Amounts Of Other Ions Research Articles

Cesium ion sorption on hybrid pectin-Prussian blue beads: Batch and column studies to remove radioactive cesium from contaminated wastewater

Hybrid sorbents composed of various ratios of Prussian blue (PB) and pectin were tested for their ability to remove cesium ions in batch and column mode. The maximum sorption capacity calculated from Langmuir isotherms was obtained for a sorbent with 50% PB additive (63.8 ± 1.7 mg g−1). The sorption kinetics studies performed at 12°C, 22°C, and 32°C and the equilibrium studies indicate physical sorption. The good sorption kinetics and the bead form of the proposed sorbents allowed column tests to be performed. Using 3 g of sorbent (50% PB), 870 mL of solution with an initial cesium content of 120 mg L−1 was purified to <2.4 mg L−1 (most of the eluate contained cesium at a level of 0.1 mg L−1). The effect of NaCl, KCl MgCl2, and CaCl2 at different concentrations on the sorption of cesium ions was also examined. The results indicated that the sorbent was also effective in a strongly saline environment, as well as in substitute ocean water and real Baltic seawater. The proposed sorbent enables safe, long-term storage of radioactive item in an air-dry, dust free state and in the smallest volume of material of high sorption capacity. This type of treatment is crucial for the disposal of radioactive waste whose activity can only be reduced by decay. Therefore, our hybrid sorbent is a promising material for the removal of (radioactive) cesium ions using either continuous or batch processes from waste aqueous solutions from a variety of sources, even those containing significant amounts of other ions.

An Efficient Polymer Inclusion Membrane-Based Device for Cd Monitoring in Seawater.

A novel and simple device that includes a polymer inclusion membrane (PIM) has been prepared and tested for the first time to detect low concentration levels of cadmium in seawater. The ionic liquid trihexyl (tetradecyl) phosphonium chloride (THTDPCl) has been shown to be an effective extractant when incorporated in a PIM that uses cellulose triacetate (CTA) as a polymer. However, it has been reported that the use of a plasticizer is mandatory to ensure an effective transport, which uses both ultrapure water and a nitric acid solution as a stripping phase. A special device incorporating a PIM made of 50% CTA, 40% nitrophenyl octyl ether (as a plasticizer), and 10% THTDPCl, effectively allows the quantitative transport and preconcentration of 10 µg L−1 Cd from seawater samples to a stripping phase consisting of 0.5 M HNO3 solution. This study shows that the efficiency of the PIM system is not affected by high salinity nor the presence of large amounts of other ions, and can thus facilitate Cd monitoring in seawater samples.

Adsorption efficiency, thermodynamics and kinetics of Schiff base-modified nanoparticles for removal of heavy metals

Nanosilica particles modified by Schiff base ligands 3-methoxy salicylaldimine propyl triethoxysilane (MNS1), 5-bromo salicylaldimine propyl triethoxysilane (MNS2) and 3-hydroxy salicylaldimine propyl triethoxysilane (MNS3) were prepared, and their potential for separation of copper, lead, zinc, cadmium, cobalt and nickel ions from aqueous solutions was examined. The effect of parameters influencing adsorption efficiency including aqueous-phase pH, amount of adsorbent, stirring time and initial concentration of the metal ions was assessed and discussed. Although MNS1 and MNS3 removed lead ions efficiently, all adsorbents showed strong selectivity toward copper ions. It was shown that, under some circumstances, MNS3 decreased the amount of other ions, particularly cobalt, in the aqueous phase. The adsorbents were also applied for removal of copper and lead ions from real samples. Possible quantitative desorption of the metal ions loaded onto the adsorbents suggests their multiple uses in adsorption–desorption process. Investigation of temperature dependency of the process led to determination of the ΔH°, ΔS° and ΔG° values. This investigation indicates that the adsorption of copper ions onto the all studied adsorbents and lead ions onto MNS1 and MNS3 is endothermic. The Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms were tested to describe the equilibrium data. Pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion equations were applied to study the kinetics of copper and lead adsorption onto the modified nanoparticles. This investigation indicates that the process for all adsorbents follows pseudo-second-order kinetics and suggests a chemisorption mechanism for the adsorption processes by the studied adsorbents.

