Impact of pH on CdII partitioning between alginate gel and aqueous media

2009 ◽  
Vol 6 (4) ◽  
pp. 305 ◽  
Author(s):  
Erwin J. J. Kalis ◽  
Thomas A. Davis ◽  
Raewyn M. Town ◽  
Herman P. van Leeuwen
Keyword(s):  
Functional Groups ◽  
Metal Ion ◽  
Ion Concentration ◽  
Local Concentration ◽  
Relevant Parameter ◽  
Donnan Potential ◽  
Alginate Gel ◽  
Bulk Medium ◽  
Ph Dependent

Environmental context. Biogels, such as those in cell walls or biofilm matrices, generally comprise negative structural charge which leads to accumulation of positively charged species, e.g. metal ions. The magnitude of the effective charge, and hence the local chemical speciation within the gel phase, is pH dependent. In situ speciation measurements in biogels, such as the model alginate studied in this work, offer a better estimate of bioavailable concentrations than does analysis of the surrounding aqueous medium. Abstract. Many microorganisms exist in a biogel-mediated micro-environment such as a cell wall or a biofilm, in which local concentrations of ionic nutrients and pollutants differ from those in the surrounding bulk medium. The local concentration is the relevant parameter for considerations of bioavailability. These modified concentrations arise as a consequence of the negative charges within biogels which may induce a Donnan potential inside the biogel phase. For metals, the net effect on the speciation within the biogel, relative to the bulk medium, is an enhancement of the concentration of free cations. Since the structural charge in the biogel arises from protolytic functional groups, the Donnan potential is pH dependent. Here we apply in situ voltammetry to measure the free metal ion concentration inside alginate gel as a function of pH. In the pH range 3 to 7, the speciation of CdII within this model biogel can be explained by specific binding to carboxylic functional groups and electrostatic binding resulting from the Donnan potential.

scholarly journals Adsorption of Pb(II) and Cd(II) by SquidOmmastrephes bartramiMelanin

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
Shiguo Chen ◽  
Changhu Xue ◽  
Jingfeng Wang ◽  
Hui Feng ◽  
Yuming Wang ◽  
...  
Keyword(s):  
Functional Groups ◽  
Metal Binding ◽  
Metal Ion ◽  
Ion Concentration ◽  
Obvious Effect ◽  
Removal Of Heavy Metals ◽  
New Material ◽  
Amine Groups ◽  
Ir Analysis ◽  
Ph Range

The adsorption of Cd(II) and Pb(II) by squid melanin was investigated. At a metal ion concentration of 2 mM/L, the biosorption efficiency of melanin reached 95% for Cd(II) and Pb(II). The maximum content of bound Cd(II) and Pb(II) was 0.93 mM/g and 0.65 mM/g, respectively. Temperature had no obvious effect on the adsorption of the metals, and in a pH range of 4.0–7.0, the adsorption yield was high and stable. Macrosalts such as NaCl,MgCl2, andCaCl2had no obvious effect on the binding of Pb(II) but greatly diminished the adsorption of Cd(II), which indicated that different functional groups in squid melanin are responsible for their adsorption. IR analysis of metal ion-enriched squid melanin demonstrated that the possible functional groups responsible for metal binding were phenolic hydroxyl (OH), carboxyl (COOH), and amine groups (NH). This study reports a new material for the removal of heavy metals from low-strength wastewater.

Fabrication of a Conductometric Sensor for Crevice Corrosion Studies

2002 ◽  
Vol 729 ◽  
Author(s):  
Xiaoyan Wang ◽  
Robert G. Kelly ◽  
Jason S. Lee ◽  
Michael L. Reed
Keyword(s):  
Thin Film ◽  
Real Time ◽  
Crevice Corrosion ◽  
Metal Ion ◽  
Microelectromechanical Systems ◽  
Spatial Information ◽  
Ion Concentration ◽  
Potentiometric Sensors ◽  
Conductometric Sensor

