Inhibition of the liberation of arachidonic acid by cadmium ions in rabbit alveolar macrophages

The effects of CdCl₂ on the liberation of arachidonic acid (20∶4) from membrane phospholipids of A23187-stimulated rabbit alveolar macrophages and on the activity of phospholipase A₂ (PLA₂) in a cytosolic fraction were studied. Alveolar macrophages were prelabeled with [³H]arachidonic acid (20∶4) and then treated with A23187. This treatment resulted in a remarkable increase in the liberation of [³H]20∶4 from their phospholipids. Exposure of cells to Cd²⁺ inhibited the liberation of [³H]20∶4 in a dose-dependent manner. Liberation of [³H]20∶4 from cell lipids was calcium dependent and the inhibitory effect of Cd²⁺ competed with the stimulatory effect of Ca²⁺. When Ca²⁺ was removed from the incubation medium, Cd²⁺ did not influence the liberation of [³H]20∶4. Entry of⁴⁵Ca²⁺ into cells was enhanced by treatment of A23187. However, Cd²⁺ did not influence the cellular uptake of⁴⁵Ca²⁺. Treatment with A23187 markedly enhanced entry of¹⁰⁹Cd²⁺ into cells. The effect of Cd²⁺ on the activity of phospholipase A₂ was determined with 1-palmitoyl-2-[¹⁴C]arachidonoyl-sn-glycero-3-phosphocholine as substrate. Calcium-dependent activation of PLA₂ was observed and Cd²⁺ inhibited activation in a dose-dependent manner. These results suggest that exposure of alveolar macrophages to Cd²⁺ causes a reduction in the rate of liberation of 20∶4 from cell lipids, as a possible result of the inhibition of PLA₂ activity by Cd²⁺.     

Synthesis,characterization, and determination of genotoxic effect of a novel dimeric 8-hydroxyquinoline Cd(II) SCN complex

In this study, a Cd(II) complex was synthesized using 8-hydroxyquinoline and thiocyanate as the ligands and structurally characterized with the combination of FTIR, ¹H-NMR, ¹³C-NMR, UV–vis, and MS spectral data. Then, genotoxic effects of the prepared complex were investigated. Genotoxic properties of the dimeric 8-hydroxyquinolinthiocyanatoCd(II) [Cd₂(8Q)₂(SCN)₂] complex synthesized as drug raw material were analyzed in human peripheral blood lymphocytes. Concentrations of 1, 2, 4, 6, and 8?μg/mL [Cd₂(8Q)₂(SCN)₂] were used for 24 and 48 h durations. [Cd₂(8Q)₂(SCN)₂] significantly increased chromosomal aberrations (CAs) at 4, 6, and 8?μg/mL concentrations after a 24-?h period and 2 and 4?μg/mL after a 48-h period. [Cd₂(8Q)₂(SCN)₂] significantly decreased the mitotic index (MI) at all concentrations, both at 24 and 48?h. Micronuclei frequency (MN) was not affected by [Cd₂(8Q)₂(SCN)₂] treatment compared with the control. After application for a 48?h period, 6 and 8?μg/mL concentrations showed toxic effects both in chromosomal abnormality and in micronucleus tests. It also decreased the cytokinesis-block proliferation index (CBPI), but this result was statistically significant only at 6 and 8?μg/mL concentrations. In the comet assay (single-cell gel electrophoresis (SCGE)), significant increases in comet tail length, tail moment, and tail intensity were observed at all concentrations. [Cd₂(8Q)₂(SCN)₂] displays clastogenic effect in the concentrations used in human peripheral lymphocytes at chromosomal abnormality, micronucleus tests, and cytokinesis-block proliferation index parameters. Further studies should be conducted in other test systems to evaluate the complete genotoxic potential of [Cd₂(8Q)₂(SCN)₂].     

