Original work in all branches of chemistry is published in the South African Journal of Chemistry. Contributions in English may take the form of papers, short communications, or critical reviews.

The South African Journal of Chemistry publishes original research across all branches of chemistry. Contributions in English may include papers, short communications, or critical reviews.

《南非化学杂志》（South African Journal of Chemistry）发表所有化学领域的原创研究。欢迎以英语提交论文、短篇通讯或批判性综述。

South African Journal of Chemistry

ABSTRACT Platinum has been widely used as the catalyst of choice for the production of hydrogen in the hybrid sulphur (HyS) cycle. In this cycle, water (H2O) and sulphur dioxide (SO2) react to form sulphuric acid and hydrogen. However, the surface reactivity of platinum towards H2O and SO2 is not yet fully understood, especially considering the competitive adsorption that may occur on the surface. In this study, we have carried out density functional theory calculations with long-range dispersion corrections [DFT-D3-(BJ)] to investigate the competitive effect of both H2O and SO2 on the Pt (001), (011) and (111) surfaces. Comparing the adsorption of a single H2O molecule on the various Pt surfaces, it was found that the lowest adsorption energy (Eads = -1.758 eV) was obtained for the dissociative adsorption of H2O on the (001) surface, followed by the molecular adsorption on the (011) surface (Eads = -0.699 eV) and (111) surface (Eads = -0.464 eV). For the molecular SO2 adsorption, the trend was similar, with the lowest adsorption energy (Eads = -2.471 eV) obtained on the (001) surface, followed by the (011) surface (Eads = -2.390 eV) and (111) surface (Eads = -1.852 eV). During competitive adsorption by H2O and SO2, the SO2 molecule will therefore preferentially adsorb onto the Pt surface. If the concentration of SO2 increases, self-reaction between two neighbouring SO2 molecules may occur, leading to the formation of sulphur monoxide (SO) and -trioxide (SO3) on the surface, which could lead to sulphur poisoning of the Pt catalytic surface. Keywords: Platinum, water, sulphur dioxide, hydrogen, adsorption, density functional theory.

Marietjie J. Ungerer

David Santos-Carballal

Cornelia G.C.E. van Sittert

Nora H. de Leeuw

Competitive Adsorption of H2O and SO2 on Catalytic Platinum Surfaces: a Density Functional Theory Study

催化铂表面H2O与SO2的竞争吸附：密度泛函理论研究

ABSTRACT We have employed density functional theory (DFT) calculations to investigate the adsorption of molecular oxygen and hydrogen on 3d transition metal (TM) surfaces with varying ordered magnetic structures in the bulk, namely ferromagnetic Fe(110), Co(0001), Ni(111) and diamagnetic Cu(111). The trend observed in the energies of adsorption was compared with the magnetic moment of the cell using the d-band centre model of chemisorption and the Stoner model of magnetic energy. As the gap between the d-band centre and the Fermi level of the TM decreases, more antibonding orbitals are present above the Fermi level and thus unoccupied, leading to stronger binding. Correspondingly, the shift in the d-band centre decreases the density of states (DOS) at the Fermi level giving rise to the ordered magnetic structure. Keywords: d-Band centre, chemisorption, Hedvall effect, magnetism.

Mogamat A. Peck

Michael Claeys

Density Functional Theory Study of the Adsorption of Oxygen and Hydrogen on 3d Transition Metal Surfaces with Varying Magnetic Ordering

密度泛函理论研究氧和氢在具有不同磁序的3d过渡金属表面吸附

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.

