Selective sorption of diethyl phthalate on pH-responsive,molecularly imprinted polymeric adsorbents

ABSTRACT

A novel synthetic route for preparation of pH-responsive molecularly imprinted adsorbents for separation of diethyl phthalate (DEP) is proposed. Polymers were synthesized using acrylic acid (AAc) and methyl methacrylate (MMA) crosslinked using ethylene glycol dimethacrylate (EGDMA) or divinylbenzene (DVB). The carried out tests revealed the pH-driven recognition of synthesized sorbents toward DEP. It was found that sorbents derived from mixture of 30% AAc:MMA (1:1) and 70 wt.% of DVB in the presence of 7 wt.% of template were the best. The DEP sorption took the highest value (85 mg g^?1) at pH = 5, while desorption with extent of 92% was the most efficient at pH = 8.     

Removal of Bisphenol A from Aqueous Solution by Molecularly Imprinted Polymers

Uniformly sized polymeric molecularly imprinted microspheres have been synthesized by membrane emulsification and suspension polymerization of methyl methacrylate and ethyl glycol dimethacrylate in the presence of bisphenol A as a template. At the beginning the best monomer compositions were selected by bulk polymerization of eight different mixtures of monomer and crosslinking agent. For the selected compositions that had the highest affinity to bisphenol A, a two-step process composed of membrane emulsification and suspension polymerization was used. Materials prepared by the two-step process showed the higher efficiency to the bisphenol A removal than their analogues prepared by bulk polymerization. The best material was synthesized from a mixture of methyl methacrylate and ethylene glycol dimethacrylate as 4:6 in the presence of n-octane as a solvent, and with 3 wt.% of bisphenol A. The logK_BPA value for this sample was 4.9. The experimental sorption isotherms were fitted by Scatchard plots and heterogeneity of the binding sites was determined. The selectivity of the sorbents to other phenols was demonstrated.     

Synthesis and non‐isothermal crystallization behavior of poly(ethylene phthalate‐co‐terephthalate)s

A series of poly(ethylene phthalate‐co‐terephthalate)s were synthesized by melt polycondensation of ethylene glycol (EG) with dimethyl phthalate (DMP) and dimethyl terephthalate (DMT) in various proportions. The DMT‐rich polymers were obtained with reasonably high molecular weights, whereas the DMP‐rich polymers were synthesized with relatively low molecular weights due to steric effects associated with the highly kinked DMP monomer. The compositions and thermal properties of the polymers were determined. The copolymers containing DMP in amounts of ≤ 21 mol% were crystallizable, whereas the other polymers were not. All the polymers exhibited a single glass transition temperature. Analysis of the measured glass transition temperatures and crystal melting temperatures confirmed that the DMT‐rich copolymers are random copolymers. The non‐isothermal crystallization behaviors of the DMT‐rich copolymers were investigated by calorimetry and modified Avrami analysis. The Avrami exponents n were found to range from 2.7 to 3.8, suggesting that the copolymers crystallize via a heterogeneous nucleation and spherulitic growth mechanism; that is, the incorporation of DMP units as the minor component does not change the growth mechanism of the copolymers. In addition, the activation energies of the crystallizations of the copolymers were determined; the copolymers were found to have higher activation energies than the PET homopolymer. Polym. Eng. Sci. 44:1682–1691, 2004. © 2004 Society of Plastics Engineers.     

A low-cost and environment friendly chitosan/aluminum hydroxide bead adsorbent for fluoride removal from aqueous solutions

A novel low-cost adsorbent named chitosan/Al(OH)₃·(CS/Al(OH)₃) bead was successfully prepared by employing AlCl₃·6H₂O aqueous solution as the solvent for CS. The CS/Al(OH)₃ beads were used for fluoride removal from water. The beads were synthesized using the chitosan and aluminum chloride with the mass ratio of 2:1 as the precursor and in situ generation of aluminum hydroxide sorbents in sodium hydroxide solution. Then, the beads were washed with distilled water to neutral and freeze dried. The sorbents were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), Fourier transform infrared spectrometry (FTIR), and X-ray diffractometry (XRD), respectively. Batch adsorption experiments were conducted to evaluate the parameters that affected the defluoridation capacity. The influencing parameters including pH, co-existing ions in water and initial temperature of the adsorption process were studied. The influence of temperature confirmed that the adsorption was spontaneous and endothermic. The adsorption isotherm of fluoride followed Langmuir isotherm model and the sorption kinetics was more suitable for pseudo-second-order kinetic model. The defluoridation capacity of chitosan/Al(OH)₃ calculated using Langmuir model was 23.06 mg/g (293 K, pH 4). The experimental results showed that the CS/Al(OH)₃ bead adsorbent is promising for the fluoride adsorption.     

