Addition Of Cd Research Articles

Metal cations enhanced the bonding of Sb(V) on adsorbent surfaces: An effective strategy for adsorbent engineering

The adsorption capacity of the adsorbent for pentavalent antimony (Sb(V)) is limited by its strong electronegativity and high solubility, and the mechanism of how the presence of coexisting cations in the wastewater can modulate this adsorption process is still understudied. In this study, the effect of coexisting metal cations on Sb(V) bonding on the adsorbent surface was determined using magnetic carbon nanotube adsorbents (FeOx@CNTs) as an example. The experimental design and theoretical calculations demonstrated that the metal cations could enhance the removal of Sb(V) by the adsorbent (4-fold enhancement of Sb(V) adsorption in the presence of Cd(II) coexistence). The addition of Cd(II) increased the FeOx@CNTs surface potential and enhanced the adsorption performance. The complexation of hydroxyl functional groups with iron oxides and the co-precipitation of FeOx/Cd(II) with Sb (V) were the primary factors to enhance the removal of Sb(V). Density functional theory (DFT) calculations demonstrated that the Sb(V) adsorption energy (Ead) on FeOx was −4.28 eV, while the introduction of Cd(II) increased the adsorption energy to −5.09 eV, facilitating an easier and more stable adsorption process. Analysis of the partial density of states (PDOS) and d-band center theory argued the Sb(V) chemisorption on the FeOx surface and its enhanced electron transport capacity (the presence of Cd(II) brings the d-band center of FeOx closer to the Fermi energy level from −0.786 to −0.739 eV). In the Sb(III) and Sb(V) synergistic adsorption system, the addition of Cd(II) not only did not inhibit the adsorption performance of Sb(III), but also enhanced the Sb(V) uptake on FeOx@CNTs. This study lays a foundation for exploring the mechanism of co-existing metal cation adsorption in real antimony (Sb)-containing wastewater, and also provides a new idea and an effective strategy for adsorbent engineering.

Interaction and Transport Characteristics of Lead and Cadmium in Different Soil-wheat Systems

In this study, four groups of lead(Pb) and cadmium(Cd) combined treatments with different concentration ratios were set up in Hailun black soil, Xianning brown-red soil, and Changwu Heilu soil, and wheat(Zhengmai 9023) was planted for a five-month pot experiment to analyze the Pb-Cd interaction behavior on heavy metal bioaccumulation in wheat under three soil-wheat systems. The low pH brown-red soil had the highest water-soluble Cd and Pb contents with significant Pb-Cd interactions in the soil, whereas the black soil with high organic matter and Heilu soil with high calcium carbonate content exhibited lower Cd and Pb activities. Among the three soils, wheat height and dry weight showed the poorest growth performance in the Heilu soil, but the wheat height increased by 2.68-8.49 cm compared with that in the control under the Pb-Cd combined treatment, whereas Pb-Cd interaction had the least effect on wheat height and dry weight in black soil and inhibited the growth of wheat in the brown-red soil. In the transport process of Cd or Pb in wheat, Pb-Cd interaction showed quite different effects in the three soil-wheat systems. Under the 125 mg·kg-1 and 250 mg·kg-1 Pb treatments, the Pb content in wheat grain planted in brown-red soil significantly increased by 73.2% and 19.1% with the addition of Cd, respectively, and therefore there was a synergistic effect between Pb and Cd. Under the 0.3 mg·kg-1 and 0.6 mg·kg-1 Cd treatments, the Cd content in wheat grains planted in black soil decreased by 51% and 33% with the addition of Pb, respectively; therefore, there was an antagonist effect between Pb and Cd. In the Heilu soil, a synergistic effect of Cd on Pb transport in wheat leaves was only observed under high Pb treatment. Therefore, pH and organic matter content were the key factors that determined the interaction behavior of Pb and Cd. The wheat food security risk of Pb and Cd combined pollution was higher than that of single metal pollution in acidic brown-red soil and lower in high organic matter black soil, whereas the interaction of Pb and Cd had little impact on the wheat food security risk of alkaline Heilu soil.

