Kinetics study of oil sorption with open‐cell polypropylene/polyolefin elastomer blend foams prepared via continuous extrusion foaming

The objective of the present work was to study the sorption kinetics of open‐cell polypropylene/polyolefin elastomer (PP/POE) blend foams. First, open‐cell PP/POE foams of different cell structures were prepared by controlling the foaming temperature via a continuous extrusion foaming process. Second, the effect of the cell structures on the sorption process, rate, and capacity was studied. Pseudo‐first order and pseudo‐second order models were applied to study the sorption kinetics of the PP/POE foams for cyclohexane. Third, the sorption rate and sorption capacity by both volume and weight of the PP/POE foam for different oils and solvents were studied to show how the intrinsic properties of the testing oils and solvents affected the sorption performance. The results showed that the sorption with the PP/POE foams followed the pseudo‐second order kinetics model. Both the cell structures of the foams and the intrinsic properties of the testing oils and solvents affected the sorption performance. For the same testing oil, a higher open‐cell content in the foam was favorable for a higher sorption rate, and a higher void fraction was favorable for a higher sorption capacity. For the same foam, a lower viscosity of the testing oil was favorable for a higher sorption rate. The sorption capacity by volume was closely related to the viscosity of the testing oil, while both the viscosity and the density of the testing oil determined the sorption capacity by weight.     

Sorption of iron(III) and iron(II) from acidic chloride solutions by polyether and polyester type polyurethane foams

Summary Iron(III) is sorbed by polyether type open-cell polyurethane foams from HCl solutions of 4 mol/l or higher. The capacity of the foams is around 50 mg·l^–1. The iron (III) sorbed can be eluted from the foam with 0.01 mol/l HCl or distilled water. An optimization of the sorption conditions showed that the process can be used for analytical applications. The polyurethane foam sorbents examined did not sorb iron(II). The mechanism of sorption by polyether foams seems to follow a mechanism similar to that of the extraction of iron(III) by etheric solvents.     

The recovery of gold from thiourea solutions with open-cell polyurethane foams

The recovery of the gold-thiourea complex from aqueous solutions with TBP-loaded and unloaded polyurethane foams was investigated in batch experiments. The rates of adsorption of the gold complex on various types of loaded and unloaded foams were studied in detail and compared with the rate of adsorption on active carbon. Loaded and unloaded polyurethane foams of the polyether or polyester type behaved similarly to active carbon. The adsorption capacity of the foams was lower than that of active carbon but the use of foam simplifies the procedure by eliminating the filtration process which is necessary with carbon.     

Kinetics and retention characteristics of some nitrophenols onto polyurethane foams

The kinetics of sorption of the nitrophenols by the unloaded polyurethane foams (PUFs) were found fast, reached equilibrium in few minutes and followed a first-order rate equation with an overall rate constant k in the range (0.16-0.21)±0.01 min⁻¹. The retention of the tested nitrophenols by the unloaded foams is consistent with the “solvent extraction” mechanism. However, the sorption also followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The mean free sorption energy of the nitrophenols onto the PUF was found equal to 7.5±0.4 kJ/mol, which reflects physical sorption. Thus, a dual-mode involves both absorption related to solvent extraction and an added component for surface adsorption seems a more likely sorption mechanism model. While a dual-mode sorption model explains the observed retention behavior, the data suggest that, solvent extraction plays a much larger role than the added component for surface adsorption. The sorption and recovery percentages of the nitrophenols from fresh, natural and industrial wastewater by the proposed unloaded foam columns were quantitatively achieved. The height equivalent to theoretical plates (HETP), N, the breakthrough capacity and the critical capacity for the unloaded foam columns were found in the range of (0.8-1.1)±0.6 mm, (94-132)±3, 3.2-4.02 and 1.5-2.67 mg/g, respectively. The method was successfully applied for the retention and recovery of the tested nitrophenols spiked to fresh and industrial wastewaters.     

