Zn Ratio Research Articles

Remobilization characteristics and diffusion kinetic processes of sediment zinc (Zn) in a tidal reach of the Pearl River Estuary, South China

Exploration of the remobilization mechanism of trace metals in estuarine sediments remain challenging because of dynamic hydrochemical conditions. This study integrated a chemical sequential extraction procedure (BCR), the diffusive gradient in thin films (DGT) and high-resolution dialysis techniques, and Visual MINTEQ ver.3.1 to identify the seasonal mobilization characteristics of sediment Zn within a tidal reach, South China. The mobility of sediment Zn based on the BCR procedure contradicted the results of DGT analysis. In summer, reductive dissolution of Fe/Mn oxides was the key driver of sediment Zn remobilization; during winter, cation exchange reactions facilitated the mobilization of Zn in the brackish water zone. The time-dependence ratios of DGT-labile Zn and dissolved Zn concentrations (mean: 0.34–0.81) indicated the sediment solid phase had partially sustained capacity to resupply Zn to the porewater in both seasons. Sediments generally functioned as a source of Zn in the freshwater zone with organically complexed Zn being diffusively released into the water column at rates of 0.3–15.5 μg·m−2·d−1. In the brackish water zone, the dominant Zn species were transformed into free Zn ions and Zn–inorganic complexes and migrated into sediment, with respective influxes of 18.9–70.7 μg·m−2·d−1 and 18.9–68.3 μg·m−2·d−1, which shifted to a sink of Zn.

Simultaneously enhanced aromatics selectivity and catalyst lifetime in methanol aromatization over [Zn, Al]-ZSM-5 via isomorphous substitution with optimized acidic properties and pore structure

Zinc-modified HZSM-5 zeolites as efficient catalysts have been widely applied in methanol to aromatics (MTA) reactions, however, the relationship between aromatics selectivity and catalytic stability in traditionally loaded catalysts seems to be a stubborn trade-off. To improve both catalytic indicators simultaneously and reveal the relation of the states of introduced Zn species to the consequential influence in physiochemical properties, a series of [Zn, Al]-Z5 zeolites with different Zn contents were prepared via isomorphous substitution under a fixed Si/Me (Me = Al or Al and Zn) ratio. Results revealed that there were three possible states of the introduced Zn species, namely the highly-dispersed ZnO phase, the Zn(OH)+ occupying the ion-exchange sites, and the tetra-coordinated ZnO42- integrated into the zeolite framework. A portion of Zn was successfully integrated into the five-membered rings of zeolite in the form of Si-O(H)-Zn, which played the role of strong Brönsted acid sites and led to the formation of hierarchical structures aside from the intrinsic micropores. Besides, extra-framework Zn(OH)+ was formed by the interaction between dissociate Zn species and the Si-O(H)-Al structure, giving rise to larger proportions of Lewis acid sites. Benefitting from the optimized acidic properties and pore structure, 0.5[Zn, Al]-Z5 exhibited higher aromatics selectivity and longer catalyst lifetime (26.0% and 132 h) than [Al]-Z5 without Zn addition (19.6% and 52 h) in methanol aromatization. Overall, our findings opened a new way to improve the efficiency of MTA reaction and broadened the method to obtain metal-modified zeolite catalysts.

INTENSITY OF ACCUMULATION OF HEAVY METALS IN RADISH AND LETTUCE GROWN IN CLOSED SOILS IN THE CONDITIONS OF THE FOREST STEPPE OF THE RIGHT BANK

