Leaching Of Metal Ions Research Articles

Mixed (Fe2+ and Cu2+) double metal hexacyanocobaltates as solid catalyst for the aerobic oxidation of oximes to carbonyl compounds

Mixed Iron and copper hexacyanocolbatate was found to be a suitable heterogeneous and recoverable catalyst for the aerobic oxidation of oximes to the corresponding ketone. The reaction can be conveniently carried out in water-ethanol 1-1 mixture as solvent. The tinme-conversion plots shows the presence of an induction period that do not correspond to the leaching of metal ions or to the damage of the crystal structure of the material. The proposed reaction mechanism is based on the cooperation of the Lewis acidity of iron with the ability of copper to interact with oxygen. Given the remarkable stability of metal hexacyanocobaltates and the large diversity of metals that can contain, our reports opens the way for the general use of these affordable and accessible solids as heterogeneous catalysts.

A comparative evaluation of sorbents for the treatment of complex metal-bearing laboratory wastewaters

This study examined the potential use of a range of sorbents (crab shell, chitosan, activated carbon, ion exchange resin, peat, sawdust, bagasse, Turbinaria conoides, Sargassum sp. and Ulva sp.) for simultaneous removal of 8 heavy metals from synthetic research laboratory effluents. The sorption experiments were conducted in both batch and continuous modes of operation. Among the sorbents used in this study, crab shell proved to be effective with a total biosorption capacity of 440mg/g at pH 4.5. Continuous-flow experiments with crab shell loaded in an up-flow packed column were successful with a total biosorption capacity of 165mg/g. The crab shell-based biosorption process was also identified to be superior to the commonly used hydroxide precipitation technique. This work reveals some practical issues associated with the biosorption process such as leaching of excess light metal ions, poor affinity toward anions and effluent odor. The study also highlights other shortcomings of biosorption, and proposes technical approaches to overcome them.

Turning a frown upside down: Exploiting nanoparticle toxicity for anticancer therapy

The use of nanosized materials is rapidly increasing, both in technological applications for daily use and in biomedical research. The use of these materials, especially for biomedical purposes is however still limited as the potential toxicity of nanomaterials warrants a lot of caution. The generation of a lot of toxicological data concerning nanomaterials sometimes creates a negative perception on their use. However, not all nanomaterials are the same and our understanding of how toxicity exerts itself and ways of how to control it for various particles is increasing. This control also offers us the possibility to exploit nanoparticle toxicity in a targeted manner, by means of selective autophagy induction or leaching of metal ions as a novel anticancer therapy. This manuscript provides an overview of work done on these topics, important achievements and key issues that need to be resolved to mature this novel scientific discipline.

Glass Frit Dissolution Influenced by Material Composition and the Water Content in Iodide/Triiodide Electrolyte of Dye-Sensitized Solar Cells

To ensure long-term stable dye-sensitized solar cells (DSCs) and modules, a hermetic sealing is required. This research investigates the chemical stability ofI-/I3-redox electrolyte and four different glass frits (GFs). Sintered GF layers were openly exposed to nonaqueous redox electrolyte and redox electrolyte with 1, 5, and 10 wt% H2O in thin, encapsulated cells. The change inI3−absorbance was assigned to a reaction between the GF andI-/I3-electrolyte and was used to evaluate the chemical stability of the different GFs. TheI3−absorbance change was monitored over 100 days. Two out of the four GFs were unstable when H2O was added to the redox electrolyte. The H2O caused metal ion leaching which was determined from EDX analysis of the inorganic remains of electrolyte samples. A GF based on Bi2O3–SiO2–B2O3with low bond strength leached bismuth into electrolyte and formed theBiI3-complex. A ZnO–SiO2–Al2O3-based GF also became unstable when H2O was added to the redox electrolyte. Leaching of zinc ions due to exchange with H+resulted in the formation of a zinc-iodine compound which causedI3−depletion. By applying the test design to different types of GFs, the material suitability in the DSC working environment was investigated.

