Different Amounts Of Cd Research Articles

Understanding the suitable alloying conditions for highly efficient Cu- and Mn-doped Zn1-xCdxS/ZnS core-shell quantum dots

Doping of alloyed colloidal quantum dots (QDs) has garnered significant attention for providing tunable and Stokes-shifted emission. By alloying the host semiconductor nanocrystals (NCs), their band gap can be tuned. With the specific addition of dopant ions, these NCs can emit tunable emissions within the visible spectrum. However, while doped and alloyed quantum dots (QDs) have shown promise for tunable emissions, their emission qualities have not been consistent across the spectrum. Here, we report the synthesis of high-quality Cu- and Mn-doped ZnxCd1-xS (x = 0–1) alloyed QDs by a colloidal non-injection method. In this study, we examined the effect of different dopant ions on the optical properties of similar alloyed nanocrystals. The deposition of a ZnS shell on these doped QDs significantly improves their quantum yield (QY), increasing it from 7.0 % to 50.0 % for Cu-doped QDs and from 30.0 % to 80.0 % for Mn-doped QDs. The Cu-doped QDs exhibit tunable emission from green to red across the visible spectrum by varying the Zn/Cd ratio, whereas the Mn-doped QDs show a fixed orange emission. Interestingly, the Cu-doped alloyed QDs show a contrasting trend in quantum yield (QY) compared to those of Mn-doped QDs when the amount of Cd in ZnCdS alloyed QDs is systematically changed. As the amount of Cd increases in the ZnCdS alloyed QDs, the Cu-doped QDs show both an increase in average lifetime and an increase in QY. In contrast, for the Mn-doped QDs, the decay lifetime values remain fairly constant for different amounts of Cd in the ZnCdS alloyed QDs, but the QY decreases as the amount of Cd increases. The results of this study may facilitate the design of optimal alloying combinations for Cu/Mn-doped QDs in optoelectronic applications.

The Use of Agricultural Residues of Vigna Peel in the Treatment of Environmental Pollution Resulting from Cadmium Ions by Adsorption Method

In this paper, vigna peel was used as a new way to get rid of Cd(II) from its aqueous solutions (VP). For this study, vigna peel (VP) was changed chemically with 25% by volume H2SO4 and ultrasonication at a frequency of 20 kHz to make a high-efficiency adsorbent. In this study, the material found was used to remove Cd(II) from the sample. The SEM and BET methods were used to figure out what the VP material was like. There were different amounts of Cd(II) (10–50 mg/L), pH (1–10), time (5–60 min), and VP dosages (50–1000 mg/50 ml). Maximum Cd(II) removal was found to be 98.6% at pH 5 with 50 mg/L of Cd(II) and 250 mg/50 ml of VP for 15 minutes. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models provided the best explanations for the equilibrium data.

Ameliorative Effects of Biochar for Cadmium Stress on Bean (Phaseolus vulgaris L.) Growth

In order to investigate the changes in the morphological and biochemical characteristics of bean plants in response to biochar treatment under cadmium (Cd) stress, a pot experiment was conducted in a greenhouse. Bean plants were subjected to different amounts of Cd (0, 100, 150 and 200 mg kg−1) and biochar applied at different doses (0, 2.5 and 5%). Under Cd stress, the growth and development of bean seedlings were remarkably inhibited, whereas the biochar treatment could effectively improve the heavy metal tolerance of bean seedlings. Cd stress caused an increase in the hydrogen peroxide (H2O2), malondialdehyde (MDA), proline and sucrose content, catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) activity of leaves. However, biochar treatments reduced the CAT, POD and SOD activity of bean seedlings. Growing beans on Cd medium led to a significant reduction in plant nutrient element content. However, biochar amendment to the soil elevated the plant nutrient element content compared to untreated soil. Cd content of the bean seedlings increased with increasing Cd doses. There was a sharp decrease in available concentration for Cd with the addition of biochar. In conclusion, biochar incorporation into the soil can alleviate the adverse impacts of Cd stress on the growth of bean seedlings.