One of the important tasks in vegetable production is the expansion of the range of vegetable crops in open and closed soil, which will ensure a constant supply of fresh vegetable products to consumers throughout the year. Lettuce and radish are among the many green vegetables that play an important role in solving this problem. In this work, the intensity of accumulation of heavy metals (Pb, Cd, Zn, Cu) in lettuce of the Record variety and radish of the Saxony variety in closed and open conditions of dark gray podzolized soil was studied. It was established that the concentration of Pb, Cd, and Zn in seeded lettuce grown under closed soil conditions was 1.5 times, 1.8 and 1.12 times lower, respectively, and in seeded radish by 1.5 times, 1.05 and 1, 23 times compared to similar products grown in open ground conditions. When growing lettuce and radish in closed soil conditions, the accumulation coefficient of Pb, Cd, Zn was lower by 2.0 times and 2.0 times, 1.8 times and 1.6 times, and 1.2 times and 1.2 times, respectively compared to similar products grown in open ground conditions. The coefficient of accumulation of Pb, Cd, Zn in lettuce grown in open ground was 2.0, 1.8, 1.12 times higher than that of lettuce grown in closed ground, respectively, and the coefficient of Pb accumulation in radish roots grown in open ground was 2.0 times higher than in the closed one, Cd concentration 1.6 times, Zn 1.2 times, and Cu 1.2 times, respectively. The research results showed that the hazard ratio of Pb in lettuce leaves and radish roots when grown in open ground was 1.5 times higher compared to similar vegetables grown in closed ground, the hazard ratio of Cd and Zn in lettuce leaves and radish roots grown under conditions of open soil was 1.8 and 1.06 times higher, respectively, compared to vegetables grown in closed soil, the hazard ratio of Cu in lettuce that was grown under closed soil conditions was 0.7 times higher compared to that grown in open soil. In radish roots, the risk factor of Cu was 1.5 times higher than in vegetables grown under open soil conditions.

THE INFLUENCE OF THE LEVEL OF SOIL MOISTURE ON THE TRANSLOCATION OF Zn AND Cu IN GRAIN OF WINTER CEREALS IN THE CONDITIONS OF THE FOREST STEPPE OF THE RIGHT BANK

The attention of almost the entire world community is focused on the problem of food security. In many countries of the world, the lack of food resources is acutely felt, the main source of which is grain farming. Ukraine is distinguished among other countries by its favorable soil and climatic conditions for the cultivation of cereals, it has the appropriate technologies, and qualified workers. Therefore, the production of grain products is one of the main directions of the agro-industrial complex of Ukraine, which is subject to certain quality requirements. The article examines the influence of the level of soil moisture (precipitation and irrigation) on the content and coefficient of accumulation and danger of Zn and Cu in the grain of winter wheat and winter barley. The purpose of the study is to study the influence of the level of soil moisture (precipitation and irrigation) on the content of the coefficient of accumulation and danger of Zn and Cu in the grain of winter wheat and winter barley in the conditions of the right-bank forest-steppe. An increase in the coefficient of accumulation of Zn and a decrease in the coefficient of accumulation of Cu in cereal grains contributed to an increase in the concentration of Zn and a decrease in Cu under such conditions, this feature was established both in winter barley of the variety (Luran) and in winter wheat of the variety (Akratos). In particular, at the level of soil irrigation in the period of tillering-earing of winter barley and winter wheat from 256.2 mm to 272.5 mm, the concentration of Zn in the grain of these cereals was 1.07 times higher, and the concentration of Cu was 1.05 times lower in winter barley grain, and in winter wheat grain, the concentration of Zn was 1.14 times higher and 1.15 times lower than the concentration of Cu, respectively, compared to the moisture level of 47.4 mm and 52.3 mm. The coefficient of danger of heavy metals in the grain of winter cereals at the level of soil moisture from 256.2 mm. to 272.5 mm in the tillering-earing period was higher in Zn and lower in Cu compared to the moisture level of 47.4 mm–52.3 mm. An increase in the hazard ratio of Zn by 1.06 times and a decrease in the hazard ratio of Cu by 1.15 times in winter barley grains and an increase by 1.15 and a decrease by 1.16 times in winter wheat grains, respectively. During the artificial moistening of the soil during the growing season in the period of tillering-earing until the grain is milky, an increase in these Zn indicators and a decrease in Cu were observed in both winter barley and winter wheat grains.

