Cd Zn Research Articles

Effect of the Introduction of ZnII and CdII Ions on EuIII and TbIII Emission in M2Ln2 Heterometallic Molecules With 2‐Furoic Acid Anions

ABSTRACTHeterometallic d‐4f coordination complexes are of paramount interest in modern coordination chemistry because of their potential applications in organic light‐emitting devices and spintronic materials. Here we report the synthesis and thorough investigation of Ln and MLn (M = Zn, Cd; Ln = Sm, Eu, Gd, Tb) molecular complexes based on 2‐furancarboxylic acid anion (Hfur): [Ln2(NO3)2(fur)4(DME)2] (Ln = Eu, Gd, Tb; DME is dimethoxyethane) and [M2Ln2(NO3)2(fur)8(bpy)2] (M = Zn, Cd; Ln = Eu, Gd, Tb, Sm; bpy is 2,2′‐bipyridyl). The structure and isostructural nature of compounds were determined based on the single‐crystal and powder X‐ray diffraction data. The photophysical properties of the obtained compounds were studied in detail: The energies of the triplet levels of the furoate anion and d‐blocks {M(fur)2(bpy)} (M = Zn, Cd), the relaxation times of the excited states, and the quantum yields were determined. Critical step from Ln complexes to ZnLn and CdLn (Ln = Eu, Tb) is accompanied by an increase in quantum yields, which correlates with a change in the energy of the triplet level of the aromatic part of the complexes and with the results of quantum chemical calculations indicating different schemes for the origination of triplet levels in MLn compounds.

High-strength WC-Co/Low carbon steel connected by Ni–Cr–Fe alloy through brazing for roller sleeves

Enhancing the bond strength between WC-Co and steel is crucial for broadening its applications. In this study, WC-Co was bonded to low-carbon steel (LCS) using a Ni–Fe–Cr alloy at 1180 °C in an argon atmosphere furnace. The WC-Co/LCS (WL) interface was characterized by XRD, SEM, and EPMA, revealing no cracks or pores and confirming robust metallurgical bonding. The bonded material's shear strength reached approximately 321–328 MPa, significantly exceeding that achieved with Ag–Cu–Zn–Cd, Cu–Zn, Cu–Ni–Al, Ag–Cu–Zn + Ni/Mn, and Ag–Cu–In–Ti filler materials in the welding process. EPMA analysis showed that Fe, Cr, and Ni from the Ni–Fe–Cr alloy diffused into the WC-Co over distances of approximately 802–815 μm, 803–817 μm, and 632–641 μm, respectively. Initially, WC decomposed at sharp corners to form W₂C, which subsequently reacted with Fe and Cr to form M₆C and M₇C₃. This methodology was also applied to producing roller sleeves for vertical mills, increasing their lifespan by 1.9 times.

Hidden deposit exploration using the tectono-geochemistry method in the western Xicheng ore field, China

Geochemical anomalies involve complex geological and geochemical processes. Integrating metallogenic processes into the interpretation of geochemical data can promote mineral exploration. In this study, 3080 subsamples were collected from the western Xicheng ore field and combined into 1312 composite samples using the tectono-geochemistry method. Nineteen elements were analyzed for each composite sample. Factor analysis based on the CLR-transformed data yielded four factors, including the Ag–Sb–Hg–Pb–Au–(B–Ba) association of F1, Zn–Cd–Pb association of F2, Bi–Sn–(Au–As) association of F3, and W–Sn–(Cu) association of F4. Thresholds of each factor were obtained using the concentration–number (C–N) fractal model. Six targets were delineated based on the factor anomaly maps, and one Pb–Zn and two Au deposits were discovered in Targets I and II, respectively. These discoveries and the good spatial correspondence between known deposits and anomalies provide compelling evidence for the effectiveness of the tectono-geochemistry method in the study area. More importantly, a model for the genetic relationship between geochemical anomalies and metallogenesis was constructed. The late tectonic-magmatic-hydrothermal transformation dominated the geochemical pattern in the study area. The degree of interaction between the Au-rich magmatic-hydrothermal fluids and SEDEX-style Pb–Zn mineralizations yielded leakage halos with various elemental assemblages. In addition, W–Sn anomalies may serve as auxiliary exploration indicators for Au mineralizations.