Nitrogen Doped Carbon-Dot Embedded Poly(lactic acid-co-glycolic acid) Composite Films for Potential Use in Food Packing Industry and Wound Dressing

Here, nitrogen-doped carbon dots (N-doped CDs) were synthesized by the hydrothermal method embedded within poly(lactic acid-co-glycolic acid) ((PLGA)) films at different amounts. The N-doped CDs (or CD) that possess fluorescence properties also have antimicrobial properties against S. aureus and E. coli microorganisms, determined by the disc diffusion method with 19 ± 2 and 18 ± 1 mm zone diameters, respectively. The CD embedded PLGA films (CD@PLGA) with different CD contents revealed an increased fluorescence intensity with the increased amount of CD. Moreover, the antibacterial potency of 50% CD containing PLGA (50-CD@PLGA) films (by weight) against S. aureus and E. coli microorganisms was examined and the zone diameters were found to be 14 ± 1 and 13 ± 1 mm, respectively. In addition, CD release studies from different amounts of CD (2.5–50 by weight) containing composite films showed that 50-CD@PLGA film released 127 ± 16 mg/g CD dots, which is 38 ± 5% of the embedded CDs in about 12 days, suggesting their potential application in food packing and wound dressing. Moreover, all CD@PLGA films were found to be blood compatible via hemolysis and blood clotting index tests with <5% hemolysis and >90% blood clotting indices regardless of their CD content.

Effects of cutting frequency of tall fescue on cadmium form in soil and cadmium enrichment in the plant

AbstractCutting is a common practice for turfgrass culture and maintenance, and it may affect cadmium (Cd) uptake and enrichment due to the removal and regrowth of aboveground parts. The objective of this study was to determine how cutting frequency affects Cd form in the soil and its enrichment and distribution in clippings, stubble and roots. In this study, ‘K‐31’ tall fescue (Festuca elata L.) plants were grown in soils containing different amounts of Cd (0, 5, 25 and 50 mg kg−1) and cut at three different frequencies (no cutting, one cutting, two cuttings and five cuttings in two weeks). The cutting treatment caused a significant decrease in the soil pH, and it promoted Cd absorption by roots and Cd transfer to stubble. Increasing the cutting frequency increased acid‐soluble and reducible Cd content in soil, and the Cd content in the stubble and roots increased significantly and peaked at five cuttings. Cutting treatment exacerbated changes in plant ultrastructure under Cd stress as the chloroplasts of clippings swelled and the number of plastoglobuli in chloroplasts increased. Our study demonstrated that cutting frequency affects the conversion of Cd forms in the soil, promotes Cd absorption in roots, promotes Cd transport to stubble and exacerbates Cd stress on plants.

Exciton-phonon coupling in InP quantum dots with ZnS and (Zn,Cd)Se shells

InP-based colloidal quantum dots are promising for optoelectronic devices such as light-emitting diodes and lasers. Understanding and optimizing their emission process is of scientific interest and essential for large-scale applications. Here we present a study of the exciton recombination dynamics in InP QDs with various shells: ZnS, ZnSe, and (Zn,Cd)Se with different amounts of Cd (5, 9, 12%). Phonon energies extracted from Raman spectroscopy measurements at cryogenic temperatures (4--5 K) are compared with exciton emission peaks observed in fluorescence line narrowing spectra. This allowed us to determine the position of both the bright $F=\ifmmode\pm\else\textpm\fi{}1$ state and the lowest dark $F=\ifmmode\pm\else\textpm\fi{}2$ state. We could identify the phonon modes involved in the radiative recombination of the dark state and found that acoustic and optical phonons of both the core and the shell are involved in this process. The Cd content in the shell increases electron wave-function delocalization, and thereby enhances the exciton-phonon coupling through the Fr\ohlich interaction.