Adsorption Behaviors and Mechanisms of Methyl Orange on Heat-Treated Palygorskite Clays

Understanding completely the interaction of clay mineral and anionic dye is very important for the applications of clay minerals. In this paper, the adsorption behaviors of heat-treated palygorskite clays for methyl orange (MO) from an aqueous medium were studied using equilibrium batch and theoretic calculation techniques. The crystal structure and surface appearance of the heat-treated samples were studied using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The adsorption results reveal that a higher calcining temperature helps in improving removal performance of palygorskite clay for methyl orange. The isothermal adsorption experiments show that there is almost no adsorption at low dye concentrations but a sudden linear increase occurs when the dye concentration exceeds to a certain value. A lower change point is observed for 700 °C treated sample compared with that of the natural sample. The leaching of exchangeable Mg2+ ions located in palygorskite should be a key factor affecting the adsorption capacity. Both the experimental and theoretical studies suggest that the adsorption of MO onto heat-treated palygorskite clay is controlled by the two mechanisms: for samples treated at lower temperatures (<300 °C), the hydrogen bonding between oxygen groups of −SO3– (anionic head groups of MO) and H+ of both the bound zeolitic water and coordinated water should be important. While for samples calcined at higher temperature (>400 °C), electrostatic interaction between the dye–Mg2+ complexes and negatively charged surface of heat-treated palygorskite clay becomes dominant. In addition, the latter becomes stronger with the increasing the calcination temperature, which can be ascribed to the formation of a higher ratio of complexes and stronger negatively charged surface of the adsorbent caused by leaching of more metal ions. This work provides a deep insight into the interaction of heat-treated palygorskite clay and anionic dye, which paves the way for their practical applications in anionic dye adsorption.

The properties of bioactive TiO2 coatings on Ti-based implants

We report a method for the one-step synthesis of a thin layer of anatase TiO2 on Ti6Al4V alloy for the improvement of short-term and long-term body responses. In particular, this method decreases the direct contact between bone tissue and metals, especially aluminium and vanadium, and improves bone osseointegration. The coating was prepared by hydrothermal synthesis in the presence of titanium ions. Morphology advantageous for bioactivity and photocatalytic properties were achieved by using the appropriate dopants and surface-active agents during the processing. The coating was composed of pinacoidal anatase grains and strongly attached to the substrate alloy; it improved hydrophilicity and reduced the leaching of toxic metal ions. The coating also stimulated the formation of hydroxyapatite when soaked in simulated body fluid solution, which was influenced by different anatase planes.

Heterogeneous catalysis over a barium carboxylate framework compound: Synthesis, X-ray crystal structure and aldol condensation reaction

A new three-dimensional alkaline-earth metal–organic framework (MOF) compound, [Ba(pdc)]n (1) (H2pdc=pyridine-2,5-dicarboxylate), has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction analysis. X-ray single-crystal analysis reveals that each metal ion in compound 1 is coordinated by seven O atoms from seven different carboxylate groups. While each pyridine-2,5-dicarboxylato (pdc2−) ligand coordinates to seven alkaline earth metal centers through two carboxylate groups adopting μ4-η2:η2-bridging and μ3-η2:η1-bridging coordination modes to afford a 3D network. Thermogravimetric analysis reveals that compound 1 is thermally stable up to around 560°C. Compound 1 efficiently catalyzes aldol condensation reactions of various aromatic aldehydes with acetone and cyclohexanone under environment friendly heterogeneous condition, giving remarkable yields (up to 96%) with high selectivity (100%) within a short reaction time (6h). The catalyst was recycled for five successive runs without significant loss of activity. There was no evidence of leaching of metal ions or no loss of structural integrity of the catalyst during the catalytic reaction.

Assessment of total coliform removal and leaching of metal ions from sewage sludge-fly ash mixture at different pH and washing conditions

Effectiveness of fly ash as a stabilising agent for heavy metals leaching was studied for different ratios of sewage sludge (SS)-fly ash (FA) mixtures at different pH and washing conditions. The supernatant liquid was analysed for total coliforms. The results obtained from the microbiological analysis of 1:1, 4:1, 1:4 sewage sludge and fly ash ratios showed that the initial concentration of total coliforms was 2.4 × 104 MPN/100ml, 150 MPN/100ml and 120 MPN/100ml which were finally reduced to 28, 4 and 3 with successive washings. The leachate after shaking of the SS:FA mixture were analysed for heavy metals contents and the results showed that the maximum removal of heavy metals was achieved with SS/FA (1:1) mixture, while Co was absent in all the samples. Out of the three pH conditions (5, 6, 7), it was observed that the maximum removal of different heavy metals was achieved at the lower pH (5) conditions. Key words: Fly ash, sewage sludge stabiliser, leaching, heavy metals, coliforms.

