1,721,009 research outputs found
Enhanced adsorption of cationic and anionic dyes based on bacterial cell membrane structure and pre-treatment techniques
Get PDFM.Tech. (Biotechnology)Abstract: Due to industrialization and development, the environment is under severe stress as a result of pollution. Water bodies are being compromised due to inadequate remediation technologies available. Conventional technologies are known to cause secondary pollution upon usage, which is of serious concern as they do not eliminate the predicament. Non-conventional methods are being considered because they are environmentally friendly and cost efficient. Dyes are one of the primary pollutants of water resources being very toxic and when discharged into the environment, they pose a threat to human and animal health due to their tetragenic, mutagenic and carcinogenic potentials. This study explores the use of microorganisms in bioremediation of dyes. In doing so, four bacteria viz: Gram-negative (i.e., E. coli, and Pseudomonas aeruginosa) and Gram-positive (i.e.,Bacillus subtilis, and Bacillaceae bacterium) were used. The bacteria were subjected to physical pre-treatment using an autoclave, mechanical pretreatment by grinding the inactive biomass and lastly, chemical pre-treatment using chemicals such as nitric acid, propyl amine, calcium chloride and ammonia. The pre-treatment techniques were applied to investigate their effect on the adsorption of dye. The Lagergren pseudo second-order kinetic was used to deduce the adsorption capacities as it was the best fit, implying that adsorption occurred by the chermisoption mechanism. The adsorption capacities of the bacteria improved tremendously from 68.49 to 161.29 mg/g in comparison to that of the untreated biomass (9.37 to 29.11 mg/g). It was also observed that in untreated biomass, no methyl orange (MO) adsorption took place whereas in treated biomass, bacteria had the ability to absorb and remove MO. The Fourier Transform Infrared (FTIR) spectra of the bacterial cell walls revealed the presence of functional groups (amines, carboxylic acids, alcohols, aldehyde and amides).Meanwhile, data obtained on the Scanning Electron Microscope (SEM) showed a homogenous surface and finer particles, which demonstrate an increase in the surface area of the treated bacterial cells. The Gram-positive and Gram-negative bacteria exhibited the ability to remove cationic and..
Phosphorylated carbon nanotube-cyclodextrin/silver-doped titania nanobiocomposites for water purification
Get PDFPh.D. (Chemistry)Abstract: Nowadays, the shortage of water resources is the major concern around the world and especially in Southern Africa. The challenge is to develop an effective method to recycle wastewater through adequate treatment. That is to design a water treatment material able to remove the pollutants from wastewater effectively and efficiently to the accepted levels. In this regard, the aim of this research project was to develop a new nanomaterial which was used as adsorbent and disinfectant to remove all the three classes of water pollutants (inorganic, organic and pathogenic microorganism) from wastewater. In this study, phosphorylated multiwalled carbon nanotube-cyclodextrin/silver doped titania (pMWCNT-βCD/TiO2-Ag) was synthesized, using a combined process of amidation reaction, cross-linking polymerization and the sol-gel method. For a better evaluation of the target material, the insoluble nanosponges β-cyclodextrin (βCD) polymer and pMWCNT-βCD composite polymer were also synthesized for comparison purposes. The prepared nanostructured materials were fully characterized using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), Brunauer-Emmett-Teller (BET) method, electron microscopy, and spectroscopy techniques. Fourier-transform infrared (FTIR) spectroscopy was used to confirm the presence of functional groups on the surface of modified MWCNTs, and the polymerization reaction. X-ray photoelectron spectroscopy (XPS) was employed to further confirm the presence of functional groups on the surface of the nanomaterials synthesized and to provide the percentage elemental composition with binding energies. Laser Raman showed the presence of MWCNT, βCD, and TiO2 in the nanocomposite. The anatase crystalline form of TiO2 in the samples synthesized was confirmed by X-ray diffraction (XRD) spectroscopy analysis. Transmission electron microscopy (TEM) analysis confirmed the structural morphology of the new biopolymer nanocomposite (pMWCNT-βCD/TiO2-Ag) as a sponge-like structure which showed a good dispersion of Ag nanoparticles. The BET surface area of the newly developed pMWCNT-βCD/TiO2-Ag was very high (352.55 m2/g), and this favored the use of this new nanomaterial as an adsorbent for the effective removal of pollutants from synthetic i.e. model wastewater and mine effluent samples..