Application of novel metal organic framework,MIL-53(Fe) and its magnetic hybrid: For removal of pharmaceutical pollutant,doxycycline from aqueous solutions

As a pharmaceutical pollutant, doxycycline causes contamination when enters into the environment. In this research MIL-53(Fe), and its magnetic hybrid MIL-53(Fe)/Fe₃O₄ were synthesized and employed for removal of doxycycline from aqueous solutions. The adsorbents were characterized by XRD, SEM, BET, FTIR, EDAX, VSM and TG-DTG technique. The effect of different variables such as DOC concentration, pH, contacting time, and adsorbent dose on the removal efficiency was studied and under optimized conditions the adsorption capacity of 322 mgg⁻¹ was obtained. The adsorption process was kinetically fast and the equilibration was attained within 30 min. The used adsorbent was easily separated from the solution by applying external magnetic field. The regenerated adsorbent retained most of its initial capacity after six regeneration steps. The effect of ionic strength was studied and it was indicated that removal of doxycycline from salt-containing water with moderate ionic strengths was quite feasible. Langmuir, Freundlich, Tempkin and Dubinin–Redushkevich isotherms were employed to describe the nature of adsorption process. The sorption data was well interpreted by the Longmuir model.     

Mechanism of primary Cd2+-induced rat liver mitochondria dysfunction: discrete modes of Cd2+ action on calcium and thiol-dependent domains

We attempted to discern discrete sites of Cd²⁺ deleterious action on rat liver mitochondrial function. In particular, EGTA, ADP, and cyclosporin A (potent mitochondrial permeability transition antagonists) affected mainly Cd²⁺ -induced changes in resting state respiration, eliminating its stimulation in KCl medium, while dithiothreitol (DTT, a dithiol reductant) produced its effect both on Cd²⁺ activation of the basal respiration and Cd²⁺ depression of uncoupler-stimulated respiration, evoking its restoration. Substantial differences in DTT influence on mitochondrial respiration at low and high [Cd²⁺] were revealed, namely, an enhanced mitochondrial permeabilization in the presence of saturated [DTT] at high [Cd²⁺] took place. Besides, DTT only partially reversed Cd²⁺ -induced swelling in NH₄NO₃ medium when glutamate plus malate or succinate without rotenone was used. Contrarily, DTT produced complete reversal of the swelling of succinate-energized mitochondria when rotenone was present in the medium. In addition, in the presence of rotenone both Cd²⁺ -produced activation of the resting state respiration in KCl medium and Cd²⁺-induced swelling in sucrose medium of succinate-energized mitochondria were more sensitive to cyclosporin A than the same Cd²⁺ effects obtained on mitochondria oxidizing succinate (without rotenone) or glutamate plus malate. We have concluded that Cd²⁺, producing primary mitochondrial dysfunction, acts both as a thiol and Me²⁺ binding site reagent. Suppositions about possible localization of separate sites of direct Cd²⁺ effects on mitochondrial function were made.     

Calmodulin-mediated cadmium inhibition of phosphodiesterase activity,in vitro

Ion-stripped bovine brain calmodulin (CaM) binds 4 moles Cd²⁺ as well as 4 moles Ca²⁺ per mole protein, with similar affinity; in the presence of 1 mM Mg²⁺ the molar binding ratio of CaM for Ca²⁺ decreased to 3, the apparent K_0.5 for Ca²⁺ nearly doubled, but the binding characteristics of CaM for Cd²⁺ were not changed. Saturating concentrations Ca²⁺ did not affect the molar binding ratio of CaM for Cd²⁺, but increased the apparent K_0.5 for Cd²⁺; vice versa, saturating concentrations Cd²⁺ decreased the molar binding ratio for Ca²⁺ to 2 without affecting the apparent K_0.5 for Ca²⁺.CaM-independent phosphodiesterase (PDE) activity was inhibited at [Cd²⁺]>10^–5 M. Cd²⁺-CaM as well as Ca²⁺-CaM activated PDE. However, the Cd²⁺-CaM complex is less effective than the Ca²⁺-CaM complex in stimulating CaM-dependent enzyme activities. Cd²⁺ inhibits Ca²⁺- and CaM-dependent PDE in a competitive way. Introduction of Cd²⁺ in a medium containing Ca²⁺ and CaM may, therefore, result in a reduction of CaM-dependent enzyme stimulation.By its interference with Ca²⁺- and CaM- dependent PDE activity, Cd²⁺ could upset the catabolic pathway of cellular cyclic nucleotide metabolism.     

