Synergistic effect of expandable graphite and melamine phosphate on flame‐retardant polystyrene

The halogen‐free flame‐retardant polystyrene (PS) composites containing expandable graphite (EG) and melamine phosphate (MP) were prepared successfully, and the thermal degradation behavior and fire performance were investigated by various measurements. The experimental results show that EG and MP have a synergistic effect on flame‐retardant PS, which can catalyze the char formation from PS. PS/MP/EG_(1:2) composite achieves limited oxygen index value of 28.0% and UL‐94V‐0 (1.6 mm) rate. The mass retention at high temperature (800 °C) under air atmosphere of PS composites have a large increase by the introduction of EG and MP. Microscale combustion calorimeter (MCC) and cone calorimetric analysis indicate that the heat release rate and total heat release of PS/MP/EG_(1:2) composite are reduced significantly, because the formed thick char layer has a notable barrier property. The study on the char residue of PS/MP/EG_(1:2) composite by X‐ray photoelectron spectroscopy (XPS) analysis confirms the formation of the stable structures containing P? O? C. Furthermore, the mechanical properties of PS composites were also investigated; compared with neat PS, the addition of flame retardants leads to the decrease of tensile strength and flexural strength, but the impact strength of PS/MP/EG_(1:2) has increased by 44.2%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45474.     

Synthesis of bifunctional polymeric adsorbent and its application in purification of stevia glycosides

Polymeric adsorbents with both functions of adsorption and decolorization were synthesized by introducing quaternary ammonium groups (e.g. –N⁺(CH₃)₃ groups) into conventional resinic adsorbent used to adsorb stevia glycosides in production. The relation between the adsorption capacity of the bifunctional adsorbents for stevia glycosides and the structure of adsorbents, and that between the decolorization efficiency and the structure were investigated. The results revealed that the adsorption capacity for stevia glycosides decreased somewhat as the increase of the content of quaternary ammonium groups in the adsorbent, while the decolorization efficiency increased. Adsorbents containing about 0.6–0.8 mmol/g of –N⁺(CH₃)₃ groups showed both high adsorption capacity and high decolorization efficiency, and showed adsorptive selectivity for the small-sized components of stevia glycosides. Mechanism of adsorption and decolorization was also studied, and revealed that adsorption of stevia glycosides was based on hydrophobic interactions, but decolorization was based on both ion exchange and hydrophobic interactions. Introduction of –N⁺(CH₃)₃ groups into polymeric adsorbent also changed the adsorption selectivity for various stevia glycosides, and thus the bifunctional adsorbent could be used to prepare stevia glycosides with high content of rebaudioside A.     

Effects of solvent adsorption on solution properties of poly(vinyl alcohol)/dimethylsulfoxide/water ternary systems

In this study, the solvent adsorption phenomena of poly(vinyl alcohol) (PVA) in cosolvent mixtures of dimethylsulfoxide (DMSO; solvent 1) and water (solvent 2) were investigated. Typically, this cosolvent mixture could form hydrogen‐bonded DMSO/(water)₂ complexes, involving one DMSO and two water molecules. Because of the complex formation in the cosolvent mixtures, PVA chains preferentially adsorb water molecules at DMSO mole fraction X₁ < 0.33, but preferentially adsorb DMSO molecules at X₁ > 0.33. The preferential adsorption of DMSO (a good solvent for PVA) could cause the relatively extended conformation of PVA chains in solutions because of the increase in excluded volume effect. Because of various interactions between PVA chains and cosolvent mixtures, the aggregation and gelation behaviors of PVA solutions were significantly affected by the composition of cosolvent mixture. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3211–3217, 2004     

Synthesis of PS‐g‐POSS hybrid graft copolymer by click coupling via ”graft onto” strategy

Polystyrene (PS)‐incorporated polyhedral oligomeric silsesquioxanes (POSS) organic–inorganic hybrid graft copolymer could be achieved by click coupling reaction between alkyne groups in POSS and azido groups in PS via “graft onto” strategy. Alkyne‐functionalized POSS was synthesized via thiol‐ene facile click reaction and subsequent amidation reaction with very high yield. Azido‐multifunctionalized PS could be synthesized by chloromethylation and subsequent azido reaction. The chemical structures of PS‐(CH₂Cl)_m, PS‐(CH₂N₃)_m, and PS‐g‐POSS were determined by Fourier transform infrared and ¹H NMR characterization. PS‐g‐POSS presented a better hydrophobic property with contact angle of 113° than that of PS (85°). And PS‐g‐POSS with ≤5% of grafting degree had lower glass transition temperature (T_g) than that of PS and then it increased up to 112°C with grafting degree. An obvious aggregation of POSS phase with 10–80 nm in size was formed in PS‐g‐POSS matrix. In addition, 5 wt % of PS‐g‐POSS was added to general purpose polystyrene (GPPS) to remarkably improve its tensile strength from 45 to 57 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