Design and application of a bench scale evaporator for the treatment of coal power plant waste water
Get PDFMEng (Chemical Engineering), North-West University, Potchefstroom CampusThe potential of scale formation during the application of Multi-Effect Distillation (MED) technology for the treatment of Reverse Osmosis (RO) retentate was investigated in this study. An improved bench scale single effect evaporation unit was designed using the Solidworks Simulation Package and appropriate materials. Operating conditions were determined to be 80°C and 0.48 bar with the design constructed to maximise evaporation. Once assembled, RO-retentate was introduced to the evaporator at an evaporation rate of 4 L/h (22.3 L/m²/h), and the variation of the concentrations of scale forming elements determined. The evaporation observed translates to 34.5% water recovery. Speciation using PHREEQ-C modelling software showed that the concentrations of scale forming ions increased during evaporation. Scale prediction and prevention were explored using French Creek software, with anti-scaling agents being used to minimise scaling. The dosage of the anti-scaling agents inside the MED was determined using French Creek software. The anti-scaling agents yielded confirmation of their capability of keeping ions in suspension and preventing them from forming scale. When measuring the performance of the anti-scaling agents on this basis, AMPS (Acrylic Acid-2-Acrylamide-2-Methylpopane Sulfonic Acid Copolymer) fared better than PBTC (2-Phosphonobutane-1,2,4-Tricarboxylic Acid). However, HEDP (1-Hydroxy ethylidene-1,1-Diphosphonic Acid) yielded concentrations of scale forming ions lower than when no anti-scaling agent was dosed. This may be ascribed to the nature of complexes that HEDP forms with the scale forming ions. The application of MED technology combined with the use of anti-scaling agents to treat inland waste waters can see the MED evaporator serving a dual purpose. The primary purpose is to serve as water producing/recycling technology that can treat saline solutions to recycle as much fresh water as possible. The MED reject will be suitable for further treatment using other separation technology to ultimately produce fresh water and salts. The secondary purpose of the MED technology when applied to a power plant could be to dissipate some of the abundant heat present. The MED technology possesses the potential of alleviating the amount of heat energy the cooling towers must dissipate to some extent, thus lowering the amount of cooling water needed, and this should be investigated. Thus, a combination of membrane technology and thermal technology could theoretically be utilised in order to adhere to the zero liquid effluent discharge policy Eskom has, whilst lowering the amount of fresh water needed for cooling purposes. Additionally, the laboratory evaluation of anti-scaling agents prescribed by scale modelling software was investigated. The considered water contained high levels of scale forming agents. The selected test method to determine anti-scaling agent induction times was found to be inefficient and an improvement on the current method was proposed. The possible causes for the inefficiency of the selected induction time test method was mainly ascribed to an insufficient heating apparatus setup.Master
Synthesis of high-grade struvite from municipal effluents and application in the remediation of acid mine drainage
Get PDFMSc (Chemical Engineering), North-West University, Potchefstroom CampusAccess to clean water resource is a fundamental need and right to all citizen in any given country.
However, the water needs to comply with different standards, specifications and guidelines thus
ensuring that potential ecotoxicological effects are not ensued from the consumption of
contaminated water. In recent decades, the contamination of the environment with municipal
wastewater (MWW) and acid mine drainage (AMD) has been a matter of primary concern. This
has impaired the quality of water and its suitability to nurture natural life and make its inherent
values. In this study, we explored the synthesis of struvite from municipal wastewater and
appraise its application for the treatment of acid mine drainage. Batch experiments were used to
accomplish the goals of this study, specifically the one-factor-at-a-time (AFAAT) initiative as
process parameters. Evaluated parameters include contact time (mixing time) and feed dosage
whereas temperature and pH were ambient. Characterisations of feed and product solid samples
were done using HR-SEM-EDS, FTIR, XRD and XRF. Aqueous samples were characterised
using inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma
optical emission spectrometry (ICP-OES), Gallery-plus and multi-parameter probes. Synthesis of
struvite was done at 1 g: 100 mL of activated magnesite and municipal wastewater, respectively.