Metallothionein-3: 63 Cu(I) binds to human 68 Zn7 -βα MT3 with no preference for Cu4 -β cluster formation.

Human metallothioneins (MTs) are involved in binding the essential elements, Cu(I) and Zn(II), and the toxic element, Cd(II), in metal-thiolate clusters using 20 reduced cysteines. The brain-specific MT3 binds a mixture of Cu(I) and Zn(II) in vivo. Its metallation properties are critically important because of potential connections between Cu, Zn and neurodegenerative diseases. We report that the use of isotopically pure 63 Cu(I) and 68 Zn(II) greatly enhances the element resolution in the ESI-mass spectral data revealing species with differing Cu:Zn ratios but the same total number of metals. Room temperature phosphorescence and circular dichroism spectral data measured in parallel with ESI-mass spectral data identified the presence of specific Cu(I)-thiolate clusters in the presence of Zn(II). A series of Cu(I)-thiolate clusters form following Cu(I) addition to apo MT3: the two main clusters that form are a Cu6 cluster in the β domain followed by a Cu4 cluster in the α domain. 63 Cu(I) addition to 68 Zn7 -MT3 results in multiple species, including clustered Cu5 Zn5 -MT3 and Cu9 Zn3 -MT3. We assign the domain location of the metals for Cu5 Zn5 -MT3 as a Cu5 Zn1 -β cluster and a Zn4 -α cluster and for Cu9 Zn3 -MT3 as a Cu6 -β cluster and a Cu3 Zn3 -α cluster. While many reports of the average MT3 metal content exist, determining the exact Cu,Zn stoichiometry has proven very difficult even with native ESI-MS. The work in this paper solves the ambiguity introduced by the overlap of the naturally abundant Cu(I) and Zn(II) isotopes. Contrary to other reports, there is no indication of a major fraction of Cu4 -β-Znn -α-MT3 forming.

Facile synthesis of ZIF-8-lignosulfonate microspheres with ultra-high adsorption capacity for Congo red and tetracycline removal from water

Zeolitic imidazolate frameworks (ZIFs) can be used as adsorbent to efficiently adsorb organic pollutants. However, the hydrophobicity of the ZIFs may be easily to form ZIFs nanoparticles aggregates, hampering the effective and practical application in adsorption. In this study, novel spherical composites of ZIF-8 incorporated with lignosulfonate (LS) were synthesized by in-situ growth method. The effects of different mass ratios of LS and Zn in ZIF-8-LS composites were evaluated with respect to structural characteristics and adsorption properties. As an adsorbent for adsorptive removing Congo Red (CR) and tetracycline (TC) from water, the prepared ZIF-8-LS4 shows the best adsorption capacity of 31.5 mg g−1 and 48 mg g−1, respectively. The spherical structure facilitates the contact between the ZIF-8 and the adsorbed substance, in addition to the H-bonding, electrostatic and π–π stacking interactions also contribute to the improvement of the adsorption performance of the ZIF-8-LS4 composite. The outstanding adsorption capacity and good reusability of the ZIF-8-LS4 composite provide a good prospect for the effective removal of other contaminants from water.

Does Water Play a Crucial Role in the Growth of ZnO Nanoclusters in ZnO/Cu Catalyst?

The catalytically active configuration of ZnO/Cu in the commercial ZnO/Cu/Al2O3 catalyst for methanol synthesis from CO2 is still not clear. In this study, we employ density functional theory based methods to shed light on the structure and stoichiometry of ZnO clusters both free in the gas phase and also deposited on the Cu(111) surface under methanol synthesis conditions. Specifically, we investigate the structural evolution of ZnO clusters in the presence of hydrogen and water. We find that the stability of ZnO clusters increases with the concentration of water until the ratio of Zn and OH in the clusters reaches 1:2, with a morphological transition from planar to 3D configurations for clusters containing more than 4 Zn atoms. These clusters exhibit weak interaction with CO2, and water is predicted to block the active center. The Cu(111) surface plays an important role in enhancing the adsorption of CO2 on the ZnO/Cu(111) systems. We infer that ZnO nanostructures covered with OH species may be the morphology of the ZnO during the methanol synthesis from the hydrogenation of CO2 on the industrial catalyst.

