South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie最新文献

{"title":"The Thermal Agitated Phase Transitions on the Ti32 Nanocluster: a Molecular Dynamics Simulation Study","authors":"Tshegofatso M. Phaahla, A. Sokol, C. Catlow, S. Woodley, P. Ngoepe, H. Chauke","doi":"10.17159/0379-4350/2021/v74a4","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v74a4","url":null,"abstract":"ABSTRACT Molecular dynamics simulations were performed to investigate the stability with respect to increasing the simulated temperature from 300 to 2400 K of an isolated cluster composed of 32 titanium atoms. The interatomic interactions were modelled using Gupta potentials as implemented within the classical molecular dynamics simulation software DL_POLY. The radial distribution functions (RDF), diffusion coefficient, and density profiles were examined to study the structural changes as a function of temperature. It was found that the Ti32 nanocluster exhibits temperature structural transition. The icosahedron and pentagonal bi-pyramid structures were found to be the most dominant building block fragments. Deformation of the nanocluster was also measured by diffusion coefficient, and it was found that the Ti32 are mobile above the bulk melting point. The phase transitions from solid to liquid have been identified by a simple jump in the total energy curve, with the predicted melting temperature near the bulk melting point (1941.15 K). As expected, the RDF's and density profile peaks decrease with increasing temperature. Keywords: Molecular dynamics, titanium cluster, radial distribution functions, diffusion coefficient, mean square displacement.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Occurrence and Fate of Amoxicillin and Penicillin G Antibiotics in Hospital Wastewater Treatment Plants: A Case Study - Gonbad Kavous, Iran","authors":"M. Golchin, Mohammad-Yaser Khani, M. Sadani, M. Sadeghi, Mahsa Jahangiri-rad","doi":"10.17159/0379-4350/2021/V75A11","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/V75A11","url":null,"abstract":"ABSTRACT Release of antibiotics to the environment as a result of wastewater effluent discharge is a cause for concern worldwide, as they pose a potential threat to human health and the earth ecosystem. Penicillin and amoxicillin are widely used antibiotics. Despite their rapid hydrolysis in aqueous matrices, their presence in the environment is widely investigated. The current study reported and analysed the current state of four hospital wastewater treatment plants (WWTPs) in Gonbad Kavous, Iran, during 2019, from the perspective of amoxicillin and penicillin G removals. WWTPs were sampled at various stages of the treatment process to determine at which stage the antibiotics are being removed. Concentrations of amoxicillin and penicillin G in raw wastewater, analysed by HPLC, varied from 0.35 to 1.02 and 0.02-0.31 /AgL-1, respectively. These values reduced in the final effluent, corresponding to overall efficiency in removing the studied antibiotics of 20-60.5%. Anaerobic processes (i.e. septic tank) slightly outperformed aerobic biological processes for both antibiotics' removal, and penicillin G was removed more efficiently than amoxicillin. Effects of wastewater physicochemical properties, including chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS) on antibiotics removal, were also studied. Whereas statistically significant correlations were noticed between COD, amoxicillin and penicillin G removals, their decline showed no correlation with TSS removal. Our study shows that despite the deployment of treatment plants, a considerable amount of antibiotics is released into receiving water bodies, resulting in significant amounts of these pharmaceuticals entering the environment. There is abundant room for further progress in the detection and quantification of pharmaceuticals and other emerging contaminants in hospital wastewaters and their metabolites and biodegradation products. Keywords: amoxicillin; penicillin G; high-performance liquid chromatography; hospital wastewater treatment plants; removal.