The purpose of this work is to investigate the batch removal of Pb2+ from aqueous solutions using marine dried brown seaweed S. baccularia. Seaweed was used as a low-cost adsorbent. The effects of pH, contact time, temperature, shaking speed and the concentration of the Pb2+ solution were examined in the biosorption process with S. baccularia. The results showed that when S. baccularia was used as the bioadsorbent, the optimum pH, Pb2+ concentration, equilibrium time, temperature, and shaking speed were 3, 20 ppm, 120 min, 30°C, and 120rpm. The equilibrium adsorption data are fitted to the Langmuir isotherm model. The separation factor (RL) in the experiment was less than one (<1), indicating that the adsorption of metal ions on Sargassum baccularia adsorbent is favorable. The calculated activation energy (Ea) implies that the adsorption of Pb (II) on brown seaweed is a physical adsorption. Thermodynamic results show that adsorption occurs spontaneously in nature.

We have described the development of electrochemical nano sensor for the detection of total arsenic in groundwater, soil, food and honey samples based on the formation of gold nanoparticles. Screen printed carbon electrodes were modified with gold nanoparticles and linked with 1,6-hexanedithiol self-assembled monolayers. The electrodeposition of Au nanoparticles was applied in 10 mL of the solution that totally cover the screen-printed carbon electrode while applying a constant potential of –0.4 V (vs. Ag within SPCE) for 600 sec. Cyclic voltammetry was used to characterize the gold nanoparticles before and after modified with 1,6-hexanedithiol self-assembled monolayers on screen printed carbon electrode. Square wave anodic stripping voltammetry with multi point standard addition method was examined for the detection of As(III) and As(V) on Au NPs-1,6-hexanedithiol modified screen printed carbon electrode under optimized conditions. As(III) and As(V) was firstly, deposited for 60 seconds by the reduction of arsenic in buffer solution: (citric acid, sodium chloride and ascorbic acid pH 2.0), followed by As stripping between –0.20 and 0.35 V at the following parameters: scan rate: 100 mV s–1, frequency: 60 Hz, amplitude: 0.025 V and increment: 5.0 mV. it was found that Au-NPs with 1,6-hexanedithiol modified screen-printed carbon electrode had a highest anodic stripping peak current at 0.201 V. The limit of detection value for arsenic was identified to be 1.7 ng ml –1. Also, the electrochemical nanosensor showed excellent reproducibility and high stability. The developed method was successfully applied to detect total arsenic in ground water, soil and honey samples.

Abstract

It has been described the development of electrochemical nano sensor for the detection of mercury ions from aqueous solutions based on the formation of polyaniline nanoparticle films. Screen printed carbon electrodes were modified with polyaniline nanoparticles. Electropolymerization of polyaniline nanoparticles was performed by the pulsed potentiostatic method. The sample of polyaniline nanoparticles was prepared by repeating the potential step process three times. Structural and morploigcal characterization of polyaniline nanoparticles modified screen printed carbon electrode was performed using Fourier Transmission infrared (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). PANI nanoparticles were spherical shaped having an apparent dimeter varying from 20 to 45 nm. Square wave anodic stripping voltammetry was used for the detection of Hg(II) on PANI NPs modified screen printed carbon electrode under optimized conditions. Hg(II) was deposited for 60 seconds by the reduction of Hg(II) in buffer solution:(citric acid and sodium chloride pH 2.30), followed by Hg stripping between 0.3 and 0.8 V at the following parameters: Scan rate: 100 mV s-1, frequency: 60 Hz, amplitude: 0.025 V and increment: 4.0 mV. it was found that the PANI NPs modified screen printed carbon electrode had a highest anodic stripping peak current in solution of pH 2.30. The limit of detection value for Hg(II) was found to be 2.50 ± 0.03 ppb. The limits of detections determined are below the corresponding guideline value from the World Health Organization (WHO). In addition, the modified nano electrode exhibited excellent reproducibility and high stability. The developed method was successfully applied to determine Hg(II) in real water samples with satisfactory results.

This study highlights the mechanism of formation for Bentonite clay surface properties. It investigates specific gravity and the influence of physicochemical characteristics on clay stability of structural forces on adsorbed water molecules. In particular, it describes the chemical composition, as well as cation exchange capacity (CEC). Bentonite clay is collected from the Murzuq city located 1150 km south of Tripoli i.e. southernmost town of Libya. The CEC value is leached by 500ppm Ca+2 at pH=8 equaled 84.5 mmoles/kg. While at pH=2, the value is (20.5 mmoles/kg). The leaching process is carried out by 500ppm K+ using flame emission photometer. The CEC value at pH =8 for sample is 91.5 mmoles/kg. Also the specific gravity is found to be 2.597. This value is in agreement with the obtained standard values for Wyoming (USA). The % MxOy of the clay is calculated by gravimetric method as follows: SiO2, 53.75; Al2O3, 21.46; Fe2O3, 1.4;CaO, 0.97; MgO, 2.13, and agreed with the XRF analysis as follows: SiO2, 54.93; Al2O3, 21.46; Fe2O3, 1.71; MgO, 3.18 ; CaO, 0.81; Na2O, 5.48; K2O, 0.54; TiO2,0.32. The results are adequately approximate and reasonable for both methods. The percent is very limited for trace elements Pb, Cr, Cd, Cu, Fe, and Zn. In the sample, it is about 0.21%. The result of XRD analysis (intensities) for sample is presented as follows: 50% quartz, 50% kaolinite, 5% Analcine, 7.5% Illite, 5% Natrolite, 10% Nontronite, 7% Montmorillonite. The formula calculation depends on the purity of clay and consequently the structural formula for Libyan Bentonite is: K0.094Na1.45Ca0.118 (Al2.92Fe0.175Ti0.033Mg0.646)VI( Al0.52Si7.48 …

