Novel carrageenan-based hydrogel nanocomposites containing laponite RD and their application to remove cationic dye

Novel hydrogel nanocomposites were synthesized by solution polymerization of acrylamide in the presence of carrageenan biopolymer and laponite RD clay. Laponite was used as an inorganic cross-linker. Ammonium persulfate was applied as an initiator. The structure and morphology of the nanocomposites were investigated using XRD, scanning electron microscopy, and transition electron microscopy techniques. The influence of both laponite nanoclay and the carrageenan content on the swelling degree of nanocomposites was studied and it was found that all nanocomposites containing carrageenan component have a high swelling degree compared to a nanocomposite without carrageenan. The obtained nanocomposites were examined to remove a cationic crystal violet (CV) dye from water. The effect of carrageenan and clay contents on the speed of dye adsorption revealed that while the rate of dye adsorption is enhanced by increasing the clay content, it was depressed as the carrageenan content increased in nanocomposite composition. The results showed that the pseudo-second-order adsorption kinetic was predominant in adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results indicated that the experimental data fit the Langmuir isotherm best. Maximum adsorption capacity was obtained for carrageenan-free nanocomposite with 79.8?mg?g^?1 of adsorbed CV onto nanocomposite.     

Effect of sodium montmorillonite nanoclay on the water absorbency and cationic dye removal of carrageenan-based nanocomposite superabsorbents

Nanocomposite superabsorbents were synthesized by simultaneously solution copolymerization of acrylamide (AAm) and sodium acrylate (Na-AA) in the presence of carrageenan biopolymer and sodium montmorillonite (Na-MMt) nanoclay. Potassium persulfate (KPS) and methylenebisacrylamide (MBA) were used as initiator and crosslinker, respectively. The structure and morphology of the nanocomposites were investigated using XRD, FTIR, scanning electron microscopy (SEM), and TEM techniques. The influence of nanoclay and carrageenan contents as well as monomer weight ratios on the degree of swelling of nanocomposites was studied. The optimum water absorbency was obtained at 10 wt% of clay, 10 wt% of carrageenan, and 1:1 of monomers weight ratio. The obtained nanocomposites were examined to remove of crystal violet (CV) cationic dye from water. The effect of carrageenan and clay content on the speed of dye adsorption revealed that while the rate of dye adsorption is enhanced by increasing the clay content up to 14 wt% of clay, it was decreased as the carrageenan increased in nanocomposite composition. The results showed that the pseudo-second-order adsorption kinetic was predominated for the adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results corroborated that the experimental data fit the Freundlich isotherm the best.     

Synthesis of kappa-carrageenan-g-poly(acrylamide)/sepiolite nanocomposite hydrogels and adsorption of cationic dye

In this study, nanocomposite hydrogels from grafting of acrylamide onto kappa-carrageenan biopolymer were prepared in the presence of sepiolite clay. Methylenebisacrylamide and ammonium persulfate were used as cross-linker and initiator, respectively. The sepiolite nanoclay was introduced into hydrogel matrix without any chemical treatment. The structure of nanocomposites was investigated by FTIR, SEM, TEM, and TGA techniques. The TEM image showed that sepiolite exists as individual needle’s shape. The swelling of hydrogels were studied in distilled water, salt solutions, and various pHs. The obtained nanocomposites were evaluated to remove of cationic crystal violet (CV) dye from water. The kinetic and isotherm of adsorption of dye onto nanocomposites were studied and analyzed according to kinetic and isotherm models. The results showed that the pseudo-second-order adsorption kinetic was predominated for the adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results corroborated that the experimental data fit the Langmuir isotherm the best. By varying the pH of initial dye solution, while the clay-free hydrogel showed relatively pH-independent adsorption behavior, the nanocomposites depicted pH-dependent adsorption.     

Preparation and characterization of poly(methyl methacrylate) nanocomposites containing octavinyl polyhedral oligomeric silsesquioxane

A series of poly(methyl methacrylate) (PMMA) containing octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) nanocomposites were synthesized by solution polymerization. The products were characterized by FTIR, ¹H NMR, GPC, TEM, DSC and TGA. The actual contents of OV-POSS in the obtained products and the reaction degree of the vinyl groups in the POSS were calculated on the basis of FTIR, TGA and ¹H NMR data respectively. The DSC and TGA results indicate that the incorporation of POSS molecules could improve the thermal properties of PMMA nanocomposites significantly. The glass transition temperature (T_g) and thermal decomposition temperature (T_dec1) of the nanocomposite with 12.27 wt % of OV-POSS were increased by 23 °C and 93 °C correspondingly. In our experiment, the improved thermal properties were largely attributed to the nanoreinforcement effect of POSS cages and the formation of star-shaped structures with cubic silsesquioxane core.     

