The disinfection of wastewater using nanoparticles (NPs) has become a focal area of research in water treatment. In this study, zinc oxide (ZnO) NPs were synthesized using the microwave heating crystallization technique and characterized using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Qualitative well diffusion and quantitative minimum inhibitory concentration (MIC) tests were conducted to determine the antimicrobial activity of ZnO NPs against selected waterborne pathogenic microbes. FTIR spectral studies confirmed that the binding of urea with Zn occurs through Zn–O stretching. XRD confirmed the crystallized identity in a hexagonal ZnO wurtzite-type structure. The formation of zones of inhibition and low MIC values in the antimicrobial analysis were indicative of the effective antimicrobial activity of zinc oxide nanoparticles against the test microorganisms. The application of metallic nanoparticles in water treatment could curb the spread of waterborne microbial diseases.

Macadamianutshell powder oxidized by hydrogen peroxide solutions (MHP) was functionalized by immobilizing 1,5′-diphenylcarbazide (DPC) on its surface. The effectiveness of grafting was confirmed by the Fourier transform infrared spectrum due to the presence of NH and C=C stretches at 3361, 1591, and 1486 cm⁻¹, respectively, on the grafted material which were absent in the nongrafted material. Thermogravimetric analysis revealed that the presence of DPC on the surface ofMacadamiashells lowered the thermal stability from 300°C to about 180°C owing to the volatile nature of DPC. Surface roughness as a result of grafting was appreciated on the scanning electron microscopy images. Parameters influencing the adsorptive removal of Cr(VI) were examined and found to be optimal at pH 2, 120 min, 150 mg/L, and 2.5 g/L. Grafting MHP with DPC leads to an increase in the Langmuir monolayer capacity from 37.74 to 72.12 mg/g. Grafting MHP with DPC produced adsorbent with improved removal efficiency for Cr(VI).

The occurrence of residual antifungal agents through indiscriminate prophylactic use and inappropriate disposal has been reported in wastewater treatment plants (WWTPs), surface water, and groundwater environments. Opportunistic pathogenic aquatic yeasts develop resistance to commonly used antifungal agents through continued exposure to residual antifungal agents in environmental waters. This poses a major public health concern. The present review attempts to provide a brief description of antifungal drugs, with a focus on the most widely used class of antifungal drugs, the azoles, as emerging contaminants in environmental water. Routes of exposure of azole antifungal drugs in wastewater treatment plants, surface water, and groundwater are discussed. The presence of pathogenic yeasts in environmental water, the associated azole resistance, and the risk of exposure to humans and microbiota are highlighted. Management actions needed to curtail the spread and minimise the risks are also indicated. Further research on the occurrence of antifungal agents in wastewater and environmental water is vital to better understand and mitigate the associated health-related risks.

Electroplating and metalworking industries produce enormous amounts of waste containing heavy metals in their effluents, leading to potential threats to biotic and abiotic life. According to regulation, heavy metal contamination must be kept within the regulated standard of a few parts per million, which has led to a recent pique in interest in the utilization of nanofiltration technology for metal recovery. The effect of feed pH, pressure, metal concentration, and oxidation of metal on the rejection of heavy metal ions using three commercial nanofiltration membranes (NF, NF90, and NF270) were explored. To begin, studies of electrolyte salts, contact angle, and water permeability were employed to characterize the nanofiltration membranes. A dead-end module was used to test the permeation and retention capacities of the nanofiltration membranes. The results showed an increase in salt rejection for all metals examined irrespective of the membrane, at a pH below the isoelectric point. For divalent cations, the NF90 membrane achieved recovery capacities of 97% and 85% at 200 ppm and 20 ppm respectively, as compared to the recovery observed for Ni²⁺, Cu²⁺, and Pd²⁺ ions by NF and NF270. At a pH 2, 20 ppm and 5 bar, the NF90 membrane had the highest percent recovery, but at a pH 3, the recovery was at 95%. Mono and divalent stable Ag+ and Ni²⁺ ions showed a comparatively high percent recovery as compared to Pd²⁺ and Cu²⁺, which have high molecular weight and charge effect. In the presence of chelating agents, the membrane surface area is increased, resulting in high divalent ion recovery capacities due to favourable interaction with the polyamide functional group of the membranes. This study establishes the significance of oxidation in high removal efficiency cation in varying experimental conditions.

