Nanocomposite Beads Research Articles

Efficient removal of lead (II) ions and methylene blue from aqueous solution using chitosan/Fe-hydroxyapatite nanocomposite beads

Chitosan is a well-known sorbent and effective in the uptake of anionic or reactive dyes, but it has deficiency in adsorption of basic dyes. In this work, chitosan/Fe-substituted hydroxyapatite composite beads were prepared in a different ratio via embedding of hydroxyapatite into chitosan solution for removal of basic dye and heavy metal from aqueous solution. The composite beads were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy in order to reveal their composition and surface morphology. In this particular study, methylene blue (MB) and lead (Pb (II)) ions were selected as representatives of dye and a heavy metal, respectively. The various experimental conditions affecting dye adsorption were explored to achieve maximum adsorption capacity. Moreover, the kinetic, thermodynamic and adsorption isotherm models were employed for the description of the heavy metal and dye adsorption processes. The results indicated that the prepared hydrogel is an efficient adsorbent for the aforementioned dye and metal concomitant with the ability of regeneration without losing the original activity and stability for water treatment applications.

Magnetic/pH-sensitive κ-carrageenan/sodium alginate hydrogel nanocomposite beads: preparation, swelling behavior, and drug delivery

This work describes the preparation of magnetic and pH-sensitive beads based on κ-carrageenan and sodium alginate for use as drug-targeting carriers. Physical cross-linking using K+/Ca2+ ions was applied to obtain ionic cross-linked magnetic hydrogel beads. The produced magnetite beads were thoroughly characterized by TEM, SEM/EDS, XRD, FTIR, and VSM techniques. While the water absorbency (WA) of magnetic beads was enhanced by increasing the weight ratio of κ-carrageenan, introducing magnetic nanoparticles caused a decrease in WA capacity from 15.4 to 6.3 g/g. Investigation on the swelling of the hydrogel beads in NaCl, KCl, and CaCl2 solutions revealed the disintegration of beads depending on the composition of hydrogel beads and the type of metal cations in swelling media. The swelling ratio of beads indicated pH-dependent properties with maximum water absorbing at pH 7.4. Also, it was found that the strength of pH-sensitivity of magnetic beads was low for beads with the high content of carrageenan component. The in vitro drug release studies from hydrogels exhibited significant behaviors on the subject of physiological-simulated pH values and external magnetic fields. The maximum cumulative releases obtained were 98 and 43% at pH values 7.4 and 1.2, respectively. The Introducing magnetite nanoparticles influenced the cumulative release of drug.

Preparation of magnetic nanocomposite beads and optimizing the conditions for effective removal of U(VI) from aqueous solutions

Magnetic ion-imprinted polymers (IIPs) were prepared by precipitate polymerization and leached with HCl to remove uranium. Their ability to remove hexavalent uranium from wastewater effluents was studied. Batch adsorption studies to determine the optimum conditions of U(VI) removal were conducted at different levels of sample pH, sorbent amount, agitation time, and initial uranium concentration. It was observed that, under optimum conditions (i.e. pH 4, adsorbent amount of 50 mg, 45 min agitation time, and initial U(VI) concentration of 2 mg L−1), the maximum removal of U(VI) cations was >98% and 80% for the magnetic IIP and the corresponding magnetic non-imprinted polymers (NIP), respectively. Langmuir and Freundlich isotherms were used to describe the adsorption of U(VI) onto magnetic IIP and NIP. The adsorption capacity of U(VI) was determined to be 1.06 and 0.85 mg g−1 for the two isotherms, respectively. The order of selectivity was found to be U(VI) > Fe(III) > Pb(II). For six cycles of regeneration and reuse, the magnetic polymers maintained their stabilities with only a 4% loss in the extraction efficiency. The average extraction efficiencies of the magnetic polymers for the spiked acid mine drainage and sewage wastewater effluents were 71% and 58% for the magnetic IIP and NIP, respectively. From powder X-ray diffraction analysis, application of the Scherrer equation yielded magnetic nanoparticles of an average mean diameter of 11.9 nm. Thermo-gravimetric analysis revealed that the HCl-leached magnetic polymers had a magnetite residual weight of 5%.