Understanding the hydrochemical evolution of a coastal dune system in SW England using a multiple tracer technique

An improved knowledge of the hydrology of coastal dune systems is desirable for successful management of their diverse ecology under a changing climate. As a near-pristine coastal dune spit system, Braunton Burrows (SW England) is an ideal location for the study of the natural processes governing recharge to the dune groundwater system and the evolution of its water quality. Whereas previous investigations have tended to focus on inter-dune slacks, this study has also given attention to infiltration through the high dunes. Cores were taken through dunes and the resulting sand samples processed to provide information on grain size distribution and porewater chemistry. Groundwater samples were obtained from beneath dunes and slacks. A variety of geochemical techniques were applied including hydrochemistry, stable isotopes and residence time indicators. The unsaturated zone profiles indicate the existence of piston flow recharge with an infiltration rate of 0.75–1m/yr, although faster rates probably also occur locally. Groundwater beneath the high dunes gave ages in the range 13–16yr, compared to the dune slack groundwater ages of 5–7yr, and an age of 22yr for groundwater from the underlying mudstone aquifer. The chemistry of waters in both unsaturated and saturated zones is dominated by Ca and HCO3, supplemented by variable amounts of other ions derived from marine aerosols and limited reaction with sand grains and their coatings. The main chemical evolution of the porewaters occurs rapidly through the mobilisation of surface salt crusts and dissolution of shell carbonate. This situation changes little in the underlying groundwater, though an evolution towards reducing conditions increases the concentrations of redox-sensitive species such as Fe and Mn. The rapid chemical evolution of the infiltrating water means that its composition will respond quickly to changes in the supply of shell material and/or marine salts, which are possible consequences of climate change. However, the residence time measurements suggest the dune aquifer has a relatively long turnover time which will to some extent buffer such changes. The results of the present study should be transferable to natural dune systems in similar coastal situations.

Sensitive Detection, Selective Determination, and Removal of Nitrite from Water Using the Reactive Function Group of Polyurethane Foam

A simple and sensitive spectrophotometric method for the microdetermination of nitrite has been developed. This method is based on the reaction of nitrite with primary amine formed on polyurethane foam by (PUF) hydrolysis with hydrochloric acid, to form a diazonium salt, which couples with α‐naphthylamine, α‐naphthol, β‐naphthol, 8‐hydroxyquinoline, resorcinol, or catechol. Introduction of primary amine group on polyurethane foam is also tried via a nitration step followed by reduction of nitro groups with zinc dust in acid media. The purple azo dye formed on the surface of the foam material is used for quantitative and/or semiquantitative determination of submicrogram amounts of nitrite spectrophotometrically or visually, respectively. As low as 0.3 ng · /ml−1 of nitrite is easily detected and Beer's law is obeyed in the concentration range 0.5–100 µg · l−1 at λmax 530 nm with molar absorptivity of 3.5 × 106 l · mol−1 · cm−1 for using α‐naphthylamine as coupling agent. The method is optimized for acidity, time of coupling required, sorption isotherm, and the tolerance amount of other ions. The average sorption capacity of a different type of PUF 0.29 mmol · g−1, preconcentration factor value ≈100, and 100% recovery were obtained (RSD ≈ 2.11%). The method has been applied to various real samples.

Systematic Bench‐Scale Assessment of Perchlorate (ClO4 −) Rejection Mechanisms by Nanofiltration and Ultrafiltration Membranes#

