has gained serious attention of the scientific community. This research encompasses the characterization of a low-grade copper oxide ore using atomic absorption spectrometer, x-ray fluorescence (XRF), x-ray diffractometer (XRD), SEM-EDS and Induced Coupled Plasma Mass Spectroscopy (ICP-MS). Leaching and adsorption of the copper ore sample was carried out using sulphuric acid of varying molarity -3M, 2M, 1.5M, 1M and 0.5M – and two Lanthanum and Cerium nanoparticles adsorbents were prepared for the adsorption of arsenic from the ore sample during the hydrometallurgical extraction of copper -leaching- process. This study revealed that there is a direct relationship between the concentration of acid and arsenic dissolution. The %As adsorption on Lanthanum nanoparticles adsorbent is lower at higher acid molarity and higher at lower sulphuric acid molarity. While in the case of Cerium adsorbent, there is a deviation. The Cerium ions were able to actively react with arsenic at higher acid molarity hence causing higher adsorption at higher molarity of acid than lower molar mass. Arsenate removal efficiency increases sharply with increasing adsorbent dosage, though there were some anomalies which were observed to be because of competing ions on the adsorption. The increase in temperature was found to reduce the adsorption efficiency of both the Cerium and Lanthanum nanoparticles adsorbents. The effect of acid molarity, adsorbent dosage and temperature were also studied on copper and iron dissolution in the extraction process. Low copper dissolution rate was achieved due to the activation of active binding sites by the Cerium and Lanthanum adsorbents which might have attracted some copper ions. The copper dissolution rate obtained when Cerium impregnated adsorbent was used gave better copper recovery than when Lanthanum adsorbents were applied. The values of RL obtained for each of the adsorption carried out shows that the nature of Langmuir model is unfavourable for Lanthanum nanoparticles, but the linear value obtained for RL in the case of Cerium nanoparticles makes it fit into the model. It is important to note that Cerium nanoparticles adsorbent performs better with increasing acid molarity while Lanthanum nanoparticles adsorbent performs better with increasing adsorbent dosage. Considering the findings obtained from studying different parameters such as acid molarity, temperature and adsorbent dosage, it can be concluded that Cerium nano adsorbent is a better adsorbent than Lanthanum nano adsorbent.
- Full Text:
Advances in the single-drop micro-extraction pre-concentration technique
- Authors: George, Joseph Mosotho
- Date: 2008-08-15T07:56:19Z
- Subjects: Extraction (Chemistry) , Chromatographic analysis , Pesticides
- Type: Thesis
- Identifier: uj:7909 , http://hdl.handle.net/10210/879
- Description: Pesticide residue analysis is very important both in agriculture and environmental protection. The effectiveness of the analytical method depends very much on the extraction and preconcentration of the analytes prior to the actual analysis, as these analytes occur in trace concentrations that may be lower than the detection limit of the instrument. Various methods of extraction and pre-concentration have been introduced in an effort to decrease costs and other negative environmental impacts without compromising efficiency. One such method is single-drop micro-extraction (SDME), whose benefits cannot be overemphasised. This method has been recently introduced in the pool of pre-concentration methods for pesticide and other organic residues. In this study, the SDME method has been developed using chloroform as a solvent for preconcentration of a ten-component mixture of triazine (TP619) herbicides, followed by analysis by gas chromatography and flame ionisation detector (ppm level detection) and mass spectrometry for detection at sub-ppb level. The developed method uses the simple introduction of an air bubble to the micro-litre droplet of the organic solvent used for extraction of the triazines. This air-bubble showed the increase in the extraction efficiency of the method by about 30% relative to the optimised extraction without the air bubble. The air bubble works very well with addition of the salt (10% NaCl) to the solution being extracted, with further extraction enhancements being observed. Traditionally, the solution being extracted is stirred to achieve good mass transfer. However, the present method does not require stirring as stirring makes the system unstable resulting in reduced precision. The optimum conditions for the newly developed method, named bubble-in-drop single-drop micro-extraction (BID-SDME) were found to be as follows: 1 μL chloroform, 0.5 μL air bubble, 10% NaCl and static equilibration for 20 minutes, while the sample volume is 1 mL. This method showed linearity in the region of 1 ppm to 0.05 ppb (about six orders of magnitude) as long as the instrumental settings were optimised for increased sensitivity. The RSD values observed in this method were better than those recorded in literature, being <10%. Some instrumental manipulations are