Carbon Nanotube–Chitosan Composite Beads with Radially Aligned Channels and Nanotube‐Exposed Walls for Bilirubin Adsorption

Porous nanocomposite materials combine the advantages of a polymer matrix in forming a stable framework and the nanofillers that provide high surface area. Here, we use carbon nanotubes (CNTs) as nanofillers to fabricate chitosan beads with controlled porous structure. We synthesized spherical chitosan–CNT composite beads via freeze casting by dropping a mixed solution into liquid nitrogen, and the resulting highly porous composite beads contain radially oriented channels with hybrid chitosan–CNT channel walls. In particular, we observed localized regions of small CNT agglomerates embedded within the chitosan matrix at a lower CNT loading (40 wt%), and predominately exposed CNTs distributed throughout the channel walls at a higher loading (80 wt%). Owing to the hierarchical open‐porous structure and mesopores provided by exposed CNTs, these composite beads showed much higher adsorption capacity (43.6 mg g−1 within 2 h) to bilirubin than CNT‐free chitosan beads. Our nanocomposite beads with tunable pore wall structure have potential applications in environmental and biomedical areas such as efficient adsorption materials.

ADSORPTION OF ARSENIC (V) ONTO METAL LOADED CELLULOSE NANOCOMPOSITE BEAD (MCNB)-ISOTHERM AND THERMODYNAMIC STUDY

Normal 0 Metal loaded cellulose nanocomposite bead, batch study, arsenic adsorption, isotherm, water analysis Cellulose nanocomposite bead modified with metal (MCNB) such as Ce, Al and Fe is synthesized for selective adsorption of arsenate anions As(V) from drinking water in batch system. The adsorbent was characterized by FTIR, FESEM, EDS and EPR studies. In the present report arsenic (v) adsorption performance on cerium modified cellulose bead was described. The maximum adsorption of As(V) is near about 100 percent up to an initial arsenic load of 5.0 mg L -1 at the acidic pH of 3.0 and the equilibrium reached in 5hr. The much higher adsorption extent and quick equilibrium time compared to the other reported adsorbents makes the present one as efficient one. Among the three adsorption isotherm models used, Langmuir model fitted the experimental data best and the adsorption is found to be exothermic, spontaneous and random in nature. The process was applied for removal of arsenic from some real sample.

Taguchi design and equilibrium modeling for fluoride adsorption on cerium loaded cellulose nanocomposite bead

The cooperative influence of operational variables for fluoride adsorption on cerium loaded cellulose nanocomposite bead (CCNB) was assessed using Taguchi design tool. The percentage contribution of each operational variable was determined. The solution pH, with a maximum contribution of 80.78%, indicates its highest influence on the response, the adsorption percent of fluoride. The quality and validity of the experimental design were assessed from ANOVA and subsequently by the confirmation experiment. The equilibrium adsorption data showed that the Temkin isotherm is the most suited one compared to the Langmuir and Freundlich model. It is found that almost 90% adsorbed fluoride can be eluted with 0.01 (N) NaOH and the regenerated bead can successively be reused for at least three times.

PH sensitive nanocomposite hydrogel beads based on carboxymethyl cellulose/layered double hydroxide as drug delivery systems

In this paper new pH sensitive nanocomposite beads were prepared by the combination of layered double hydroxides (LDH) and carboxymethyl cellulose (CMC). Ibuprofen (IBU), as a model drug, was intercalated between LDH layers through the co-precipitation method. The synthesized LDH-IBU nanohybrids and nanocomposites beads were characterized using FTIR, XRD, and SEM. In vitro tests of drug delivery in conditions simulating the gastrointestinal tract were carried out to prove the effectiveness of this novel type of nanocomposite beads as a controlled drug delivery system (DDS). The drug release tests revealed a better protection against stomach pH and a controlled liberation in the intestinal tract conditions for new nanocomposite beads.

Removal of Silver (I) from Aqueous Solutions by Chitosan/Carbon Nanotube Nanocomposite Beads

Chitosan/CNT nanocomposites were prepared by blending chitosan with carbon nanotubes (CNTs) and forming composite beads. The composites were used as Ag+ adsorbents. Adsorption equilibrium experiments were carried out as a function of contact time, CNTs concentration, pH value, and adsorbent dosage level. The equilibrium time of Ag+ adsorption was found to be 160 min. Composite adsorbent had the highest adsorption efficiency when the weight of CNTs was 0.01 wt%. The maximum Ag+ removal took place at the initial pH value of 3. The optimum adsorbent dosage for Ag+ removal was 5 g. Under above optimal conditions the maximum Ag+ removal was 99.7%. The adsorption isotherm of chitosan/CNT nanocomposite bead agreed well with the Langmuir model. The maximum adsorption capacity was 0.393 mg/g.