Rapid fabrication of nanoporous iron by atmospheric plasma for efficient wastewater treatment

Nanoporous (NP) iron with large surface area is highly desired for wastewater degradation catalysis. However, it remains a challenge for the fabrication of NP-Fe because the conventional aqueous dealloying or liquid metal dealloying are not applicable. Herein, a novel and universal plasma-assisted electro-dealloying technique was utilized to fabricate NP-Fe. The NP-Fe demonstrates evenly distributed pore structure. The pore density can be tuned by the variation of the ratio of Fe and Zn in the precursor, and the average pore size can be tuned by the processing time. Owing to its large specific surface area, the NP-Fe shows excellent wastewater degradation performance, which is 26 times better than that of commercial zero-valent iron catalysts. This study provides a useful approach to fabricate NP active metals with enhanced catalytic performance.

Bimetallic (Fe/Zn-ZIF-8) crystals: Fabrication and adsorptive removal activity

This work presents an investigation on the fabrication and characterization of Fe doped zeolitic imidazolate framework (ZIF-8) of 1:1 M ratio of Zn:Fe (Fe/Zn-ZIF-8) and adsorption performances of acquired materials. The synthesized Zn-ZIF-8, Fe-ZIF-8, and Fe/Zn-ZIF-8 materials were characterized for the phase structure, morphology, elemental analysis and surface area by using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), Energy Dispersive X-Ray (EDX), and BET surface area, respectively. The results revealed the adsorption capacity was enhanced by incorporation of Fe into ZIF-8 structure. The CR dye adsorption capacities were 287, 219, and 412 mg/g for Zn-ZIF-8, Fe-ZIF-8, and Fe/Zn-ZIF-8 adsorbers, respectively. The CR adsorption obeyed to the pseudo 2nd order model and the Langmuir model was most closely matched during the high value of correlation coefficient (R2), signifying a palpable monolayer adsorption rather than multilayer.

Effect of ZnO dimers on the thermoelectric performance of armchair graphene nanoribbons.

Enhancing the thermoelectric performance in engineered graphene nanoribbons is used to produce thermoelectric nanodevices, which are important in many applications. By using a chemical doping method, armchair graphene nanoribbons (AGNRs) can have thermoelectric properties that are tunable. We predicted that changing the number and geometrical pattern of zinc oxide (ZnO) dimers in an AGNR can engineer thermoelectric properties, so we used density functional-based tight binding (DFTB) combined with the non-equilibrium Green's function (NEGF) to investigate the geometric, electronic, and thermoelectric properties of the AGNR with and without various dopants of ZnO dimers. With three forms of ZnO dimers, ortho, meta, and para dimers, different concentration ratios of Zn and O atoms are used. Our results indicate that the electronic features of AGNR are influenced not only by the concentrations of ZnO dimers but also by the geometrical pattern of ZnO dimers in the AGNR. These results are helpful in better understanding the effect of chemical doping on the transport properties of AGNRs and in motivating nanodevices to improve their thermoelectric performance.

