This study explores the extraction of rare earth elements(REEs)from high-ash run-of-mine and discard coal sourced from the Waterberg Coalfield.Three distinct methods were employed:(1)ultrasonic-assisted caustic digest...This study explores the extraction of rare earth elements(REEs)from high-ash run-of-mine and discard coal sourced from the Waterberg Coalfield.Three distinct methods were employed:(1)ultrasonic-assisted caustic digestion;(2)direct acid leaching;and(3)ultrasonic-assisted caustic-acid leaching.Inductively coupled plasma mass spectrometry was utilized to quantify REEs in both the coals and resultant leachates.Leaching the coals with 40%NaOH at 80℃,along with 40 kHz sonication,yielded a total rare earth element(TREE)recovery of less than 2%.Notable enrichment of REEs was observed in the run-of-mine and discard coal by 17%and 19%,respectively.Upon employing 7.5%HCl,a recovery of less than 11.0%for TREE was achieved in both coal samples.However,leaching the caustic digested coal samples with 7.5%HCl significantly enhanced the TREE recovery to 88.8%and 80.0%for run-of-mine and discard coal,respectively.X-ray diffraction analysis identified kaolinite and quartz as the predominant minerals.Scanning electron microscopyenergy dispersive microanalysis revealed monazite and xenotime as the REE-bearing minerals within the coal samples.These minerals were found either liberated,attached to,or encapsulated by the clay-quartz matrices.Further mineralogical assessments highlighted the increased REE concentrations in coals post-caustic digestion and subsequent recovery during acid leaching.This increase was attributed to the partial dissolution of kaolinite encapsulating the RE-phosphates and the digestion of REE-bearing minerals.Notably,undissolved REE-bearing elements in the caustic-acid-leached coal indicated the necessity of harsh leaching conditions to augment REE recovery from these coal samples.展开更多
Sulfur dioxide (SO2) and nitrogen dioxide (NO2) are some of the air pollutants in industrial and urban areas. These are the most prevalent inorganic pollutants that are a serious risk to public health in populated are...Sulfur dioxide (SO2) and nitrogen dioxide (NO2) are some of the air pollutants in industrial and urban areas. These are the most prevalent inorganic pollutants that are a serious risk to public health in populated areas. However, Lephalale, Polokwane and Steelpoort have not received enough attention to date. Therefore, this study investigated seasonal levels of NO2 and SO2 concentrations using passive sampling during summer, winter, autumn and spring of 2021. The sampling was done the first seven days of the month. The relationship of inorganic pollutants with meteorological factors was performed statistically using multiple linear regression model. Lephalale exhibited the highest NO2 concentration, 1.74 µg/m3, in spring. Whereas Polokwane and Steelpoort peaked at 1.57 µg/m3 and 0.84 µg/m3 in winter, respectively. The concentrations of SO2 were higher in winter than in other seasons in all areas. The multiple linear regression models showed that NO2 and SO2 dispersion was influenced by meteorological parameters such as temperature, wind speed and relative humidity. In Polokwane and Steelpoort, NO2 and SO2 concentrations are inversely correlated to temperature and relative humidity. Similarly, NO2 concentrations are inversely correlated, while SO2 concentrations are directly correlated to both temperature and relative humidity in Lephalale. Wind speed had positive and inverse correlations to the concentrations of both air pollutants. The SO2 and NO2 concentrations did not exceed the annual average of 50 µg/m3 and 94 µg/m3 as set by National Ambient Air Quality Standards and World Health Organization. However, it is important to keep pollution concentrations of SO2 and NO2 to relatively safe for humans and the environment in the studied areas.展开更多
A Longi LGS 500 wet high intensity magnetic separator(WHIMS) was used to concentrate a fine, low grade South African hematite ore. The ore was prepared into different size fractions and was subjected to changes in pul...A Longi LGS 500 wet high intensity magnetic separator(WHIMS) was used to concentrate a fine, low grade South African hematite ore. The ore was prepared into different size fractions and was subjected to changes in pulp density, magnetic field intensity and pulsation frequency which followed a 33 full factorial matrix. The concentrate mass yield and Fe grade were selected as the dependent responses to the changes. The analysis of variance(ANOVA) shows that the variables investigated are significant to the material's response to magnetic separation. This significance was in the order of magnetic field intensity followed by pulsation frequency and then pulp density. It was also noted that a single stage magnetic separation has a potential to upgrade a feed( 75 lm and 40% Fe) to a 55% Fe grade, as the pulsation frequency increases. In addition, the model predictions and actual data were in good agreement, reporting regression coefficients within acceptable ranges.展开更多
