With the exacerbation of industrialization, water treatment has become a necessary step for the eradication of dyes, heavy metals, oils, pharmaceuticals, and illicit drugs. These pollutants pose an impending threat to the health of humans by causing chronic or acute poisoning. Albeit they are noxious, the presence of some metals in lower concentrations is indispensable for human health. 3D printing (additive manufacturing) (3DP) can contrive nearly any complicated geometric form in a wide array of objects among various scales by a layer-wise method of manufacturing, which is more indubitably designed than any other conventional method. 3DP could remodel the existing patterns of membrane housing and possibly trim down the power demand and chemical use in saltwater desalinating and wastewater purification plants. Membranes that are 3D printed with correctly arranged apertures and shapes enhance material transport and flow athwart the surface of the membrane and at once lessen membrane soiling. This kind of technology forges membranes of polymers, biopolymers, alloys, metals, and ceramics via computer-aided design (CAD). A polylactic acid porous super-hydrophobic membrane with pore size in the range 40–600 μm showed 99.4% oil-water separating power and 60 kL h⁻¹ m⁻² flux when the pore size was tuned to 250 μm via CAD-aided 3D printing technology. This review focuses on the ability of 3D-printed membranes for the efficient removal of toxic pollutants from wastewater. Graphical abstract 3D-printed membranes for water treatment

Activated carbons (ACs) from Pinus canariensis cones were developed by KOH chemical activation. The effect of the impregnation KOH/carbonized cones ratio (IR = 1, 2, or 3) and temperature (873, 973, 1073 K) on main chemical, textural, and morphological characteristics of the resulting ACs was systematically examined. CO₂ adsorption capacity from gaseous streams was evaluated by gravimetric adsorption tests, and the analysis of breakthrough curves was determined in a packed-bed column at 303 K and atmospheric pressure. Comparison of CO₂ adsorption capacities of the ACs at 273 K and 303 K at equilibrium showed that those samples developed at 973 K with IR = 3 (BET surface area ~ 1900 m² g⁻¹) attained the highest values (6.4 mmol g⁻¹ and 1.9 mmol g⁻¹, respectively), even though the ACs obtained at 1073 K with the same IR exhibited the largest surface area (2200 m² g⁻¹). Thermodynamic parameters evaluated from CO₂ adsorption isotherms determined in the range 273–333 K for the former sample pointed to a physisorption, spontaneous, and exothermic process; isosteric heat of adsorption was also estimated for the range of surface coverage of the equilibrium isotherms. The kinetics of CO₂ adsorption onto all the ACs was successfully described by the linear driving force model. The breakthrough curves were properly represented by the Thomas’ model, the longest breakthrough time and highest adsorption capacity being also attained for the bed packed with the ACs developed at 973 K with IR = 3. Higher CO₂ adsorption capacities of the ACs were directly related to the presence of narrow micropores (< 0.9 nm) induced by the stronger activation conditions. However, an excessively severe combination of the IR and activation temperature exerted a negative influence on CO₂ adsorption onto the ACs, likely due to micropores widening.

Microplastics (MPs) are physical anthropogenic pollutants and their ability to act as contaminant vectors in biological matrices is of serious ecosystem and human health concern. In the present study, we have, for the first time, screened and detected MPs in the stomach of a select group of commonly consumed fish species from a municipal water supply lake (Eleyele) in Nigeria. A total of 109 fish samples consisting of eight (8) species: Coptodon zillii (CZ: n = 38), Oreochromis niloticus (ON: n = 43), Sarotheron melanotheron (SM: n = 19), Chrysicthys nigrodigitatus (CN: n = 3), Lates niloticus (LN: n = 3), Paranchanna obscura (PO: n = 1), Hemichromis fasiatus (HF: n = 1), and Hepsetus odoe (HO: n = 1) were collected between February–April, 2018. Fish stomach content was screened for the presence of MPs using the density gradient separation technique (NaCl hypersaline solution) and examined using a fluorescence microscope. MPs were present in all the species screened (except H. fasciatus) with a frequency of 69.7% positive individuals in the examined species. MP prevalence was highest in ON (34%) > CZ (32%) > SM (13%) > CN (6%) and 5% each, for PO HO, and LN. On average, 1–6 MPs with sizes ranging between 124 μm and 1.53 mm were detected per individual. However, the highest number (34) of MPs was detected in the stomach of SM. Principal coordinate analysis (PCA) identified ecological variables such as habitat, feeding mode, and trophic levels as critical factors that may determine and influence MP uptake in fish population. The PCA showed stronger association between fish habitat, feeding mode, and trophic level with MP size and number in the benthopelagic species (ON CZ and SM), compared to demersal species (PO CN HO and LN). Given that MPs can act as vectors for the transfer of pathogens and environmental contaminants (both legacy and emerging), in addition to direct health risks to aquatic organisms, our findings raise concerns on the potential human/wildlife health effects of MPs in these economically and ecologically important food fishes.