Spatial and temporal trends in δ66Zn and 206Pb/207Pb isotope ratios along a rural transect downwind from the Upper Silesian industrial area: Role of legacy vs. present-day pollution

Transect sampling is an under-exploited tool in isotope studies of atmospheric pollution. Few studies have combined Zn and Pb isotope ratios to investigate whether atmospheric pollution at a receptor site is dominated by a different anthropogenic source of each of these toxic elements. It has been also unclear whether pollution abatement strategies in Central Europe have already resulted in regionally well-mixed background isotope signature of atmospheric Zn and Pb. Zinc and lead isotope ratios were determined in snow collected along a rural transect downwind from the Upper Silesian industrial area (southern Poland). Spatial and temporal gradients in δ66Zn and 206Pb/207Pb ratios at four sites were compared with those of ore and coal collected in eight Czech and Polish mining districts situated at distances of up to 500 km. Snow pollution was extremely high 8 km from Olkusz in 2011 (1670 μg Zn L−1; 240 μg Pb L−1), sharply decreased between 2011 and 2018, and remained low in 2019–2021. Snow pollution was lower at sites situated 28–68 km from Olkusz. Across study sites, mean δ66Zn and 206Pb/207Pb ratios of snow were −0.13‰ and 1.155, respectively. With an increasing distance from Olkusz, the δ66Zn values first increased and then decreased, while the 206Pb/207Pb ratios first decreased and then increased. The δ66Zn values in snow plotted closer to those of Upper Silesian ores (−0.20‰) than to the δ66Zn values of Upper Silesian stone coal (0.52‰), showing predominance of smelter-derived over power-plant derived Zn pollution. The 206Pb/207Pb ratios of Upper Silesian coal (1.171) and Upper Silesian ores (1.180) were higher compared to those of snow. A206Pb/207Pb vs.208Pb/207Pb plot identified legacy pollution from leaded gasoline as the low-radiogenic mixing end-member. Across the transect sites, only the last sampling campaign exhibited a high degree of isotope homogenization for both Zn and Pb.

Comprehensive study of recycling municipal solid waste incineration fly ash in lightweight aggregate with bloating agent: Effects of water washing and bloating mechanism

Recycling into lightweight aggregate (LWA) by sintering is a promising technology for disposal of municipal solid waste incineration fly ash (FA). In this study, FA and washed FA (WFA) were combined with bentonite and SiC (bloating agent) to make LWA. The performance was comprehensively studied by hot-stage microscopy and laboratory preparation experiments. Water washing and increased FA/WFA improved LWA bloating extent, while shorten the bloating temperature range. Water washing also increased the 1 h-water absorption rate of LWA, making it harder to meet the standard. Excessive FA /WFA usage (70 wt%) will prevent LWA from bloating. For the goal of recycling more FA, mixture with 50 wt% WFA could prepare LWA that meet standard GB/T 17431 at 1140–1160 °C. After water washing, the ratio of Pb, Cd, Zn, and Cu stabilized in LWA increased by 279 %, 410 %, 458 %, and 109 % for 30 wt% FA/WFA addition, and 364 %, 554 %, 717 %, and 697 % for 50 wt% FA/WFA addition, respectively. The change of liquid phase content and viscosity at high temperature were determined using the thermodynamic calculations and chemical compositions. The bloating mechanism was further investigated by integrating these two properties. To obtain accurate results of the bloat viscosity range (2.75–4.44 log Pa·s) for high CaO systems, the composition of the liquid phase should be taken into account. The liquid phase viscosity required for bloating start was proportional to the liquid phase content. With temperature increasing, bloating would end when viscosity drops to 2.75 log Pa·s or liquid phase content reach 95 %. These findings provided further understanding of the heavy metal stabilization during LWA production and the bloating mechanism of high CaO content systems, and could contribute to the feasibility and sustainability of recycling FA and other CaO-rich solid wastes into LWA.

