South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie最新文献_第6页

H-FER-Catalyzed Conversion of Methanol to Ethanol and Dimethyl Ether: a First-Principles DFT Study h - fe催化甲醇转化为乙醇和二甲醚:第一性原理DFT研究

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2021-01-01 DOI: 10.17159/0379-4350/2021/v74a6

Cecil H. Botchway, R. Tia, E. Adei, N. Dzade, N. D. de Leeuw

{"title":"H-FER-Catalyzed Conversion of Methanol to Ethanol and Dimethyl Ether: a First-Principles DFT Study","authors":"Cecil H. Botchway, R. Tia, E. Adei, N. Dzade, N. D. de Leeuw","doi":"10.17159/0379-4350/2021/v74a6","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v74a6","url":null,"abstract":"ABSTRACT Methanol adsorption and dehydration reactions within zeolites represent important steps in the catalytic conversion process to form long-chain hydrocarbons. Herein, first-principles density functional theory (DFT) is employed in the determination of methanol adsorption and conversion in ferrierite (FER), where we predict the fundamental adsorption geometries and energetics of methanol adsorption. The methanol molecule is shown to physisorb at all explored binding sites, stabilized through hydrogen-bonded interactions with the acid site atOmeth-Hframbond distances ranging from 1.33-1.51 A. We demonstrate that the zeolites' adsorption capability is affected by the silicon/aluminium ratio, with stronger adsorptions predicted in the material with silicon to aluminium fractions of 5 than 8. The adsorption strength is also found to vary depending on the tetrahedral binding site, with the T1O2 site yielding the most stable methanol adsorption structure in the Si/Al ratio = 5(Eads = -22.5 kcal mol-1), whereas the T1O1 site yields the most stable adsorption geometry (Eads = -19.2 kcal mol-1) in the Si/Al ratio = 8. Upon translational and rotational motion, methanol is protonated resulting in the breaking of its C-O bond to form a methoxy species bound to the framework oxygen (O-CH3 distance of 1.37 A), whereas the water molecule is stabilized at the acid site through H-bonding (Owat-H = 2.0 A). Further reaction between the methoxy species and a second methanol molecule results in the formation of ethanol and protonated dimethyl ether, with adsorption energies of -42 and -25 kcal mol-1, respectively. The results in this study provide atomistic insight into the effect of acidity of the FER zeolite on the adsorption and conversion of methanol. Keywords: Zeolites, ferrierite, methanol adsorption, acid sites, density functional theory (DFT).","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463743","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}

引用次数: 3

Selective Solid-Phase Extraction Using Molecularly Imprinted Polymers for the Analysis of Target Pesticides in Cannabis Bud 分子印迹聚合物选择性固相萃取法分析大麻芽中目标农药

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2021-01-01 DOI: 10.17159/0379-4350/2021/v75a17

P. Myburgh, G. Kemp, P. Forbes

{"title":"Selective Solid-Phase Extraction Using Molecularly Imprinted Polymers for the Analysis of Target Pesticides in Cannabis Bud","authors":"P. Myburgh, G. Kemp, P. Forbes","doi":"10.17159/0379-4350/2021/v75a17","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v75a17","url":null,"abstract":"ABSTRACT A molecularly imprinted solid-phase extraction (MISPE) procedure was developed for the GC-MS analysis of four high priority pesticides (atrazine, terbuthylazine, acetochlor and alachlor) in a cannabis bud sample matrix. The study demonstrated that the synthesised polymer had a high affinity and good selectivity for either chloroacetamide or triazine classes of pesticide used as a template molecule during the molecularly imprinted polymerisation reaction. The MISPE procedure was optimised in terms of loading, washing and elution fractions utilising a range of aqueous methanol solutions for optimal recovery and minimal matrix interferences. The optimal wash fraction was 20% (v/v) methanol in an aqueous solution, whilst 70% (v/v) was used for the elution fraction. The selectivity, accuracy and recovery of the MISPEs were verified using a synthesised non-imprinted polymer and a commercial C18 cartridge as reference sorbents in comparative experiments. Approximately 3 g of the cannabis bud sample was spiked at a 0.05 mg/kg maximum residue limit (MRL) concentration. The recovery of the four selected pesticides extracted from the spiked samples ranged between 76.4-85.0% when utilising the optimised MISPE methods, compared to 91.6-96.9% for the C18 SPE. However, the use of the MISPE resulted in enhanced selectivity, as evidenced by GC-MS analysis, due to the extraction of less matrix interferences. Therefore, it can be concluded that the MISPE is a viable pre-treatment method for selective pesticide analysis in cannabis flowers using GC-MS when selectivity is valued for the extraction of target pesticides from a complex sample matrix. Keywords: molecularly imprinted polymer; solid-phase extraction; Cannabis; pesticides; atrazine; terbuthylazine; acetochlor; alachlor","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463690","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}

引用次数: 0

Synthesis and Biological Evaluation of New Chromenes and Chromeno[2,3-d] pyrimidines 新型铬烯和[2,3-d]嘧啶的合成及生物学评价