Muhammad Hafeez

Ruzma Shaheen

Bilal Akram

Muhammad Naeem Ahmed

Zain- ul-Abdin

Sirajul Haq

Salah Ud Din

Maryum Zeb

Muhammad Abdullah Khan

Green Synthesis of Nickel Oxide Nanoparticles using Populus ciliata Leaves Extract and their Potential Antibacterial Applications

使用白杨叶提取物绿色合成氧化镍纳米颗粒及其潜在的抗菌应用

ABSTRACT This work evaluated the extraction efficiency of silica from diatomaceous earth (DE) by conventional solvent extraction (CSE) and ultrasound-assisted extraction (UAE) under basic and acidic (HCl) conditions utilizing response surface methodology (RSM). A common statistical model was used to get the best percentage yield and percentage purity using RSM. Experimental parameters such as stirring time, NaOH concentration (for CSE), sonication time, NaOH/HCl concentration, cycle and amplitude (for UAE methods) were optimized using central composite design (CCD). The analytical responses, that is, percentage yield and percentage purity, were analyzed using ANOVA and regression analysis. The linear coefficient of determination, R2, was high and precise. The overall yield and purity were highest for the UAE method under acid condition (pH 1-2, approximately), making it the most effective silica extraction method from DE. For this method, the optimal conditions for extracting Si from DE were 2 h of sonication, 220 mL of 2.82 M HCl as a leaching/extracting medium, 0.524 cycles and 72.6 % of amplitude. Under these conditions, 82 % of silica was yielded with a purity of about 95 %. The experimental results indicate that high-quality silica can be produced from DE in high yield so that DE can be an alternative silica source. Keywords: Diatomaceous earth, silica, response surface methodology, ultrasound-assisted extraction, conventional solvent extraction.

Oisaemi U. Izevbekhai

Wilson M. Gitari

Nikita T. Tavengwa

Optimization of Silica Extraction from Diatomaceous Earth using the Central Composite Design of Response Surface Methodology

响应面法中心复合设计优化硅藻土中二氧化硅提取工艺

ABSTRACT Plant-based material, namely bitter kola leaf, as an additive for surface modification of mild steel in H2SO4 solution was thoroughly scrutinized using electrochemical, theoretical and optimization techniques. The functional groups, of the biomolecules of the bitter kola leaf extract, were examined using Fourier transform infrared spectrometry (FTIR) and gas chroma-tography-mass spectrophotometry (GC-MS). For clarification purpose, scanning electron microscopy (SEM) was used to inspect the texture of the degraded and inhibited steel after 21 h of immersion. For the response surface methodology (RSM), central composite design of Design-Expert Software was used to optimize the inhibition efficiency as a function of acid concentration, inhibitor concentration, temperature and time. The optimum inhibition efficiency of 93 % was obtained at 0.9 g L-1 bitter kola leaf. The mutual correlation between the considered variables and expected response was adequately interpreted by a quadratic model. The fitness of the model was justified by the following standards which include P-value (&lt;0.0001), adjusted R2 (0.9843), R2 (0.991), adequate precision (43.14) and coefficient of variation (2.59). Bitter kola leaf extract behaved as a mixed-type inhibitor and adequately satisfied Langmuir adsorption isotherm. Furthermore, the theoretical modelling revealed the most active molecule of bitter kola leaf responsible for the overall inhibition. The experimental and theoretical results are in agreement that bitter kola leaf extract is a viable corrosion inhibitor of mild steel in H2SO4 solution. Keywords: Acid corrosion, electrochemical study, green extract, mild steel, optimization study, theoretical modelling.

Valentine Chikaodili Anadebe

Patrick Chukwudi Nnaji

Nkechinyere Amaka Okafor

Joseph Okechukwu Ezeugo

Fidelis Ebunta Abeng

Okechukwu Dominic Onukwuli

Evaluation of Bitter Kola Leaf Extract as an Anticorrosion Additive for Mild Steel in 1.2 M H2SO4 Electrolyte

