Faculty Publications
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Item Improved desalination by polyamide membranes containing hydrophilic glutamine and glycine(Springer Science and Business Media Deutschland GmbH, 2019) Kolangare, I.M.; Isloor, A.M.; Siddique, I.; Asiri, A.M.; A.F., A.F.Water desalination and recycling of wastewater is a key challenge to meet water shortage issues. Thin film composite polyamide membranes are widely used for desalination; however, their low permeability due to a poor hydrophilicity is a major drawback. Here, we designed novel thin film composite membranes having good hydrophilicity, permeability, and stability without compromising solute rejection. We improved the membrane hydrophilicity by incorporation of hydrophilic additives, such as glycine and l-glutamine, into the polyamide layer. Hence polyamide-based flat sheet membranes were fabricated via interfacial polymerization of m-phenylenediamine and trimesoyl chloride and then were coated over a polysulfone/sulfonated polyphenylsulfone (85:15) support. Polyamide membranes were then characterized and tested for desalination. Results show that the ridge and valley structure observed by scanning electron microscopy confirms the formation of the polyamide layer on membrane surface. The performance reached the highest pure water flux of 36.23 Lm?2 h?1 and flux recovery ratio of 89.18% for membranes with 2 wt% of l-glutamine. Incorporation of 2 wt% l-glutamine induced a high permeate flux and a maximum rejection of 87.87% for MgSO4, 83.50% for Na2SO4 and 60.77% for NaCl solutions. Overall, the polyamide nanofiltration membrane with hydrophilic groups displayed superior antifouling property and can be used as a potential candidate for desalination. © 2018, Springer Nature Switzerland AG.Item An electroactive ?-phase polyvinylidene fluoride as gel polymer electrolyte for magnesium–ion battery application(Elsevier B.V., 2019) Singh, R.; Janakiraman, S.; Khalifa, M.; Anandhan, S.; Ghosh, S.; Adyam, A.; Biswas, K.The gel polymer electrolytes (GPEs) are currently interesting research area in rechargeable batteries. In the present study, synthesis and characterization of electroactive gel polymer electrolyte (EGPE) for Mg-ion batteries application have been investigated. The bead free electroactive polyvinylidene fluoride (PVDF) with high porosity is achieved by an electrospinning process. The ?-phase of PVDF is polar and electroactive with a high dipole moment. Electroactive ?-phase is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Field emission scanning electron microscopy (FESEM) study is done to analyze the structure and morphology of the electroactive membrane. The electroactive gel polymer electrolyte is formed by immersing an electroactive PVDF membrane in 0.3 M magnesium perchlorate (MgClO4) and propylene carbonate (PC) solution. The ionic conductivity of electroactive ?-phase PVDF membrane is achieved to be 1.49 mS cm?1 at 30 °C, which is higher than commercial available polypropylene (PP) Celgard. Tortuosity of electroactive gel polymer electrolyte is found to be 1.44. The voltage stability of the EGPE is stable up to a high voltage of 5.0 V against Mg+2/Mg. The total ionic transference number and magnesium ion transference number of EGPE are also investigated to confirm high ionic conductivity. © 2019 Elsevier B.V.Item Stearate as a green corrosion inhibitor of magnesium alloy ZE41 in sulfate medium(Elsevier B.V., 2019) Dindodi, N.; Nityananda Shetty, A.N.The efficiency of stearate as a corrosion inhibitor for magnesium alloy ZE41 has been studied in sodium sulfate medium, employing electrochemical techniques like potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of polarization study imply that stearate functions as a mixed-type corrosion inhibitor with a predominant anodic control. The adsorption of stearate on alloy surface is found to obey the Langmuir adsorption isotherm. The proposed inhibition mechanism involved adsorption of stearate onto metal surface, followed by precipitation of magnesium stearate within the microdefects of Mg(OH)2 surface film which enhanced the barrier effect of an otherwise porous partially protective film. © 2014 The AuthorsItem Studies on high performance alkali activated slag concrete mixes subjected to aggressive environments and sustained elevated temperatures(Elsevier Ltd, 2019) Manjunath, R.; Narasimhan, M.C.; Umesha, K.M.In contemporary constructions, there is a continuous drive for enhancing the performances of concrete mixes, both green and as well as on hardened state. Again there are simultaneous efforts to take full advantage of all the various fast-track, state-of-art construction technologies, leading