Heavy Metal Ions Cd Research Articles

Dechlorination of Hexachlorobenzene by Ni/Fe Bimetallic Nanoparticles and the Influence of Co-Existing Heavy Metal Ions

Hexachlorobenzene (HCB) is one of the most persistent environmental pollutants of global concern. Ni/Fe nanoparticles, with their small particle size, large surface area, and high reactivity, are a promising candidate for HCB degradation. In this work, we investigated the kinetics and products of the dechlorination of HCB by Ni/Fe nanoparticles and how the presence of heavy metal ions Cd(Ⅱ) and Zn(Ⅱ) influences the reaction. It is found that 400 μg/L HCB can be rapidly removed by 7.5 g/L Ni/Fe nanoparticles and the removal percentage reaches 99% in 48 h. The removal is facilitated by adsorption and sequential dechlorination of HCB, producing PCB, 1,2,3,4-TeCB, and 1,2,3-TCB as the main products, with 1,2,3,5/1,2,4,5-TeCB, 1,2,4-TCB, and 1,2-DCB as the minor products. The addition of heavy metal ions Cd(Ⅱ) and Zn(Ⅱ) does not significantly affect the removal rate of HCB but hinders the adsorption and degradation of the byproducts through competitive adsorption. Additionally, the concentration of both Cd(Ⅱ) and Zn(Ⅱ) decreases rapidly and achieves over 98% removal in 4 h. Our study reveals that Ni/Fe nanoparticles can remove HCB and heavy metals Cd(Ⅱ) and Zn(Ⅱ) concurrently, with the extent of HCB dechlorination reduced compared to that without heavy metal. These findings may inform the application of Ni/Fe nanoparticles in the treatment of water bodies and soil contaminated by both halogenated aromatics and heavy metal.

Fabrication of a polyoxometalate-based metal-organic compound and its derivative for enhanced photocatalytic, electrocatalytic, and electrochemical sensing properties

A novel polyoxometalate-based metal-organic compound (POMOC), namely [Ag(3-pna)2(H2PW12O40)]n (compound 1, where 3-pna = N-(pyridine-3-yl)nicotinamide), had been successfully synthesized and structurally characterized. The photocatalytic performance of compound 1 for the degradation of gentian violet (GV) and methylene blue (MB) was investigated in detail, which exhibited good cyclic stability as a photocatalyst. In addition, cyclic voltammetry technology was used to verify that compound 1 exhibited excellent electrocatalytic performance towards KBrO3 and H2O2. To improve the degradation of organic dyes and electrochemical sensing performance, a negatively charged oxygen vacancy metal oxide compound 1@C was prepared via pyrolysis using compound 1 as a precursor. Compound 1@C was investigated as an adsorbent, and was found to effectively remove MB and GV from wastewater, with adsorption rates of 824.36 mg/g and 957.02 mg/g, respectively. The performance of compound 1@C/glassy carbon electrode as an electrochemical sensor was studied using differential pulse dissolution voltammetry (DPV). This method proved effective in detecting heavy metal ions Cd2+ and Pb2+ in wastewater with the limits of detection as 4.65 and 1.69 μg/L, respectively. Compound 1@C/GCE showed good anti-interference capabilities and stability in detecting heavy metal ions in wastewater.

Hydrogen-bond organic-framework-based electrochemical sensor for highly sensitive determination of trace cadmium ions in environmental and e-cigarette samples

BackgroundThe heavy metal ion Cd2+ is acutely toxic, and excessive concentrations can have adverse effects on human production and life, and even lead to significant public health risks and environmental impacts. There are several mature non-electrochemical methods for heavy metal detection, but these methods are characterized by high cost, which makes it difficult to be applied to the field for timely detection. Therefore, it is necessary to prepare a new electrochemical sensor that is environmentally friendly and capable of detecting Cd2+ in the environment quickly, easily and sensitively. ResultsIn this study, hydrogen-bonded organic frameworks (HOFs) were synthesized by a simple hydrothermal reaction. The prepared materials consisted of only C, N and O and had a thin lamellar structure. The HOFs were integrated into a novel electrochemical sensor to achieve accurate detection of Cd2+ ions in real aqueous environments by square wave anodic dissolution voltammetry. The sensor has a wide linear range and a detection limit as low as 0.13 μg/L. Several real water samples, such as tap water, lake water, and e-cigarette digest, were analyzed to simulate the working environment of the sensor, and the results showed that the recoveries of Cd2+ ranged from 95.75 % to 101.2 %. SignificanceWe pioneered the detection of heavy metal ions Cd2+ in e-cigarette digestate samples with the innovative use of HOFs as the sensor material, which demonstrated the potential application in electrochemical sensing with extremely low background current value and high sensitivity, providing new ideas for environmental monitoring and public health control.

