Concentration Of Metal Ions In Solution Research Articles

Modeling and Optimization of Heavy Metals Biosorption by Low-Cost Sorbents Using Response Surface Methodology

This paper exploits, through modeling and optimization, the experimental laboratory data on the biosorption of heavy metal ions Pb(II), Cd(II), and Zn(II) from aqueous media using soybean and soybean waste biomasses. The biosorption modeling was performed using the Response Surface Methodology, followed by optimization based on numerical methods. The aim of the modeling was to establish the most probable mathematical relationship between the dependent variables (the biosorption efficiency of the biosorbents when adsorbing metal ions, R(%), and the biosorption capacity of sorbents, q(mg/g)) and the process parameters (pH; sorbent dose, DS (g/L); initial metal ion concentration in solution, c0 (mg/L); contact time, tc (min); temperature, T (°C)), validated by methodologies specific to the multiple regression analysis. Afterward, sets of solutions were obtained through optimization that correlate various values of the process parameters to maximize the objective function. These solutions also confirmed the performance of soybean waste biomass in the removal of heavy metal ions from polluted aqueous effluents. The results were validated experimentally.

BIOSORPTION OF Pb(II) AND Cu(II) IONS FROM AQUEOUS SOLUTION USING COFFEE SENNA (Senna occidentalis) LEAVES AS BIOMASS

Conventional reagents for the remediation of heavy metals from wastewaters are expensive. Plant materials are being investigated to serve as alternative. The potential of Senna occidentalis leaves in removing Pb (II) and Cu (II) ions from aqueous solution was investigated using Batch adsorption method. The process was subjected to different experimental conditions such as initial metal concentration, solution pH, contact time, biosorbent dose, temperature and shaking speed. Atomic absorption spectroscopy (AAS) was employed in the determination of metal ion concentrations in solution after agitation, and characterization of plant biomass was done using infrared (IR) and scanning electron microscopy (SEM) analytical techniques. The adsorption process vary with the pH of the reaction medium. The optimum adsorption of Pb (II) and Cu (II) ions was achieved at pH 6 and 4 with percent uptake recorded at 97.70% and 82.32% respectively. At optimum temperatures of 40oC & 60oC for Pb (II) and Cu (II) ions, reaction equilibrium was attained after 120 min and 90 min of contact with 20 mg and 40 mg doses of the biomass respectively. The adsorption data for Pb (II) ion fitted well to Langmuir, Freundlich, Temkin and Dubbinin-Radushkevich isotherms. However, Cu (II) ion adsorption mechanism showed exception to Langmuir adsorption isotherm. The plant material was found to be effective in removing Pb (II) and Cu (II) ions and thus, can serve as a substitute for costly adsorbents in the remediation of Pb (II) and Cu (II) ions from wastewaters.

Preliminary Study on The Development of Preconcentration Method of Cu(II), Co(II), Ni(II), and Cr(III) Ions in Water Samples Using Nanomagnetite Coated by Carboxymethyl kappa-Carrageenan (CMKC)

Flame Atomic Adsorption Spectrophotometry (FAAS) is one of the instruments that is often used to determine metal ion concentration in solution. FAAS uses simple operational procedure for metal ions concentration determination and produces accurate metal ion concentrations. Unfortunately, the accuracy of metal ion determination test decreases if the concentration of metal ions is too low, whereas the threshold for metal ions in drinking water is very low. Preconcentration is a method for increasing the concentration of metal ions in sample. An effective preconcentration method needs to be studied to improve the accuracy in the determination of metal ions concentration in water at low concentration using FAAS. This research aims to determine the effectiveness of metal ions preconcentration in water samples using nanomagnetite coated by CMKC. The research was conducted in four stages, 1) synthesis of nanomagnetite coated by CMKC; 2) preconcentration of samples containing Cu(II), Co(II), Ni(II), and Cr(III); 3) measurement of metal ion concentration with FAAS; 4) effectivity of preconcentration process and preconcentration optimum conditions. The result showed that nanomagnetite coated by CMKC can be used to preconcentration of metal ions Cu(II), Co(II), Ni(II), and Cr(III) in water samples by utilizing desorption-adsorption mechanism. Desorption was done using 0.1 N HNO3 as a desorption solvent without variation in concentration and desorption time preconcentration optimum conditions for each metal ion were as follows, adsorption condition of Ni(II) was pH 7 and 60 minutes; Cr(III) was pH 7 and 40 minutes; Co(II) was pH 7 and 60 minutes; Cu(II) pH 6 and 40 minutes. The effectiveness of preconcentration at optimum conditions for each metal ions are: %Cr(III) > %Cu(II) > % Co(II) > %Ni(II), successively.