Reverse flotation studies on magnetite samples have revealed that the use of starch as a depressant of Fe-oxides has a hydrophilic effect on the surface of Fe-bearing silicates and significantly decreases Fe in the si...Reverse flotation studies on magnetite samples have revealed that the use of starch as a depressant of Fe-oxides has a hydrophilic effect on the surface of Fe-bearing silicates and significantly decreases Fe in the silica-rich stream when used in combination with an amine （Lilaflot D817M）. In this study, the effect of reverse flotation on the optimization of products obtained fi＇om magnetic separation was inves- tigated. Two different magnetic samples, zones 1 and 2, were milled to 〈75 btm and then subjected to low intensity magnetic separation （LIMS）. The LIMS test conducted on the 〈75 ~m shown an upgrade of 46.40wt% Fe, 28.40wt% SiO2 and 2.61wt% MnO for zone 1 and 47.60wt% Fe, 29.17wt% SiO2 and 0.50wt% MnO for zone 2. Further milling of the ore to 〈25 ~tm resulted in a higher magnetic-rich product after magnetic separation. Reverse flotation tests were conducted on the agitated magnetic concentrate feed, and the result shows a significant upgrade of Fe compared to that obtained from the non-agitated feed. Iron concentrations greater than 69%, and SiO2 concentrations less than 2% with overall magnetite recoveries greater than 67% and 71% were obtained for zones 1 and 2, respectively.展开更多
A series of MgO nanoparticles were prepared by first precipitating and isolating Mg(OH)2 nanoparticles from Mg(NO3)2 at three different temperatures using NaOH followed by their thermal decomposition also at three tem...A series of MgO nanoparticles were prepared by first precipitating and isolating Mg(OH)2 nanoparticles from Mg(NO3)2 at three different temperatures using NaOH followed by their thermal decomposition also at three temperature settings. The effects of temperature at which precipitation and thermal decomposition of the hydroxide occurred were studied to assess their influence on nanoparticle size and surface area. The synthesised nanoparticles were characterized using a suite of techniques including Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscope (SEM) analysis. The average diameter range of MgO nanoparticles ranged between 15 and 35 nm, while for the precursor Mg(OH)2 it varied between 28 and 45 nm. The nanoparticle surface area obtained from BET studies was found in all cases to increase from 77 to 106.4 m2/g with increasing temperature of precipitation. Antibacterial activities of the prepared Mg(OH)2 and MgO nanoparticles were evaluated against the Gram-negative bacteria, Escherichia coli, and the Gram-positive bacteria, Staphylococcus aureus, using agar diffusion method. A correlation between surface area and antibacterial activity supported the mechanism of bacterial inactivation as the generation of reactive species. The Mg(OH)2 and MgO nanoparticles both exhibited pronounced bactericidal activity towards the Gram positive bacteria than Gram negative bacteria as indicated by the extend of the zone of inhibition around the nanoparticle.展开更多
The concentration of phosphate flotation concentrate with P2O5 grade lower than the commercially acceptable phosphate quality was upgraded in the use of tribo-electrostatic technique. The concentration of the flotatio...The concentration of phosphate flotation concentrate with P2O5 grade lower than the commercially acceptable phosphate quality was upgraded in the use of tribo-electrostatic technique. The concentration of the flotation concentrate stream was conducted under both triboelectrification and inductive charging mechanism. Mineralogical analysis reveals that the phosphate ore utilized was dominated mainly by fluorapatite, crandallite, wavellite, and with quartz as the major gangue mineral. Flotations concentrate of about 28.87% P2O5 was obtained from the reverse flotation technique, after conditioning the phosphate ore at 80% passing 150 lm under Lilafloat. Constant parameters such as à6 kV charging voltage, 25 kV separating voltage, inlet air, different charger rotary speed and splitter distances were investigated. Commercially accepted grade of 35.50% P2O5 was attained after the second stage of separation with a recovery of 12.26%, another phosphate product of 34.02% P2O5 and 85.19% was also recovered under the same condition. Single stage of separation also shows a significant increase in the grade of the product obtained, with 33.41% P2O5 and 84.07% recovery achievable. The practicability of tribo-electrostatic separation technique for upgrading flotation concentrates resulted in a significant increase in grade for <150 lm product that do not meet the viable grade.展开更多