Differences in heavy metal binding to cysteine-containing coiled-coil peptides.

One third of all structurally characterised proteins contain a metal; however, the interplay between metal-binding and peptide/protein folding has yet to be fully elucidated. To better understand how metal binding affects peptide folding, a range of metals should be studied within a specific scaffold. To this end, we modified a histidine-containing coiled-coil peptide to create a cysteine-containing scaffold, named CX3C, which was designed to bind heavy metal ions. In addition, we generated a peptide named CX2C, which contains a binding site more commonly found in natural proteins. Using a combination of analytical techniques including circular dichroism (CD) spectroscopy, UV-Vis spectroscopy and size-exclusion chromatography coupled to multi-angle light scattering (SEC-MALS), we examined the differences in the metal-binding properties of the two peptides. Both peptides are largely unfolded in the apo state due to the disruption of the hydrophobic core by inclusion of the polar cysteine residues. However, this unfolding is overcome by the addition of Cd(II), Pb(II) and Hg(II), and helical assemblies are formed. Both peptides have differing affinities for these metal ions, a fact likely attributed to the differing sizes of the ions. We also show that the oligomerisation state of the peptide complexes and the coordination geometries of the metal ions differ between the two peptide scaffolds. These findings highlight that subtle changes in the primary structure of a peptide can have considerable implications for metal binding.

Differences in Cadmium Uptake and Accumulation in Seedlings of Wheat Varieties with Low- and High-Grain Cadmium Accumulation under Different Drought Stresses.

Cadmium (Cd) and drought, as abiotic stresses, have long been significant challenges for crop growth and agricultural production. However, there have been relatively few studies conducted on the effects of drought stress on Cd uptake, especially regarding the differences in Cd uptake characterization in varieties with varying Cd accumulation under different drought stress. To investigate the effects of drought conditions on Cd uptake by wheat in different genotypes under specific background levels of Cd pollution, we validated the differences in root absorption characteristics of low- (YM) and high-grain Cd accumulating wheat genotypes (XM) using non-invasive micro-test technology, and we conducted a hydroponic experiment on the Cd addition and different drought levels in a climate-controlled chamber. The biomass, root morphology, Cd uptake, and accumulation were determined under Cd (100 µmol L-1) and different drought levels of 0% (0 MPa), 5% (-0.100 Mpa), 10% (-0.200 Mpa), and 15% (-0.388 Mpa) simulated by polyethylene glycol (PEG-6000). We found that the simultaneous exposure to Cd and drought had a suppressive effect on the total root lengths, root surface areas, and root volumes of XM and YM, albeit with distinct patterns of variation. As the concentration of PEG-6000 increased, the Cd concentrations and the amount of Cd accumulated in the roots and shoots of XM and YM decreased. Specifically, the Cd concentration in the roots exhibited a reduction ranging from 12.51% to 66.90%, while the Cd concentration in the shoots experienced an even greater decrease of 50.46% to 80.57%. The PEG-6000 concentration was significantly negatively correlated (p < 0.001) with Cd concentration of roots and shoots and Cd accumulation in roots, shoots, and the whole plants and significantly negatively correlated (p < 0.05) with the total length, surface area, and volume of roots. This study confirms that drought stress (5% PEG-6000) can decrease the uptake and accumulation of Cd in wheat seedlings without significant inhibition of biomass, and the change of root morphology (root length) and the decrease of Cd concentration in roots may be the main direct pathways for achieving these effects under drought stress. This research provides a new perspective and idea for water management in Cd-contaminated farmland.