Toxins in water, such as metal ions and dyes, have become a global challenge to humanity by causing several serious illnesses. Removal of these toxins from water is needed for human health and environmental concerns. This work investigated the use of hemp seeds as an environmentally friendly adsorbent for applications in water treatment. Pristine hemp seeds (PHSs) were carbonized at 500 and 700 °C to obtain carbon-based hemp seeds (CHS-500 and CHS-700 for the removal of cadmium and methylene blue. The morphological and functional groups of the carbonized adsorbents and pristine hemp seeds were determined by SEM and FTIR. Isotherm studies showed that the Langmuir model best described the adsorption process based on homogenous surfaces. The maximum adsorption capacities were obtained with CHS-700 with a 36.88 and 52.61 mg/g uptake of cadmium and methylene blue, respectively. The effect of contact time showed that the sorption process rate was rapid initially, followed by a slower increment due to the saturation of active sites. ΔS° values were positive, demonstrating the increased randomness and degree of freedom of cadmium and methylene blue in water. The adsorption trends for cadmium and methylene blue by CHS-500 and CHS-700 increased as the temperature rose; a decrease was observed for adsorption by PHSs. This result suggests that the adsorption was endothermic for CHS-500 and CHS-700 and exothermic for PHSs. The pseudo-second-order model better described the uptake of both pollutants by the adsorbents. This research illustrates the great potential of carbon-based hemp seeds in removing cadmium and methylene blue dye from water.

The emphasis of previous studies has targeted the development of insulin mimic with little attention given to the development of metabolic enzyme inhibitors. Our focus is to synthesise nine o-hydroxy and p-nitro-azomethine analogues, investigate their digestive enzyme inhibitory capacity, as well as the antioxidant and antimicrobial activities. The substituted Schiff bases were analysed using thermal gravimetric analyser (TGA), X-ray diffractometer (XRD), nuclear magnetic resonance spectroscopy (NMR), elemental analyser, and Fourier-transform infrared spectroscopy (FT-IR). Determination of synthetic yield revealed that the o-hydroxy analogues produced the highest yield of ≥77.1% compared to p-nitro and unsubstituted analogues. Spectra study showed the presence of azomethine stretching vibration at 1698–1613 cm⁻¹, proton signals at δ 8.46–9.81, and carbon signals at δ 145.95–159.53 ppm. Investigation into the thermal property indicated an elevated melting point for the o-hydroxy analogue, compared to the p-nitro derivative which showed high stability to heat. There are similarities in crystalline structure with few unique patterns suggesting different substituent group. The antioxidant activities of the substituted analogues registered low half maximal inhibitory concentration (IC₅₀), with exception to the ferric reducing power; indicating that the Schiff bases are weak siderophores. All nine Schiff bases were bacteriostatic or fungistatic at the screened concentrations; however, the nitro-substituted analogues have an enhanced activity with Minimum Inhibitory Concentration (MIC) values of 0.03–2.54 µM. Both o-hydroxy and p-nitro-substitution does not improve the antifungal activity of the compounds against A. niger. The o-hydroxyl and p-nitro Schiff base derivatives showed enhanced activity towards the inhibition of $\mathsf{\alpha }$ -amylase and α-glucosidase by hydroxylation and glycosylation, respectively. Although, hydroxy derivatives of sulphonic acid derived Schiff base slightly decreased the activities on α-glucosidase and α-amylase. Our findings suggest that p-nitro substitution enhances the in vitro nonenzymatic activity while the o-hydroxy derivatives are good hydrolase inhibitors. Therefore, substituent modification can be used as an enhancement technique in designing novel pharmacophore.