Banaras Hindu University

About: Banaras Hindu University is a education organization based out in Varanasi, Uttar Pradesh, India. It is known for research contribution in the topics: Population & Dielectric. The organization has 11858 authors who have published 23917 publications receiving 464677 citations. The organization is also known as: Kashi Hindu Vishvavidyalay & Benares Hindu University.

Ecological risk assessment of soil contamination by trace elements around coal mining area

Abstract: Coal mining activities are inevitably connected with production of acidic drainage and airborne compounds such as fly ash and bottom ash with high metal content. Soil is a prominent sink for trace elements discharged from anthropogenic sources. Thus, understanding the occurrence, accessibility and ecological risk of trace elements around coal mining areas is of utmost importance in view of implications for environmental health. Seventy-five soil samples from 25 different sites were collected from Jharia coal field (India) and analyzed for pH, electrical conductivity, total organic carbon, and trace elements. For the background values of trace elements, black shale and sandstone were collected from the study area and analyzed for trace element concentrations. Sampled soils were evaluated for the level of soil contamination with respect to average shale concentrations of toxic trace elements in the region and assessed for their ecological risk in terms of enrichment factor, contamination factor, and pollution load index. Interactions among different trace elements and their spatial distribution were analyzed by the use of multivariate approaches. The study also quantifies the potential sources of contamination for each element and their relation with emission source. The average concentrations of Pb, Ni, Cu, Mn, Fe, Zn, and Cd in the soil exceeded the world averages, while Cu and Zn overstepped their respective critical limit in the soil. Enrichment factor values showed that soil near coal mine areas was loaded with Pb, Cd, Cu, Zn, and Ni. The pollution load index and contamination factor suggest that the soils were contaminated by all the investigated trace elements and areas near coal mines were the most polluted. The absolute principal component score technique, combined with multiple linear regression analysis revealed three major factors, coal mining activities/mine fires (40 %), windblown dust (23 %), and crustal (24 %), were responsible for soil trace element pollution in the area. Coal mining activities, mine fires, and windblown dust are the chief contributors of soil pollution in the area. Coal mining activities/mine fires are the main contributing sources to soil Ni, Cu, and Cr, while crustal input was mainly represented by Mn and Zn and windblown dust for Pb, Fe, and Cd. High concentrations of trace elements at any site depend on the feasibility and availability of respective pollution sources.

Electrochemical sensor for folic acid based on a hyperbranched molecularly imprinted polymer-immobilized sol-gel-modified pencil graphite electrode

Abstract: Contrary to the ‘substructure imprinting approach’ of larger molecule like folic acid, which often leads molecular recognition for both folic acid and structural analogues containing pteridine and glutamic acid substructures, a molecularly imprinted polymer capable of binding specifically folic acid has been prepared by stoichiometric imprinting process (template/monomer molar ratio, 1:3) creating multiple binding sites within the cross-linked hyperbranched polymer. Dendrimer-like chains were obtained by an ‘initiator-fragment incorporation radical polymerization’ technique involving a new trifunctional monomer, 2,4,6-trisacrylamido-1,3,5-triazine. An electrochemical sensor was developed for the selective and quantitative recognition of folic acid, using a preanodized sol–gel coated pencil graphite (grade 2B) electrode with imprinted polymer immobilized to its exterior surface. During preconcentration step at +0.8 V (with respect to Ag/AgCl), the analyte recapture at pH 2.5 in aqueous environment simultaneously involved mixed hydrophobically driven hydrogen bondings and ionic interactions with pteridine substructure and purely hydrogen bonding interactions with glutamic acid residue of folic acid. The encapsulated analyte was instantly oxidized and then cathodically stripped off responding differential pulse cathodic stripping voltammetric signal. The folic acid was selectively detected with a limit of detection of 0.002 μg mL −1 (3 σ , RSD ≤3.0%), without any cross-reactivities and real matrix complications.

Fe3O4@graphene as a superior catalyst for hydrogen de/absorption from/in MgH2/Mg

Abstract: The present investigation describes the hydrogen sorption (de/absorption) behavior of MgH2 catalyzed by graphene sheet templated Fe3O4 nanoparticles (Fe3O4@GS). Hydrogen sorption studies reveal that MgH2 catalyzed by Fe3O4@GS (MgH2:Fe3O4@GS) offers improved hydrogen storage behavior as compared to stand-alone MgH2 catalyzed by graphene sheets (GS) (MgH2:GS) or Fe3O4 nanoparticles (MgH2:Fe3O4). The MgH2:Fe3O4@GS has an onset desorption temperature of ∼262 °C (∼142 °C lower than pristine MgH2), while MgH2:GS and MgH2:Fe3O4 have onset desorption temperatures of ∼275 °C and ∼298 °C respectively. In contrast to this, MgH2:GS absorbs 4.40 wt% and MgH2:Fe3O4 absorbs 5.50 wt% in 2.50 minutes at 290 °C under 15 atm hydrogen pressure. On the other hand, MgH2:Fe3O4@GS absorbs 6.20 wt% hydrogen in 2.50 minutes (which is considerably higher than recently studied catalyzed MgH2 systems) under identical temperature and pressure conditions. The MgH2 catalyzed with Fe3O4@GS shows negligible degradation of the storage capacity even after 25 cycles. Additionally, the desorption activation energy for MgH2:Fe3O4@GS has been found to be 90.53 kJ mol−1 (which is considerably lower as compared to metal/metal oxide catalyzed MgH2 and fluorographene catalyzed MgH2). The formation enthalpy for MgH2:Fe3O4@GS is 60.62 kJ per mole of H2 (13.44 kJ mol−1 lower than bulk MgH2). The catalytic effect of Fe3O4@GS has been described and discussed with the help of structural (X-ray diffraction (XRD)), micro structural (electron microscopy) and Raman spectroscopic studies.