Operando XAS and UV-Vis Characterization of the Photodynamic Spiropyran-Zinc Complexes.

Thermal and photoinduced processes accompanying complexation of photochromic spiropyrans (SPP) with Zn ions in acetone solution were characterized by means of UV-vis and X-ray absorption spectroscopies in operando regime. SPP ligands are usually transparent at λ > 350 nm, but after mixing with Zn ions, they produce a stable colored (ε = 32 000-38 000 M-1 cm-1) complex with maximum absorption at 525 nm, which makes them a powerful tool for monitoring metal-ion concentration in solution. The complex revealed fluorescence and photochromic behavior under static irradiation with visible light with constant photoreaction quantum yield across its characteristic absorption band. Zn K-edge X-ray absorption spectra show prominent changes in Zn local atomic structure between free Zn ions and Zn complex. The pump-flow-probe scheme was adapted to measure operando changes in Zn coordination upon light irradiation. Within experimental time resolution, we have determined that 20 μs after light irradiation, Zn ion is released out of the complex. This is the first example of the direct spectroscopic probe of the Zn photorelease from the spiropyran complex.

Role of Manglicolous fungi isolated from Indian Sunderban mangrove forest for the treatment of metal containing solution: Batch and optimization using response surface methodology

Abstract Lead and Cadmium are known for their various carcinogen effects in various biotic components. In the present study, manglicolous fungi isolated from the Indian Sunderban region were utilized for the removal of lead and cadmium from its aqueous solution. Six fungal strains were isolated from the water samples collected from the intertidal zone of Jharkhali, an island of Indian Sunderban region, which were then screened for their potentiality for the removal of lead and cadmium. Of all the isolated strain, one fungal strain which was molecularly identified to be Alternaria alternata showed promising result in the removal of lead and cadmium. The removal efficiency of Alternaria alternata from the aqueous solution of Lead and Cadmium were optimized using different conditions like initial concentration of heavy metal, contact time, biomass dose, pH, temperature and salinity. Competitive biosorption capacity of the fungal species were also investigated by mixing the two metal in effluent solution where the removal capacity of each metal ion were reduced due to the presence of other metal ion and also the removal efficiency decreases with increase of competitive metal ion concentration in solution. Further, the removal of these heavy metals were also optimized using Response Surface Methodology (RSM). It was observed that Alternaria alternata could remove 98.27% and 84.64% of lead and cadmium respectively from the initial metal-ion solution. This research indicated that fungi obtained from mangrove growing area of Sunderban region has biosorption potential and can be used to remove heavy metal-ions from the wastewater.

Morphology Matters: Additive-Assisted Metal Foam Deposition for the Electrochemical CO2 Conversion

