Bulelwa Ntsendwana

The fast growing and accumulation of electronic waste (e-waste) brings both an environmental challenge and an opportunity for valuable metal recovery. This research investigates the extraction of copper from waste printed circuit boards (WPCBs) using electro-assisted leaching with ammonia-ammonium sulfate system, employing graphite electrodes recycled from D-size Durata spent dry-cell batteries (SDBs). The electrodes were characterized using cyclic voltammetry (CV), and demonstrated quasi-reversible redox behavior with geometrical surface area of 0.0597 cm2 defined by heat shrink tube. Four independently prepared electrodes have shown good reproducibility with similar voltammogram profiles. WPCBs containing 17.4% copper were subjected to electro-assisted ammonia leaching (+0.6 V vs. Ag/AgCl, 500 rpm, 220 min, 0.5 M ammonia buffer), achieving a leaching efficiency of 88.3%. Copper was electrodeposited from the leachate onto the recycled electrodes (-0.65 V vs. Ag/AgCl, 3 h), attaining ~96% deposition efficiency. The XRD pattern confirmed the deposit as metallic FCC copper, with peaks at 2θ = 44.17° and 51.29° corresponding to the (111) and (200) planes, absent in the bare graphite electrode. SEM revealed a uniform layer of fine, nodular copper deposits, while SEM/EDS point spectra and elemental mapping confirmed uniform Cu distribution from multiple dispersed nucleation sites and the absence of other metallic elements, demonstrating high selectivity of the leaching and recovery process toward copper. This dual-waste valorization approach offers a sustainable, low-cost alternative for copper recovery, particularly relevant for developing regions.

Infectious diseases such as HIV, Malaria, Tuberculosis, are viewed as a global health threat contributing to the major causes of mortality and morbidity worldwide. The susceptibility of the patients with these infectious diseases are also prone to comorbid non-infectious diseases such as diabetes mellitus (DM), hypertension, heart diseases, chronic obstructive pulmonary diseases (COPD), and cancer, making health management even more complex especially for resource-limited regions. Diabetes, a non-communicable metabolic disorder, has been rising at an alarming rate globally, with an estimated 537 million adults living with the disease. This increasing prevalence of DM, particularly in regions heavily burdened by TB, Malaria, and HIV has created an epidemiological synergy, complicating control efforts. It is clear that early detection and surveillance is critical to and preserve and prolong health living of both humans and animals. This requires diagnostic tools that are efficiency and accessible for continuous monitoring. The biosensor technology have emerged as desirable analytical tools due to their ability to provide rapid, sensitive, and cost-effective diagnostics. They are capable of detecting specific biomarkers leading to enhanced specificity and selectivity, providing insight into disease presence, stage, and aggressiveness. These biomarkers can be found in a variety of biofluids such as blood, saliva, urine, and breath, offering minimally invasive diagnostic potential. Diagnosis using biosensors can be viewed as a confirmatory and continuous assessment of a disease, opening new avenues for predictive diagnosis over a period of time for comorbidities. Biosensing can be carried out using electrochemical, optical, lateral flow platforms. The analytical response of these platforms can be induced by utilization of nanomaterials with varying particle size, morphology, surface chemistry etc. These nanomaterials are classified based on their dimension, composition and origin, providing diverse properties, which can be fine-tined for specific disease monitoring. Other materials such as MoS2 were evaluated in the third article, where the study focused on developing of MoS2-Ag nanocomposites, which was formulated into conductive ink for fabrication of MoS2 sensor. The sensor was tested towards dopamine as the neurotransmitters, showing exceptionally high performance and ability to be used in biomedical and clinical applications. The last study, focuses on utilization of other types of sensors known as near infrared (NIR) sensors alternatives for detection of TB in both human and animals. These sensors can discriminate between various TB strains using non-invasive samples. Hence, they can be easily incorporated in portable diagnostic devices on field surveys and often epidemiological investigations as they give fresh data.The special issue also highlights challenges in upscaling of nanomaterials. An integration of modelling studies for precise control of properties, plant designs, surface engineering should be considered to unlocking the full potential of Mxenes in next-generation healthcare technologies. Additionally, the lack of frameworks for regulation of nanotoxicity especially in developing countries, where health service delivery is scarce is a hindrance that delays the market-entry of nanodiagnostics. This should inform the scientific community, government structures and funding agencies to provide proper regulation of nano-enabled diagnostics, in order to translate the research into commercial product. This will also contribute to homegrown innovations that addresses regional health management issues and fast early disease detection.