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Africa-UK Partnership for the Computer-aided Development of Sustainable Catalysts","authors":"D. Santos-Carballal, C. G. van Sittert, N. D. de Leeuw","doi":"10.17159/0379-4350/2021/v74a1","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v74a1","url":null,"abstract":"Collaboration is the cornerstone of modern science, driving the development of new knowledge, concepts, methodologies, and thought processes. The complementary expertise existing in South Africa, Ghana, Botswana, Namibia, and the United Kingdom has allowed the advancement in the field of sustainable catalysis showcased in the thematic issue of the South African Journal of Chemistry, to which this foreword is an introduction. Historically, the design, testing and characterization of the catalyst structure and analysis of reactants, intermediates, and products, has been at the centre of catalysis science. However, the advent of computer modelling has underpinned the predictive simulation of the geometries and properties of catalysts and their interaction with reactants, intermediates, and products. The inspection and assessment of simulated catalytic pathways and the effect of a range of environmental conditions have become an almost routine task in modern catalysis research, thereby supporting and complementing experiments. The modelling of various reaction mechanisms and the calculation of their kinetic and thermodynamic energy profiles has led to a new and realistic description of catalytic processes. The rapid progress of the computer-aided development of sustainable catalysts has been facilitated by innovative and accurate theoretical concepts and their implementation into a variety of software codes. The application of these computational tools to simulate complex systems and realistic problems have been driven by constantly expanding computational capacity. Most of the papers in this theme issue have used the South Africa National Centre for High Performance Computing (CHPC), the Cardiff University HPC systems, the pan-Wales network of computer clusters HPC Wales or its successor Supercomputing Wales (SCW), hosted by Cardiff University. The articles in this theme issue exemplify many of the major challenges in the contemporary computer-aided development of catalysts and materials for sustainable energy. The topical simulation of the lithium intercalation voltage in spinel-structured materials is explored in the paper by Malatji et al.1 In contrast, key issues in the development of computational models to describe cobalt and its oxide phases are addressed in the article of Cadi-Essadek et al.2 The paper of Phaahla et al.3 examines the phase transition in titanium nanoclusters using dynamic simulation methods, and the challenges in extrapolating binding energies to alkaline earth metal oxides are investigated by Escher et al.4 In the contribution of Botchwaya et al.,5 density functional theory calculations are used to model the surface and catalytic properties of zeolites. On the other hand, Meerholz et al.6 deployed atomistic simulations based on interatomic potentials to provide new insight into the thermodynamics and structure of the atomic distribution in metal alloy surfaces. Nyeptesi et al.7 have exploited in situ monitoring techniques t","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Adsorption-Kinetic Studies of Mordant Exhaust Dyeing of Cotton and Silk Fabrics with Dye Extract of M. lucida Plant Species","authors":"Janani Loum, R. Byamukama, P. Wanyama","doi":"10.17159/0379-4350/2021/v75a16","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v75a16","url":null,"abstract":"ABSTRACT The kinetics and adsorption isotherms of the extremely slow traditional natural exhaust dyeing that takes many hours or days have been studied purposely to find means of improving the process. The dyeing of cotton and silk fabrics using dye extract of M. lucida at 50 °C were elucidated with graphs to predict the reaction orders and identify the appropriate adsorption isotherm model(s). Since the dye is UV active, changes in UV absorbance were used in place of changes in concentrations. The simultaneous and post mordanting methods followed pseudo-second-order reactions, hence chemisorption. However, mordant application to the dyed fabrics during post mordant followed a pseudo-first-order model, largely physisorption. Dyeing has followed Langmuir and Freundlich isotherm models with linear correlation r2 ranging between 1 and 0.998. From the Freundlich model and values of Langmuir constant RL (0.9307 to 1.0), the process is homogeneous, forming a favourable and linear monolayer. Accordingly, the dyeing speed can be improved by increasing the concentration of dye liquor. Additionally, according to the Freundlich model, higher dye intensity on fabrics is recorded in post mordanting. Keywords: adsorption isotherms, equilibrium, exhaust dyeing, mordant, rate law","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"106 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bioaccumulation and Human Risk Assessment of Heavy Metals in