Thermodynamic and kinetic studies of crystal violet dye adsorption with poly(methyl methacrylate)–graphene oxide and poly(methyl methacrylate)–graphene oxide–zinc oxide nanocomposites

We successfully prepared poly(methyl methacrylate) (PMMA)–graphene oxide (GO) and PMMA–GO–zinc oxide (ZnO) nanocomposites and characterized them using different techniques. The adsorption performances of the as-prepared composites were investigated for crystal violet (CV) dye removal. The contact time as a main factor affecting the adsorption process by adsorbents was studied. Because the adsorption capacity value for CV was found to show no extensive changes after 35 min, 35 min was selected as the best contact time for our system. The adsorption results revealed that the best capacity of CV adsorption onto the PMMA–GO and PMMA–GO–ZnO nanocomposites occurred at pH 12 and 298 K. The respective entropies (−0.208 and −0.168 kJ mol⁻¹ K⁻¹) and enthalpies (−72.86 kJ/mol, and −55.54 kJ/mol) for PMMA–GO and PMMA–GO–ZnO and Gibbs energy revealed that the process of adsorption was exothermic. In addition, the Elovich, pseudo-first-order, intraparticle diffusion, and pseudo-second-order (four types) models were applied to our kinetic study. Our results indicate that CV adsorption onto PMMA–GO and PMMA–GO–ZnO was good with the pseudo-second-order (type 1) and pseudo-first-order models because of the low χ² value and the high correlation coefficient value. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47495.     

Organic–Inorganic Incompletely Condensed Polyhedral Oligomeric Silsesquioxane-Based Nanohybrid: Synthesis,Characterization and Dye Removal Properties

A nanocomposite was developed from organic–inorganic hybrid of incompletely condensed polyhedral oligomeric silsesquioxane nanoparticles and poly (acrylamide-co-hydroxyethyl methacrylate) with properties of hydrophobicity of incompletely condensed polyhedral oligomeric silsesquioxane and dye adsorption capacity of the copolymer. The as-prepared nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The synthesized hybrid nanocomposite acquires extraordinary water remediation property after the removal of toxic dye from aqueous solution. Conditions for the adsorption of dye by the hybrid nanocomposite have been also optimized. In addition, the adsorption mechanism was studied.     

OV-POSS改性CM胶料的硫化行为及其硫化胶的性能

将氯化聚乙烯弹性体(CM)与笼型八乙烯基倍半硅氧烷(OV-POSS)进行共混,制备POSS改性CM胶料;采用过氧化二异丙苯(DCP)为硫化剂,三烯丙基异氰脲酸酯(TAIC)为助硫化剂,利用无转子硫化仪对该改性胶料的硫化行为及硫化动力学进行研究。利用动态力学热分析仪(DMA)以及热机械分析仪(TMA)对硫化胶的力学性能、热稳定性能,及其动、静态热机械性能进行了研究。结果表明：随着OV-POSS用量的增加,改性胶料的硫化反应活化能逐步降低,硫化速度加快,硫化胶的拉伸强度、玻璃化温度(T_g)相应提高。表明OV-POSS对CM的硫化具有促进作用,加入OV-POSS,可改善其硫化胶的力学性能以及提高热稳定性能。     

Facile synthesis of TiO<Subscript>2</Subscript>/ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanocomposite by sol-gel auto combustion method for superior visible light photocatalytic efficiency

Photocatalytic composite materials having photon absorption capability in the range of visible light were synthesized by loading TiO₂ (5, 10, 15, and 20 wt%) on ferrite nanocomposites by sol-gel auto-combustion method. The synthesized nanocomposites were analyzed using X-ray diffraction, Transmission electron microscopy, diffuse reflectance spectroscopy and N₂ adsorption techniques. The generation of photo active hydroxyl radicals for all the synthesized composites was found higher under the irradiation of red LED (RLED irradiation) which was confirmed by degradation of rhodamine B dye under irradiation of RLED. Photocatalytic activity of the synthesized nanocomposites was also carried out under irradiation of ultraviolet (UVLED) and blue (BLED) light emitting diodes, which is comparatively less than for the reaction under red LED irradiation. The operational parameters like catalyst amount, pH and concentration of dye solution were studied and ESI-MS degradation pathway is proposed by analyzing the degraded samples.     

