Study of removal of Direct Yellow 12 by cadmium oxide nanowires loaded on activated carbon

In this research, cadmium oxide nanowires loaded on activated carbon (CdO-NW-AC) has been synthesized by a simple procedure and characterized by different techniques such as XRD, SEM and UV–vis spectrometry. This new adsorbent has been efficiently utilized for the removal of the Direct Yellow 12 (DY-12) from wastewater. To obtain maximum DY-12 removal efficiency, the influences of variables such as pH, DY-12 concentration, amount of CdO-NW-AC, contact time, and temperature have been examined and optimized in a batch method. Following the variable optimization, the experimental equilibrium data (at different concentration of DY-12) was fitted to conventional isotherm models such as Langmuir, Freundlich and Tempkin. The applicability of each method is based on the R² and error analysis for each model. It was found that the experimental equilibrium data well fitted to the Langmuir isotherm model. The dependency of removal process to time and the experimental data follow second order kinetic model with involvement of intraparticle diffusion model. The negative value of Gibbs's free energy and positive value of adsorption enthalpy show the spontaneous and endothermic nature of adsorption process.     

Simultaneous preconcentration and determination of copper, nickel, cobalt and lead ions content by flame atomic absorption spectrometry

A sensitive and simple method for the simultaneous preconcentration of nutritionally important minerals in real samples has been reported. The method is based on the formation of metal complexes by 4,6-dihydroxy-2-mercaptopyrimidine (DHMP) loaded on activated carbon. The metals content on the complexes are then eluted using 5 mL 2M HNO(3) in acetone, which are detected by AAS at resonance line. In this procedure, minerals such as Cu, Ni, Pb and Co could be analyzed in one run by caring out the simultaneous separation and quantification of them. At optimum condition the response are linear over concentration range of 0.04-1.1 microg mL(-1) for Ni(2+) and 0.04-1.0 microg mL(-1) for Cu(2+), Pb(2+) and Co(2+). The detection limits of each element are expressed as the amount of analytes in ng mL(-1) giving a signal to noise ratio of 3 are equal to 3.5, 3.4, 2.9 and 8.4 for Ni(2+), Co(2+), Cu(2+) and Pb(2+). The sorption capacity was determined by saturating 0.5 g solid phase. The loading capacity are 0.54, 0.53, 0.63 and 0.45 mg g(-1) for Ni(2+), Co(2+), Cu(2+) and Pb(2+). The ability of method for repeatable recovery of trace ion are 99.0, 98.9, 99.2 and 98.8 with R.S.D. of 1.4, 1.3, 1.2 and 1.4 for Ni(2+), Co(2+), Cu(2+) and Pb(2+). The low detection limits of these elements in this technique make it a superior alternative to UV-vis and in several applications, also an alternative to ICP-MS techniques. The method has been successfully applied for these metals content evaluation in some real samples including natural water, leaves of spinach and cow liver.     

Cloud point extraction and flame atomic absorption spectrometry combination for copper(II) ion in environmental and biological samples

A cloud point extraction procedure was presented for the preconcentration of copper(II) ion in various samples. After complexation by 4-(phenyl diazenyl) benzene-1,3-diamine (PDBDM) (chrysoidine), copper(II) ions were quantitatively recovered in Triton X-114 after centrifugation. 0.5 ml of methanol acidified with 1.0 mol L⁻¹ HNO₃ was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The influence of analytical parameters including ligand, Triton X-114 and HNO₃ concentrations, bath temperature, heating time, centrifuge rate and time were optimized. The effect of the matrix ions on the recovery of copper(II) ions was investigated. The detection limit (3S.D._b/m, n = 10) of 0.6 ng mL⁻¹ along with preconcentration factor of 30 and enrichment factor of 41.1 with R.S.D. of 1.0% for Cu was achieved. The proposed procedure was applied to the analysis of various environmental and biological samples.     

Equilibrium,kinetic and isotherm of some metal ion biosorption

Trichoderma reesei was used as a biosorbent for the removal of Co²⁺, Cu²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ ions. The influence of factors such as pH, mass of biomass, contact time and temperature on biosorption efficiency was optimized. To calculate the isotherm parameters for the biosorption of Co²⁺, Cu²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ ions at optimized conditions, the experimental equilibrium data were fitted to Langmuir and Freundlich models. The calculated thermodynamic parameters, ΔG°, ΔH° and ΔS° showed that the biosorption of Co²⁺, Cu²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ ions onto T. reesei biomass was feasible, spontaneous and endothermic at the optimized conditions. The results of kinetic analysis showed that the biosorption of the selected metal ions onto T. reesei biomass obeys pseudo second order kinetics.     

