Sadanand Pandey

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.

Development of a sodium alginate-based organic/inorganic superabsorbent composite hydrogel for adsorption of methylene blue.

Batch adsorption experiments were carried out for the removal of methylene blue (MB) cationic dye from aqueous solution using organic/inorganic hydrogel nanocomposite of titania incorporated sodium alginate crosslinked polyacrylic acid (SA-cl-poly(AA)-TiO2). The hydrogel was prepared by graft copolymerization of acrylic acid (AA) onto sodium alginate (SA) biopolymer in the presence of a crosslinking agent, a free radical initiator and TiO2 nanoparticles. The hydrogel exhibited a high swelling capacity of 412.98g/g. The factors influencing adsorption capacity of the absorbents such as pH of the dye solutions, initial concentration of the dye, amount of absorbents, and temperature were investigated and used to propose a possible mechanism of adsorption. The adsorption process concurs with a pseudo-second-order kinetics and with Langmuir isotherm equation. A very high adsorption capacity (Qmax=2257.36 (mg/g)) and a correlation coefficient of 0.998 calculated from isotherm equations show the high efficiency of the absorbent and thus expected to be a good candidate as an absorbent for water treatment.

Facile approach to synthesize chitosan based composite—Characterization and cadmium(II) ion adsorption studies

In this present study, the physicochemical properties, nature and morphology of prepared composite materials involving Activated Eskom fly ash (A-FA) and biopolymer-chitosan (Ch) for two components composite materials were investigated. The nature, morphology, elemental characterizations of these materials were carried out by means of modern analytical methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), UV-vis spectroscopy (UV-vis), and Fourier transform infrared spectroscopy (FTIR. Other physicochemical characterizations undertaken were carbon, nitrogen and hydrogen (CNH) analysis, and ash content. The precursors and composite materials were then applied to the sorption of cadmium (Cd(2+)) from aqueous water. Maximum Cd(2+) adsorption capacity (Qmax) was recorded to be 87.72 mg/g at pH 8. The adsorption kinetics of the composite materials fitted well with the pseudo second-order kinetic model while the adsorption isotherm data could be well described by the Langmuir isotherm model.

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.

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.

Sodium alginate stabilized silver nanoparticles-silica nanohybrid and their antibacterial characteristics.

Due to the problem of resistance of many infectious agents to the usual treatments, this study addresses the ways of obtaining and using new sodium alginate stabilized-silver/mesoporous silica (Na-Alg-s-AgNPs@SiO2) nanohybrid as antimicrobial agents. Capping AgNPs with a shell of mesoporous SiO2 is a system to build the increase biocompatibility of AgNPs. In this work, we report a simple and green way to deal with setting up a uniform sodium alginate-stabilized silver nanoparticles embedded mesoporous silica (Na-Alg-s-AgNPs@SiO2 nanohybrid). The synthesized nanocomposite was characterized using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, and ultraviolet-visible (UV-vis) absorption spectra, which exhibited that AgNPs with average of size of ∼7nm were consistently and compactly deposited in the nanocomposite. The nanohybrid demonstrated excellent antibacterial activity against both Gram negative (-ve) and Gram positive (+ve) bacteria. Thus, the developed Na-Alg-s-AgNPs@SiO2 nanohybrid has a potential to be used for various antibacterial applications in biotechnology and biomedical fields.

Rapid, facile microwave-assisted synthesis of xanthan gum grafted polyaniline for chemical sensor

Grafting method, through microwave radiation procedure is extremely productive in terms of time consumption, cost effectiveness and environmental friendliness. In this study, conductive and thermally stable composite (mwXG-g-PANi) was synthesized by grafting of aniline (ANi) on to xanthan gum (XG) using catalytic weight of initiator, ammonium peroxydisulfate in the process of microwave irradiation in an aqueous medium. The synthesis of mwXG-g-PANi were confirm by FTIR, XRD, TGA, and SEM. The influence of altering the microwave power, exposure time of microwave, concentration of monomer and the amount of initiator of graft polymerization were studied over the grafting parameters, for example, grafting percentage (%G) and grafting efficiency (%E). The maximum %G and %E achieved was 172 and 74.13 respectively. The outcome demonstrates that the microwave irradiation strategy can increase the reaction rate by 72 times over the conventional method. Electrical conductivity of XG and mwXG-g-PANi composite film was performed. The fabricated grafted sample film were then examined for the chemical sensor. The mwXG-g-PANi, effectively integrated and handled, are NH3 sensitive and exhibit a rapid sensing in presence of NH3 vapor. Chemiresistive NH3 sensors with superior room temperature sensing performance were produced with sensor response of 905 at 1ppb and 90% recovery within few second.

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.

Guar gum-grafted poly(acrylonitrile)-templated silica xerogel: nanoengineered material for lead ion removal

BackgroundPolysaccharides are renewable biodegradable natural materials and are accounted for to control the formation of hybrid silica nanocomposites by sol gel process.MethodsThe synthesis of templated silica xerogel essentially includes two critical steps of hydrolysis and polycondensation reaction that are started by catalyst and silica precursor solution. Aside from this Saponification guar-graft-polyacrylonitrile (s-GG-g-PAN) as a copolymer are included in the precursor solution for providing a novel templating environment for silica matrix formation. The s-GG-g-PAN acts as a template for the silica produced in the blended framework because of the hydrogen bonding between the hydroxyl groups at silanols and hydroxyl group and carbonyl groups at the copolymer surface. Connected silanol groups can further hydrolyze and after that take part in the condensation reaction. Accordingly, the s-GG-g-PAN template gets trapped inside the resulting silica system, which on calcining at 900 °C is lost, producing pores of shape and size of the template.ResultsThe surface area and pore volume of the developed templated silica xerogel have been determined. The surface area and pore volume of the template silica xerogel (H900) were observed to be (240 m2 g−1) and (0.286 ccg−1) respectively. The conditions for the adsorption by adsorbent had been enhanced, and kinetics and thermodynamic studies were performed. The best result in terms of lead adsorption was obtained with templated silica xerogel calcined at 900 °C. The % Pb2+ removal is observed to be 96% when H900 adsorbent was treated under ideal adsorption states of measurements 0.05g dose, 500mgL−1 Pb2+ concentration, time 2 h, pH 5 at 30 °C. The adsorption information fitted satisfactorily to Langmuir isotherms, showing unilayer adsorption. In view of the Langmuir model, Qmax was calculated to be 2000 mgg−1. Theadsorption demonstrated pseudo-second-order kinetics. The thermodynamic study revealed the endothermic and spontaneous nature of the adsorption. The adsorbent demonstrated good thermal stability and high reusability.ConclusionsThe present study highlights the possibility of silica xerogel derived from saponified guar gum-grafted poly (acrylonitrile) toward its potential application as superior adsorbent for removal of Pb2+ from aqueous solution.