Abnormal dopamine (DA) levels in the human body are associated with severe health conditions, making their accurate detection crucial for early diagnosis and monitoring. Therefore, the development of a highly sensitive electrochemical sensor for DA detection is of significant importance in physiological, biochemical, pharmaceutical, and medical applications. In this study, screen-printed electrodes (SPEs) were fabricated using MoS₂-based conductive inks containing varying concentrations of silver nanoparticles (Ag NPs) to enhance electrocatalytic activity. The ink composition included ethyl cellulose and polyvinylpyrrolidone (PVP) as binders, providing structural integrity and adhesion, while terpineol was used as the solvent to achieve the desired viscosity for smooth and consistent printing. The printed electrodes underwent comprehensive electrochemical characterization to assess their performance, including stability, reproducibility, and sensitivity. Electrochemical analysis revealed that the SPCE/MoS₂-Ag,4 electrode exhibited the best sensing characteristics due to the optimized interaction between MoS₂ and Ag NPs, which facilitated improved electron transfer and enhanced detection capability. The electroanalytical performance of the sensors was assessed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. The SPCE/MoS₂-Ag,4 sensor demonstrated a wide linear detection range from 0.01 to 0.08 mM and an exceptionally low limit of detection (LOD) of 0.016 μM for DA. Additionally, the sensor exhibited excellent reproducibility, high sensitivity, and strong selectivity, making it a promising candidate for reliable dopamine detection in biomedical and clinical applications.

Effluents from the textile industry contain high concentrations of synthetic dyes, such as methylene blue, which are released into the environment (water bodies) and have the potential to negatively impact aquatic life, humans, and animals due to their neurotoxicity, photosynthesis disruption, and oxygen depletion. Thus, the importance of finding viable solutions for the removal of methylene blue from wastewater is emphasized. It is with this regard that the current study focuses on the effective removal of methylene blue using adsorption and WS ₂ nanosheets. The nanosheets were fabricated at different residence times and yielded black and grey WS ₂ . The morphological and surface characteristics of the nanosheets were determined by using microscopic and spectroscopic techniques. The Fourier transform infrared spectroscopy revealed typical characteristic functional groups for the WS ₂ materials between 650–1250 and 1600–3300 cm ⁻¹ , respectively. Meanwhile, scanning electron microscopy revealed flake‐like nanosheet morphologies. The point of zero charge was found to be 1.90 for grey WS ₂ and 2.47 for black WS ₂ nanosheets. The optimized adsorption conditions were found to be pH 7, initial concentration of 250 mg/L, the adsorbent dosage of 60 mg, and a contact time of 60 min. The maximum removal efficiency was 95.8% grey (WS ₂ ) and 98.9% black (WS ₂ ), respectively. The theoretical q _e values (148, 41, and 164, 02 mg g ⁻¹ ) were found to be closer to the experimental values (145,07 and 167, 56 mg g ⁻¹ ). The thermodynamics shows that the reaction was endothermic in nature, indicated by positive Δ H ⁰ , and the positive Δ S ⁰ indicted the increased randomness at the solid–liquid interface. The reusability tests at optimum conditions show that the black tungsten disulfide is highly stable and is rendered an economically feasible catalyst.

In realizing a low-carbon footprint economy, battery technology offers a transition from hydrocarbon fuels to renewable and sustainable energy systems. Recently, liquid metal batteries have been reported to demonstrate advantages for grid-scale storage due to their high power density, cyclability, and low cost. In these systems, the electrode materials play a significant role in influencing the overall energy efficiency. Furthermore, liquid metal batteries utilize earth-abundant materials with an ideal combination of metallic properties, fluidity, fast transfer kinetics, and mass (ions) transport, making them suitable for applications that require rapid charging and discharging. Interestingly, chalcogen-based materials have emerged as electrode materials of choice for the fabrication of liquid metal batteries, characterized by low melting points and flexibility. In this light, this chapter highlights the application of alternative electrodes based on chalcogen, examining their structural, morphological, and functional characteristics. The evaluation of various electrode fabrication methods and the ascertaining of the chalcogen-based electrode material’s performance in batteries will be discussed. The chapter will conclude by highlighting existing gaps and future directions on how liquid metals can be accessible for next-generation battery systems.