Cadmium reduced methane emissions by stimulating methane oxidation in paddy soils

Flooded rice paddy fields are a significant source of anthropogenic methane (CH4) emissions. Cadmium (Cd) is one of the most common and toxic contaminants in paddy soils. However, little is known about how the soil microbial communities associated with CH4 emissions respond to the increasing Cd-stress in paddies. In this study, we employed isotopically 13C-labelled CH4, high-throughput sequencing analysis, and gene quantification analysis to reveal the effect and mechanism of Cd on CH4 emissions in paddy soils. Results showed that 4.0 mg kg−1 Cd addition reduced CH4 emissions by 16–99% in the four tested paddy soils, and significantly promoted the transformation of 13CH4 to 13CO2. Quantitative polymerase chain reaction (qPCR) demonstrated that Cd addition increased the abundances of pmoA gene, the ratios of methanogens to methanotrophs (mcrA/pmoA) showed a positive correlation with CH4 emissions (R2 = 0.798, p < 0.01). Furthermore, the composition of the microbial community containing the pmoA gene was barely affected by Cd addition (p > 0.05). This observation was consistent with the findings of a pure incubation experiment where methanotrophs exhibited high tolerance to Cd. We argue that microbial feedback to Cd stress amplifies the contribution of methanotrophs to CH4 oxidation in rice fields through the complex interactions occurring among soil microbes. Our study highlights the overlooked association between Cd and CH4 dynamics, offering a better understanding of the role of rice paddies in global CH4 cycling.

Effective citric acid and EDTA treatments in cadmium stress tolerance in pepper (Capsicum annuum L.) seedlings by regulating specific gene expression

Soil contamination with toxic environmental pollutants [such as cadmium (Cd)] is becoming a serious global problem due to rapid development of social economy. To improve the growth and yield of a plant, various chelating agents, such as ethylenediaminetetraacetic acid (EDTA) and citric acid (CA), can be applied to the soil; such application not only increases plant uptake of metals from the soil but also promotes plant absorption of micronutrient fertilizers from the medium. For this purpose, we have conducted a pot experiment using the exogenous application of CA (2.5 mM) and EDTA (2.5 mM) in pepper (Capsicum annuum L.) seedlings grown under the varying levels of Cd (0, 50 and 100 µM) in the soil. M]. Our results depicted that Cd addition to the soil significantly (P < 0.05) decreased plant growth and biomass, gas exchange attributes, and mineral uptake by C. annuum when compared to the plants grown without the addition of Cd. However, Cd toxicity boosted the production of reactive oxygen species (ROS) by increasing the content of malondialdehyde (MDA), which is the indication of oxidative stress in C. annuum, and was also manifested by hydrogen peroxide (H2O2) content and electrolyte leakage to the membrane-bound organelles. The results showed that the activities of various antioxidative enzymes, such as superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), and their specific gene expression and also the content of non-enzymatic antioxidants, such as phenolic, flavonoid, ascorbic acid, and anthocyanin, initially increased with an increase in the Cd concentration in the soil. The results also revealed that the levels of soluble sugar, reducing sugar, and non-reducing sugar were decreased in plants grown under elevating Cd levels, but the accumulation of the metal in the roots and shoots of C. annuum, was found to be increased. The negative impacts of Cd injury were reduced by the application of EDTA and CA, which increased plant growth and biomass, improved photosynthetic apparatus, antioxidant enzymes and their gene expression, and mineral uptake, as well as diminished the exudation of organic acids and oxidative stress indicators in C. annuum by decreasing Cd toxicity. Here, we conclude that the application of EDTA and CA under the exposure to Cd stress significantly improved plant growth and biomass, photosynthetic pigments, and gas exchange characteristics; regulated antioxidant defense system and essential nutrient uptake; and balanced organic acid exudation pattern in C. annuum.

Biochar improves the yield and quality of Erigeron breviscapus in heavily cadmium-polluted soil