On the encapsulation of natural pesticide using polyvinyl alcohol/alginate–montmorillonite nanocomposite for controlled release application

A representative pesticide, NeemAzal was encapsulated into polyvinyl alcohol/alginate‐montmorillonite (PVA/Alg‐MMT) nanocomposite by cross‐linking with glutaraldehyde. Different formulations of capsule beads containing NeemAzal were prepared with different concentration of materials. Evidence of cross‐linking of PVA and Alg was obtained by comparison of the Fourier transform infrared spectra of the initial substrates and capsule beads. X‐ray diffraction and transmission electron microscopy techniques confirmed the intercalated structure of capsule bead nanocomposites. In addition the swelling behavior of capsule beads was investigated. Results showed that swelling ratio of capsule beads decreases with introduction of MMT as well as increase of PVA content in capsule bead formulations. The release characteristics of NeemAzal from capsule beads were monitored using UV–visible spectrophotometer in distilled water. The addition of sodium MMT to these formulations was found to have a profound inhibitory effect on the release of NeemAzal. Furthermore, the release data were fitted to several empirical equations to estimate the kinetic parameters. The NeemAzal encapsulated PVA/Alg‐MMT nanocomposite capsule beads, designed and discussed in this work, have the potential for controlled release of pesticide. POLYM. ENG. SCI., 54:2707–2714, 2014. © 2013 Society of Plastics Engineers

Preparation, characterization and drug delivery behavior of novel biopolymer/hydroxyapatite nanocomposite beads

Nano-sized materials possess uniqueness in their properties and designs as compared to their bulk counterparts. For this reason, they have attracted a great deal of attention from the scientific community. Nanocomposite is a composition having a dispersed material that has one or more dimensions, such as length, width and thickness, in the nanometer size range. The nano-sized materials have emerged as suitable alternatives to overcome drawbacks of composite and microcomposite materials. Biodegradable polymer /hydroxyapatite nanocomposites are a novel class of materials which have recently attracted interest as biomaterials and as drug delivery vehicles. The objectives of the present study were the preparation, evaluation and drug delivery behaviour of nanocomposite beads based on biodegradable polymer sodium alginate and inorganic material hydroxyapatite. In the present study, biopolymer / hydroxyapatite nanocomposite beads have been prepared, optimized and studied in parallel. The prepared nanocomposite beads were characterized by means of XRD, zeta sizer, and SEM, for better understanding regarding their composition and surface morphology. Polydispersity index of particles and mean particle sizes of the nanocomposite beads were measured by zeta sizer. XRD reports confirm the nanocrystalline composition and crystallite size. SEM provided the nanocomposites shapes and their surface topography. The average diameters of particles in the nanocomposites were found to be around 200 nm. We used this biopolymer/hydroxyapatite nanocomposite beads to evaluate its drug delivery behaviour using ofloxacin as a model drug. The in vitro drug-release study confirmed that prepared biopolymer/hydroxyapatite nanocomposite beads exhibited extended release period of drug as compared to the pristine biopolymer sodium alginate.

Montmorillonite–alginate nanocomposite as a drug delivery system – incorporation and in vitro release of irinotecan

The scope of the present study was the preparation and characterization of irinotecan nanocomposite beads based on montmorillonite (Mt) and sodium alginate (AL) as drug carriers. After irinotecan (I) incorporation into Mt, the resulting hybrid was compounded with alginate, and I-Mt-AL nanocomposite beads were obtained by ionotropic gelation technique. The structure and surface morphology of the hybrid and composite materials were established by means of X-ray diffraction (XRD), IR spectroscopy (FT-IR), thermal analysis (TG-DTA) and scanning electron microscopy (SEM). Irinotecan incorporation efficiency in Mt and in alginate beads was determined both by UV-vis spectroscopy and thermal analysis and was found to be high. The hybrid and composite materials were tested in vitro in simulated intestinal fluid (pH 7.4, at 37 °C) in order to establish if upon administering the beads at the site of a resected colorectal tumor, the delivery of the drug is sustained and can represent an alternative to the existing systemic chemotherapy. The in vitro drug release test results clearly suggested that Mt, and Mt along with AL were able to control the release of irinotecan by making it sustained, without any burst effect, and by reducing the released amount and the release rate. The nanocomposite beads may be a promising drug delivery system in chemotherapy.

In situ generation of sodium alginate/hydroxyapatite/halloysite nanotubes nanocomposite hydrogel beads as drug-controlled release matrices.