Cadmium sensitivity, uptake, subcellular distribution and thiol induction in a marine diatom: exposure to cadmium

The aims of this study were to (1) evaluate the changes in the Cd tolerance of a marine diatom after exposure under different Cd concentrations for various durations and (2) to explore the potential subcellular and biochemical mechanisms underlying these changes. The 72-h toxicity, short-term Cd uptake, subcellular Cd distribution, as well as the synthesis of phytochelatins (PCs) were measured in a marine diatom Thalassiosira nordenskioeldii after exposure to a range of free Cd ion concentrations ([Cd²⁺], 0.01-84 nM) for 1-15 days. Surprisingly, the diatoms did not acquire higher resistance to Cd after exposure; instead their sensitivity to Cd increased with a higher exposed [Cd²⁺] and a longer exposure period. The underlying mechanisms could be traced to the responses of Cd cellular accumulation and the intrinsic detoxification ability of the preconditioned diatoms. Generally, exposure to a higher [Cd²⁺] and for a longer period increased the Cd uptake rate, cellular accumulation, as well as the Cd concentration in metal-sensitive fraction (MSF) in these diatoms. In contrast, although PCs were induced by the environmental Cd stress (with PC₂ being the most affected), the increased intracellular Cd to PC-SH ratio implied that the PCs’ detoxification ability had reduced after Cd exposure. All these responses resulted in an elevated Cd sensitivity as exposed [Cd²⁺] and duration increased. This study shows that the physiological/biochemical and kinetic responses of phytoplankton upon metal exposure deserve further investigation.     

Cadmium‐induced Cytosolic Ca2+ Elevation and Subsequent Apoptosis in Renal Tubular Cells

Abstract: Cadmium (Cd²⁺) is an industrial and environmental metal. The effect of Cd²⁺ on intracellular free‐Ca²⁺ levels ([Ca²⁺]_i) and viability in Madin Darby canine kidney cells was explored. Cd²⁺increased [Ca²⁺]_i in a concentration‐dependent manner with an EC₅₀ of 85 µM. Cd²⁺‐induced Mn²⁺ entry demonstrated Ca²⁺ influx. Removal of extracellular Ca²⁺ decreased the [Ca²⁺]_i signal by 60%. The [Ca²⁺]_i signal was inhibited by La³⁺ but not by L‐type Ca²⁺ channel blockers. In Ca²⁺‐free medium, Cd²⁺‐induced [Ca²⁺]_i signal was abolished by pre‐treatment with 1 µM thapsigargin (an endoplasmic reticulum Ca²⁺pump inhibitor) and 2 µM carbonylcyanide m‐chlorophenylhydrazone (CCCP; a mitochondrial uncoupler). Cd²⁺‐induced Ca²⁺ release was not altered by inhibition of phospholipase C. At concentrations between 10 and 100 µM, Cd²⁺killed cells in a concentration‐dependent manner. The cytotoxic effect of 100 µM Cd²⁺was reversed by pre‐chelating cytosolic Ca²⁺with BAPTA. Cd²⁺‐induced apoptosis was demonstrated by propidium iodide. Collectively, this study shows that Cd²⁺ induced a [Ca²⁺]_i increase in Madin Darby canine kidney cells via evoking Ca²⁺ entry through non‐selective Ca²⁺ channels, and releasing stored Ca²⁺ from endoplasmic reticulum and mitochondria in a phospholipase C‐independent manner.     

Effect of CH3HgCl and several transition metals on the dopamine neuronal carrier; peculiar behaviour of Zn2+