Super-hydrophobic carrageenan cross-linked graphene sponge for recovery of oil and organic solvent from their water mixtures

A novel ultra-light, superhydrophobic graphene based carrageenan sponge (GCS) absorbent was synthesized by one pot hydrothermal method, for the use of selective adsorption of oils and organic solvents from their water mixtures. The GO nanosheets were reacted in the presence of formaldehyde by the insertion of carrageenan, forming hydrophobic cross-linked structure in between them. The structure and properties of this GCS are well characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Thermal gravimetric analysis, Scanning electron microscopy, and Water contact angle. The as-prepared GCS has good thermal stability (400 °C), low density (20 mg/cm⁻³), excellent hydrophobicity (water contact angle of 136.24°), and selective absorption capacity (25.2–35.95 g/g) of oils and organic solvents from their water mixtures. GCS has excellent oil sorption capacity in the range of 25.2–50 g of oil per gram of adsorbent. GCS could be easily reused by simple solvent treatment. Therefore, the adsorption capacity still retained even after 10 cycles. The present work suggests that GCS using biobased resources has high potentials for many widespread applications in industry to control environmental pollution.     

Surfacial,liquid sorption and monolayer-forming properties of hydrophilic and hydrophobic Stöber silica particles

The surface of silica spheres with a diameter of 500 nm was modified with ethoxysilane. Hydrophilic and partially hydrophobic silica spheres were obtained, suitable for the preparation of two-dimensional monoparticle films at the liquid-air interface. The tendency of these particles to self-assemble is basically dependent on surface hydrophobicity. Liquid sorption excess isotherms were studied in ethanol-cyclohexane and ethanol-chloroform mixtures with the aim of characterizing the adsorption capacity of the particles. Specific surface area and porosity were measured by nitrogen adsorption. The specific surface area determined by liquid sorption was considerably larger than determined by gas adsorption. This is ascribed to penetration of ethanol into the pores and the swelling of the silica particles in ethanol. Surface modification of hydrophilic particles changed the film-forming properties of the particles. The compressibility and the lift-off area of the monolayer films of hydrophobic particles on water were higher than for the films of hydrophilic particles.     

Use of open-cell resilient polyurethane foam loaded with crown ether for the preconcentration of uranium from aqueous solutions

The preconcentration of uranium from aqueous solutions on open-cell resilient polyurethane foams (PUF) impregnated with crown ether as an organic extractant in different conditions was investigated. The data showed that 50 minutes is a sufficient time to attain equilibrium with a maximum extraction percentage for uranium ion on polyurethane foams loaded with crown ether. Also the extraction percentage of uranium is increased markedly with increasing the pH values up to pH ~ 6 and displayed the lowest extraction at 8>pH>6. The different isotherms of uranium sorption have shown that the sorption followed a Freundlich isotherm. Column studies have been carried out in order to extend these studies to the plant scale. From the data of column sorption and breakthrough curves, the height equivalent of theoretical plates (HETP), and breakthrough capacity which affect the efficiency of the column have been calculated and found to be 1.03 mm/plate, 64±5 and 58.3 mg uranium/gram polyurethane foam impregnated with crown ether, respectively.     

Extraction of azo dyes by polyurethane foam

The extraction of 12 closely related mono-azo dyes by polyester and polyether-type polyurethane foams was studied to gain more information regarding the mechanism of the extraction of organic compounds. The effects on extraction of solution pH, dye concentration and salt concentration were investigated. It was found that the extraction of the dyes involved a neutral zwitterionic species and is highly dependent on the parameters studied. The dependency of the extraction on these parameters can be explained in a manner consistent with solvent extraction; however, the dual-mode sorption mechanism seems a more likely model. This mechanism involves both absorption related to solvent extraction, and an added component for surface adsorption. While the dual-mode sorption model explains the observed extraction behaviour, the data suggest that surface adsorption plays a much larger role than previously considered.     

