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Green-synthesised silver and zinc oxide nanoparticles from stingless bee honey: Morphological characterisation, antimicrobial action, and cytotoxic assessment.

This study investigated the green synthesis of silver nanoparticles (Ag-NPs) and zinc oxide nanoparticles (ZnO-NPs) using an aqueous extract of stingless bee honey (SBH) as a reducing and stabilising agent. The rich compositions of SBH containing flavonoids, phenolics, organic acids, sugars, and enzymes makes the SBH extract an ideal biocompatible precursor for the NPs synthesis. Physicochemical characterisation of the synthesised NPs was performed using UV-Vis spectroscopy, FESEM, TEM, XRD, and FTIR spectroscopy. The results revealed that the Ag-NPs and ZnO-NPs exhibited polydispersity, with size ranges between 25-50nm and 15-30nm, respectively. A majority of the NPs possessed a spherical morphology. Furthermore, the study evaluated the antimicrobial activity of the SBH-based NPs against gram-positive (Staphylococcus aureus, ATCC 43300) and gram-negative (Escherichia coli, ATCC 25922) bacteria. The findings demonstrated significantly higher antimicrobial efficacy of the Ag-NPs with a zone of inhibition (ZOI) of 16.91mm against S. aureus, and 17.43mm against E. coli compared to the ZnO-NPs which having a ZOI of 13.05mm and 14.01mm, respectively. Notably, cytotoxicity assays revealed no adverse effects of the synthesised NPs on normal mouse fibroblast (3T3) and human lung fibroblast (MRC5) cells up to 100μg/ml of concentration. These findings suggest the potential of SBH-based Ag-NPs and ZnO-NPs as safe and effective antibacterial agents for various applications, including pharmaceuticals, cosmetics, ointments, and lotions.

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Long-range atmospheric transport of organochlorine pesticides from China to South Korea: Evidence from Deokjeok Island.

The influence of transboundary air pollutants originating from the Asian continent on South Korea has been a major concern. Although organochlorine pesticides (OCPs) have been banned for several decades, they continue to be detected in the Korean environment. However, studies on the long-range atmospheric transport (LRAT) of OCPs in South Korea, particularly in background areas, remain limited. This study investigated the atmospheric levels, sources, and behavior of OCPs at Deokjeok Island, a background site near the west coast of the Korean Peninsula. Total concentrations of 24 OCPs ranged from 53.6 to 325pg/m3, which are lower than those reported by the national POPs monitoring network of South Korea and similar to levels found in other background regions in Northeast Asia. HCB (62.7pg/m3, 45%) and PeCB (46.6pg/m3, 33%) were the most dominant OCPs in the gaseous phase, whereas DDTs were predominant (1.65pg/m3, 44%) in the particulate phase. Gaseous OCPs were strongly influenced by past use and re-emissions, while ongoing emissions and LRAT were the major sources of particulate OCPs. The consistent detection of mirex provides strong evidence of LRAT. In addition, correlation analysis and the Clausius-Clapeyron equation indicated that DDTs were significantly influenced by LRAT. Concentration-weighted trajectory maps identified East, North, and Northeast China as the major source regions for gaseous OCPs, driven by re-emissions, while the primary source areas for particulate OCPs were Beijing, Hebei, Tianjin, and Shandong. Air/soil fugacity fractions showed equilibrium or net deposition for most OCPs (except PeCB), indicating the dynamic environmental behavior of OCPs influenced by past use and LRAT. This study provides evidence of LRAT of OCPs to South Korea, demonstrating the significant impact of transboundary pollution. These results highlight the importance of ongoing monitoring of both historically and currently used pesticides at receptor sites in Northeast Asia.

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Generation of disinfection byproducts by graphene quantum dot: Graphene nanostructures and water chemistry.

Graphene quantum dot (GQD), as one of the smallest graphene nanomaterials (GNMs), has the potential to be widely used due to its excellent fluorescence properties, hydrophilicity, and good biocompatibility. GQD remaining in water will generate DBPs when entering the disinfection process, and whether the generation mechanism and influencing factors are similar to those of other GNMs has not been proven and thoroughly investigated. In this study, the total amount, effect, and mechanism of DBPs formation from GQD chlorination were investigated and compared with graphene oxide (GO) and graphene. The results show that GQD produced a total trichloromethane (TCM) amount of 1019.6μg/L, which is significantly higher than that produced by GO (99.2μg/L) and graphene (7.0μg/L) at a concentration of 500mg/L. The key factors are abundant functional groups and strong hydrophilicity of GQD after the characterization and comparison of physicochemical properties. Different water chemistry conditions influence DBPs formation, such as Br- increased the formation of brominated DBPs, and high pH led to a decrease in TCM generated by GQD, which is different from other GNMs. However, NaCl concentration can be negligible. Moreover, residual GQD in natural water can participate in the DBPs formation and increase the content of DBPs, which may be influenced by the diversity of chemical composition in surface water. This study highlights the unique impact of GQD on DBPs formation.

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Alternative assessment of machine learning to polynomial regression in response surface methodology for predicting decolorization efficiency in textile wastewater treatment.