The particle deposition on the surface of solar photovoltaic panels deteriorates its performance as it obstructs the solar radiation reaching the solar cells. In addition to that, it may cause overheating of the panels, which further decreases the performance of the system. The dust deposition on the surfaces is a complex phenomenon which depends on a large number of different environmental and technical factors, such as location, weather parameters, pollution, tilt angle and surface roughness. Hence, it becomes crucial to investigate the key parameters which influence dust accumulation and their interrelations. In this study, the phenomenon of dust deposition was studied experimentally in the urban area at one of the most polluted cities of Europe, i.e. Kraków, Poland. Solar photovoltaic panels tilted at angles 15° and 35° were exposed to atmospheric conditions for the period of eighteen months from 6 May 2017 until 30 November 2018. Dust samples were collected from the panels for the exposure period which ranged from one day up to 11 days. It was observed that lower tilt angles promote dust accumulation on the surface and that in the absence of wind and rain, deposition of particles on the surface of panels follows the pattern of concentration of PM2.5 and PM10 in the atmosphere. Wind and rainfall usually promote the removal of dust particles from the surface. However, rainfall not always aids the cleaning of panels, and it was observed that low-intensity rain results in a very low rate of PMs in the air and in much higher than typical dust deposition on the panel surface. It also accelerates the cementing of already deposited dust. It was only rainfall whose intensity was at least 38 mm/h that was sufficient to remove dust particles from the panels.

To investigate the variation of the biogeochemical cycle of riverine dissolved inorganic carbon (DIC) and silicon (DSi) with the cascade damming, the bicarbonate ([Formula: see text]), dissolved silicon (DSi), and other environmental factors within the cascade reservoirs of the lower reaches of Yalongjiang River, passing through the southeastern Qinghai-Tibet Plateau, were systematically analyzed by collecting water samples during the wet season and dry season from 2018 to 2019, respectively. The results showed that the lower ratio of DSi to[Formula: see text] (0.044 ± 0.001) was mainly controlled by the domination of carbonate mineral in the sedimentary rock of the Yalongjiang River drainage basin. The DSi:[Formula: see text] ratio was positively correlated with discharge (P < 0.05), and negatively correlated with the water retention time (P < 0.01) and chlorophyll a, implying that the variations of DSi:[Formula: see text] ratio were mainly determined by the rock chemical weathering processes and the hydrologic process outside the reservoirs and the biological processes within the cascade reservoirs. The phytoplankton photosynthetic process stoichiometrically assimilated DSi and [Formula: see text], resulted in 3.46 × 10⁴ t·Si a⁻¹ and 1.89 × 10⁴ t·C a⁻¹ sequestering in the cascade reservoirs, respectively. Compared with the situation of dam-free in the lower reaches of Yalongjiang River, the export flux of [Formula: see text] and DSi at the mouth of Yalongjiang River was reduced by 11.87% and 62.50%, respectively; the ratio of DSi:[Formula: see text] decreased by 36.01% for only building the Ertan dam and 53.15% for the cascade damming, respectively. The water renewal time prolonged from 45 to 126.6 days due to the regulation of the cascade reservoirs in the mainstream. Ultimately, a conceptual model on migration-transformation of DIC and DSi within the cascade reservoirs in the lower reaches of Yalongjiang River was established. These findings demonstrated that riverine cascade damming could extend the biogeochemical coupling cycle of DIC and DSi within the inland aquatic ecosystems and ensure the ecological environment security in the hot-dry valley.

Diatomite is an economical and environmentally friendly adsorbent, and its use has been applied widely for the treatment of water contaminated by heavy metals. Despite this, the mechanism for the removal of the heavy metal Cd(II) remains unclear. In this work, we explored the adsorption mechanism of Cd(II) by diatomite using batch experiment, and characterized the diatomite using scanning electron microscopy, energy-dispersive spectrometry, specific surface area, and pore size distribution analysis. Our results showed that, under the experimental conditions, the kinetic adsorption approached equilibrium within 5 min, and the Sips isotherm model was most suitable for data fitting. EDS characterization of the Cd-loaded diatomite indicated that Cd(II) was adsorbed onto the diatomite. Furthermore, desorption experiments showed that Ca²⁺ and Mg²⁺ in the diatomite caused an ion exchange interaction, and this was primarily responsible for Cd(II) adsorption. Moreover, we found that its contribution to the whole adsorption reaction could reach 80%, while the remainder of Cd(II) was probably trapped in the microporous structure of the diatomite. Additionally, our data indicated that the adsorption mechanism did not change significantly after regeneration. These results have provided special insight into the deep understanding of the mechanism of Cd(II) adsorption by diatomite, and could provide theoretical support and guidance for further development and application of diatomite in the treatment of Cd(II)-contaminated water. Graphical abstract