Cadmium decontamination through ball milling using an expandable clay mineral

Mechanochemical treatments have been widely used for the remediation of soils and sediments polluted by organic and inorganic pollutants. However, there has been still limited knowledge about the molecular mechanisms underlying the mechanochemical transformations responsible of heavy metals immobilization on clay minerals.In the present study, the ability of a dioctahedral smectite to retain cadmium (Cd) as induced by mechanochemical treatments was investigated. The smectite was ground with different amounts of Cd (from 0.3 to 5.2% w/w). Solid-state characterizations (XRF, XRD, XPS, FT-IR, NMR) as well as desorption isotherm experiments were carried out to understand the critical metal sorption mechanisms onto dioctahedral smectite occurring in mechanochemical interactions. The “entrapping efficiency” and the type of interaction between clay surfaces and cadmium were evaluated. Cd immobilization degree was assessed by extract analyses and expressed as leachable fraction of cations. Leaching was both performed with deionized water and 1 M MgCl2 solution. Spectroscopic analyses evidenced that long time grinding (24 h) allowed Cd sorption on two sites: Type I, exhibiting characteristic of an outer-sphere complex likely localized in the montmorillonite interlayers and coordinated by two water molecule shells, i.e. in an exchangeable position; Type II sites, where Cd was more tightly bound to the TOT layers, either onto broken edges via the new OHs formed during the mechanochemical treatments or onto montmorillonite surfaces likely bridged via a water molecule. Desorption isotherms also confirmed a two-adsorption site model. This information could be useful to understand, develop and manage new remediation technologies based on mechanochemical treatments.

Cd isotope fractionation during sulfide mineral weathering in the Fule Zn-Pb-Cd deposit, Yunnan Province, Southwest China

Zinc (Zn)-Lead (Pb) deposits are generally rich in cadmium (Cd), and the weathering of sulfide minerals in such deposits results in large releases of Cd into the environment. From an environmental and public health standpoint, understanding Cd sources and cycling is critical to identifying potential hazards to humans. In this study, the Cd isotope compositions (expressed as δ114/110Cd) of secondary minerals such as anglesite (−0.57±0.03‰; 2S.D.), granular smithsonite (0.04±0.14‰; 2S.D.), layered smithsonite (0.15±0.40‰; 2S.D.), hydrozincite (0.26±0.01‰; 2S.D.) and clay minerals (−0.01±0.06‰; 2S.D.) from the Fule Zn-Pb-Cd deposit, Southwest China, are investigated to better understand the Cd sources and cycling in this area.Combined with our previous study (Zhu et al., 2017), the work herein elucidates the patterns of Cd isotopic fractionation during the formation processes of such secondary minerals and traces the weathering of these minerals into the ecosystem. The δ114/110Cd values of secondary minerals exhibit the following decreasing trend: hydrozincite>large granular smithsonite>small granular smithsonite>anglesite. Although different amounts of Cd were lost during the formation of equally sized samples, no or minor variations in Cd isotopic composition were observed. However, significant isotopic differences were observed between different size fractions. These results demonstrate that the particle size of secondary minerals and weathering products of sulfide significantly influence Cd isotope composition and fractionation during natural weathering. This systematic fractionation provides an initial foundation for the use of Cd isotopes as environmental tracers in ecosystems and in the global Cd isotope budget.

Photosynthetic response and tolerance of three willow species to cadmium exposure in hydroponic culture

Three willow species (Salix alba, Salix matsudana and Salix nigra) were exposed to very high cadmium (Cd) concentrations in order to define some physiological traits related to high biomass production. Plants were grown hydroponically under semi-controlled conditions (greenhouse). It was assumed that leaves accumulate different amounts of Cd in relation to their age due to the specific occurrence of symptoms generated by Cd accumulation. The rate of photosynthesis and concentration of photosynthetic pigments in young and old leaves was correlated with biomass production in order to ascertain their significance as indicators of plant performance at sites contaminated with Cd. Changes in the photosynthetic parameters induced by treatments depended on the concentration of Cd in the nutrient solution, the species of willow and leaf age. Fv/Fm ratios were not considerably changed in treated plants, indicating preserved activity of PSII. According to results presented in this work, the Fv/Fm ratio was a less sensitive indicator of Cd stress in willows than the rate of photosynthesis and pigment concentration. High tolerance to applied treatments estimated on the basis of biomass production of S. nigra and S. matsudana irrespective of Cd concentration in the growth substrate might indicate their potential in the reclamation of Cd-contaminated sites.