Spatial patterns and mechanism of the impact of soil salinity on potentially toxic elements in coastal areas

Soil salinization and heavy metal pollution in the Yellow River Delta region have elicited increasing concern. Therefore, revealing the underlying mechanism of the impact of soil salinity on potential toxic elements (PTEs) is crucial for environmental protection and the rational utilization of resources in this area. In this study, we employed CatBoost–SHAP and multiscale geographically weighted regression (MGWR) models to comprehensively investigate the spatial effects of soil electrical conductivity (EC1:5) on PTEs. Additionally, we employed a space–for–time substitution strategy with the aim of investigating how increasing soil salinity, represented by EC1:5, K+, Na+, Ca2+, and Mg2+, affects the bioavailability of PTEs over time. The primary findings are as follows: (1) for most PTEs, the influence of soil EC1:5 on the bioavailable forms of these elements surpassed its impact on their total concentrations. (2) The results of the MGWR model indicated that exchangeable Ca (aCa) in the soils of the eastern coastal areas markedly increased the bioavailable Cd (aCd), bioavailable Cu (aCu), and bioavailable Zn (aZn). (3) When the soil EC1:5 ranges between 2 and 6 dS/m, exchangeable Na (aNa) primarily competed for the adsorption sites of bioavailable Pb (aPb). However, as the soil EC1:5 increases to 6–10 dS/m, exchangeable Mg (aMg) and aCa became the primary competing ions, with aMg playing a more significant role than aCa. These findings provide valuable theoretical insights and practical guidance for saline-alkali soil improvement and PTEs pollution control in the Yellow River Delta region, thereby providing a foundation for sustainable environmental management and resource utilization.

Enhancing zinc biofortification and mitigating cadmium toxicity in soil–earthworm–spinach systems using different zinc sources

Cadmium (Cd) pollution poses significant threats to soil organisms and human health by contaminating the food chain. This study aimed to assess the impact of various concentrations (50, 250, and 500 mg·kg–1) of zinc oxide nanoparticles (ZnO NPs), bulk ZnO, and ZnSO4 on morphological changes and toxic effects of Cd in the presence of earthworms and spinach. The results showed that Zn application markedly improved spinach growth parameters (such as fresh weight, plant height, root length, and root-specific surface area) and root morphology while significantly reducing Cd concentration and Cd bioconcentration factors (BCF-Cd) in spinach and earthworms, with ZnO NPs exhibiting the most pronounced effects. Earthworm, spinach root, and shoot Cd concentration decreased by 82.3 %, 77.0 %, and 75.6 %, respectively, compared to CK. Sequential-step extraction (BCR) analysis revealed a shift in soil Cd from stable to available forms, consistent with the available Cd (DTPA-Cd) results. All Zn treatments significantly reduced Cd accumulation, alleviated Cd-induced stress, and promoted spinach growth, with ZnO NPs demonstrating the highest Cd reduction and Zn bioaugmentation efficiencies compared to bulk ZnO and ZnSO4 at equivalent concentrations. Therefore, ZnO NPs offer a safer and more effective option for agricultural production and soil heavy metal pollution management than other Zn fertilizers.

Preparation of Experiments on Growing Zinc–Cadmium Telluride Crystals in Microgravity

Cd1-xZnxTe crystals are necessary for the production of ionizing radiation detectors widely used in science, technology, medicine and other fields. Internal stresses during crystallization lead to generation of dislocations and low-angle boundaries. Typical problem of melt crystal growth of Cd-Zn-Te compounds are tellurium inclusions, which deteriorate detector performance. Microgravity conditions provide unique opportunities for growing high-quality crystals due to the absence of convection, more equilibrium conditions of melt mixing, and a decrease in internal stresses. Since the properties of such crystals strongly depend on the production conditions, seeds and a feed ingot with specified compositions and structure are required. Ampoules with two compositions of materials have been prepared for the space experiment. Crystals of different compositions Cd0.96Zn0.04Te and Cd0.9Zn0.1Te were produced for two charges. They consist of an oriented seed, solvent, and feeding ingot, which are single-phased, single crystalline, have certain crystallographic orientation, meet demands for growth of Cd–Zn–Te crystals in microgravity. Ampoules containing these materials were sent to International Space Station for crystal growth on equipment already assembled at “Nauka” station.