Designing and synthesis of bis(2,4-dihydroxybenzylidene)-1,6-diaminohexane and its efficient application as neutral carrier for preparation of new copper selective electrode

A new copper carbon paste electrode (CPE) based on incorporation bis(2, 4-dihydroxybenzyliden)-1,6-diaminohexane (DHBDAH) in graphite powder matrix has been described. The influence of variables including an amount of graphite, sodium tetraphenylborate (NaTPB), DHBDAH and nujol on the Cu²⁺ carbon paste electrode response was studied and optimized. The optimum carbon paste composition was set as follows, graphite powder: NaTPB: Nujol: DHBDAH with amount of 150:2.3:30:4 mg, respectively. At the optimum conditions, the potential response is linear over the concentration range of 5.0 × 10^? 8 to 1.0 × 10^? 1 mol L^? 1 with a Nernstian slope of 29.5 ± 1.1 mV per decade of Cu²⁺ ion concentration. The good performance of electrode such as low detection limit of (LOD) (4 × 10^? 8 mol L^? 1), wide applicable pH range (2.5–5.5), fast response time (?10 s) and adequate shelf life (69 days) indicate the utility of the proposed electrode for evaluation of Cu²⁺ ion content in various analysis. Due to moderate potentiometric selectivity coefficients of proposed electrode obtained by fixed interference method (FIM) and separate solution method (SSM), the proposed electrode successfully can be applied for the determination of Cu²⁺ ions content in some real samples.     

Preconcentration and separation of trace amount of heavy metal ions on bis(2-hydroxy acetophenone)ethylendiimine loaded on activated carbon

A sensitive and simple method for simultaneous preconcentration of trace heavy metal ions in some food samples has been reported. The method is based on the adsorption of Cr(3+), Fe(3+), Cu(2+), Ni(2+), Co(2+) and Zn(2+) on bis(2-hydroxy acetophenone)ethylendiimine (BHAPED) loaded on activated carbon (AC). The adsorbed metals on activated carbon were eluted using 2 mol L(-1) nitric acid in acetone. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the recoveries of analyte ions were also investigated. The recoveries of analytes were generally higher than 94%. The method has been successfully applied for analysis of the metal contents in real samples including natural water samples.     

The determination of some heavy metals in food samples by flame atomic absorption spectrometry after their separation-preconcentration on bis salicyl aldehyde, 1,3 propan diimine (BSPDI) loaded on activated carbon

A sensitive and simple method for the simultaneous preconcentration of Cr3+, Fe3+, Cu2+, Ni2+, Co2+ and Zn2+ in real samples has been reported. The method is based on the adsorption of analytes on bis salicyl aldehyde, 1,3 propan diimine (BSPDI) loaded on activated carbon. The adsorbed metals on modified activated carbon were eluted using 8 mL of 2 mol L(-1) nitric acid in acetone or 10 mL of 4 mol L(-1) HNO3. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally quantitative. The method has been successfully applied for these metals content evaluation in some food samples.     

Dynamic analysis of multi-layered filament-wound composite pipes subjected to cyclic internal pressure and cyclic temperature

Based on the three-dimensional anisotropic elasticity, the stress analysis of multi-layered filament-wound composite pipes subjected to cyclic internal pressure and temperature loading is conducted in this article. The time-dependent stress, strain and deformation distributions are numerically obtained by the use of the finite difference technique. The pressure and temperature are considered to be symmetrical about the axis of the cylinder and independent of the axial coordinate. Each layer of the pipes is made of a homogeneous, anisotropic and linearly elastic material and it is assumed that the material properties do not change with increasing the temperature. The shear extension coupling is also considered because of lay-up angles. Numerical results obtained from the present model are compared with other published results and good agreement has been achieved.     

Chemical cleaning of reverse osmosis and nanofiltration membranes fouled by licorice aqueous solutions

The aim of this work was finding optimum cleaning agents and conditions for cleaning reverse osmosis (RO) and nanofiltration (NF) membranes fouled by licorice aqueous solutions. The effect of various chemicals on flux recovery (FR) and resistance removal (RR) of the fouled membranes was investigated. For both membranes the results indicate that a combination of ethylene diamine tetra acetic acid (EDTA), sodium dodecyl sulphate (SDS) and sodium hydroxide may be used as cleaning agents to achieve an optimum cleaning efficiency. Zeta potential and contact angle measurements indicate the changes in charge and hydrophilicity of the surface of RO and NF membranes at various pH solutions, respectively. The effect of surface characteristics is evident in efforts to select the optimal operating conditions. The effect of cleaning condition such as concentration, temperature, pH and cleaning time was studied. The optimum temperature, cleaning time, pH and concentration were found as 35 ± 1 °C, 20 min, 12 and 0.1 wt.%, respectively. SEM pictures showed the surface morphology of RO and NF membrane.