pH-responsive molecularly imprinted polymer for sorption and rapid desorption of dibutyl phthalate

The pH-responsive molecularly imprinted polymers (SR-MIPs) for the removal of dibutyl phthalate (DBP) were obtained. The polymers were synthesized using methyl methacrylate, methacrylic acid, divinylbenzene, and a template mixed at different ratios allowing to optimize the process. The so-prepared SR-MIPs were evaluated at various pH values in processes of DBP sorption. The studies covered evaluation of uptake capacity, sorption kinetics, selectivity, and elution. The imprinted samples are characterized by improved factors comparing to their non-imprinted analogues, revealing also pH-sensitivity. The highest removal of DBP (130 mg g^?1) was achieved at pH = 6, while pH-driven desorption (90%) was the most efficient at pH = 8.     

Fine polymer imprinted layers for the monitoring of bisphenol A in aqueous solutions

The present work proposes the use of molecularly imprinted polymer layers (MIPLs) on dehydrochlorinated poly(vinyl chloride) (DHPVC) particles, which could serve as new materials for the separation of bisphenol A (BPA). The best material with MIPLs was obtained using a mixture of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) with the molar ratio of 4:6 in n-octane as the solvent and with 7 wt.% of BPA, which were grafted onto DHPVC particles. The synthesized materials were investigated for their possible application in the monitoring of BPA contamination in real samples received after the treatment of can of some popular beverages.     

气相色谱法测定6种邻苯二甲酸酯痕量组分的固相萃取条件研究

利用固相萃取技术富集了水中6种邻苯二甲酸酯类:邻苯二甲酸二(2-乙基己基)酯(DEHP)、邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸二丁酯(DBP)、邻苯二甲酸二辛酯(DOP)、邻苯二甲酸丁基苄基酯(BBP)。借助均匀设计法及计算机回归建模优化技术对6种邻苯二甲酸酯类的固相萃取条件进行了设计与优化,得到最佳固相萃取条件为:洗脱剂配比(正己烷与丙酮的体积比)30∶1,洗脱体积2 mL,洗脱速率为4 mL/min,上样速率8 mL/min。富集后的样品用带电子捕获器的毛细管气相色谱检测,方法的线性范围为1~1 000μg/L(DMP、DEP、DOP),0.2~100μg/L(DBP、DEHP),0.1~100μg/L(BBP);线性回归方程的相关系数为0.997 0~1.000,检测限为0.01~0.4μg/L,方法回收率为69.0%~117.0%,相对标准偏差为2.2%~9.5%。     

Solid Phase Extraction of Phenol on Zeolitic Material: Batch Sorption and Column Dynamics

The solid phase extraction of phenol using hydrothermal (CZBFA) and fusion synthesized zeolitic materials (FZBFA) were carried out by batch and column mode. The chemical composition and the functional groups of synthesized zeolitic materials were investigated by XRF and FTIR. The major zeolitic phases and morphology were identified by PXRD and SEM techniques. The isotherms were estimated for the nature of sorption of phenols on sorbents. Thermodynamics parameters exhibited the endothermic nature of sorption. The phenol sequestration is highest for FZBFA as compare to bentonite, mud, and resin sorbents but lower than the activated carbon. Desorption of phenol is highest for BFA with 0.5 M NaOH.     

