Heavy Metals In Aqueous Solutions Research Articles

Magnetic removal/immobilization of cadmium and zinc in contaminated soils using a magnetic microparticle solid chelator and its effect on rice cultivation

Magnetic removal techniques using functionalized magnetic nanoparticles as adsorbents have been frequently tested for use in the removal of heavy metals in aqueous solution, but seldom in farmland soil. Here, a novel magnetic microparticle solid chelator (MSC) was employed as the adsorbent for magnetic removal and/or immobilization of Cd and Zn in a paddy soil (PS), an upland soil (US), and a paddy–upland rotation soil (RS) with different degrees of pollution. MSC was applied to 14 kg air-dried soil samples (PS, US, and RS) at the dosage of 1% (w/w), and then watered, and intermittently stirred. Finally, the MSC–metal complexes were retrieved using a magnetic device (MCR treatment) or not (MC treatment), and the removal efficiency of soil Cd and Zn in MCR treatment was evaluated. After magnetic separation of MSC–metal complexes, pot experiments were performed to investigate the impacts of the magnetic remediation process on rice growth, the phytoavailability of soil Cd and Zn, and the accumulation of Cd and Zn in rice plants. The MCR treatment exhibited recovery rates of 55.4%, 49.6%, and 19.0% for MSC–metal complexes in PS, US, and RS, respectively, which brought about removal efficiencies of 2.2–12.2% for Cd and 1.9–4.6% for Zn. The MC and MCR treatments substantially decreased the availability of soil Cd, but not soil Zn; this effect was more remarkable when using CaCl2 instead of DTPA as the extractant for determination of bioavailable metals. Furthermore, the CaCl2-extractable Cd and Zn had a more significant relationship with Cd and Zn concentrations in rice roots. The MC and MCR treatments led to dramatic reductions in rice grain Cd of 23.9–72.1% and 37.3–63.9%, respectively, in the three soils relative to the respective controls. The MC and MCR treatments also exhibited an inhibitory effects on rice grain Zn accumulation in US (10.6% and 4.3% decreases, respectively) and RS (9.3% and 19.5% decreases, respectively), but not in PS. Moreover, the grain yield was unaffected under the MCR treatment in the three soils, and significantly increased by 29.8% under the MC treatment in US. Our study suggests that MSC-based magnetic remediation technique can effectively immobilize and/or remove Cd and Zn in farmland soils, decreasing their uptake by rice plants, with no adverse effects on grain yield.

Reduced texaphyrin: A ratiometric optical sensor for heavy metals in aqueous solution.

We report here a water-soluble metal cation sensor system based on the as-prepared or reduced form of an expanded porphyrin, texaphyrin. Upon metal complexation, a change in the redox state of the ligand occurs that is accompanied by a color change from red to green. Although long employed for synthesis in organic media, we have now found that this complexation-driven redox behavior may be used to achieve the naked eye detectable colorimetric sensing of several number of less-common metal ions in aqueous media. Exposure to In(III), Hg(II), Cd(II), Mn(II), Bi(III), Co(II), and Pb(II) cations leads to a colorimetric response within 10 min. This process is selective for Hg(II) under conditions of competitive analysis. Furthermore, among the subset of response-producing cations, In(III) proved unique in giving rise to a ratiometric change in the ligand-based fluorescence features, including an overall increase in intensity. The cation selectivity observed in aqueous media stands in contrast to what is seen in organic solvents, where a wide range of texaphyrin metal complexes may be prepared. The formation of metal cation complexes under the present aqueous conditions was confirmed by reversed phase high-performance liquid chromatography, ultra-violet-visible absorption and fluorescence spectroscopies, and high-resolution mass spectrometry.

Synthesis of FeO@SiO2-DNA core-shell engineered nanostructures for rapid adsorption of heavy metals in aqueous solutions.