Removal of Oil Spills from Salty Waters by Commercial Organoclays

In this study two commercial organoclays, Cloisite 15A and Cloisite 30B, were used to investigate their potential for removing of light and heavy crude oils from salty waters. The results of batch kinetic studies indicated that the equilibrium time can be reached within 25–30 minutes of contact time. In addition experiments were performed to determine the effect of salinity, temperature, pH and mixing time on the adsorption process. The adsorption isotherms were obtained for the crude oils at equilibrium, at an optimum pH value of 11.73 and temperature of 19°C for which the initial oil contents varied in the range of 100 to 2000 ppm. Experimental results showed that oil sorption onto these organoclays can be described by Freundlich isotherm. Further, it was found that the oil removal efficiency for Cloisite 30B is higher than that of Cloisite 15A and the greater sorption was observed for Gachsaran crude oil onto the organoclays over Soroosh crude oil.     

Facile fabrication of hydrophobic octadecylamine-functionalized polyurethane foam for oil spill cleanup

To improve the hydrophobic property of polyurethane foam for oil spill cleanup, the polyurethane foam with nitrile groups is modified by grafting with oleophilic octadecylamine. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and optical contact angle measuring device are used to characterize the modified polyurethane foam. The results show that the octadecylamine has been successfully grafted onto the polyurethane foam and improved the foam hydrophobicity. The modified foam exhibits higher contact angle (146.3 ± 2.8°) compared to the unmodified foam (121.4 ± 3.2°). Moreover, the water sorption of the modified foam is 0.11g/g, which is much lower than that of the unmodified foam (0.84g/g). On the other hand, the sorption capacity of the modified foam for toluene, gasoline and diesel sorption is increased by 20?40%. Therefore, the polyurethane foam prepared by us can be effectively used in oil/solvent spill cleanup.     

Ion-exchange foam chromatography: Part I. Preparation of rigid and flexible ion-exchange foams

In order to be able to apply the principles of foam chromatography to ion-exchange processes, preparative methods for open-cell ion-exchange foams, were investigated. Homogeneous ion-exchange foams were prepared by introducing ion-exchange groups on previously prepared phenol-formaldehyde, polyurethane and polyethylene foams. The maximum capacity of the produced sulfonated phenol-formaldehyde cation-exchange foams was 1.85 meq g^-1; that of the styrene-polyurethane interpolymer anion-exchange foams was 2.2 meq g^-1. Weak carboxylic ion-exchange foams were prepared by radiation grafting of polyurethane and polyethylene foams; the maximum capacity of these foams was 4.02 meq g^-1. Heterogeneous ion-exchange foams were prepared by foaming a fine powder of a commercially available cation exchanger with the precursors of open-cell polyether-type polyurethane foam. The capacity of such a foam containing 26% ion-exchange powder was 1.0 meq g^-1. The kinetics of the cation-exchange process on the heterogeneous foams was measured with ⁸⁵Sr.     

Synthesis of activated carbon foams with high specific surface area using polyurethane elastomer templates for effective removal of methylene blue

Carbon foams have gained significant attention due to their tuneable properties that enable a wide range of applications including catalysis, energy storage and wastewater treatment. Novel synthesis pathways enable novel applications via yielding complex, hierarchical material structure. In this work, activated carbon foams (ACFs) were produced from waste polyurethane elastomer templates using different synthesis pathways, including a novel one-step method. Uniquely, the produced foams exhibited complex structure and contained carbon microspheres. The ACFs were synthesized by impregnating the elastomers in an acidified sucrose solution followed by direct activation using CO₂ at 1000 ℃. Different pyrolysis and activation conditions were investigated. The ACFs were characterized by a high specific surface area (S_BET) of 2172 m²/g and an enhanced pore volume of 1.08 cm³/g. Computer tomography and morphological studies revealed an inhomogeneous porous structure and the presence of numerous carbon spheres of varying sizes embedded in the porous network of the three-dimensional carbon foam. X-ray diffraction (XRD) and Raman spectroscopy indicated that the obtained carbon foam was amorphous and of turbostratic structure. Moreover, the activation process enhanced the surface of the carbon foam, making it more hydrophilic via altering pore size distribution and introducing oxygen functional groups. In equilibrium, the adsorption of methylene blue on ACF followed the Langmuir isotherm model with a maximum adsorption capacity of 592 mg/g. Based on these results, the produced ACFs have potential applications as adsorbents, catalyst support and electrode material in energy storage systems.     

