K. Hidajat

Carboxymethyl-β-cyclodextrin conjugated magnetic nanoparticles as nano-adsorbents for removal of copper ions: Synthesis and adsorption studies

A novel nano-adsorbent, carboxymethyl-β-cyclodextrin modified Fe(3)O(4) nanoparticles (CMCD-MNPs) is fabricated for removal of copper ions from aqueous solution by grafting CM-β-CD onto the magnetite surface via carbodiimide method. The characteristics results of FTIR, TEM, TGA and XPS show that CM-β-CD is grafted onto Fe(3)O(4) nanoparticles. The grafted CM-β-CD on the Fe(3)O(4) nanoparticles contributes to an enhancement of the adsorption capacity because of the strong abilities of the multiple hydroxyl and carboxyl groups in CM-β-CD to adsorb metal ions. The adsorption of Cu(2+) onto CMCD-MNPs is found to be dependent on pH and temperature. Adsorption equilibrium is achieved in 30 min and the adsorption kinetics of Cu(2+) is found to follow a pseudo-second-order kinetic model. Equilibrium data for Cu(2+) adsorption are fitted well by Langmuir isotherm model. The maximum adsorption capacity for Cu(2+) ions is estimated to be 47.2mg/g at 25 °C. Furthermore, thermodynamic parameters reveal the feasibility, spontaneity and exothermic nature of the adsorption process. FTIR and XPS reveal that Cu(2+) adsorption onto CMCD-MNPs mainly involves the oxygen atoms in CM-β-CD to form surface-complexes. In addition, the copper ions can be desorbed from CMCD-MNPs by citric acid solution with 96.2% desorption efficiency and the CMCD-MNPs exhibit good recyclability.

Fe3O4/cyclodextrin polymer nanocomposites for selective heavy metals removal from industrial wastewater.

In this work, carboxymethyl-β-cyclodextrin (CM-β-CD) polymer modified Fe(3)O(4) nanoparticles (CDpoly-MNPs) was synthesized for selective removal of Pb(2+), Cd(2+), Ni(2+) ions from water. This magnetic adsorbent was characterized by TEM, FTIR, XPS and VSM. The adsorption of all studied metal ions onto CDpoly-MNPs was found to be dependent on pH, ionic strength, and temperature. Batch adsorption equilibrium was reached in 45 min and maximum uptakes for Pb(2+), Cd(2+) and Ni(2+) in non-competitive adsorption mode were 64.5, 27.7 and 13.2 mg g(-1), respectively at 25 °C. Adsorption data were fitted well to Langmuir isotherm and pseudo-second-order models for kinetic study. The polymer grafted on MNPs enhanced the adsorption capacity because of the complexing abilities of the multiple hydroxyl and carboxyl groups in polymer backbone with metal ions. In competitive adsorption experiments, CDpoly-MNPs could preferentially adsorb Pb(2+) ions with an affinity order of Pb(2+)>>Cd(2+)>Ni(2+) which can be explained by hard and soft acids and bases (HASB) theory. Furthermore, we explored the recyclability of CDpoly-MNPs.

A new class of hybrid mesoporous materials with functionalized organic monolayers for selective adsorption of heavy metal ions

Thiol- and amino-functionalized SBA-15 silicas with uniform mesoporosities were prepared and employed for removing heavy metal ions from waste water; the thiolated SBA-15 adsorbent exhibited a higher complexation affinity for Hg2+, while the other metal ions (Cu2+, Zn2+, Cr3+ and Ni2+) showed exceptional binding ability with its aminated analogue.

Adsorption of chiral aromatic amino acids onto carboxymethyl-β-cyclodextrin bonded Fe3O4/SiO2 core–shell nanoparticles

Surface of magnetic silica nanoparticles is modified by grafting with carboxymethyl-β-cyclodextrin (CM-β-CD) via carbodiimide activation. The functionalized magnetic core-shell nanoparticles (MNPs) are characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infra Red (FTIR) spectroscopy, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Vibrating Sample Magnetometer (VSM). These nano-sized particles are scrutinized for adsorption of certain chiral aromatic amino acid enantiomers namely, d- and l-tryptophan (Trp), d- and l-phenylalanine (Phe) and d- and l-tyrosine (Tyr) from phosphate buffer solutions. Adsorption capacities of the coated magnetic nanoparticles toward amino acid enantiomers are in the order: l-Trp>l-Phe>l-Tyr and under the same condition, adsorption capacities are higher for l-enantiomers than the corresponding d-enantiomers. All the equilibrium adsorption isotherms are fitted well to Freundlich model. FTIR studies depict significant changes after adsorption of amino acids onto nanoparticles. The stretching vibration frequencies of NH bonds of the amino acid molecules are changed with complex formation through host-guest interaction. The structure and hydrophobicity of amino acid molecules emphasize the interactions between amino acid molecules and the nano-adsorbents bearing cyclodextrin, thus play important roles in the difference of their adsorption behaviors.