Creating novel and innovative nanostructures is a challenge, aiming to discover nanomaterials with promising properties for environmental remediation. In this study, the physicochemical and adsorption properties of a heterogeneous nanostructure are evaluated for the rapid removal of heavy metal ions from aqueous solutions. Core–shell nanostructures are prepared using iron oxide cores and silica dioxide shells. The core is synthesized via the co-precipitation method and modified in situ with citric acid to grow a carboxyl layer. The shell was hydrolyzed/condensed and then functionalized with amine groups for ds-DNA condensation via electrostatic interaction. The characterization techniques revealed functional FeO@SiO2–DNA nanostructures with good crystallinity and superparamagnetic response (31.5 emu g−1). The predominant superparamagnetic nature is attributed to the citric acid coating. This improves the dispersion and stability of the magnetic cores through the reduction of the dipolar–dipolar interaction and the enhancement of the spin coordination. The rapid adsorption mechanism of FeO@SiO2–DNA was evaluated through the removal of Pb(ii), As(iii), and Hg(ii). A rapid adsorption rate is observed in the first 15 min, attributed to a heterogeneous chemisorption mechanism based on electrostatic interactions. FeO@SiO2–DNA shows higher adsorption efficiency of 69% for Pb(ii) removal compared to As(iii) (51%) and Hg(ii) (41%). The selectivity towards Pb(ii) is attributed to the similar acid nature to ds-DNA, where the ionic strength interaction provides good affinity and stability. The facile synthesis and rapid adsorption suggest a promising nanostructure for the remediation of water sources contaminated with heavy metal ions and can be extended to other complex molecules.

Unrevealing the biosorption capacity of freshwater algae biomasses for toxic heavy metals in aqueous solutions

Unrevealing the biosorption capacity of freshwater algae biomasses for toxic heavy metals in aqueous solutions

Electroanalytical determination of heavy metals in aqueous solutions by using a carbon paste electrode modified with spent coffee grounds

In this paper, the quantification of Pb2+ and Cd2+ at trace levels was carried out by differential pulse anodic stripping voltammetry technique, using a paste carbon electrode modified with spent coffee grounds (SCG) as working electrode. Different percentages of SCG (40, 50, 60, 70% of SCG) were tested in the experiments; the best electrochemical response was obtained with the electrode modified with 50% of SCG. An experimental design was performed in order to maximize the intensity of the oxidation current, using the accumulation time and the reduction potential as factors. The best experimental conditions for the electrodeposition of the cadmium ions were obtained at an accumulation time of 76 s, and the reduction potential of −1115 mV; while for the electrodeposition of lead ions, the best performance was obtained at an accumulation time of 120 s and a reduction potential of −1200 mV. The detection limit of the carbon paste electrode modified with 50% of SCG were 89 and 90 μM for Cd(II) and Pb(II), respectively, showing the potential of these electrodes as a viable and sustainable alternative for the determination of heavy metals in aqueous solutions.

Investigation of detoxification nature of activated carbons developed from Manilkara zapota and de oiled soya

Abstract Heavy metals are poisonous and detrimental water contaminant. Their existence affects human beings, animals and vegetation as a outcome of their mobility in aqueous ecosystem, toxicity and non-biodegradability. This work aimed at the development of new adsorbent in the detoxification of heavy metals using Manilkara zapota tree wood and de oiled soya. The study completely focused on the characterization of the developed activation in the view of using it as a adsorbent. The characterization of activated carbon was effected SEM analysis, FTIR, XRD analysis and surface area determination. Both the activation carbon have showed a tremendous characterization in their employability as adsorbent in adsorption of heavy metals in aqueous solution.

Synthesis of Hydroxy-Sodalite/Cancrinite Zeolites from Calcite-Bearing Kaolin for the Removal of Heavy Metal Ions in Aqueous Media

A hydroxy-sodalite/cancrinite zeolite composite was synthesized from low-grade calcite-bearing kaolin by hydrothermal alkali-activation method at 160 °C for 6 h. The effect of calcite addition on the formation of the hydroxy-sodalite/cancrinite composite was investigated using artificial mixtures. The chemical composition and crystal morphology of the synthesized zeolite composite were characterized by X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, and N2 adsorption/desorption analyses. The average specific surface area is around 17–20 m2·g−1, whereas the average pore size lies in the mesoporous range (19–21 nm). The synthesized zeolite composite was used as an adsorbent for the removal of heavy metals in aqueous solutions. Batch experiments were employed to study the influence of adsorbent dosage on heavy metal removal efficiency. Results demonstrate the effective removal of significant quantities of Cu, Pb, Ni, and Zn from aqueous media. A comparative study of synthesized hydroxy-sodalite and hydroxy-sodalite/cancrinite composites revealed the latter was 16–24% more efficient at removing heavy metals from water. The order of metal uptake efficiency for these zeolites was determined to be Pb > Cu > Zn > Ni. These results indicate that zeolite composites synthesized from natural calcite-bearing kaolin materials could represent effective and low-cost adsorbents for heavy metal removal using water treatment devices in regions of water shortage.

