Triveni Kumar Mahto

Kinetic and thermodynamic study of polyaniline functionalized magnetic mesoporous silica for magnetic field guided dye adsorption

An eco-friendly magnetic mesoporous silica iron oxide (MS@Fe3O4) nanoparticles with a high surface area was fabricated using a colloidal chemical method. Hereafter, polyaniline (PANI) was conjugated into the pores of MS@Fe3O4 to obtain PANI–MS@Fe3O4 nanocomposites. The nanocomposites were essentially monodispersed and highly efficient for the adsorption of methyl orange (MO). In addition, the rate of the adsorption reaction followed pseudo-second-order kinetics and the adsorption isotherm fitted well to the Langmuir isotherm model. The negative values for the change in Gibbs energy (ΔG) and positive value of the change in enthalpy (ΔH) indicated that the overall adsorption process was spontaneous and endothermic in nature. The density functional theory calculation using the Gaussian 09 and GaussView 5.0 programs also supported the electrostatic interaction phenomena between PANI and MO, which is mainly responsible for the adsorption.

Fabrication of a magnetic nanoparticle embedded NH2-MIL-88B MOF hybrid for highly efficient covalent immobilization of lipase

Metal–organic frameworks (MOFs), a class of porous hybrid materials composed of metal ions and organic ligands, have been studied for a variety of applications. In this work, for the first time, magnetic MOFs are developed for lipase immobilization. A general one-step in situ hydrothermal route is developed for the construction of MOFs encapsulating superparamagnetic Fe3O4 nanoparticles. The integration of Fe3O4 nanoparticles into the MOFs exhibits many interesting inherent properties including a porous nature, easy functionalization as well as strong superparamagnetism. Here Candida rugosa lipase (CRL) is covalently attached to amino-rich magnetic MOFs. The resulting magnetic MOFs are characterized by means of field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM) measurements. Then the enzymatic activities of the immobilized CRL are compared with free CRL. The immobilized CRL presented a wider pH tolerance and excellent thermal stability than free CRL. The Michaelis–Menten kinetic constant (Km) and maximum reaction velocity (Vmax) for both free and immobilized lipase are investigated. The loading amount of CRL on the magnetic MOFs was 280 mg per g of support and the immobilized CRL was efficiently recycled for up to nine cycles.

Hydroxyapatite conjugated graphene oxide nanocomposite: a new sight for significant applications in adsorption

Great efforts have been made to develop efficient adsorbents in recent years. In this study, graphene oxide (GO) was synthesized and the surface chemistry of GO was modified by means of hydroxyapatite (HAP) conjugation in order to increase the number of active sites responsible for cationic dye adsorption. The obtained HAP conjugated GO nanocomposites were characterized using various techniques such as FTIR, RAMAN, XRD, TGA, FESEM, BET surface area and AFM. Herein, malachite green (MG) was used as a model dye and the effect of several parameters, including time, pH, temperature, adsorbent dose, and MG concentration, on the adsorption were investigated. The isotherm, kinetic and thermodynamic parameters were measured. The adsorption of MG was best described by the Freundlich isotherm with a pseudo second order kinetic model. In addition, the removal efficiency was maintained at 82% even in the fourth cycle, which supported the reusability and stability of the fabricated nanocomposite for cationic dye adsorption from an aqueous medium.

Study of the Effect of Xanthan Gum Based Graft Copolymer on Water Based Drilling Fluid

This research article consists of the synthesis of xanthan gum (XG)-g-polyacrylamide (PAA) copolymer and its effect in the development of water based drilling fluids. The graft copolymer was synthesized with varying concentration of XG to obtain shear stable and long chain graft copolymer. The obtained graft copolymer was characterized by Fourier transform infrared spectroscopy and Field emission scanning electron microscopy. The synthesized graft copolymer was then utilized as an additive for the development of water based drilling fluid system. The rheological properties of developed drilling fluids have increased significantly with the increase in graft copolymer concentration and these fluids have the capability to control fluid loss during filtration studies. The fluid loss volume was further reduced to 7 ml after the addition of bridging agent. The filtration and rheological properties of this system were compared with conventional water based drilling fluid system developed using partially hydrolyzed polyacrylamide polymer. It was observed that drilling fluid developed using graft copolymer has better rheological and filtration properties than the drilling fluid formulated using partially hydrolyzed polyacrylamide polymer.

Rheological investigations of water based drilling fluid system developed using synthesized nanocomposite

In the present study, polyacrylamide grafted xanthan gum/multiwalled carbon nanotubes (PA-g-XG/MWCNT) nanocomposite was synthesized by free radical polymerization technique using potassium persulfate as an initiator. The polyacrylamide was grafted on xanthan gum backbone in the presence of MWCNT. The synthesized nanocomposite was characterized by X-ray diffraction technique (XRD), and Fourier transform infrared spectroscopy analysis (FT-IR). The morphological characteristics of the nanocomposite were analyzed by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) analyses. Also, its temperature resistance property was observed with Thermogravimetric analysis (TGA). The effect of nanocomposite on the rheological properties of the developed drilling fluid system was analyzed with a strain controlled rheometer and Fann viscometer. Flow curves were drawn for the developed water based drilling fluid system at elevated temperatures. The experimental data were fitted to Bingham, power-law, and Herschel Bulkley flow models. It was observed that the Herschel Bulkley flow model predict the flow behavior of the developed system more accurately. Further, nanocomposite exhibited non-Newtonian shear thinning flow behavior in the developed drilling fluid system. Nanocomposite showed high temperature stability and had a significant effect on the rheological properties of the developed drilling fluid system as compared to conventionally used partially hydrolyzed polyacrylamide (PHPA) polymer.

One-step synthesis of amikacin modified fluorescent carbon dots for the detection of Gram-negative bacteria like Escherichia coli

In this paper, we report a one-step strategy to synthesize amikacin modified fluorescent carbon dots (CDs@amikacin) for assaying pathogenic bacteria, Escherichia coli. Amikacin is a well-known aminoglycoside antibiotic but here we used it as a binding ligand towards E. coli. Here the synthesized carbon dots are used to detect E. coli accompanied with a linear range of 3.904 × 105 to 7.625 × 102 cfu per mL as well as a detection limit of 552 cfu per mL. CDs@amikacin were well dispersed in water with an average particle diameter of ∼2.5 nm and exhibited a quantum yield of 12.35% at a excitation wavelength of 340 nm. The synthesis of CDs@amikacin and their use in the detection of E. coli are simple, cheap and effective process. This study is also successfully applied to the sensing of E. coli in different fruit juice samples like apple, pineapple and orange. We believe that this analytical method can be used in the field of public health as well as food safety.

Fabrication of a Hierarchical TiO2 Microsphere/Carbon Dots Photocatalyst for Oxygen Evolution and Dye Degradation Under Visible Light

Anatase hierarchical TiO2 microsphere/carbon dots composite (HTM/CDs) was fabricated by a facile method for active visible light photocatalysis. The phase, morphology, microstructure and optical properties were investigated by X-ray diffraction, scanning electronmicroscopy, transmission electron microscopy and UV-VIS diffuse reflectance spectroscopy respectively. Under visible light illumination, the fabricated HTM/CDs composite was exhibited an enhanced photo catalytic activity compared to that of pure hierarchical TiO2 microspheres (HTM). Such an enhancement in photocatalytic activity can be attributed to an increase in the absorption of visible light. The photocatalytic activity was investigated by the degradation of a model dyemalachite green (MG) and oxygen production through water splitting.We believe that this type of hybrid material could be used as a highly active and stable visible light photocatalyst to remove pollutants as well as energy production with high performance.