Electrochemical Detection of Cd2+, Pb2+, Cu2+ and Hg2+ with Sensors Based on Carbonaceous Nanomaterials and Fe3O4 Nanoparticles.

Two electrochemical sensors were developed in this study, with their preparations using two nanomaterials with remarkable properties, namely, carbon nanofibers (CNF) modified with Fe3O4 nanoparticles and multilayer carbon nanotubes (MWCNT) modified with Fe3O4 nanoparticles. The modified screen-printed electrodes (SPE) were thus named SPE/Fe3O4-CNF and SPE/Fe3O4-MWCNT and were used for the simultaneous detection of heavy metals (Cd2+, Pb2+, Cu2+ and Hg2+). The sensors have been spectrometrically and electrochemically characterized. The limits of detection of the SPE/Fe3O4-CNF sensor were 0.0615 μM, 0.0154 μM, 0.0320 μM and 0.0148 μM for Cd2+, Pb2+, Cu2+ and Hg2+, respectively, and 0.2719 μM, 0.3187 μM, 1.0436 μM and 0.9076 μM in the case of the SPE/ Fe3O4-MWCNT sensor (following optimization of the working parameters). Due to the modifying material, the results showed superior performance for the SPE/Fe3O4-CNF sensor, with extended linearity ranges and detection limits in the nanomolar range, compared to those of the SPE/Fe3O4-MWCNT sensor. For the quantification of heavy metal ions Cd2+, Pb2+, Cu2+ and Hg2+ with the SPE/Fe3O4-CNF sensor from real samples, the standard addition method was used because the values obtained for the recovery tests were good. The analysis of surface water samples from the Danube River has shown that the obtained values are significantly lower than the maximum limits allowed according to the quality standards specified by the United States Environmental Protection Agency (USEPA) and those of the World Health Organization (WHO). This research provides a complementary method based on electrochemical sensors for in situ monitoring of surface water quality, representing a useful tool in environmental studies.

Evaluating the Potential of Multi-Walled Carbon Nanotube-Modified Clay as a Landfill Liner Material.

In this paper, the feasibility of multi-walled carbon nanotube (MWCNT)-modified clay as a landfill liner material is investigated. Experiments were conducted on the modified clay with 0.5%, 1%, and 2% MWCNTs. The effects of the MWCNTs on the compaction characteristics, permeability coefficient, stress-strain curve, peak deviation stress, shear strength parameters (internal friction angle and cohesion), microstructures, and adsorption performance of the clay were analyzed. The results showed that the optimum moisture content (OMC) increased from 16.15% to 18.89%, and the maximum dry density (MDD) decreased from 1.79 g/cm3 to 1.72 g/cm3 with the increase in MWCNTs. The permeability coefficients firstly fell and then gradually rose as the MWCNTs increased; the minimum permeability coefficient was 8.62 × 10-9 cm/s. The MWCNTs can also effectively increase the peak deviation stress of the clay, and at the maximum level, the peak deviation stress was increased by 286%. SEM images were processed using the Pore and Crack Analysis System (PCAS), and the results showed that the appropriate amount of MWCNTs could fill the pores and strengthen the clay structure. The effect of the MWCNT-modified clay on the adsorption performance of common heavy metal ions Cd2+, Mn2+ and Cu2+ in landfill leachate was analyzed by batch adsorption tests. The maximum adsorption capacities (Qmax) of Cu2+, Cd2+ and Mn2+ in the 2% MWCNT-modified clay were, respectively, 41.67 mg/g, 18.69 mg/g, and 4.97 mg/g. Compared with the clay samples without MWCNTs, the adsorption properties of Cu2+, Cd2+, and Mn2+ were increased by 228%, 124%, and 202%, respectively. Overall, the results suggest that MWCNT-modified clays have the potential to be suitable barrier materials for the construction of landfills.