Diclofenac sodium-loaded sodium alginate/hydroxyapatite/halloysite nanotubes (SA/HA/HNTs-DS) nanocomposite hydrogel beads were prepared by the in situ generation of HA nanoparticles during the sol-gel transition of the SA/HNTs suspension. The nanocomposite beads were characterized by FT-IR spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy, etc. Factors, e.g., the weight ratio of HNTs to SA (mHNTs/mSA), the weight ratio of (NH4)2HPO4 to SA (m(NH4)2HPO4 /mSA), and the concentration of SA, which influenced the entrapment efficiency (EE) and release of DS, were investigated. The EE was enhanced from 62.85 ± 0.29% to 74.63 ± 1.65%, and the burst release of DS was overcome by introducing appropriate amounts of HA and HNTs. An almost constant rate release of DS is achieved when mHNTs/mSA = 0.3 and m(NH4)2HPO4 /mSA = 0.1. The release rate of DS from the SA/HA/HNTs-DS beads was 9.19 mg g-1 h-1. The release of DS is controlled by Case-II transport. The tubular structure of the HNTs and the in situ-formed HA nanoparticles can restrict movability of the SA polymer chains, which is the main reason for the improved drug loading and release behavior.

Nanostructured polymer–titanium composites and titanium oxide through polymer swelling in titania precursor

Polymer (XAD7HP)/Ti4+ nanocomposites were prepared through the swelling of polymer in titanium (IV) ethoxide as a titanium dioxide precursor. The nanocomposite beads exhibit relatively high porosity different than the porosity of the initial polymer. Thermal treatment of composite particles up to 200 °C in vacuum causes the change of their internal structure. At higher temperature, the components of composite become more tightly packed. Calcination at 600 °C and total removal of polymer produce spherically shaped TiO2 condensed phase as determined by XRD. Thermally treated composites show the substantial change of pore dimensions within micro- and mesopores. The presence of micropores and their transformation during thermal processing was studied successfully by positron annihilation lifetime spectroscopy (PALS). The results derived from PALS experiment were compared with those obtaining from low-temperature nitrogen adsorption data.

Effect of gelatin on the in situ formation of Alginate/Hydroxyapatite nanocomposite

Alginate/Hydroxyapatite nanocomposite is a biocompatible and biodegradable multifunctional material suitable for potential biomedical applications such as drug delivery, tissue engineering etc. The in situ method of alginate/hydroxyapatite nanocomposite fabrication usually results in amorphous calcium phosphate. In this study an attempt is made to improve the crystallinity of the hydroxyapatite in the in situ formed nanocomposite. Alginate/Hydroxyapatite nanocomposite beads were fabricated by an in situ method in the presence and absence of gelatin. The composite beads were characterized by Fourier transform IR spectroscopy, XRD and scanning electron microscopy. Gelatin was found to influence the crystallinity of apatite formed and also microstructure of the resulting composite.

Synthesis and study of Prussian blue type nanoparticles in an alginate matrix

A new approach for the synthesis of Prussian blue type nanoparticles containing nanocomposites in the form of beads or films, as well as their corresponding aqueous colloids, was developed by using a water-soluble alginate matrix as a template and as a stabilizing agent. This method consists of the step-by-step building of a cyanometallate network in the pores of Mn+/alginate ionotropic gels in order to obtain a large range of nanocomposites containing cyano-bridged coordination polymer nanoparticles Mn+/[M′(CN)m]3−/alginate (where Mn+ = Ni2+, Cu2+, Mn2+, Fe2+, Eu3+ and M′ = Fe3+, Cr3+ (m = 6), Mo5+ (m = 8)). The nanocomposite beads and films, as well as the corresponding aqueous colloidal solutions, were studied by infrared (IR), UV/visible spectroscopy, and transmission electron microscopy (TEM) analyses, which reveal the presence of homogeneously dispersed uniformly sized cyano-bridged coordination polymer nanoparticles of 3–7 nm. These nanocomposite beads and films present superparamagnetic, spin-glass or paramagnetic behaviour depending on the nature of the metal ions used. In addition, the Eu3+-containing nanocomposites are room temperature optically active emitters displaying a characteristic 5D0 → 7F0–4 transition.

Microdroplet fabrication of silver–agarose nanocomposite beads for SERS optical accumulation

Microdroplets have been used as reactors for the fabrication of agarose beads with high uniformity in shape and size, and densely loaded with silver ions, which were subsequently reduced into nanoparticles using hydrazine. The resulting nanocomposite beads not only display a high plasmonic activity, but can also trap/concentrate analytes, which can be identified by means of surface-enhanced Raman scattering (SERS) spectroscopy. The size of the beads is such that it allows the detection of a single bead under a conventional optical microscope, which is very useful to reduce the amount of material required for SERS detection.