In situ studies of bovine serum albumin adsorption onto functionalized polystyrene latices monitored with a quartz crystal microbalance technique

The adsorbability of bovine serum albumin (BSA) onto poly(styrene‐co‐itaconic acid) (PS–IA), poly(styrene‐co‐hydroxyethyl methacrylate) (PS–HEMA), poly(styrene‐co‐acrylic acid) (PS–AA), and poly(styrene‐co‐methacrylic acid) (PS–MAA) latices were investigated with a quartz crystal microbalance. The amount adsorbed onto the functionalized latices, except for PS–MAA, was greater than that adsorbed onto polystyrene (PS) latex. To explain this result, two kinds of interaction forces were considered, hydrogen bonding and hydrophobic interactions, whereas electrostatic interaction was assumed to be small. When comparing the two extremes of hydrophobic interaction and hydrogen bonding, the latter was stronger. The corrected adsorption mass suggested that the BSA molecules were adsorbed onto the PS–MAA latex in a side‐on mode. However, in the case of the PS, PS–IA, PS–HEMA, and PS–AA latices, the BSA molecules were probably adsorbed in multiple layers. The presence of the BSA in the latex particle surface was verified by attenuated total reflectance/Fourier transform infrared spectroscopy and atomic force microscopy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42055.     

Influence of isomer ratio and ring substituents in decomposition activation energies of α,α,α′,α′‐tetrasubstituted dibenzyls

Diethyl‐2,3‐dicyano‐2,3‐di‐(X‐substituted phenyl) succinates (X = p‐OCH₃, p‐CH₃, p‐Cl, H, p‐NO₂) can initiate the free‐radical polymerization of styrene. The decomposition rate constant and activation energy were measured by means of a dilatometer, and the results showed that they were strongly dependent on the ratio of meso‐ and dl‐isomers in the polysubstituted dibenzyl compounds and the properties of the ring substituents. On the other hand, it was found that the polystyrenes, which were obtained by initiation with hydrogen, had a much larger average molecular weight than that with p‐OCH₃ and p‐CH₃. The experimental phenomena were correlated with the structure of the radical resulting from hydrogen. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2964–2971, 2001     

Insights into Removal of Phenol from Aqueous Solutions by Low Cost Adsorbents: Clays Versus Algae

Abstract

Exchanged clays and cross-linked algae were compared based on their properties for the removal of phenol from aqueous solutions. Algae Lessonia nigrescens Bory (A1) and Macrocystis integrifolia Bory (A2) were cross-linked with CaCl₂ to enhance their physical and mechanical properties. The natural clays were chemically-exchanged with salts of tetramethyl ammonium (B1), hexadecyltrimethyl ammonium (B2), and bencyltriethyl ammonium (B3) ions to increase their affinity towards organic substrates. The effects of pH and adsorbent dose were evaluated. pH exhibited a strong effect mainly on the phenol aqueous chemistry. Sorption isotherm results were modelled on the Langmuir and Freundlich equations and complemented with EDX analysis, indicating that adsorption of phenol from water was mostly driven by hydrophobic forces, with the exchanged bentonites being the adsorbents that reported the maximum adsorption capacities. Conversely, a polar surface adsorption is suggested for algae mostly by means of hydrogen bonding formation. These results provide further insight into the adsorption mechanism of phenol and analogues and their use as powerful and cheap adsorbent for the treatment of phenol-containing real wastewater.     

Adsorption of Nonpolar Solutes onto Neutral Polymeric Sorbents

Abstract

Model nonpolar solutes were chosen to examine adsorption onto neutral polymeric sorbents. When n-hexane was used as the solvent hydrogen bonding appeared to play a predominant role in adsorption. Hydrogen bonds were presumably established between the carboxylic ester groups of the sorbent and either the -OH or -NH groups of the solutes. These results suggest that the specificity of hydrogen bonding can be exploited to selectively adsorb solutes from nonpolar solvents. When water was used as the solvent, adsorption increased with decreasing solute polarity; while hydrogen bonding between the solute and sorbent appeared to be less important. These results suggest that hydrophobic interactions play a major role in adsorption from aqueaous solutions, and thus the selectivity of adsorption may be limited by the nonspecific nature of hydrophobic interactions.     