First-principle study on the stability of Cd passivates in soil

The stable existence of heavy metals in soil under natural conditions is the core issue in heavy metal pollution solidification and remediation technology. However, the existing research is limited to soil passivation tests of different materials or biochar adsorption tests and cannot reveal the internal mechanism of functional groups of different compounds in soil passivation. This paper takes the common heavy metal ion Cd2+ as an example to analyze the stability of the combination of heavy metal ions and common ion groups in soil. The stability and existing form of Cd are analyzed by using first-principle calculations, and the free energy, band structure, and partial density of states of CdCO3, CdSO4, CdCl2, and CdSiO3 are computed. The stability of Cd binding to common anions in soil is determined. Results show the descending order of structural stability of cadmium compounds is CdSiO3, CdSO4, CdCO3, and CdCl2. SO42− and SiO32− can be used as preferred functional groups for cadmium pollution passivation. Anhydrous sodium sulfate and sodium silicate are promising passivators.

Graphene Quantum Dots Doped with Sulfur and Nitrogen as Versatile Electrochemical Sensors for Heavy Metal Ions Cd(II), Pb(II), and Hg(II)

A sulfur co-doped nitrogen-graphene quantum dot (S,N-GQD) was synthesized from polyaniline using sulfuric acid as an acid catalyst and S-doping agent. Thus, through a simple hydrothermal synthesis method, we could achieve nanosized (∼4 nm) highly crystalline and aromatic S,N-GQDs. The S,N-GQDs, for the first time, exhibited simultaneous sensing toward three of the top 10 toxic metal ions: Cd(II), Pb(II), and Hg(II) with highly sharp peaks and adequate peak-to-peak separation, while the control N-GQD (no S co-doping) exhibited current response only for Cd(II) and the current response of Cd(II) on S,N-GQD was ∼7-fold higher than that of on N-GQD. The detection limit values were lowest hitherto for Cd(II), Pb(II), and Hg(II) on S,N-GQD with 1, 10, and 1 pM, respectively, for the simultaneous sensing of the metal ions. The significantly enhanced sensitivity compared to that of N-GQD for Cd(II) and the versatile simultaneous sensing capability of S,N-GQD is assigned to the co-doping with S, which enabled the sensing of Pb(II) and Hg(II) through the M(II)–S interactions and the enhanced electronic properties, respectively. The sensing characteristics were effectively stretched to actual environmental water samples such as groundwater, seawater, and wastewater, spiked with Cd(II), Pb(II), and Hg(II), and accomplished ∼100% recovery in all the tested samples with a relative standard deviation of ≤0.5%.

New nanoadsorbent based on magnetic iron oxide containing 1,4,7,10-tetraazacyclododecane in outer chain (Fe3O4@SiO2-cyclen) for adsorption and removal of selected heavy metal ions Cd2+, Pb2+, Cu2+

Magnetic Fe3O4@SiO2-cyclen nanoparticles were prepared and used as adsorbent for Cd2+, Pb2+ and Cu2+ from aqueous solution removal process controlled with differential pulse anodic stripping voltammetry (DPASV) and hanging mercury drop electrode (HDME). Nanomaterial was synthesised in three-step process co-precipitation of Fe3O4 core, coating with silane and N-(3-(triethoxysilyl)propyl)-1,4,7,10-tetraazacyclododecane-1-carboxamide silane functionalisation. The effectiveness of each step of the synthesis was confirmed using scanning electron microscopy (SEM), high-resolution X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (pXRD) and fourier-transform infrared spectroscopy (FT-IR) techniques. The Fe3O4@SiO2-cyclen nanoparticles were employed for Cd2+, Pb2+ and Cu2+ ions elimination from individual and mixed solutions by carrying out titration with a suspension of nanocomposites. The binding level for all ions both in the individual solutions and in the mixture was very similar at high levels. For Cd2+ and Cu2+ ions sorption efficiency level was from 83% to 89%, while for Pb2+ ions it was slightly lower at the level over 73%. In all cases, the equilibrium adsorption capacity parameter was over 1 mg/g and reached definitely higher values for individual ions solutions. The research results revealed that Fe3O4@SiO2- cyclen nanoparticles can be a promising adsorbent for magnetic heavy metal ions water treatment agents.

