Preferential Removal of Alkali Metal Using Dodecanoic Acid and Sodium Dodecyl Sulfate in Foam Separation System.

The selectivity of adsorption between alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) based on the ionic functional groups of the surfactants was studied using two types of surfactants, dodecanoic acid (DA) and sodium dodecyl sulfate (SDS), in the foam separation system. The results showed that Li+ was preferably removed by foam separation using DA. The removal rates of other alkali metal ions were relatively low, and there were no significant differences among other alkali metal ions (Na+, K+, Rb+, and Cs+). However, Cs+ exhibited the highest removal rate among the mixed alkali metals by foam separation using SDS. From these results, the selectivity of the alkali metal in foam separation was dependent on the type of surfactant.

Investigation of the relevance between biomass pyrolysis polygeneration and washing pretreatment under different severities: Water, dilute acid solution and aqueous phase bio-oil.

Washing pretreatments of rice straw were performed using three different solutions, namely water, dilute hydrochloric acid solution (HCl solution, pH = 2.9), and aqueous phase bio-oil (APBO, pH = 2.9). The raw and pretreated samples were pyrolyzed at 550 °C in a fixed bed reactor. Results showed that among the three pretreatments, washing with APBO had the highest removal efficiency of alkali metal and alkaline earth metals (AAEMs). Among the pyrolysis products, bio-oil from APBO washed sample had the highest mass, energy, and carbon yields, lowest water content of 36.9%, highest HHV of 17.2 MJ/kg, and highest relative content of anhydrosugars of 31.2%. Its biochar had the lowest ash content of 27.3% and highest specific surface area of 98.6 m2/g, and its non-condensable gases had the highest HHV of 11.9 MJ/m3. Therefore, APBO washing was effective in improving the quality of biomass and its subsequent pyrolysis products.

Metalless electrodes for capacitively coupled contactless conductivity detection on electrophoresis microchips.

This paper describes the use of ionic solutions as sensing electrodes for capacitively coupled contactless conductivity detection on electrophoresis microchips. Initially, two channels were engraved in a PMMA holder by using a CO2 laser system and sealed with a thin adhesive membrane. PDMS electrophoresis chips were fabricated by soft lithography and reversibly sealed against the polymer membrane. Different ionic solutions were investigated as metalless electrodes. The electrode channels were filled with KCl solutions prepared in conductivity values from approximately 10 to 40 S/m. The best analytical response was achieved using the KCl solution with 21.9 S/m conductivity (2 mol/L). Besides KCl, we also tested NaCl and LiCl solutions for actuating as detection electrodes. Taking into account the same electrolyte concentration (2 mol/L), the best response was recorded with KCl solution due to its higher ionic conductivity. The optimum operating frequency (400 kHz) and the best sensing electrode (2 mol/L KCl) were used to monitor electrophoretic separations of a mixture containing K(+) , Na(+) , and Li(+) . The use of liquid solutions as sensing electrodes for capacitively coupled contactless conductivity detection measurements has revealed great performance to monitor separations on chip-based devices, avoiding complicated fabrication schemes to include metal deposition and encapsulation of electrodes. The LOD values were estimated to be 28, 40, and 58 µmol/L for K(+) , Na(+) , and Li(+) , respectively, what is comparable to that of conventional metal electrodes. When compared to the use metal electrodes, the proposed approach offers advantages regarding the easiness of fabrication, simplicity, and lower cost per device.

Separation of ions using polyelectrolyte-modified nanoporous track-etched membranes.

Selective ion exclusion from charged nanopores in track-etched membranes allows separation of ions with different charges or mobilities. This study examines pressure-driven transport of dissolved ions through track-etched membranes modified by adsorption of poly(styrene sulfonate) (PSS)/protonated poly(allylamine) (PAH) films. For nominal 30 nm pores modified with a single layer of PSS, Br(-)/SO4(2-) selectivities are ∼3.4 with SO4(2-) rejections around 85% due to selective electrostatic exclusion of the divalent anion from the negatively charged pore. Corresponding membranes containing an adsorbed PSS/PAH bilayer are positively charged and exhibit average K(+)/Mg(2+) selectivities >10 at 8 mM ionic strength, and Mg(2+) rejections are >97.5% at ionic strengths <5 mM. The high rejection of Mg(2+) compared to SO4(2-) likely results from both a smaller pore size after deposition of the PAH layer and higher surface charge because of Mg(2+) adsorption. Simultaneous modeling of K(+) and Mg(2+) rejections using the nonlinearized Poisson-Boltzmann equation gives an average modified pore diameter of 8.4 ± 2.1 nm, which does not vary significantly with ionic strength. This diameter is smaller than that calculated from hydraulic permeabilities and estimated pore densities, suggesting that narrow regions near the pore entrance control ion transport. In addition to simple electrostatic exclusion, streaming potentials lead to differing rejections of Br(-) and acetate in PSS/PAH-modified pores, and of Li(+) and Cs(+) in PSS-modified pores. For these cases, electrical migration of ions toward the feed solution results in higher rejection of the more mobile ion.