Simultaneously utilizing and remediating soil contaminated with cadmium (Cd) is propitious and economically beneficial. In this study, Erigeron breviscapus, a raw medicinal material used to extract scutellarin, was utilized to conduct a pot experiment including five treatments. Under a control without Cd and biochar addition (CK), soil exogenously added with high concentration of Cd (0.01%) were used to investigate the effects of different biochar doses (0%, 5%, 10%, and 15%, denoted as CdB0, CdB5, CdB10, and CdB15, respectively) on the yield (shoot biomass) and quality (represented by scutellarin content) of E. breviscapus as well as soil remediation. The results showed that soil with addition of high Cd decreased the shoot biomass and scutellarin content of E. breviscapus by 33.6% and 70.8%, respectively. Compared with CdB0, the shoot biomass and scutellarin content of CdB15 increased by 24.7% and 312.0%, respectively. Biochar application (CdB5, CdB10, and CdB15) changed the soil Cd speciation and reduced the soil available Cd and plant Cd concentrations by 17.4%–121.8% and 26.4%–42.6%, respectively, compared with CdB0. However, the chlorophyll content, catalase activity, and acquisition of N, Fe, and Cu of E. breviscapus were increased in CdB5, CdB10, and CdB15 compared with CdB0. In addition, the Cd toxicity mitigation effect enhanced with increasing biochar application, and the application of 15% biochar resulted in the highest shoot biomass and scutellarin content of E. breviscapus. The results of this study highlight the importance of biochar for improving the Cd adaptability of E. breviscapus and provide a reference for the simultaneous utilization and remediation of heavily Cd-contaminated soil.

Ciprofloxacin enhances cadmium toxicity to earthworm Eisenia fetida by altering the gut microorganism composition

The concurrent existence of cadmium (Cd) and ciprofloxacin (CIP) in agricultural soils is very common, but presents a challenge to soil organisms. As more attention has been paid to the effect of toxic metals on the migration of antibiotic resistance genes, the critical role of the gut microbiota in CIP-modifying Cd toxicity in earthworms remains unclear. In this study, Eisenia fetida was exposed to Cd and CIP alone or in combination at environmentally relevant concentrations. Cd and CIP accumulation in earthworm increased as their respective spiked concentrations increased. In fact, Cd accumulation increased by 39.7% when 1 mg/kg CIP was added; however, the addition of Cd did not affect CIP uptake. Compared with exposure to Cd alone, a greater ingestion of Cd following combined exposure to Cd and 1 mg/kg CIP resulted in greater oxidative stress and energy metabolism disturbances in earthworms. The reactive oxygen species (ROS) contents and apoptosis rate of coelomocytes were more sensitive to Cd than these biochemical indicators. In fact, 1 mg/kg Cd induced the derivation of ROS. Similarly, the toxicity of Cd (5 mg/kg) to coelomocytes was promoted by CIP (1 mg/kg), ROS content in coelomocytes and the apoptosis rate increased by 29.2% and 113.1%, respectively, due to increased Cd accumulation. Further investigation of the gut microorganisms revealed that the decreased abundance of Streptomyces strains (known as Cd accumulation taxa) could be a critical factor for enhanced Cd accumulation and greater Cd toxicity to earthworms following exposure to both Cd and CIP; this was because this microorganism group was eliminated by the simultaneous ingestion of CIP. This study stressed the role of gut microorganisms in altering the toxicity of Cd and CIP combined contamination in soil organisms. More attention should be paid to the ecological risks of such combined contamination in soils.

Stability of exogenous Cadmium in different vineyard soils and its effect on grape seedlings

Cadmium (Cd) being potentially toxic heavy metal, has become increasingly serious to vineyard soil and grapes in recent years. Soil type is one of the main factors affecting the absorption of Cd in grapes. To investigate the stabilization characteristics and form changes of Cd in different types of vineyard soils, a 90-days incubation experiment was conducted after exogenous Cd addition to 12 vineyard soils from typical vineyards in China. The inhibition of exogenous Cd on grape seedlings was determined based on the pit-pot incubation experiment (200 kg soil per pot). The results demonstrate that Cd concentration in all the sampling sites did not exceed the national screening values (GB15618-2018; i.e., 0.3 mg/kg when pH was lower than 7.5, 0.6 mg/kg when pH was higher than 7.5);. Cd in Fluvo-aquic soil 2, Red soils1, 2, 3 and Grey-Cinnamon soil is dominated by acid-soluble fraction, but was mainly in residual fraction in the remain soils. Throughout the aging process, proportion of the acid-soluble fraction increased and then decreased, while proportion of the residual fraction decreased and then increased, after exogenous Cd was added. The mobility coefficients of Cd in Fluvo-aquic soil 2 and Red soil 1, 2 increased 2.5, 3 and 2 folds, after exogenous Cd addition, respectively. Compared with CK (control), the correlation between total Cd content and its different fractions was relatively weak in the Cdl (low concentration) and Cdh (high concentration) groups. Poor Cd stabilization and strong inhibition of seedling growth rate were observed in Brown soil 1, black soil, red soil 1 and cinnamomic soil. Fluvo-aquic soil 2, 3 and Brown soil 2 showed good Cd stability and small inhibition effect on grape seedlings. These results show that Cd stability in soils and inhibition rate of grape seedlings by Cd are strongly influenced by soil type.