Hg (II) and Cd (II) Heavy Metal Ions Detection Based On Fluorescence Using Zn (II) Metal Ion Complex with Pyrazoline Derivatives Ligand

Pyrazoline derivatives can be used as ligands because they have photophysical properties and can chelate metal ions which cause very strong absorption, emission and have a fluorescence properties. Therefore, in recent years, pyrazoline ligands and their derivatives have been widely used for chemosensors. This research aims to detect fluorescence-based heavy metal ions Hg2+ and Cd2+ using a metal ion complex compound Zn2+ with pyrazoline derivative ligand. The research was started by synthesizing pyrazoline-derived ligands, then synthesizing complex compounds. Complex compounds were characterized using Fourier Transform Infra Red (FTIR), UV-Vis Spectrophotometer, and Spectrofluorometer. Then, a fluorescence study was carried out to determine the type of fluorosensor for complex compounds with the addition of heavy metal ions Cd2+ and Hg2+. The last stage is UV-Vis spectroscopy study on the addition of heavy metal ions Hg2+ and Cd2+. Pyrazoline derivative ligand obtained as para-di-2-(1-phenyl-3-pyridyl-4,5-dihydro-1H-pyrazole-5-yl)benzene is a yellow solid. The metal ion complex compound Zn2+ with pyrazolin derivative ligand is a brown colored compound, has a yield of 45 % and a melting point is 245 oC. The FTIR spectrum showed the presence of functional groups such as amine, C-H aromatic, C=N, C=C aromatic, C-N, Zn-N and Zn-Cl. Analysis with UV-Vis spectrophotometer showed that there was a shift in the maximum wavelength from the ligand to the Zn(II)-ligand complex, namely 240 nm to 246 nm and 363 nm with molar absorptivity values (log ) of 4.56 and 4.28, respectively. For fluorescence analysis, two absorbance peaks were obtained, namely at a wavelength of 370 nm with an intensity of 3644 a.u and 478 m at 8216 a.u. The results of fluorescence chemosensor studies on the addition of heavy metal ions Hg2+ and Cd2+ showed that the metal ion complex compound Zn2+ with pyrazoline-derived ligands can detect heavy metal ions Hg2+ and Cd2+ with a turn-on type.

Alkali treatment to transform natural clinoptilolite into zeolite Na–P: Influence of NaOH concentration

In this study, natural clinoptilolite was treated with NaOH solutions of different concentrations under mild ambient conditions. The composition and structure of the as-prepared samples were characterized, and their performance was assessed in terms of the removal of the heavy metal ions Cd2+, Cu2+, and Cr3+ from the aqueous solution. The results showed that the composition, structure, and capability of removal of heavy metal ions of the samples were significantly influenced by the NaOH concentrations. The crystal structure of clinoptilolite remained invariant under a relatively low NaOH concentration (≤0.5 M), began transforming into zeolite Na–P under a medium NaOH concentration (∼1.0 M), and then completely transformed into it under a high NaOH concentration (2.0–4.0 M). The samples treated with NaOH had lower SiO2/Al2O3 ratios, and were superior to unmodified natural zeolite in removing the heavy metal ions. This method of treatment with relatively high concentrations of NaOH is a simple and effective way to transform natural clinoptilolite into the zeolite Na-P rich ion exchanger, which is suitable for removing heavy metal ions.

Decontamination of Cd2+ and Pb2+ from aqueous solution using a magnetic nanocomposite of eggshell/starch/Fe3O4

In the present study, to remove heavy metal ions Cd2+ and Pb2+ from aqueous solution and industrial effluent, a new magnetic nanocomposite based on eggshell/starch/Fe3O4 nanoparticles was used as an effective adsorbent. FTIR analysis showed that the magnetic composite is well synthesized and has different functional groups that can be effective in the adsorption process. In addition, the VSM test showed that the magnetic nanocomposite had a superparamagnetic property. The BET value for magnetic nanocomposite of eggshell/starch/Fe3O4 nanoparticles was determined to be 35.648 m2/g, higher than eggshell nanoparticles. The maximum decontamination efficiency of Cd2+ (96.38%) and Pb2+ (97.86%) was obtained at pH 7 and 6, respectively, temperature 25 °C, contact time of 60 min, metal concentration of 10 mg/L, and adsorbent dose of 1 g/L. The results showed that the adsorption process of the desired ions using eggshell/starch/Fe3O4 nanoparticles follows a pseudo-second-order and the Langmuir models. The Langmuir capacity for Cd2+ and Pb2+ adsorption using eggshell/starch/Fe3O4 was computed at 48.54 and 57.14 mg/g, respectively. The value of the ∆G° parameter for the adsorption process of Cd2+ and Pb2+ was determined in the span of −20 < ∆G° < 0 kJ/mol, which suggests that the adsorption process was performed physically and spontaneously. The value of the parameter ∆H° was also negative, which confirms the exothermic of the process and indicates that the increase in temperature harms the adsorption process. The adsorbent of this study had vital properties like being economical (due to its recyclability) and practicality for wastewater treatment.