to early completion of efficient, economical and eco-friendly infrastructure projects. The present authors have developed a new class of high performance self-compacting, alkali activated slag concrete mixes (HPAASC) using three industrial by-products, all obtained from iron and steel industry and have evaluated them for their strength properties. While these HPAASC mixes have higher compressive strengths (about 70–90 MPa) and reasonable split-tensile and flexural strengths, they are also self-compacting in nature. In the present paper, the durability performance of this class of mixes on long-term exposure to aggressive environments like acids, sulphates and chlorides is discussed. Strength deteriorations of the standard test specimens subjected to 5% concentrated sulphuric acid solution and so also in 10% magnesium sulphate solution were monitored for a period of one year. The impermeability of the mixes against chloride-ions was evaluated using both Bulk diffusion test (BDT) and the Rapid chloride penetration test (RCPT). Further these mixes were also evaluated for their performance on exposure to sustained elevated temperatures in the range of 200–800 °C. All the specimens were further analysed for their microstructural studies. Results in the present study indicate that, all the HPAASC mixes exhibit better resistances to aggressive environments and sustained elevated temperatures as compared to the OPC-based reference concrete mix. © 2019 Elsevier LtdItem Solar-metallicity gas in the extended halo of a galaxy at z ? 0.12(Oxford University Press, 2020) Pradeep, J.; Sankar, S.; Umasree, T.M.; Narayanan, A.; Khaire, V.; Gebhardt, M.; Sameer; Charlton, J.C.We present the detection and analysis of a weak low-ionization absorber at z = 0.121 22 along the sightline of the blazar PG 1424+240, using spectroscopic data from both HST/COS and STIS. The absorber is a weak Mg II analogue, with an incidence of weak C II and Si II, along with multicomponent C IV and O VI. The low ions are tracing a dense (nH ? 10?3 cm?3) parsec-scale cloud of solar or higher metallicity. The kinematically coincident higher ions are either from a more diffuse (nH ? 10?5–10?4 cm?3) photoionized phase of kiloparsec-scale dimensions or are tracing a warm (T ? 2 × 105 K) collisionally ionized transition temperature plasma layer. The absorber resides in a galaxy overdense region, with 18 luminous (>L?) galaxies within a projected radius of 5 Mpc and velocity of 750 km s?1. The multiphase properties, high metallicity, and proximity to a 1.4L? galaxy, at ? ? 200 kpc and separation |v| = 11 km s?1, favour the possibility of the absorption tracing circumgalactic gas. The absorber serves as an example of weak Mg II–O VI systems as a means to study multiphase high-velocity clouds in external galaxies. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyItem Room-temperature ultraviolet-ozone annealing of ZnO and ZnMgO nanorods to attain enhanced optical properties(Springer, 2020) Alam, M.J.; Murkute, P.; Sushama, S.; Ghadi, H.; Mondal, S.; Paul, S.; Das, D.; Pandey, S.K.; Chakrabarti, S.ZnO and ZnMgO nanorods have proven to be promising materials for sensing, UV and deep UV based optoelectronic applications. A major drawback of ZnO and ZnMgO based thin films and nanorods is the presence of native point defects which deteriorates their optical efficiency and becomes an impediment to their efficient device applications. The furnace and rapid thermal annealing processes have overcome this up to a great extent but being high temperature processes, they put many fabrication and technological limits in device fabrication. Especially keeping an eye on the future flexible devices, herein we report ultraviolet-ozone (UVO) annealing as a room-temperature, simple and cost-effective annealing method to improve the optical efficiency of ZnO and ZnMgO nanorods along with control of defect states. The ZnO and ZnMgO nanorods were grown by hydrothermal method and annealed in UVO irradiation. UVO annealing substantially improved near band emission and suppressed defect band emissions. It is found that zinc interstitial atoms migrate from the top portion of ZnO nanorods towards the bottom of nanorods after UVO annealing, resulting in reduced zinc interstitial defects in the top portion of nanorods. X-ray diffraction results showed improvement in structural properties. XPS results confirmed suppression of oxygen vacancies and zinc interstitials and improvement in lattice oxygen in the ZnO nanorods after UVO annealing. Optimum times of UVO annealing for ZnO and ZnMgO nanorods were 30 and 50 min respectively. These findings will be helpful for the further development of ZnO and ZnMgO nanorods based high performance optoelectronic devices and sensors. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.Item Spatial and temporal variations in river water quality of the Middle Ganga Basin using unsupervised machine learning techniques(Springer Science and Business Media Deutschland GmbH, 2020) Krishnaraj, A.; Deka, P.C.In this study, cluster analysis (CA), principal component analysis (PCA) and correlation were applied to access the river water quality status and to understand spatiotemporal patterns in the Ganga River Basin, Uttara Pradesh. The study was carried out using data collected over 12 years (2005–2017) regarding 20 water quality parameters (WQPs) covering spatially from upstream to downstream Ankinghat to Chopan, respectively (20 stations under CWC Middle Ganga Basin). The temporal variations of river water quality were established using the Spearman non-parametric correlation coefficient test (Spearman R). The highest Spearman R (?0.866) was observed for temperature with the season and a very significant p value of (0.0000). The parameters EC, pH, TDS, T, Ca, Cl, HCO3, Mg, NO2 + NO3, SiO2 and DO had a significant correlation with the season (p < 0. 05). K-means clustering algorithm grouped the stations into four different clusters in dry and wet seasons. Based on these clusters, box and whisker plots were generated to study individual clusters in different seasons. The spatial patterns of river WQ on both seasons were examined. PCA was applied to screen out the most significant water quality parameters due to spatial and seasonal variations out of a large data set. It is a data reduction process and a more conventional way of speeding up any machine learning algorithms. A reduced number of three principal components (PCs) were drawn for 20 WQPs with an explained total variance of 75.84% and 80.57% is observed in the dry and wet season, respectively. The parameters DO, EC_ Gen, P-Tot, SO4 are the most dominating parameters with PC score more than 0.8 in the dry season; similarly, TDS, K, COD, Cl, Na, SiO2 in the wet season. The different components of water quality monitoring, such as spatiotemporal patterns, scrutinize the most relevant water quality parameters and monitoring stations are well addressed in this study and could be used for the better management of the Ganga River Basin. © 2020, Springer Nature Switzerland AG.Item A high thermally stable polyacrylonitrile (PAN)-based gel polymer electrolyte for rechargeable Mg-ion battery(Springer, 2020) Singh, R.; Janakiraman, S.; Khalifa, M.; Anandhan, S.; Ghosh, S.; Adyam, A.; Biswas, K.The ionic conductivity and thermal stability of the electrolyte-separator system is an essential parameter for improving battery performance and safety. The present work addresses the high thermally stable gel polymer electrolyte (GPE) using polyacrylonitrile (PAN) as a polymer membrane and magnesium perchlorate in propylene carbonate (Mg(ClO4)2-PC) as a liquid electrolyte. The PAN based polymer membrane is prepared by electrospinning process which produces a bead free and uniformly distributed nanofibers. The electrospun PAN based GPE is characterized by different physical and electrochemical techniques like X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, ionic conductivity, linear sweep voltammetry, magnesium ion transference number and electrochemical impedance spectroscopy. The ionic conductivity of PAN is 3.28 mS cm?1, compared to that of PP Celgard is 1.97 × 10–4 mS cm?1 at 30 °C. The electrochemical stability of PAN is 4.6 V and also exhibits excellent interfacial stability with magnesium metal. The results showed that the PAN-based GPE has higher ionic conductivity and thermal stability than the polypropylene (PP) Celgard membrane. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.Item Alcohol-based aqueous biphasic system applied to partition four different natural bioactive compounds from Garcinia indica Choisy(Bellwether Publishing, Ltd., 2021) Nainegali, B.S.; Iyyaswami, R.; Belur, P.D.An attempt was made to simultaneously partitioning Anthocyanins (ACN), Hydroxycitric acid (HCA), Garcinol (GL), and Isogarcinol (IGL) from fruit rinds of Garcinia indica using the 1-propanol and magnesium sulfate system. The influences of 1-propanol and magnesium sulfate concentration and Tie line Length (TLL) were investigated to obtain the optimal partitioning and recovery of GL and IGL into the top-phase and ACN and HCA to the bottom phase. The 25% w/w 1-propanol and 12% w/w magnesium sulfate system showed the maximum extraction efficiency for all the compounds. The purity and recovery were further improved by employing the second stage ATPS. © 2020 Taylor & Francis Group, LLC.