Measurements of the rejection of perchlorate anion (ClO4 −) have been performed by using two thin‐film composite nanofiltration (NF) membranes and four ultrafiltration (UF) membranes. The latter four membranes are all from the same manufacturer and, ostensibly, from the same material family. These were chosen to systematically change the membranes steric properties, while keeping the same material chemistry, thus, the enthalpic interactions should stay constant. The perchlorate anion (at a concentration of 100 g/L of ClO4 − by “spiking” with KClO4) was presented to the membrane as a pure component, in binary mixtures with other salts, and at varying pH and ionic strength (conductivity). Also, a natural source water was “spiked” with perchlorate anion and used to document the effects of a complex mixture, including natural organic matter, on the observed rejection. All filtration measurements were performed at approximately the same permeate flow rate to minimize artifacts from mass transfer at the membrane interface. In general, the results indicate that, in a pure component system, target ions (in this case ClO4 −) can be significantly excluded from like‐charged membranes with pores large with respect to the size of the ion, but this rejection capability decreases in the presence of a sufficient amount of other ions that can screen the electrostatic force field. #Contribution of the US Government, not subject to copyright in the United States

Use of surfactant modified ultrafiltration for perchlorate (ClO 4−) removal

Determinations of perchlorate anion (ClO 4 −) transport and rejection were performed using a surfactant modified ultrafiltration (UF) membrane. Perchlorate anion (at a concentration of 100 μg/L of ClO 4 −, spiked with KClO 4) was introduced to the membrane as a pure component, in binary mixtures with other salts, cationic and anionic surfactants, and at various ionic strength conditions (conductivity). Also, a natural source water was spiked with perchlorate in the presence of cationic and anionic surfactants and used to determine the effects of a complex mixture (including natural organic matter (NOM)) on the observed rejection. All filtration measurements were performed at approximately the same permeate flow rate in order to minimize artifacts from mass transfer at the membrane interface. The objective of this study was to modify a negatively charged UF membrane in terms of the fundamental mechanisms, steric/size exclusion and electrostatic exclusion and to enhance perchlorate rejection, with synthetic water and a blend of Colorado River water and State Project water (CRW/SPW). Previous work suggested that perchlorate was dominantly rejected by electrostatic exclusion for charged nanofiltration (NF) and UF membranes (Rejection of perchlorate by reverse osmosis, nanofiltration and ultrafiltration (UF) membranes: mechanism and modeling. Ph.D. dissertation, University of Colorado, Boulder, USA, 2001). In that research, perchlorate rejection capability was quickly lost in the presence of a sufficient amount of other ions. However, this study showed that ClO 4 − was excluded from a (negatively) charged UF membrane with pores large with respect to the size of the ion. Although perchlorate rejection capability due to apparent electrostatic force was reduced in the presence of a cationic surfactant, a desired amount of the ClO 4 − was excluded by steric exclusion. The steric exclusion was due to decreasing membrane pore size caused by the adsorption of the cationic surfactant.

Determination of nitrite by simple diazotization method

A simple and rapid spectrophotometric method for the determination of nitrite is described. This is based upon simple diazotization reactions involving p-nitroaniline (PNA) and sulfanilamide (SA) with ethyl acetoacetate (EAA) as the coupling agent. The absorbance was measured at 507 and 356 nm, respectively. The method is optimized for acidity, amount of reagents required, amount of sodium hydroxide and the tolerance amount of other ions. The range of linearity for PNA–EAA couple was 0.05–6.0 μg ml −1 of nitrite with molar absorptivity of 1.59×10 4 l mol −1 cm −1; while that for SA–EAA couple was found to be 0.2–3.0 μg ml −1 and 1.22×10 4 l mol −1 cm −1, respectively. The method has been applied to various water and soil samples.