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2021-01-01 DOI: 10.17159/0379-4350/2021/v75a18

F. Belhadj, Z. Kibou, M. Benabdallah, M. Aissaoui, M. Rahmoun, D. Villemin, N. Choukchou-Braham

引用次数: 2

Degradation of o-Chloranil Using Nanocrystalline-Cellulose/TiO2 Composites via a Solar Photocatalytic Route 纳米晶纤维素/TiO2复合材料在太阳光催化下降解邻氯胺

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2021-01-01 DOI: 10.17159/0379-4350/2021/V75A10

Vashen Moodley, S. Maddila, S. Jonnalagadda, W. E. Zyl

{"title":"Degradation of o-Chloranil Using Nanocrystalline-Cellulose/TiO2 Composites via a Solar Photocatalytic Route","authors":"Vashen Moodley, S. Maddila, S. Jonnalagadda, W. E. Zyl","doi":"10.17159/0379-4350/2021/V75A10","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/V75A10","url":null,"abstract":"ABSTRACT Water pollution by organic pollutants is a continuous and increasing problem of global concern. In this paper, we developed a nanocrystalline cellulose (NCC) and titania (TiO2) based nanocomposite for the photocatalytic degradation of o-chloranil via aqueous wet impregnation. Different NCC loadings (10, 20, 40, and 80%) were used, and several analytical and microscopy techniques characterised the NCC/TiO2 catalyst. The efficiency of TiO2 as a photo-catalyst was enhanced through the chiral nematic nature and potential charge carrier capacity of NCC, which lowered the rate of electron recombination. The NCC/TiO2 material was used in the solar-driven photo-degradation of o-chloranil (3,4,5,6-tetrachloro-1,2-benzoquinone), a by-product of a commonly used pesticide. The successful decomposition of o-chloranil led to the successful identification of three breakdown products, namely 2,3-dichloro-4,5-dioxohex-2-enedoic acid (DCA), 2,3-dioxosuccinic acid (DSA) and oxalic acid (OA). The 20% NCC/TiO2 catalyst was found to be optimum and showed excellent degradation and mineralisation of o-chloranil within 2 hours (~90% degradation after 2 hours or 0.00920 mols of the total 0.0102 mols). The degradation products were analysed and identified using GC-MS. The photo-catalyst offers many benefits, including ease of preparation, a low cost-factor, and high stability with no loss of activity. Keywords: nanocrystalline cellulose; o-chloroanil; photocatalyst; photo-degradation; titania","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463931","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}

引用次数: 1

Trends in NMR Structural Elucidation Of Polycyclic Cages, Namely: Adamantane, Pentacycloundecane and Trishomocubane 多环笼，即金刚烷、五环癸烷和三环癸烷的核磁共振结构研究进展

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2021-01-01 DOI: 10.17159/0379-4350/2021/V75A14

M. Kelani, D. Dieudonné, Kornelia J. Skowron, Clayton A. Pedigo, Thavenden Govender, H. Kruger, Tricia Naicker, Oluseye K. Onajole

引用次数: 0

Effect of Telfaira occidentalis Leaf Extract on Packed Cell Volume in Rats with Malaria-induced Anaemia 西叶提取物对疟疾性贫血大鼠堆积细胞体积的影响

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2020-01-01 DOI: 10.17159/0379-4350/2020/v73a8

C. Ikese, S. T. Ubwa, S. Adoga, S. Audu, M. I. Kuleve, F. O. Okita, A. Okoh

引用次数: 0

A Novel Biopolymer-based Nanomagnetic Catalyst for the Synthesis of 4H-pyran and Tetrahydro-4H-chromene Derivatives 合成4h -吡喃和四氢- 4h -铬衍生物的新型生物聚合物纳米磁性催化剂

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2020-01-01 DOI: 10.17159/0379-4350/2020/v73a9

A. Mohammadzadeh, A. P. Marjani, A. Zamani

引用次数: 18

Optimization of X-ray Fluorescence Calibration through the Introduction of Synthetic Standards for the Determination of Mineral Sands Oxides 引入矿砂氧化物测定合成标准优化x射线荧光定标

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2020-01-01 DOI: 10.17159/0379-4350/2020/v73a14

Cramwell Badla, F. Wewers

{"title":"Optimization of X-ray Fluorescence Calibration through the Introduction of Synthetic Standards for the Determination of Mineral Sands Oxides","authors":"Cramwell Badla, F. Wewers","doi":"10.17159/0379-4350/2020/v73a14","DOIUrl":"https://doi.org/10.17159/0379-4350/2020/v73a14","url":null,"abstract":"An XRF spectrometer traditionally requires its methods to be calibrated using certified reference materials (CRMs). This means choosing from a limited selection of CRMs, which are costly and not widely available. This article examines the application of synthetic oxide standards made from commercially available high purity compounds for the calibration of an XRF spectrometer. Enabling it to analyze for major, minor and trace elements (Mg, Al, Si, P, Hf, Ca, Ti, Zr, Fe, Th, U) in heavy mineral sands processing. Calibration standards were synthesized by mixing pure compounds and mineral sands reference materials, to mimic matrices similar to that of the routine samples and cover the required analytical range. The aliquots were mixed in % fractions and fused with a 1:9 sample/borate dilution to make glass beads. The optimized calibration was validated as per SANAS TR 26-02 criteria for linearity, working range, limit of detection (LOD) and quantification (LOQ), precision and accuracy. The correlation coefficients (r) of the resulting calibration curves were >0.999, showing excellent linearity. The working range for all the calibration lines was satisfactory. The LOD and LOQ values for all the lines were low enough to prevent extrapolation below the lowest calibration point. The precision of the calibration was sufficiently high, and the accuracy was of adequate quality with z(MAD) <2. These observations support the successful synthesis and use of a well-selected set of synthetic standards. Additionally, it has been successfully utilized to analyze a variety of heavy mineral sands samples.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463515","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}