Synthesis and studies of water-soluble Prussian Blue-type nanoparticles into chitosan beads

A new approach to the synthesis of highly stable aqueous colloids of coordination polymer nanoparticles was developed by using water-soluble chitosan beads as template and as stabilizing agent. The method consists in the synthesis of nanocomposite beads containing cyano-bridged coordination polymer nanoparticles via step-by-step coordination of the metal ions and the hexacyanometallate precursors into the chitosan pores and then water solubilization of these as-obtained nanocomposite beads. We obtain a large range of M(2+)/[M'(CN)(6)](3-)/chitosan (where M(2+) = Ni(2+), Cu(2+), Fe(2+), Co(2+), Mn(2+) and M' = Fe(3+) and Cr(3+)) nanocomposite beads and their respective aqueous colloids containing coordination polymer core/chitosan shell nanoparticles. The nanocomposite beads and the corresponding aqueous colloids were studied by Infrared (IR) and UV-Vis spectroscopy, nitrogen sorption (BET), Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM) and magnetic analyses, which reveal the presence of homogeneously dispersed uniformly-sized cyano-bridged coordination polymer nanoparticles. The detailed studies of the static and dynamic magnetic properties of these nanoparticles show the occurrence of a spin-glass like behavior presumably produced by intra-particle spin disorder due to the low spin exchange energy characterizing these materials.

The Rheological Behaviour and Drug-Delivery Property of Chitosan/Rectorite Nanocomposites

The rheological behaviour of the nanocomposites based on chitosan (CS) and unmodified rectorite (REC) were first evaluated. The nanocomposites showed a low shear-rate non-Newtonian viscosity and a rapid shear-thinning behaviour. The zero shear rate viscosity and the storage and loss moduli for the nanocomposites displayed a monotonic increase with increasing REC content in comparison with pure CS. The results implied the presence of electrostatic and hydrogen-bonding interaction between CS and REC, which was corroborated by the SEM images and FT-IR analysis. Then CS beads and CS/REC nanocomposite beads were prepared via the cross-linking interaction of sodium tripolyphosphate and CS, SEM images indicated that the nanocomposite beads had more compact surface and internal structure than those of CS beads. The swelling degree of the nanocomposite beads in 0.9% (w/v) saline was only about 15%, while that of CS beads was 30%. The nanocomposite beads released the drug continuously; in the given 6 days the minimum cumulative release only reached 51.4%, much lower than that of pure CS beads (72.1%). Therefore, CS/REC nanocomposites are more suitable to apply as drug carrier than pure CS.

Highly porous and monodisperse magnetic silica beads prepared by a green templating method

We describe the preparation of magnetic silica nanocomposite millimetric beads using alginate as a green biopolymer template. The simple and soft method which is used here is particularly suitable since the alginate template allows a multiscale control of the structure of the material, both its morphological characteristics at the millimetric scale and its porosity at the nanometric level. These nanocomposites are characterised by a high monodispersity, a perfect spherical shape, a very large and multiscale porosity with pore diameters ranging from 2 nm to more than 50 nm, a homogeneous dispersion of the magnetic nanoparticles in the silica matrix and a high magnetic susceptibility which increases linearly with the volume fraction of the nanoparticles. These highly porous materials which can be used as magnetic adsorbents in water treatment, showed a good sorption capacity for methylene blue, chosen as a model dye.

Preparation of chitosan/magnetite composite beads and their application for removal of Pb(II) and Ni(II) from aqueous solution

A simple and effective process has been proposed to prepare chitosan/magnetite nanocomposite beads with saturation magnetization value as high as uncoated Fe3O4 nanoparticles (ca. 54emu/g). The reason was that the coating chitosan layer was so thin that it did not affect magnetic properties of these composite beads. Especially, chitosan on the surface of the magnetic Fe3O4 nanoparticles is available for coordinating with heavy metal ions, making those ions removed with the assistance of external magnets. Maximum adsorption capacities for Pb(II) and Ni(II), occurred at pH 6 and under room temperature were as high as 63.33 and 52.55mg/g respectively, according to Langmuir isotherm model. These results permitted to conclude that chitosan/magnetite nanocomposite beads could serve as a promising adsorbent not only for Pb(II) and Ni(II) (pH=4–6) but also for other heavy metal ions in wastewater treatment technology.