CH₃Hg⁺ and metal ions inhibited the specific binding of (1-[2-(diphenylmethoxy)ethyl]-4-(3-phenyl-2-[1-³H]propenyl) piperazine) ([³H]GBR 12783) to the dopamine neuronal carrier present in membranes from rat striatum with a general rank order of potency CH₃Hg⁺ > Cu²⁺ > Cd²⁺ > Zn²⁺ > Ni²⁺ = Mn²⁺ = Co²⁺, suggesting that -SH groups are chiefly involved in this inhibition. Five millimolar dithiothreitol reversed the rather stable block of the specific binding produced by Cd²⁺ or Zn²⁺. An increase in the concentration of Na⁺, or addition of either K⁺ or Ca²⁺ reduced the inhibitory effects of metal cations, except Cu²⁺. Zn²⁺ (3 μM) reduced the inhibitory potency of Cd²⁺ on the binding but was ineffective against CH₃Hg⁺ and Cu²⁺. Zn²⁺ at 0.3 to 10 μM significantly enhanced the specific binding of [³H]GBR 12783 and [³H]cocaine by 42 to 146%. Zn²⁺ (3 μM) increased the affinity of all pure uptake inhibitors tested and of the majority of the substrates for the [³H]GBR 12783 binding site. Dissociation experiments revealed that Zn²⁺ both inhibited and enhanced the [³H]GBR 12783 binding by recognizing amino acids located close to or in the radioligand binding site. Micromolar concentrations of Zn²⁺ noncompetitively blocked the [³H]dopamine uptake but they did not modify the block of the transport provoked by pure uptake inhibitors. These findings suggest that Na⁺, K⁺, Ca²⁺ and metal ions could recognize some -SH groups located in the [³H]GBR 12783 binding site; low concentrations of Zn²⁺ could allow a protection of these -SH groups.     

Biphasic effect of cadmium ions on the secretion of leukotriene B4 in rabbit alveolar macrophages

 One major role of alveolar macrophages is the production of eicosanoids, which modulate immune and inflammatory processes in the lung. In this study, the effects were investigated of cadmium ions on the secretion of leukotriene (LT)B₄ and prostaglandin (PG)E₂, predominant products of lipoxygenase and cyclooxygenase, respectively. Cd²⁺ had an inhibitory effect on the secretion of LTB₄ and PGE₂ in response to A23187 stimulation at concentrations >3× 10^-5 M. This effect can be explained by the inhibition of arachidonic acid (20 : 4) liberation from membrane phospholipids by Cd²⁺, because Cd²⁺ inhibits both [³H]arachidonic acid (20 : 4) liberation from [³H]20 : 4-prelabeled macrophages and the cytosolic phospholipase A₂ activity. At concentrations <3×10^-5 M, Cd²⁺ had no effect on PGE₂ secretion but showed an augmentation of LTB₄ secretion. In vitro study using macrophage lysate showed enhanced LTB₄ synthesis from arachidonic acid by Cd²⁺, which could be responsible for the augmentation of LTB₄ secretion in cells. These results indicate that Cd²⁺ may increase inflammation by increasing LTB₄ production in lung. Received: 13 February 1996/Accepted: 23 April 1996     

Metallothionein accumulation in response to cadmium in a clonal rat liver cell line

RLC cells, a clonal line of cells derived from rat liver, accumulate ¹⁰⁹Cd in a unique bound form in response to exposure to Cd²⁺. Cadmium administration also causes increased incorporation of [³⁵S]cystine into a chromatographically distinct macromolecule. The ¹⁰⁹Cd-binding activity and the macromolecule preferentially labeled by [³⁵S]cystine cochromatograph both on gel filtration and ion exchange columns. In addition, the Cd²⁺ responsive [³H]cystine-labeled moiety of RLC cells cochromatographs in both systems with rat liver [³⁵S]cystine metallothionein labeled in response to Cd²⁺ challenge in vivo. These data suggest that RLC cells are able to accumulate authentic metallothionein in culture in response to Cd²⁺ challenge. Time course and concentration data for metallothionein accumulation and labeling with ¹⁰⁹Cd and [³⁵S]cystine are presented. RLC cells in culture appear to be able to accumulate Cd²⁺ into metallothionein at a rate comparable to rat liver tissue in vivo when both systems are maximally activated.     

Copper scavenging efficiency of adsorbents prepared from Raphia hookeri fruit waste

Low cost adsorbents prepared from the epicarp of Raphia hookeri fruit were used for the removal of copper (II) ion from aqueous solution. The effects of operational parameters such as pH, concentration and contact time, dosage as well as interference of other ions were studied. Optimum pH for raw and modified biomass were 5.0 and 5.5 with percentage removal of 75.08% and 95.62% respectively. Concentration of competing ions greatly reduced Cu²⁺ removal with both adsorbents while agitation speed had negligible effect on Cu²⁺ uptake. Adsorbents surfaces were activated as temperature increased thus enhancing adsorbent adsorption capacity at high temperature. Adsorption kinetic data fitted best into the pseudo second order model while the thermodynamics studies confirmed adsorption spontaneity and feasibility. The Freundlich adsorption isotherm best described the adsorption process and the Langmuir maximum monolayer adsorption capacity for the raw (RHE) and acid treated (ARHE) biomass were 81.97 and 103.09 mg/g respectively. Chemisorption predominate the Cu²⁺-ARHE system hence desorption efficiency was obtained to be 72.65% with CH₃COOH as eluent.     