High-surface area metal foam catalysts for the electrochemical CO2 reduction reaction (ec-CO2RR) are deposited on planar model substrates and technical supports (e.g. 2D mesh or 3D sponges). The metal deposition is typically carried from acidified plating baths at particularly high current densities (e.g. -3 A/cm2) where the metal deposition is superimposed on the hydrogen evolution reaction (HER). Gas bubbles formed on the support surface serve as geometrical template for the metal deposition leaving highly porous metal foams behind.1,2 Pore density and the particular side-wall morphology of these foams can be fine-tuned not only by the current density, metal ion concentration in solution but also by the use of particular polymeric plating additives (e.g. polyethylene-imines, PVPs, polymerizates of imidazole and epichlorohydrin). The activity and product selectivity of the electrochemical reduction of CO2 on Cu foam catalysts strongly depend on the resulting pore size distribution of the Cu catalyst. The maximum in the C-C coupling efficiency (FEC2 = 55%) observed for pore size dimensions in the range of 50 to 100 µm. Such morphology dependence of the ec-CO2RR product distribution will be discussed not only on the basis of the availability of certain reactive surface sites and facets but also on the basis of a temporal trapping of gaseous intermediates (in particular CO and C2H4) inside the mesoporous catalyst material. Mild thermal annealing (300°C, 1h) of the Cu metal foams activates them for the production of C2 and C3 alcohols (ethanol, n-propanol). Identical location (IL) HR-SEM, HR-TEM, white-light interferometry and 3D optical microscopy are applied to probe morphological changes on different length scales that are induced by the foam activation (e.g. by thermal annealing) and the ec-CO2RR itself. This study indicates that the catalyst morphology might undergo drastic changes under operando conditions. [1] Shin, H. C.; Liu, M. L., Chem. Mater. 2004, 16 (25), 5460-5464. [2] Shin, H. C.; Dong, J.; Liu, M. L., Adv. Mater. 2004, 16 (3), 237-240.

Functionalized halloysite nanotubes for enhanced removal of lead(II) ions from aqueous solutions

In this study, environmental friendly halloysite nanotubes and their amino derivatives were used as adsorbent materials for lead(II) ions. The adsorption ability of both nanomaterials towards Pb2+ ions has been studied in NaClaq, at I = 0.1 mol L−1, in the pH range 3–6. Moreover, the effect of ionic strength on the adsorption process was evaluated at the pH of maximum efficiency of the adsorbent materials. Kinetic and equilibrium experiments were carried out by using the Differential Pulse Anodic Stripping Voltammetry (DP-ASV) technique to check the metal ion concentration in solution after contact with the two adsorbents. Different isotherm and kinetic equations were used to fit the experimental data. The speciation of metal ion and the characterization of the adsorbents with different techniques were considered in order to establish the suitable experimental conditions for the metal ion removal. The collected data showed that the functionalization of halloysite enhances the adsorption ability of the clay mineral and it makes the nanoclay a good candidate for metal removal from aqueous solutions.

Heavy metal ions removal from waste water bythe natural zeolites

The removal of cobalt, zinc and manganese from aqueous solutions by natural zeolites has been examined using the batch method.The heavy metal ion concentrations in solution ranging from 50 to 400 mg/l were used. The extraction efficiency of natural zeolites for metal ions observed higher at the lower concentration. The results of extraction efficiency (%R) and the distribution ratio (Kd) increases with decreasing ion concentration in solutions. It is clear from these results that the Mordenite is a potential candidate for removal of Co2+, Zn2+ and Mn2+ ions from wastewater than the Stilbite and Heulandite. The extraction efficiency value for Co2+is observed highest forMordenite at a concentration of 50 mg/l. Present results suggest that natural zeolites can be removed heavy metal ions from wastewater effectively

Coordination Kinetics of Different Metal Ions with the Amidoximated Polyacrylonitrile Nanofibrous Membranes and Catalytic Behaviors of their Complexes

Two transition metal ions (Fe3+ and Cu2+) and a rare earth metal ion (Ce3+) were selected to coordinate with amidoximated polyacrylonitrile (PAN) nanofibrous membrane for preparing three metal modified PAN nanofibrous membrane complexes (M‐AO‐n‐PANs, M = Fe, Cu, or Ce) as the heterogeneous Fenton catalysts for the dye degradation in water under visible irradiation. The coordination kinetics of three metal ions with modified PAN nanofibrous membranes was studied and the catalytic properties of the resulting complexes were also compared. The results indicated that increasing metal ion concentrations in solution or higher coordination temperature led to a significant increase in metal content, particularly in Fe and Cu contents of the complexes. Their coordination process could be described using Langmuir isotherm and pseudo‐second‐order kinetic equations. Moreover, Fe‐AO‐n‐PAN had the best photocatalytic efficiency for the dye degradation in acidic medium, but a lower photocatalytic activity than Cu‐AO‐n‐PAN in alkali medium.