Alginate and Algal-Based Beads for the Sorption of Metal Cations: Cu(II) and Pb(II)

Alginate and algal-biomass (Laminaria digitata) beads were prepared by homogeneous Ca ionotropic gelation. In addition, glutaraldehyde-crosslinked poly (ethyleneimine) (PEI) was incorporated into algal beads. The three sorbents were characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX): the sorption occurs in the whole mass of the sorbents. Sorption experiments were conducted to evaluate the impact of pH, sorption isotherms, and uptake kinetics. A special attention was paid to the effect of drying (air-drying vs. freeze-drying) on the mass transfer properties. For alginate, freeze drying is required for maintaining the porosity of the hydrogel, while for algal-based sorbents the swelling of the material minimizes the impact of the drying procedure. The maximum sorption capacities observed from experiments were 415, 296 and 218 mg Pb g⁻¹ and 112, 77 and 67 mg Cu g⁻¹ for alginate, algal and algal/PEI beads respectively. Though the sorption capacities of algal-beads decreased slightly (compared to alginate beads), the greener and cheaper one-pot synthesis of algal beads makes this sorbent more competitive for environmental applications. PEI in algal beads decreases the sorption properties in the case of the sorption of metal cations under selected experimental conditions.     

Separation Characteristics of Dimethylformamide/Water Mixtures through Alginate Membranes by Pervaporation,Vapor Permeation and Vapor Permeation with Temperature Difference Methods

Abstract

In this study permeation and separation characteristics of dimethylformamide (DMF)/water mixtures were investigated by pervaporation (PV), vapor permeation (VP), and vapor permeation with temperature difference (TDVP) methods using alginate membranes crosslinked with calcium chloride. The effects of membrane thickness (30–90 µm), feed composition (0–100 wt%), operating temperature (30–50°C) on the permeation rates and separation factors were investigated. The permeation rate was found to be inversely proportional to the membrane thickness whereas separation factor increased as the membrane thickness was increased. It was observed that the permeation rates in VP and TDVP were lower than in PV however the highest separation factors were obtained with TDVP method. Alginate membranes gave permeation rates of 0.97–1.2 kg/m² h and separation factors of 17–63 depending on the operation conditions and the method. In addition, sorption‐diffusion properties of the alginate membranes were investigated at the operating temperature and the feed composition. It was found that the sorption selectivity was dominant factor for the separating of DMF/water mixtures.     

Ion‐selective Imprinted Superporous Monolith for Cadmium Removal from Human Plasma

Abstract

Molecular recognition based separation systems have received much attention because of their high selectivity for target molecules. Molecular imprinting has been recognized as a promising technique for the development of affinity adsorbents. Molecularly imprinted polymers (MIP) are easy to prepare, stable, inexpensive, and capable of molecular recognition. Cadmium is a carcinogenic and mutagenic element. The limit value of cadmium in blood should be no higher than 50 pg/L when exposure to cadmium is unavoidable in industry. There is no specific treatment available for acute or chronic metal poisoning. Besides supportive therapy and hemodialysis, metal poisoning is often treated with commercially available chelating agents including EDTA and dimercaprol. However, there is histopathological evidence for increased toxicity in animals when these agents are utilized. The aim of this study is to prepare superporous ion‐imprinted polymer monolith which can be used for the selective removal of Cd²⁺ ions from Cd²⁺‐overdosed human plasma. N‐methacryloly‐(L)‐cysteinemethylester (MAC) was chosen as the complexing monomer. In the first step, MAC synthesized by using methacryloyl chloride and cysteine. Cd²⁺ was complexed with MAC monomer and the Cd²⁺‐imprinted poly(HEMA‐MAC) monoliths were synthesized by bulk polymerization. After that, Cd²⁺ ions were removed by 0.1 M thiourea and 0.1 M HNO₃ solutions, respectively. Cd²⁺‐imprinted poly(HEMA‐MAC) monoliths had a specific surface area of 226.8 m²/g and the swelling ratio was determined to be 76%. According to the elemental analysis results, monoliths contain approximately 58.3 µmol/g of MAC. The maximum adsorption capacity for Cd²⁺ ions was 26.6 µmol/g of the dry weight of monolith. The adsorption capacity decreased significantly from 23.25 µmol/g to 3.08 µmol/g polymer with the increase of the flow‐rate from 1 mL/min to 4 mL/min. The Cd²⁺‐imprinted poly(HEMA‐MAC) monolith could be used many times without decreasing their adsorption capacities significantly.     