Toxicity assessment of three-component Fe–Cr–Ni biomedical materials using an augmented simplex design

This study firstly establishes the toxicity assessment of three-component Fe–Cr–Ni biomedical materials using Probit dose–response model and augmented simplex design. The individually determined toxicity rankings of these three cations is in the order Ni2+≥Cr3+>Fe3+. The ternary Fe–Cr–Ni system's EC50 contour plot shows a hump with EC50=897.5mg/L, and a saddle with EC50=637.5mg/L. Ternary Fe–Cr–Ni biomedical implants may possess good biocompatibility when the chemical compositions of selectively leached metal ions approach the hump region, but present at increased toxic risk when close to the saddle region. Toxicity of Fe–Cr–Ni three-component biomedical materials with various chemical compositions can be predicted and verified economically and efficiently using an augmented simplex design.

Modification in Properties of Fly Ash through Mechanical and Chemical Activation

This paper is a critical overview on chemical, structural, and morphological changes in fly ash properties with mechanical activation using high energy planetary ball mill and chemical activation by digesting with various mineral acids (HCl, HNO3, H2SO4 and HClO4) at 110oC. Mechanical activation results in increase in silica percentage, amorphous nature, specific surface area and surface roughness, as evident by analytical measurements using XRF, XRD, FT-IR, BET surface area and SEM techniques. The chemical activation of Fly ash performed by different acids results in increased silica content and surface area due to leaching of several metal ions from silico-aluminate skeleton. The surface silanol groups responsible for generating Bronsted acidity are enhanced as evident by pyridine adsorbed FT-IR. Activation with HClO4 is also evident to generate surface active Lewis acid sites due to formation of Al-OH phases on the surface. The mechano-chemical activation can generate sufficient activity on fly ash surface rendering its potential application in heterogeneous acid catalysis.

γ-Al2−xMxO3±y (M = Ti4+ through Ga3+): potential pseudo-3D mesoporous materials with tunable acidity and electronic structure

A simple and highly efficient surfactant-free sol–gel process has been developed to obtain nanocrystalline mesoporous γ-Al2O3 and metal ion incorporated mesoporous γ-Al2O3 with general formula γ-Al2−xMxO3±y (where M = Ti4+ through Ga3+). Any one of the first row transition metal (TM) ions along with Ga3+ could be introduced into the γ-Al2O3 framework in a direct one-pot synthesis process. The generality of the present synthesis recipe for metal ion incorporation in γ-Al2O3 was demonstrated by preparation of an Al–Ga–M ternary oxide system with the metal ion composition of general formula Al9GaTM (TM = Ti4+ to Zn2+) and their characterization through various physicochemical and spectroscopic techniques. The mesoporous γ-Al2−xMxO3±y materials showed a BET surface area in the range of 200–400 m2 g−1 with a narrow pore size distribution. Wormhole mesoporosity makes the material pseudo-3D (p3D) with a small pore depth of few nm (<10 nm). Metal ions in γ-Al2O3 lead to changes in the acidity and electronic environment. XRD, TEM, and 27Al MAS NMR studies demonstrate that the sol–gel process and the disordered mesoporous structure allow Ga and TM ions to be highly distributed and integrated in the γ-Al2O3 framework. The efficacy of these materials in catalysis has been successfully evaluated for steam reforming of dimethylether: Ni, Cu and Zn containing Al9GaTM oxides showed high activity and stability. The smaller mesochannel depth (<10 nm) and pseudo-3D characteristics that arise due to the wormhole-type disordered mesoporous framework of these alumina materials facilitate mass transport through them without any leaching of metal ions out of the lattice and pore blocking during the reaction, which makes them attractive in catalysis. This preparation method is versatile enough to be used for a reproducible synthesis of metal ion incorporated mesoporous γ-Al2O3 by varying the metal content and their combinations, and it is expected that many other metal ions could be introduced into the lattice framework for a variety of applications by tuning acidity and electronic structure.