Local electron-rich structures facilitating the efficient synthesis of dimethyl carbonate from propylene carbonate and methanol over a ZnO/ZrO2 solid solution catalyst

ZnO/ZrO2 solid solution was introduced as the catalyst for synthesizing dimethyl carbonate (DMC) from propylene carbonate (PC) and methanol. Homogeneous catalysts with strong alkaline nature are the current main catalysts for this reaction. Therefore, to supplant the former with a more applicable multiphase one, it is necessary to construct stable and efficient alkaline active centers on the surface of solid catalysts. The ZnO/ZrO2 solid solution created defective structures of coordinative unsaturation in the form of oxygen vacancies (OV) by substituting Zn atoms for Zr atoms in ZrO2 crystals. Characterizations showed that electrons were transferred to the surrounding Zn atoms upon the formation of these OV, leading to a local enrichment of electrons and the formation of basic active centers. The number of oxygen defects and the alkalinity were effectively regulated by changing the ratio of the two metal atoms in the solid solution. Experiments demonstrated that the catalyst had the best DMC selectivity (92.2%) and the highest DMC yield (57.2%) at a 1:1 ratio of Zn to Zr, at 160 °C and 4 h. This superior performance not only establishes the feasibility of solid solution catalysts in synthesizing DMC but also provides a new perspective on the essential understanding of the active centers of such catalysts.

Effect of Dietary Supplementation of Zinc Nanoparticles Prepared by Different Green Methods on Egg Production, Egg Quality, Bone Mineralization, and Antioxidant Capacity in Caged Layers.

The present study was planned to evaluate the effect of dietary zinc-oxide (ZnO) nanoparticles synthesized by different plant extracts on egg production, egg quality, bone mineralization, and antioxidant capacity in caged layers. Nanoparticles of ZnO were synthesized by using extracts of Allium sativum (AS), Aloe vera (AV), Curcuma longa (CL), and Zingiber officinale (ZO). Different sources of nano ZnO (AS, AV, CL, and ZO) with varying levels (35, 70, or 105 ppm) were tested on 288 caged LSL layers of 25 weeks of age. Each diet was offered to 4 replicates of 6 birds each level and the duration of trial was 8 weeks. Daily egg production, feed consumption, and fortnightly egg quality parameters were recorded. Egg quality parameters (egg weight, egg mass, shape index, yolk index, albumen index, Haugh unit score, specific gravity, and eggshell thickness) were determined fortnightly by taking 2 eggs from each replicate randomly. Antioxidant capacity and bone mineralization were determined at the end of the trial. Results showed that the nano ZnO preparations were not effective (P < 0.05) on laying performance but additional levels (70 ppm) improved egg production, feed conversion ratio, egg mass, Haugh unit score, and antioxidant capacity of chickens. An interaction was found among nanoparticles prepared by Allium sativum and Zingiber officianale extracts with 70 ppm level regarding total antioxidant capacity and egg production (P > 0.05). Interaction among source and level was not found regarding feed intake, feed conversion ratio, egg quality, bone characteristics, and concentration of Zn. Results of the present study suggest that nano ZnO sources may not be a factor that affects performance, but level affects the birds' physiology. Thus, it is concluded that nano ZnO with 70 ppm concentration is sufficient to optimize the laying performance.

Zinc and Strontium-Substituted Bioactive Glass Nanoparticle/Alginate Composites Scaffold for Bone Regeneration.