Colorectal cancer(CRC)is among the leading causes of cancer mortality.The lifetime risk of developing CRC is about 5%in adult males and females.CRC is usually diagnosed at an advanced stage,and at this point therapy h...Colorectal cancer(CRC)is among the leading causes of cancer mortality.The lifetime risk of developing CRC is about 5%in adult males and females.CRC is usually diagnosed at an advanced stage,and at this point therapy has a limited impact on cure rates and long-term survival.Novel and/or improved CRC therapeutic options are needed.The involvement of microRNAs(miRNAs)in cancer development has been reported,and their regulation in many oncogenic pathways suggests their potent tumor suppressor action.Although miRNAs provide a promising therapeutic approach for cancer,challenges such as biodegradation,specificity,stability and toxicity,impede their progression into clinical trials.Nanotechnology strategies offer diverse advantages for the use of miRNAs for CRC-targeted delivery and therapy.The merits of using nanocarriers for targeted delivery of miRNA-formulations are presented herein to highlight the role they can play in miRNA-based CRC therapy by targeting different stages of the disease.展开更多
In this study, synthesis of copper nanoparticles was performed using organoclay as a support to stabilize the nanoparticles. Organoclay amount was gradually increased, which had an effect on the morphology of the resu...In this study, synthesis of copper nanoparticles was performed using organoclay as a support to stabilize the nanoparticles. Organoclay amount was gradually increased, which had an effect on the morphology of the resultant nanoparticles. Low amount of organoclay added resulted in larger and agglomerated copper nanoparticles whereas increased amount of organoclay gave smaller sized nanoparticles. The hybrid materials were characterized using the SEM and TEM for morphology, XRD and FT-IR spectroscopy for structural elucidation, thermal analysis using TGA and also studying their antibacterial effect on the two well-known gram negative bacteria of E. coli and P. Aeruginosa. The synthesized nanoparticles were found to be crystalline Cu nanoparticles with a mix of CuO. Larger sized copper nanoparticles and agglomerates showed the higher thermal behaviour as compared with smaller nanoparticles with higher organoclay loading. The hybrid showed an improved antibacterial activity as compared with organoclay alone. The hybrid showed the higher antibacterial effect against the P. aeruginosa microorganism as compared with the E. coli microorganism.展开更多
Anisotropic gold nanoparticles were synthesized in a simple, environmentally benign process under ambient conditions of temperature and atmospheric pressure using bovine serum albumin (BSA) as both the reductant and b...Anisotropic gold nanoparticles were synthesized in a simple, environmentally benign process under ambient conditions of temperature and atmospheric pressure using bovine serum albumin (BSA) as both the reductant and biotemplate. Two types of anisotropic nanoparticles were produced in the system, namely larger two dimensional plates and smaller three-dimensional nanoparticles. Since the characteristics of nanoparticles are largely determined by their morphology, a simple centrifugation step was included to roughly separate the larger plate-like particles from the smaller more compact particles. In an attempt to identify potential applications, the properties of the particles were determined by TEM, SEM, STEM-EDS, UV-Vis spectroscopy and photoluminescence. The results of this study identified several optical properties of gold nanoparticles.展开更多
Work has been ongoing in building a thermodynamic database for the prediction of phase equilibria in Pt-based superalloys. The alloys are being developed for high texture applications in aggressive environments. The d...Work has been ongoing in building a thermodynamic database for the prediction of phase equilibria in Pt-based superalloys. The alloys are being developed for high texture applications in aggressive environments. The database will aid the design of alloys by enabling the calculation of the composition and proportions of phases present in alloys of different compositions. In order to extend this database, a preliminary assessment of the Cr-Pt-Ru system has been undertaken, using a combination of Pandat and MTDATA software. As a first step, it was necessary to provide thermodynamic models for the three associated binary systems. Owing to a lack of thermodynamic information for these systems, the binary assessments were based on phase diagrams available in the literature. Using recent experimental phase equilibria data for the ternary system, a preliminary assessment of the Cr-Pt-Ru system has been produced. In this preliminary assessment, simplified models were employed for the L12 and sigma phases with a view to extending the descriptions as new experimental information becomes available.展开更多