Sediment porewater extraction and analysis combining filter tube samplers and capillary electrophoresis.

Careful extraction and analysis of porewater from sediment cores are critical for the investigation of small-scale biogeochemical processes. Firstly, small sample volumes and high spatial resolution are required. Secondly, several chemical species in the anaerobic porewater are sensitive to oxidation when brought in contact with ambient air. Here we present the combination of a special sampling technique and an analytical method for the porewater extraction of a varved sediment core from Lake Baldegg in central Switzerland, using MicroRhizon samplers and a portable capillary electrophoresis (CE) instrument. MicroRhizon filter tubes of 1 mm diameter and 20 mm length are suitable for fast retrieval of particle-free porewater samples directly from the sediment core. Since the time-span between sampling and analysis is less than 20 seconds, oxygen-sensitive Fe(ii) can be analyzed in one go together with Na(+), K(+), Ca(2+), Mg(2+), NH4(+), and Mn(ii) without splitting, acidification or dilution of the sample. The major inorganic cations and anions of the sediment porewater can be determined in less than 15 minutes. Detection limits are in the sub-micromolar concentration range. The capillary electrophoresis instrument used in this study requires sample volumes of only 20 µL. These remarkable small sample volumes allow the minimization of disturbance of the sediment cores and a high spatial resolution of the sediment profile, even in sediments with low water content. The equipment is inexpensive, easy to handle, fully portable and therefore suitable for environmental on-site applications.

Separation of alkali metals using isotachophoresis with cryptand 222 as a leading electrolyte additive.

This work shows how the inclusion of cryptand 222 as a leading electrolyte additive in isotachophoresis affects the electrophoretic mobilities of alkali metal cations. Using isotachophoresis the separation of alkali metals can be difficult due to the similar electrophoretic mobilities of three of the ions: caesium, rubidium and potassium. However, the presence of cryptand 222 in the leading electrolyte retards the mobilities of the caesium, rubidium and potassium to a different extent allowing separations to be made. A novel electrolyte system was formulated which consisted of a leading electrolyte of 10 mM caesium hydroxide, 0.75 mM cryptand 222 buffered to pH 9.4 with glycylglycine and a terminating electrolyte of 10 mM tetrabutylammonium hydroxide. The use of this electrolyte system allowed good separations of mixtures of rubidium, potassium, sodium and lithium to be achieved. The method was also applied to the analysis of edible salt samples.

Cation-π interaction of alkali metal ions with C24 fullerene: a DFT study.

Using first principle calculations, we investigated cation-π interactions between alkali cations (Li(+), Na(+), and K(+)) and pristine C(24) or doped fullerenes of BC(23), and NC(23). The most suitable adsorption site is found to be atop the center of a six-membered ring of the exterior surface of C(24) molecule. Interaction energies of these cations decreased in the order: Li(+) > Na(+) > K(+), with values of -31.82, -22.36, and -15.68 kcal mol(-1), respectively. It was shown that the interaction energies are increased and decreased by impurity doping of B and N atoms in adjacent wall of adsorption site, depending on electron donating or receptivity of the doping atoms.

The effect of alkali and Ce(III) ions on the response properties of benzoxazine supramolecules prepared via molecular assembly.

A series of benzoxazine monomer supramolecules with different substituted groups on their benzene ring was prepared with a Mannich reaction and characterized by FTIR, 1H-NMR and MS. The obtained products were 3,4-dihydro-3-(2'-hydroxyethylene)-6-methyl-2H-benzoxazine (BM1), 3,4-dihydro-3-(2'-hydroxyethylene)-6-ethyl-2H-benz-oxazine (BM2), and 3,4-dihydro-3-(2'-hydroxyethylene)-6-methoxy-2H-benzoxazine (BM3). The efficiency of alkali metal ion extraction from the products was determined with Pedersen's technique, while the complexation of the Ce(III) ion was confirmed by the Job's and the mole ratio methods. The evidence of complex formation between benzoxazine monomers and Ce(III) ions was obtained with FTIR and a computational simulation. Single phase ceria (CeO2) as observed with XRD was successfully prepared by calcinating the Ce(III)-benzoxazine monomer complexes at 600 °C for 2 h. In addition, the geometry of the ceria nanoparticles confirmed by TEM is spherical, with an average diameter of 10-20 nm.