pH‐sensitive uniform gel beads for DNA adsorption

Uniform gel beads 3 mm in diameter were obtained by the suspension polymerization of an amine functionalized monomer, N‐3‐(dimethyl amino)propylmethacrylamide (DMAPM). The polymerization of DMAPM in the form of uniform droplets could be achieved at room temperature in an aqueous dispersion medium by using Ca–alginate gel as the polymerization mold. In this preparation, potassium persulfate/tetramethyl ethylenediamine and sodium alginate/calcium chloride were used as the redox initiator and the stabilizer systems, respectively. The crosslinked DMAPM gel beads exhibited pH‐sensitive, reversible swelling–deswelling behavior. The uniform gel beads were also obtained by the copolymerization of DMAPM and acrylamide (AA) in the same polymerization system. Although copolymer gel beads with higher pH sensitivities were obtained with increasing feed concentration of DMAPM, the total monomer conversion decreased. Crosslinked DMAPM and DMAPM–AA copolymer gel beads were utilized as sorbents for DNA adsorption. The gel beads produced with higher DMAPM feed concentration exhibited higher equilibrium DNA adsorption capacity. The DNA equilibrium adsorption capacities up to 50 mg DNA/g dry gel could be achieved with the crosslinked DMAPM gel beads. This value was reasonably higher relative to the previously reported adsorption capacities of known sorbents. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3154–3161, 2000     

Synthesis and study of optimization of amidoximated PAN‐DVB‐EGDMA beads for the sorption of uranium from aqueous media

Environmental and economic considerations have made the sorption of uranium from aqueous media a very time demanding area of research from last few decades. In this particular work, amidoximated polyacrylonitrile beads were synthesized by the reaction of hydroxyl amine hydrochloride (OH‐NH₂.HCl) with macroporous crosslinked polyacrylonitrile beads, prepared through suspension polymerization techniques, using acrylonitrile (AN) as monomer and divinylbenzene and ethyleneglycoldimethacrylate as crosslinkers, in a variety of relative compositions, to modify suitably the hydrophilicity and physicochemical stability. These beads were also characterized by FT‐IR, scanning electron microscope, and thermogravimetric analysis–differential scanning calorimetry techniques to explain the morphology and chemical functionality. The beads reached its saturation capacity towards uranyl ions well within 1 h of equilibration at ~25°C, under near neutral pH conditions and the observed maximum sorption capacity was found to be ~18 mg g^?1. The beads were also used for the sorption of uranium from various real water samples and showed good sorption from these samples. Reusability of the beads was also established up to the studied four cycles. These synthesized beads can potentially serve the dual purpose of the decontamination of uranium contaminated potable well water as well as to treat acidic radioactive waste generated in nuclear industry before final discharge to environment. POLYM. ENG. SCI., 59:863–872, 2019. © 2018 Society of Plastics Engineers     

Determination of trace amounts of Co(II) after preconcentration with surface ion imprinted sorbent based on activated carbon

In this study, by using surface ion imprinting technique, Co(II)-imprinted activated carbon was synthesized as a new sorbent in order to use in solid phase extraction method. Several parameters were investigated and optimum experimental conditions were determined. Synthesized sorbent was characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Thermogravimetric Analysis and Brunaer, Emmet, and Teller techniques. The maximum adsorption capacity of imprinted and nonimprinted sorbents were found as 833.3 mg/g and 188.7 mg/g respectively. The limit of detection, the limit of quantification and relative standart deviation were found as 0.066 µg/L, 5.91 µg/L and 5.65% respectively.     

Synthesis of sulfur nanoparticles-loaded alumina as a low-cost sorbent for the preconcentration of nickel from real samples

This study reports a simple method for the synthesis of α-sulfur-nanoparticles-loaded alumina as a reliable kind of sorbents in solid-phase extraction (SPE) methods for the preconcentration and determination of trace levels of Ni(II) from real samples. The most important advantage of this technique is not using the ligand as a complexing agent and hence the disadvantages of other SPE methods have been avoided. The calibration graph was linear over the range of 0.66–100 µg/L and the relative standard deviation (RSD) of 1.98% at 50 µg/L was obtained. The limit of detection (LOD) and preconcentration factor (PF) were obtained as 0.22 µg/L and 250, respectively. The maximum adsorption capacity of the adsorbent was found to be 18 mg/g for Ni(II).     