necessary to realise the full potential of the instrument. Various settings were explored on the GC-MS to optimise its performance below the ppb level. It was observed that the configuration that gave the best sensitivity and the lowest limits of detection was the high-pressure and split-less injection mode. This improved the detection limits of the instrument by 2 orders of magnitude (from 1 ppb to below 0.05 ppb). The GC-MS performance was further improved by the use of selected ion monitoring (SIM) mode of analysis. This technique reduced the interferences from the co-extracted compounds that can compromise the precision and accuracy of the analytical method especially at low concentration applicable in trace analysis. The new BID-SDME method was applied to various samples (dam water, synthetic hard water, dam sediment, humic and sandy soil samples) giving unsurpassed efficiencies with very low RSD values. In these systems, NaCl addition (10% w/v) not only increased extraction efficiency but also had a matrix-normalising effect as the RSD values were reduced and the matrix effects somewhat diminished. The application of this method to orange juice required the addition of only 5% NaCl (not 10% like the other samples). The results obtained with the extraction of orange juice were better than those recorded in literature. The normalising effect was further observed as the RSD values with addition of the NaCl were reduced the RSD from 11.7 (salt-free solution) to 5.56 (5% NaCl). These application experiments were carried out at the 0.2 ppb level using spiked samples. The method was compared against the other extraction techniques used in trace analysis (especially SPME) and it performed better overall giving lower RSD values and much improved detection limits. The calculated detection limits for the ten triazines used in the mixture were in the region of parts per trillion (0.9-14 ppt) with RSD values of < 10% with the use of internal standard. , Prof. D.B.G. Williams Mr. R. Meyer
- Full Text:
- Authors: George, Joseph Mosotho
- Date: 2008-08-15T07:56:19Z
- Subjects: Extraction (Chemistry) , Chromatographic analysis , Pesticides
- Type: Thesis
- Identifier: uj:7909 , http://hdl.handle.net/10210/879
- Description: Pesticide residue analysis is very important both in agriculture and environmental protection. The effectiveness of the analytical method depends very much on the extraction and preconcentration of the analytes prior to the actual analysis, as these analytes occur in trace concentrations that may be lower than the detection limit of the instrument. Various methods of extraction and pre-concentration have been introduced in an effort to decrease costs and other negative environmental impacts without compromising efficiency. One such method is single-drop micro-extraction (SDME), whose benefits cannot be overemphasised. This method has been recently introduced in the pool of pre-concentration methods for pesticide and other organic residues. In this study, the SDME method has been developed using chloroform as a solvent for preconcentration of a ten-component mixture of triazine (TP619) herbicides, followed by analysis by gas chromatography and flame ionisation detector (ppm level detection) and mass spectrometry for detection at sub-ppb level. The developed method uses the simple introduction of an air bubble to the micro-litre droplet of the organic solvent used for extraction of the triazines. This air-bubble showed the increase in the extraction efficiency of the method by about 30% relative to the optimised extraction without the air bubble. The air bubble works very well with addition of the salt (10% NaCl) to the solution being extracted, with further extraction enhancements being observed. Traditionally, the solution being extracted is stirred to achieve good mass transfer. However, the present method does not require stirring as stirring makes the system unstable resulting in reduced precision. The optimum conditions for the newly developed method, named bubble-in-drop single-drop micro-extraction (BID-SDME) were found to be as follows: 1 μL chloroform, 0.5 μL air bubble, 10% NaCl and static equilibration for 20 minutes, while the sample volume is 1 mL. This method showed linearity in the region of 1 ppm to 0.05 ppb (about six orders of magnitude) as long as the instrumental settings were optimised for increased sensitivity. The RSD values observed in this method were better than those recorded in literature, being <10%. Some instrumental manipulations are necessary to realise the full potential of the instrument. Various settings were explored on the GC-MS to optimise its performance below the ppb level. It was observed that the configuration that gave the best sensitivity and the lowest limits of detection was the high-pressure and split-less injection mode. This improved the detection limits of the instrument by 2 orders of magnitude (from 1 ppb to below 0.05 ppb). The GC-MS performance was further improved by the use of selected ion monitoring (SIM) mode of analysis. This technique reduced the interferences from the co-extracted compounds that