AbstractMicrofabricated crevice corrosion samples have been employed in experiments that provided important information necessary for developing an accurate, comprehensive, and reliable crevice corrosion model. Acquiring real-time spatial information of crevice corrosion is also essential in analyzing corrosion processes. Integration of arrays of solid-state microsensors, such as conductometric sensors, pH and other ion concentration potentiometric sensors, into the crevice corrosion samples will allow for in-situ real-time data acquisition. In the present work, crevice corrosion samples with conductometric sensor arrays are made using the techniques developed for thin film semiconductor processing and microelectromechanical systems (MEMS) fabrication. The crevice corrosion testing sample is constructed by coupling a crevice former to a crevice substrate and has a uniform crevice gap. A conductometric sensor array built on a silicon wafer is incorporated into the crevice former. Each of these sensors is composed of a pair of thin film gold electrodes, which enables in-situ spatial conductivity analysis of crevice corrosion. Information about metal ion concentration and active chemistry inside the crevice can also be obtained.

scholarly journals Heavy metal complexation by surfaces and humic acids: a brief discourse on assessment by acidimetric titration.

1987 ◽  
Vol 35 (3) ◽  
pp. 231-240 ◽  
Author(s):  
Z.J. Wang ◽  
W. Stumm
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Heavy Metal Ions ◽  
Natural Waters ◽  
Ion Concentration ◽  
Natural Sample ◽  
Voltammetric Measurement ◽  
Ph Dependent ◽  
The Stability

In natural waters the form of occurrence of heavy metal ions needs to be known to understand the factors that control their concentrations, their reactivity and bioavailability. In natural samples, it is difficult to identify the species present and to distinguish between dissolved and particulate concentrations, because of the lack of sufficiently sensitive and specific analytical detectors. It is suggested that the voltammetric measurement of the labile metal ion concentration as a function of pH (from an acidimetric titration of a natural sample) may provide useful information on the pH-dependent distribution of soluble and particulate concentrations and on the stability of (surface and solute) complexes formed. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Chemistry and structural modulations in Bi2Sr2CuO6

1992 ◽  
Vol 7 (4) ◽  
pp. 844-852 ◽  
Author(s):  
Y. Shen ◽  
D.R. Richards ◽  
D.G. Hinks ◽  
A.W. Mitchell
Keyword(s):  
High Temperature ◽  
Oxygen Content ◽  
Metal Ion ◽  
Ion Concentration ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Long Time ◽  
Structural Modulation

A series of samples along the composition lines Bi2+xSr2−xCuOy, and Bi2Sr2−xCuOy have been used to study the structural modulation, chemistry, and superconducting properties of pseudo-tetragonal Bi2Sr2CuO6 (2201). The 2201 phase can be formed from crystallization of thin glassy platelets. The sample displayed a strong crystallographic (00l) orientation which made it possible to determine incommensurate modulations near (00l) reflections using a conventional x-ray θ-2θ scan. From the crystallization of the 2201 phase, it was found that structural modulation was intrinsic to the phase, and ordering of the structure required a long time at high temperature. High temperature in situ x-ray diffraction of a 2201 Bi2Sr1.85CuOy platelet showed that the modulation existed at 875 °C in O2 (Tmelt ≍ 892 °C in O2). These suggest that the structural modulation cannot be caused solely by oxygen ordering and that metal-ion displacement must be involved. By removing 0.04 to 0.05 oxygen atom per formula unit from Bi2Sr2CuOy and Bi2Sr1.85CuOy, the c* components of the modulation changed from 0.31 to 0.26 and from 0.38 to 0.31, respectively, while the b* component of the modulation remained approximately 0.2. This demonstrates that oxygen, while not the sole cause, does play a role in the formation of the structural modulation. However, the invariance of bmod with respect to the change in oxygen content does not support the model that explained the modulation by inserting extra oxygen in the BiO plane. By varying metal-ion concentrations of Bi and Sr we found that both the lattice parameters and the modulation vectors depended more on the Bi/Sr ratio than on the Sr concentration alone. As the Bi/Sr ratio increased from 1.0 to 1.35, the modulation lines moved toward the (00l) reflections. The corresponding superstructural periodicities were calculated to vary from ∼1/5b* + 0.32 c* to ∼1/5 b* + 0.63 c*. Effects of oxygen content and metal-ion concentration on the 2201 phase formation and the superconducting properties will also be discussed.