Mixture toxicity of copper, cadmium, and zinc to barley seedlings is not explained by antioxidant and oxidative stress biomarkers.

The analysis of metal mixture toxicity to plants is complicated by mutual interactions. In the present study, mixture effects of zinc (Zn), cadmium (Cd), and copper (Cu) on barley (Hordeum vulgare L.) root elongation were analyzed using oxidative stress parameters. The hypothesis was that toxic mixture effects on plant growth are better explained by biochemical parameters than by exposure information, because the former excludes interactions among metals for root uptake. Barley seedlings were exposed for 5 d or 14 d to these metals in nutrient solutions, added in isolation and as mixtures. Root elongation in Cu+Cd mixtures was well predicted from free metal ion concentrations in solution, using concentration addition (CA) or independent action (IA) reference models. In contrast, Zn acted antagonistically when combined with Cu and/or Cd, relative to both CA and IA. This protective effect of Zn correlated with the biomarkers measured in the long-term experiment; oxidative stress (indicated by malondialdehyde level, for example) decreased after addition of Zn. In addition, it was found that some biomarkers were sensitive to both Cu and Cd dosed in isolation, but not to Cu+Cd mixtures. Overall, the exposure explained mixture effects better than most of the 16 measured biomarkers (i.e., the biochemical effects). It is concluded that these biomarkers are not robust indicators for metal mixture toxicity, potentially because different metals have different parallel modes of action on growth that are insufficiently indexed by the biomarkers. Environ Toxicol Chem 2017;36:220-230. © 2016 SETAC.

Real Time Measurement of Biosorption Efficiency of Chemically Modified Coconut Powder for Pb(II) and Cd(II) Using Open Circuit Potential

The present communication reports a new method for the potentiometric determination of adsorbent efficiency of coconut shell powder for removal of lead and cadmium from water. A three-electrode system containing metal-coated copper wire electrode was used as a working electrode. At equilibrium Open Circuit Potential (OCP) values represents metal ion concentration in solution. With the addition of coconut powder an appreciable decrease in the OCP was observed, which is associated with the reduction of the metal ion concentration due to the uptake of metal ions by the coconut powder. Chemical modification of coconut biomass was carried out by graft co-polymerization of acrylic acid. Modified biopolymer has been characterized using FTIR technique. An increase in the adsorbent efficiency of the biomass was observed by graft-copolymerized biopolymer i.e. from 54.4 mg/g to 122.1 mg/g and 58.8 mg/g to 141 mg/g respectively for Pb (II) and Cd (II) ions. The OCP based method provides an easy and simple approach for real time measurement of adsorption efficiency, which is a low cost and less time consuming process.

Modelling the dynamic growth of copper and zinc dendritic deposits under the galvanostatic electrolysis conditions

This paper investigates the process of crystallisation of the copper and zinc dendritic deposits under galvanostatic conditions on the rod electrode. The effect of the value of current and metal ion concentration in solutions on the growth dynamics of loose deposits is studied. It is shown that the current efficiency of the metal increases, and the growth rate decreases during the elongation of dendritic particles, and an increase in the surface area on which the electrocrystallisation takes place. Empirical equations for the quantitative description of changes in time of the lengths of the dendrites and the current efficiency of copper and zinc are proposed, which well approximate the experimental data obtained under various conditions of electrolysis.A phenomenological model is worked out that helps to calculate the variation of structural parameters in time (the number and the radius of tips of the dendrite branches) of the loose deposit growth and to determine the moment of transition from a loose deposit to a compact one.