Phytochelatins Bind Zn(II) with Micro- to Picomolar Affinities without the Formation of Binuclear Complexes, Exhibiting Zinc Buffering and Muffling Rather than Storing Functions.

Phytochelatins (PCs) are poly-Cys peptides containing a repeating γ-Glu-Cys motif synthesized in plants, algae, certain fungi, and worms by PC synthase from reduced glutathione. It has been shown that an excess of toxic metal ions induces their biosynthesis and that they are responsible for the detoxification process. Little is known about their participation in essential metal binding under nontoxic, basal conditions under which PC synthase is active. This study presents spectroscopic and thermodynamic interactions with the PC2-PC5 series, mainly focusing on the relations between Zn(II) complex stability and cellular Zn(II) availability. The investigations employed mass spectrometry, UV-vis spectroscopy, potentiometry, competition assays with zinc probes, and isothermal titration calorimetry (ITC). All peptides form ZnL complexes, while ZnL2 was found only for PC2, containing two to four sulfur donors in the coordination sphere. Binuclear species typical of Cd(II)-PC complexes are not formed in the case of Zn(II). Results demonstrate that the affinity for Zn(II) increases linearly from PC2 to PC4, ranging from micro- to low-picomolar. Further elongation does not significantly increase the stability. Stability elevation is driven mainly by entropic factors related to the chelate effect and conformational restriction rather than enthalpic factors related to the increasing number of sulfur donors. The affinity of the investigated PCs falls within the range of exchangeable Zn(II) concentrations (hundreds of pM) observed in plants, supporting for the first time a role of PCs both in buffering and in muffling cytosolic Zn(II) concentrations under normal conditions, not exposed to zinc excess, where short PCs have been identified in numerous studies. Furthermore, we found that Cd(II)-PC complexes demonstrate significantly higher metal capacities due to the formation of polynuclear species, which are lacking for Zn(II), supporting the role of PCs in Cd(II) storage (detoxification) and Zn(II) buffering and muffling. Our results on phytochelatins' coordination chemistry and thermodynamics are important for zinc biology and understanding the molecular basis of cadmium toxicity, leaving room for future studies.

Bioconcentration capacity of moss Leskea angustata Tayl., for heavy metals and its application in the atmospheric biomonitoring of a metropolitan area

In this work, the bioconcentration capacity of heavy metals Cd, Cu, Pb and Zn in the moss Leskea angustata Tayl., exposed under laboratory conditions was evaluated, and subsequently the usefulness of moss for the heavy metals' biomonitoring associated with suspended particulate matter in air of the Toluca Valley Metropolitan Area was determined by means of the moss bag technique. To achieve the aims, bioassays were carried out in the laboratory with the moss, the exposure for a period of 6 months of the moss bags in the sites of the Automatic Atmospheric Monitoring Network of the Government of the State of Mexico and their subsequent analysis through of elemental and structural characterization techniques. The results of the bioassays on the moss L. angustata, demonstrate that this moss has adequate bioconcentration capabilities to be used as a biomonitor of heavy metals in polluted areas. The structural characterization of the moss L. angustata, shows that this moss has good adsorption characteristics (presence of functional groups, surface area of 19.87 m2 g−1, average pore diameter equal to 2.86 nm and a total pore volume of 0.014218 cm3 g−1). The significant correlations between Cd–Zn–Pb and between Pb and Zn with PM2.5, as well as a strong correlation between Pb and Zn with PM10, allow us to establish that these three metals have their main origin in the domestic combustion of wood and liquid petroleum gas (LP gas), as well as emissions from agricultural burning in the study area. Cu has a different origin than other metals and PM10 and PM2.5. The findings demonstrate a strong association between anthropogenic activities - such as domestic wood and LP gas combustion, agricultural burning emissions, vehicular emissions, tire wear, and industrial activities - and the detection, entrapment, and accumulation of several heavy metals by L. angustata moss.

Differentiating anthropogenic effects from natural metal(loid) levels in residential soil near a zinc smelter in South Korea.