The global population is growing older and entering an aging society. Aging results in severe tissue disorder and organ dysfunction. Bone-related injuries are particularly significant. The need for alternative bone replacement materials for human implants has grown over the past few decades. Alginate has the potential for use as a cell scaffold for bone tissue engineering due to its high bio-compatibility. To improve the bioactivity of alginate scaffolds, zinc- and strontium-containing sol-gel-derived bioactive glass nanoparticles (Zn-Sr-BGNPs) with sizes ranging from 100 to l40 nm were incorporated. Zn-Sr-BGNPs synthesized through the sol-gel process have a high sur-face-to-volume ratio, homogeneity, and purity, resulting in faster degradation. The therapeutic bivalent ions released from Zn-Sr-BGNPs strengthen the cell scaffold and improve the stimulation of the production and development of bone cells. Zn-Sr-BGNPs with different Zn to Si nominal ratios of 0, 1, and 1.5 were mixed with alginate in this research. The ratio of Zn in Zn-Sr-BGNPs and the ratio of Zn-Sr-BGNPs in scaffolds impact the pore size, swelling, and biological properties of synthesized composite scaffolds. The surface area and pore volume of a 1:1 1Zn-Sr-BGNP:Alg composite scaffold were 22.58 m2/g and 0.055 cm3/g, respectively. The incorporation of Zn-Sr-BGNPs improved the mechanical performance of the scaffolds up to 4.73 ± 0.48 MPa. The swelling rate decreased slightly from 2.12 (pure Alg) to 1.50 (1Zn-Sr-BGNP:Alg (1:1)). The 1Zn-Sr-BGNP:Alg (1:1) composite scaffold promoted bioactivity through apatite layer formation, increased bone cell proliferation via the dissolution products released from the scaffold, enhanced calcium deposition, and facilitated cell attachment. Thus, 1Zn-Sr-BGNP:Alg (1:1) composite scaffold is proposed as a possible artificial bone scaffold in bone tissue regeneration.

Synergistic performance of Zn2+ incorporated bimetallic Cobalt sulfide for the hydrogen evolution reaction in an alkaline medium

Cobalt sulfide (CoS) has gathered attention as a hydrogen evolution reaction (HER) catalyst. However, further research is required to enhance the catalytic performance CoS in terms of its durability, electrocatalytic activity and understanding its fundamental mechanism. Herein, we report a facile hydrothermal synthesis of Zn-substituted CoS with excellent electrocatalytic activity and stability towards the HER. Zn substitution in CoS has been carried out using different ratios of Zn. As a result, the synergistically doped ZnCoS-1 achieved an overpotential of 227 mV for the HER in order to achieve a current density of 10 mA cm−2 in 1 M KOH electrolyte. The performance enhancement observed with ZnCoS-1 is attributed to the Zn2+ dopant, which forms a bimetallic phase with CoS and acts as a strong Lewis acid that regulates the electronic characteristics for enhanced intermedial binding for catalytic activity. The prepared ZnCoS-1 catalyst exhibits excellent catalytic activity and robust stability towards the HER demonstrating the potential possibility to construct a water electrolyzer for sustainable hydrogen production.

Characterisation and larvicidal effects of different zinc oxide nanoparticles against Aedes aegypti larvae

This work reports the characterisation and larvicidal effects of two ZnO nanoparticle types towards Aedes aegypti (Ae. aegypti) larvae. ZnO-AG (as-grown ZnO produced by gas-phase synthesis) and ZnO-BM (ball-milled for one week) were the two types of ZnO nanoparticles. ZnO-AG and ZnO-BM were characterised for structural, optical, and morphology properties by XRD, UV–vis, and FESEM, respectively. The colloidal nanoparticles were centrifuged and dried for the ZnO-BM sample before the bioassay procedure was performed on the third instar Ae. aegypti larvae. Bioassay procedures were done following WHO standards for both samples. The results revealed that ZnO-BM had a smaller crystallite size (34.88 nm) and higher EDX O: Zn ratio (0.831) compared to that of ZnO-AG (crystallite size 47.4 nm and 0.675 of O: Zn EDX ratio). Moreover, bioassay results showed ZnO-BM has lower LC50 (48.6 mg/L) compared to ZnO-AG (73.47 mg/L), which suggested the stronger toxicity of the ball-milled sample toward Ae. aegypti larvae. The higher mortality rate of the ZnO-BM sample can be attributed to its larger surface area-to-volume ratio that led to enhanced ROS (reactive oxygen species) generation and increased zinc dissolution that caused internal organ damage inside the Aedes larvae.