The mixtures were mixed at 60 minutes at 300 rpm. The product sludge was used for AMD
treatment. The obtained results revealed 30 minutes of equilibration and 15 g of dosage in 1000
mL at 300 rpm of mixing speed. Interaction of struvite with AMD led to > 99% removal efficacy for
Al, Fe, Mn and other metals except for sulfate, which demonstrated close to 30% removal efficacy.
XRD confirmed the synthesis of struvite with 60% purity. This was further confirmed by elevated
concentration of phosphate in XRF results. After the interaction of struvite and Raw Acid Mine
Drainage (RAMD), the product mineral confirmed the presence of Fe-based minerals and gypsum
hence denoting that Fe and sulfates are removed from AMD. The pH was observed to be ≥ 9.5
and this was suitable for attenuation of all the chemicals. Thus, this technology could valorise
struvite synthesized from municipal wastewater effluents and open new horizons for the effective
and sustainable management of wastewater effluents and AMD. This will minimize the footprints
of acid mine drainage and municipal wastewater on different spheres of the environment.
Although an economic feasibility and life cycle analysis need to be done to conclusively proof the
feasibility of this technology.Master
Leachability of polycyclic aromatic hydrocarbons from coal tar and synthesis of the nanohybrid photocatalyst for their degradation
Get PDFMEng (Chemical Engineering), North-West University, Potchefstroom CampusThere exists a great number of industrial processes that produce coal tar as a by-product. The rate of coal tar production is higher than the rate at which it is converted to other products, and its application is very limited. As a result, coal tars produced as by-products end up being discharged into the environment and occupy the unused land.In addition, the disposal of coal tar in the environment poses threats because of the toxic, carcinogenic, mutagenic, teratogenic and skin irritants compounds it contains.These compounds are known as polycyclic aromatic hydrocarbons (PAHs). PAHs can leach into surface waters since they are mobile. It is therefore important that the water contaminated by these harmful compounds is properly treated to avert the health and environmental problems they cause. Different techniques for the removal of PAHs from water have been investigated and explored. Photocatalysis has emerged to be a promising method in terms of efficiency, sustainability, economic impact and reliability in the removal of persistent organic pollutants such as PAHs. Even though photocatalysis has been found to be effective in purifying wastewater, there is a search for an appropriate photocatalyst to degrade these organic pollutants in water. This research focused on assessing the coal tar PAH profile and investigated the factors influencing the leachability of PAHs from coal tar into the environment. It was discovered that coal tar contains the majority of the most popular PAHs, which generally include 16 priority PAHs. It was also found that the mobility of PAHs from coal is highly influenced by contact time between coal tar and chemical properties of the aqueous solution the tar may be exposed to. The findings suggest that PAHs can leach from coal tar and enter water bodies, while the leachability of low molecular weight PAHs is much higher than the leachability rate of high molecular weight PAHs. Even though the amount of HMW PAHs that is leached into the water is very small, if the leaching process takes place for prolonged periods, the amount of HMW PAHs in waters can be significant. Therefore, it is important that a photocatalyst that is able to degrade both LMW and HMW PAHs is found. In this study, RGO-Bi2MoO6 was investigated as potential photocatalyst to degrade PAHs in water. Thus, this photocatalyst was synthesised using hydrothermal methods because it allows the use of elevated temperatures, at which the RGO-Bi2MoO6 nanocomposite forms, and it is easy to operate. This research focused on using the synthesised photocatalyst in the photo degradation of coal tar PAHs. To test the photocatalytic performance of RGO-Bi2MoO6 in degrading PAHs, a degradation test was carried out using naphthalene as representative of PAHs. It was found that RGO-Bi2MoO6 is a highly effective material in degrading naphthalene. The material showed a photo degradation efficiency of about 95%, and the results also indicated that RGO-Bi2MoO6 can be reused for about five times and still achieve a photo degradation efficiency of over 80%. The small amount of RGO that was added in the photocatalyst played a significant role in improving the performance of the material.Master
Colouring of dolomite, quartzite and dolerite mine dump rocks
Get PDFFor environmental and aesthetic purposes it has
become essential that mine dump rocks either blend into the
environment or be used in the production of other products.