Hydrothermal Synthesis of Ni-Fe Layered Double Hydroxide with High Crystallinity Using Homogeneous Precipitation Method

Ni-Fe layered double hydroxide containing carbonate anion (CO32- ) has been successfully synthesized by a process of homogeneous precipitation involving urea hydrolysis under hydrothermal conditions. Factors that influence the composition and the crystallinity degree of NiFe-LDH, such as the molar fraction of urea/NO3- in solution, the total metal ion concentration in solution and the aging time, have been investigated in detail. Structure and morphology of the sample were characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectra and scanning electron microscope (SEM). The results indicate NiFe-LDH with high purity present well-crystalline, uniform crystallite size

Preparation of a Modified PTFE Fibrous Photo-Fenton Catalyst and Its Optimization towards the Degradation of Organic Dye

Polytetrafluoroethylene (PTFE) fiber was grafted with acrylic acid to impart the carboxyl groups onto the fiber surface, which were used to coordinate with both transition metal ions Fe(III) and Cu(II) and a rare metal ion Ce(III) to prepare the metal grafted PTFE fiber complexes as the novel heterogeneous Fenton catalysts for the degradation of the azo dye in water under visible irradiation. Some factors affecting the preparation process, such as nature and concentration of metal ions in the coordination solution, grafting degree of PTFE and reaction temperature were optimized with respect to the content and strength of metal fixation on the fiber and dye degradation efficiency. The results indicated that increasing metal ion concentrations in solution and grafting degree of PTFE fiber as well as higher coordination temperature led to a significant increase in metal content, especially Fe(III) and Cu(II) content of the complexes. Fe(III) ions fixed on the fiber showed the better catalytic performance than Cu(II) and Ce(III) ions fixed when three different complexes with similar metal content being employed, respectively. Moreover, Increasing Fe content or incorporation of Cu(II) ions could significantly improve the catalytic activity of the complexes.

The evolution and analysis of electrical percolation threshold in nanometer scale thin films deposited by electroless plating

Extension of Ultra Large Scale Integration (ULSI) to a nanometer scale elevates the importance of interconnect resistivity in addition to conventional problems of coverage and electromigration. In this work we study electrical properties of ultra thin silver (Ag) and copper (Cu) films prepared by electroless deposition (ELD) in order to provide low resistivity, stable interconnect metallization technology and electrical contacts. The thin film is modeled by assuming metal conducting clusters separated by empty dielectric gaps. The continuity of the film or gap size is controlled by film thickness with respect to the growth mode of each metal. Analysis of the electrical properties of thin films at percolation threshold demonstrates that insulator–conductor transition occurs at the thickness about 35 nm and 30 nm for Ag and Cu films, respectively. At these thicknesses film roughness is constant, therefore, scattering on film walls remains unaffected and resistivity change can be associated with a percolation mechanism. The resistivity as a function of thickness varies according to power law and reaches saturation value of 2.5 μΩ cm and 4.3 μΩ cm at the thicknesses of 60 nm and 50 nm with critical exponents ( τ) of 0.95 and 1.04 for Ag and Cu thin films, respectively. The X-ray Photoelectron Spectroscopy analysis has not detected contaminations or oxidation states. The strong dependence of the film surface roughness on metal ion concentration in solution was observed while the deposition rate and the resistivity remain unaffected.

Experimental and Modeling Study of Nickel Electrodeposition Including H + and Water Reduction and Homogeneous Reactions

A comprehensive physicochemical model is presented for nickel electrodeposition onto nickel and copper rotating disk electrodes in sulfate media buffered with boric acid at various concentrations. The model accounts for three contributions comprising the total current: nickel deposition, reduction, and water reduction. Also considered are homogeneous reactions and transport of dissolved species to and from the electrode by diffusion and convection. The model is statistically fit to experimental linear sweep voltammetry data to obtain the various kinetic parameters. It is not possible to satisfactorily fit the curves obtained on a nickel substrate for the different concentrations with a single set of parameters. Analysis of the experimental data and fitted model shows that the cathodic reactions reach completion in the following order as the potential becomes more negative during the scans: reduction, nickel deposition, and water reduction. The extent of water reduction during scans does not vary with the metal ion concentration in solutions containing or more, but increases when the concentration is reduced to . The model confirms that hydrolysis mitigates the increase of the surface due to and water reduction.