Solid-liquid extraction of alkali metals and organic compounds by leaching of food industry residues.

Leaching was studied for its application in extracting inorganic and organic constituents from fresh fermented grape pomace, air-dried fermented grape pomace and air-dried sugar beet pulp. Samples of each feedstock were leached in water at ambient temperature for 30 or 120 min at dry solid-to-liquid ratios of 1/20 and 1/50 kg/L. Leaching removed 82% of sodium, 86% of potassium, and 76% of chlorine from sugar beet pulp, and reduced total ash concentration in air-dry fermented grape pomace from 8.2% to 2.9% of dry matter, 8.2% to 4.4% in fresh fermented grape pomace, and 12.5% to 5.4% in sugar beet pulp. Glycerol (7-11 mg/dry g), ethanol (131-158 mg/dry g), and acetic acid (24-31 mg/dry g) were also extracted from fermented grape pomace. These results indicate that leaching is a beneficial pretreatment step for improving the quality of food processing residues for thermochemical and biochemical conversion.

Studying the influence of operation parameters on heavy and alkali metals partitioning in flue gases.

In order to study the distribution and partitioning of heavy and alkali metals in the flue gases of a sewage sludge incinerator, an experiment was carried out in a pilot scale combustor. The results indicated that it was feasible to separate part of metals from flue gases by collecting fly ash at different temperatures. On the basis of their separation temperature, heavy and alkali metals could be divided into three groups: group A included Zn, K and P, which converted from gaseous phase to liquid or solid when temperature was above 600 degrees C. Pb and Cu were the metals of group B, with optimum transformation temperature of 400 degrees C. Na and As belonged to group C, with conversion temperatures of 300 degrees C. Moreover, the effect of temperature gradient on heavy and alkali metal gas-solid transformation was also experimentally investigated. It was observed that the temperature gradient could promote the gas-solid conversion of heavy and alkali metals. However, too high a temperature gradient would suppress the formation of fine particles. The peak of conversion rate for K, Pb and Na occurred at 434 degrees C s(-1), while that of P and Cu was 487 degrees C s(-1).

Simultaneous separation of inorganic anions and metal-citrate complexes on a zwitterionic stationary phase with on-column complexation.

The retention and separation selectivity of inorganic anions and on-column derivatised negatively charged citrate or oxalate metal complexes on reversed-phase stationary phases dynamically coated with N-(dodecyl-N,N-dimethylammonio)undecanoate (DDMAU) has been investigated. The retention mechanism for the metal-citrate complexes was predominantly anion exchange, although the amphoteric/zwitterionic nature of the stationary phase coating undoubtedly also contributed to the unusual separation selectivity shown. A mixture of 10 inorganic anions and metal cations was achieved using a 20 cm monolithic DDMAU modified column and a 1 mM citrate eluent, pH 4.0, flow rate equal to 0.8 mL/min. Selectivity was found to be strongly pH dependent, allowing additional scope for manipulation of solute retention, and thus application to complex samples. This is illustrated with the analysis of an acidic mine drainage sample with a range of inorganic anions and transition metal cations, varying significantly in their concentrations levels.

Fabrication and integration of planar electrodes for contactless conductivity detection on polyester-toner electrophoresis microchips.

In this report, we describe the microfabrication and integration of planar electrodes for contactless conductivity detection on polyester-toner (PT) electrophoresis microchips using toner masks. Planar electrodes were fabricated by three simple steps: (i) drawing and laser-printing the electrode geometry on polyester films, (ii) sputtering deposition onto substrates, and (iii) removal of toner layer by a lift-off process. The polyester film with anchored electrodes was integrated to PT electrophoresis microchannels by lamination at 120 degrees C in less than 1 min. The electrodes were designed in an antiparallel configuration with 750 microm width and 750 microm gap between them. The best results were recorded with a frequency of 400 kHz and 10 Vpp using a sinusoidal wave. The analytical performance of the proposed microchip was evaluated by electrophoretic separation of potassium, sodium and lithium in 150 microm wide x 6 microm deep microchannels. Under an electric field of 250 V/cm the analytes were successfully separated in less than 90 s with efficiencies ranging from 7000 to 13,000 plates. The detection limits (S/N = 3) found for K+, Na+, and Li+ were 3.1, 4.3, and 7.2 micromol/L, respectively. Besides the low-cost and instrumental simplicity, the integrated PT chip eliminates the problem of manual alignment and gluing of the electrodes, permitting more robustness and better reproducibility, therefore, more suitable for mass production of electrophoresis microchips.

Preparation, characterization and applications of novel iminodiacetic polyurethane foam (IDA-PUF) for determination and removal of some alkali metal ions from water.

