Evaluation of corrosion inhibition of essential oil-based inhibitors on aluminum alloys

There is a high demand for eco-friendly, effective, and highperformance corrosion inhibitors for industrial applications. Thus, the corrosion property of aluminum alloys was studied in essential oil-containing sodium chloride solution at various concentrations. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), surface tests, and weight loss analysis were used to study the corrosion inhibition mechanism of the essential oil. The essential oil showed the highest inhibition efficiency of 97.01% at 1000 ppm. A high efficiency of 96.03% was achieved even after 168 h of exposure. The potentiodynamic polarization test showed that the essential oil is a mixed-type inhibitor. EIS results show better adsorption of the oil on the surface of the aluminum at increased inhibitor concentrations. The Langmuir’s adsorption isotherm model was found to describe the adsorption behavior. The surface morphology of the uninhibited and inhibited specimens examined by a scanning electron microscope equipped with an energydispersive X-ray spectroscope confirmed the protective film of the inhibitor molecules on the aluminum surface.http://pubs.acs.org/journal/acsodfam2023Chemical Engineerin

Evaluation and risk assessment of heavy metals in surface water collected along the Isipingo River, KwaZulu-Natal, South Africa

In this study, the pollution levels, sources, and ecological risks associated with five selected heavy metals (chromium, copper, iron, lead, and zinc) were evaluated in surface water, soil, and sediment systems along the Isipingo River, KwaZulu-Natal, South Africa. The surface water, soil and sediment samples collected along the river, were preserved, transported, and stored followed the standard procedures. Soil and sediment samples were digested for heavy metal determination using a microwave digestion system. The digested samples were quantitatively analysed using an inductively coupled plasma optical emission spectrometer (ICP-OES). The results demonstrate that majority of the targeted heavy metals were found below the detection limits in surface water except for iron (Fe), which was found within the concentration range of 9.54 to 46.76 µg/L. Lead was found below the detection limit in water, soil, and sediment samples, while other heavy metals were within the range not detected (ND) to 0.222 µg/kg dry weight and 0.212 µg/kg dry weight in soil and sediment respectively. The ecological risk assessment of the studied metals in soil and sediment systems from this river signified that water from this river had less probable potential adverse effects on both animals and humans as well as benthic organisms.https://www.tandfonline.com/loi/geac20hj2024Chemical EngineeringSDG-06:Clean water and sanitatio

Mechanistic study of cefixime degradation with an atmospheric air dielectric barrier discharge – influence of radical scavengers and metal ion catalyst

DATA AVAILABILITY : Data will be made available on request.Please read abstract in the article.The Government of the United Kingdom through The Royal Society FLAIR award.https://www.elsevier.com/locate/seppurhj2024Chemical EngineeringSDG-09: Industry, innovation and infrastructur

Embracing the future of circular bio-enabled economy : unveiling the prospects of microbial fuel cells in achieving true sustainable energy

DATA AVAILABILITY : Sources of data collected have been mentioned in the text.Sustainable development and energy security, highlighted by the United Nations Sustainable Development Goals (SDGs), necessitate the use of renewable and sustainable energy sources. However, upon careful evaluation of literature, we have discovered that many existing and emerging renewable energy systems (RESs) prioritize renewability over true sustainability. These systems not only suffer from performance inconsistencies and lack of scalability but also fall short in fully embodying the principles of sustainability and circular economy. To address this gap, we propose considering microbial fuel cells (MFCs) as a viable alternative and integral part of the renewable energy ecosystem. MFCs harness the omnipresence, abundance, and cost-effectiveness of their essential components, making them a promising candidate. Through our comprehensive analysis, we shed light on the limitations and advancements of this technology, which underscore the remarkable potential of MFCs to revolutionize our perception of clean, sustainable energy.The National Research Foundation, South Africa and the the Royal Society. Open access funding provided by University of Pretoria.https://www.springer.com/journal/11356am2024Chemical EngineeringSDG-07:Affordable and clean energ

Non-thermal plasma review : assessment and improvement of feasibility as a retrofitted technology in tertiary wastewater purification