From green biowaste to water treatment applications: Utilization of modified new biochar for the efficient removal of ciprofloxacin

Water pollution caused by antibiotics is a serious environmental problem in recent years. Using biochar to remove such pharmaceutical pollutants has recently emerged as a promising option. After H₃PO₄ modification, a new waste-based biochar (MPCWSB500) from sour cherry stalk was successfully synthesized to remove ciprofloxacin (CFX) from aquatic media, and modification of feedstock has significantly improved the adsorption capacity of biochar. MPCWSB500 is suitable for both batch and continuous treatment systems. The CFX sorption was systematically studied using various kinetics and isotherm models. The surface characteristics of the modified biochar and the possible CFX?biochar interactions were investigated by BET, FT?IR, and SEM?EDX analysis. Short operation time, high sorption capacity (410.06 mg g^?1), and nearly 100% removal efficiency were recorded as significant findings at optimum experimental conditions (pH: 6.3, contact time: 40 min, MPCWSB500 dose: 15 mg). Furthermore, the modified biochar exhibited more than 95% CFX removal efficiency in continuous mode at all flow rates (1–10 mL min^?1). Its sorption performance was minimally affected by the presence of Cl^?, K⁺, Na⁺, and NO₃^? ions in the adsorption medium. In addition, up to 5 sorption-desorption cycles, biochar regeneration and recycling produced satisfactory results. The proposed biochar was also successfully used to remove CFX from simulated hospital wastewater and synthetic urine samples. These features are all important advantages for its real applications. Overall, our research offers a practical approach for removing CFX from the polluted aquatic environment.     

The effect of salinity on cadmium toxicity to the estuarine mysid Mysidopsis bahia: role of chemical speciation

The effect of salinity on the toxicity of cadmium to the bay mysid, Mysidopsis bahia Molenock, was studied. When toxicity was expressed in terms of free cadmium ion (Cd²⁺) rather than total cadmium (Cd_T), CdCl⁺ or CdCl₂ only a slight salinity effect was apparent, suggesting that Cd²⁺ is the primary toxic species. Mysids were more tolerant of Cd²⁺ at an intermediate salinity of 22‰ and less tolerant at low and high salinity extremes (6 and 38‰). Alteration of cadmium speciation by use of an artificial ligand, nitrilotriacetic acid (NTA), over a range of salinities (14–34‰) produced conflicting results. Toxicity of Cd²⁺ was independent of Cd_T concentration at a given salinity but increased with increasing salinity and/or NTA concentration and was determined to be the result of salinity—Cd²⁺ and NTA-Cd²⁺ interactions. Possible mechanisms of the salinity effect and NTA interaction with cadmium toxicity are discussed.     

Defluoridation of water using adsorbent derived from the Labeo rohita (rohu) fish scales waste: Optimization,isotherms, kinetics,and thermodynamic study

Fluoride ions have more affinity towards chitosan material. Fish scales waste is chitosan material generated in abundance in fish markets with virtually no value. The present research attempts to convert this waste to useful adsorbent which can remove fluoride from water. A novel adsorbent is thus developed from the Labeo rohita (rohu) fish scales waste giving thermal treatment for removal of fluoride from water using the batch study of adsorption. Taguchi optimization approach with L₁₆ orthogonal array was adopted to optimize the process parameters for achieving the maximum removal of fluoride. Using ANOM, pH 3; initial F^? concentration 5 mg.L^?1; mixing time 90 min; adsorbent dose 8 g.L^?1 and temperature 303 ^OK were obtained as optimum values providing a maximum fluoride reduction of 93.32%. Adopting ANOVA, the percentage contribution of each process parameter in descending order of sequence is initial F^? concentration 72.44%> pH 20.61% > temperature 2.96% > adsorbent dose 2.45% > contact time 1.55%. The fluoride sorption onto fish scales adsorbent was best fitted with the pseudo-second-order kinetic model and follows the Freundlich isotherm (K_F = 0.865, 1/n = 0.407) model. Thermodynamic parameters (ΔS = ?6.32 J mol^?1.K^?1, and ΔH = ?2.02 kJ mol^?1) suggested a spontaneous, exothermic nature of adsorption and indicates a physiosorption mechanism on a heterogeneous material. SEM and FTIR analysis for surface morphology showed the presence of hydroxyl functional groups is responsible for fluoride sorption. In the regeneration studies, the F ^– exhausted adsorbent was eluted with 0.1 N NaOH and rinsed with distilled water to prepare the adsorbent for the next cycle. The study indicates the removal of fluoride from water onto fish scales adsorbent is quite feasible, cost-effective, recyclable, and better utilization of locally available waste material into useful adsorbent for defluoridation of water.     