Organic–inorganic composite materials from acrylonitrile–butadiene–styrene copolymers (ABS) and silica through an in situ sol‐gel process

Nonbonded and chemically bonded organic–inorganic composite materials, ABS/SiO₂ and ABS Si(OCH₃)₃/SiO₂, were prepared by the sol‐gel processing of tetraethoxysilane (TEOS) in the presence of ABS and trimethoxysilyl functionalized ABS, ABS Si(OCH₃)₃, under the catalization of NH₄F. The ABS Si(OCH₃)₃ was obtained by oxidizing the cyano group in ABS with hydrogen peroxide, then subsequently underwent ring‐opening reaction with 3‐glycidoxypropyltrimethoxysilane (GPTS). The ABS Si(OCH₃)₃/TEOS sol‐gel liquid solution system, in which the ABS chains formed the covalent bonds with silica network and helped fix the polymer chains in the silica network, had a shorter gelation time than that of the ABS/TEOS system, which linked ABS chains to the silica network only by hydrogen bonding the cyano groups in ABS to the silanol groups. The morphology and properties of composite were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), tensile tests, and thermogravimetry. It was found that the composite prepared from ABS Si(OCH₃)₃ had higher tensile strength, glass transition point (T_g), thermal stability, and more homogeneous morphology because of the existence of the covalent bond between ABS chains and silica network that increased the compatibility between the organic and inorganic phases. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 275–283, 2000     

Adsorption of copper and lead species at electrochemically activated glassy carbon electrodes

The adsorption behaviors of Cu²⁺ and Pb²⁺ species at electrochemically activated glassy carbon obtained by different activation methods have been studied. Micropore structures were developed by cyclic polarization while small void space located at the bottom of the large void space was resulted from potentiostatic activation. The adsorption of the adsorbents would depend on the relative sizes of both the adsorbents and the void space created by electrochemical pretreatment. Different quinone derivatives would adsorb to different adsorption sites at the activated electrode, and consequently, affected the uptake of metal ions at the activated electrode incorporated with different quinone derivatives. Electrostatic and hydrophobic interactions between the adsorbents and the graphite oxide film might be involved.     

Adsorption of Pb2+ on Chitosan Cross‐Linked with Triethylene‐Tetramine

A novel triethylene‐tetramine cross‐linked chitosan (CCTS) was synthesized via the cross‐linking of triethylene‐tetramine and epichlorohydrin activated chitosan. Its structure was characterized by elemental analysis, infrared spectroscopy and X‐ray diffraction analysis, and the surface topography was determined with ESEM. The results were in agreement with expectations. The capacity of CCTS to adsorb Pb²⁺ ions from aqueous solutions was examined, and equilibrium and kinetic investigations were undertaken. The adsorption isotherms were fitted well by the Langmuir equation (R > 0.999). The maximum adsorbed amount, at pH 5.5, with an initial concentration of 3 mmol/L (621 ppm), was 378.8 mg/g. The adsorption process could be best described by a second‐order equation (R = 1). This suggests that the rate‐limiting step may be the chemical adsorption (chemisorption) step and not the mass transport. The separation factor used was 0 < R_L < 1. Therefore, it can be concluded that CCTS is an effective adsorbent for the collection of Pb²⁺.     

Application of magnetite modified with aluminum/silica to adsorb phosphate in aqueous solution

BACKGROUND: Phosphate is one of the main contaminants responsible for the eutrophication of surface waters, and adsorption is a potential treatment method for this pollutant. A magnetic adsorbent manufactured from magnetite (Fe₃O₄) can be recovered easily from treated water by magnetic force, without requiring further downstream treatment. In this research, the surface of magnetite modified with aluminum and silica (Al/SiO₂/Fe₃O₄) was used to adsorb phosphate in an aqueous solution in a batch system. RESULTS: The optimum solution pH for phosphate adsorption by Al/SiO₂/Fe₃O₄ was found to be 4.5. The phosphate adsorption behavior of Al/SiO₂/Fe₃O₄ was in good agreement with both the Langmuir and Freundlich adsorption isotherm, and the maximum adsorption capacity (q_m) and Gibbs free energy of phosphate was 25.64 mg g^?1 and ? 21.47 kJ mol^?1, respectively. A pseudo‐second‐order model could best describe the adsorption kinetics, and the derived activation energy was 3.52 kJ mol^?1. The optimum condition to desorb phosphate from Al/SiO₂/Fe₃O₄ is provided by a solution with 0.05 mol L^?1 NaOH. CONCLUSIONS: Magnetic adsorbent is a potential material for a water treatment method. The results of this study will be helpful in the development of aluminum modified silica magnetic adsorbents that can be used to remove phosphate in aqueous solution. Copyright © 2011 Society of Chemical Industry     