Edge‐functionalized graphene nanoplatelets with polystyrene by atom transfer radical polymerization: grafting through carboxyl groups

AbstractThe surface modifier 3‐((4‐hydroxybutoxy)dimethylsilyl)propyl methacrylate (CD), which contains a double bond and a hydroxyl group, was synthesized through a coupling reaction of 1,4‐butanediol and (3‐methacryloxypropyl)dimethylchlorosilane. Subsequently, graphene oxide (GO) was functionalized with different amounts of CD from its edge carboxyl groups. Then, grafting through atom transfer radical polymerization of styrene in the presence of various amounts of the edge‐functionalized GO was carried out to evaluate the effect of graphene loading along with graft density. A peak at 3.8 ppm in the 1H NMR spectrum of CD associated with the methylene adjacent to the Si–O group indicated a successful coupling reaction. Attachment of CD on the edges of GO was evaluated using X‐ray photoelectron and Fourier transform infrared spectroscopies. Expansion of GO interlayer spacing by functionalization was evaluated using X‐ray diffraction. The ordered and disordered crystal structure of carbon was studied using Raman spectroscopy. The close ID/IG values for GO and various kinds of functionalized graphenes show the preserved graphitic crystallite size. Relaxation behaviour of polystyrene chains in the presence of graphene nanoplatelets and also the effect of graft content on chain confinement were studied using differential scanning calorimetry. High‐graft‐density nanocomposites show higher glass transition temperatures. Morphology of graphene nanoplatelets was studied using scanning electron and transmission electron microscopies. The flat and smooth morphology of graphene nanoplatelets is disturbed and also the transparency of the nanoplatelets decreases during the oxidation and functionalization processes. © 2014 Society of Chemical Industry

SORPTION AND DESORPTION KINETICS OF CADMIUM FROM SOILS: INFLUENCE OF PHOSPHATE

The mobility and availability of heavy metals is controlled by sorption-desorption characteristics of the soils. There is much literature available about the sorption characteristics of heavy metals by soils. However, the influence of ionic environments on the desorption kinetics of heavy metals, particularly Cd, have not been studied in detail. The present study reports the kinetic data of desorption of Cd from two soils, with contrasting Cd availability characteristics, using 1 M NH4Cl. The soils were preadsorbed with different amounts of Cd in the presence of monoammonium phosphate. The Cd was sorbed onto the soils almost instantaneously in the absence of phosphate, with >97% of the Cd added to the soils sorbed within the first 15 min of reaction time. The Freundlich parameter a, the sorption coefficient, which is related to the Cd sorption capacity, indicated that the phosphate retarded Cd sorption by both soils by at least one order of magnitude. The overall diffusion coefficient of Cd release from the Luseland soil by 1 M NH4Cl, obtained using the parabolic diffusion model for the desorption kinetics, was 1.62 to 10.1 times higher than that of the Jedburgh soil, depending on the initial amount of Cd preadsorbed. The lower the amount of initial Cd preadsorbed, the greater the difference in the rate of Cd released between the two soils. The presence of phosphate during Cd adsorption by the soils increased the amount of Cd released in the initial 30-min reaction period as well as the overall diffusion coefficients of Cd release. The kinetic data of Cd desorption reflect well the Cd availability index and grain Cd content of the durum wheat crops, Kyle and Arcola, grown in the two soils.