Gd(III) Adsorption on the DTPA-functionalized chitosan/magnetite nanocomposites

The method for chitosan (CS) covalent immobilization onto NH₂-functionalized magnetite nanoparticles surface is presented. Covalent binding of CS to the magnetite surface proceeds using a free -CH₂OH group of CS and a NH₂-group of magnetite with epichlorohydrin (ECH) as a cross-linker. The obtained nanocomposites were functionalized by diethylenetriaminepentaacetic acid (DTPA)-groups. Composites were characterized by elemental analysis, FTIR, XPS and ASAP methods. The total content of organic phase (CS-DTPA) in the hybrid material, appreciated by thermogravimetric analysis (TGA), was 3.7%. Considering the atomic ratio between oxygen in CS and oxygen in ECH residue, the chemical structure of the hybrid material is proposed. The adsorption of Gd-DTPA and Gd³⁺ on the obtained nanocomposite was studied. The Freundlich isotherm fits all the experimental data better than the Langmuir adsorption.     

Water‐soluble chitosan intercalated montmorillonite nanocomposites for removal of basic blue 66 and basic yellow 1 from aqueous solution

Water‐soluble chitosan intercalated montmorillonite (wCTS/MMT) nanocomposites were modified and characterized by using Fourier transform infrared, thermogravimetric analysis, and X‐ray diffractometer techniques. Two types of wCTS, namely, low molecular‐weight chitosan (L‐wCTS) and hydroxyethylacryl chitosan (H‐wCTS) were synthesized and applied. The batch adsorption experiments on these nanocomposites were conducted by using basic dyes, that is, Basic Blue 66 and Basic Yellow 1 (BY1). The adsorption capacities of sodium montmorillonite (Na‐MMT), chitosan, L‐wCTS/MMT, and H‐wCTS/MMT were measured and compared. The results showed that the adsorption capacities of wCTS/MMT nanocomposites were higher than those values of Na‐MMT and chitosan. The adsorption kinetics of wCTS/MMT nanocomposites for BY1 were studied. It was described that the adsorption processes were better fitted by pseudo‐second‐order equation. The Langmuir and the Freundlich models were used to fit the adsorption isotherm. It was indicated that the adsorption isotherms followed the Langmuir model. The values of the maximum adsorption capacity of L‐wCTS/MMT and H‐wCTS/MMT adsorbents were at 188.7 and 294.1 mg/g, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Construction of hybrid nanocomposites containing Pt nanoparticles and poly(3-methylthiophene) nanorods at a glassy carbon electrode: Characterization, electrochemistry, and electrocatalysis

Hybrid nanocomposites containing Pt nanoparticles (nano-Pt) and poly(3-methylthiophene) (P3MT) nanorods at glassy carbon surfaces have been successfully prepared by use of an in situ cyclic voltammetry (CV) method. Field emission scanning electron microscope (FE-SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltagrams were used to characterize the properties of these nanocomposites. SEM images showed that nano-Pt were located on the surface of P3MT nanorods and that they formed a three-dimensional (3D) porous nanostructure. EIS and CV results demonstrated that these hybrid nanocomposites had good conductivities, and could accelerate the electron-transfer rates of redox ions. From the results of electrochemical oxidation of methanol and nitrite, we observed that this nanocomposite-modified electrode exhibited excellent electrocatalytic activity, which might be useful in biosensors and/or fuel cells.     

Preparation and characterization of hydrophilic polydopamine-coated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/oxide graphene imprinted nanocomposites for removal of bisphenol A in waters

Bisphenol A (BPA), a known endocrine disruptor, is of global concern because it poses serious threats to the ecological environment and human health. In this work, hydrophilic polydopamine-coated Fe₃O₄/oxide graphene (IPDA@MGO) magnetic imprinted nanocomposites were prepared by the self-polymerization of dopamine on the surface of Fe₃O₄/GO in Tris-HCl buffer using BPA as a template for selective adsorption of BPA in water. IPDA@MGO showed specific recognition toward BPA with a high imprinting factor of 3.2 compared with nonimprinted polymer. The capacity of IPDA@MGO toward BPA was 41.2 mg/g and the adsorption reached equilibrium within 30 min. The adsorption agreed well with the Freundlich and pseudo-second order kinetic models. The good adsorption performance was attributed to the abundant binding sites and good dispersibility of IPDA@MGO nanocomposites derived from its excellent hydrophilicity. The nanocomposites could be removed rapidly by an external magnet and regenerated for repeated adsorption of BPA in water. The proposed method has potential applications for efficient removal of BPA in environmental waters.     

