Solvent-impregnated resins (SIRs) – Methods of preparation and their applications

Interest in the development of solvent-impregnated resins (SIRs) and their applications for the separation of metal ions and organic compounds from water in the form of a hybrid polymeric adsorbent material has intensified over the past thirty years. SIRs are particulate adsorbers that possess a combination of the advantageous features of both liquid–liquid extraction and ion exchange and this renders them applicable to a wide range of potential liquid–solid separation and recovery processes. This paper reviews the extensive published literature on methods of synthesis of SIRs, attempts to stabilize hybrid solvent-impregnated resins and various applications of SIRs.     

Porous dye affinity beads for albumin separation from human plasma

Porous polymeric beads were obtained by the suspension polymerization of 2‐hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA). Poly(HEMA–EGDMA) beads were characterized by surfacearea measurements, swelling studies, FTIR, scanning electron microscopy (SEM), and elemental analysis. Poly (HEMA–EGDMA) beads had a specific surface area of 56 m²/g. SEM observations showed that the poly(HEMA–EGDMA) beads abounded macropores. Poly(HEMA–EGDMA) beads with a swelling ratio of 55%, and containing different amounts of Reactive Red 120 (9.2–39.8 μmol/g) were used in the adsorption/desorption of human serum albumin (HSA) from aqueous solutions and human plasma. The nonspecific adsorption of HSA was very low (0.2 mg/g). The maximum HSA adsorption amount from aqueous solution in phosphate buffer was 60.1 mg/g at pH 5.0. Higher HSA adsorption value was obtained from human plasma (up to 95.7 mg/g) with a purity of 88%. The equilibrium monolayer adsorption amount, Q_max was determined as 172.4 mg/g. The dimensionless separation factor (R_L) value shows that the adsorption behavior of HSA onto the Reactive Red 120 attached poly(HEMA–EGDMA) beads was favorable (0 < R_L < 1). Desorption of HSA from Reactive Red 120 attached poly (HEMA–EGDMA) beads was performed using 0.1M Tris/HCl buffer containing 0.5M NaCl. It was observed that HSA could be repeatedly adsorbed and desorbed with Reactive Red 120‐attached poly(HEMA–EGDMA) beads without significant loss in the adsorption amount. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

ELECTRO-DEIONIZATION OF Cr (VI)-CONTAINING SOLUTION. PART I: CHROMIUM TRANSPORT THROUGH GRANULATED INORGANIC ION-EXCHANGER

Kinetics of Cr (VI) → OH^? exchange on both hydrogel and xerogel of hydrated zirconium dioxide was investigated. Self-diffusion coefficient of Cr (VI) species has been determined by analysis of kinetic curves. Transport of Cr (VI) anions through the inorganic ion exchangers under the influence of applied voltage was also researched. In the case of hydrogel, the ions are transported mainly through the solid phase. Diffusion coefficient of chromate anions through this material was estimated as 9.00 × 10^?12 m² s^?1. This is in agreement with self-diffusion coefficient of Cr (VI) obtained from kinetic measurements (1.60 × 10^?12–9.92 × 10^?12 m² s^?1). Owing to the rather high mobility of Cr (VI) through hydrogel of hydrated zirconium dioxide, this material was recommended for electro-deionization processes. On the other hand, the use of polymer anion-exchange membrane must be excluded to prevent poisoning of the inorganic ion exchanger with Cr (III) cations to be formed during chemical interaction of Cr (VI) with organic materials.     

Removal of cadmium from phosphoric acid solution by solvent-impregnated resins (sirs) - sorption kinetics and equilibria studies

Cyanex-302 (bis [2,4,4-trimethylpentyl] monothiophosphinic acid) was impregnated into macroporous Diaion HP-10 and HP-1MG polymeric resin matrices and used as an extractant to recover cadmium from concentrated phosphoric acid. The optimum conditions for batchwise extraction of cadmium were established, and equilibrium data in the concentration range 0-200 mg/L Cd were obtained in 40% H 3 PO 4 solution. A Langmuir adsorption isotherm gave the best fit of the adsorption equilibrium data. A preliminary kinetic study was carried out in order to elucidate the rate-controllingmechanism. The uptake of trace cadmium onto Cyanex 302 containing solvent-impregnated resins from 40% phosphoric acid appears to be particle diffusion controlled.     

Microbial corrosion of Ni–Cu alloys by Aeromonas eucrenophila bacterium

The corrosion behavior of Ni–Cu alloy in Nutrient Broth medium (peptone from meat 5.0 g, meat extract (N source) 3.0 g, and sodium chloride 6.0 g in 1 L) and in the presence of Aeromonas eucrenophila, isolated from water treatment system, has been studied using electrochemical techniques. Results showed that the polarization curves exhibiting a cathodic shift of the corrosion potential confirmed the increase in the corrosion rates. According to EIS data lower Q_CPE value for 5 h indicates surface inhomogeneity resulting from surface metal roughening, which is the likely cause of the enhanced dissolution of the metal also observed in SEM micrographs. In addition, the pH values of the medium did not change throughout the experiment; however, after immersion the pH value decreased to acidic value and caused corrosion.     