DATA AVAILABILITY STATEMENT: Authors will make relevant data available on request.Chlorination, ozonation and non-thermal plasma water purification technologies were compared in terms of their effectiveness, efficiency, capital and operating costs, energy yield and chemical demand. Retrofitting plasma technology to chlorination plants offered the lowest capital cost (ZAR 14,000 or USD 253,376 based on the current South African Reserve Bank rate of ZAR/USD of 18.0983) and the most effective contaminant removal (of the three possible combinations). However, this combination yielded the highest operating costs (ZAR 586,000 per annum or USD 10.6 million) and the lowest energy efficiency. It was concluded that retrofitting chlorination plants with plasma technology is feasible. However, plasma generators should be redesigned to consume less energy or to operate using renewable energy. Furthermore, research should be performed on contaminants of emerging concern to establish a deadline after which their concentration must not exceed a specified limit. This will accelerate the implementation of plasma technology and secure the health of our posterity.Global Challenge Research Funds of United Kingdom.https://www.mdpi.com/journal/applsciChemical Engineerin

Inactivation of antibiotic-resistant bacteria and antibiotic-resistance genes in wastewater streams: Current challenges and future perspectives

The discovery of antibiotics, which was once regarded as a timely medical intervention now leaves a bitter aftertaste: antimicrobial resistance (AMR), due to the unregulated use of these compounds and the poor management receiving wastewaters before discharge into pristine environments or the recycling of such treated waters. Wastewater treatment plants (WWTPs) have been regarded a central sink for the mostly unmetabolized or partially metabolised antibiotics and is also pivotal to the incidence of antibiotic resistance bacteria (ARBs) and their resistance genes (ARGs), which consistently contribute to the global disease burden and deteriorating prophylaxis. In this regard, we highlighted WWTP-antibiotics consumption-ARBs-ARGs nexus, which might be critical to understanding the epidemiology of AMR and also guide the precise prevention and remediation of such occurrences. We also discovered the unsophistication of conventional WWTPs and treatment techniques for adequate treatment of antibiotics, ARBs and ARGs, due to their lack of compliance with environmental sustainability, then ultimately assessed the prospects of cold atmospheric plasma (CAP). Herein, we observed that CAP technologies not only has the capability to disinfect wastewater polluted with copious amounts of chemicals and biologicals, but also have a potential to augment bioelectricity generation, when integrated into bio electrochemical modules, which future WWTPs should be retrofitted to accommodate. Therefore, further research should be conducted to unveil more of the unknowns, which only a snippet has been highlighted in this study

The production of biogenic silica from different South African agricultural residues through a thermo-chemical treatment method

A thermo-chemical treatment method was used to produce biogenic amorphous silica from South African sugarcane and maize residues. Different fractions of South African sugarcane (leaves, pith, and fiber) were processed for silica production. The biomass samples were leached with either 7 wt% citric acid or 7 wt% sulfuric acid at 353 K for 2 h prior to being rinsed, dried and combusted using a four-step program ranging from room temperature to 873 K in a furnace. The characterization of the pre-treated biomass samples was conducted using thermogravimetric analysis (TG/DTA), X-ray fluorescence analysis (XRF) and elemental analysis (CHN), while the final products were characterized by XRF, X-ray diffraction (XRD), elemental analysis, nitrogen physisorption and scanning electron microscopy (SEM). Citric acid pre-treatment proved to be an attractive alternative to mineral acids. Amorphous biogenic silica was produced from sugarcane leaves in good quality (0.1 wt% residual carbon and up to 99.3 wt% silica content). The produced biogenic silica also had great textural properties such as a surface area of up to 323 m2 g −1 , average pore diameter of 5.0 nm, and a pore volume of 0.41 cm3 g −1 .The National Research Foundation of South Africahttps://www.mdpi.com/journal/sustainabilityChemical Engineerin

Empirical prediction of optimum process conditions of spark plasma-sintered magnesium composite (AZ91D-Ni-GNPs) using response surface methodology (RSM) approach