Synergetic metal-Nx and metal nanoparticles derived from Zn/Co-zeolitic imidazolate frameworks boosted conversion of microalgal lipids

In order to enhance acid-base active sites and their utilization efficiency to efficiently convert microalgal lipids into biodiesel, an acid-base catalyst was synthesized through pyrolyzing ZnCo bimetallic zeolitic imidazolate frameworks (ZIFs). Pyrolysis destroyed saturated coordinated metal-N4 sites in ZIFs and produced more unsaturated metal-Nx and metal nanoparticles, which enhanced Lewis acidity. The increased pyridinic N and unsaturated metal-Nx promoted Lewis basicity. Meanwhile, Zn doping reduced sizes of catalyst crystals and metal nanoparticles, which improved utilization efficiency of active sites. Hence, compared with pyrolyzed ZIF-67, the acidity of optimal catalyst increased from 0.205 to 1.535 mmol/g, whereas basicity increased from 0.069 to 0.405 mmol/g. DFT calculations revealed that catalytic performances of metal nanoparticles and unsaturated metal-Nx were better than that of saturated metal-N4. Therefore, the catalytic efficiency of C-Zn/Co-ZIF = 4 (molar ratio of Zn to Co was 4) catalyst was highest at 96.2%, because of the minimal catalyst crystals and metal nanoparticles.

Constructing an S-scheme heterojunction of 2D/2D Cd0.5Zn0.5S/CuInS2 nanosheet with vacancies for photocatalytic hydrogen generation under visible light

Exploring efficient and stable water-splitting photocatalysts is critical for realizing conversion solar energy into hydrogen energy. Herein, a unique 2D/2D S-scheme Cd0.5Zn0.5S/CuInS2 heterojunction with sulfur vacancies was rationally designed by chemically converting inorganic–organic hybrid ZnS(en)0.5 into inorganic Cd0.5Zn0.5S nanosheets and fabricating with CuInS2 at 350 °C under an N2 atmosphere. The final Cd0.5Zn0.5S/CuInS2 photocatalyst was composed of thin nanosheets with a substantial interfacial contact area, which enhanced light absorption and allowed directional charge transfer and separation. Under visible light irradiation, the photocatalytic H2 evolution activities of Cd0.5Zn0.5S nanosheets is 0.79 mmol·g−1·h−1, which is greater than other solid solution materials obtained by varying Cd and Zn ratios. The 2D/2D nanosheets with 8% CuInS2 exhibit excellent hydrogen evolution activity with yields of 7.73 mmol·g−1·h−1, which are 9.8 and 138 times higher than Cd0.5Zn0.5S and CuInS2. In addition, Cd0.5Zn0.5S/CuInS2 photocatalyst demonstrates outstanding stability and activity over the course of 24-hour period. Moreover, the transfer pathway of photogenerated charges were explored by the energy band bending, which proved that an S-scheme heterojunction is synthesized successfully.This work offers a useful methodology for analyzing S-scheme heterojunction with abundant sulfur vacancies, and improving the solar hydrogen evolution performance of Cd0.5Zn0.5S photocatalyst.

Potential of montmorillonite and humus-like substances modified montmorillonite for remediation of Pb and Zn-contaminated soils

Pb and Zn pollution for soil are becoming more and more serious, strengthening the treatment of contaminated soils is conducive to the sustainable development of soil. In this study, the humus-like substances modified montmorillonite (HLS-MMT) were synthesized to remediate the Pb and Zn-contaminated soils. The application of HLS-MMT in simulated and actual contaminated soil were carried, and the long-term stability of HLS-MMT was evaluated. The results showed that the mobility, bioavailability and leachability of heavy metals (HMs) significantly decreased after remediating by HLS-MMT. Compared with MMT, the TCLP leaching ratio (TLr) of Pb and Zn reduced by 9.27–13.96% and 10.3–13.18%, while the DTPA effectiveness (DEr) Pb and Zn reduced by 9.11% and 8.76% in simulated soil, respectively. Moreover, the aging experiments proved that HLS-MMT possessed a stability to resistance the freeze-thaw cycles, wet and dry alternation, and acid rain leaching. This article provides some theoretical basis for the soil remediation.