Metal(loid)s pose a significant hazard due to inherent toxicity. Individuals are particularly exposed to metal(loid)s in soil through direct or indirect contact. Identifying metal(loid) sources in soil is required for exposure mitigation to anthropogenic metal(loid)s, while metal(loid)s are natural constitutes of soil. Metal(loid) concentrations and Pb isotopes were determined in residential soil profiles impacted by a Zn smelter to distinguish the anthropogenic effect from natural levels. One hundred sixty-nine core soil samples were collected from depths down to 5.5m below ground level at 19 sites and were divided into Zn-Cd-As- and As-contaminated groups based on the worrisome level (WL) of soil contamination. The Zn-Cd-As-contaminated group (n = 62) was observed at depths < 1m, showed high Zn levels (mean of 1168mg/kg) and Cd and As frequently exceeding WLs, and had low 206Pb/207Pb ratios close to the Zn smelter. In contrast, the As-contaminated group (n = 96) was observed at depths > 1m, did not have other metals exceeding WLs, and showed a wide range of 206Pb/207Pb ratios far away from the Zn smelter. The results indicated that the pollution sources of Zn-Cd-As- and As-contaminated soils were fugitive dust emissions from smelter stacks and geology, respectively. The metal(loid)s in host rock set geochemical baselines in soil profiles, while smelting activities affected the upper layers over 50years. This study demonstrated the effectiveness of utilizing the vertical distribution of metal(loid) concentrations and Pb isotopes in soil profiles for distinguishing between anthropogenic and geogenic origins, in combination with baseline assessment.

Bioindicator responses to extreme conditions: Insights into pH and bioavailable metals under acidic metal environments

Acid mine drainage (AMD) caused environmental risks from heavy metal pollution, requiring treatment methods such as chemical precipitation and biological treatment. Monitoring and adapting treatment processes was crucial for success, but cost-effective pollution monitoring methods were lacking. Using bioindicators measured through 16S rRNA was a promising method to assess environmental pollution. This study evaluated the effects of AMD on ecological health using the ecological risk index (RI) and the Risk Assessment Code (RAC) indices. Additionally, we also examined how acidic metal stress affected the diversity of bacteria and fungi, as well as their networks. Bioindicators were identified using linear discriminant analysis effect size (LEfSe), Partial least squares regression (PLS-R), and Spearman analyses. The study found that Cd, Cu, Pb, and As pose potential ecological risks in that order. Fungal diversity decreased by 44.88% in AMD-affected areas, more than the 33.61% decrease in bacterial diversity. Microbial diversity was positively correlated with pH (r = 0.88, p = 0.04) and negatively correlated with bioavailable metal concentrations (r = −0.59, p = 0.05). Similarly, microbial diversity was negatively correlated with bioavailable metal concentrations (bio_Cu, bio_Pb, bio_Cd) (r = 0.79, p = 0.03). Acidiferrobacter and Thermoplasmataceae were prevalent in acidic metal environments, while Puia and Chitinophagaceae were identified as biomarker species in the control area (LDA>4). Acidiferrobacter and Thermoplasmataceae were found to be pH-tolerant bioindicators with high reliability (r = 1, P < 0.05, BW > 0.1) through PLS-R and Spearman analysis. Conversely, Puia and Chitinophagaceae were pH-sensitive bioindicators, while Teratosphaeriaceae was a potential bioindicator for Cu–Zn–Cd metal pollution. This study identified bioindicator species for acid and metal pollution in AMD habitats. This study outlined the focus of biological monitoring in AMD acidic stress environments, including extreme pH, heavy metal pollutants, and indicator species. It also provided essential information for heavy metal bioremediation, such as the role of omics and the effects of organic matter on metal bioavailability.