Correlation of Gelation Times for Polymer Solutions Used as Sweep Improvement Agents

1981 ◽  
Vol 21 (02) ◽  
pp. 229-235 ◽  
Author(s):  
Ronald E. Terry ◽  
Chyi-gang Huang ◽  
Don W. Green ◽  
Michael J. Michnick ◽  
G. Paul Willhite
Keyword(s):  
Oil Recovery ◽  
Metal Ion ◽  
Water Movement ◽  
Polymer Concentration ◽  
Gelation Time ◽  
Reducing Agent ◽  
Ion Concentration ◽  
Fluid Movement ◽  
Polymer Hydrolysis

Abstract Gelled polymers are being used increasingly to redirect or modify reservoir fluid movement in the vicinity of injection or production wells for the purpose of improving water/oil ratios. To date, little has been reported about the chemistry of the in-situ gelling process that involves a multivalent metal ion, a reducing agent, and a polymer. This paper reports results of a study of the relationship between process parameters and gelation time, which is defined as the time required for the solution to reach a specified viscosity. The gelation time is determined by continuous monitoring of the viscosity following addition of the chemical reactants. The varied parameters in the investigation include polymer type and concentration, chromate concentration, and reducing-agent type and concentration. Five different polyacrylamide polymers were used including polyacrylamides that were hydrolyzed to different degrees, an anionic copolymer, and a cationic copolymer. Sodium bisulfite and thiourea were used as reducing agents. It was determined that for a given polymer-reducing agent system, the reciprocal of gelation time is a linear function of the reciprocal of the polymer concentration for a fixed metal ion concentration. The slope of the straight line is a function of the degree of polymer hydrolysis, the existence of the anion or cation functional groups, and type of reducing agent used. Introduction Waterflooding generally has proved to be a highly successful oil recovery process. In those reservoirs where waterflooding has not been successful, the primary causes have been low sweep efficiencies and the bypassing of oil by water due to viscous fingering. Low sweep efficiencies can be caused by water channeling through fractures or zones of high permeability.The production of a large amount of water relative to the amount of oil produced is often a result of poor sweep efficiency in a waterflood project. Large water/oil ratios (WOR) and the subsequent handling and treating of the produced water lead to high operating costs and often make it uneconomical to continue a waterflooding program.Even where waterflooding has been successful, large volumes of water usually have been required. The economics have been justified by the fact that water is inexpensive and can be recirculated. Since water is relatively inexpensive to inject, there usually has been little concern about controlling the water movement in the reservoir while WOR remained below some predetermined (by economics) value.However, with the implementation of tertiary recovery methods, some of which involve the addition of expensive chemicals to the floodwater, it becomes very important that good fluid control be established. This is necessary so that the maximum volume of the reservoir is contacted by a minimum amount of fluid.There have been many attempts to control fluid movement in reservoirs to improve sweep efficiencies. Methods that have been among the most successful have used polymers, usually polyacrylamides, in some form. Polyacrylamides are thought to be especially effective since they have the ability to reduce formation permeabilities to water while retaining the permeabilities to oil. Early treatment involved simply the injection of polymers. Recent developments have shown that polyacrylamides can be crosslinked in situ to form a three-dimensional gel. SPEJ P. 229^

Reductive Cleavage of Secondary Sulfonamides: Converting Terminal Functional Groups into Versatile Synthetic Handles

2019 ◽  
Author(s):  
Patrick Fier ◽  
Suhong Kim ◽  
Kevin M. Maloney
Keyword(s):  
Functional Groups ◽  
Late Stage ◽  
Reductive Cleavage ◽  
Bioactive Molecules ◽  
General Method

Sulfonamides are pervasive in drugs and agrochemicals, yet are typically considered as terminal functional groups rather than synthetic handles. To enable the general late-stage functionalization of secondary sulfonamides, we have developed a mild and general method to reductively cleave the N-S bonds of sulfonamides to generate sulfinates and amines, components which can further react <i>in-situ</i> to access a variety of other medicinally relevant functional groups. The utility of this platform is highlighted by the selective manipulation of several complex bioactive molecules.