The solidification and volatilization behavior of heavy metal ions in ceramic proppant made from fly ash

As a type of silica-alumina solid waste, fly ash can be utilized to prepare ceramic proppants by partially substituting bauxite due to a similar chemical composition. However, the heavy metal elements in fly ash including Zn and Cd are subjected to be released during high-temperature calcination, causing harm to some extent. In this study, migration, transformation, solidification, and volatilization of heavy metals in proppant at elevated temperatures are systematically studied by various experimental characterization methods. The results show that the solidification effect of the prepared ceramic proppant on the Zn and Cd elements is favorable, with solidification ratios up to 77.16% and 74.34%. The addition of Cd improves the bulk density and strength of the ceramic proppant, while the addition of Zn significantly reduces the strength and increases the water absorption. Additionally, the majority of doped Zn will combine with Al2O3 to form a new phase, zinc spinel ZnAl2O4, which hinders the formation of the inherent mullite phase. On the contrary, the addition of Cd does not change the phase composition, and the Cd element is mainly solidified in the form of lattice substitution. Finally, the distributions of volatile Zn and Cd in gas- and solid-phase were quantitatively determined by the in situ continuous collection system. In addition, a mathematical model was used to predict the volatilization of heavy metals during the proppant calcination process.

Spectroscopic studies of heavy metal cations influence on the structure of synthetic hydrated calcium aluminosilicates.

Calcium aluminosilicate hydrates (C-(A)-S-H) with two different C/S molar ratios of 1.0 and 1.7 were synthesized by precipitation with the use of the alkali-activation method. The samples were synthesized with solutions of heavy metals nitrates such as nickel (Ni), chromium (Cr), cobalt (Co), lead (Pb), and zinc (Zn). Metal cations were added in the amount of Ca:Me equal to 9:1, while Al/Si was 0.05. The influence of the addition of heavy metal cations on the structure of the C-(A-)S-H phase was investigated. For this purpose, XRD was used to examine the phase composition of the samples, FT-IR and Raman spectroscopy were used to determine the effect of heavy metal cations on the structure of the obtained C-(A)-S-H phase and their degree of polymerization. Using SEM and TEM, changes in the morphology of the obtained materials were determined. Possible mechanisms of immobilization of heavy metal cations have been determined. It was found that some heavy metals (Ni, Zn, and Cr) could be immobilized by precipitation of insoluble compounds. On the other hand, they could remove Ca2+ ions from the structure of aluminosilicate and take their place, as evidenced by the crystallization of Ca(OH)2 in samples with the addition of Cd, but also Ni and Zn in small amounts. A third possibility is the incorporation of heavy metal cations at the silicon and/or aluminum tetrahedral sites, as is the case with Zn.

Simulation of neutron shielding performance of Al-Cd alloy for radioactive waste container

Neutron shielding material is necessary for the container of radioactive waste emitting neutrons, such as spent fuel from research reactor. This study aimed to determine the shielding performance of Al-Cd material for neutron radiation emitted by radioactive radiation. The calculations of neutron shielding were carried out using MNCP5 software. The Al-Cd shielding was simulated to withstand a neutron radiation source with 2.538×10−8 MeV energy and 4.5 MeV energy moderated with paraffin. The Al-Cd was simulated as a homogeneously-mixed alloy and Al coated with Cd. The results show that addition of Cd to Al increased the neutron shielding performance for thermal and fast neutron. With the addition of 10% Cd to Al, the neutron shielding performance increased by more than 90% for thermal neutron, and 30% for fast energy neutron moderated with 5 cm thick paraffin. It shows that Al-Cd alloy is potential for radioactive waste container which requires high neutron shielding performance.