Desorption kinetics of cadmium from soils using M ammonium nitrate and M ammonium chloride

The bioavailability and, hence, potential toxicity of a trace metal ion in the soil depends on its concentration in the soil solution and on the soil's ability to release the trace metal ions from the solid phase to replenish those removed from the soil solution by plants. Voluminous literature is available on the sorption characteristics of heavy metals by soils. However, study of desorption of heavy metals, particularly cadmium (Cd) from soils has not received much attention. The present study reports the kinetic data of desorption of Cd by M ammonium nitrate (NH4NO3) and M ammonium chloride (NH4Cl) from the Luseland and Jedburgh soils of Saskatchewan, Canada, with contrasting Cd‐availability characteristics, preadsorbed with different amounts of Cd. The desorption kinetics were described best using the parabolic diffusion mathematical model. The overall diffusion coefficient of Cd release by M NH4Cl, obtained using the parabolic diffusion model for the desorption kinetics, from the Luseland soil was 2.5–14.8 times higher than that of the Jedburgh soil, depending on the initial amount of Cd preadsorbed. The lower the amount of initial Cd preadsorbed, the greater was the difference in the rate of Cd released between the two soils. The rate constant of Cd desorption by M NH4Cl from the Luseland soil was 14.8 times higher than that from the Jedburgh soil, when no Cd was preadsorbed onto the soil. The rate constants obtained from the desorption kinetics of the two soils reflect very well the Cd availability index and grain Cd content of the durum wheat crops, Kyle and Arcola grown in the two soils. The results highlight the importance of Cd desorption kinetics in elucidating the availability of Cd in the soils.

Procion Red MX-3B-Derived Poly(HEMA/EGDMA) Microspheres for Removal of Cadmium Ions

Poly(hydroxyethyl methacrylate/ethylene glycol dimethacrylate) [poly(HEMA/ EGDMA)]-Procion Red MX-3B microspheres were used for removal of Cd(II) ions from aqueous solutions containing different amounts of Cd(II) ions (5–60 ppm). Dye-derived microbeads carrying 8.95 μmol Procion Red MX-3B/g polymer were used in the adsorption-desorption of Cd(II) ions. High adsorption rates were observed at the beginning of adsorption and then equilibrium was achieved in about 5–10 min. The maximum adsorption of Cd(II) ions onto the Procion Red MX-3B-derived microspheres (i.e., by chelate formation of Cd(II) ions with dye molecules) was about 4.2 mg Cd(II) ions/g polymer, which was observed at pH 7.0. While non-specific adsorption onto the underived microspheres was 0.93 mg Cd(II) ions/g polymer. More than 96% of the adsorbed Cd(II) ions was desorbed in 15 min by using 0.1 M HNO3 as an desorption agent. The regenerability of the dye-derived microspheres was also sufficient.

Exposure of scorpionfish ( Scorpaena guttata) to cadmium: effects of acute and chronic exposures on the cytosolic distribution of cadmium, copper and zinc

Scorpionfish were exposed to sublethal levels of cadmium in seawater (0.1 to 20 mg/l) for 4 and 8 wk. Cytosols from liver, kidney, intestine and gill tissues from these fish were analyzed by Sephadex G-75 chromatography to determine the effects of chronic Cd exposure on detoxication by a medium-molecular-weight (3 000–20 000) metallothionein-containing (MT) pool and the potential for toxicity to enzymes in a high-molecular-weight (>62; 20 000) enzyme-containing (ENZ) pool. Examination of ENZ- and MT-Cd values from these chronic exposures revealed patterns different from those resulting from acute (4-day) exposure to similar or higher concentrations in a previous study (Brown et al., 1984). The relative order of sensitivity of tissues to Cd after chronic exposure was intestine >62; gill >62; kidney — liver, whereas the kidney was most affected after acute exposure. Further, while acute exposures appeared to result in an MT saturation-dependent ‘spillover’ of Cd into the ENZ pool, chronic exposures appeared to involve an equilibrium-dependent exchange of Cd between the ENZ and MT pools. Chronic exposure to 20 mg Cd/l resulted in much higher MT-Cd and lower ENZ-Cd values than acute exposure to 25 mg Cd/l in all tissues examined, indicating more resistance to Cd toxicity after chronic exposure. Increases in MT-Zn were often correlated with increases in MT-Cd. Significant correlations (positive and negative) were occasionally found between the ENZ-Cd and the ENZ-Cu and -Zn values. We conclude that biological impact cannot be predicted from whole tissue bioaccumulation data since much different amounts of Cd may be detoxicated depending upon whether the exposure has been acute or chronic. Biochemical detoxication and toxicity measurements also cannot predict such impacts unless the most sensitive tissue is examined.