can compromise the precision and accuracy of the analytical method especially at low concentration applicable in trace analysis. The new BID-SDME method was applied to various samples (dam water, synthetic hard water, dam sediment, humic and sandy soil samples) giving unsurpassed efficiencies with very low RSD values. In these systems, NaCl addition (10% w/v) not only increased extraction efficiency but also had a matrix-normalising effect as the RSD values were reduced and the matrix effects somewhat diminished. The application of this method to orange juice required the addition of only 5% NaCl (not 10% like the other samples). The results obtained with the extraction of orange juice were better than those recorded in literature. The normalising effect was further observed as the RSD values with addition of the NaCl were reduced the RSD from 11.7 (salt-free solution) to 5.56 (5% NaCl). These application experiments were carried out at the 0.2 ppb level using spiked samples. The method was compared against the other extraction techniques used in trace analysis (especially SPME) and it performed better overall giving lower RSD values and much improved detection limits. The calculated detection limits for the ten triazines used in the mixture were in the region of parts per trillion (0.9-14 ppt) with RSD values of < 10% with the use of internal standard. , Prof. D.B.G. Williams Mr. R. Meyer
- Full Text:
Carbonaceous nanomaterials and their conducting polymerbased nanocomposites for the removal of heavy metals from water and the use of metal-loaded adsorbents for gas sensing applications
- Authors: Skosana, Lindiwe
- Date: 2019
- Subjects: Extraction (Chemistry) , Adsorption , Nanocomposites (Materials)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/418824 , uj:35525
- Description: Abstract: The presence of Co2+ and Ni2+ in water is a major concern owing to their non-biodegradable, carcinogenic and mutagenic nature. In recent years, diverse techniques have been applied in their removal from water and upon careful evaluation of some of these techniques, adsorption seemed to be a desirable technique of choice owing to its favourable characteristics as well as its benefits in Co2+ and Ni2+ removal. By virtue of the efficacy of adsorption being governed by an adsorbent, Hollow Carbon Nano Spheres (HCNS) have emerged as attractive adsorbents of choice due to their favourable characteristics in comparison to the adsorbents which have previously been applied in the removal of Co2+and Ni2+ from water... , M.Sc. (Chemistry)
- Full Text:
- Authors: Skosana, Lindiwe
- Date: 2019
- Subjects: Extraction (Chemistry) , Adsorption , Nanocomposites (Materials)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/418824 , uj:35525
- Description: Abstract: The presence of Co2+ and Ni2+ in water is a major concern owing to their non-biodegradable, carcinogenic and mutagenic nature. In recent years, diverse techniques have been applied in their removal from water and upon careful evaluation of some of these techniques, adsorption seemed to be a desirable technique of choice owing to its favourable characteristics as well as its benefits in Co2+ and Ni2+ removal. By virtue of the efficacy of adsorption being governed by an adsorbent, Hollow Carbon Nano Spheres (HCNS) have emerged as attractive adsorbents of choice due to their favourable characteristics in comparison to the adsorbents which have previously been applied in the removal of Co2+and Ni2+ from water... , M.Sc. (Chemistry)
- Full Text:
Critical evaluation and application of sequential extraction for sediment analysis
- Authors: Gouws, Karen
- Date: 2012-08-27
- Subjects: Sedimentation analysis , Extraction (Chemistry) , Water - Analysis
- Type: Thesis
- Identifier: uj:3261 , http://hdl.handle.net/10210/6669
- Description: M.Sc. , Sediment analysis, especially for trace metals, is important since aquatic sediments act as sinks for metals in the environment. Total element analysis yields insufficient information on the bioavailability and the geochemical fate of these metals. Sequential extraction procedures were developed to determine the partitioning of metals in sediment phases. The need for comparability of data produced world-wide led to the development of a sequential extraction procedure, which was proposed by the Community Bureau of Reference as a standard procedure (refered to as the BCR protocol). We contributed to the validation of the BCR procedure by using well-defined in-house model sediments. The results obtained for the model sediments showed that the BCR procedure could distinguish effectively between anthropogenically introduced metals and metals that form part of the mineral structure of the sediment components. The BCR procedure was applied to the sediments of the Vaal Dam and its contributing rivers. The amount of metals extracted in the first three steps of the sequential extraction procedure were low, indicating a very small contribution of anthropogenically introduced metals. It was therefore concluded that these sediments were relatively unpolluted compared to water systems in, for example, Europe.
