Prof. Subhajit Dash - Academia.edu (original) (raw)

Papers by Prof. Subhajit Dash

Journal of Nanoscience and Nanotechnology, Jun 1, 2018

Journal of environmental chemical engineering, Oct 1, 2018

Great emphasis is being put in to develop green, efficient and inexpensive adsorbent in recent ye... more Great emphasis is being put in to develop green, efficient and inexpensive adsorbent in recent years. In this study, we demonstrate the potential of coal fly ash (CFA) materials as environmental pollutant adsorbent. The Sulfonic acid functionalized heat and alkali treated CFA (HATF-SO3H), is synthesized by condensation of 3-mercaptopropyltrimethoxysilane (3-MPTS) and heat and alkali treated CFA (HATF) followed by oxidation of surface thiol groups by H2O2 to sulfonic acid groups. The as-synthesized product is used to remove toxic and reactive dyes i.e. Malachite green (MG) and Rhodamine 6G (R6G), which are the main contaminant from the dye manufacturing and textile finishing. The efficiency of the dye adsorption on HATF-SO3H surface was investigated under various experimental parameter such as adsorbent dose, contact time, stirring speed, pH, and temperature. The proficient sorption efficacy of HATF-SO3H towards toxic and reactive dyes (efficiency of MG removal, 99.20%; maximum specific removal : 233.30 mg g −1 : efficiency of R6G removal, 98.70 %; maximum specific removal : 381.70 mg g −1) can be explained from the perspective of both electrostatic and H-bonding interactions between the surface of HATF-SO3H and dye molecules.

Industrial & Engineering Chemistry Research, Sep 16, 2016

The removal of toxic dyes (Methyl Violet, MV; Congo Red, CR; and Malachite Green, MG, respectivel... more The removal of toxic dyes (Methyl Violet, MV; Congo Red, CR; and Malachite Green, MG, respectively) from water using Si-MCM-41 functionalized with aspartic acid (APA), polyethylenimine (PEI), and β-cyclodextrin (β-CD) developed through new facile synthetic routes is reported here. The successful functionalizations of Si-MCM-41 were examined by means of TGA, solid-state 13C CP MAS NMR spectra, FTIR, XRD, nitrogen sorption, FESEM, and TEM. Beside this, the sorption behavior of those sorbents using sorbates is determined by considering some factors like the pH of the medium, contact time, temperature of the medium, concentration of the dye medium, sorbent dose, and agitation speed. The kinetics data fitted a pseudo-second-order model. It is noticed that the Langmuir equation yields an accurate description of these sorption data, implying that monolayer adsorption took place in all sorption processes. The proficient sorption capacities of these adsorbents (qm = 374.89 mg g–1 for MV on Si-MCM-41–APA, qm = 458....

Catalysis Letters, Mar 27, 2018

In this paper, a new convenient strategy for the synthesis of polyethylenimine functionalized Si-... more In this paper, a new convenient strategy for the synthesis of polyethylenimine functionalized Si-MCM-41 grafted on surface modified graphene oxide has been developed. The as-synthesised catalyst exerts good catalytic activity and reusability toward Knoevenagel condensation of different substituted aromatic aldehydes with malononitrile and ethyl cyanoacetate. Moreover, it shows remarkable thermal stability. The physicochemical characteristics of the catalyst as probed by FTIR, XRD, N 2 sorption isotherms, TGA, XPS, FESEM, TEM, and solid state 13 C NMR analyses, were discussed to get an idea about the catalytic mechanism of Knoevenagel condensation.

Journal of Porous Materials, Apr 16, 2016

ChemistrySelect, Feb 13, 2017

In this paper, we report an in-situ facile route to synthesize graphene oxide-SBA-16 (GO-SBA-16) ... more In this paper, we report an in-situ facile route to synthesize graphene oxide-SBA-16 (GO-SBA-16) composite in acidic medium at room temperature. Thermogravimetric analysis (TGA) exhibits excellent stability of the synthesised composite. X-ray diffractograms (XRD), Fourier transformed infrared (FTIR) spectroscopy, and nitrogen sorption isotherms indicated the coexistence of GO and mesoporous silica particles in the composite. Moreover, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images gave clear evidence of the formation of GO-SBA-16 hybrid composite. Apart from this, the synthesised hybrid material shows not only highly proficient sorption capacities of toxic dyes but also excellent catalytic performance. The highly proficient sorption capacity of GO-SBA-16 towards toxic dyes (q m : 358.72 mg g À1 for Malachite Green, MG; q m : 536.63 mg g À1 for Methyl Violet, MV) can be explained on the basis of both hydrogen bonding and electrostatic interactions between the surface of GO-SBA-16 and dye molecules. Furthermore, GO-SBA-16 shows excellent catalytic efficiency towards metal free synthesis of amide from secondary amine and aromatic aldehyde. Finally, used GO-SBA-16 can be well regenerated and reused several times without causing any important decrement in the sorption efficacy and catalytic activity.