Use of agro-waste (Musa paradisiaca peels) as a sustainable biosorbent for toxic metal ions removal from contaminated water

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Contact Time ◽  
Metal Ion ◽  
Equilibrium Concentration ◽  
Ion Concentration ◽  
Contaminated Water ◽  
Musa Paradisiaca ◽  
Percentage Removal ◽  
Adsorbent Dose

A study of removal of heavy metal ions from heavy metal contaminated water using agro-waste was carried out with Musa paradisiaca peels as test adsorbent. The study was carried by adding known quantities of lead (II) ions and cadmium (II) ions each and respectively into specific volume of water and adding specific dose of the test adsorbent into the heavy metal ion solution, and the mixture was agitated for a specific period of time and then the concentration of the metal ion remaining in the solution was determined with Perkin Elmer Atomic absorption spectrophotometer model 2380. The effect of contact time, initial adsorbate concentration, adsorbent dose, pH and temperature were considered. From the effect of contact time results equilibrium concentration was established at 60minutes. The percentage removal of these metal ions studied, were all above 90%. Adsorption and percentage removal of Pb2+ and Cd2+ from their aqueous solutions were affected by change in initial metal ion concentration, adsorbent dose pH and temperature. Adsorption isotherm studies confirmed the adsorption of the metal ions on the test adsorbent with good mathematical fits into Langmuir and Freundlich adsorption isotherms. Regression correlation (R2) values of the isotherm plots are all positive (&gt;0.9), which suggests too, that the adsorption fitted into the isotherms considered.

The use of in-situ Raman spectroscopy in investigating carbon materials as the anodes of alkali metal-ion batteries

Carbon ◽  
2021 ◽  
Vol 177 ◽  
pp. 428
Author(s):  
Xiaoqin Cheng ◽  
Huijun Li ◽  
Zhenxin Zhao ◽  
Yong-zhen Wang ◽  
Xiaomin Wang
Keyword(s):  
Raman Spectroscopy ◽  
Alkali Metal ◽  
Metal Ion ◽  
Carbon Materials ◽  
In Situ Raman Spectroscopy ◽  
Alkali Metal Ion ◽  
In Situ Raman

scholarly journals Chemical Composition and Corrosion Behavior of a-C:H/DLC Film-Coated Titanium Substrate in Simulated PEMFC Environment

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 820
Author(s):  
Beibei Han ◽  
Mengyuan Yan ◽  
Dongying Ju ◽  
Maorong Chai ◽  
Susumu Sato
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Metal Ion ◽  
Ion Beam ◽  
Titanium Substrate ◽  
Corrosion Current ◽  
Ion Concentration ◽  
Bipolar Plates ◽  
High Adhesion ◽  
Corrosion Behaviors

The amorphous hydrogenated (a-C:H) film-coated titanium, using different CH4/H2 and deposition times, was prepared by the ion beam deposition (IBD) method, which has the advantage of high adhesion because of the graded interface mixes at the atomic level. The chemical characterizations and corrosion behaviors of a-C:H film were investigated and evaluated by SEM, AFM, Raman spectroscopy, EPMA, TEM and XPS. An a-C:H film-coated titanium was corroded at 0.8 V, 90 °C in a 0.5 mol/L H2SO4 solution for 168 h. The metal ion concentration in the H2SO4 corrosion solution and the potentiodynamic polarization behavior were evaluated. Results indicate that a higher CH4/H2 of 1:0 and a deposition time of 12 h can result in a minimum ID/IG ratio of 0.827, Ra of 5.76 nm, metal ion concentration of 0.34 ppm in the corrosion solution and a corrosion current of 0.23 µA/cm2. The current density in this work meets the DOE’s 2020 target of 1 µA/cm2. Electrical conductivity is inversely proportional to the corrosion resistance. The significant improvement in the corrosion resistance of the a-C:H film was mainly attributed to the increased sp3 element and nanocrystalline TiC phase in the penetration layer. As a result, the a-C:H film-coated titanium at CH4/H2 = 1:0 with improved anti-corrosion behavior creates a great potential for PEMFC bipolar plates.

Sign in / Sign up

Export Citation Format

Share Document