Adsorption study of heavy metals in aqueous solutions aiming at the treatment of contaminated groundwater

This study evaluates the application of the vegetal activated carbon (AC), vegetable AC impregnated with Ag and Cu (0.08% m/m) and cationic SupergelTM SGC650H resin for adsorption of Fe3+ and Pb2+ ions in closed and batch system. The best adsorption capacities were obtained by using the cationic resin SGC650H, pH 3, temperature of 30 °C and stirring speed of 100 rpm. Thus, the kinetic and equilibrium experiments, in mono- and bicomponent, were performed using SGC650H resin, wherein the kinetic models of pseudo-first and pseudo-second order presented a good fit to the kinetic data, for mono- and bicomponent, respectively. The Langmuir isotherm adequately represented the monocomponent equilibrium data, showing maximum adsorption capacities values of 7.18 and 4.00 meq g−1 for Fe3+ and Pb2+, respectively. An inhibitory effect between the metal species was verified by fitting the modified extended Langmuir isotherm model to the binary equilibrium data, which allowed to predict changes in the surface affinity to the adsorbent by the metal ions. Based on the observed results, the use of SGC650H resin presents great potential for water treatment systems contaminated with heavy metals.

Novel and green nanocomposite-based adsorbents from functionalised mesoporous KCC-1 and chitosan-oleic acid for adsorption of Pb(II)

To capture heavy metals in aqueous solution, it is imperative to develop viable and safe heavy metals uptake techniques. Herein, we report polymer matrix nanocomposite adsorbents with 2 and 5 wt.% nanofiller contents based on functionalised mesoporous fibrous silica KCC-1, chitosan, and oleic acid (abbreviated as TA-KCC-1/Chi-OLA NC). TA-KCC-1/Chi-OLA NCs relying on physicochemical adsorption are potential candidates for heavy metals removal because of their facile fabrication procedure, low toxicity, biodegradability, and high affinity toward heavy metals. The adsorption of Pb(II) cations onto green TA-KCC-1/Chi-OLA 5 wt.% adsorbent was studied in the batch system. Langmuir and pseudo-second-order models were found to be the best fit models to predict isotherms and kinetics of adsorption, respectively. The maximum adsorption capacity according to the Langmuir model was 168 mg g−1 (adsorption conditions: pH: 9.0, adsorbent dose: 20.0 mg; contact time: 100 min; initial concentration: 100 mg L−1).

Effect of humic acid on the stabilization of cadmium in soil by coprecipitating with ferrihydrite

Coprecipitation of humic acid (HA) with ferrihydrite (Fh) has been proposed to reduce the activity of heavy metals in aqueous solutions. The effect of the amount of HA added to the coprecipitates on the stabilization of Cd in soil is unclear. In this research, five different Fh-HA coprecipitates were synthesized to study the impact of different HA additions on the fractionation of Cd in the soil and the optimal addition ratio of C/Fe. Characterization technique as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), specific surface area analyzer, and scanning electron microscopy (SEM) was used in order to test and analyze of the microstructure and physicochemical property of the coprecipitates. The results showed that the Fh-HA coprecipitate is mainly combined by the coordination exchange of -OH on the surface of the Fh with the carboxyl group of the HA. Adding HA could stabilize Fh and increase its surface roughness. Changes in the fractionation of the Cd were used to evaluate the stabilization effect of the coprecipitate. Before treatment, Cd in different contaminated soils was existed only a small amount of residual fraction. After the addition of the Fh-HA coprecipitate, the proportion of residual Cd in each contaminated soil increased. When the C/Fe ratio was 1.5, the maximum residual fraction were 62.94%, 55.67%, and 52.99% respectively. Residual Cd could remain relatively stable indicating that the Fh-HA coprecipitate is a promising amendment for repairing Cd-contaminated soil. The addition of HA has strengthened the active role of Fh on stabilizing heavy metals.