The Effect of Cadmium on Indicator Bacteria in Sewage

The effect of cadmium (Cd) on the number of different faecal indicator bacteria in sewage, and on species composition of different indicator bacteria, was studied. Different amounts of Cd were added to aliquots of a sewage sample, and after 0, 4% and 24 h of Cd exposure at 20°C conforms, faecal coliforms, faecal streptococci and Clostridium perfringens were enumerated by the membrane filter method. The Cd-induced reduction in the number of coliforms and faecal coliforms during exposure was found to be greater than the decrease in the number of faecal streptococci. In the case of C. perfringens the Cd concentrations used produced no observable effect on the cell number. The addition of Cd changed the faecal coliforms and faecal streptococci density relationship. Escherichia coli seems to be more resistant to Cd than other coliforms and Streptococcus faecalis var. liquefaciens and Streptococcus durans more resistant to Cd than other faecal streptococci. No influence of Cd on gas production by faecal coliforms was observed. Faecal streptococci and C. perfringens seem to be better indicator bacteria than coliforms and faecal coliforms in evaluating the hygienic quality of Cd polluted sewage.

Bioavailability of Cd to Food crops in relation to heavy metal content of sludge-amended soil.

Results of greenhouse and laboratory experiments on factors influencing uptake and accumulation of Cd by economic crops are summarized.Tolerance to Cd is highly crop-specific. For example, 21 different economic crops were grown in pots filled with a calcareous soil treated with increasing amounts of Cd. Yields versus Cd addition rate relations showed yield reductions to occur with Cd sensitive plants (spinach, soybean, curlycress, and lettuce) at addition rates varying from 5 to 15 mug Cd/g soil, whereas tolerant crops (tomato, squash, cabbage, and rice) did not suffer a yield reduction when treated at rates less than 150 mug Cd/g soil. Nutrient solution experiments likewise revealed marked differences in growth of crops. Corn, turnip, beets, bean, and tomato plants grown in solution cultures containing 0.1 mug Cd/ml accumulated different amounts of Cd in leaf tissue depending upon crop species; leaf Cd concentrations ranged from a low of 9 mug Cd/g leaf for beans to 200 mug Cd/g leaf for beets. Large differences also occur with regard to distribution of Cd within the plant. Fruit and seed tissue contain less Cd than leaves. Experiments comparing the toxicity of Cd to Cu, Ni, and Zn in an acid soil +/- lime showed Cd to be the most phytotoxic. While interactive effects occur with regard to metal uptake and accumulation by plants, Cd uptake is essentially dependent upon the Cd concentration of the soil. Studies of chemical speciation of Cd in relation to Cd availability indicate that the free Cd(2+) concentration correlates better with Cd uptake than Cd total of the soil solution.

Uptake of Cadmium and Lead by a Rooted Aquatic Macrophyte (Elodea Canadensis)

The role of roots in the uptake of nonessential trace metals by aquatic macrophytes was investigated Elodea canadensis. Plants were grown in 2 lakes in which metal concentrations in the water differed. Specimens in each lake were anchored in either control sediment or in sediment contaminated with Cd and Pb. Plants grown in the same water but in sediment from different sources had significantly different concentrations of the 2 metals. Elodea samples rooted in sediments from the same source but grown in water with different levels of metals also accumulated significantly different amounts of Cd and Pb. Thus the importance of both sediment and the surrounding water as sources of metals for aquatic plants was demonstrated. Samples grown in water and sediment containing low levels of metals had minimal concentrations of 0.32 mg/g Cd and 5.2 mg/g Pb, while plants grown in metal—contaminated water and sediment accumulated up to 32.33 mg Cd/g and 160.9 mg Pb/g.