A pseudo first order rate model for the adsorption of an organic adsorbate in aqueous solution

Five low rank, coal‐based adsorbents, i.e. coal, grus, two chars, and an activated carbon were used to adsorb a low molecular weight organic compound from aqueous solution. The rates of adsorption were found to conform to pseudo first order kinetics with good correlation (r² greater than 0.996). This kinetic model was used to calculate pseudo first order rate constants (k₁^′ min ⁻¹) and relative rate constants (rate constant/unit mass of adsorbent, k₁^″ min⁻¹ g⁻¹) for the adsorption process. Rate properties have been explained in terms of both a diffusion and chemically controlled rate determining step. Rate constants for the five adsorbents vary as expected on the basis of their physical properties, that is slowest for grus (compressed coal) and fastest for the activated carbon. © 1999 Society of Chemical Industry     

Silica gel‐based adsorbents prepared via homogeneous and heterogeneous routes: adsorption properties and recycling as heterogeneous catalysts

Silica gel‐based adsorbents were prepared via homogeneous and heterogeneous routes using two silane coupling reagents, 3‐glycidoxypropyltrimethoxysilane and γ ‐chloropropyltrimethoxysilane. Characterization results showed that amino contents of the adsorbents prepared via the homogeneous route were higher than those of the adsorbents prepared via the heterogeneous route for both silane coupling reagents. The adsorption capabilities of the resulting four types of adsorbents for Hg(II), Cu(II), Au(III), Ni(II), Pb(II) and Ag(I) ions were compared. Good adsorption capability for Au(III) was observed for the new adsorbents and the maximum static saturated adsorption capacities for Au(III) could reach 0.67 mmol g^?1. Due to the formation of Au(0) particles in the adsorption process, which hampered the reusability of the spent adsorbents, alternative recycling of the spent adsorbents after Au(III) adsorption was sought. The spent adsorbents were treated with NaBH₄ and used as catalysts in the reduction of 4‐nitrophenol to 4‐aminophenol. After three catalytic cycles at 298 K, the k values indicated minimal decrease of catalytic activity. © 2017 Society of Chemical Industry     

Self-assembly of an organometallic silver(I) 1D architecture supported by three different types of bonding interactions

The new ligand o-C₆H₄[CH₂OCH₂C(3-Phpz)₃]₂ (pz=pyrazolyl ring) reacts with AgBF₄ to yield the coordination polymer {o-C₆H₄[CH₂OCH₂C(3-Phpz)₃]₂Ag₂(BF₄)₂}_n. The organometallic supramolecular architecture contains two different types of silver(I) cations arranged in bimetallic units forming a 1D coordination polymer. The bimetallic units show three different types of bridging interactions, including a μ-κ¹,κ²-tris(3-Ph-pyrazolyl)methane unit, a silver η²-bonded to a phenyl group and π–π stacking interactions.     

Macroporous crosslinked hydrophobic/hydrophilic polystyrene/polyamide interpenetrating polymer network: Synthesis,characterization, and adsorption behaviors for quercetin from aqueous solution

In the present study, a novel hydrophobic/hydrophilic polystyrene/polyamide interpenetrating polymer network (PS/PAM IPN) was synthesized and its molecular structure was characterized by Fourier transform infrared ray (FT‐IR) spectrum, chemical analysis, swelling test, and N₂ adsorption‐desorption experiment. The obtained PS/PAM IPN was employed as a polymeric adsorbent to adsorb quercetin from aqueous solution, and the adsorption thermodynamics were calculated according to thermodynamic equations. It was found that no chemical bond was formed between PS and PAM and PS/PAM IPN held characters of amphiphilic polymer network (APN). The adsorption isotherms could be well fitted by Freundlich isotherm, and the adsorption was shown to be an exothermic, spontaneous, and more ordered process. The total adsorption capacity from the column adsorption experiment was measured to be 8.6 mg/mL wet resin, and the adsorbed quercetin on PS/PAM IPN could be easily desorbed by 10% of hydrochloric acid‐ethanol. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

CO2 sorption performance by aminosilane functionalized spheres prepared via co‐condensation and post‐synthesis methods