Deposition of Fine-Pitch Indium Bumps on Single Die

Photolithographic lift-off at wafer level is a wellestablished method for depositing indium bumps onto pixels of electronic components such as sensors and application-specific integrated circuits (ASIC). These indium bumps form interconnects between pixels of the components during flip-chip bonding to make devices such as radiation detectors. Such components are not always available on wafer-scale, and single dies need to be processed in small-scale production, R&amp;D, or for Cd(Zn)Te detector material. Photolithography on single dies is ineffective due to the edge-bead of photoresist that compromises perfect indium deposition onto pixels near the periphery of the die. To utilize the maximum surface area of a die, a rigid mask with apertures (shadow mask) is an adequate substitute for the photoresist. Different mask designs and production techniques for fine-pitch indium bump arrays are investigated by testing electroformed stencils or micromachined silicon (Si) membranes as shadow masks. For the indium deposition, the sensor and ASIC dies are clamped into custom-made jigs that include shadow masks. Alternatively, dies can be adhered to shadow masks with soluble adhesive. The apertures of a mask are aligned to the pixel array of the detector component. Bump arrays with 250μm- and 100μm-pitch were demonstrated with electroformed stencils. For smaller pitch (55μm) and bump diameter of ~20μm, specialized masks from Si membranes are tested. Components with successfully deposited indium bump arrays were subsequently flip-chip bonded at room temperature without reflowing the indium. A bond yield of at least 99.9% pixels for such flip-chip bonded radiation detector was shown using the read-out signal from exposure with a flat field X-ray radiation of an Am-241 sealed source.

Evaluation of Zn–Cd–Sn–S nanostructures for in vitro pyrene degradation and antimicrobial activity

The present work describes the fabrication of the quaternary Zn–Cd–Sn–S nanostructure and its use in photocatalytic remediation of the biological contaminant pyrene from water resources. Nanostructures fabricated were characterized by XRD, UV-DRS, FTIR, DLS, EDX, and SEM. In addition, an agar well diffusion test was conducted to determine the antimicrobial activity. Zn–Cd–Sn–S (ZCSS) nanostructures were evaluated for their photocatalytic degrading potential by using pyrene as a model pollutant and evaluating the effects of parameters like initial pyrene concentration, nanocatalyst dosage, solution pH, and light sources during batch adsorption. Nanostructures had a size of 16.74 nm according to the XRD analysis. With a 300 min time interval, ZCSS nanostructures achieved the highest removal rate of 86.3%. Pyrene degradation metabolites were identified using GC-MS analysis of the degraded samples. A Freundlich isothermal (R2 0.9) and pseudo-first-order (R2 0.952) reaction kinetic path best fit the adsorption results for pyrene by the fabricated ZCSS nanostructure, based on the adsorption and kinetic studies. Zn–Cd–Sn–S exhibited the highest antibacterial activity against Staphylococcusaureus (22.4 mM). Due to the combined synergistic actions of the constituent metals, this quaternary nanostructure exhibited exceptional photocatalytic activity. To our est knowledge, the ZCSS nanostructure was made and used to remove pyrene by photocatalysis and fight microbes. Ultimately, the ZCSS nanostructure was found to be an effective photocatalyst for eradicating pathogenic microbes from water.

Early-stage growth and elemental composition patterns of Brassica napus L. in response to Cd–Zn contamination

Soil contamination caused by the presence of Cd and the excess amount of Zn is a widespread concern in agricultural areas, posing significant risks to the growth and development of crops. In this paper, the early-stage development and metal (Cd and Zn) accumulation potential of rapeseed (Brassica napus L.) grown under different metal application schemes were assessed by determining radicle and hypocotyl length and the micro- and macro elemental composition of plantlets after 24, 72, and 120 h. The results indicated that the single and co-application of Cd and Zn significantly reduced the radicle and hypocotyl lengths. Accumulation intensity for Cd and Zn was affected by Cd and the combination of Cd and Zn in the solution, respectively. In addition, both metals significantly influenced the tissue Mn and had a minor effect on Cu and Fe concentrations. Both Cd and Zn significantly affected macro element concentrations by decreasing tissue Ca and influencing K and Mg concentrations in a dose- and exposure time-dependent manner. These findings specify the short-term and support the long-term use of rapeseed in remediation processes. However, interactions of metals are crucial in determining the concentration patterns in tissues, which deserves more attention in future investigations.

Optical, structural, morphological and photocatalytic characters of Mn-doped Cd0.9Zn0.1S quantum dots

The Cd0.9Zn0.1MnxS (Mn = 0–4 %) QDs were synthesised using the co-precipitation route, and their structural, morphological, optical, and photocatalytic natures were investigated. The XRD studies confirmed the cubic nature of Zn and Mn-doped CdS without the formation of a secondary phase. The fine-tuning of size and lattice parameters was explored by Mn levels and the defects associated with Mn2+. The optical properties and band gap of Cd0.9Zn0.1S are tuned well by the incorporation of Mn2+ ions. Cd–Zn–S and Cd–Zn–Mn–S bondings were confirmed by FTIR studies. The high-intense PL emissions (blue, green and yellow) at Mn 2%-doped Cd0.9Zn0.1S were described by the weakening of size and the Mn-based defects. Zn and Mn dual-doped CdS are recommended as potential photocatalysts for the exclusion of dyes and this is confirmed using methylene blue. The enhanced catalytic action in Zn and Mn-added CdS is caused by the release of charge carriers and the creation of defects, which demonstrated better efficiency after six re-cycling processes.