- Full Text:
- Authors: Gouws, Karen
- Date: 2012-08-27
- Subjects: Sedimentation analysis , Extraction (Chemistry) , Water - Analysis
- Type: Thesis
- Identifier: uj:3261 , http://hdl.handle.net/10210/6669
- Description: M.Sc. , Sediment analysis, especially for trace metals, is important since aquatic sediments act as sinks for metals in the environment. Total element analysis yields insufficient information on the bioavailability and the geochemical fate of these metals. Sequential extraction procedures were developed to determine the partitioning of metals in sediment phases. The need for comparability of data produced world-wide led to the development of a sequential extraction procedure, which was proposed by the Community Bureau of Reference as a standard procedure (refered to as the BCR protocol). We contributed to the validation of the BCR procedure by using well-defined in-house model sediments. The results obtained for the model sediments showed that the BCR procedure could distinguish effectively between anthropogenically introduced metals and metals that form part of the mineral structure of the sediment components. The BCR procedure was applied to the sediments of the Vaal Dam and its contributing rivers. The amount of metals extracted in the first three steps of the sequential extraction procedure were low, indicating a very small contribution of anthropogenically introduced metals. It was therefore concluded that these sediments were relatively unpolluted compared to water systems in, for example, Europe.
- Full Text:
Development and application of molecularly imprinted polymers for selective separation and recovery of gold and silver from industrial wastewaters
- Ahamed, Mohammed Elbushra Hassan
- Authors: Ahamed, Mohammed Elbushra Hassan
- Date: 2018
- Subjects: Extraction (Chemistry) , Heavy metals , Polymers - Separation , Polymers - Analysis
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/261571 , uj:27582
- Description: Ph.D. (Chemistry) , Abstract: Due to the continued global demand for silver and gold, there is constantly a need for more efficient and cost-effective methods to recover these precious metals from industrial aqueous solutions. The recovery of these metals is not easy owing to their presence in complex matrices. As selective recognition elements materials, molecularly imprinted polymers (MIPs) have been attracting great attention for their application in metals extraction. In this research, the performance of imprinted polymers as an adsorbent for the selective recovery of precious metal ions from mining and metallurgical wastewaters was investigated. The imprinted polymers were prepared using various functional monomers (vinylated monomers) and modified chitosan-biopolymers. Various techniques were used to characterize the prepared polymers and to elucidate their interaction mechanisms with the studied precious metal ion. The study also investigated the adsorption behavior of these materials in single and co-adsorption metal ions systems. In the first part of the study, ion-imprinted polymers (IIPs) were prepared by bulk polymerization method using three coordinating monomers namely: 4-vinyl pyridine (4-VP), N-(4-vinyl benzyl) ethylenediamine (EDA) and N-(allyl)-N-diethylthiophosphate (ADT), and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. Comparative studies on the adsorption performance of these IIPs for gold ion were conducted. The results obtained indicated that IIPs containing 4-VP had superior adsorption capability and selectivity towards gold compared to the other IIPs. Molecular modeling, using a Gaussian software package, was used to understand this difference in the adsorption ability. The results obtained indicated that the interaction between gold ion and 4-VP monomer is the strongest (ΔG = -4143.75 kcal mol-1) than its interaction with the other two monomers, suggesting that the adsorption process is more feasible for the IIP derived from 4-VP. FTIR and XRD analysis were done in order to understand and elucidate the adsorption mechanisms. It was proposed that gold ion adsorbed onto IIPs 4-VP and EDA by coordination and ion exchange mechanisms, while complexation – reduction mechanism was the one that accounted for its adsorption onto ADT produced polymeric material. In another attempt, IIPs synthesized from two functional monomers, 4-VP and 1-vinyl imidazole (1-VID), and N, N-ethylene bisacrylamide (EBAm) as the crosslinker via a precipitation polymerization method were found to be suitable for Ag(I) extraction...