Although PVDF flat sheet membranes have been widely tested in MD,their synthesis and modifications currently require increased use of green and inexpensive materials.In this study,flat sheet PVDF membranes were synthe...Although PVDF flat sheet membranes have been widely tested in MD,their synthesis and modifications currently require increased use of green and inexpensive materials.In this study,flat sheet PVDF membranes were synthesized using phase inversion and water as the pore former.Remarkably,the water added in the casting solution improved the membrane pore sizes;where the maximum pore size was 0.58μm.Also,the incorporation of f-SiO2NPs in the membrane matrix considerably enhanced the membrane hydrophobicity.Specifically,the membrane contact angles increased from 96°to 153°.Additionally,other parameters investigated were mechanical strength and liquid entry pressure(LEP).The maximum recorded values were 2.26 MPa and 239 kPa,respectively.The modified membranes(i.e.,using water as the pore former and f-SiO2NPs)were the most efficient,showing maximum salt rejection of 99.9%and water flux of 11.6 LMH;thus,indicating their capability to be used as efficient materials for the recovery of high purity water in MD.展开更多
In this work,Fe3O4-Al2O3@CNFs nanocomposite was synthesised and used as a nanosorbent in the ultrasound-assisted dispersive magnetic solid phase extraction(UA-DMSPE)of 17-beta estradiol(E2)in wastewater samples.The qu...In this work,Fe3O4-Al2O3@CNFs nanocomposite was synthesised and used as a nanosorbent in the ultrasound-assisted dispersive magnetic solid phase extraction(UA-DMSPE)of 17-beta estradiol(E2)in wastewater samples.The quantification of E2 was achieved using high performance liquid chromatography coupled with diode array detector(HPLC-DAD).Various parameters affecting the efficiency of this sample preparation technique were optimised to achieve excellent sensitivity and high recoveries of E2.Response surface methodology was utilised for optimisation of these parameters.Using the optimised conditions,the linear dynamic range was achieved in the range of 0.1e1000 mgL^-1and the correlation coefficient was found to be 0.9981.The preconcentration factor,enrichment factor,limit of detection(LOD)and limit of quantification(LOQ)were 67,169,0.025 mgL^-1and 0.083 mg L1,respectively.The relative standard deviation(%RSD)for the intraday(n?10)and interday(n?5 working days)were 1.8%and 3.3%,respectively.The developed UA-DMSPE/HPLC-DAD method was applied for the preconcentration and determination of E2 in wastewater samples.The obtained results indicated that E2 was present in the wastewater samples.展开更多
Electrospun cyclodextrin(CD)-based nanofibers with capabilities to remove pollutants from water have been synthesized and characterized.The high-quality nanofibers presented here were synthesized in two simple steps t...Electrospun cyclodextrin(CD)-based nanofibers with capabilities to remove pollutants from water have been synthesized and characterized.The high-quality nanofibers presented here were synthesized in two simple steps that involved in-situ electrospinning of the nanofibers and all nanocomponents,followed by the reduction of silver(Ag+)and iron(Fe3+)ions to nanoparticles using an environmentally benign process that involved irradiation of the electrospun fibers using a tailor-made UV-equipped furnace at low temperatures.In the previously reported study it was observed that Ag and Fe nanoparticles effectively removed a range of different strains of Gram-negative and Gram-positive bacteria from water.As such,this study focused on improving the thermal and mechanical properties of the nanofibers prepared from polymer blends ofβ-CDs with cellulose acetate(CA)and small additions(2 wt%)of functionalized multiwalled carbon nanotubes(fMWCNTs).The electrospinning parameters were varied to determine the optimum conditions for preparation of uniform nonbeaded nanofibers.Bead-free and uniform nanofibers were obtained at a polymer concentration of 32%at the ratio of 1:1β-CDs:CA,syringe injection flow rate of 0.7 mL h−1,15 cm between the tip of the spinneret and the collector,and a voltage of 16 kV.The addition of f-MWCNTs was found to improve the tensile strength of the nanofibers by twofold,relative to nanofibers with no f-MWCNTs.The thermal degradation of the nanofibers was improved by a magnitude of 50°C.The study has shown that adding small amounts of f-MWCNTs improved the thermal stability and mechanical strength of the CD/CA nanofibers significantly.展开更多
This study reports the removal of amoxicillin from environmental water matrices using zinc oxide coated carbon nanofibers composite as an adsorbent.The structural and surface properties of zinc oxide coated carbon nan...This study reports the removal of amoxicillin from environmental water matrices using zinc oxide coated carbon nanofibers composite as an adsorbent.The structural and surface properties of zinc oxide coated carbon nanofiber composite were characterized using X-ray diffraction,scanning electron microscopy/energy dispersion x-ray spectroscopy,transmission electron microscopy,and Fourier transform infrared spectroscopy.The factors(sample pH and dosage)influencing the adsorption experiments were optimised using central composite design.Freundlich,Langmuir and Flory-Huggin isotherm models were used to study the adsorption isotherms.The results obtained revealed that the maximum adsorption capacity was up to 156 mg g^-1.The kinetic studies demonstrated that the adsorption process was best described by pseudo-second-order model and the equilibrium data followed Langmuir isotherm model.The optimised batch method was then applied for the removal of amoxicillin in real wastewater samples.In addition,the zinc oxide coated carbon nanofibers nanocomposite was found to reusable up to fifteen cycles.展开更多