Micro algal systems for biosequestration of heavy metals in aqueous solution

Micro algal systems for biosequestration of heavy metals in aqueous solution

Individual and Simultaneous Voltammetric Determination of Cd(II), Cu(II) and Pb(II) Applying Amino Functionalized Fe3O4@Carbon Microspheres Modified Electrode

AbstractAmino‐functionalized Fe3O4@carbon microspheres (NH2−Fe3O4@C) were prepared and the electrochemical sensor was constructed using NH2−Fe3O4@C modified glassy carbon electrodes (GCE) to determine toxic heavy metals in aqueous solution. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the structure and phase of NH2−Fe3O4@C. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results indicate that NH2−Fe3O4@C modified GCE possesses large active area and excellent electron transfer. Under optimized electrochemical condition, Cd(II), Pb(II) and Cu(II) were determined using NH2−Fe3O4@C modified GCE. The electrode through amino functionalization exhibits higher sensitivity and lower detection limit toward Cd(II) and Cu(II) due to the acid‐base pairing interaction between the electron‐rich −NH2 ligand and the electron‐deficient heavy metal ions. Compared with other similar results reported in the literature, the NH2−Fe3O4@C modified electrode exhibits wider linear response range while with comparable lower detection limit. It also exhibits excellent stability, reproducibility and anti‐interference ability.

Interaction of epitaxial graphene with heavy metals: towards novel sensing platform

Development of next-generation sensors based on graphene materials, especially epitaxial graphene (EG) as the most promising representative, with desirable cross-reactivity to heavy metals (HMs) is of great technological significance in the virtue of enormous impact on environmental sensorics. Nevertheless, the mechanisms by which EG responds to toxic HMs exposure and then produces the output signal are still obscure. In the present study, the nature of interaction of toxic HMs, e.g. Cd, Hg and Pb in neutral charge state and EG on Si-face SiC in the absence and in the presence of pure water solution has been investigated using density functional theory with the inclusion of dispersion correction and cluster model of EG. The gas-phase calculations showed that adsorbed electron-donating Cd and Hg adatoms on EG are most stable when bonded to hollow sites, while Pb species prefer to sit above bridge sites. By using non-covalent interaction analysis, charge decomposition analysis, overlap population density of states analysis and topological analysis, it was found that the interaction between Cd or Hg and EG is non-bonding in nature and is mainly governed by van der Waals forces, while Pb adsorption is followed by the formation of anti-bonding orbitals in vacuum conditions and bonding orbitals in water. The role of solvent in the adsorption behavior of HMs is studied and discussed. The present theoretical analysis is in good agreement with recent experimental results towards discriminative electrochemical analysis of the toxic HMs in aqueous solutions at critically low concentrations.

Single and Binary Adsorption of Zn (II) and Cr (VI) Heavy Metals onto Synthesized Silica ‐Based MCM‐41

AbstractEffluents from numerous Industries like textile, paint, pharmaceutical, steel and electroplating industries liberate both Zinc [Zn (II)] and Chromium [Cr (VI)] heavy metals. In this work, adsorptive interaction of toxic Zn (II) heavy metal in aqueous solution with synthesized mesoporous silica based MCM‐41 was investigated. Further, the effects of presence of Cr (VI) heavy metal on the adsorption of Zn (II) and vice versa were investigated by simultaneous competitive binary adsorption from Cr (VI) and Zn (II) aqueous binary solution. Batch experiments were executed to see the effects of parameters like pH, adsorbent dose (m), adsorbate concentration and adsorption time (t). Optimum conditions for Zn (II) treatment were obtained as: initial pH (pHi) =7, m=0.1 g/L and t=2 h. Competitive adsorption of both Cr (VI) and Zn (II) from their binary solution was studied at 288− 308 K temperatures. Obtained equilibrium data were then fitted to different competitive multicomponent isotherm models like Langmuir (extended), Freundlich isotherm (extended), Sheindrof‐Rebuhn‐Sheintuch (SRS) isotherm and Redlich‐Peterson isotherm (modified) models, and various isotherm interaction parameters were calculated.