This study investigated the potential of machine learning (ML) as a substitute for polynomial regression in conventional response surface methodology (RSM) for decolorizing textile wastewater via a UV/H2O2 process. While polynomial regression offers limited adaptability, ML models provide superior flexibility in capturing nonlinear responses but are prone to overfitting, particularly with constrained RSM datasets. In this study, we evaluated decision tree (DT), random forest (RF), multilayer perceptron (MLP), and extreme gradient boosting (XGBoost) models with respect to a quadratic regression model. Our observations indicated that the ML models achieved higher R2 values, demonstrating better adaptability. However, when provided with additional data, the polynomial regression displayed a moderate predictability, whereas MLP and XGBoost exhibited indications of overfitting, while DT and RF remained robust. Both ANalysis Of VAriance (ANOVA) and SHapley Additive exPlanations (SHAP) analyses consistently emphasized the significance of operational factors (H2O2 concentration, reaction time, UV light intensity) in decolorization. The findings underscore the need for cautious validation when substituting ML models in RSM and highlight the complementary value of ML (particularly SHAP analysis) alongside conventional ANOVA for analyzing factor significance. This study offered significant insights into replacing polynomial regression with ML models in RSM.

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Innovative grease interceptor to enhance fat, oil and grease removal from the wastewater generated from food service establishments.

Commercial grease interceptors (GIs), commonly used in food service establishments, are primarily designed to treat fat, oil and grease (FOG) from handwash sink (HS) wastewater. They are generally less effective for removing highly concentrated FOG from dishwasher (DW) effluents which contain highly emulsified FOG with complex long-chain fatty acids (LCFAs). Furthermore, standard testing of GIs uses diesel fuel to simulate FOG separation; however, the flow properties of typical cooking oils and animal fats differ significantly from diesel. We developed a novel GI (bench-scale with 72L capacity) and examined the impact of various baffle configurations on FOG removal efficiency using samples containing representative FOG components of cooked oil, fat and food solids. The results demonstrated that the installation of two short baffles projecting from the top along with one short baffle projecting from the bottom in the first chamber, and another short baffle projecting from the top in the second chamber, led to FOG removal efficiencies of up to 88% and 40% for HS and DW effluents, respectively, at a hydraulic retention time (HRT) of 44min. The short baffles acted as barriers, thus enhancing the loss of kinetic energy, subsequently ensuring a quiescent flow condition, resulting in an increased HRT for effective FOG separation. The addition of alum as coagulant at 200mg/L (18.2mg of Al3+/L) significantly enhanced the removal of FOG from treated DW effluents (up to 87%), effectively reducing the concentrations of various extra-LCFAs, such as paullinic (C20:1), arachidic (C20:0), eicosadienoic acid (C20:2), mead (C20:3), eicosapentaenoic (C20:5), erucic (C22:1), cervonic (C22:6), tricosanoic acid (C23:0), lignoceric (C24:0) and nervonic (C24:1) acid by up to 99%. These findings provide significant insights into the advanced GI design, offering a proactive solution to prevent fatberg formation while promoting a more sustainable and economically viable approach to sewer management.

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Short alkyl-chained Imidazolium-based Ionic Liquids: Promising green solution or potential environmental threat?

Ionic Liquids (ILs) are currently applied in a wide variety of fields, with promising outcomes in microalgae high value biocompounds extraction. The occurrence of these compounds in natural water systems, with their characteristic stability and low biodegradability, becomes a threat worthy of attention. In the present study, Dunaliella tertiolecta, Isochrysis galbana and Rhinomonas reticulata were exposed to 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM] Tf2N) for 72, 168 and 264h, at 20 and 25°C. Obtained results suggest that the N-containing cationic ring in the selected IL could act as a nitrogen source, aiding protein synthesis and growth in the three studied microalgae. Moreover, this specific IL might become a potential eutrophication agent when discharged in aquatic ecosystems, already pressured by climate change conditions. Important lipid contents, mainly in I. galbana and associated with increased cellular energy allocation values, could be related to mitochondrial stress, which is known to be a lipid accumulation promoting factor. Hence, we hypothesise that, since [BMIM] Tf2N does not appear to impair growth or biocompound accumulation, it could be a candidate for microalgae biomass pretreatment in biodiesel production. However, its life cycle and disposal must be carefully considered.

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A high-efficient electrochemical degradation of diclofenac in water on planar and microstructured 2D, and macroporous 3D boron-doped diamond electrodes: Identification of degradation and transformation products.

The highly efficient degradation of persistent organic substances by electrochemical advanced oxidation processes (EAOPs), which don't result in the formation of potentially harmful by-products, is crucial for the future of water management. In this study, boron-doped diamond electrodes (BDDE) with three morphologies (planar 2D, microstructured 2D, and macroporous 3D) were employed for the anodic oxidation of diclofenac (DCF) in two working electrolytes (NaCl and Na2SO4). In total, 11 by-products formed during the electrochemical oxidation of DCF were identified via HPLC-HRMS. The identification of degradation products revealed the formation of various active chlorinated species. The utilization of a chlorine-free Na2SO4 electrolyte resulted in the formation of greater number of chlorinated species, while their elimination required a longer period compared to the use of NaCl electrolyte. The formation of by-products was also influenced by the specific type of BDD electrode, which was associated with variations in applied current density. This led to an uneven distribution of dichloro (2D BDDE) and trichloro (3D BDDE) patterns. However, none of the products showed signs of a high level of persistence. The results revealed that the type of electrolyte is the most significant factor affecting the removal efficiency of DCF, while the different electrode morphologies do not lead to differences in the removal rates. The electrode type exerted a notable influence on the removal rates, which was associated with varying applied current densities, exclusively in the case of the Na₂SO₄ electrolyte. Over 99 % removal efficiency for DCF in NaCl, with power consumption of 1.8 kWh m-3 was achieved.

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