Oreochromis niloticus and Clarias gariepinus Fish Species from the Golinga Reservoir, Ghana","authors":"Zita Naangmenyele, Somandla Ncube, F. Akpabey, S. Dube, M. Nindi","doi":"10.17159/0379-4350/2021/V75A13","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/V75A13","url":null,"abstract":"ABSTRACT The Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus) from the Golinga reservoir in Northern Ghana are consumed as an alternative source of protein. In the current study, levels of selected metals (As, Cd, Fe, Co, Cr, Cu, Mn, Mo, Ni and Pb) in the two fish species and the fish condition were determined, and potential human health effects assessed. The metal concentrations in the edible fish muscles ranged from 0.16 mg kg-1 (Mn) to 101 mg kg-1 (Pb). The weight-length relationships showed that both fish were growing isometrically, and bioaccumulation of metals from the reservoir was considered insignificant with bioconcentration factors below 100 except for Mn, whose value was 161 in the gills of Oreochromis niloticus. The health risk assessment showed that Pb, Cd and As had Target Hazard Quotient values above 1 for both fish species, with that of As being as high as 19.6 for Oreochromis niloticus. The target cancer risk values for As, Cd, Cr and Pb were above the non-risk threshold of <10-6, indicating the risk of cancer developing over the years due to fish consumption. The metal concentration in the fish in the reservoir should therefore be constantly monitored and potential health risks associated with frequent consumption of the fish assessed. Keywords: fish; health risk assessment; Nile tilapia; Target Hazard Quotient; trace metals","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DFT+U Study of the Electronic, Magnetic and Mechanical Properties of Co, CoO, and Co3O4","authors":"Abdelaziz Cadi-Essadek, A. Roldan, D. Santos-Carballal, P. Ngoepe, M. Claeys, N. D. de Leeuw","doi":"10.17159/0379-4350/2021/v74a3","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v74a3","url":null,"abstract":"ABSTRACT Cobalt nanoparticles play an important role as a catalyst in the Fischer-Tropsch synthesis. During the reaction process, cobalt nanoparticles can become oxidized leading to the formation of two phases: CoO rock-salt and Co3O4 cubic spinel. Experimentally, it is possible to evaluate the phase change and follow the catalyst degradation by measuring the magnetic moment, as each material presents a different magnetic structure. It is therefore important to develop a fundamental description, at the atomic scale, of cobalt and its oxide phases which we have done here using density functional theory with the Dudarev approach to account for the on-site Coulomb interactions (DFT+U). We have explored different Ueff values, ranging from 0 to 5 eV, and found that Ueff = 3.0 eV describes most appropriately the mechanical properties, as well as the electronic and magnetic structures of Co, CoO and Co3O4. We have considered a ferromagnetic ordering for the metallic phase and the antiferromagnetic structure for the oxide phases. Our results support the interpretation of the catalytic performance of metallic cobalt as it transforms into its oxidized phases under experimental conditions. Keywords: Materials chemistry, cobalt oxides, cobalt metal, spinel, density functional theory, on-site Coulomb correction.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient Vortex-assisted Extraction of Phorbol Esters from Jatropha Leaves and Correlation Between Leaves and Seeds in Phorbol EstersContent","authors":"Hercílio E. Zimila, Jaime S. Mandlate, Tercina P. Ngovene, Motoyuki Nakao, A. Uamusse","doi":"10.17159/0379-4350/2021/v75a19","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v75a19","url":null,"abstract":"ABSTRACT This work aimed to optimise and validate the vortex-assisted extraction with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) method to quantify phorbol esters (PEs) in Jatropha leaves. Additionally, to evaluate the correlation between PEs content in leaves and seeds. The results of PEs content were expressed as equivalent of the major Jatropha phorbol ester, 12-deoxy-16-hydroxyphorbol-4'-[12',14'-butadienyl]-6'-[16',18',20'-nonatrienyl]-bicyclo[3.1.0]-hexane-(13-O)-2'-[carboxylate]-(16-O)-3'-]8'-butenoic-10']ate (DHPB) . One-variable-at-time strategy and 25-1V factorial fractional design were employed to determine the effects of solvent type, volume, stirring frequency, extraction time and cycles on yield. The quantification was performed using HPLC-UV. The optimum conditions were three extractions with 2% tetrahydrofuran:dichloromethane (1:1) in methanol (THF:DCM/MeOH). The sample:solvent ratio was 1 mg:25 μL, and the vortex stirring was 2200 rpm for 5 minutes. The method showed good linearity (R2 0.999), recoveries (97 to 105%), selectivity and repeatability (RSD 1.93-7.95%). In addition, good limits of detection and quantification of 2.19 and 6.65 ng μL\"1, respectively, were noted. DHPB content in leaves and seeds ranged from 0.01 to 0.38 mg g\"1 and 0.41 to 1.82 mg g\"1, respectively. There is a statistically significant and positive linear relationship between leaves and seeds for DHPB content. These results may have practical application in analysing and predicting the amount of PEs in Jatropha leaves for environmental safety studies and the selection of better varieties for genetic improvement. Keywords: correlation, Jatropha leaves; Jatropha seeds; phorbol esters; vortex-assisted.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Green Synthesis of Nickel Oxide Nanoparticles using Populus ciliata Leaves Extract and their Potential Antibacterial Applications","authors":"M. Hafeez, R. Shaheen, B. Akram, M. N. Ahmed, Z. Ul-Abdin, S. Haq, S. Din, M. Zeb, M. Khan","doi":"10.17159/0379-4350/2021/v75a21","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v75a21","url":null,"abstract":"ABSTRACT Green synthesis of nanoparticles has received a lot of attention from scientists globally because it is eco-friendly, relatively rapid, and a cost-effective method. This work presents a method for the green synthesis of nickel oxide nanoparticles (NiO-NPs) using leaf extracts of Populus ciliata as a reducing and stabilising agent. The synthesised NiO-NPs were characterised by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. It was found that the synthesised NiO-NPs shapes varied, were highly crystalline, and had a face-centred cubic geometry. The calculated crystallite size of the synthesised nanoparticles was 44 nm. Moreover, the antibacterial activity of the synthesised NiO-NPs was also conducted against Gram-positive bacteria (Bacillus subtilis, Bacillus licheniformis) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae). Bacillus subtillus showed a maximum inhibition zone of 28.1±1.6 mm, whereas Klebsiella pneumonia showed a minimum inhibition zone of 9.2±0.5 mm. It was also found that the antibacterial activity increased with an increase in the concentration of NiO-NPs. Keywords: antibacterial activity, green synthesis, nanoparticles, NiO, Populus ciliata.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbon Nanodots Derived from Natural Products","authors":"Y. Kwee, A. Kristanti, Kaido Siimon, N. Aminah, M. Z. Fahmi","doi":"10.17159/0379-4350/2021/V75A6","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/V75A6","url":null,"abstract":"This review highlights recent improvements, and present situations concerning the practical application of, natural productsbased carbon nanodots (CNDs) in nanomedicine, sensors, drug delivery, bio-imaging, solar cells, photocatalysis and nanoencapsulation. CNDs are zero-dimensional carbonaceous nanomaterials that have recently drawn much attention because of their unique physicochemical properties, such as excellent biocompatibility and tunable photoluminescence, easy functionalization, solubility in water, dispersibility, and low toxicity. Additionally, they are environmentally friendly, abundant, easily accessible, and rich in multiple elements. Since CNDs derived from organic products have unique properties, we explored and found that the properties of CNDs may depend on the preparation method and the used precursors. This study also informs on the positioning of natural products in nanotechnology.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"75 1","pages":"40-63"},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Approaching Bulk from the Nanoscale: Extrapolation of Binding Energy from Rock-Salt Cuts of Alkaline Earth Metal Oxides","authors":"Susanne G. E. T. Escher, H. D. Duncan, A. Sokol, S. Woodley","doi":"10.17159/0379-4350/2021/v74a5","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v74a5","url":null,"abstract":"ABSTRACT A systematic DFT study is performed on (MgO)B, (CaO)n, (SrO)n, and (BaO)n clusters with 6 < n < 50, and which display a cuboid 2X2X2 atomic motif seen in the bulk, rock-salt, configuration. The stability and energy progression of these clusters are used to predict the energies of infinitely long nanorods, or nanowires, slabs, and the bulk global minimum energy. Keywords: Alkaline earth metal oxides, nanoclusters, nanorods, DFT.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}