Kinetic Study of Garlic and Ginger Particles in Adsorption of Heavy Metals in Aqueous Solution

This study involved investigation and comparison of the capacity of garlic and ginger particles in adsorption of lead, cadmium and chromium ions from contaminated water. This was motivated by the perennial contamination of well water by crude oil, which carried alongside heavy metals from earth surface and other sources in contact with it while discharging from oil facilities to the subsurface region. Heavy metal analysis on the well water and crude oil from the polluted site showed high level of heavy contamination. Effect of initial concentration of heavy metals, adsorbents dosage and contact time on adsorption of the lead, cadmium and chromium ions in aqueous solution by garlic and ginger particles were studied. Garlic and ginger particles adsorption process was studied using Langmuir and Temkin isotherms. Also, to describe the kinetics of the adsorption process, the Pseudo first and second order kinetics as well as the intra-particle diffusion kinetics were used to study the experimental data. The analysis showed that the percentage of lead, cadmium and chromium ions adsorbed by garlic and ginger particles decreased as the initial concentration of metals in solution and contact time were increased. Similarly, the percentage of lead, cadmium or chromium ions adsorbed by the garlic and ginger particles at equilibrium increased as adsorbent dosages was increased due to increased effective surface area of the adsorbent. Equilibrium was attained at about 60 minutes with either garlic or ginger particles. However, garlic particles adsorbed the heavy metals more than the particles of ginger at all conditions. Also, it was observed that lead ion has more affinity to both garlic and ginger particles followed by cadmium ion. The adsorption of lead, cadmium and chromium ions were better explained by the Langmuir isotherm model than the Temkin’s isotherm model. The maximum adsorption capacity for lead, cadmium and chromium ions with garlic particles were 3.9308 mg/g, 3.3223 mg/g and 1.992 mg/g while that of ginger particles were 2.9011 mg/g, 2.3121 mg/g and 1.9543 mg/g respectively. The adsorption of lead, cadmium and chromium ions in the solution of both adsorbents revealed that diffusion and chemisorptions occurred in the adsorption process, which was best fitted in the Pseudo second order kinetics. Indicating that the Pseudo second order kinetics was the rate controlling step, and thus, will predict accurately the concentration of metal ions adsorbed. Conclusively, the garlic and ginger particles showed capacity for the removal of lead, cadmium and chromium in aqueous solution, and therefore are recommended for use in adsorption of heavy metals in wastewater. Keywords : Garlic, Ginger, Heavy metals, Adsorption Isotherm, Kinetics DOI : 10.7176/CPER/60-04 Publication date :March 31 st 2019

A study of adsorption of cadmium, copper and lead by two clays from Burkina Faso

Water pollution caused by natural and anthropogenic causes become a major problem for many countries around the world in trying to find adequate and accessible means of treating polluted water. For more than a decade, research is focused on local adsorbent materials such as clays. It is in this dynamic that two clays extracted in Burkina Faso and referenced KORO and SIT were used to evaluate their capacities to reduce the content of heavy metals in aqueous solutions simulating waste water. The monitoring of the removal processes uses electrochemical characterizations, as voltammetry, evidencing a removal degree of heavy metals exceeding 90%. Characterizations of the process were also obtained by X-ray diffraction, Infrared Spectroscopy and Scanning Electron Microscopy. It is shown that the removal process occurs through the formation of clay-heavy metals complexes with both KORO and SIT. The three major mechanisms that were evidenced are complexation, ion-exchange and precipitation. © 2018 International Formulae Group. All rights reserved Keywords: Clay; adsorption; heavy metals; waste water; removal

Fabrication and Characterization of CTS/Coconut Composite Membranes Crosslinked with Glutaraldehyde for Elimination of Heavy Metal in Aqueous Solution

Chitosan/coconut (CTS/coconut) composite membranes were successfully prepared by the cross-linking reaction with glutaraldehyde and they were applied in eliminating heavy metals from aqueous solutions. The cross-linked membranes were obtained at the ratios of 1/1, 1/1.5 and 1/2 and the coconut fiber was chemically treated by NaOCl/NaOH. The best ratio of CTS/coconut fiber is found to be 1/1.5 which has a relatively high stability with the degree of swelling (DS) and solvent content (SC) of membrane to be 13.33% and 69.88%, respectively. The results also indicate that the CTS membranes showed preferential separation of heavy metals for blend CTS/coconut membranes.