Lately, there has been a constant need to produce more durable
road and construction material and to develop an alternative for
granite countertops and flooring. For the visibility of road surface
material and the aesthetic aspect of countertops, the colouring of
mine dump rocks was considered. A cost effective and
environmentally friendly process was suggested to colour mine
dump rocks. In this study different colouring agents for three mine
dumping rocks, dolomite, quartzite and dolerite, were
investigated. The aim was to create lasting colours that have a high
wear resistance to weather conditions. Coloured dolomite can be
used as road and construction material, coloured quartzite as
countertops while coloured dolerite can serve as a replacement for
road surface
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Simulated Inhibitory Effects of Typical Byproducts of Biomass Pretreatment Process on the Viability of Saccharomyces cerevisiae and Bioethanol Production Yield
Get PDFThe abundance of second generation feedstock reinforces the consideration of biofuel over fossil fuel, as bioethanol can be produced from lignocellulosic materials. However, the pretreatment required for oxidation of lignocellulose into hexose often results in the production of inhibitors likely to impede the activity of Saccharomyces cerevisiae during bioethanol production. This study aimed to investigate the comparative inhibitory effects of acetic acid and vanillin on the viability of S. cerevisiae and the production yield of bioethanol. Different concentrations of inhibitors were spiked in the fermentation broth then the production of bioethanol monitored overtime and correlated with cell viability. The results showed that the inhibition of S. cerevisiae by vanillin is more potent compared to acetic acid; however the reduction of bioethanol yield after 12 h was more pronounced with acetic acid (42.8% reduction) than with vanillin (33.3% reduction) which was ascribed to the simultaneous production of weak acids during the fermentation process. The viability test has shown that in the presence of lower concentrations of inhibitors, S. cerevisiae can adapt for the first 12 h of fermentation and then may improve ethanol production yield overtime. At lower concentrations (2 g/l vanillin and 4 g/l acetic acid) the effect of inhibitors on the viability of S. cerevisiae and ethanol productivity does not last and can be overcome by the adaptation of the yeast. However, the presence of higher concentrations (4 g/l vanillin and 6 g/l acetic acid) results to nearly total inhibition of bioethanol production and the remediation of such effect may therefore require a detoxification process.Keywords: Bioethanol Production, Saccharomyces cerevisiae, Inhibition, Acetic Acid, Vanillin, Cell Viabilit
Synthesized af-PFCl and GG-g-P(AN)/TEOS hydrogel composite used in hybridized technique applied for AMD treatment
No full textIn the present study af-PFCl, GL-g-P(AN) hydrogel and GL-g-P(AN)/TEOS hydrogel composite were synthesized. The hydrogels were characterized using the fourier transformed infra-red (FTIR) and the scanning electron microscope (SEM) techniques. The coagulant af-PFCl and the hydrogels were applied consecutively in flocculation and adsorption processes respectively for the treatment of acid mine drainage (AMD). It was observed that the grafting process increased the amount of binding groups on the hydrogels. The hybridization of the techniques assisted in the removal of anions; while the cations were mostly removed by the adsorption process. The adsorbents behaviour was fittingly expressed by the pseudo-second order model. The adsorption capacities of GL-g-P(AN)/TEOS hydrogel composite for the removal of Al, As and Zn were 3.89, 0.66 and 0.394 respectively; while the adsorption capacities of GL-g-P(AN) for the removal of Al and Mg were 3.47 and 9.66 mg/g respectively.
The techniques applied in this study have shown good potential for the removal of specific pollutants from the AMD; it is however, important that the appropriate hybridization of techniques allows to remove all the pollutants and restore acceptable water qualit
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