Browsing by Author "Mordekar, Rajashri Karmali"

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    Comparison of degradation of methylene blue dye by zno, n doped zno and iron ore rejects
    (European Chemical Bulletin, 2014) Borker, Vrinda; Mordekar, Rajashri Karmali; Rane, Koyar
    Textile effluent containing unused dye when released in surroundings pollutes water bodies. It requires processing before disposal. Iron ore reject created during mining creates environmental pollution but contains minerals of technological importance. It has ~30-50 % iron in the form of γ-Fe2O3, α-Fe2O3 and Fe3O4 is wasted if thrown in fields, so can be used to degrade organic dyes. Mineralization of methylene blue, MB a model dye is carried out using photocatalyst either iron ore reject, synthesized ZnO or ZnO1-xNx and the results are compared. ZnO is synthesised from oxalate and nitrogen doped ZnO from hydrazinated oxalate precursors. FTIR study of zinc complexes indicates formation of precursors and XRD of decomposed complexes reveal formation of zinc oxide with wurtzite structure. The presence of nitrogen in ZnO1- xNx is confirmed by chemical estimation and XPS studies. SEM reveals the particle size of ZnO1-xNx ~69 nm and ZnO ~0.5-1μm. ZnO1-xNx absorbs in the visible region and ZnO in UV region. Band gap energy calculated using Diffuse reflectance Spectrum is 2.48 eV for the former, 3.19eV for the later and 2.38 eV for ore reject. Mineralizing property of ore reject, ZnO and ZnO1-xNx are compared by electrons spray ionisation mass spectrometry study (ESI-MS) of degradation products, COD measurement and CO2, NO3- and SO4-2 estimation. Reusability study, kinetic study of degradation of MB dye using photocatalysts and ESI-MS study of degraded products of MB reveal better efficacy of iron ore rejects amongst three. Thus efficiency of iron ore reject > ZnO1-xNx. > ZnO as photocatalyst.
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    Experimental validation of vapor-phase direct methanol fuel cell with Pt-Ru/Zeolite electrocatalyst
    (Elsevier, 2025) Naik, Arti K.; Samant, Purnakala V.; Mordekar, Rajashri Karmali
    This study investigates the performance of a vapor-phase Direct Methanol Fuel Cell (DMFC) utilising a Pt-Ru/Zeolite (Pt-Ru/HY) electrocatalyst. The anode material, loaded with 2 wt% metal supported on zeolite (HY), demonstrates superior output voltage and power density compared to conventional Pt/C catalysts inspite of lower noble metal dosage. A Nafion membrane, operating under humidified conditions, effectively enhances proton conductivity and serves as a solid electrolyte. To comprehensively understand fuel cell behavior, a mathematical model is executed for theoretical calculation of diffusion, conductivity, permeability, and Nafion proton conductivity. Experimental validation is conducted by systematically varying operating conditions such as methanol concentration, flow rate, pre-humidified and dehumidified oxygen pressure, and temperature. The study reveals the significance of humidifying both the anode and cathode compartments for reducing voltage losses and increasing power output without much fuel loss. The obtained polarisation curves closely resemble those of traditional DMFCs, confirming the catalyst's effectiveness. Furthermore, the stability of the Pt-Ru/HY catalyst is consistent with reduced ohmic losses, indicating its durability for long-term operation.
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    Silver substituted cobalt zinc ferrites as magnetic antimicrobials
    (Elsevier, 2023) Mordekar, Rajashri Karmali; Samant, Pranita; Mishra, Puja; Joseph, Jaison
    Silver-substituted cobalt zinc ferrite series, CoxAg0.5-xZn0.5Fe2O4 (x = 0.4, 0.3, 0.2, 0.1), is synthesized using the citrate gel method, wherein ferrite formation is achieved at 600 °C. The low-temperature crystallization results in agglomerated and porous ferrites. In this sample preparation methodology, as the silver content in the series increases, metallic silver deposits at the grain boundaries, and vacancies are created at the octahedral sites. With a further increase in silver content, the magnitude of magnetic properties decreases. Antimicrobial activity increases and further decreases with an increase in silver content. The composition Co0.4Ag0.1Zn0.5Fe2O4 exhibits both magnetic and antimicrobial behaviour. These materials can potentially be beneficial in the manufacture of removable antimicrobial agents for water purification and drug delivery systems.