Competitive adsorption of heavy metals in aqueous solution onto biochar derived from anaerobically digested sludge

Heavy metals often coexist in contaminated wastewater systems and their competitive behavior could affect the adsorption capacity of biochar. Till now, the competitive adsorption of heavy metals by biochar derived from anaerobically digested sludge has never been reported. In this work, biochar from anaerobically digested sludge was synthesized and characterized to explore the competitive behavior of widely co-existed Pb(II) and Cd(II). The mutual effects and inner mechanisms of their adsorption on studied biochar were systematically investigated via single-metal and binary-metals systems. In single-metal system, the biochar exhibited much higher adsorption capacity for Pb(II) compared to that for Cd(II). The maximum adsorption capacities of Pb(II) and Cd(II) based on single-component adsorption isotherm were 0.75 and 0.55 mmoL/g, respectively, which were much higher than those reported biochars from different materials. In binary-metals system, the Cd(II) adsorption on biochar was severely inhibited, while the uptake of Pb(II) was not affected significantly. The results of binary-components adsorption isotherm clearly demonstrated the competitive adsorption between two metals occurred as well as the preference of biochar for Pb(II) compared to Cd(II). FTIR and metal characteristics analysis results revealed that Pb(II) had exactly the same adsorption sites with Cd(II), but Pb(II) has a greater affinity than Cd(II), thereby exhibiting a competitive advantage in the coexisting system.

Evaluation of the colloidal stability and adsorption performance of reduced graphene oxide–elemental silver/magnetite nanohybrids for selected toxic heavy metals in aqueous solutions

Reduced graphene oxide (rGO) hybridized with magnetite and/or elemental silver (rGO/magnetite, rGO/silver, and rGO/magnetite/silver) nanoparticles were evaluated as potential adsorbents for toxic heavy metal ions (Cd(II), Ni(II), Zn(II), Co(II), Pb(II), and Cu(II)). Although the deposition of iron oxide and silver nanoparticles on the rGO nanosheets played an inhibitory role in metal ion adsorption, the metal adsorption efficiency by the nanohybrids (NHs) was still higher than that reported for many other sorbents (e.g., activated biochar, commercial resins, and nanosized hydrated Zr(IV) oxide particles). X-ray photoelectron spectroscopy analyses revealed that complexation with deprotonated adsorbents and cation exchange was an important mechanism for Cd(II) ion removal by the rGO and NHs. Competitive adsorption tests using multi metals showed that the adsorption affinity of metal ions on the rGO and its NHs follows the order (Cu(II), Zn(II)) > Ni(II) > Co(II) > (Pb(II), Cd(II)), which is similar to the order observed for single-metal adsorption experiments. These results can be explained by the destabilization abilities of the rGO and NHs, as well as the ionic radii of the considered metal ions. Our findings demonstrate the feasibility of using rGO-based NHs as highly efficient adsorbents for heavy metal removal from water.

Anodization of Zirconia Nanotubes for Lead (II) Adsorption

Zirconia (ZrO2) nanotubes were prepared by anodization of zirconium (Zr) foil in a glycerol-formamide electrolyte containing ammonium fluoride. The effects of anodizing voltage and temperature on the pore diameter and thickness of the resulting nanotube array were studied. ZrO2 nanotubes with larger pore diameter were formed at higher anodizing voltage and temperature. Additinally, the thickness of the oxide layer was also increased. The applicability of the ZrO2 nanotubes for adsorption of heavy metals in aqueous solution was evaluated using Pb (II) as the model ions. Generally, the uptake of Pb (II) was increased at longer adsorption time and higher initial concentration of the adsorbate.