Synergistic effects of cellulose nanocrystals-organic montmorillonite as hybrid nanofillers for enhancing mechanical,crystallization, and heat-resistant properties of three-dimensional printed poly(lactic acid) nanocomposites

Cellulose nanocrystals (CNC)-organic montmorillonite (OMMT) hybrid nanofillers were prepared, and their effects in reinforcing the performance of three-dimensional (3D) printed poly(lactic acid) (PLA) nanocomposites were studied. The results indicated that the hybrid CNC-OMMT nanofillers had a synergistic impact on enhancing the mechanical properties of PLA nanocomposites compared to either single nanofillers (CNC or OMMT). The dispersion of CNC-OMMT in the PLA matrix was not only significantly improved, but also the hybrid nanofillers did not form pore defects in the nanocomposites. In terms of the crystallization performance, the multidimensional hybrid nanofillers acted as efficient heterogeneous-nucleating agents and increased the PLA crystallization rate. Additionally, the incorporation of the hybrid nanofillers improved the heat resistance of the PLA nanocomposites when the printing platform temperature was adjusted to a temperature within the crystallization temperature range of PLA. The preparation of hybrid nanofillers based on existing nanomaterials and their incorporation into polymers creates a novel route for the development of high-performance polymer nanocomposites.     

Synthesis of acrylic-lignosulfonate resin for crystal violet removal from aqueous solution

A new acrylic-lignosulfonate resin (ALR) was obtained by radical polymerization using calcium lignosulfonate (LS-Ca) and acrylic acid (AA) as raw materials. ALR was characterized using FT-IR, SEM, TG-DSC and N₂ adsorption–desorption surface area and pore size analyzer. Batch adsorption, including initial concentration, time, pH, dosage and temperature on the adsorption of crystal violet (CV) by ALR, was systematically studied. The ALR contained porous structure and the specific surface area of ALR was 190.55 m²/g with average pore diameter 11.34 nm. The kinetic and equilibrium data fitted into the pseudo-second-order model and Freundlich isotherm model, respectively. The adsorption process was slightly influenced in the range of pH=3–12. The maximum adsorption capacity of CV was found to be as high as 150.40±4.80mg/g for 24 h at 25 °C. Thermodynamic parameters were evaluated, and their values indicated that adsorption of CV on ALR was an exothermic process and spontaneous.     

Nanodiamond-containing polyethyleneimine hybrid materials for lead adsorption from aqueous media

This study describes the preparation of new surface-modified nanodiamond (ND) particles containing urethane-based hybrid materials by photopolymerization of aliphatic urethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate monomers, and their usage for lead adsorption from aqueous media. ND and synthesized surface-modified ND were characterized by atom transfer radical addition Fourier transform infrared spectroscopy (ATR-FTIR) and scanning transmission electron microscopy analysis. Crosslinked adsorbent nanocomposites were then treated with polyethylene imine and all adsorbent nanocomposites were characterized by ATR-FTIR, scanning electron microscopy, thermogravimetric analysis, and contact angle measurements. The metal ion binding capacity of the surfaces of the nanocomposites containing high amine content was investigated. The effects of the percentage of functional monomer, pH, and contact time on adsorption, and the interaction of foreign metal ions have been tested. Optimum contact time was found to be 7 h at pH 5. The adsorption capacity of the synthesized nanocomposite adsorbent for lead (II) was determined as 17.12 mg g⁻¹. Langmuir and Freundlich isotherms were used to determine the adsorption behaviors and Langmuir isotherm model was found to be the most suitable model (R²: 0.9988). The amount of adsorption of Pb (II) ions of UV curable adsorbent film prepared in river water samples was investigated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48241.     

Biodegradable polyester layered silicate nanocomposites based on poly(ϵ‐caprolactone)

Nanocomposites based on biodegradable poly(?‐caprolactone) (PCL) and layered silicates (montmorillonite, MMT) were prepared either by melt interaction with PCL or by in situ ring‐opening polymerization of ?‐caprolactone as promoted by the so‐called coordination‐insertion mechanism. Both non‐modified clays (Na⁺ ‐MMT) and silicates modified by various alkylammonium cations were studied. Mechanical and thermal properties were examined by tensile testing and thermogravimetric analysis. Even at a filler content as low as 3 wt% of inorganic layered silicate, the PCL‐layered silicate nanocomposites exhibited improved mechanical properties (higher Young's modulus) and increased thermal stability as well as enhanced flame retardant characteristics as a result of a charring effect. It was shown that the formation of PCL‐based nanocomposites depended not only on the nature of the ammonium cation and related functionality but also on the selected synthetic route, melt intercalation vs. in situ intercalative polymerization. Interestingly enough, when the intercalative polymerization of ?‐caprolactone was carried out in the presence of MMT organo‐modified with ammonium cations bearing hydroxyl functions, nanocomposites with much improved mechanical properties were recovered. Those hybrid polyester layered silicate nanocomposites were characterized by a covalent bonding between the polyester chains and the clay organo‐surface as a result of the polymerization mechanism, which was actually initiated from the surface hydroxyl functions adequately activated by selected tin (II) or tin (IV) catalysts.     

