Department Of Chemistry

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Author: search.filters.author.Dahiya, Amarjeet

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    Reduced and oxidized rice straw biochar for hexavalent chromium adsorption: Revisiting the mechanism of adsorption
    (Elsevier Ltd, 2023-11-01T00:00:00) Dahiya, Amarjeet; Bhardwaj, Akanksha; Rani, Archana; Arora, Meenu; Babu, J. Nagendra
    Surface oxygen functional groups of biochar were tuned by oxidation and reduction of biochar for establishing Cr(VI) adsorption mechanism. Oxygen functional groups (OFGs) on the surface of leached rice straw biochar (LBC4-6) obtained from pyrolysis at 400, 500 and 600 �C, were oxidized to furnish OBC4-6 using modified Hummer's method. Reduced biochar RBC4-6 were obtained by esterification and NaBH4/I2 reduction of oxidized biochar (OBC4-6). The modified biochar were characterized by increase in O/C and H/C ratio, respectively, in case of OBC4-6 and RBC4-6. The Cr(VI) adsorption by modified biochar LBC4-6, OBC4-6, and RBC4-6 showed optimum conditions of pH 3 and dose 0.1 g/L with a good non-linear fit for Langmuir & Freundlich isotherm. The maximum adsorption (Qm) followed the trend: OBC4 (17.47 mg/g) > RBC4 (15.23) > OBC5 (13.23) > LBC4 (10.23) > RBC5 (9.83) > OBC6 (9.60) > RBC6 (7.24) > LBC5 (6.32) > LBC6 (5.98). The adsorption kinetics for adsorption of Cr(VI) on to modified biochar fits pseudo second order (PSO), Elovich and intraparticle diffusion kinetics, showing a chemisorptions in case of biochar L/O/RBC4-6. The lower temperature modified biochar O/RBC4 show better Cr(VI) adsorption. X-ray Photoelectron Spectroscopy (XPS) studies establish optimum OFGs for reduction of Cr(VI) and chelation of the reduced Cr(III). Adsorption and stripping cycles show the oxidized and reduced biochar as better adsorbents with excellent stripping of Cr up to >98 % upon desorption with 1 M NaOH. � 2023
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    Synthesis of in situ immobilized iron oxide nanoparticles (Fe3O4) on microcrystalline cellulose: Ecofriendly and recyclable catalyst for Michael addition
    (John Wiley and Sons Ltd, 2021-09-21T00:00:00) Kumar, Bhupender; Reddy, Marri Sameer; Dwivedi, Kartikey Dhar; Dahiya, Amarjeet; Babu, J. Nagendra; Chowhan, L. Raju
    Microcrystalline cellulose-immobilized Fe3O4 magnetic nanoparticles (Fe3O4@MCC) with iron loading 5%�20% are synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The synthesized nanocomposites were studied for their catalytic activity towards Michael addition reaction by employing 1,3-cyclohexadione/dimedone and styrylisoxazole in an aqueous ethanolic medium. The catalyst with 15% iron loading showed the highest efficiency with an excellent yield. Michael addition reaction is one of the most important reaction for the creation of a carbon�carbon bond and widely used in organic synthesis under mild condition. The prepared catalyst performed well in Michael addition reaction and afforded the product in excellent yield. The products were isolated by simple filtration without use of any chromatographic techniques. The scale-up experiment on 10-mmol scale proved the sustainability of the methodology. The catalyst was recycled, and the recovered catalyst data showed no considerable depreciation in catalytic activity even after 5 consecutive cycles. The advantages of this green and safe procedure include a simple reaction set-up, very mild reaction conditions, high yields, moderate reaction time, recyclable catalyst, and easy separation of the products without use of any tedious separation techniques. � 2021 John Wiley & Sons, Ltd.
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    Synergistic effect of pistachio shell powder and nano-zerovalent copper for chromium remediation from aqueous solution
    (Springer Science and Business Media Deutschland GmbH, 2021-07-06T00:00:00) Kumar, Sandeep; Brar, Ravinderdeep Singh; Babu, J. Nagendra; Dahiya, Amarjeet; Saha, Sandip; Kumar, Avneesh
    Pistachio shell powder supported nano-zerovalent copper (ZVC@PS) material prepared by borohydride reduction was characterized using SEM, FTIR, XRD, TGA/DTA, BET, and XPS. SEM, XRD, and XPS revealed the nano-zerovalent copper to consist of a core-shell structure with CuO shell and Cu(0) core with a particle size of 40�100 nm and spherical morphology aggregated on PS biomass. ZVC@PS was found to contain 39% (w/w %) Cu onto the pistachio shell biomass. Batch sorption of Cr(VI) from the aqueous using ZVC@PS was studied and was optimized for dose (0.1�0.5 g/L), initial Cr(VI) concentration(1�20 mg/L), and pH (2�12). Optimized conditions were 0.1 g/L doses of sorbent and pH=3 for Cr(VI) adsorption. Langmuir and Freundlich adsorption isotherm models fitted well to the adsorption behavior of ZVC@PS for Cr(VI) with a pseudo-second-order kinetic behavior. ZVC@PS (0.1g/L) exhibits qmax for Cr(VI) removal up to 110.9 mg/g. XPS and other spectroscopic evidence suggest the adsorption of Cr(VI) by pistachio shell powder, coupled with reductive conversion of Cr(VI) to Cr(III) by ZVC particles to produce a synergistic effect for the efficient remediation of Cr(VI) from aqueous medium. Graphical abstract: [Figure not available: see fulltext.] � 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.