Effect of Cd toxicity on root morphology, ultrastructure, Cd uptake and accumulation of wheat under intercropping with Solanum nigrum L.

In order to evaluate the effect of intercropping of the hyperaccumulator, Solanum nigrum L. and wheat on the absorption and accumulation of cadmium (Cd) in wheat. The experiment was conducted with three replicates, which conducted on four Cd concentrations (0, 20, 40, 60 μmol L−1) in the Hoagland solution and using two planting patterns [monoculture wheat (MW), intercropping wheat and Solanum nigrum L. (IW，IS)]. The results showed that the addition of Cd in the solutions reduced the total root length by 19.08–55.98%, total root area by 12.35–44.48%, and total root volume by 16.01–46.00% of wheat plants. Intercropping with Solanum nigrum L. significantly reduced Cd contents by 28.3–47.2% and Cd accumulations by 10.08–32.43% in the roots of wheat. Transmission electron microscope (TEM) revealed that the root-tip cells of the monoculture wheat treated with Cd exhibited swollen spheres of intracellular mitochondria, disorderly arranged inner ridges of mitochondria, some damaged mitochondrial membranes, and deformed nuclear membranes. Many dense electron particles in the form of Cd were deposited in the cell gap, and the cell nucleus became smaller or even disappeared. Under the same Cd concentrations, root-tip cells of intercropped wheat showed much less density of electron particles, starch granules, and the damage to the nucleus and nuclear membrane by Cd.These results indicated that intercropping with Solanum nigrum L. reduced the Cd toxicity to wheat roots and decreased Cd uptake and accumulation in both the shoots and roots of the wheat.

Zinc and cadmium change the metabolic activities and vegetable cellulose degradation of Bacillus cellulasensis in vegetable soils.

Bacillus cellulasensis Zn-B isolated from vegetable soil was highly adaptable to Zinc (Zn) and Cadmium (Cd). Cd, but not Zn, adversely affected the total protein spectrum and functional groups of Bacillus cellulasensis Zn-B. Up to 31 metabolic pathways and 216 metabolites of Bacillus cellulasensis Zn-B were significantly changed by Zn and Cd (Zn&Cd). Some metabolic pathways and metabolites related to functional groups of sulfhydryl (-SH) and amine (-NH-) metabolism were enhanced by Zn&Cd addition. The cellulase activity of Bacillus cellulasensis Zn-B was up to 8.58 U mL-1, increased to 10.77 U mL-1 in Bacillus cellulasensis Zn-B + 300mg L-1 Zn, and maintained at 6.13 U mL-1 in Bacillus cellulasensis Zn-B + 50mg L-1 Cd. The vegetables' cellulose content was decreased by 25.05-52.37% and 40.28-70.70% under the action of Bacillus cellulasensis Zn-B and Bacillus cellulasensis Zn-B + 300mg L-1 Zn. Those results demonstrated that Zn could significantly enhance cellulase activity and biodegradability of Bacillus cellulasensis Zn-B to vegetable cellulose. Bacillus cellulasensis Zn-B can survive in vegetable soil accumulated with Zn&Cd. The tolerance concentration and adsorption capacity of Bacillus cellulasensis Zn-B to Zn were up to 300mg L-1 and 56.85%, indicating that Bacillus cellulasensis Zn-B acting as a thermostability biological agent had an essential advantage in accelerating the degradation of discarded vegetables by Zn and were beneficial to maintain organic matter content of vegetable soil.

The Expression of the StNRAMP2 Gene Determined the Accumulation of Cadmium in Different Tissues of Potato.