基金The research was also supported by the National Research Foundation(NRF)of South Africa's SARChI Clean Coal Technology Grant(86421)。
文摘This study explores the extraction of rare earth elements(REEs)from high-ash run-of-mine and discard coal sourced from the Waterberg Coalfield.Three distinct methods were employed:(1)ultrasonic-assisted caustic digestion;(2)direct acid leaching;and(3)ultrasonic-assisted caustic-acid leaching.Inductively coupled plasma mass spectrometry was utilized to quantify REEs in both the coals and resultant leachates.Leaching the coals with 40%NaOH at 80℃,along with 40 kHz sonication,yielded a total rare earth element(TREE)recovery of less than 2%.Notable enrichment of REEs was observed in the run-of-mine and discard coal by 17%and 19%,respectively.Upon employing 7.5%HCl,a recovery of less than 11.0%for TREE was achieved in both coal samples.However,leaching the caustic digested coal samples with 7.5%HCl significantly enhanced the TREE recovery to 88.8%and 80.0%for run-of-mine and discard coal,respectively.X-ray diffraction analysis identified kaolinite and quartz as the predominant minerals.Scanning electron microscopyenergy dispersive microanalysis revealed monazite and xenotime as the REE-bearing minerals within the coal samples.These minerals were found either liberated,attached to,or encapsulated by the clay-quartz matrices.Further mineralogical assessments highlighted the increased REE concentrations in coals post-caustic digestion and subsequent recovery during acid leaching.This increase was attributed to the partial dissolution of kaolinite encapsulating the RE-phosphates and the digestion of REE-bearing minerals.Notably,undissolved REE-bearing elements in the caustic-acid-leached coal indicated the necessity of harsh leaching conditions to augment REE recovery from these coal samples.
文摘Sulfur dioxide (SO2) and nitrogen dioxide (NO2) are some of the air pollutants in industrial and urban areas. These are the most prevalent inorganic pollutants that are a serious risk to public health in populated areas. However, Lephalale, Polokwane and Steelpoort have not received enough attention to date. Therefore, this study investigated seasonal levels of NO2 and SO2 concentrations using passive sampling during summer, winter, autumn and spring of 2021. The sampling was done the first seven days of the month. The relationship of inorganic pollutants with meteorological factors was performed statistically using multiple linear regression model. Lephalale exhibited the highest NO2 concentration, 1.74 µg/m3, in spring. Whereas Polokwane and Steelpoort peaked at 1.57 µg/m3 and 0.84 µg/m3 in winter, respectively. The concentrations of SO2 were higher in winter than in other seasons in all areas. The multiple linear regression models showed that NO2 and SO2 dispersion was influenced by meteorological parameters such as temperature, wind speed and relative humidity. In Polokwane and Steelpoort, NO2 and SO2 concentrations are inversely correlated to temperature and relative humidity. Similarly, NO2 concentrations are inversely correlated, while SO2 concentrations are directly correlated to both temperature and relative humidity in Lephalale. Wind speed had positive and inverse correlations to the concentrations of both air pollutants. The SO2 and NO2 concentrations did not exceed the annual average of 50 µg/m3 and 94 µg/m3 as set by National Ambient Air Quality Standards and World Health Organization. However, it is important to keep pollution concentrations of SO2 and NO2 to relatively safe for humans and the environment in the studied areas.
基金NRF SARCh I Clean Coal Technology, Mintek – South Africa and the University of the Witwatersrand for making funds available for the research study
文摘A Longi LGS 500 wet high intensity magnetic separator(WHIMS) was used to concentrate a fine, low grade South African hematite ore. The ore was prepared into different size fractions and was subjected to changes in pulp density, magnetic field intensity and pulsation frequency which followed a 33 full factorial matrix. The concentrate mass yield and Fe grade were selected as the dependent responses to the changes. The analysis of variance(ANOVA) shows that the variables investigated are significant to the material's response to magnetic separation. This significance was in the order of magnetic field intensity followed by pulsation frequency and then pulp density. It was also noted that a single stage magnetic separation has a potential to upgrade a feed( 75 lm and 40% Fe) to a 55% Fe grade, as the pulsation frequency increases. In addition, the model predictions and actual data were in good agreement, reporting regression coefficients within acceptable ranges.