- Full Text:
- Authors: Ahamed, Mohammed Elbushra Hassan
- Date: 2018
- Subjects: Extraction (Chemistry) , Heavy metals , Polymers - Separation , Polymers - Analysis
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/261571 , uj:27582
- Description: Ph.D. (Chemistry) , Abstract: Due to the continued global demand for silver and gold, there is constantly a need for more efficient and cost-effective methods to recover these precious metals from industrial aqueous solutions. The recovery of these metals is not easy owing to their presence in complex matrices. As selective recognition elements materials, molecularly imprinted polymers (MIPs) have been attracting great attention for their application in metals extraction. In this research, the performance of imprinted polymers as an adsorbent for the selective recovery of precious metal ions from mining and metallurgical wastewaters was investigated. The imprinted polymers were prepared using various functional monomers (vinylated monomers) and modified chitosan-biopolymers. Various techniques were used to characterize the prepared polymers and to elucidate their interaction mechanisms with the studied precious metal ion. The study also investigated the adsorption behavior of these materials in single and co-adsorption metal ions systems. In the first part of the study, ion-imprinted polymers (IIPs) were prepared by bulk polymerization method using three coordinating monomers namely: 4-vinyl pyridine (4-VP), N-(4-vinyl benzyl) ethylenediamine (EDA) and N-(allyl)-N-diethylthiophosphate (ADT), and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. Comparative studies on the adsorption performance of these IIPs for gold ion were conducted. The results obtained indicated that IIPs containing 4-VP had superior adsorption capability and selectivity towards gold compared to the other IIPs. Molecular modeling, using a Gaussian software package, was used to understand this difference in the adsorption ability. The results obtained indicated that the interaction between gold ion and 4-VP monomer is the strongest (ΔG = -4143.75 kcal mol-1) than its interaction with the other two monomers, suggesting that the adsorption process is more feasible for the IIP derived from 4-VP. FTIR and XRD analysis were done in order to understand and elucidate the adsorption mechanisms. It was proposed that gold ion adsorbed onto IIPs 4-VP and EDA by coordination and ion exchange mechanisms, while complexation – reduction mechanism was the one that accounted for its adsorption onto ADT produced polymeric material. In another attempt, IIPs synthesized from two functional monomers, 4-VP and 1-vinyl imidazole (1-VID), and N, N-ethylene bisacrylamide (EBAm) as the crosslinker via a precipitation polymerization method were found to be suitable for Ag(I) extraction...
- Full Text:
Development of microwave based sample preparation methods for extraction of multi-element for coal clean-up and spectrometric determination
- Authors: Mketo, Nomvano
- Date: 2016
- Subjects: Extraction (Chemistry) , Microwaves - Industrial applications , Coal - Desulfurization
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/124884 , uj:20970
- Description: Abstract: During coal processing such as pyrolysis, liquefaction, gasification and combustion, significant quantities of toxic trace-metals and sulphur can be released into the atmosphere causing severe environmental problems (water, air & soil pollution). Some of these contaminants are corrosive in nature and can cause damages to the combustion reactors which might lead to the reduction of the reactor life span. Additionally, other elements in coal might be trapped inside the combustion boilers and cause slagging, abrasion and fouling. Coal impurities such as trace-metals and sulphur cannot be controlled or prevented as they occur naturally during coal genesis. Therefore, development of analytical procedures is urgently required for determination of coal impurities for future clean-up strategies. Concentration levels of the elemental contaminants in coal must be monitored and controlled in order to determine the coal quality and value. The aim of the current study was to develop cost-effective, novel and environmentally friendly sample preparation procedures based on the use of microwave radiation for quantitative extraction of trace-metals and sulphur in coal samples followed by ICP-MS/OES & IC analysis and coal clean-up approaches. Determination of trace-metals and total sulphur was conducted by using two microwave based methods followed by ICP-MS/OES analysis. The first developed sample preparation procedure was microwave-assisted acid extraction (MW-ADAE) using different dilute inorganic acid and their combination with hydrogen peroxide. Optimisation for trace-metals and total sulphur extraction was conducted by using multivariate and univariate approaches, respectively. In both cases (trace-metals and total sulphur optimisation), results indicated that dilute HNO3-H2O2 was the suitable mixture for simultaneous extraction of 22 elements and total sulphur in coal samples. The use of dilute nitric acid eliminates the carcinogenic nitrous oxides that are produced by concentrated nitric acid (normally used in classic acid digestion methods) and also reduces laboratory waste generated. The MW-ADAE method was then applied in three South African coals coded as coal sample A, B & C (CSA, CSB & CSC) for determination of trace-metals and total sulphur... , Ph.D. (Chemistry)