Effects of process variables for biodiesel production by transesterification

In this study, biodiesel production from various vegetable oils by transesterification was studied, to determine the optimum conditions. Experiments were carried out by using different kinds of catalysts (sodium hydroxide, potassium hydroxide, barium hydroxide, pyrolitic coke and wood ash) and feedstocks (corn oil, sunflower oil, soybean oil, olive pomace oil and cottonseed oil) at 65 °C and an agitation speed of 1000 rpm. The neutralization step with controlled pH was performed by treatment with phosphoric acid. An experimental design was used to evaluate the effects of the parameters such as types of vegetable oils, kinds of catalysts, reaction time, alcohol/oil volumetric ratio and amount of catalyst, on the methyl ester conversion. Using response surface methodology, a quadratic polynomial equation was obtained by multiple regression analysis. It was found that catalyst concentration was the most effective parameter. Sodium hydroxide and potassium hydroxide exhibited a superior catalytic behavior, whereas pyrolitic coke and wood ash had to be used in excess amount or for prolonged reaction times. Moreover, the properties such as viscosity, density, calorific value, acid value, and refractive index of the biodiesel were measured. The tri‐, di‐, monoacylglycerols and glycerol residuals in the methyl esters produced were also quantified by GC analysis.     

Hydroxyapatite-chitosan biocomposites synthesized in the simulated body fluid and their drug loading studies

Hydroxyapatite (HAp) is a bioceramic applied in the biomedical areas, such as matrices for drug release control. Chitosan (CTS), a natural polymer, is another material has been widely investigated for its potential use in the drug delivery systems. In this study, the composites of HAp-CTS are produced in order to investigate their drug loading and release studies. First of all, HAp-CTS composites are produced in the presence of simulated body fluid (SBF). Analysis confirmed the structure of HAp-CTS composites. Secondly, composites are encapsulated with 5-Fluorouracil (5-FU). The weight ratio of CTS is varied to realize its effect on drug loading of 5-Fluorouracil, a cancer drug, for the ratios of 1:1, 1:2 and 1:4 of HAp-CTS. The weight ratio giving the greatest drug load efficiency is selected for the last step of the study. Crosslinking agent, glutaraldehyde, are changed from 0 to 5% on the selected sample, then, drug loading is examined again in various environment owing different pH. Furthermore, drug release studies are conducted. To understand the structure and morphology of the samples, XRD, FTIR, SEM and Uv-Spectrum are applied. It is observed that weight ratio of polymer and crosslinking agent can be manipulated to adjust drug loading. Release kinetics are shown the Fickian diffusion. This new produced material can be applicable for drug delivery.     

A robust asset–liability management framework for investment products with guarantees

This paper suggests a robust asset–liability management framework for investment products with guarantees, such as guaranteed investment contracts and equity-linked notes. Stochastic programming and robust optimization approaches are introduced to deal with data uncertainty in asset returns and interest rates. The statistical properties of the probability distributions of uncertain parameters are incorporated in the model through appropriately selected symmetric and asymmetric uncertainty sets. Practical data-driven approaches for implementation of the robust models are also discussed. Numerical results using generated and real market data are presented to illustrate the performance of the robust asset–liability management strategies. The robust investment strategies show better performance in unfavorable market regimes than traditional stochastic programming approaches. The effectiveness of robust investment strategies can be improved by calibrating carefully the shape and the size of the uncertainty sets for asset returns.     

Trace elements in edible tissues of three shrimp species (Penaeus semisulcatus,Parapenaeus longirostris and Paleomon serratus)

Accumulation levels of trace elements in edible tissues of three shrimp species (Penaeus semisulcatus, Parapenaeus longirostris and Paleomon serratus) from the Gulf of Antalya, Turkey were investigated. Copper (Cu), cadmium (Cd), zinc (Zn), iron (Fe) and manganese (Mn) concentrations were determined by atomic absorption spectrophotometry. The lowest Cu (1.33 mg kg^?1) and Cd (0.23 mg kg^?1) and highest Mn (1.52 mg kg^?1) concentrations were found in P. longirostris, the lowest Zn (6.25 mg kg^?1), Fe (1.84 mg kg^?1) and Mn (0.25 mg kg^?1) concentrations in P. serratus and the highest Cu (6.19 mg kg^?1), Cd (2.36 mg kg^?1), Zn (30.84 mg kg^?1) and Fe (33.89 mg kg^?1) concentrations in P. semisulcatus. The Cd levels detected in P. semisulcatus and P. serratus were above legislative limits. Our results show that there were significant differences in trace element concentrations among the three shrimp species. The highest levels of the five trace elements investigated, with the exception of Mn, were found in edible tissue of P. semisulcatus. Copyright © 2007 Society of Chemical Industry     

Synthesis of polydimethylsiloxane‐block‐polystyrene‐block‐polydimethylsiloxane via polysiloxane‐based macroinitiator in supercritical CO2

Polydimethylsiloxane‐block‐polystyrene‐block‐polydimethylsiloxane (PDMS‐b‐PS‐b‐PDMS) was synthesized by the radical polymerization of styrene using a polydimethylsiloxane‐based macroazoinitiator (PDMS MAI) in supercritical CO₂. PDMS MAI was synthesized by reacting hydroxy‐terminated PDMS and 4,4′‐azobis(4‐cyanopentanoyl chloride) (ACPC) having a thermodegradable azo‐linkage at room temperature. The polymerization of styrene initiated by PDMS MAI was investigated in a batch system using supercritical CO₂ as the reaction medium. PDMS MAI was found to behave as a polyazoinitiator for radical block copolymerization of styrene, but not as a surfactant. The response surface methodology was used to design the experiments. The parameters used were pressure, temperature, PDMS MAI concentration and reaction time. These parameters were investigated at three levels (?1, 0 and 1). The dependent variable was taken as the polymerization yield of styrene. PDMS MAI and PDMS‐b‐PS‐b‐PDMS copolymers obtained were characterized by proton nuclear magnetic resonance and infrared spectroscopy. The number‐ and weight‐average molecular weights of block copolymers were determined by gel permeation chromatography. Copyright © 2004 Society of Chemical Industry