The new type of ion chelating resin (IDA-PUF) has iminodiacetic group that was prepared from polyurethane foam (PUF) by the reaction between primary amine of PUF and monochloro-acetic acid. The IDA-PUF was characterized using infrared spectra, elemental and thermal analysis. The exchange properties and chromatographic behaviour of the new chelating resin were investigated for removal of some alkali metal ions (lithium, sodium and potassium) using batch and column processes. The maximum distribution coefficient (KD) of trace alkali metal ions was in the pH range of 8-10. The kinetics of sorption of the alkali metal ions was found to be fast with average values of half-life of sorption (t1/2) of 4.93min. The values of DeltaG, DeltaS and DeltaH were -3.86kJmol(-1), 57.73Jmol(-1)K(-1) and 14.41kJmol(-1), respectively, which reflects the spontaneous and endothermic nature of ion exchanger process. The average sorption capacity of IDA-PUF is 4.8mmol/g for alkali metal ions, enrichment factors approximately 40 and the recovery 95-100% were also achieved with average value of RSD%=1.67. The proposed method has been successfully applied to preconcentrate, determinate and remove the alkali metal ions from different samples of water.

Preparation and applications of weak acid cation exchanger based on monodisperse poly(ethylvinylbenzene-co-divinylbezene) beads.

New technology is reported here for the synthesis of an effective weak acid-cation exchanger for ion chromatography. Monodisperse macroporous poly(ethylvinylbenzene-co-divinylbezene) (PEVB-DVB) beads of 5 microm diameter were prepared by a two-step swelling and polymerization method. Then carboxyl groups were introduced by polymerization of maleic anhydride with unreacted vinyl groups on the resin beads, followed by hydrolysis of the maleic anhydride groups. A column packed with the carboxylate beads was used to separate alkali and alkaline earth metal ions in a single isocratic run. Separations were found to be better than those with similar resin particles that are simply coated with maleic acid. The columns containing the new particles were 100% compatible with solvents commonly used for HPLC. Additionally, the prepared column was stable and could be used for a long time in a wide range of pH. The column gave good resolution, low detection limits and good repeatability for the separation of common cations. Satisfactory results were also obtained for separations of organic amines and of common cations in rainwater.

On-chip potential gradient detection with a portable capillary electrophoresis system.

A portable chip-CE system with potential gradient detection (PGD) was developed and applied to the determinations of alkali metals and alkaloids. The separation efficiency appeared to be satisfactory and nonaqueous capillary electrophoresis (NACE) proved to be applicable to PGD or conductivity detection. The power supplies, separation and detection were built on a device of 3 kg in weight. A branch channel near the end of the separation channel was designed to perform PGD and make the application of relatively high field strength possible. The study is the first report on the application of PGD on the microchip platform. The design of the chip-CE system shows several advantages, such as simplicity, miniaturization and wide applicability.

Polyelectrolyte-modified short microchannel for cation separation.

Three alkali cations, potassium, sodium, and lithium, have been separated within 15 s in a 1 cm long polymer microchip. The separation microchannel is modified by a polycation, poly(allylammonium chloride), which makes the channel surfaces positively charged leading to a reversed electroosmotic flow (EOF) when compared to bare channels. Due to the decreased apparent mobility of the cations, the separation resolution is improved allowing the use of shorter channels.

Manipulation of separation selectivity for alkali metals and ammonium in ion-exchange capillary electrochromatography using a suspension of cation exchange particles in the electrolyte as a pseudostationary phase.

The viability of using ion-exchange particles as a pseudostationary phase in capillary electrochromatography for the separation of monovalent inorganic cations has been investigated. Using sulfonated polymeric particles (average diameter 225 nm) as the pseudostationary phase, the separation selectivity for alkali metals and ammonium was examined under a range of background electrolyte compositions and employing indirect absorbance detection. Addition of ion-exchange particles to the background electrolyte resulted in a reduction in the observed electrophoretic mobility of the analytes due to the establishment of ion-exchange interaction with the pseudostationary phase, with the decrease in mobilities following the ion-exchange interaction order for these analytes with a sulfonated stationary phase. Increasing the concentration of the particles resulted in a uniform reduction in the electrophoretic mobility of the analytes, similar to that observed in micellar electrokinetic chromatography. Conversely, increasing the concentration of the cationic indirect detection probe (which also acted as an ion-exchange competing cation) resulted in a decrease in the ion-exchange interaction with the particles and a reduction of the relative ion-exchange contribution to the overall separation mechanism. Plots of log[retention factor] versus log[electrolyte concentration] were linear, as is the case for ion-exchange chromatography, but the observed slopes were greater than predicted from ion-exchange theory. Indirect absorbance detection was found to give poor sensitivity due to light scattering effects caused by the particles of pseudostationary phase.