Journal of environmental chemical engineering, Dec 1, 2015

Abstract Adsorption of four dyes, namely neutral red (NR), safranin O (SF), reactive red 2 (RR2) ... more Abstract Adsorption of four dyes, namely neutral red (NR), safranin O (SF), reactive red 2 (RR2) and congo red (CR), onto SBA-15 (Santa Barbara Amorphous) material was studied in detail not only to investigate the possible effects of interactions between adsorbate molecules and adsorbent but also the potential of this material for the removal of dyes from wastewater. SBA-15 and dye adsorbed SBA-15 were thoroughly characterised using standard analytical tools. High resolution X-ray diffractogram (HR-XRD) of SBA-15 shows four distinct peaks characteristic of highly ordered mesoporous material. Peak intensities of diffractograms of dye adsorbed SBA-15 are less intense. Nitrogen adsorption-desorption isotherm of SBA-15 is type-IV typical of mesoporous material. Such isotherms of dye adsorbed SBA-15 are different from that of SBA-15. Specific surface area, average pore diameter, and total pore volume decreased on adsorption of dyes- clearly indicating that pores have been blocked. High resolution transmission electron microscopic (HR-TEM) analyses of SBA-15 and dye adsorbed SBA-15 show distinct changes in pore morphology. It is observed that the adsorption capacities of SBA-15 towards NR and SF are much greater in comparison to RR2 and CR. The adsorption kinetics and isotherm follow the pseudo-second-order kinetics model, intraparticle diffusion kinetics model and Langmuir adsorption isotherm model respectively. The thermodynamic parameter suggests that the dye uptake process is spontaneous. The high adsorption capacity of SBA-15 ( q m = 289.86 mg g −1 for NR, q m = 257.73 mg g −1 for SF) is probably due to electrostatic interactions as well as H-bonding interactions between adsorbent and adsorbate molecules.

Industrial & Engineering Chemistry Research, Mar 9, 2017

Journal of environmental chemical engineering, Mar 1, 2016

Abstract The adsorption of four dyes, namely Neutral Red (Basic Red 5, NR), Congo Red (Sodium sal... more Abstract The adsorption of four dyes, namely Neutral Red (Basic Red 5, NR), Congo Red (Sodium salt of 3,3′-([1,1′-biphenyl]-4,4′-diyl)bis(4-aminonaphthalene-1-sulfonic acid, CR)), Safranin O (Basic Red 2, SF), and Reactive Red 2 (Red MX-5B, RR2) onto SBA-16 material was studied in detail to investigate the plausible effect of interactions between the adsorbate and adsorbent molecule vis-a-vis determining the pore structure stability of SBA-16 and its potential application for the removal of these dyes from aqueous media. Various characterization techniques including FTIR spectra, Nitrogen adsorption–desorption isotherms, HR-XRD patterns, FE-SEM and HR-TEM analyses of the adsorbent were carried out to get an insight of pre and post adsorption in surface morphology. It was observed that the dye adsorption did not introduce any serious disorder on the pore structure stability of SBA-16 and this material probably be a very promising adsorbent for the removal of both NR and SF ( q m = 276.24 mg g −1 for NR, q m = 240.39 mg g −1 for SF) from aqueous medium. Various adsorption parameters such as pH, contact time, temperature, dye concentration and adsorbent dosage was studied to provide more information about the adsorption characteristics of SBA-16. Kinetics of adsorption followed pseudo-second-order model as well as intraparticle diffusion model. The adsorption isotherms data was well fitted with the Langmuir isotherm model. Thermodynamic parameters suggest that the dye adsorption process is spontaneous. Finally, desorption experiment indicates very good regeneration efficiency of the adsorbent.

Industrial & Engineering Chemistry Research, Feb 6, 2017

A novel thiol modified coal fly ash (CFA-SH) is successfully synthesized by a facile, efficient a... more A novel thiol modified coal fly ash (CFA-SH) is successfully synthesized by a facile, efficient and environmental friendly process using 3-mercaptopropyltrimethoxysilane (MPTS). Various techniques have been used to characterize thoroughly their structures, surface property as well as the presence of the mercaptopropyl groups. The synthesized material proves to be an effective and selective adsorbent for removal of Hg 2+ and Cd 2+ ions from aqueous solution. The effect of time, pH, sample dose, speed, temperature and metal ion concentrations were investigated thoroughly to optimize sorption process. The kinetics data fitted in accordance with pseudo-second-order model. It is also noticed that Langmuir equation provides an accurate description of these sorption data, implying that monolayer sorption took place during adsorption. The quick and excellent uptake capacities ‫ݍ(‬ : 361.01 mg g-1 for Hg 2+ within 50

New Journal of Chemistry, 2016

Journal of Environmental Chemical Engineering, 2018

Journal of nanoscience and nanotechnology, 2018

Surface modified nano fly ash has been used as an activator, in the reduction of a few cyclic and... more Surface modified nano fly ash has been used as an activator, in the reduction of a few cyclic and acyclic ketones with NaBH4 as reducing agent. Exclusive formation of trans-4--butyl cyclohexanol was observed in such case. Reduction of 3-methylcyclohexanone yielded only cis-3-methylcyclohexanol (equatorial -OH). In case of reduction of other substituted cyclohexanones, propensity to form more of equatorial alcohol was observed. The chemical yields of various alcohols were high (∼95-99%). The rates of reductions of the ketones were also appreciably high. It appears that the silanol groups present in the surface modified fly ash cause nucleophilic activation of the carbonyl groups leading to faster reaction rate. Exclusive formation of the epimer with equatorially disposed -OH group is most likely due to the same reason. Finally, the advantage of the activator lies in its low cost.

Industrial & Engineering Chemistry Research, 2017

RSC Advances, 2016

Surface activated calcined Si-MCM-41 and SBA-16 materials as activators in the reduction of cycli... more Surface activated calcined Si-MCM-41 and SBA-16 materials as activators in the reduction of cyclic ketones.

Industrial & Engineering Chemistry Research, 2016