基金the financial assistance of the National Research Foundation(NRF)University of the Witwatersrand,Johannesburg,South Africa
文摘Reverse flotation studies on magnetite samples have revealed that the use of starch as a depressant of Fe-oxides has a hydrophilic effect on the surface of Fe-bearing silicates and significantly decreases Fe in the silica-rich stream when used in combination with an amine （Lilaflot D817M）. In this study, the effect of reverse flotation on the optimization of products obtained fi＇om magnetic separation was inves- tigated. Two different magnetic samples, zones 1 and 2, were milled to 〈75 btm and then subjected to low intensity magnetic separation （LIMS）. The LIMS test conducted on the 〈75 ~m shown an upgrade of 46.40wt% Fe, 28.40wt% SiO2 and 2.61wt% MnO for zone 1 and 47.60wt% Fe, 29.17wt% SiO2 and 0.50wt% MnO for zone 2. Further milling of the ore to 〈25 ~tm resulted in a higher magnetic-rich product after magnetic separation. Reverse flotation tests were conducted on the agitated magnetic concentrate feed, and the result shows a significant upgrade of Fe compared to that obtained from the non-agitated feed. Iron concentrations greater than 69%, and SiO2 concentrations less than 2% with overall magnetite recoveries greater than 67% and 71% were obtained for zones 1 and 2, respectively.
文摘A series of MgO nanoparticles were prepared by first precipitating and isolating Mg(OH)2 nanoparticles from Mg(NO3)2 at three different temperatures using NaOH followed by their thermal decomposition also at three temperature settings. The effects of temperature at which precipitation and thermal decomposition of the hydroxide occurred were studied to assess their influence on nanoparticle size and surface area. The synthesised nanoparticles were characterized using a suite of techniques including Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscope (SEM) analysis. The average diameter range of MgO nanoparticles ranged between 15 and 35 nm, while for the precursor Mg(OH)2 it varied between 28 and 45 nm. The nanoparticle surface area obtained from BET studies was found in all cases to increase from 77 to 106.4 m2/g with increasing temperature of precipitation. Antibacterial activities of the prepared Mg(OH)2 and MgO nanoparticles were evaluated against the Gram-negative bacteria, Escherichia coli, and the Gram-positive bacteria, Staphylococcus aureus, using agar diffusion method. A correlation between surface area and antibacterial activity supported the mechanism of bacterial inactivation as the generation of reactive species. The Mg(OH)2 and MgO nanoparticles both exhibited pronounced bactericidal activity towards the Gram positive bacteria than Gram negative bacteria as indicated by the extend of the zone of inhibition around the nanoparticle.
基金the financial support of the South African National Energy Research Institute(SANERI)the Mineral Processing Division, Mintek
文摘The concentration of phosphate flotation concentrate with P2O5 grade lower than the commercially acceptable phosphate quality was upgraded in the use of tribo-electrostatic technique. The concentration of the flotation concentrate stream was conducted under both triboelectrification and inductive charging mechanism. Mineralogical analysis reveals that the phosphate ore utilized was dominated mainly by fluorapatite, crandallite, wavellite, and with quartz as the major gangue mineral. Flotations concentrate of about 28.87% P2O5 was obtained from the reverse flotation technique, after conditioning the phosphate ore at 80% passing 150 lm under Lilafloat. Constant parameters such as à6 kV charging voltage, 25 kV separating voltage, inlet air, different charger rotary speed and splitter distances were investigated. Commercially accepted grade of 35.50% P2O5 was attained after the second stage of separation with a recovery of 12.26%, another phosphate product of 34.02% P2O5 and 85.19% was also recovered under the same condition. Single stage of separation also shows a significant increase in the grade of the product obtained, with 33.41% P2O5 and 84.07% recovery achievable. The practicability of tribo-electrostatic separation technique for upgrading flotation concentrates resulted in a significant increase in grade for <150 lm product that do not meet the viable grade.
基金funded by the Department of Science and Innovation/Mintek Nanotechnology Innovation Centre.
