Faculty Publications
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Item Modelling for organics and nutrients release during Benthal sludge stabilisation : Part I -organics(2008) Bhargava, D.S.; Shrihari, S.Settleable solids in the untreated and partially treated domestic and industrial effluents discharged into a river system undergoes settling and decomposition in the form of benthal sludge deposits, Early models of biochemical oxygen demand (BOD) assimilation in rivers do not account for the BOD contribution by these benthal sludge deposits. In this paper, a model for computations of the BOD contribution by benthos (both from the top aerobic layers and the leached portion of BOD from the bottom anaerobic layers) was presented. Observations from three sets of experiments at the chosen overlying water flow rates (500 ml/min, 1000ml/ min and 1500 ml/min) show a higher BOD contribution by benthos at higher overlying water flow rates. The ratio of the BOD contributions by benthos to the volatile solids in the top aerobic layers was lower when compared to the similar ratio in respect of the bottom layer volatile solids showing that a higher contribution was made by the top layers.Item Modelling for organics and nutrients release during benthal sludge stabilisation part il - Nutrients(2009) Bhargava, D.S.; Shrihari, S.Settleable solids from untreated or partially treated domestic and industrial effluents undergoing stabilisation in stream beds contain significant amount or nutrients such as ammonia and phosphates apart from carbonaceous organic material. An experimental investigation was carried out to study the contribution of biochemical oxygen demand (BOD) and nutrients by this benthal-sludge undergoing stabillisation in steam beds. Sludge was collected from a sewage channel and placed at the bottom of an experimental reactor, and a continuous flow of clean tap water was maintained, in such a manner that the sludge was not disturbed. The first part of this work contained a discussion on degreadation of carbonaceous matter. The degradation of the nutrients, such as ammonia and phosphates being released from the sediments into the overlying waters at different flow rates of over laying waters is evaluated. It was noticed that the ammonia and phosphates released from the sediments into the overlying waters become more or less uniform after some days. The ammonia release and phosphate release were found to be affected by changes in the flowrates of overlying waters. The ammonia and phosphates remaining in the top and bottom layers of the sediments also showed similar trends. Predictive models have been presented for the variation of ammonia and phophate release into the overlying water, ammonia and phosphates remaining in the sediment layers at different times and different flow rates.Item Separation of dimethyl phenol using a spiral-wound RO membrane - Experimental and parameter estimation studies(2009) Srinivasan, G.; Sundaramoorthy, S.; Murthy, D.V.R.Reverse osmosis (RO) is increasingly used as a separation technique in chemical and environmental engineering for the removal of organics and organic pollutants present in waste water. Treatment of organics by RO is dependent on many factors and hence developing a viable RO system involves extensive pilot-plant studies. The removal of an organic compound, namely dimethyl phenol, using a polyamide membrane was investigated in this study. Experiments were conducted on a laboratory-scale spiral-wound RO module. The permeate concentrations and rejection coefficient values were measured for various transmembrane pressures and feed concentrations. A maximum rejection of 97% was observed. A mathematical model was developed for the RO module assuming a solution-diffusion mechanism for solute and solvent transport through the membrane and considering the concentration and pressure to be uniform on both permeate and retentate sides. The model has four parameters. A graphical method for estimating the model parameters was proposed. The model and the estimated parameter values were validated with the experimental data. The model was able to predict the permeate concentration within an error of 19% and rejection within 2% error. © 2009.Item Review of thermal characterization techniques for salt-based phase change materials(Elsevier Ltd, 2022) Agarwala, S.; Prabhu, K.N.Phase change materials (PCM)-based energy storage system is a quite promising technology for the efficient usage of the excess solar energy produced and utilize it at the hour of high demand. The major challenge here is the selection of PCMs for energy storage applications. Inorganic PCMs possess higher thermal conductivity and energy storage capacity when compared to organic PCMs. Thus, inorganic PCMs have a great potential to be used in energy storage systems majorly in medium to high-temperature applications where organic PCMs cannot be used. An accurate and reliable data on the thermophysical properties of the PCMs is essential before its selection and installation of