Effects of Divalent Cations on Adenosine Agonist Binding to A1 Receptors and Non-A1/Non-A2 Sites in Rat Cerebral Cortex

Abstract: In the present study results are reported concerning the effects of several divalent cations on the binding characteristics of [³H]-cyclohexyladenosine on A1 adenosine receptors and of [³H]-N-ethylcarboxamidoadenosine on non-A1/non-A2 sites in membranes from cerebral cortex of the rat. The [³H]-cyclohexyladenosine binding to A1 receptors was dose-dependently increased by Mn²⁺, Co²⁺, Ca²⁺. The binding characteristics of the agonist were differently affected by Ca²⁺/Mn²⁺ and Mg²⁺. Ca² and Mn²⁺ increased the B_max value without any change in K_d, whereas Mg²⁺ decreased the K_d value without changing the B_max. In the presence of Ca²⁺ and Mg²⁺ the K_d value was similar to that obtained in the presence of Mg²⁺, whereas the B_max value was similar to the apparent number of binding sites calculated in the presence of Ca²⁺. The cations, Cu²⁺, Cd²⁺, Zn²⁺, decreased the Al binding with IC₅₀, values of 19.6 μM, 39.2 μM and 103.9 μM, respectively. The binding characteristics of [³H]-N-ethylcarboxamidoadenosine to non-A1/non-A2 sites were affected by Ca²⁺, Mn²⁺, Co²⁺ and Mg²⁺ in the opposite manner to A1 receptors. They decreased the binding with IC₅₀ values of 20.1 mM, 22.8 mM, 93.0 mM and 18.1 mM, respectively. This occurs through an enhancement in K_d, values without changes in the number of binding sites. The findings on A1 receptor and non-A1/non-A2 binding site, taken together, suggest that cations could also exert a modulatory action via specific interactions with divalent cation binding sites on the receptor molecule.     

Nickel adsorption from aqueous solution using lemon peel biomass chemically modified with TiO2 nanoparticles

Adsorption technique has attracted considerable attention as a promising alternative for reducing heavy metal ions in water sources. This work is focused on the adsorption of nickel ions using lemon peel biomass chemically modified with titanium dioxide (TiO₂) nanoparticles through siloxane bonds. The biomass was characterized by FT-IR and compositional analyses to identify functional groups and elemental composition. From these measurements, it was observed peaks at 1741, 1328, and 1229 cm^?1, characteristics of CO, C–O, and C–H stretching bands, respectively. These organic bonds can be related to the existence of cellulose, lignin, and pectin biopolymers, which are present in the lemon peel biomass, as observed from the compositional analyses. After grafting TiO₂ nanoparticles onto lemon peel biomass surface, it was observed from FTIR the presence of vibrational bands at 1524, 1054, and 943 cm^?1, characteristics of –Ti-O-C, –Si-O-Si, and –Ti-O-Si functional groups. Additionally, the morphology and elemental composition of the lemon peel biomass modified with the titanium dioxide (TiO₂) nanoparticles were determined by SEM microscope, observing the presence of C, O, Ti, and Si atoms from the EDS mapping. Batch adsorption experiments were carried out to determine the effect of pH and biomass particle size on adsorption of Ni (II) ions from aqueous solution. From these experiments, maximum adsorption of Ni (II) ions of 78 ± 0.2% was obtained at pH 6.0, while no significant effects were observed for biomass particle size. Furthermore, the modification of biomass with TiO₂ nanoparticles increased up to 90 ± 0.1% the Ni (II) ions adsorption, suggesting the potential of the biomass modified with metal oxide nanoparticles for removal of heavy metal ions.     