Luminescent properties of Cd(x)Zn(1-x)S nanocrystals formed in the matrix of a Langmuir–Blodgett film

At a temperature of 80–300 K, the photoluminescence of Cd(x)Zn(1-x)S nanocrystals (x = 0.2 and 0.5) formed in a Langmuir–Blodgett film was studied. Two peaks can be distinguished in the PL spectra: (i) a low-energy peak, which is portable and changes significantly with increasing zinc content in nanocrystals and temperature, and (ii) a high-energy peak, the position of which weakly depends on temperature and nanocrystal content. It was found that the high-energy peak is most pronounced at elevated temperatures (&gt;290 K). Experimental data are performed by recombination through levels of deep centers associated with the intrinsic defects and behenic acid molecules on the surface of nanocrystals.

Assessment of trace elements in the long-term banana cultivation field’s soil

This work assesses the contamination of trace elements (Cr, Cu, Ni, As, Zn Cd, Mn, Fe, and Pb) in soil and different tissues of the banana plant (Musa spp.), the ecological risks of trace elements using various indices, and the probable health risks using a chemometric approach. Soil and different banana plant tissues were collected from banana fields around the industrial area of the capital of old Pundranagar (the earliest urban archaeological location), Bangladesh. Samples were digested by acid digestion, and trace elements were measured by inductively coupled plasma spectrophotometer (ICP-MS). The concentrations of Cr, Ni, Cu, As, Cd, Pb, Fe, Mn, and Zn in soil ranged from 1.50–61.7, 2.42–87.4, 2.00–100.8, 0.25–31.2, 0.10–12.7, 0.60–91.8, 11330–23782, 8.69–105.9, and 7.50–125.9 mg/kg, respectively. The mean concentrations of trace elements in four tissues descend in order of roots &amp;gt; leaves &amp;gt; stems &amp;gt; fruits. The abundances of trace elements varied in both soil and plant samples, which apparently occurred due to the variations of soil parent materials and the excessive use of agrochemicals for long-term banana cultivation. The soil exhibited a moderate to high degree of contamination with trace elements, and Cr, Pb, Zn, Cd, and As mainly originated from anthropogenic sources. Both non-cancer and cancer risks were perceived due to Cr and As exposure from the fruit tissue of banana plants in the study area.

Heavy Metals in Urban Soils of the Volga Federal District: a Conjugate Analysis of Official Data

Based on a conjugated analysis of the official data of Roshydromet on the content of priority heavy metals (Cd, Pb, Zn, Cu, Ni) in the soils of 23 cities of the Volga Federal District, as well as Rosstat data on the socio-economic indicators of these settlements, the ecological and geochemical characteristics of urbanozems (Urbic Technosols) and with the help of multivariate statistical analyzes (cluster and factorial), possible relationships between soil pollution parameters and urban features of cities were revealed. For the soils of most cities in the region with average socioeconomic indicators, admissible levels of accumulation of Cd, Pb, Zn, and Cu have been established, which, in terms of concentrations, are close to the average abundance of urban soils in Russia. In small and medium-sized cities of the Republic of Bashkortostan, exceedances of APC Ni in soils are recorded, which reflects the presence of a regional geochemical anomaly of natural and anthropogenic nature in the eastern part of the Volga Federal District, but no correlations between nickel pollution and socio-economic indicators of settlements are revealed. The moderately hazardous level of complex pollution in urbanozems with dominant accumulation of Cd and significantly lower concentration ratios of other heavy metals (Belebey, Davlekanovo, Dzerzhinsk) shows no correlation with the demographic indicators of settlements. The more complex profile of soil pollution (Cd–Zn in Penza or Cu–Cd–Zn in Mednogorsk) shows lower values of the total fertility rate and higher values of the mortality rate (compared with the average regional indicators). In general, using the example of the cities of the Volga Federal District, it is shown that the gradients of increasing concentrations in soils of Cd, Pb, Zn, Cu and the total pollution index Zc are codirectional with an increase in the general mortality rate of the population.