- Full Text:
- Authors: Mketo, Nomvano
- Date: 2016
- Subjects: Extraction (Chemistry) , Microwaves - Industrial applications , Coal - Desulfurization
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/124884 , uj:20970
- Description: Abstract: During coal processing such as pyrolysis, liquefaction, gasification and combustion, significant quantities of toxic trace-metals and sulphur can be released into the atmosphere causing severe environmental problems (water, air & soil pollution). Some of these contaminants are corrosive in nature and can cause damages to the combustion reactors which might lead to the reduction of the reactor life span. Additionally, other elements in coal might be trapped inside the combustion boilers and cause slagging, abrasion and fouling. Coal impurities such as trace-metals and sulphur cannot be controlled or prevented as they occur naturally during coal genesis. Therefore, development of analytical procedures is urgently required for determination of coal impurities for future clean-up strategies. Concentration levels of the elemental contaminants in coal must be monitored and controlled in order to determine the coal quality and value. The aim of the current study was to develop cost-effective, novel and environmentally friendly sample preparation procedures based on the use of microwave radiation for quantitative extraction of trace-metals and sulphur in coal samples followed by ICP-MS/OES & IC analysis and coal clean-up approaches. Determination of trace-metals and total sulphur was conducted by using two microwave based methods followed by ICP-MS/OES analysis. The first developed sample preparation procedure was microwave-assisted acid extraction (MW-ADAE) using different dilute inorganic acid and their combination with hydrogen peroxide. Optimisation for trace-metals and total sulphur extraction was conducted by using multivariate and univariate approaches, respectively. In both cases (trace-metals and total sulphur optimisation), results indicated that dilute HNO3-H2O2 was the suitable mixture for simultaneous extraction of 22 elements and total sulphur in coal samples. The use of dilute nitric acid eliminates the carcinogenic nitrous oxides that are produced by concentrated nitric acid (normally used in classic acid digestion methods) and also reduces laboratory waste generated. The MW-ADAE method was then applied in three South African coals coded as coal sample A, B & C (CSA, CSB & CSC) for determination of trace-metals and total sulphur... , Ph.D. (Chemistry)
- Full Text:
Investigating the metabolomic dimensions of plant samples through optimization of extraction and chromatographic techniques
- Authors: Masike, Keabetswe
- Date: 2017
- Subjects: Chromatographic analysis - Technique , Metabolites - Analysis , Plant metabolites , Extraction (Chemistry) , Plant extracts
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243960 , uj:25223
- Description: M.Sc. (Biochemistry) , Abstract: Please refer to full text to view abstract
- Full Text:
- Authors: Masike, Keabetswe
- Date: 2017
- Subjects: Chromatographic analysis - Technique , Metabolites - Analysis , Plant metabolites , Extraction (Chemistry) , Plant extracts
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243960 , uj:25223
- Description: M.Sc. (Biochemistry) , Abstract: Please refer to full text to view abstract
- Full Text:
Micro-extraction and detection/quantification of trace pesticides in various matrices
- Authors: George, Joseph Mosotho
- Date: 2012-11-02
- Subjects: Pesticides - Sampling , Environmental sampling , Trace analysis , Extraction (Chemistry)
- Type: Thesis
- Identifier: uj:7323 , http://hdl.handle.net/10210/8060