Cadmium (Cd) is a toxic metal that threatens human health when enriched in crops. NRAMPs are a family of natural macrophage proteins reported to play a key role in Cd transport in plants. In order to explore the gene regulation mechanism of potato under Cd stress and the role of NRAMPs family in it, this study analyzed the gene expression differences of two different Cd accumulation levels in potato after 7 days of 50 mg/kg Cd stress and screened out the key genes that may play a major role in the differential accumulation of Cd in different varieties. Additionally, StNRAMP2 was selected for verification. Further verification showed that the StNRAMP2 gene plays an important role in the accumulation of Cd in potato. Interestingly, silencing StNRAMP2 increased Cd accumulation in tubers but significantly decreased Cd accumulation in other sites, suggesting a critical role of StNRAMP2 in Cd uptake and transport in potatoes. To further confirm this conclusion, we performed heterologous expression experiments in which overexpression of StNRAMP2 gene in tomato resulted in a threefold increase in Cd content, which further confirmed the important role of StNRAMP2 in the process of Cd accumulation compared with wild-type plants. In addition, we found that the addition of Cd to the soil increased the activity of the plant antioxidant enzyme system, and silencing StNRAMP2 partially reversed this effect. This suggests that the StNRAMP2 gene plays an important role in plant stress tolerance, and future studies could further explore the role of this gene in other environmental stresses. In conclusion, the results of this study improve the understanding of the mechanism of Cd accumulation in potato and provide experimental basis for remediation of Cd pollution.

Comparative study of Cd addition effects on precipitation in different aluminium alloys

This work demonstrates that Cd microadditions can enhance the precipitation of age-hardening precipitates in 2xxx and 6xxx alloys as well as the dispersoid precipitation in 3xxx alloys, but have a minimal effect on the precipitation in 7xxx alloys. Experimental and theoretical methods are utilised to investigate the nucleation and precipitation of precipitates/dispersoids in Cd-containing Al alloys. The enhanced precipitation of θ′ and α-dispersoids in 2xxx and 3xxx alloys, respectively, are proposed to result from the heterogeneous nucleation on earlier-formed Cd-rich nanoparticles, while the enhanced precipitation of β′′ in 6xxx alloys is attributed to the increased number density of effective Mg-Si co-clusters due to the Cd incorporation. This investigation provides theoretical basis for the design of precipitation-strengthened Al alloys via microalloying.

Co-adsorption characteristics of antibiotics with different functional groups and cadmium combined contamination on activated carbon

Due to the diversity of functional groups of antibiotics, antibiotics are easy to complex with metals, thereby changing their migration and transformation behavior. The adsorption/complexation mechanism of three antibiotics co-adsorbed with Cd(Ⅱ) and systematic comparison were studied using Raman, FTIR, XPS and Materials Studio (norfloxacin (NOR), sulfamethazine (SMT) and tetracycline (TC)). We concluded that two NORs complexed with Cd(Ⅱ) through oxygen atoms from carboxylic acid and carbonyl in ketone group to form a six-membered ring chelate. The Cd(II)(NOR±)2+ showed a stronger adsorption coefficient than other forms of NOR, Cd(II)(NOR±)2+, NOR and Cd(Ⅱ) would compete the same permanent charge sites, thus exhibiting an inhibitory effect on NOR adsorption. Contrarily, one SMT molecule complexed with Cd(Ⅱ) through the N atom on pyrimidine ring and the -NH attached to the pyrimidine ring, forming an AC-Cd(Ⅱ)-SMT ternary complex on activated carbon (AC), and Cd(Ⅱ) acted as bridge. The bridging effect of Cd(Ⅱ) and multi-layer adsorption of SMT provided more adsorption sites for SMT, thus promoting the SMT adsorption. There was no complexation between TC and Cd(Ⅱ), and the addition of Cd(Ⅱ) had no significant effect on TC adsorption. The adsorption capacity of AC-Cd(Ⅱ)-SMT complex (107.4 mg·g−1) was stronger than NOR-Cd(Ⅱ) complex (40.2 mg·g−1), and the adsorption capacity of antibiotics was SMT>TC>NOR in all systems. The correlation analysis and molecular orbital calculation further supported the strong effect of complexation between Cd(Ⅱ) and antibiotics with different function groups on the adsorption, and the environmental behavior of system was jointly determined by complex structure and adsorption mechanism.