文摘Colorectal cancer(CRC)is among the leading causes of cancer mortality.The lifetime risk of developing CRC is about 5%in adult males and females.CRC is usually diagnosed at an advanced stage,and at this point therapy has a limited impact on cure rates and long-term survival.Novel and/or improved CRC therapeutic options are needed.The involvement of microRNAs(miRNAs)in cancer development has been reported,and their regulation in many oncogenic pathways suggests their potent tumor suppressor action.Although miRNAs provide a promising therapeutic approach for cancer,challenges such as biodegradation,specificity,stability and toxicity,impede their progression into clinical trials.Nanotechnology strategies offer diverse advantages for the use of miRNAs for CRC-targeted delivery and therapy.The merits of using nanocarriers for targeted delivery of miRNA-formulations are presented herein to highlight the role they can play in miRNA-based CRC therapy by targeting different stages of the disease.
文摘In this study, synthesis of copper nanoparticles was performed using organoclay as a support to stabilize the nanoparticles. Organoclay amount was gradually increased, which had an effect on the morphology of the resultant nanoparticles. Low amount of organoclay added resulted in larger and agglomerated copper nanoparticles whereas increased amount of organoclay gave smaller sized nanoparticles. The hybrid materials were characterized using the SEM and TEM for morphology, XRD and FT-IR spectroscopy for structural elucidation, thermal analysis using TGA and also studying their antibacterial effect on the two well-known gram negative bacteria of E. coli and P. Aeruginosa. The synthesized nanoparticles were found to be crystalline Cu nanoparticles with a mix of CuO. Larger sized copper nanoparticles and agglomerates showed the higher thermal behaviour as compared with smaller nanoparticles with higher organoclay loading. The hybrid showed an improved antibacterial activity as compared with organoclay alone. The hybrid showed the higher antibacterial effect against the P. aeruginosa microorganism as compared with the E. coli microorganism.
文摘Anisotropic gold nanoparticles were synthesized in a simple, environmentally benign process under ambient conditions of temperature and atmospheric pressure using bovine serum albumin (BSA) as both the reductant and biotemplate. Two types of anisotropic nanoparticles were produced in the system, namely larger two dimensional plates and smaller three-dimensional nanoparticles. Since the characteristics of nanoparticles are largely determined by their morphology, a simple centrifugation step was included to roughly separate the larger plate-like particles from the smaller more compact particles. In an attempt to identify potential applications, the properties of the particles were determined by TEM, SEM, STEM-EDS, UV-Vis spectroscopy and photoluminescence. The results of this study identified several optical properties of gold nanoparticles.
基金The work was financially supported by EPSRC platform grant GR/R95798, "The Platinum Development Initiative", and the Department of Science and Technology, South Africa
文摘Work has been ongoing in building a thermodynamic database for the prediction of phase equilibria in Pt-based superalloys. The alloys are being developed for high texture applications in aggressive environments. The database will aid the design of alloys by enabling the calculation of the composition and proportions of phases present in alloys of different compositions. In order to extend this database, a preliminary assessment of the Cr-Pt-Ru system has been undertaken, using a combination of Pandat and MTDATA software. As a first step, it was necessary to provide thermodynamic models for the three associated binary systems. Owing to a lack of thermodynamic information for these systems, the binary assessments were based on phase diagrams available in the literature. Using recent experimental phase equilibria data for the ternary system, a preliminary assessment of the Cr-Pt-Ru system has been produced. In this preliminary assessment, simplified models were employed for the L12 and sigma phases with a view to extending the descriptions as new experimental information becomes available.
基金The authors would like to acknowledge the South African National Research Foundation for funding this work.
文摘Although PVDF flat sheet membranes have been widely tested in MD,their synthesis and modifications currently require increased use of green and inexpensive materials.In this study,flat sheet PVDF membranes were synthesized using phase inversion and water as the pore former.Remarkably,the water added in the casting solution improved the membrane pore sizes;where the maximum pore size was 0.58μm.Also,the incorporation of f-SiO2NPs in the membrane matrix considerably enhanced the membrane hydrophobicity.Specifically,the membrane contact angles increased from 96°to 153°.Additionally,other parameters investigated were mechanical strength and liquid entry pressure(LEP).The maximum recorded values were 2.26 MPa and 239 kPa,respectively.The modified membranes(i.e.,using water as the pore former and f-SiO2NPs)were the most efficient,showing maximum salt rejection of 99.9%and water flux of 11.6 LMH;thus,indicating their capability to be used as efficient materials for the recovery of high purity water in MD.