- Description: Ph.D. , A lot of chemicals are used in agriculture to increase production per cost. Unfortunately most of these chemicals find their way into the final agricultural product or get washed off into other systems where they may pose health and environmental concerns. As such monitoring of these compounds where they are not needed is necessary to avoid unwarranted pollution and the effects associated with them. This requires the use of analytical techniques and instrumentation. Analytical chemistry, especially in the area of sample preparation and clean-up, has shifted focus mainly on greener methods that produce only minute quantities of waste without sacrificing efficiency. This has led to the conception of a term QuEChERS (acronym for Quick, Easy, Cheap, Effective, Robust and Safe) to reflect this trend in sample preparation. Efforts have been made in this regard to reduce the amount of chemicals used; as a result miniaturised techniques have evolved. One such technique that is easiest and cheapest is solvent micro-extraction especially the single-drop format, wherein only a few micro-litres of an organic solvent are used to sample the aqueous solution with the same volume being transferred into the instrument for analysis. This study reports the advances made in development of a modified single-drop micro-extraction (SDME) technique through the deliberate introduction of an air-bubble to facilitate mass transfer. This is termed bubble-in-drop single-drop micro-extraction (BID-SDME). The method has been reported for the first time in our earlier work. This study started off with the validation of the method using triazine mixture (TP 619) as model herbicides. The method was validated for linearity (0.05 – 5 ng/mL), reproducibility and repeatability (%RSD < 10%), matrix effect, limits of detection (pg/mL range) and quantification as well as accuracy.
- Full Text:
- Authors: George, Joseph Mosotho
- Date: 2012-11-02
- Subjects: Pesticides - Sampling , Environmental sampling , Trace analysis , Extraction (Chemistry)
- Type: Thesis
- Identifier: uj:7323 , http://hdl.handle.net/10210/8060
- Description: Ph.D. , A lot of chemicals are used in agriculture to increase production per cost. Unfortunately most of these chemicals find their way into the final agricultural product or get washed off into other systems where they may pose health and environmental concerns. As such monitoring of these compounds where they are not needed is necessary to avoid unwarranted pollution and the effects associated with them. This requires the use of analytical techniques and instrumentation. Analytical chemistry, especially in the area of sample preparation and clean-up, has shifted focus mainly on greener methods that produce only minute quantities of waste without sacrificing efficiency. This has led to the conception of a term QuEChERS (acronym for Quick, Easy, Cheap, Effective, Robust and Safe) to reflect this trend in sample preparation. Efforts have been made in this regard to reduce the amount of chemicals used; as a result miniaturised techniques have evolved. One such technique that is easiest and cheapest is solvent micro-extraction especially the single-drop format, wherein only a few micro-litres of an organic solvent are used to sample the aqueous solution with the same volume being transferred into the instrument for analysis. This study reports the advances made in development of a modified single-drop micro-extraction (SDME) technique through the deliberate introduction of an air-bubble to facilitate mass transfer. This is termed bubble-in-drop single-drop micro-extraction (BID-SDME). The method has been reported for the first time in our earlier work. This study started off with the validation of the method using triazine mixture (TP 619) as model herbicides. The method was validated for linearity (0.05 – 5 ng/mL), reproducibility and repeatability (%RSD < 10%), matrix effect, limits of detection (pg/mL range) and quantification as well as accuracy.
- Full Text:
Recovery of base metals from nitric and sulphiric solutions using carbon nanotubes
- Authors: Mgwetyana, Unathi
- Date: 2014-01-27
- Subjects: Nanotubes , Extraction (Chemistry) , Heavy metals - Absorption and adsorption , Water - Purification - Adsorption
- Type: Thesis
- Identifier: uj:7961 , http://hdl.handle.net/10210/8861
- Description: M.Tech. (Extraction Metallurgy) , For many decades, carbon nanotubes (CNTs) have been used as adsorbents for the removal of pollutants from wastewaters because of their unique properties such as inert surface, resistance to acid and base environment, rigidity and strength. Herein is a report of application of functionalised CNTs on the adsorption of metal ions from aqueous solutions and mine leachates. The CNTs were first synthesised in-house, purified, functionalised and characterised with various characterisation techniques: FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy, TEM (Transmission Electron Microscopy), EDS (Energy Dispersive Spectroscopy), Raman Spectroscopy, TGA (Thermal Gravimetric Analysis) and BET (Brunauer-Emmet-Teller). Together, these techniques gave substantiation for structure, surface and chemical modification of the synthesised moieties. After characterisation, the functional groups were attached to the walls of the tubes and this implies successful functionalisation...