Transport of perchlorate (ClO 4−) through NF and UF membranes

Measurements of the rejection of perchlorate anion (ClO 4 −) were performed using nanofiltration (NF) and ultrafiltration (UF) membranes. Aqueous solutions of perchlorate (at a concentration of 100 μg/L of ClO 4 − by “spiking” with KClO 4) were fed to the membrane test apparatus. Solutions contained only perchlorate, or an additional salt (KCl, K 2SO 4, or CaCl 2) at overall ionic strengths of 30, 60, or 115 mS/cm, and pH adjusted to 4, 6, 8, or 10. The data were modeled by application of a non-equilibrium thermodynamic model. The model has five parameters: the molecular transport coefficient (ω), osmotic pressure gradient (ΔΠ), molecular reflection coefficient (σ), the average bulk fluid interfacial concentration between the feed and permeate side ( C avg), and the solvent flux ( J v). These parameters were determined by independent measurements (and calculation with minimum assumptions.) For example, the molecular transport coefficient (ω) was obtained by diffusion cell measurements under varying pH and conductivity conditions — generally it decreased with increasing pH and increased with conductivity for the membranes in our study. Measured and predicted perchlorate transport was in good agreement. Overall, the results indicate that, in a pure component system, target ions (in this case ClO 4 −) can be excluded from (negatively) charged membranes with pores large with respect to the size of the ion, but this rejection capability is quickly lost in the presence of a sufficient amount of other ions that can screen the apparent electrostatic force field. As intuitively expected, the perchlorate flux is governed by convection in large pore membranes.

Spectrophotometric determination of nitrite and nitrate using phosphomolybdenum blue complex

A method for spectrophotometric determination of nitrite and nitrate is described. This method is based on the reduction of phosphomolybdic acid to phosphomolybdenum blue complex by sodium sulfide. The obtained phosphomolybdenum blue complex is oxidized by the addition of nitrite and this causes a reduction in intensity of the blue color. The absolute decrease in the absorbance of the blue color or the rate of its decrease is found to be directly proportional to the amount of nitrite added. The absorbance of the phosphomolybdenum blue complex is monitored spectrophotometrically at 814 nm and related to the concentration of nitrite present. The effect of different factors such as acidity, stability of the complex, time, temperature, phosphate concentration, molybdenum concentration, sodium sulfide concentration and the tolerance amount of other ions have been reported. Maximum absorbance is at 814 nm. The range of linearity using the conventional method is 0.5–2.0 ppm with molar absorptivity of 1.1×10 4 l mol −1 cm −1. and a relative standard deviation of 2.6% for five measurements. The range of linearity using the reaction rate method is 0.2–3.6 ppm with a relative standard deviation of 2.4% for five measurements. The method is applied for determination of nitrite and nitrate in water, meat products and vegetables.

Sensitive spectrophotometric determination of vanadium with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol after extraction with N-benzoyl-N-phenylhydroxylamine

A selective and precise spectrophotometric determination of vanadium(V) is performed after preceding extraction with N-benzoyl-N-phenylhydroxylamine (BPHA). The color is developed in a water-ethanol solution with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol (5-Cl-DMPAP). The molar absorptivity at 588 nm is (6.57 ± 0.05) × 104 L mol–1 cm–1 at pH 2.1. The method permits the determination of vanadium (V) at trace levels in the presence of large amounts of other ions. It is applied to the determination of vanadium in aluminium (analytical reagent grade) and in human hair. High accuracy and precision is obtained.

Spectrophotometric Determination of Niobium with Hydrogen Peroxide and 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol in Steel and Apatite after Its Extractive Separation as α-Benzoin Oxamate

A sensitive method for the spectrophotometric determination of niobium(V) based on the formation of its complex with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the presence of hydrogen peroxide has been developed. The molar absorptivity at 591 nm is 7.43×104 1 mol-1 cm-1 at pH 4.0+-1.0. This method becomes selective for niobium(V) after a preliminary extraction of its complex with α-benzoin oxime from 5–9 M hydrochloric acid, thus permitting the determination of traces of niobium in the presence of a large amount of other ions. It has been applied to the determination of niobium in materials of certified Nb content: steel and apatite samples.

Selective spectrophotometric determination of trace amounts of chromium(VI) using a flow injection system with a microcolumn of zirconium(IV) oxide modified silica gel

Zirconium(IV) oxide coated on a silica gel surface was found to be very effective for extracting CrVI from aqueous solutions at a pH of about 3. A microcolumn packed with this material was inserted into a flow injection system for the separation and preconcentration of CrVI. By this process, a concentration level of 2 ppb was detected with a relative standard deviation of 2.4%. Because of the high selectivity of the immobilized substrate, it was possible to determine CrVI in the presence of larger amounts of other ions. The analysis was also carried out on natural water spiked with CrVI, and compared with a standard method.