苦柯叶提取物作为1.2 M H2SO4电解质中低碳钢防腐蚀添加剂的评价

ABSTRACT The occurrence of pharmaceuticals in various wastewater treatment plants (WWTPs) and their discharge into the surface water are existing global challenges. However, such challenges are more detrimental in developing countries due to the aging infrastructure and its vandalism influenced by poverty, resulting in the illegal breakdown of the WWTPs. This study investigated the presence of efavirenz, ibuprofen, naproxen, sulfamethoxazole, and trimethoprim in WWTPs. Ultrasound-assisted extraction (UAE) followed by solid-phase extraction (SPE) was used to extract these pharmaceuticals in sludge samples, with wastewater extracted with only the latter. This was followed with analysis using a high-performance liquid chromatography-photo-diode array detection system. Recoveries found after spiking the samples with analytes at different concentrations ranged from 56 to 117%. An antibiotic, sulfamethoxazole, was among the prominent drugs in untreated wastewater with its concentration reaching 77 ug L-1. All the analytes were detected in sludge samples, with naproxen having the highest concentration of 13.35 ng g-1. The pharmaceutical with the lowest removal efficiency (2-12%) in WWTPs was efavirenz, while other drugs were fairly removed from wastewater. Overall, the findings of this study indicate the dysfunctionality of selected WWTPs in the Eastern Cape province of South Africa due to the release of high amounts of pharmaceuticals into the surface water which can be detrimental to humans, animals, and aquatic life.

R Netshithothole

M Managa

T Botha

L Madikizela

Occurrence of selected pharmaceuticals in wastewater and sludge samples from wastewater treatment plants in Eastern Cape province of South Africa

南非东开普省污水处理厂废水和污泥样品中选定药物的出现情况

This study examined the potential of electrooxidation techniques for treating Rhodamine B dyestuff from aqueous solutions made from synthetic wastewater. The Rhodamine B dyestuff was electro-oxidized by using five anodes coated with "Ti/IrO2/RuO2" as anode material and five stainless steel cathodes as cathode material. The initial concentration of Rhodamine B, the type of support electrolyte, the current density, and the initial pH of the wastewater were evaluated. KCl, NaCl, NaNO3 and Na2SO4 were used as supporting electrolytes. Colour removal performance was optimum when the initial pH was approximately 5, the current density was 1.78 mA cm-2, and the supporting electrolyte was NaCl at a concentration of 10 mM. Under ideal circumstances, colour removal was shown to be 99.72% effective.

S Günaslan

B Fil

C Elgün

S Cihan

Colour removal from wastewaters by an electrooxidation method

电氧化法去除废水中的颜色

Biodiesel is considered to be more friendly to the environment than petroleum-based fuels, cheaper and capable for producing greener energy which contributed positively in boosting bio-economy. In this work, waste cooking oil (WCO) is converted into biodiesel utilizing a waste eggshell (CaO) nano-catalyst in an effort to discover environmentally beneficial and economically viable processes for social and economic development. The eggshell-based CaO catalyst developed for the production of ecologically friendly biodiesel at a reduced price is calcined at temperatures between 600 and 1100 °C. The synthesized catalysts were assessed in terms of their physical and chemical qualities via BET, TGA and XRD analysis. This revealed that, besides displaying exceptional transesterification activity, the catalyst synthesised at 950 °C also offered the greatest biodiesel yield. Transesterification, used in biodiesel generation, was used to evaluate the catalytic performance of manufactured catalysts under several reaction circumstances. Under prime reaction conditions i.e., a reaction time of 3 hours, an ethanol-oil molar ratio of 9:1, and a catalyst amount of 4 wt.%, it was ascertained that a catalyst which had calcined at 950 °C demonstrated excellent transesterification activity and delivered a ceiling yield of 88% fatty acid ethyl esters. The production of FAME was confirmed by using gas chromatography-mass spectroscopy (GC-MS). Fuel properties of fatty acid ethyl ester complied with ASTM D 6751 which indicated that it would be an appropriate alternative form of fuel.