- Full Text:
- Authors: Mgwetyana, Unathi
- Date: 2014-01-27
- Subjects: Nanotubes , Extraction (Chemistry) , Heavy metals - Absorption and adsorption , Water - Purification - Adsorption
- Type: Thesis
- Identifier: uj:7961 , http://hdl.handle.net/10210/8861
- Description: M.Tech. (Extraction Metallurgy) , For many decades, carbon nanotubes (CNTs) have been used as adsorbents for the removal of pollutants from wastewaters because of their unique properties such as inert surface, resistance to acid and base environment, rigidity and strength. Herein is a report of application of functionalised CNTs on the adsorption of metal ions from aqueous solutions and mine leachates. The CNTs were first synthesised in-house, purified, functionalised and characterised with various characterisation techniques: FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy, TEM (Transmission Electron Microscopy), EDS (Energy Dispersive Spectroscopy), Raman Spectroscopy, TGA (Thermal Gravimetric Analysis) and BET (Brunauer-Emmet-Teller). Together, these techniques gave substantiation for structure, surface and chemical modification of the synthesised moieties. After characterisation, the functional groups were attached to the walls of the tubes and this implies successful functionalisation...
- Full Text:
Recovery of Germanium from Copper Slag
- Authors: Kayembe, Junior Ngoyi
- Date: 2019
- Subjects: Germanium , Copper slag , Pyrometallurgy , Extraction (Chemistry)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/445178 , uj:38937
- Description: Abstract: Pyrometallurgy is the most used technology in copper extraction for copper-rich ores by which most of the copper around the world has been produced based on the properties and type of copper ore or concentrates0and working conditions. Pyrometallurgy of nonferrous metals unescapably produces massive amounts of residues in the smelting of which smelter slags are included. These smelter slags, in particular, are dumped continuously in the landscape around the world while they contain valued metals. Due to the valued metals, they are imperative by-products to process as some metal contents such as germanium (Ge) being a trace element in nature has become rare in its available deposits. Therefore, a copper slag from a copper smelter that processed concentrates from different mines has been used0for the recovery of Ge and base metals using the pyrometallurgical approaches. The raw slag was well mixed and characterized using cone blender and X-Ray Fluorescence (XRF), 0X-Ray Diffraction (XRD) and0Scanning Electron Microscopy0Energy Dispersive X-Ray Spectroscopy0(SEM-EDS)... , M.Tech. (Extraction Mettalurgy)
- Full Text:
- Authors: Kayembe, Junior Ngoyi
- Date: 2019
- Subjects: Germanium , Copper slag , Pyrometallurgy , Extraction (Chemistry)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/445178 , uj:38937
- Description: Abstract: Pyrometallurgy is the most used technology in copper extraction for copper-rich ores by which most of the copper around the world has been produced based on the properties and type of copper ore or concentrates0and working conditions. Pyrometallurgy of nonferrous metals unescapably produces massive amounts of residues in the smelting of which smelter slags are included. These smelter slags, in particular, are dumped continuously in the landscape around the world while they contain valued metals. Due to the valued metals, they are imperative by-products to process as some metal contents such as germanium (Ge) being a trace element in nature has become rare in its available deposits. Therefore, a copper slag from a copper smelter that processed concentrates from different mines has been used0for the recovery of Ge and base metals using the pyrometallurgical approaches. The raw slag was well mixed and characterized using cone blender and X-Ray Fluorescence (XRF), 0X-Ray Diffraction (XRD) and0Scanning Electron Microscopy0Energy Dispersive X-Ray Spectroscopy0(SEM-EDS)... , M.Tech. (Extraction Mettalurgy)
- Full Text:
- «
- ‹
- 1
- ›
- »