Browsing by Author "Mordekar, Rajashri Karmali"
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Item Comparison of degradation of methylene blue dye by zno, n doped zno and iron ore rejects(Deuton-X Ltd, 2014) Borker, Vrinda; Mordekar, Rajashri Karmali; Rane, KoyarTextile 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.Item Experimental validation of vapor-phase direct methanol fuel cell with Pt-Ru/Zeolite electrocatalyst(Elsevier, 2025) Naik, Arti K.; Samant, Purnakala V.; Mordekar, Rajashri KarmaliThis 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.Item Gliricidia sepium-derived high surface area meso/micro-porous carbon for enhanced capacitance and adsorption performance(Elsevier, 2026) Sakli, Firdosh; Mordekar, Rajashri Karmali; Samant, Purnakala V.Carbon-based materials, due to their unique structural and physicochemical properties, are used in various environmental and energy applications. The present investigation reports a sustainable approach to valorise Gliricidia sepium (GS) into porous carbon with a large surface area. Carbon was synthesized through carbonization and KOH activation, with varying KOH-to-carbon ratios. The influence of the KOH activation ratio showed variation in structural and morphological character in activated carbon, which influenced the electrochemical and dye adsorption performance. Among the samples, GSC5K achieved a specific surface area of 2670 m2 g−1 with a pore volume of 1.33 cm3 g-1, enabling efficient ion transport and adsorption. Further electrochemical studies demonstrated a notable specific capacitance of 329 F g−1 at 5 mV s−1, positioning GSC5K as a strong candidate for supercapacitor application. Additionally, GSC5K demonstrated enhanced methylene blue adsorption (250 mg g−1) achieving complete removal within 120 s under refined kinetic monitoring, surpassing the adsorption capacity of commercial activated carbon. Thus, the work highlights an enhanced GS-derived carbon for sustainable energy storage and wastewater treatment.Item Mycosynthesized magnetite particles:Comparative physicochemical properties and antifungal activity(Elsevier, 2026) Prabhugaonkar, Arya; Mordekar, Rajashri KarmaliThe study focuses on antifungal applications of Fe3O4 synthesized by Chemical and fungal methods. Fe3O4 is synthesized by conventional hydroxide method and mycosynthesized using fungi G. lucidum and P. rimosus. The Fe3O4 synthesized by all three methods is Pure, crystalline and magnetic. Fe3O4 synthesized by fungal methods show fine crystallite size and agglomeration than the one synthesized by chemical method. There is evidence of phenolic and amino groups which are indicative of phytochemicals in mycosynthesized Fe3O4. All synthesized samples are good antifungal agents against pathogenic fungi C. albicans and A. flavus with sensitivity in the range of 500 to 7.81 μg/mL. Fe3O4 synthesized using P. rimosus (P– Fe3O4) shows better sensitivity (S) at concentrations from 500 to 4.0 μg/ml for pathogens C. albicans and A. flavus in comparison to G- Fe3O4 and C– Fe3O4. The materials show sensitivity superior to some of the reported composites of magnetite with noble metals and Schiff bases like Fe3O4@Ag, Fe3O4@SiO2/Schiff Base/Cu(II)MNPS These potential antifungal agents being magnetic, can be used synergistically with antifungal drugs which will facilitate their movement within the target tissue by means of external magnetic field. This will also minimize the dosage and toxicity of the antifungal drugs.Item Resistivity enhancement in c-axis-grown nanograin Mn–Zn ferrite thin films generated through radio frequency sputtering technique(Springer Nature, 2026) Joseph, Jaison; Mordekar, Rajashri Karmali; Mahadevan Pillai, V. P.Ultra-thin ferrite materials synthesis, with physical properties tailored to specific applications is expected to drive innovations in manufacturing techniques and production processes for electronic components and devices. The specific physical properties inherent in ferrite thin films heavily rely on the choice of the target material for film fabrication, selection of fabrication techniques, and the precise deposition parameters employed. Consequently, we resolute to utilize nano-particle ferrite powder as the target in radiofrequency sputtering technique, for producing MnxZn1−xFe2O4 thin films having nanograins and specific grain orientation along c-axis, on a quartz substrate. Remarkably, we observed a substantial increase in resistivity, by a factor of 2 to 3, in thin-film ferrite material compared to the base materials used for its fabrication. This enhanced resistivity is likely an outcome of grain boundary effects that stem from peculiar film growth along c-axis at minimal film thickness, ranging from 590 to 830 Å, wherein the planar transport of charge carriers becomes predominantly prominent.Item Silver substituted cobalt zinc ferrites as magnetic antimicrobials(Elsevier, 2023) Mordekar, Rajashri Karmali; Samant, Pranita; Mishra, Puja; Joseph, JaisonSilver-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.