This study investigates the transmission of volatility between OPEC-oil and sector stock returns in Pakistan. The issue of volatility spillovers across the oil and sector stocks is a crucial part of risk management and portfolio designs, as all firms are not expecting to be equally affected by changes in oil price. Empirically, we estimate a bivariate VAR-GARCH model using daily data sampled from January 1, 2003 to December 29, 2017. We also analyze the optimal weights and hedge ratios for oil-stock portfolio holdings based on our model results. Our findings reveal that negative and significant spillover effects from the oil market to agriculture, energy, and machinery sector stocks are present. However, our findings show that volatility spillover effects are insignificant from stock returns to oil. The findings of the study illustrate that development of stock market will motivate highly polluting firms to invest more in renewable and clean energy, which will help reduce carbon emissions.

Silver nanoparticles were fabricated in the presence and absence of light with silver nitrate and aqueous extract of Prunus cerasifera leaf via facile and one-pot green method. P. cerasifera leaf extract reduced and stabilized the nanoparticles with phytometabolites expunging the need for addition of external reducing agents. Optimized silver nanoparticle syntheses was done with variations in leaf extract concentration, time, temperature, and molarity for deciphering the photocatalytic, antifungal, and antibacterial potential of synthesized nanoparticles. Optical, compositional, and morphological analyses of the synthesized nanoparticles were done by UV-visible spectrometry (UV-Vis), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Formation of silver nanoparticles was confirmed firstly through UV-Vis by exhibition of peaks with 400–450 nm. FTIR confirmed the presence of major organic groups responsible for reduction of nanoparticles. AFM confirmed the spherical morphology of the synthesized nanoparticles with remarkable dispersion without any agglomeration. Phytochemical analysis for P. cerasifera leaf metabolites was done by GC-MS. Spherical nanoparticles having a size range of 57–144 nm were obtained with face-centered cubic crystals. The average crystallite size obtained from XRD spectra was 2.34 nm. Enhanced photocatalytic first-order kinetics were obtained for persistent organic pollutants, i.e., crystal violet, methylene blue, and malachite green (R² = 0.99, 0.99, 0.98) in less than 15 min. Biomedical and agricultural significance as an antibiotic drug and utilization as a fungicides substitute was explored against nine resistant microbes. Statistically significant variations were analyzed via one-way analysis of variance (ANOVA) and Kruskal-Wallis test and specific multi comparison tests. Active to highly active inhibition zones manifested the use of biogenic silver nanoparticles as potential candidate for applications in biological arenas and as environmental remediators.

This study uses a combined data envelopment analysis and logarithmic mean Divisia index (DEA-LMDI) method to decompose affecting factors for PM₂.₅ emissions into effects related to the potential emission intensity (PEI), environmental efficiency and technology, production efficiency and technology, regional economic structure, and national economic growth, and investigates differences in the effects on PM₂.₅ emissions, considering the diversity among different areas and periods in China. This study provides a new insight in the decomposition method, which can decompose the emissions into new effects compared with the exiting studies. This study reveals that the regional environmental-based technology (EBT) effect is the key curbing factor for PM₂.₅ emissions, followed by the regional PEI effect. The curbing effect of regional EBT on PM₂.₅ emissions is strong in East China and weak in Northeast China. The environment-oriented scale efficiency (ESE), environment-oriented management efficiency (EME), production-oriented scale efficiency (PSE), production-oriented management efficiency (PME), and production-based technology (PBT) had relatively small effects on PM₂.₅ emissions on the whole. The effects differ among different areas and periods in China. The emission reduction potential of these efficiency effects has not been realized. The national economic growth greatly promotes PM₂.₅ emissions. The regional economic structure effect slightly increases PM₂.₅ emissions because of the unbalanced development of regional economy. The relative policy suggestions are put forward based on the findings of this study.

This study examines the impacts of economic growth, energy consumption, tourism, and natural resources on the ecological footprint in the ASEAN countries for spanning from 1995 to 2016. For this purpose, the cross-sectional dependent test, the second-generation unit root test, and the Westerlund cointegration test have been applied. The Driscoll-Kraay panel regression model has been used to check the long-run relationship among the series. Also, the Dumitrescu-Hurlin panel causality test is used to determine the paths of causal interactions. These tests help to overcome the problem of cross-sectional dependence in panel data analysis. The results showed an inverted U-shaped EKC behavior in ASEAN countries, hence a negative relation between tourism and natural resources with the ecological footprint. This implies that tourism and natural resources help to improve the environmental quality in ASEAN countries.