Assessment of Casuarina glauca as biofiltration model of secondary treated urban wastewater: effect on growth performances and heavy metals tolerance

The use of fast-growing tree species, such as Casuarina glauca for wastewater treatment could improve the quality of wastewater and offer an ecological and sustainable system. A hydroponically experiment was conducted to evaluate C. glauca ability to remove heavy metals from secondary treated urban wastewater (SWW). The effect of the SWW on plant biomass, some physiological parameters, heavy metals (Cd, Pb, Ni and Zn) bioaccumulation and removal from wastewater was evaluated. After 28days, wastewater treatment C. glauca showed high efficiency for the removal of pathogenic bacteria such as faecal coliforms and faecal streptococci from SWW. A significant reduction was found for electrical conductivity, biochemical oxygen demand, chemical oxygen demand and suspended solids with 31%, 92%, 83% and 31% respectively. Casuarina glauca plants were able to remove heavy metal ions Cd, Pb, Ni and Zn from SWW and the removal efficiency was 92%, 77%, 83% and 73%, respectively. Casuarina glauca plants accumulated concentrations of heavy metals (Cd, Pb, Ni and Zn) in their roots higher than the shoots. SWW had a remarkable effect on plant growth and photosynthetic capacity in C. glauca compared with plants grown in tap water (control). The results indicated that C. glauca can act as scavengers of heavy metal ions from polluted water and confirms their ability for wastewater treatment.

Wastewater treatment using natural zeolite materials

Today, there is an urgent need in our country to develop and implement new energy - and resource-saving technologies for wastewater treatment and water treatment. The need for such a system is determined by the urgency of the tasks of protecting the health of the population, agricultural products, and other biological objects. Wastewater is contaminated with radioactive substances, heavy metal ions, toxic substances, and pathogenic microbes. During the work, wastewater contaminated with heavy metal ions Cd2+, Pb2+ was treated with a natural zeolite material. The mechanism of water purification from metal ions is based on the porous structure and adsorption capacity of zeolite. Heavy metal ions diffuse into the pores of the zeolite material, displacing sodium ions, which are structural modifiers. The zeolite treatment process was carried out by measuring the permeability of wastewater using a conductometer and comparing its results with the value of the permeability of distilled water. According to the results obtained, this method can be used to completely purify wastewater from heavy metal ions.

A novel smartphone-based electrochemical cell sensor for evaluating the toxicity of heavy metal ions Cd2+, Hg2+, and Pb2+ in rice.

A novel smartphone-based electrochemical cell sensor was developed to evaluate the toxicity of heavy metal ions, such as cadmium (Cd2+), lead (Pb2+), and mercury (Hg2+) ions on Hep G2 cells. The cell sensor was fabricated with reduced graphene oxide (RGO)/molybdenum sulfide (MoS2) composites to greatly improve the biological adaptability and amplify the electrochemical signals. Differential pulse voltammetry (DPV) was employed to measure the electrical signals induced by the toxicity of heavy metal ions. The results showed that Cd2+, Hg2+, and Pb2+ significantly reduced the viability of Hep G2 cells in a dose-dependent manner. The IC50 values obtained by this method were 49.83, 36.94, and 733.90μM, respectively. A synergistic effect was observed between Cd2+ and Pb2+ and between Hg2+ and Pb2+, and an antagonistic effect was observed between Cd2+ and Hg2+, and an antagonistic effect at low doses and an additive effect at high doses were found in the ternary mixtures of Cd2+, Hg2+, and Pb2+. These electrochemical results were confirmed via MTT assay, SEM and TEM observation, and flow cytometry. Therefore, this new electrochemical cell sensor provided a more convenient, sensitive, and flexible toxicity assessment strategy than traditional cytotoxicity assessment methods.