a energy storage system. In this study, various characterization methods based on calorimetry, temperature difference, cooling rate, and cooling curve used to date are described. Methods such as conventionally used differential scanning calorimetry (DSC), T-history method, and computer-aided cooling curve analysis (CACCA) are reviewed and discussed in this study. The two modes of CACCA, Newtonian, and Fourier techniques are explained. The advantages and limitations associated with all these methods are outlined. Inverse heat conduction problem (IHCP)-energy balance method based on CACCA which is devoid of the limitations associated with the conventional characterization methods is discussed. Thermal conductivity is the main characterization parameter of the PCMs and therefore methods to measure thermal conductivity are critically reviewed in this study. Thermal cycling stability is discussed in the context of the review. © 2021 Elsevier LtdItem Synthesis, optical, electrochemical, and computational investigation of new cyanopyridine-centered organic dyads(Elsevier B.V., 2023) Naik, P.; Pilicode, N.; Keremane, K.S.; Acharya, M.; Vasudeva Adhikari, A.V.Herein we report the molecular design, synthesis, and inclusive investigation of four novel di-anchored symmetric dyes (CP1-4) centered on electron deficient cyanopyridine scaffold as possible photosensitizers for DSSC application. These new chromogens (CP1-4) comprise a powerful electron-withdrawing cyanopyridine moiety linked with additional electron attracting functionalities such as cyanoacetic acid (CP1), 3-(carboxymethyl) rhodanine (CP2), 2,4,6-pyrimidinetrione (CP3), and 2,6-dihydroxy-2-mercaptopyrimidine (CP4), as effective acceptor/anchoring units via biphenyl donor units. Their in-depth optical and electrochemical behaviour were investigated to assess their suitability as photosensitizers. Further, the molecular modeling calculations were undertaken to understand their ground state properties and energy level potentials. The comprehensive studies revealed that they own all the requisites to performance as a potential photosensitizer for DSSC application. © 2023 Elsevier B.V.Item Distal Synergistic Effect in Bimetal-Organic Framework for Superior Catalytic Water Oxidation(American Chemical Society, 2023) Bhoi, U.; Ray, S.; Bhand, S.; Ninawe, P.; Roy, D.; Rana, S.; Tarafder, K.; Ballav, N.Metal-organic frameworks (MOFs) are emerging as promising electro-catalysts for the oxygen evolution reaction (OER). The bimetallic design strategy was further adopted in MOFs to elevate the OER performance by a synergistic effect. The proximal metal-oxygen-metal bonding configuration with typical 3dπ-2pπ-3dπ interaction was apparently essential for an effective electronic coupling between the metal centers. Here, we report an example of distal synergy in a bimetal-organic framework exhibiting a better OER activity than the monometallic counterparts, as well as the conventional proximal synergy. To achieve a current density of 10 mA·cm-2, our electrodeposited bimetallic MOF, Co-Ni(TCNQ)2(H2O)2 (TCNQ = 7,7,8,8-tetracyanoquinodimethane), on a glassy-carbon electrode required an overpotential value of 220 mV. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed distinctive electronic coupling between the Co(II)-3d7 and Ni(II)-3d8 centers, despite being 9 Å apart, leading to an overall charge delocalization in the structure via TCNQ. © 2023 American Chemical Society.Item Ultralow thermal conductivity and thermally-deactivated electrical transport in a 1D silver array with alternating δ-bonds(Royal Society of Chemistry, 2024) Hassan, N.; Nagaraja, S.; Saha, S.; Tarafder, K.; Ballav, N.We report the synthesis of a (TMA)AgBr2 (TMA = tetramethylammonium) crystal, which comprises inorganic anionic chains of -(AgBr2)∝- stabilized by columnar stacks of organic TMA cations with a periodic arrangement of shorter and longer Ag(i)⋯Ag(i) bonds, even though all the Ag(i) ions are chemically equivalent. The presence of two chemically non-equivalent bridging Br ions is attributed to the primary cause of such an unusual arrangement, as clearly visualized in the charge density plot of (TMA)AgBr2 extracted from the theoretical calculations based on density functional theory. Remarkably, we identified from the orbital-projected density of states the existence of alternate δ-like bonding involving dxy orbitals of 4d10 Ag(i), which was attributed to the cause for ultralow thermal conductivity and thermally-deactivated electrical transport in (TMA)AgBr2. Barring the energetics, our observations on the existence of a δ-bond will shed new light in understanding the nature of metal-metal chemical bonding and its unprecedented implications. © 2024 The Royal Society of Chemistry.Item Photocatalytic Degradation of Chlorpyrifos and Tetracycline in Aqueous Medium Using Silver Titanate Perovskite Nanoparticles(Springer Science and Business Media Deutschland GmbH, 2024) Joseph, A.; Raval, K.; Manirethan, V.Near-infrared (NIR) active silver titanate perovskite (AgTiO3)-based