R Alsaiari

E Musa

M Rizk

Effects of calcination temperature of eggshell-derived CaO as a catalyst for biodiesel production from waste cooking oil

蛋壳衍生的CaO作为废食用油生物柴油生产催化剂的煅烧温度影响

In this study, natural rubber (NR) and low-density polyethylene (LDPE) were melt blended in a 2-roll mill to fabricate NR/LDPE composites with liquid natural rubber (LNR) and hematite (a-Fe2O3) as compatibilizer and filler respectively. The effects of liquid natural rubber (LNR) on the mechanical properties and morphology of NR/LDPE composites were investigated. NR/LDPE composites were prepared in three different compositions of 70/30, 50/50 and 30/70, with filler content at varying concentrations (3, 5 and 7 g) while LNR was kept at 10 g for the modified composites. Results obtained showed increment in the tensile strength, tensile modulus, compressive and flexural properties but with decrease in the elongation at break the a-Fe2O3 and LDPE contents increase. The modification of the composites with LNR further enhanced the mechanical properties. FTIR spectrum of LNR revealed a peak at 3395 cm-1 suggesting the hydroxyl (OH) end group attached to the LNR chain due to the photochemical degradation of NR to yield LNR. FTIR spectra of the selected composites showed the presence of iron oxide bond (Fe-O) at 571 cm-1, 467 cm-1 and 463 cm-1 due to the incorporation of a-Fe2O3 filler particles in the composites. SEM images showed improved matrix/filler interfacial adhesion induced by the LNR compatibilizer.

Henry Obasi

Franklin Opara

Genevive Onuegbu

Kate Chike

Godwin Onyeagoro

Fabrication, characterization and mechanical properties of hematite (a-Fe2O3) filled natural rubber/low-density polyethylene composites

赤铁矿（α-Fe2O3）填充天然橡胶/低密度聚乙烯复合材料的制备、表征及力学性能

Natural kaolinite obtained from Share, Nigeria was treated with ammonium carbonate to enhance the adsorption capacity. The optimum operating conditions for the adsorption of metal ions on the natural clay (SK clay) were employed on the ammonium carbonate-treated clay (SK-AC clay). The adsorption data were analysed using adsorption isotherm and kinetic models. The statistical p-values were less than 0.05, indicating that the model terms are significant for the adsorption of the metal ions. The pseudo-second-order kinetic model best describes the metal ions adsorption mechanism. The activation energy values less than 40 kJ mol-1 obtained indicated physisorption. Langmuir adsorption isotherm model fitted the adsorption data for Fe2+, Zn2+ and Cr6+ ions while the Freundlich model fitted Pb2+ ions adsorption. Analysis of thermodynamic parameters shows the adsorption is spontaneous and endothermic. The ammonium carbonate-modified clay exhibited an increase in adsorption capacity from 10.74 to 13.60 mg g-1, 16.48 to 17.38 mg g-1 and 11. 96 to 13.8 mg g-1 for Fe2+, Pb2+ and Zn2+ ions while uptake of Cr6+ decreased from 8.75 to 7.25 mg g-1. The results showed that the adsorption of Fe2+, Pb2+ and Zn2+ ions onto kaolin-containing cowlesite can be enhanced by treating it with ammonium carbonate.

J Lawal

E Odebunmi

F Adekola

Removal of heavy metals from aqueous solutions by adsorption using natural and ammonium carbonate modified kaolinite clays

利用天然及碳酸铵改性高岭土吸附去除水溶液中重金属

Abbreviation	S.Afr.j.chem.
Journal Impact	0.82
Quartiles(Global)	CHEMISTRY, MULTIDISCIPLINARY(Q4)

ISSN	0379-4350, 1996-840X
h-index	27

Publication Information	Publisher: Bureau for Scientific Publications，Publishing cycle: Monthly，Journal Type: journal，Open Access Journals: Yes
Basic data	Year of publication: 1996，Proportion of original research papers: 100.00%，Self Citation Rate:0.00%， Gold OA Rate: 86.96%
Average review cycle	网友分享经验：>12周，或约稿
Average recruitment ratio	网友分享经验：容易

South African Journal of Chemistry

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