基金the Department of Science and Technology(DST,South Africa)/National Nanoscience Postgraduate Teaching and Training Programme(NNPTTP)and National Research Foundation(NRF,South Africa,grant no.99270&91230).
文摘In this work,Fe3O4-Al2O3@CNFs nanocomposite was synthesised and used as a nanosorbent in the ultrasound-assisted dispersive magnetic solid phase extraction(UA-DMSPE)of 17-beta estradiol(E2)in wastewater samples.The quantification of E2 was achieved using high performance liquid chromatography coupled with diode array detector(HPLC-DAD).Various parameters affecting the efficiency of this sample preparation technique were optimised to achieve excellent sensitivity and high recoveries of E2.Response surface methodology was utilised for optimisation of these parameters.Using the optimised conditions,the linear dynamic range was achieved in the range of 0.1e1000 mgL^-1and the correlation coefficient was found to be 0.9981.The preconcentration factor,enrichment factor,limit of detection(LOD)and limit of quantification(LOQ)were 67,169,0.025 mgL^-1and 0.083 mg L1,respectively.The relative standard deviation(%RSD)for the intraday(n?10)and interday(n?5 working days)were 1.8%and 3.3%,respectively.The developed UA-DMSPE/HPLC-DAD method was applied for the preconcentration and determination of E2 in wastewater samples.The obtained results indicated that E2 was present in the wastewater samples.
基金Financial support from the National Research Foundation(NRF)–Nanotechnology Flagship Project[grant number 97823],the DST/Mintek Nanotechnology Innovation Centre–Water Research Node,and the NanoWS4RUMP community engagement project is acknowledged.
文摘Electrospun cyclodextrin(CD)-based nanofibers with capabilities to remove pollutants from water have been synthesized and characterized.The high-quality nanofibers presented here were synthesized in two simple steps that involved in-situ electrospinning of the nanofibers and all nanocomponents,followed by the reduction of silver(Ag+)and iron(Fe3+)ions to nanoparticles using an environmentally benign process that involved irradiation of the electrospun fibers using a tailor-made UV-equipped furnace at low temperatures.In the previously reported study it was observed that Ag and Fe nanoparticles effectively removed a range of different strains of Gram-negative and Gram-positive bacteria from water.As such,this study focused on improving the thermal and mechanical properties of the nanofibers prepared from polymer blends ofβ-CDs with cellulose acetate(CA)and small additions(2 wt%)of functionalized multiwalled carbon nanotubes(fMWCNTs).The electrospinning parameters were varied to determine the optimum conditions for preparation of uniform nonbeaded nanofibers.Bead-free and uniform nanofibers were obtained at a polymer concentration of 32%at the ratio of 1:1β-CDs:CA,syringe injection flow rate of 0.7 mL h−1,15 cm between the tip of the spinneret and the collector,and a voltage of 16 kV.The addition of f-MWCNTs was found to improve the tensile strength of the nanofibers by twofold,relative to nanofibers with no f-MWCNTs.The thermal degradation of the nanofibers was improved by a magnitude of 50°C.The study has shown that adding small amounts of f-MWCNTs improved the thermal stability and mechanical strength of the CD/CA nanofibers significantly.
基金The authors are grateful to the University of Johannesburg,Applied Chemistry Department,National Nanoscience Postgraduate Teaching and Training Programme(NNPTTP)National Research Foundation(NRF)Thuthuka(grant no.99720)for the permission to do this work as well as financial support.
文摘This study reports the removal of amoxicillin from environmental water matrices using zinc oxide coated carbon nanofibers composite as an adsorbent.The structural and surface properties of zinc oxide coated carbon nanofiber composite were characterized using X-ray diffraction,scanning electron microscopy/energy dispersion x-ray spectroscopy,transmission electron microscopy,and Fourier transform infrared spectroscopy.The factors(sample pH and dosage)influencing the adsorption experiments were optimised using central composite design.Freundlich,Langmuir and Flory-Huggin isotherm models were used to study the adsorption isotherms.The results obtained revealed that the maximum adsorption capacity was up to 156 mg g^-1.The kinetic studies demonstrated that the adsorption process was best described by pseudo-second-order model and the equilibrium data followed Langmuir isotherm model.The optimised batch method was then applied for the removal of amoxicillin in real wastewater samples.In addition,the zinc oxide coated carbon nanofibers nanocomposite was found to reusable up to fifteen cycles.