Abstract: Monitoring the concentrations of heavy metals in natural and waste water at and below the level of their maximum permissible concentrations is an urgent environmental problem. Hence, new procedures for the preconcentration of heavy metals with their subsequent determination by different methods are required. Along with other sorbents, significant attention is attracted to polymer chelating sorbents, which provide individual or group extraction of trace elements, eliminate matrix effects, and provide high concentration factors. The effect of the various parameters such as electrochemically and chemically synthesis methods, physical oxidation state of the polymer, polymer thickness, solution pH and metal ion concentration on the adsorption, kinetics and efficiency were investigated. The results showed a vary broad concentration range of the heavy metals from (0.05 to 10 mg/L) can be adsorbed on different kinds of polymers at different pH values and different efficiently. The adsorption capacity of the polymer to different concentrations of heavy metals was evaluated as the milligram of metal ions by one gram of various forms of the polymer. The DC conductivity measurements were also employed on the solid polymer before and after adsorption of metal ions. The experimental adsorption date was fitted to different mathematical isotherms to estimate the binding constant of heavy metals with the polymer in both single and mixed ion solutions. The method provides the extraction of analytes from natural water of complex composition containing high concentrations of alkali, alkaline-earth and other elements and is characterized by rapidly, selectivity, low detection limits, and a high reproducibility of the results. The relative standard deviation is 2-4%. The technique was test with real waste water samples.  

The title complex was isolated as a red solid from the reaction of 4-(salicylaldiminato)antipyrine, HL, and cobalt (II) acetate in ethanol. The complex has been characterized by elemental analysis, FTIR, UV-Vis, and X-ray single crystal diffraction. Two crystallographically different cationic units, A and B, of the title complex are found. Both units are essentially isostructural; nevertheless, small differences exist between them. Both units contain four cobalt atoms arranged at the corners of distorted cubane like core alternatively with phenoxy oxygen of the Schiff base. In both cases, one cobalt binds to three coordinated sites from the corresponding tridentate Schiff base ligand, and the fourth one was bonded by the acetate oxygen, and the fifth and the sixth donor sites come from the phenolate oxygen of another Schiff base ligand.

The title complex was isolated as red solid material from the reaction of Co(SCN)2 with 4(Salicylaldimine) antipyrine in ethanol. The molecular structure has been determined by elemental analysis, FT IR, UV-Vis and X-ray diffraction. The crystallographic data are: monoclinic

P21/n, a = 9.8335(3) A, b = 18.8593(6) A, c = 11.2921(4) A, = 90', =  = 90', V = 2041.46(12) ų and Z 2, R =0.045. The dicobalt (Il) complex is centrosymmetric dimer in which the Co(ll) ions are six coordinate being bonded to three coordinating donor sites from the corresponding tridentate Schiff base ligand and the fourth one is relatively bonded by phenolic oxygen, the fifth and sixth donor sites comes from isothiocyanate and methanol.

 carbon materials2 through their unique combination of excellent processability and high carbon yield. The enediyne functionality of the monomers undergo a thermal Bergman cycloaromatization reaction that yields reactive naphthalene diradicals which polymerize to form polynapthalene.(Figure 1) The tetrafunctionality of the monomers allows for both a higher processing window due to extensive branching and ultimately the formation of network polymers. The high carbon yield results in less shrinkage of the polymer upon pyrolysis to the glassy carbon state. This allows for the faithful templating of carbon structures from a polymeric precursor.

Hydrogen fuel cell electrodes require several properties for optimum performance. An ideal electrode would have as high a surface area as possible with an uniform dispersion of nano-scale catalyst particles attached to the surface. The electrode must be electrically conductive and have good mass transport for products and reactants. Carbon supported platinum is the best known catalyst for the oxidation of hydrogen at the anode and the reduction of oxygen at the cathode of a proton exchange membrane fuel cell (PEMFC) 3. The material also must have good compatibility with the material used for the proton exchange membrane in the membrane electrode assembly (MEA), usually a sulfonated fluoropolymer such as Nafion. We have undertaken a study to prepare a high surface area carbon material through a BODA templating method which can then be functionalized with both well dispersed platinum nanoparticles …

The preparation and characterization of a cobalt substituted ETS-10 titanosilicate are described. X-ray diffraction shows that cobalt incorporation causes an increase in unit cell dimensions. UV–VIS, EPR, Raman and Co K-edge XANES spectra all show that Co2+ occupies tetrahedral sites, substituting for silicon. The 29Si NMR spectra do not permit identification of which silicon sites in ETS-10 are substituted, but the Co K-edge EXAFS shows clearly that Co2+ substitutes at Si(3Si,1Ti) sites.

A review is given of recent work in the authors' laboratory on the characterization of different forms of nanostructured titania. It is shown that nanocrystalline anatase powders and nanocrystalline anatase thin films differ significantly in their optical properties, due primarily to differences in sintering behaviour on drying. It is argued that the electronic properties of these systems are determined by surface phenomena rather than quantum size effects. The novel titanosilicate zeolite ETS-10 which contains one dimensional “quantum wires” of titania provides an alternative system for studying quantum size effects which has considerable potential for photocatalysis.