Relationships between subcellular distributions of cadmium and perturbations in reproduction in the polychaete Neanthes arenaceodentata

The accumulation and subcellular distribution of Cd in the polychaete worm, Neanthes arenaceodentata, were examined following an eleven-week period of exposure to a range of free cadmium ion activities, [Cd²⁺]. The accumulation of Cd in N. arenaceodentata was directly proportional to [Cd²⁺] in seawater at lower concentrations (10⁻¹² M to 10⁻¹⁰ M) but deviated from proportionality at higher concentrations (10⁻⁹ M and 10⁻⁸ M). This deviation in proportionality at higher [Cd²⁺] was attributable to a relative increase in the concentration of metal associated with the metallothionein and the very low molecular weight metal-ligand pools of the cytosol.Reproductive potential was also monitored in these organisms to examine the ecological significance of Cd accumulation and shifts in its subcellular distribution. Perturbations in reproduction were observed at 10⁻⁸ M [Cd²⁺] which coincided with the deviation in proportionality of Cd accumulation and increased accumulation of Cd in the cytosol.     

Preparation and characterization of a novel functionalized agricultural waste-based adsorbent for Cu2+ removal: Evaluation of adsorption performance using response surface methodology

In this study, it was aimed to the improvement of adsorption capability with a novel modification method based on increasing surface activity of flaxseed waste (FW), an agricultural waste product, and the investigation of its usability as an effective adsorbent for Cu²⁺ removal. The modification method involves functionalization of FW with iron by adding FeCl₃ to medium in presence of N, N-Dimethyl-formamide, poly (N-vinyl-pyrrolidone), and hexamethylenetetramine. The effect of parameters was investigated by conventional univariate analysis. In addition, Response Surface Methodology (RSM) based on multivariate analysis was used to improve the performance of Cu²⁺ adsorption onto iron-modified flaxseed waste (M ? FW). Cu²⁺ removal efficiency was achieved as 91.46% ± 2.34 (N = 2) at an equilibrium time of only 15 min under determined optimum conditions as Co: 75 ppm, pH: 4.7, and m: 0.23 g. RSM was successfully applied for the prediction of adsorption. Adsorption nature was as a single-layer adsorption with a maximum adsorption capacity (Q_max) of 7.64 mg/g. The adsorption mechanism, determined to be chemically controlled, an exothermic and non-spontaneous process. Furthermore, pH-dependent adsorption showed that electrostatic interactions between M ? FW and Cu²⁺ ions play an important role in adsorption mechanism. The results of characterization studies showed that a large surface area was provided with increased porosity of structure and desired changes occurred in target functional structures with modification. Moreover, modification and reusability of M ? FW were evaluated in terms of overall sustainability and waste management. The results indicated that M ? FW has potential for usability to remove heavy metals like Cu²⁺ in environmental remediation applications.     

Enhancement of CO2 adsorption on natural zeolite,modified clinoptilolite with cations,amines and ionic liquids

The modification of clinoptilolite as a natural zeolite via a simple route was carried out for CO₂ adsorption. Cation exchange with Li⁺, Mg^2+, and Ca²⁺, amine modification using monoethanolamine (MEA), triethanolamine (TEA) and hexyl amine, and ionic liquid modification using [bmim]X (X = PF₆?, NO₃?, Br?, Cl?, and bmim = 1-Butyl-3-methylimidazolium) were performed in a different amount of the modifiers. The samples were characterized by several methods (XRD, FT-IR, BET, and SEM), and adsorbed CO₂ was evaluated utilizing adsorption isotherm at a wide range of pressure. The results showed enhancement in CO₂ adsorption capacity for all the samples and 4.18, 3.58, and 4.35 times increase in CO₂ adsorption were obtained where clinoptilolite/Li⁺, clinoptilolite/2% MEA and clinoptilolite/5% [bmim]PF₆ were used as adsorbent at 4 bar pressure of CO₂, respectively.