Shivani B. Mishra

Organic-inorganic hybrid of chitosan/organoclay bionanocomposites for hexavalent chromium uptake

Organic-inorganic hybrid of chitosan and nanoclay (Cloisite 10A) was chosen to develop a nanomaterial with combine properties of hydrophilicity of an organic polycation and adsorption capacity of inorganic polyanion. The chitosan/clay nanocomposite (CCN) was prepared by solvent casting method. The material synthesis was found most efficient in adsorbent behavior was studied in detail taking Cr(VI) as representative ion. The chemical, structural and textural characteristics of the material were determined by FTIR, XRD, TEM, SEM and EDAX analysis. XRD and TEM results indicated that an exfoliated structure was formed with addition of small amounts of MMT-Na+(montmorillonite-Na(+)) to the chitosan matrix. These composite material were used for the removal of chromium(VI) from aqueous solution. The conditions for the adsorption by the composite have been optimized and kinetics and thermodynamic studies were performed. Though the adsorption takes place in wide pH range, pH 3 was found most suitable and at this pH the adsorption data were modeled using the Langmuir and Freundlich isotherms at 15 °C and 35 °C, where the data fitted satisfactorily to Langmuir isotherms, the R(2) values being 0.998 and 0.999 respectively indicating unilayer adsorption. Based on Langmuir model, Q(o) was calculated to be 357.14 mg/g. The adsorption showed pseudo second order kinetics with a rate constant of 8.0763 × 10(-4) g mg(-1) min(-1) at 100 ppm Cr(VI) concentration.

Catalytic reduction of p-nitrophenol by using platinum nanoparticles stabilised by guar gum.

We report a facile and green method to synthesise highly stable dispersions of platinum nanoparticles (PtNPs) with an average particle size of ∼ 6 nm. Natural, nontoxic, eco-friendly biopolymer guar gum was utilised as both the reducing and capping agent precursor in aqueous medium. The PtNPs that had been stabilised by guar gum (GG-s-PtNPs) were characterised by UV-vis spectroscopy, XRD, TEM and XPS. GG-s-PtNPs performed better in terms of catalytic activity for the liquid phase reduction of p-nitrophenol (p-NP) compared to p-aminophenol (p-AP). The efficiency of the catalytic reduction of p-NP over GG-s-PtNPs was found to be 97% in a total time of 320 s at room temperature. The mechanisms of the synthesis and catalytic reduction of p-NP are also discussed. The synthesis approach presented here does not require stringent conditions or toxic agents and thus is a straightforward, rapid, efficient, and green approach to the fabrication of highly active catalysts.

Gum ghatti and Fe3O4 magnetic nanoparticles based nanocomposites for the effective adsorption of rhodamine B

This article reports the development of a new nanocomposite using gum ghatti crosslinked with poly(acrylic acid-co-acrylamide) reinforced with iron oxide magnetic nanoparticles. The nanocomposite was characterized through BET, FT-IR, XRD, SEM-EDX, TGA and TEM and applied for the removal of RhB. Different optimized adsorption parameters were adsorbent dose (0.8 g/L) and pH (7.0). The adsorption isotherm data was used to study Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich isotherm models. The value of correlation coefficient confirmed the applicability of Langmuir isotherm model with maximum adsorption efficiency of 654.87 mg/g. The adsorption kinetics data showed pseudo second order reaction. Thermodynamic studies showed that the adsorption process was endothermic and spontaneous. Moreover, the adsorbent was successfully utilized for successive three cycles for the adsorption-desorption of RhB.

Synthesis and DNA binding studies of Ni(II), Co(II), Cu(II) and Zn(II) metal complexes of N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone Schiff-base ligand.

The thiocarbohydrazone Schiff-base ligand with a nitrogen and sulphur donor was synthesized through condensation of pyridine-2-carbaldehyde and thiocarbohydrazide. Schiff-base ligands have the ability to conjugate with metal salts. A series of metal complexes with a general formula [MCl2(H2L)]·nH2O (MNi, Co, Cu and Zn) were synthesized by forming complexes of the N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone (H2L) Schiff-base ligand. These metal complexes and ligand were characterized by using ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FT-IR), 1H and 13C NMR spectroscopy and mass spectroscopy, physicochemical characterization, CHNS and conductivity. The biological activity of the synthesized ligand was investigated by using Escherichia coli DNA as target. The DNA interaction of the synthesized ligand and complexes on E. coli plasmid DNA was investigated in the aqueous medium by UV-Vis spectroscopy and the binding constant (Kb) was calculated. The DNA binding studies showed that the metal complexes had an improved interaction due to trans-geometrical isomers of the complexes than ligand isomers in cis-positions.

Graft copolymerization of ethylacrylate onto xanthan gum, using potassium peroxydisulfate as an initiator.

Graft copolymer of xanthan gum (XG) and ethylacrylate (EA) has been synthesized by free radical polymerization using potassium peroxydisulfate (KPS) as an initiator in an air atmosphere. The grafting parameters, i.e. grafting ratio and efficiency decrease with increase in concentration of xanthan gum from 0.050 mg/25 mL to 0.350 mg/25 mL, but these grafting parameters increase with increase in concentration of ethylacrylate from 9×10(-2) to 17×10(-2) ML(-1), and KPS from 15×10(-3) to 35×10(-3) ML(-1). The graft copolymer has been characterized by FTIR, XRD, TGA and SEM analysis. The grafted copolymer was also evaluated as efficient Zn(2+) metal binder. The grafted copolymer shows improvement in the stability, solubility as well as their sorbing capacity. Thus graft copolymer formed could find applications in metal ion removal and in drug delivery.