In the present study, nickel (Ni) and graphene nanoplatelets (GNPs) are considered as ideal reinforcements for Mg-9Al-1Zn (AZ91D) magnesium alloy to form metal matrix composites (MMCs) because of their excellent mechanical properties. It is essential to utilize effective manufacturing techniques to develop AZ91D magnesium (Mg) alloy-nickel-graphene nanoplatelets (AZ91Z-Ni-GNPs) MMCs. Hence, the spark plasma sintering method is used to fabricate AZ91D-Ni-GNPs composites. HRTEM, OM, SEM, EDS, XRD, and Raman spectroscopy were used to investigate the microstructure, crystallinity, and elemental composition of both the blended powder and the sintered composites. GNPs and Ni were well-dispersed in the AZ91D Mg matrix, and effective interfacial bonding is formed between GNPs, Ni, and Mg alloy matrix powder before sintering. A Response Surface Methodology (RSM) with a central composite design was used to design the experiments by considering two variables, i.e., sintering temperature and pressure. The method was adopted to eliminate the trial-by-error approach. Using the data generated, quadratic regression models were developed for the relative density (g/cm3), and Vickers hardness (HV) of the MMCs, and the parametric effects were explained via RSM. The process parameters were optimized, and the effective interaction between two descriptive variables (process parameters) on the relative density, hardness, and microstructural properties of Mg-based composites was investigated. Validation of the experimental run was performed using optimal process parameters acquired from the analyses to demonstrate the enhancement in the properties of the sintered composites. It was observed that the sintering temperature had a major influence on the relative density and hardness properties (responses). The optimal relative density and hardness obtained for AZ91D-Ni-GNPs composites were 1.723 g/cm3 and 93.21 HV, respectively. The addition of GNPs to AZ91D-Ni produced material with improved properties.The Department of Chemical Engineering of the University of Pretoria and Faculty of Engineering, the Built Environment and Information Technology, Pretoria, South Africa.https://link.springer.com/journal/133692023-07-22hj2023Chemical Engineerin

Modeling and Simulation of Low Current Atmospheric and High-Pressure Helium Plasma Discharges

A plasma discharge in a Helium gas reactor at different pressures and at low currents (0.25-0.45 A) has been investigated by Computational Fluid Dynamic modeling coupled with the Maxwell's equations. The results show different discharge dynamics across the pressure range (0.1-8 MPa), with an arc discharge obtained at high pressure and a low current arc discharge observed at atmospheric pressure. A large density gradient at higher pressure causes a strong natural convection effect in the reactor. This density gradient affects drastically the discharge shape and the velocity field at high pressures while at atmospheric pressure, a lower density gradient was observed resulting in a low velocity magnitude. It has been observed that the velocity magnitude is not affected by the electric current. The discharge electric potential has been calculated by considering the electrical characterization of the electrodes and numerical results have been compared with experimental results. The comparison shows a good agreement between the measured and calculated discharge electric potential at lower pressures. These devices can be used as plasma sources for wastewater treatment

Microstructure, Mechanical, Tribological and Synergistic strengthening mechanisms of nickel/graphene nanoplatelets hybrid reinforced AZ91D magnesium-based matrix composites via spark plasma sintering

AZ91D-Ni-graphene nanoplatelets (GNPs) Mg-based composites were effectively consolidated using spark plasma sintering (SPS). The - reinforcement in the AZ91D Mg alloy varies from 0 wt% to 2 wt%, with Ni constituent fixed at 1.5 wt%. Scanning electron microscope, Transmission electron microscope, X-ray diffraction and Raman spectroscopy were utilised to investigate the morphology of the powder and sintered compact. The synergistic strengthening offered by the inclusion of GNPs comprising grain refinement (ΔσHall−Petch), load transfer from AZ91D-Ni Mg-based alloy matrix to GNPs reinforcement (ΔσLT), dislocations strengthening due to the mismatch in the coefficient of thermal expansion (CTE)(ΔσCTE), modulus mismatch (Δσmm), and strengthening due to Orowan (Δσorowan) was investigated. Experimental results indicate that the addition of GNPs contributes minimally to the densification of the compacts, increasing from 97% to 98.1% with increasing GNPs. However, significant improvements were obtained for other properties investigated, such as a microhardness, which increased from 67.4 to 89.7 H V, nano hardness from 4744.9 to 18,251.3 MPa, an elastic modulus from 84.53 to 243.75 GPa and wear rate from 5.21 × 10−3 to 3.85 × 10−3 mm3/N/m under 10 N load with an increase in GNPs content. This study establishes the capability of GNPs as efficient reinforcement in manufacturing metal matrix composites with enhanced mechanical and tribological properties