Evaluating the adsorption of Shanghai silty clay to Cd(II), Pb(II), As(V), and Cr(VI): kinetic, equilibrium, and thermodynamic studies.

The adsorption properties of Shanghai silty clay (SSC) towards heavy metal ions Cd(II), Pb(II), As(V), and Cr(VI) were investigated by batch experiments. The effects of solid-solution ratio, pH, temperature, reaction time, and metal concentration on sorption were analyzed. In order to better understand the adsorption mechanisms, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray fluorescence (XRF) were used to analyze the soil specimen before and after sorption. Three adsorption kinetic models and three adsorption isotherm models were used to analyze the adsorption characteristics. Thermodynamic parameters including changes in the Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were also calculated. Sorption capacity of SSC was compared with other clay minerals reported in the literatures. The results show that the selectivity sequence is Pb(II) > Cd(II) > As(V) > Cr(VI), with equilibrium sorption capacities of 26.46, 8.90, 2.80, and 1.85mgg-1, respectively. Adsorption is largely effective on the clay surface rather than on the crystals. The clay surface turns to be flat and slippery after adsorption. The Langmuir model shows the best fit for Cd(II) and Pb(II) data, while Freundlich model is more suitable for As(V) and Cr(VI). The optimum solid-solution ratios for sorption of Cd(II), Pb(II), As(V), and Cr(VI) are 15, 6, 40, and 40g L-1, respectively. The optimum pHs for Cd(II), Pb(II), As(V), and Cr(VI) adsorption are 9.0, 6.0, 7.0, and 2.0, respectively. The pseudo-second-order kinetic is found to be the dominant sorption mechanism of these four ions on SSC. For Cd(II) and Pb(II), both particle diffusion and film diffusion are rate-limiting factors, whereas for As(V) and Cr(VI), intraparticle diffusion is the rate-controlling factor. The thermodynamic analysis reveals that the adsorption of Cd(II) and Pb(II) is spontaneous and endothermic and the system disorder increases, while adsorption of As(V) and Cr(VI) is exothermic and the system disorder decreases. Compared with most clay minerals, natural SSC exhibits comparable adsorption capacity and thus can potentially be used as a landfill liner material to retard the migration of heavy metals.

Green synthesis of network nanostructured calcium alginate hydrogel and its removal performance of Cd2+ and Cu2+ ions

In this work, we present a simple and green preparation method for the synthesis of three-dimensional (3D) network nanostructured sodium alginate (NNSA) hydrogel. Such special structure derives from the self-weaving of sodium alginate nanowires (SA NWs) with diameters of <30 nm rather than the introduction of divalent cations, binders, and skeleton supports. By the appropriate cross-linking of the NNSA hydrogel and Ca2+ ions, calcium alginate (CA) hydrogel with the same morphology and structure can be easily prepared in large quantities and the stability of the 3D network nanostructures in aqueous solution is evidently improved. To evaluate the adsorption performances of the 3D network nanostructured calcium alginate (NNCA) hydrogel, we select heavy metal ions Cd2+ and Cu2+ as the model inorganic contaminants in aqueous solutions. The effects of dosage, pH, initial concentration, contact time, and temperature on the adsorption performances are investigated. The testing results show relatively high removal efficiency, rapid adsorption rate, and small absorbent dosage. The adsorption behavior of the NNCA hydrogel matches well with the Langmuir isotherm model and pseudo-second-order kinetics model. Besides, adsorption thermodynamics and adsorption mechanism are also studied, and the results show diffusion-controlled process and bidentate bridging (BB)/bidentate chelating (BC) coordination modes, respectively.

Signal Decoding for Glutamate Modulating Egg Laying Oppositely in Caenorhabditis elegans under Varied Environmental Conditions.

SummaryAnimals' ability to sense environmental cues and to integrate this information to control fecundity is vital for continuing the species lineage. In this study, we observed that the sensory neurons Amphid neuron (ASHs and ADLs) differentially regulate egg-laying behavior in Caenorhabditis elegans under varied environmental conditions via distinct neuronal circuits. Under standard culture conditions, ASHs tonically release a small amount of glutamate and inhibit Hermaphrodite specific motor neuron (HSN) activities and egg laying via a highly sensitive Glutamate receptor (GLR)-5 receptor. In contrast, under Cu2+ stimulation, ASHs and ADLs may release a large amount of glutamate and inhibit Amphid interneuron (AIA) interneurons via low-sensitivity Glutamate-gated chloride channel (GLC)-3 receptor, thus removing the inhibitory roles of AIAs on HSN activity and egg laying. However, directly measuring the amount of glutamate released by sensory neurons under different conditions and assaying the binding kinetics of receptors with the neurotransmitter are still required to support this study directly.

