An analytical method is reported for the preparation of K(+) -imprinted nanoparticles using cryptand 222 as the complexing agent, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the crosslinker and 2,2'-azobisisobutyronitrile as the radical initiator. The prepared particles have a diameter of 200-250 nm. The maximum adsorption capacity of potassium ion-imprinted polymer particles was 120 μmol/g. The optimum pH for quantitative extraction was 9.0. The nature of the eluent, eluent concentration, adsorption and desorption times, weight of the polymer material, aqueous phase, and desorption volumes were also studied. The relative selectivity coefficients of K(+) /Li(+) , K(+) /Na(+) , K(+) /Rb(+) and K(+) /Cs(+) were 48.10, 4.80, 29.70, and 43.4, respectively. The relative standard deviation and limit of detection of the method were obtained 1.61% and 4.62 ng/L, respectively. Finally, the method was applied for the determination of potassium ions from different samples using flame photometry.
In this article, organic/inorganic membrane was prepared for gas separation by incorporating dodecatungstophosphric acid (PWA) into the base polymer. Flatsheet composite membranes were produced via dry-phase inversion method. In the first stage, the effects of PWA concentration on morphology and performance of polyvinyl alcohol (PVA) membranes were elucidated. For this stage, the preparation of membranes was carried out at constant temperature of 40 C. The porosity of the prepared membrane was slightly increased with addition of PWA. By increasing the PWA concentration up to 6 wt % in the membrane recipe, the permeability of N 2 , O 2 , and air was improved from 50,000 (for no addition of PWA) to around 160,000, 140,000, and 80,000 L m À2 h
À1, respectively. For H 2 , this was enhanced from 110,000 to 230,000 L m À2 h À1 . The ideal selectivity of the membrane was slightly improved for N 2 /air (from 1 to 1.2). For N 2 /O 2 pair, the initial drop (from 2.5 to 1.5) was followed by a slight increase (1.5-1.9). Moreover, the selectivity was decreased for H 2 /air (from 2.8 to 1.8) and H 2 /N 2 (from 2.2 to 1.7) by increasing the PWA concentration. The 10 wt % PVA membrane with 6 wt % PWA demonstrated superior performance compared with the other compositions. In summary, the presence of PWA in the casting solution results in lower flux for O 2 and higher selectivity for H 2 /O 2 pair. In the second stage, the effects of solvent evaporation temperature (10, 27, 40, and 80 C) on morphology and performance of the membranes were studied. By increasing the temperature, the number and size of voids were increased.
In the present paper, organic/inorganic membrane has been prepared for gas separation by incorporating heteropolyacids (ΗΡΑ) such as 12-phosphotungstic acid (PWA) into the base polymer. Flat-sheet membranes were prepared using polyethersulfone (PES) dissolved in Ν, Ν-dimethylacetamide (DMAc) with and without the addition of PWA. The membranes were prepared from quaternary (PES/PWA/DMAc/water) and ternary (PES/PWA/DMAc) systems by wet and dry (solvent evaporation) techniques. Composite membranes were produced via a two-stage wet phase inversion method. The skin layer was synthesized from ternary (PVA/PWA/II 2 O) system on the surface of PES membrane as the sub layer, using dip coating technique. The permeability and selectivity of H 2 , N 2 , O 2 and air were tested. In dry method, the porosity of the prepared membrane was slightly increased by addition of PWA. The increased porosity results in flux improvement. By increasing the concentration of PWA in the wet procedure, the channel-like structure appeared. The presence of PWA in the casting solution results in lower flux for O 2 gas and higher selectivity for S pair.
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