Indian Institute of Technology Guwahati

About: Indian Institute of Technology Guwahati is a education organization based out in Guwahati, Assam, India. It is known for research contribution in the topics: Catalysis & Computer science. The organization has 6933 authors who have published 17102 publications receiving 257351 citations.

Amine-Modified Mesoporous Silica for CO2 Adsorption: The Role of Structural Parameters

Abstract: The present study investigated the role of structural parameters such as pore size, pore volume, and specific surface area of mesoporous silica on the CO2 sorption performance of various amine-functionalized adsorbents. A series of mesoporous silica with different structural properties KIT-6, MCM-41, SBA-15, and HV MCM-41 were synthesized and functionalized with pentaethylenehexamine (PEHA) by wet impregnation. The CO2 sorption performances of the sorbents were evaluated using high pressure gas adsorption analyzer. The sorption capacity of adsorbents follows the order: MCM-41 < HV MCM-41 < SBA-15 ≈ KIT-6 at 105 °C and 1 bar. Larger pore size reduces the mass transfer resistance, and large pore volume improves the PEHA distribution inside the pores. The high specific surface area has little impact during adsorption. Due to the 3D structure with interconnected pores, KIT-6 shows the lowest heat of regeneration (57.8 kJ/mol CO2) during adsorption. The PEHA-impregnated KIT-6 (K-60 PEHA) shows the highest sorp...

Oxyanion-Encapsulated Caged Supramolecular Frameworks of a Tris(urea) Receptor: Evidence of Hydroxide- and Fluoride-Ion-Induced Fixation of Atmospheric CO2 as a Trapped CO32– Anion

Abstract: A tris(2-aminoethyl)amine-based tris(urea) receptor, L, with electron-withdrawing m-nitrophenyl terminals has been established as a potential system that can efficiently capture and fix atmospheric CO2 as air-stable crystals of a CO32–-encapsulated molecular capsule (complex 1), triggered by the presence of n-tetrabutylammonium hydroxide/fluoride in a dimethyl sulfoxide solution of L. Additionally, L in the presence of excess HSO4– has been found to encapsulate a divalent sulfate anion (SO42–) within a dimeric capsular assembly of the receptor (complex 2) via hydrogen-bonding-activated proton transfer between the free and bound HSO4– anions. Crystallographic results show proof of oxyanion encapsulation within the centrosymmetric cage of L via multiple N–H···O hydrogen bonds to the six urea functions of two inversion-symmetric molecules. The solution-state binding and encapsulation of oxyanions by N–H···O hydrogen bonding has also been confirmed by quantitative 1H NMR titration experiments, 2D NOESY NMR ex...

Raman spectra of CdS nanocrystals in Nafion: longitudinal optical and confined acoustic phonon modes

Abstract: Quantum confinement effects on the longitudinal optical and acoustic phonons in CdS nanocrystals in the strongly confined regime in the polymer matrix Nafion are studied using Raman spectroscopy. The LO-phonon modes show size-dependent asymmetric broadening though the broadening and asymmetry are less than those predicted by the phonon confinement models. Two types of confined acoustic modes corresponding to n =1, l =0 and n =1, l =2 spheroidal vibrations are observed. Softening of the spheroidal modes is observed in the strongly confined regime.

Ciprofloxacin degradation from aqueous solution by Fenton oxidation: reaction kinetics and degradation mechanisms

Abstract: Pharmaceutical wastewater from a large number of manufacturing units is extremely contaminated by ciprofloxacin (CIP), an antibiotic drug. In this work, aqueous CIP solution was treated by Fenton oxidation (FO). The effects of typical process parameters on drug mineralization have been reported. The optimal Fe2+/H2O2 molar ratio of 0.125 and pH of 3.5 were determined with 15 mg L−1 initial CIP at 25 °C temperature. Maximum CIP, COD and TOC removal of 74.4, 47.1 and 37.9% were obtained under the optimal conditions. The mean oxidation number of carbon determined in terms of COD and TOC values was in accordance with that from the oxidation number of individual carbon atom. The concentration of hydroxyl radicals was measured using the N,N-dimethyl phenyl hydrazine method using dimethyl sulphoxide as a probe. Thirteen fragments appeared in the mass spectra and the proposed mechanism explored the routes of daughter ion formation. The cleavage of the piperazine ring was more effective in CIP oxidation due to high nucleophilic character of lone pair of electrons present on the nitrogen atom. A simple 2nd order kinetic model was proposed for the oxidation of CIP and degradation products (DPs) with respect to OH˙ concentration. The rate constants of 3.13 × 103, 4.89 × 103 M−1 s−1 were estimated for CIP and DPs. The initial concentration of OH˙ was found to be 11.67 μM.