Effect of microplastics on dry matter content in Lactuca sativa L.

Plastics are commonly used in every field of life due to their ease of use and economics. If the plastic wastes are not disposed of properly, they form microplastics by breaking down into smaller particles with decomposition. Microplastics are chemical substances in polymer structure. They are difficult to dissolve in nature and require a long time. Microplastics, that spread to the environment in various ways, cause pollution and negatively affect organisms and ecosystems. &#x0D; This study aimed to determine the effects of microplastics and the combined impact of microplastics and Cd on dry matter content (the ratio of dry mass to fresh mass of an organ), which is the one of the major plant traits for plant growth, in lettuce (Lactuca sativa L.). Five experiment sets were designed by using Simila variety lettuce seedlings, including (1) control, (2) 1.5 % microplastic (3) 2.5 % microplastic, (4) 1.5 % microplastic and 200 ppm Cd solution and (5) 2.5 % microplastic and 200 ppm Cd solution added. The polyethylene mulch pieces (2,5 mm x 4 mm) were used as microplastics. Results showed that the polyethylene microplastic addition to the soil significantly reduced aboveground and belowground DMCs of lettuce seedlings. Concentration of the microplastics in the soil was also effective on DMC. The Cd addition to the soils, which contain microplastics, a bit increased the DMC.

Effect of limiting current density on corrosion performance of Ni–Mo, Ni–Cd and Ni–Mo–Cd alloy coatings

In this article an attempt was made to increase the corrosion resistance of Ni–Mo alloy coatings with the addition of small quantity of CdCl2 into its bath. The limiting of limiting current density (iL) of Ni in both Ni–Mo and Ni–Cd baths due to inherent induced and normal type of codeposition has been successfully alleviated by addition of 1 g/L of CdCl2. The advent of induced and normal type of codeposition of individual binary baths has been used to optimize the Ni content of the ternary deposit for better corrosion stability. The composition vs. current density plots of all coatings have been studied, and thereby optimal iL of Ni in all baths were assessed. The content of Mo was found to be decreased with the small addition of Cd to the bath. Results revealed that (Ni–Mo–Cd)6.0 Adm−2 coating showed better corrosion resistance by reducing iL of Ni, on addition of Cd+2 ions into the bath and was explained in the light of diffusion limited deposition of Ni+2 ions. The results were supported by SEM (scanning electron microscopy), XRD (X-ray diffraction) and AFM (atomic force microscopy) study of Ni–Mo, Ni–Cd and Ni–Mo–Cd coatings at optimal current densities.

Correlating fractography with mechanical properties of microalloyed 2219Al alloys under different thermo-mechanical conditions

ABSTRACT 2219Al alloys microalloyed with varying trace contents (0–0.1 wt.%) of Cd were cast, and subjected to standard sequential thermo-mechanical processes of rolling and age-hardening treatments. Uniaxial tensile and Charpy impact tests were performed, and fractured surfaces were studied under scanning electron microscope (SEM). Variations in tensile ductility and toughness with trace additions of Cd were reported under given processing conditions. Independent influences of Cd compositions, peak-ageing treatment and rolling were investigated to identify predominant fracture modes (ductile/fibrous, brittle/cleavage or mixed) of 2219Al alloys for the first time. Salient features and fracture mechanisms as exhibited from the fractographs were further correlated with microstructural evolution, mechanical ductility and toughness. Cast 2219Al alloy exhibited typically ductile fractographs, compared to moderate level of ductility after microalloying. Lower fracture strain and toughness of peak-aged alloys were accompanied with mixed mode of fracture surfaces. Rolling resulted in fractographs of mixed mode, however with higher ductility compared to peak-aged alloys. Impact testing resulted in failure at higher strain rate, exhibiting typically brittle fractographs, correlated with the impact toughness values. Present fractographic analysis provided a structure-property correlation, to validate the susceptibility of these alloys, to different modes of failure, subjected under various loading and thermo-mechanical treatments.