Preparation and characterization of uniform molecularly imprinted polymer beads for separation of triazine herbicides

Uniform molecularly imprinted polymer beads were synthesized by precipitation polymerization for separation of triazine herbicides. A series of imprinted polymers were prepared using ametryn as template and divinylbenzene as crosslinking monomer, in combination with three different functional monomers under different solvent conditions. Under optimized reaction conditions, we obtained uniform molecularly imprinted polymer microspheres that display favorable molecular binding selectivity for triazine herbicides. The imprinted polymer beads synthesized using methacrylic acid as functional monomer in a mixture of methyl ethyl ketone and heptane showed the best results in terms of particle size distribution and molecular selectivity. Compared with nonimprinted polymer microspheres, the imprinted microspheres displayed significantly higher binding for a group of triazine herbicides including atrazine, simazine, propazine, ametryn, prometryn, and terbutryn. For the first time, precipitation polymerization has been used to produce highly uniform imprinted microspheres suitable for affinity separation of triazine herbicides. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and evaluation of aconitine imprinted microspheres and its application to body fluid samples

To extract aconitine from body fluid samples, aconitine‐molecularly imprinted polymer microspheres with the optimum molar ratios of template/monomer/cross‐linker (1:8:40) as selective sorbents were synthesized by precipitation polymerization. Excellent retention of aconitine on the molecularly imprinted microspheres (MIMs) cartridge was achieved by optimizing the MISPE process, and the binding capacity reached 0.802mg/g, yielding an imprinting factor of 4.76. The MIMs also showed high selectivity for aconitum alkaloids, but not for other kinds of poisonous alkaloids. High recoveries (>89%) for aconitine, hypaconitine, and mesaconitine were got in spiked serum samples. The working curves show linear dependence on aconitine concentration in the range of 2.0–0.1 µg/mL, and the detection limits of aconitine, hypaconitine, and mesaconitine were 16.7, 18.3, 10.2 ng mL^–1, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Uranium sorption from aqueous solutions using polyacrylamide-based chelating sorbents

ABSTRACT

This article introduces an investigation on the sorption power of two polyacrylamide-based chelating sorbents for uranium ion removal from aqueous solutions. The studied sorption parameters involved pH, contact time, initial uranium concentration, and polymer dosage. The results revealed that a maximum uptake percentage of 65.3 mg/g and 20.1 mg/g for polymers I and II, respectively, could be obtained at pH 4 with 120 min shaking time. Based on isotherm, kinetic, and thermodynamic studies, the sorption process of uranium on the chelating polymers is said to follow Langmuir isotherm model with pseudo second-order mechanism and exothermic nature.     

Crystalline complex between poly(γ-methyl l-glutamate) and dimethyl phthalate

The crystalline complex between poly(γ-methyl l-glutamate) (PMLG) and dimethyl phthalate (DMP) has been formed in films cast from a solution in dichloroethane. It has the stoichiometry of 1 mol of DMP to three or four residues of PMLG and shows two definite characteristics in X-ray diffraction patterns; one is the large hexagonal unit cell with the edge of around 28 Å and another the ‘extra’ 5.07 Å meridional reflection which can not be interpreted by a PMLG α-helical conformation. The structural examination for the films with various DMP contents is carried out by X-ray, viscoelastic, and d.s.c. measurements and the following structure is proposed for the crystalline complex. Four PMLG are associated to form a group which is hexagonally packed and DMP molecules, located in the gaps between groups, form a specific favourable helical structure along PMLG chains in which the van der Waals stacking of benzene rings of DMP is significant.     

Preparation of Dicarboxylic Acid Containing Sulfonamide Based Resin and Removal of Basic Dyes

Polymer and dye interaction leading to polymer-dye complex formation exhibits many interesting and important practical features. For this purpose, dicarboxylic acid containing resin was prepared in two steps starting from poly (styrene-divinyl benzene) (PS-DVB) (10% crosslinking) based beads with a particle size of 400-590 µm, according to the synthetic protocol; chlorosulfonation, sulfamidation with iminodiacetic acid. Dye extraction experiments were carried out by contacting wetted resin samples with aqueous dye solutions at room temperature. Capacities were determined by colorimetric analysis of the residual dye content. Dye sorption capacity of the resin was found to be (0.67-0.63 g g^?1 resin). This material is also able to remove the cationic dyes completely even from highly diluted aqueous dye solutions.