Biosorption potential of Gum ghatti-g-poly(acrylic acid) and susceptibility to biodegradation by B. subtilis

This article reports the biosorption potential of Gum ghatti (Gg)-grafted-acrylic acid (AA) polymer and its susceptibility to biodegradation by Bacillus subtilis (BS) in two different liquid media, i.e. phosphate buffered saline (PBS) and mineral salt medium (MSM). The progress of biodegradation was monitored after every 15 days using FT-IR and SEM techniques. The degradation of the polymer was further evidenced by a loss of weight of 23.2% and 27% in BS-MSM and BS-PBS, respectively, after 60 days. The AA-grafted polymer was then utilized for the removal of Pb(II) and Cu(II) from aqueous solution. The adsorption isotherm data were studied using Langmuir, Freundlich, Temkin, Flory-Huggins and Dubinin-Kaganer-Radushkevich isothermal models. High values of correlation coefficients confirmed the applicability of Langmuir isotherm model used to determine the adsorption capacity of the AA-grafted polymer. The maximum adsorption capacity was found to be 84.74 mg/g for Cu(II) and 310.55 mg/g for Pb(II). Kinetic data were evaluated using pseudo first order, pseudo second order, Elovich, intraparticle diffusion and liquid film diffusion models. The experimental kinetic data fitted well with the pseudo second order rate model.

Stabilisation of silver and copper nanoparticles in a chemically modified chitosan matrix

This work describes the stabilisation of silver and copper nanoparticles in chemically modified chitosan colloidal solution. Chitosan-N-2-methylidene-hydroxy-pyridine-6-methylidene hydroxy thiocarbohydrazide (CSPTH) was used as a stabilising and reducing agent for silver and copper nanoparticles. The modified chitosan derivatives and the synthesised nanoparticles were characterised by Fourier transform infrared (FT-IR) spectroscopy, Ultraviolet-visible (UV-Vis) spectroscopy and X-ray diffraction (XRD). Particle size, morphology and segregation of the nanoparticles were determined by transmission electron microscopy (TEM). The size of the nanoparticles was found to be less than 20 nm and 50 nm for silver and copper nanoparticles, respectively. These nanoparticles were stabilised in a chemically modified chitosan solution and their properties were studied using fluorescence spectroscopy, photoluminescence spectroscopy and surface-enhanced Raman scattering (SERS). The optical properties of silver nanoparticles in surface plasmon band (SPB) were enhanced at 407 nm compared to those of copper nanoparticles. Fluorescence (400 nm and 756 nm), photoluminescence (450 and 504 nm) and Raman scattering (1382 and 1581 cm(-1)) properties for the copper nanoparticles were superior to those of the silver nanoparticles.

Microwave synthesized xanthan gum-g-poly(ethylacrylate): an efficient Pb2+ ion binder.

Microwave induced emulsion copolymerization of ethylacrylate and xanthan gum resulted in copolymer samples of different % grafting (%G). The synthesis was done in the presence of catalytic amount of KPS as an initiator and the adsorption behavior of the copolymer (360%G) was investigated by performing both the kinetics and equilibrium studies in batch conditions. The copolymer was characterized by different techniques. Several experimental parameters were varied to optimize the adsorption conditions. The most favorable pH for the adsorption was pH 5, and at this pH the adsorption data were modeled using Langmuir and Freundlich isotherms. On the basis of the Langmuir model, Q0 was calculated to be 142.86 mg g(-1) for microwave synthesized copolymer (mwXG-g-PEA). The sorption by mwXG-g-PEA followed pseudo second-order kinetics where a linear plot of t/(qt) versus t was obtained, the correlation coefficient (R(2)) and rate constant at 100 mg L(-1) Pb(II) being 0.994 and 3.013×10(-4)g/(mg min), respectively.

Effect of functionalization on the adsorption capacity of cellulose for the removal of methyl violet

In this research paper a comparative study has been carried out for the removal of methyl violet dye using unfunctionalized and functionalized cellulose. The functionalization was achieved through esterification of cellulose with furan-2,5-dione. The functionalization of the cellulose was evidenced using BET, FT-IR, SEM and TGA. The adsorption isotherm data was fitted using different isotherm models like Langmuir, Freundlich, Temkin, Flory-Huggins and Dubinin-Kaganer-Radushkevich models and found to follow Langmuir and Temkin isotherm models with high value of correlation coefficients. Functionalized cellulose (106.38 mg g(-1)) showed higher dye removal capability than unfunctionalized cellulose (43.668 mg g(-1)). The kinetics of adsorption was investigated using pseudo first order, second order, Elovich, liquid film diffusion and intra-particle diffusion models. The mechanism of adsorption was found to follow pseudo second order rate equation. Thermodynamic studies showed that the adsorption process was endothermic and spontaneous.

Chromatographic resolution of racemic α-amino acids: Chiral stationary phase derived from modified xanthan gum

Enantiomeric resolution of α-amino acids into L-amino acid and D-amino acid via column chromatography using chiral stationary phase was performed. For this purpose, a dynamic chiral stationary phase prepared by grafting of methylmethacrylate onto xanthan gum (XG) was successfully employed in resolving various α-amino acids racemates. The peculiarities of the chromatographic behaviour of xanthan gum-graft-poly(methylmethacrylate)-amino acid interaction and the mechanism of their retention in column are discussed. The enantioselective properties of the xanthan gum-graft-poly(methylmethacrylate) in the separation of enantiomers of α-amino acids were studied using acidic solution of alanine, leucine, valine and tryptophan. The procedure is characterized by simplicity, efficiency and relatively low cost to analyze enantiomers of some amino acids.