Extraction-spectrophotometric determination of niobium with N-phenylbenzohydroxamic acid and 4-(2-pyridylazo)resorcinol in non-aqueous media

A method for the spectrophotometric determination of niobium(V) is proposed, in which niobium(V) is extracted with N-phenylbenzohydroxamic acid into chloroform from 5 M hydrochloric acid. The colour is then developed in an aliquot of the chloroform extract by addition of 4-(2-pyridylazo)resorcinol solution in N,N-dimethylformamide without back-extraction. The molar absorptivity at 547 nm is 3.35 × 104 l mol–1 cm–1 with a relative standard deviation of 1.0%. The proposed method permits the determination of niobium(V) at trace levels in the presence of large amounts of other ions. The method has been applied to the determination of niobium in BCS standard steels and ores (IGS standard culombites) and high accuracy and precision have been obtained.

Solvent extraction and spectrophotometric determination of iron(II) with 2,2′-dipyridyl-2-quinolylhydrazone

2,2′-Dipyridyl-2-quinolylhydrazone (DPQH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) reacts with DPQH at pH 3.4–4.5 to form a water-insoluble 1:2 complex, which can be extracted with many kinds of organic solvent. The extracted species with benzene has absorption maxima at 473, 504, and 644 nm and obeyed Beer's law over the range 0–14 μg of iron at 504 nm and 0–33 μg at 644 nm. The molar absorptivities at 504 and 644 nm are 3.14 × 10 4 and 1.30 × 10 4 M −1 cm −1, respectively. DPQH is one of the most sensitive reagents for iron(II) and trace amount of iron(II) can be determined in the presence of fairly large amounts of other ions. Possible equilibria involved in the extraction process were also studied.

Occurrence of chromian, hercynitic spinel (“pleonaste”) in Apollo-14 samples and its petrologic implications

Many isolated grains of a reddish pleonaste-type spinel occur in fines and metabreccia samples, particularly 14 319. Electron microprobe analyses (104) of spinels and their associated phases include 58 of pleonaste which show Mg/(Mg + Fe) 0.44–0.62 and Cr/(Cr + Al) 0.017–0.134 (atomic), plus minor amounts of other ions, and differ greatly from almost all previously recorded lunar spinels; almost no spinels of intermediate composition were found. Two types of compositional zoning exist: a diffuse primary one with cores lower in Ti, and a narrow secondary one from reaction with matrix yielding rims higher in Cr, Ti, and Mn. At contacts with breccia matrix there is a narrow corona of almost pure plagioclase (An 80-An 94), free of opaque minerals and pyroxene. Two types of solid inclusions found in the pleonaste are calcic plagioclase, and tiny spherical masses of nickel-rich sulfide. Similar pleonaste occurs in crystalline rock clasts, mainly with plagioclase; one clast (A) consists only of coarse olivine, plagioclase, and pleonaste, with granulated grain boundaries suggestive of deformation. From composition and texture, this clast is one possible candidate for the mafic cumulate counterpart of the “anorthositic” crust. Another clast (B), also made solely of olivine, plagioclase and pleonaste, is itself a breccia. These data suggest a two-stage brecciation process: 1) disruption (probably pre-Imbrian) of a deep-seated pleonaste-bearing source rock like A and reconsolidation to form a breccia without addition of pyroxene, ilmenite or other minerals; and 2) disruption of this breccia to yield breccia clast B which was then incorporated into the Fra Mauro formation.

Thermodynamic calculations on phase equilibria involving fused salts; part I, General theory and application to equilibria involving calcium carbonate at high pressure

A theory is developed for determining melting-point curves of salt mixtures and of salt mixtures containing small amounts of other ions. Depression of the curves is illustrated for NaCl + NaF and CaO + CaCl ₂ at atmospheric pressure and then applied at 1000 bars to the system Ca(OH) ₂ -CaCO ₃ . The presence of 1.35 weight percent of water is calculated to lower the eutectic temperature in this system by 10 degrees C.