Amine functionalized silica microspheres were synthesised via a modified Stöber reaction for carbon dioxide (CO₂) adsorption. A number of adsorbents were synthesized by co‐condensation and post synthesis immobilization of amines on porous silica spheres. CO₂ adsorption studies were carried out on a fixed bed gas adsorption rig with online mass spectrometry. Amine co‐condensed silica spheres were found to adsorb up to 66 mg CO₂ g^?1 solid in a 0.15 atm CO₂ stream at 35°C. Simple post‐synthesis addition of aminopropyltriethoxysilane to amine co‐condensed silica was found to significantly increase the uptake of CO₂ to 211 mg CO₂ g^?1 under similar conditions, with CO₂ desorption commencing at temperatures as low as 60°C. The optimum temperature for adsorption was found to be 35°C. This work presents a CO₂ adsorbent prepared via a simple synthesis method, with a high CO₂ adsorption capacity and favorable CO₂ adsorption/desorption performance under simulated flue gas conditions. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2825–2832, 2016     

Syntheses and adsorption properties for Hg2+ of chelating resin of crosslinked polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole

A novel chelating resin with functional group containing S and N atoms was prepared using chloromethylated polystyrene and 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT) as materials. Its structure was characterized by infrared spectra and elementary analysis. The results showed that the content of the functional group was 2.07 mmol BMT g^?1 resin, 47% of which were in the form of monosubstitution (PS‐BMT‐1) and 53% in the form of double substitution (PS‐BMT‐2). The adsorption for mercury ion was investigated. The adsorption dynamics showed that the adsorption was controlled by liquid film diffusion. Increasing the temperature was beneficial to adsorption. The Langmuir model was much better than the Freundlich model to describe the isothermal process. The adsorption activation energy (E_a), ΔG, ΔH, and ΔS values calculated were 18.56 kJ·mol^?1, ‐5.99 kJ·mol^?1, 16.38 kJ·mol^?1, and 37.36, J·mol^?1·K^?1, respectively. The chelating resin could be easily regenerated by 2% thiourea in 0.1 mol·L^?1 HCl with higher effectiveness. Five adsorption–desorption cycles demonstrated that this resin was suitable for repeated use without considerable change in adsorption capacity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1646–1652, 2004     

Removal of nitro aromatic compounds and sulfite acid from distillate of 2,4,6‐trinitrotoluene red water using modified porous polystyrene microspheres

To remove the nitro aromatic compounds (NACs) and SO₃^2? from distillate of 2,4,6‐trinitrotoluene (TNT) red water, the carboxylated and aminated polystyrene (PSt) microspheres were used as adsorbents. GC‐MS and HPLC analysis were used to determine the types and concentrations of NACs before and after adsorption. The carboxylated PSt, which was prepared by modifying PSt with phthlandione (PA), could remove the neutral NACs including 2,6‐dinitrotoluene (2,6‐DNT), 2,4‐dinitrotoluene (2,4‐DNT), 1,3,5‐trinitrobenzene (1,3,5‐TNB), and 2,4,6‐trinitrotoluene (2,4,6‐TNT), with the acid 2,4‐dinitrophenol (2,4‐DNP) and SO₃^2? remained in the distillate. The aminated PSt that was synthesized by activating PSt with chloroacetyl chloride follow by reaction with 1,2‐ethanediamine (EDA) could remove all the NACs and SO₃^2?. The results suggested that EDA‐PSt adsorbed the NACs though multimode interactions, i.e., hydrogen bond and electrostatic attraction. After adsorption using EDA‐PSt, chemical oxygen demand (COD) was reduced from 86.1 to 11.2 mg L^?1, and a colorless, transparent, and nontoxic solution with neutral pH value was obtained. Five grams of EDA‐PSt could purify 1600 cm³ of distillate of TNT red water, and the adsorbents could be recycled by elution with methanol to desorb the neutral NACs followed by elution with 0.1 mol L^?1 NaOH to wash off 2,4‐DNP and SO₃^2?. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Syntheses and characterization of polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole and its sorption behavior for Pd(II), Pt(IV), and Au(III)

A type of chelating resin crosslinking polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT), containing sulfur and nitrogen atoms, was prepared. The structure of PS‐BMT was confirmed by FTIR, elemental analysis, and X‐ray photoelectron spectroscopy (XPS). Adsorption of Pd(II), Pt(IV), and Au(III) was investigated. The capacity of PS‐BMT to adsorb Pd(II) and Pt(IV) was 0.190 and 0.033 mmol/g, respectively. The adsorption dynamics of Pd(II) showed that adsorption was controlled by liquid film diffusion and that the apparent activation energy, E_a, was 32.67 kJ/mol. The Langmuir model was better than the Freundlich model in describing the isothermal process of Pd(II), and the ΔG, ΔH, and ΔS values calculated were ?0.33 kJ/mol, 26.29 kJ/mol, and 87.95 J mol^?1 K^?1, respectively. The mechanisms of adsorption of Pd(II), Pt(IV), and Au(III) were confirmed by XPS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 631–637, 2006