INHIBITING EFFECT OF CRYSTAL VIOLET DYE ON ALUMINUM CORROSION IN ACIDIC AND ALKALINE MEDIA

Crystal violet dye (CV) was studied as a corrosion inhibitor for aluminum in hydrochloric acid (1 mol dm^?3) and potassium hydroxide (0.5 mol dm^?3) solutions in the temperature range 30°–60°C using the gravimetric technique. The effect of iodide ions on the inhibiting efficacy of CV was also assessed. CV was found to inhibit Al corrosion in both aggressive media, exhibiting greater inhibition efficiency in 1 M HCl (83.6%) than in 0.5 M KOH (23.0%). Inhibition efficiency in 0.5 M KOH was, however, synergistically increased in the presence of iodide ions to attain values up to 85.3%. Inhibition efficiency in the acidic and alkaline solutions increased with CV concentration but decreased with rise in temperature, suggesting physical adsorption of CV on the Al surface. The calculated values of activation energy (E_a), free energy of adsorption (ΔG_ads), and heat of adsorption (Q_ads) confirm the physisorption mechanism. The inhibitor adsorption characteristics were approximated by the Freundlich adsorption isotherm.     

Unsaturated polyester–poly(ε‐caprolactone) hybrid nanocomposites: Thermal–mechanical properties

This paper reports on the thermal behavior and mechanical properties of nanocomposites based on unsaturated polyester resin (UP) modified with poly(ɛ‐caprolactone) (PCL) and reinforced with an organically modified clay (cloisite 30B). To optimize the dispersion of 30B and the mixing of PCL in the UP resin, two different methods were employed to prepare crosslinked UP–PCL‐30B hybrid nanocomposites. Besides, two samples of poly(ɛ‐caprolactone) of different molecular weight (PCL2: M_n = 2.10³g.mol⁻¹ and PCL50: M_n = 5.10⁴g.mol⁻¹) were used at several concentrations (4, 6, 10 wt%). The 30B concentration was 4 wt% in all the nanocomposites. The morphology of the samples was studied by scanning electron microscopy (SEM). The analysis of X‐ray patterns reveals that intercalated structures have been found for all ternary nanocomposites, independently of the molecular weight, PCL concentration and the preparation method selected. A slight rise of the glass transition temperature, T_g, is observed in UP/PCL/4%30B ternary nanocomposites regarding to neat UP. The analysis of the tensile properties of the ternary (hybrid) systems indicates that UP/4%PCL2/4%30B nanocomposite improves the tensile strength and elongation at break respect to the neat UP while the Young modulus remains constant. POLYM. COMPOS., 35:827–838, 2014. © 2013 Society of Plastics Engineers     

Adsorption behavior of crystal violet from aqueous solutions with chitosan–graphite oxide modified polyurethane as an adsorbent

A series of chitosan (Ch)–graphite oxide (GO)‐modified polyurethane foam (PUF) materials as adsorbents were synthesized by a foaming technique. The adsorbent was characterized through IR spectroscopy, scanning electron microscopy, and thermogravimetric analysis (TGA). Batch adsorption experiments of the cationic dye crystal violet (CV) were carried out as a function of the Ch–GO content (1.0–8.0 wt %), solution pH (2–10), dye concentration (100–300 mg/L), adsorbent dosage (10–60 mg/mL), and temperature (20–45°C). At a lower pH value, the surface of Ch–GO/PUF acquired positive charge by absorbing H⁺ ions; this resulted in a decreasing adsorption of the cationic CV dye because of electrostatic repulsion. As the pH of the aqueous system increased, the numbers of negatively charged sites increased by absorbing OH⁻ ions, and a significantly high electrostatic attraction existed between the negatively charged surface of Ch–GO/PUF and the cationic dye (CV) molecules. This led to maximum dye adsorption. The kinetics, thermodynamics, and equilibrium of CV adsorption onto Ch–GO/PUF were investigated. The equilibrium data for CV adsorption fit the Langmuir equation, with a maximum adsorption capacity of 64.935 mg/g. The adsorption kinetics process followed the pseudo‐second‐order kinetics model. Thermodynamic parameters analysis revealed that the adsorption of CV from an aqueous solution by a Ch–GO modified PUF material was a spontaneous and endothermic process. We concluded that Ch–GO/PUF is a promising adsorbent for the removal of CV from aqueous solutions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41828.