Extraction of lead using EDTA: factors affecting extraction, effects of amorphous iron and recycling of used EDTA

The effects of major cations present in soils, soil:extractant ratio, and EDTA:lead stoichiometric ratio on the extraction efficiency of lead using EDTA were studied for three different Superfund soils, one rifle range soil, and one artificially lead-contaminated soil. Extraction of lead from the lead-contaminated soils was not affected by a soil:extractant ratio as low as 1:3 but instead was dependent on the quantity of EDTA present. The extraction efficiency for each soil was different. The differences in extraction efficiencies may be due to the major cations present in soils. Among the cations present, ferric ions probably competed most strongly with lead for EDTA ligand sites for pH values less than 6. In addition, Cu and Zn may have a potential to compete with Pb for EDTA ligand sites. At high pH values, Ca may have an effect on lead extraction. For some of the soils tested, the extraction efficiency of lead may be affected by being occluded in the Fe and Mn oxides present in the soil. While major cations present in the soil may be one of the factors affecting lead extraction efficiency, the type of lead species present may also play a role;Bench-scale experiments were conducted with three different artificially prepared lead-contaminated soils (lead sulfate, lead carbonate and lead phosphate) with and without addition of amorphous iron to investigate the amorphous iron effects on the lead extraction. The experimental results indicated that amorphous iron effects on lead extraction was dependent on the equilibrium pH and lead species present;A method to recycle used Pb-EDTA was proposed. The proposed method consists of substituting the Pb ions with Fe ions, uncomplexed Pb ions precipitation with phosphate or sulfate ions and with/without Fe precipitation using pH control. According to the experimental results, the used EDTA wastewater can be recycled for further treatment. In addition, experimental results showed that recycled used EDTA with phosphate precipitation was slightly more superior than recycled used EDTA with sulfate precipitation. Both recycled EDTA solutions (phosphate and sulfate precipitation) showed similar or slightly lower extractive abilities when compared to fresh EDTA solution

Adoption of Short Message Service: Gender Difference

While the adoption of mobile devices has recently received research attention, there has been little research focusing on a specific application or service running in mobile devices. In this study, we examine the adoption of short message service (SMS) with the technology acceptance model. The model has been assessed with the data collected from 225 SMS users. Results from the partial least squares analysis show that perceived ease of use of SMS positively affects perceived usefulness of SMS and intention to adopt SMS, and perceived usefulness of SMS also positively affects intention to adopt SMS. Comparing the two factors, perceived usefulness is more influential than perceived ease of use in the SMS adoption, which implies that extrinsic, i.e., task -oriented, characteristics of SMS may be more important than its intrinsic characteristics in the adoption decision. This study includes how the gender moderates the effects of the two factors on the SMS adoption, showing that the effect of perceived ease of use on the SMS adoption is stronger for female. Implications and future research are discusse

Influence of soil minerals on chromium(VI) reduction by sulfide under anoxic conditions

The effects of soil minerals on chromate (Cr(VI)O(4)(2-), noted as Cr(VI)) reduction by sulfide were investigated in the pH range of 7.67 to 9.07 under the anoxic condition. The examined minerals included montmorillonite (Swy-2), illite (IMt-2), kaolinite (KGa-2), aluminum oxide (γ-Al(2)O(3)), titanium oxide (TiO(2), P-25, primarily anatase), and silica (SiO(2)). Based on their effects on Cr(VI) reduction, these minerals were categorized into three groups: (i) minerals catalyzing Cr(VI) reduction – illite; (ii) minerals with no effect – Al(2)O(3); and (iii) minerals inhibiting Cr(VI) reduction- kaolinite, montmorillonite, SiO(2 )and TiO(2 ). The catalysis of illite was attributed primarily to the low concentration of iron solubilized from the mineral, which could accelerate Cr(VI) reduction by shuttling electrons from sulfide to Cr(VI). Additionally, elemental sulfur produced as the primary product of sulfide oxidation could further catalyze Cr(VI) reduction in the heterogeneous system. Previous studies have shown that adsorption of sulfide onto elemental sulfur nanoparticles could greatly increase sulfide reactivity towards Cr(VI) reduction. Consequently, the observed rate constant, k(obs), increased with increasing amounts of both iron solubilized from illite and elemental sulfur produced during the reaction. The catalysis of iron, however, was found to be blocked by phenanthroline, a strong complexing agent for ferrous iron. In this case, the overall reaction rate at the initial stage of reaction was pseudo first order with respect to Cr(VI), i.e., the reaction kinetics was similar to that in the homogeneous system, because elemental sulfur exerted no effect at the initial stage prior to accumulation of elemental sulfur nanoparticles. In the suspension of kaolinite, which belonged to group (iii), an inhibitive effect to Cr(VI) reduction was observed and subsequently examined in more details. The inhibition was due to the sorption of elemental sulfur onto kaolinite, which reduced or completely eliminated the catalytic effect of elemental sulfur, depending on kaolinite concentration. This was consistent with the observation that the catalysis of externally added elemental sulfur (50 μM) on Cr(VI) reduction would disappear with a kaolinite concentration of more than 5.0 g/L. In kaolinite suspension, the overall reaction rate law was: -d[Cr(VI)]/dt = k(obs)[H(+)](2)[Cr(VI)][HS(-)](0.70