photocatalysis is a potential method for degrading organic pollutants due to its unique structural features, compositional flexibility, and affordability. Herein, we have synthesized novel NIR-active AgTiO3 nanoparticles with a low band gap of 0.92 eV via the hydrothermal method using Ananas comosus leave extract, which is a major agricultural waste worldwide. The produced AgTiO3 nanoparticles were characterized using Fourier Transform Infrared (FTIR) spectroscopy investigations, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy dispersive X-ray spectroscopy (EDS). The photocatalytic activities of the AgTiO3 nanoparticles toward the degradation of tetracycline and chlorpyrifos under UV, visible, NIR, and solar light irradiation were carefully examined, and the photocatalytic mechanism was proposed using liquid chromatography-mass spectrometry (LC-MS) and high-performance liquid chromatography (HPLC). AgTiO3 nanoparticles completely degraded tetracycline and chlorpyrifos within 27 min and 21 min, respectively. The increased efficiency of AgTiO3 nanoparticles produced by green synthesis over conventional photocatalysts points to a potential advancement avenue for water treatment systems. Furthermore, using agricultural waste like leftover pineapple leaves not only lessens the impact on the environment but also solves the issue of cost when putting these technologies into practice on a larger scale. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Item Push-pull carbazole twin dyads as efficient sensitizers/co-sensitizers for DSSC application: effect of various anchoring groups on photovoltaic performance(Royal Society of Chemistry, 2025) Keremane, K.S.; Abdellah, I.M.; Eletmany, M.R.; Naik, P.; Anees, P.; Vasudeva Adhikari, A.V.To investigate the effect of various anchoring groups of organic sensitizers on fundamental processes occurring inside DSSCs and their overall performance, we designed and synthesized nine new double donor-acceptor (D-A) type organic dyes DCH1-9 comprising carbazole-based twin molecules as electron donors, with a non-conjugated linear alkyl chain as an extended linker featuring multiple acceptor units. Their photophysical, thermal, electrochemical, and theoretical properties were examined to gain a deeper understanding of the structure-property relationship. Photophysical results revealed that all dyes display ?abs and ?emi in the range of 400-470 nm and 500-560 nm, respectively, with a bandgap in the range of 2.46-2.74 eV. The push-pull structure with extended conjugation results in strong fluorescence characteristics. Photophysical and electrochemical studies confirm their thermodynamic feasibility for electron injection, recombination, and dye regeneration in cells. Quantum chemical simulations further provided insights into their structural, electronic, and optical parameters. New DSSCs were fabricated employing dyes DCH1-9 as sensitizers/co-sensitizers. The cell sensitized with DCH1 achieved the highest power conversion efficiency (PCE) of 2.45% under standard AM 1.5 solar conditions. Furthermore, co-sensitization of DCH1-9 with the Ru-based HD-2 sensitizer resulted in an improved PCE of 8.82% for DCH2, surpassing HD-2 alone (6.79%). EIS studies were conducted to further explore their energy conversion processes. Conclusively, these investigations highlight the significant potential of dyes carrying carbazole twin molecules with different anchoring units in enhancing the overall performance of DSSCs. © 2025 The Royal Society of Chemistry.Item Performance analysis of hybrid perovskite solar cells based on different halide ions(Elsevier Ltd, 2025) Jarwal, D.K.; Mishra, A.K.; Dubey, C.; Jangid, A.K.; Bhargava, K.; Kumar, R.; Rawat, G.Here, we have investigated the importance of incorporating different halide ions into perovskite material of the hybrid perovskites-based solar cells (PSCs) and optimized the performance of the PSCs. The n-i-p device structure as FTO/ZnOS/Absorber Material/CuO/Au, is used, where ZnOS and CuO are as electron and hole transport layers, respectively. The CH3NH3PbI3, CH3NH3PbBr3 and CH3NH3PbI3?xClx are exploited as an active absorber layer, with FTO and Au serving as front and back electrodes, respectively. Their performance is studied in terms of various performance parameters viz. Open-circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE). Moreover, a systematic optimization and comparison is conducted to examine the influence of perovskite layer thickness, defect density, and operating temperature on the performance of the three modelled PSCs. The results show that CH3NH3PbI3 based hybrid PSC exhibits the highest PCE of 25.34 % at 300 K, at a defect density of 1015cm?3 and absorber layer thickness of 600 nm. The other key parameters include VOC of 1.15 V, JSC of 25.21 mA/cm2 and FF of 86.4 %. The analysis highlights the importance of numerical simulations in predicting the influence of structural variations in perovskite materials on performance of the hybrid perovskite solar cells. © 2025 Elsevier Ltd