Effect of red mud on combustion behavior and heavy metal stabilization of Refuse Derived Fuel (RDF)

Refused Derived Fuel (RDF) from municipal solid waste has become a promising and effective approach for waste storage and utilization. However, the poor combustion performance and heavy metals (HMs) emission limit the development of this technology. In this study, red mud (RM), an industrial waste from the alumina extraction process, was used as an additive to improve the combustion behavior of RDF. The results show that 10 wt% of red mud addition can increase the flammability index (F) and the comprehensive combustion characteristic index (S) by 91% and 156%, respectively. It significantly reduced the burnout temperature of RDF by 59 °C. Moreover, RM also promoted the transformation of HMs into more stable forms. The proportion of F4 speciation for Cr, Ni, Cu, Zn Cd, and Pb in ash residues increased by 6.42%, 50.91%, 92.48%, 43.77%, 15.77%, and 4.53%, respectively, while the leaching rate of Cr, Ni, and Cd decreased by 1.7%, 0.99%, and 1.31%. The findings proved that RM could serve as an efficient additive for enhancing RDF combustion and stabilizing the HMs in ash residues, which would provide new insight into the co-utilization of wastes and the contribution to the clean combustion of RDF.

Volatilization characteristic and solidification of Pb, Zn, Cd and as during cement kiln co-processing of solid waste

Cement kiln co-processing always became one of the predominate approaches to dispose hazardous solid waste containing heavy metals. The volatilization and morphology of heavy metals should be paid to more concern during the cement production due to the environmental risk of heavy metals. In this study, the volatilization characteristics and the solidification effect of heavy metals (Pb, Zn Cd and As) during cement kiln co-processing were explored by the lab and pilot scale experiments. At same experimental conditions, the volatilization rate followed as As > Pb > Cd > Zn. Both limestone and cement raw meal have been demonstrated the capability to mitigate the rates of heavy metal volatilization. Notably, cement raw meal displays a more pronounced effect compared to limestone in suppressing volatilization processes. Over 50% of heavy metals were transformed into residual state at 1400 °C, and Cd, As and Zn were easy to be solidified than Pb. A pilot scale experiment proved that more than 80% of heavy metals was solidified, and Zn reached nearly 100%. Moreover, around 80% of Cd, As and Zn were remained in clinker and the rest was distributed in kiln dust particles, only very few amount was released into the exhaust flue gas. This study provides a comprehensive and extensive understanding of the volatilization characteristics and migration patterns of heavy metals in the cement kiln environment. It offers theoretical support for the control of heavy metals during the co-processing of hazardous solid waste in cement kilns.

Optical Emission Spectroscopy Characterization of Nanosecond Pulsed Laser Ablation of ZnCd Plasma Plume

This work used spectroscopic plasma emission analysis to investigate the parameters of Zn–Cd plasma formed in the atmosphere by a Q-switched Nd:YAG nanosecond laser system emitting infrared (1064[Formula: see text]nm) laser light with an energy output spanning 200[Formula: see text]mJ to 500[Formula: see text]mJ. The spectrometer was used to examine and record the emission spectrum profiles of (ZnCd), which helped to extract crucial plasma characteristics (i.e., [Formula: see text] and [Formula: see text]. The electron density was measured using the Stark broadening, and the plasma temperature was calculated using the Boltzmann plot technique. The electron temperature was between 1.02[Formula: see text]eV and 1.39[Formula: see text]eV, and the electron density was between (39.05 and 50.66) [Formula: see text][Formula: see text]cm[Formula: see text]. The Debye length (l), the number of particles in the Debye sphere ([Formula: see text] and the plasma frequency ([Formula: see text] can all be estimated from the electron temperature ([Formula: see text] and the electron density ([Formula: see text] ([Formula: see text]. Results indicate that plasma parameters are proportional to the energy of laser due to the increase in the intensity of spectral lines energy, and that plasma shielding of ZnCd increases with laser energy in the range of (1.20–1.23).