Extraction of lead using EDTA: factors affecting extraction, effects of amorphous iron and recycling of used EDTA

The effects of major cations present in soils, soil:extractant ratio, and EDTA:lead stoichiometric ratio on the extraction efficiency of lead using EDTA were studied for three different Superfund soils, one rifle range soil, and one artificially lead-contaminated soil. Extraction of lead from the lead-contaminated soils was not affected by a soil:extractant ratio as low as 1:3 but instead was dependent on the quantity of EDTA present. The extraction efficiency for each soil was different. The differences in extraction efficiencies may be due to the major cations present in soils. Among the cations present, ferric ions probably competed most strongly with lead for EDTA ligand sites for pH values less than 6. In addition, Cu and Zn may have a potential to compete with Pb for EDTA ligand sites. At high pH values, Ca may have an effect on lead extraction. For some of the soils tested, the extraction efficiency of lead may be affected by being occluded in the Fe and Mn oxides present in the soil. While major cations present in the soil may be one of the factors affecting lead extraction efficiency, the type of lead species present may also play a role;Bench-scale experiments were conducted with three different artificially prepared lead-contaminated soils (lead sulfate, lead carbonate and lead phosphate) with and without addition of amorphous iron to investigate the amorphous iron effects on the lead extraction. The experimental results indicated that amorphous iron effects on lead extraction was dependent on the equilibrium pH and lead species present;A method to recycle used Pb-EDTA was proposed. The proposed method consists of substituting the Pb ions with Fe ions, uncomplexed Pb ions precipitation with phosphate or sulfate ions and with/without Fe precipitation using pH control. According to the experimental results, the used EDTA wastewater can be recycled for further treatment. In addition, experimental results showed that recycled used EDTA with phosphate precipitation was slightly more superior than recycled used EDTA with sulfate precipitation. Both recycled EDTA solutions (phosphate and sulfate precipitation) showed similar or slightly lower extractive abilities when compared to fresh EDTA solution.</p

A comparison study of ionic polymer-metal composites (IPMCs) fabricated with Nafion and other ion exchange membranes

Ionic polymer-metal composites (IPMCs) have been and still are one of the best candidates with great potential to be used as actuators and sensors particularly in bioengineering where the environmental conditions are in an aqueous medium. Each component of an IPMC is important. However, the ion exchange membrane should be more emphasized because it is where ions migrate when electrical stimulation is applied and eventually it produces deformation of the IPMC. So far, the most commonly used ion exchange membrane is Nafion and many studies have been conducted with it for IPMC applications. There are a number of other commercially available ion exchange membranes now, but only a few studies have been done on those membranes to be used in IPMC applications. In this study, four commercially available membranes, (1) Nafion N115 (DuPont), (2) CMI7000S (Membranes International Inc.), (3) F-14100 (fumatech), (4) GEFC-700 (Golden Energy Fuel Cell) were selected and fabricated in IPMCs and their potentials as actuators were examined by conducting various characterizations such as water uptake, ion exchange capacity, SEM, DSC, blocking force and bending displacement. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use onl

Robust Hydroxide Ion Conducting Poly(biphenyl alkylene)s for Alkaline Fuel Cell Membranes

High molecular weight, quaternary ammonium-tethered poly­(biphenyl alkylene)­s without alkaline labile C–O bonds were synthesized via acid-catalyzed polycondensation reactions for the first time. Ion-exchange capacity was conveniently controlled by adjusting the feed ratio of two ketone monomers in the polymerization. The resultant anion exchange membranes showed high hydroxide ion conductivity up to 120 mS/cm and excellent alkaline stability at 80 °C. This study provides a new synthetic strategy for the preparation of anion exchange membranes with robust fuel cell performance and excellent stability