Impregnation of polyethylene membranes with 1-butyl-3-methylimidazolium dicyanamide ionic liquid for enhanced removal of Cd2+, Ni2+, and Zn2+ from aqueous solutions

In this study, commercial hydrophobic polyethylene (PE) membranes were impregnated with 1-butyl-3-methylimidazolium dicyanamide ([BMIM][DCA]) hydrophilic ionic liquid (IL) and tested for the rejection of metals ions. Three homogenous mixtures containing ethanol and IL with ethanol: IL volume ratio of 15:5 (M-IL1), 12:8 (M-IL2), and 10:10 (M-IL3) were prepared. The impregnation of the IL was ascertained using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Structural and surface characteristics of the membranes, including porosity, water contact angle, tensile strength, and surface charge, were studied. Results showed that the IL impregnation has led to remarkable changes in the surface properties of the PE membrane. For instance, the water contact angle and surface porosity of the membranes have decreased from 130.1 ± 1.5° to 94.5 ± 6.7°, and from 85% to 10% in the PE and M-IL3 membranes; respectively. The heavy metal ions Cd2+, Ni2+, and Zn2+ rejection percentage has increased from 35.73 ± 4.41, 39.40 ± 1.23, and 52.89 ± 3.08% in the pristine PE membrane to 52.87 ± 1.82, 51.47 ± 0.61, and 68.05 ± 1.27%; respectively in the M-IL3 membrane. This removal was reported at pure water flux of 22.12 ± 1.22 L m−2 h−1. The enhanced removal was attributed to the ability of the IL DCA- anion to form stable complexes with the heavy metal cations through ion exchange, the formation of hydroxides species, and electrostatic attraction forces. The new membranes have great potential for their application in the remediation of industrial wastewater containing heavy metal ions.

Influence of operating conditions on the retention of severe industrial wastewater by nanofiltration

ABSTRACT The presence of metals in industrial wastewater is a major health risk in many places in the world. On pilot, the suitability of a thin film polyamide nanofiltration composite membrane (SNTE NF270-2540) to extract heavy metal ions (Zn, Cr, Cu, Fe, Cd, Pb, Co & Ni) from industrial wastewater was examined. The operating conditions including feed pH value, feed concentration and pressure were studied. The membrane was characterised by using the ions transport model and the consumption energy was calculated. The effect of ionic concentration and the diffusion fluxes were studied. The retention of Iron at pH = 5.3 and Nickel at pH = 7.2 and for pressures from 6.0 to 13.5 bars was quantitative (100%). For Lead at pH = 4.4 and for pressures from 6.0 to 10 bars, the retention was quantitative (100%). In general, the nanofiltration process is recommended to be applied in practice for the extraction of heavy metals from wastewater.

Effect of Dispersibility of Natural Sorbents on Their Sorption Activity for Cd(II), Pb(II), and Cu(II) Ions

The effect of the degree of dispersion of sorbent particles derived from natural minerals (vermiculite and perlite) on their sorption properties towards heavy metal ions Cd(II),Cu(II), and Pb(II) is studied. The particle sizes of the sorbents vary in the range from submicrons to nanometers (from 250 μm to 100 nm), using a range of dispersion methods (grinding using centrifuge and planetary ball mills),which result in a reduction of the particle size by 1.5–100 times. It is found that the sorption of the examined metal ions on the surface of all the substates can be described by the Langmuir absorption model, regardless of the degree of sorbent dispersion. The low values of the heat of the sorption for ions studied indicate the physical nature of sorption. An increase in the dispersion degree of the sorbents contributed to a significant increase in the sorption activity of dispersed particles of vermiculite and perlite towards to the ions studied (up to 2-fold increase in the sorption degree values). The optimization of the sorption conditions made it possible to achieve high sorption efficiency with the sorption degree ~99.9% towards Cd(II), Cu(II), and Pb(II) ions at a 10-4 mol/L ion concentration and close to neutral conditions at ambient temperature.