Sorption properties of new nitrogen-containing wood-based ion exchangers with respect to gold(III) ions

Sorption properties of new nitrogen-containing wood-based ion exchangers with respect to gold(III) ions were examined in relation to the metal ion concentration in solution, pH of medium, and sorption temperature and time. The rate-limiting steps in the process were identified. The mechanism of sorption of aurate ions from solutions was considered in relation to their acidity.

An Investigation of Commercial Grade 2 Titanium as a Bipolar Plate Material for PEM Fuel Cells

Bipolar plates are one of the most important components in PEM fuel cell stacks. Currently, the commercial bipolar plates are made of non-porous graphite because of its chemical and thermal stability. However, they account for about 80% of the total weight and 45% of stack cost. In this study, commercial grade 2 titanium has been investigated as a possible bipolar plate material because its excellent corrosion resistance and relatively low density. Potentiodynamic, potentiostatic tests and EIS measurements were done to investigate the corrosion resistance in the simulated anode and cathode environments of a PEM fuel cell. SEM metallography was conducted to determine the corrosion morphology. ICP-OES tests were done to determine the metal ion concentrations in solution after corrosion. The Ti ion concentration in solution would be about 20ppm after 5000 hour operation at both the anode and the cathode.

Kinetic studies on visible light-assisted degradation of acid red 88 in presence of metal-ion coupled oxone reagent

Visible light-assisted photo-Fenton-like oxidation of a mono-azo textile dye, acid red 88 (AR88), has been carried out in presence of Cu2+ or Fe3+ ions as the catalyst and oxone as the oxidant. The optimal concentrations of metal-ion (Cu2+ or Fe3+) and oxidant (oxone) for the abatement of the azo dye were determined. Decolorization of AR88 in Cu2+/oxone system was found to follow zero-order kinetics with respect to the dye and first-order kinetics when Fe3+/oxone system was employed. In both the cases, the decolorization of AR88 was found to be accelerated with increasing concentrations of metal-ions in solution. Almost 95% decolorization was attained in 2h with Cu2+ ion and within 14min with Fe3+ at each metal-ion concentration of 0.075mM. Mineralization studies were also carried out by monitoring the reduction of total organic carbon (TOC) content during the course of the reaction. A suitable mechanism has been proposed to explain the observed kinetics of decolorization of AR88 in both the Fe3+/oxone and Cu2+/oxone systems.

An investigation into the effects of a nano-thick gold interlayer on polypyrrole coatings on 316L stainless steel for the bipolar plates of PEM fuel cells

Polypyrrole is one of the most important conductive polymers because it is easily oxidized, water soluble and commercially available. Also, polypyrrole coatings have potential applications in batteries, fuel cells, electrochemical sensors, anti-corrosion coatings and drug delivery systems. In this study, a very thin gold layer was first coated on SS316L, and then a polypyrrole coating was laid on top. The nucleation and growth mechanisms of polypyrrole on the gold-coated SS316L were studied by electrochemical nucleation and growth techniques. SEM was used to characterize the polypyrrole coating morphology. Potentiodynamic tests were performed to determine the corrosion parameters of the polypyrrole coatings. Potentiostatic tests of the coated SS316L were conducted in simulated anode and cathode environments of a PEM fuel cell. The simulated anode environment was at a potential of about −0.1 V versus SCE purged with H 2 and the simulated cathode environment was at a potential of about 0.6 V versus SCE purged with O 2. After coating with Au and polypyrrole, the polarization resistance of SS316L is increased about six times, and the corrosion current density is decreased about seven times, compared to the base SS316L. Also, our calculations show that the metal ion concentration in solution for the polypyrrole/Au/SS316L had met the target of 10 ppm after 5000 h fuel cell operation.