Experimental study of a simulated counter-current adsorption system—III. Sorbex operation

Abstract The separation of an aqueous mixture of fructose and glucose has been carried out in a simulated moving bed counter-current adsorption system, operated in a manner similar to the UOP “Sorbex” process. Concentration profiles measured under cyclic steady state conditions are close to the profiles predicted theoretically for the equivalent continuous counter-current system. The conditions on the flow rates which must be fulfilled in order to obtain an operable process are delineated and the effects of the process variables on product quality are examined. Under properly selected conditions product purities and recoveries of 85–95% are obtained. This is comparable with the values quoted for a commercial Sarex system.

Improvement of the hydrothermal stability of fluorinated MCM-41 material

Abstract The formation of regular hexagonal MCM-41 framework was studied using cetyltrimethyl ammonium bromide (CTMABr) as the surfactant template and aerosil-200 powder silica as the silica source under static condition in the presence of fluoride or chloride anions. The hydrothermal stability of MCM-41 framework synthesized in the presence of fluoride anions was found to be remarkably improved as compared with those synthesized in the presence of chloride anions. The improvement of the hydrothermal stability of MCM-41 material is most likely attributed to the formation of SiF bonds on the surface of the mesopores of MCM-41, leading to the natural resistance of the fluorinated surface to the hydrolysis by water molecules.

Adsorption and catalytic combustion of aromatics on platinum-supported MCM-41 materials

Among a series of Pt-supported catalysts prepared by impregnation, the most hydrophobic Pt-supported on MCM-41 (synthesized in the presence of fluoride anions) with large surface area and pore size is found to be the most active catalyst for the combustion of toluene in air, and its activity is maintained even in the presence of water. However, Pt/ZSM-5 with micropores, the smallest pore volume and the least hydrophobicity has the worst catalytic activity. The high oxidation activity of the catalyst depends mainly on its high hydrophobicity (characterized by selective adsorption for H2O and toluene and by FTIR spectra of surface hydroxyl groups) and partly on its large pore size and high Pt loading. The order of the oxidation activity of a series of aromatics with different molecular weight and different boiling point on Pt-supported MCM-41 catalyst is found to be as follows: toluene>benzene>cumene>ethyl benzene>mesitylene.

Experimental study of a simulated counter-current adsorption system-V. Comparison of resin and zeolite absorbents for fructose-glucose separation at high concentration

Abstract The operation of a simulated counter-current adsorption process for separation of fructose-glucose mixtures has been studied experimentally at high concentration under conditions similar to those employed in the commercial process with both CaY zeolite and Duolite resin as the adsorbent. The overall performance of the system is similar for both adsorbents although the flow conditions required to achieve separation are significantly different. At high concentration the equilibrium isotherms deviate somewhat from linearity and this has an important effect on the concentration profile (and therefore the performance) of the counter-current unit. The equilibrium stage model, with due correction for the concentration dependence of the apparent distribution coefficients, is shown to provide a good representation of the system behaviour.

β-Cyclodextrin conjugated magnetic, fluorescent silica core–shell nanoparticles for biomedical applications

We present synthesis of highly uniform magnetic nanocomposite material possessing an assortment of important functionalities: magnetism, luminescence, cell-targeting, and hydrophobic drug delivery. Magnetic particle Fe3O4 is encapsulated within a shell of SiO2 that ensures biocompatibility of the nanocomposite as well as act as a host for fluorescent dye (FITC), cancer-targeting ligand (folic acid), and a hydrophobic drug storage-delivering vehicle (β-cyclodextrin). Our preliminary results suggest that such core-shell nanocomposite can be a smart theranostic candidate for simultaneous fluorescence imaging, magnetic manipulation, cancer cell-targeting and hydrophobic drug delivery.

Synthesis and characterization of β-cyclodextrin-conjugated magnetic nanoparticles and their uses as solid-phase artificial chaperones in refolding of carbonic anhydrase bovine

Surface-functionalized magnetic nanoparticles are widely used in various fields of biotechnology. In this study, beta-cyclodextrin-conjugated magnetic nanoparticles (CD-APES-MNPs) are synthesized and the use of CD-APES-MNPs as a solid-phase artificial chaperone to assist protein refolding in vitro is demonstrated using carbonic anhydrase bovine (CA) as model protein. CD-APES-MNPs are fabricated by grafting mono-tosyl-beta-cyclodextrin (Ts-beta-CD) onto 3-aminopropyltriethoxysilane (APES)-modified magnetic nanoparticles (APES-MNPs). Results obtained from transmission electron microscopy (TEM) and vibrating sample magnetometery (VSM) show that the synthesized magnetic nanoparticles are superparamagnetic with a mean diameter of 11.5 nm. The beta-CD grafting is confirmed by Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The amount of beta-CD grafted on the APES-MNPs is found to be 0.042 mmol g(-1) from elemental analysis. Our refolding results show that a maximum of 85% CA refolding yield can be achieved using these beta-CD-conjugated magnetic nanoparticles which is at the same level as that using liquid-phase artificial chaperone-assisted refolding. In addition, the secondary and tertiary structures of the refolded CA are the same as those of native protein under optimal conditions. These results indicate that CD-APES-MNPs are suitable and efficient stripping agents for solid-phase artificial chaperone-assisted refolding due to easier and faster separation of these nanoparticles from the refolded samples and also due to recycling of the stripping agents.