English

The present study was done to check the bioleaching feasibility of brown shale for the recovery of copper (Cu), aluminum (Al), magnesium (Mg) and manganese (Mn) ions using Ganoderma lucidum. Different experimental parameters were optimized for the enhanced recovery of metals ions. Effect of different substrates like glucose, molasses, saw dust and cotton seed cake on the recovery of metals ions was investigated under shaking as well as non-shaking conditions. Significant difference in leaching of metal ions by G. lucidum was observed under shaking and non shaking conditions. Maximum leaching of Al (90.7%), Mg (96.46%), Mn (66.3%) and Cu (73.45%) was observed using glucose under shaking conditions with 5, 3, 4 and 3% pulp densities respectively. The results show that maximum solubilization up to 68.89, 77.03 and 38.37% was achieved for Cu, Al and Mg ions respectively using molasses as substrate, whereas, 57.74% recovery of Mn was achieved with saw dust. The recovery of metal ions indicated that this low grade discarded ore may be a potential source of metal ions in future.

Assessment of Corrosion Resistance and Metal Ion Leaching of Nitinol Alloys.

Nitinol usage for biomedical implant devices has received significant attention due to its high corrosion resistance and biocompatibility. However, surface treatments are known to affect surface charge, surface chemistry, morphology, wettability, and corrosion resistance. In this investigation, the corrosion resistance of a binary and various ternary Nitinol alloys was determined after being subjected to electropolishing, magnetoelectropolishing, and water boiling and passivation. Cyclic polarization in vitro corrosion tests were conducted in Phosphate Buffer Saline (PBS) in compliance with ASTM F 2129-08 before and after surface treatments. The concentrations of dissolved metal ions in the electrolyte were also determined by ICPMS.

Corrosion and Biocompatibility Assessment of Magnesium Alloys

Magnesium due to its good biocompatibility, mechanical properties, necessity in metabolic processes and lightness in weight, is an ideal candidate for biodegradable implants. The major concerns with magnesium and its alloys are that of rapid and non-uniform corrosion. In this investigation, magnesium based binary, ternary and quaternary alloys were studied for their corrosion resistance and biocompatibility. In vitro corrosion resistance of the alloys was studied in accordance with ASTM G 102-89in phosphate buffered saline (PBS) at 37°C. The surface morphology of the alloys was studied using scanning electron microscopy (SEM) and the wettability of the alloys was determined by contact angle measurements. Additionally, the cytotoxicity of the leached metal ions on the viability of osteoblast was evaluated bysulforhodamine B (SRB) assay.

Batch is bad? Leaching of Opalinus clay samples and ICP-MS determination of extracted elements

Geological clay formations are often considered as a host rock for a future waste repository. Many studies concerning sorption or desorption experiments of radionuclides or other toxic metals onto/from geological samples like clay are performed with batch techniques where only small amounts of the homogenised clay samples are in contact with the appropriate metals diluted in high volumes of aqueous solutions. This can lead to a high leaching of metal ions originating from the clay. The leached elements can considerably increase the background concentration of many isotopes, and they may also influence the results of the sorption/desorption experiments due to their competition with the used metal ions. This study focuses on this problem by analysing element leaching of clay during the batch procedure. After characterisation of the used Opalinus clay (OPA), element leaching was performed by extraction of homogenised clay samples from a bore hole with two different leaching solutions, Milli-Q water and, in contrast, synthetic porewater (PW) with a high ionic strength. After centrifugation, the leached elements in the supernatant were analysed by inductively coupled plasma-mass spectrometry (ICP-MS). Depending on the used extraction solution different elemental compositions in the leachate can be determined. The leaching of OPA with Milli-Q water leads to a dissolution of mainly anionic element species, whereas the use of PW leads to a release of mainly cationic metal ions. In particular, metals like Al, Fe, V, Cr, Co, Ni, Sr, Ba and U (beside the present PW ions) can be found in the leachates.

Analyses of Heavy Metals in Mineral Trioxide Aggregate and Portland Cement

Introduction Portland cement is used in the construction industry as a binder in concrete. It is manufactured from chalk, limestone, and clay, which are clinkered at very high temperatures and ground with gypsum to form Portland cement. The raw materials and the manufacturing process can result in the inclusion of heavy metals in Portland cement. Portland cement with a four to one addition of bismuth oxide is marketed as mineral trioxide aggregate (MTA), which is used mainly as a dental material. Heavy metal inclusion can be of concern because MTA is in contact with hard and soft tissues. Methods Measurements of arsenic, lead, and chromium in hydrated gray and white Portland cement, ProRoot MTA, and MTA Angelus were conducted with graphite furnace atomic absorption spectrophotometry after acid digestion on the hydrated material. The leaching of the metal ions from the solid material in water and simulated body fluid (SBF) was also determined. Results All cement types showed high relative values of leached chromium compared with arsenic and lead in both the total metal content and leached species. The gray Portland cement showed the highest total amount of metal. The white Portland and both MTAs had lower values for all the leached metal ions. Conclusions Both MTAs released more arsenic than the amount specified in ISO 9917-1 (2007). Portland cements and MTAs showed evidence of heavy metals in the acid-soluble form as well as leaching in deionized water and SBF. MTA contained levels of arsenic higher than the safe limit specified by the ISO 9917-1 (2007).