牛血清白蛋白在医用聚氨酯弹性体表面的吸附

制备了具有较好机械性能的异佛尔酮二异氰酸酯(IPDI)型聚氨酯弹性体胶片, 并进行表面肝素化处理, 得到抗凝血医用导管材料. 将聚氨酯胶片浸泡在牛血清白蛋白(BSA)水溶液中, 利用稀溶液黏度法研究了牛血清白蛋白在聚氨酯胶片表面的动态吸附情况, 并采用界面校正黏度方程计算溶液浓度变化. 研究发现, 牛血清白蛋白分子能迅速吸附到聚氨酯胶片表面, 但达到吸附平衡需要较长时间. 牛血清白蛋白在聚氨酯表面吸附后的溶液中分子构象发生变化.     

高交联双酯树脂制备、表征及性能研究

聚双甲基丙烯酸乙二醇酯(PEGDMA)大孔吸附树脂是一类含酯基的中极性吸附剂,通过调节致孔剂的种类和比例,制备了一系列均聚PEGDMA及EGDMA-DVB共聚物双酯树脂.用简易BET低温氮吸附法测定了树脂的比表面积.结果表明,甲苯作致孔剂制备的PEGDMA树脂比表面积在单体:致孔剂(体积比)为1:1~1:2时变化不大,甲苯致孔剂量增大所得树脂在各种溶剂中的溶胀率增大;EGDMA-DVB共聚物双酯树脂的比表面积随DVB量增加稍有下降.以苯酚和苹果多酚为吸附质研究了该系列树脂对极性有机分子的吸附行为与吸附机理,静态吸附等温线数据分析结果表明,制备的树脂与2种商品树脂(XAD-7和HP2MG)比较,树脂ED2-T对苹果多酚的平衡吸附量超过了商品树脂,初始浓度Co=1.1935mg/mL时,ED2-T树脂的平衡吸附量为135mg/g,XAD-7和HP2MG分别为113mg/g和120mg/g.树脂对苹果多酚的吸附等温线与Langmuir方程拟合较好,对苯酚的吸附Freundlich方程拟合得更好.     

疏水/亲水大孔聚二乙烯基苯/聚(N-2-氨基乙基丙烯酰胺)IPN树脂的合成及对水杨酸吸附性能研究

采用分步悬浮聚合法制备了聚二乙烯基苯/聚丙烯酸甲酯(PDVB/PMA)大孔互穿聚合物网络,将其中的聚丙烯酸甲酯用乙二胺氨解,合成了具有疏水/亲水性能的聚二乙烯基苯/聚(N-2-氨基乙基丙烯酰胺)(PDVB/PNAEAM)大孔互穿聚合物网络(IPN);测定了该树脂的孔结构、含水量、弱碱交换量和溶胀性能;测定了该树脂对水杨酸在不同温度下的吸附等温线,利用热力学函数关系计算出了吸附焓、自由能和熵.推测PDVB/PNAEAM IPN树脂中疏水性的PDVB一网具有疏水作用吸附能力、亲水性的PNAEAM一网具有氢键作用吸附能力.动态吸附及脱附实验表明湿态PDVB/PNAEAM IPN树脂对水溶液中水杨酸的饱和吸附量达到46.1mg/mL.树脂可以通过4%NaOH溶液再生.PDVB/PNAEAM IPN树脂在分离工业废水中水杨酸等芳香有机酸有良好的应用前景.     