引用次数: 1

Synthesis and Characterization of Zeolites Produced by Ultrasonication of Coal Fly Ash/NaOH Slurry Filtrates 粉煤灰/NaOH浆液滤液超声合成沸石及表征

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2020-01-01 DOI: 10.17159/0379-4350/2020/v73a10

Tebogo M.A. Mokgehie, W. Gitari, N. Tavengwa

{"title":"Synthesis and Characterization of Zeolites Produced by Ultrasonication of Coal Fly Ash/NaOH Slurry Filtrates","authors":"Tebogo M.A. Mokgehie, W. Gitari, N. Tavengwa","doi":"10.17159/0379-4350/2020/v73a10","DOIUrl":"https://doi.org/10.17159/0379-4350/2020/v73a10","url":null,"abstract":"Studies were conducted to determine if crystalline zeolites could be obtained from the filtrates of coal fly ash (CFA)/NaOH slurries through sonication. The CFA/NaOH slurries were obtained by aging CFA in 3 M NaOH for 24 h at 50 °C using a solid/ liquid (S/L) ratio of 15 g/120 mL. FT-IR studies indicated that the ‘Lo’ regime ultrasonicated zeolite had higher intensities than that of the ‘Hi’ frequency ultrasonicated zeolite. The bands associated with the ‘Lo’ regime ultrasonicated zeolite were observed at 1066 cm, 1400 cm and 3600 cm, which were identified as Si-O asymmetric stretch, Al-O asymmetric stretch, O-H bend and O-H asymmetric stretch, respectively. Based on PXRD studies, the zeolitic phases were most intense for the 90 min ultrasonicated zeolite. Powder X-ray diffraction studies showed that the phases initially in CFA, such as quartz and aluminosilicate, were converted into gismodine zeolite Na-P1. Morphological changes were seen as ultrasonication period was increased. At short ultrasonication times, irregularly shaped fused-like grain structures were observed, while at longer times separate grain-like structures became more apparent. Energy dispersive X-ray spectroscopy studies on the 90 min ultrasonicated zeolite indicated the presence of Na, O, Si and Al, which were important building-blocks for the zeolites.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463328","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}

引用次数: 3

Synthesis, Characterization and Application of a Molecularly Imprinted Polymer in Selective Adsorption of Abacavir from Polluted Water 分子印迹聚合物的合成、表征及在污水中选择性吸附阿巴卡韦中的应用

IF 1.5 4区化学

South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie Pub Date : 2020-01-01 DOI: 10.17159/0379-4350/2020/v73a13

Sharlott N. Qwane, P. S. Mdluli, L. Madikizela

{"title":"Synthesis, Characterization and Application of a Molecularly Imprinted Polymer in Selective Adsorption of Abacavir from Polluted Water","authors":"Sharlott N. Qwane, P. S. Mdluli, L. Madikizela","doi":"10.17159/0379-4350/2020/v73a13","DOIUrl":"https://doi.org/10.17159/0379-4350/2020/v73a13","url":null,"abstract":"Abacavir is an antiretroviral drug (ARVD), which has been identified as a water pollutant. To find a selective adsorbent for its extraction from water, a molecularly imprinted polymer (MIP) is proposed for its selective uptake. A 24-hour bulk polymerization process was performed for imprinting abacavir with aliquat 336 and ethylene glycol dimethacrylate, as functional monomer and cross-linking agent, respectively. Uptake of abacavir from 10 mL of aqueous solutions was performed with 40 mg of MIP at pH 5 within 60 min of contact time. MIP selectively adsorbed abacavir from water in the presence of other ARVDs (tenofovir disoproxil and efavirenz). The maximum adsorption capacity obtained for abacavir was 5.98 mg g. The adsorption mechanism was best described by the Freundlich isotherm and pseudo-second-order kinetic model, which were translated to multilayer coverage and chemisorption influenced by electrostatic attractions, respectively. The extraction efficiencies achieved for abacavir in wastewater influent, effluent and estuarine water were 67, 74 and 76 %, respectively. The synthesized MIP can be reused at least 10 consecutive times for adsorption of abacavir from polluted water without losing its extraction efficiency. This is the first study to report the application of aliquat 336 as the functional monomer in the synthesis of MIP for selective extraction of abacavir from","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67463466","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}

引用次数: 4