Chitosan-Type Bioadditive-Modified Electronic Industry Waste Sludge for Heavy Metal Stabilization with Assistance of Microwave Heating

Cement solidification is used as the common method for stabilizing industrial wastewater sludge in Taiwan. However, this method has the disadvantage of increasing the volume of waste. In contrast, chitosan-type biopolymer is used by several researchers for biosorption applications and dye discoloration in aqueous solutions. Therefore, in this study, commercially available low-cost chitosan-type material was used as an alternative bioadditive to stabilize the leaching of heavy metal ions in industrial sludge. The effects of additive dosage amount, power of microwave irradiation, and reaction time were studied. The heavy metal leaching capacity was determined using a standard TCLP test, and the elemental content in the leachate was analyzed by ICP. It was found that chitosan effectively stabilizes copper ions with higher selectivity in the presence of microwave irradiation and other toxic heavy metal ions. The optimized additive mixing in industrial sludge for the control of the leaching of copper and other heavy metal ions was found to be <5 mg L−1 after a microwave heating process in nitrogen atmosphere rather than air. Complete stabilization was achieved for chromium and cadmium (not detected after a TCLP test) compared to other heavy metal ions. The heavy-metal-ion-stabilized sludge was further tested for dye discoloration efficiency. Chitosan-modified sludge exhibited complete discoloration for the dye compounds methlylene blue and acid red 114.

Sorption of toxic metals on sodium aluminosilicate (NAS)

The present study describes sorption of toxic metal ions viz: Hg 2+, Pb 2+, Cd 2+, Zn 2+ and As 3+ onto synthesized sodium aluminosilicate. A series of experiments were carried out in different conditions. Time of equilibration was observed for 5 h through kinetic study. Sorption was found to be pH dependent. In the case of Hg 2+, sorption was observed to be decreased by increasing the pH whereas it gradually increased with pH with respect to other metal ions. Sorption was observed to be decreased with the increase in metal ion concentration (10 − 2 M to 10 − 5 M) and the data was fitted well in Freundlich's isotherm. A thermodynamic study showed spontaneity of the sorption. Positive values of enthalpy and entropy indicate endothermic and increase in order of randomness at the solid–solution interface during sorption. A desorption study showed that distilled water has no capability of leaching metal ions in contrast with organic ones. The MINTEQA-2 software has been used for the aqueous speciation of the metal ions. Speciation data showed the presence of different species at different pH.

Application of thermal plasma to vitrify fly ash from municipal solid waste incinerators

Several fly ash samples collected from different municipal solid waste incinerator plants were vitrified using thermal plasma furnace at 1400–1500 °C. After vitrification, there are obvious changes in microstructures and crystalline phases between produced slag and original ash. Toxicity characteristic leaching procedure results show that there is an excellent resistance against leaching of heavy metal ions. The residual fractions of heavy metals in slag presumably decrease in the following sequence: Cr > Ni > Cu > Zn > Pb > Cd. Almost all of PCDD/Fs could be destroyed through thermal plasma treatment. And the average decomposition efficiency of the samples vitrified by thermal plasma furnace is 100% in toxic equivalent calculations, higher than that of the samples vitrified by conventional resistance furnace.

Thermal treatment of municipal solid waste incinerator fly ash using DC double arc argon plasma

In this study, glassy slag was produced by melting fly ash samples without any additives in a thermal plasma reactor, the core of which was a DC double anode plasma torch. After vitrification, there was an obvious change in the microstructural and the mineralogical characterization, an excellent resistance against leaching of heavy metal ions and a significant decomposition rate (99.95%) of PCDD/Fs in TEQ in the produced slag. These results indicate that the thermal plasma vitrification is an alternative technology with high efficiency and energy to dispose MSWI fly ash.