An empirical relationship between distribution coefficients of phenols by polyurethane foams and their octanol-water distribution constants and pK(a) values

Sorption of phenol, 3-cresol, 2-, 3-, 4-nitrophenols, 2,4-, 2,6-dinitrophenol, 2,4,6-trinitrophenol, and 1-naphthol by polyether- and polyester-type polyurethane foams (PUF) was investigated. The effects of sorption time, pH, phenol concentration and the structure of tested phenols and PUF were studied. The mechanism of sorption of tested compounds on foams is discussed. It is shown that the hydrophobicity (logP, octanol-water distribution constant) and pK(a) values of the compounds play an important role in the sorption process. A regression equation connecting distribution coefficient of phenols by PUF with their hydrophobicity parameter and pK(a) values were derived. Good correlation between logD and values logP and pK(a) was observed.     

疏水/亲水性聚二乙烯基苯/聚丙烯酸大孔互穿聚合物网络树脂对苯胺的吸附性能

采用分步悬浮聚合法制备了聚二乙烯基苯/聚丙烯酸甲酯（PDVB/PMA）大孔互穿聚合物网络,将其中的聚丙烯酸甲酯转化为聚丙烯酸,得到具有疏水/亲水性能的聚二乙烯基苯/聚丙烯酸（PDVB/PAA）大孔互穿聚合物网络（IPN）,研究了这类疏水/亲水大孔PDVB/PAA IPN对苯胺的吸附热力学和吸附动力学,测定了该树脂的孔结构、含水量、弱酸交换量和溶胀性能;测定了该树脂对苯胺在不同温度下的吸附等温线,利用热力学函数关系计算了吸附焓、自由能和熵。 红外光谱显示,成功合成了疏水/亲水PDVB/PAA IPN,与PDVB、PDVB/PMA IPN树脂相比,其BET表面积以及孔容均减小,含水量为62.73％,弱酸交换量为1.91 mmol/g;对苯胺的吸附为放热、自发的过程;溶胀实验、静态解吸实验表明,PDVB/PAA IPN树脂中疏水性的PDVB网具有疏水作用吸附能力,亲水性的PAA网具有氢键作用吸附能力。 对苯胺的吸附在90 min时即可达到吸附平衡,树脂吸附苯胺符合一级速率方程,吸附速率主要受颗粒内扩散的控制,同时还受液膜扩散的影响,吸附动力学可采用HSDM模型描述。     

Preconcentration of Polycyclic Aromatic Hydrocarbons on Polyurethane Foams and Their Determination in Waters with the Use of Luminescence and High-Performance Liquid Chromatography

A technique was developed for the sorption preconcentration of polycyclic aromatic hydrocarbons on polyurethane foams in the batch and dynamic modes providing their simultaneous quantitative extraction. A procedure was proposed for screening waters for polycyclic aromatic hydrocarbons based on the preconcentration of these compounds with polyurethane foam, determination of their total amount by the luminescence method, desorption of adsorbed compounds with acetonitrile, and determination of individual compounds in the eluate by high-performance liquid chromatography with fluorescence detection. The procedure was tested with model and real samples of water.     

Hydrophobic,superabsorbing materials from reduced graphene oxide/MoS2 polyurethane foam as a promising sorbent for oil and organic solvents

This study illustrates the preparation of robust superhydrophobic and superoleophilic reduced graphene oxide (rGO) and MoS₂ nanoparticles incorporated polyurethane (PU) foam by in-situ polymerization via the one-shot method. Spectroscopic analyses confirmed the successful formation of nanoparticles and also the development of the hybrid PU material. The sponges were evaluated based on hydrophobicity and oil absorbance capacities and the modified foam exhibits the water contact angle of 151°. The pore size of the foam analyzed using an optical microscope and the effect on the density and porosity were also analyzed. The oil absorption capacity of the foam was studied using standard sorption testing. The oil and organic solvent selectivity and recyclability of hybrid PU foam were performed to estimate whether the foams could be recycled and reused. The modified system shows very high selectivity (83–94%). The recyclability of the foam was about 35 cycles without much reduction in its own weight and after 55 cycles more than 80% of the oil absorption capacity was conserved. The resulting hybrid PU material is highly efficient, porous, ultralight, hydrophobic and reusable sorbent material and displays great potential for versatile environmental remediation.     

Selectivity of polymer adsorbent in adsorptive separations of stevia diterpene glycosides

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