Faculty Publications

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Author: search.filters.author.Raj Mohan, B.

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    Materials, Energy and Environment Engineering: Select Proceedings of ICACE 2015
    (2017) Raj Mohan, B.; Srinikethan, G.; Meikap, Bhim Charan
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    Efficacy of lead-resistant microorganisms for bioremediation of lead-contaminated sites
    (CRC Press, 2017) Raj Mohan, B.; Jacob, J.M.; Damodharan, D.
    Lead pollution and its associated aftereffects have existed as a major issue affecting the total quality of the environment. Traditional methods of remediating lead-contaminated sites include a variety of physical, thermal, and chemical treatments, which in general are expensive ex situ approaches. In this context, the efficiency of lead-resistant microorganisms for the bioremediation of lead-contaminated soils has emerged as a promising cost-effective technology for practical utilization. In general, the mechanisms of metal resistance in microbes include precipitation of metals such as phosphates, carbonates, and/or sulfides, volatilization via methylation or ethylation, physical exclusion of electronegative components in the membranes and extracellular polymeric substances, energy-dependent metal efflux systems, and intracellular sequestration with low-molecularweight, cysteine-rich proteins. Such mechanisms have been employed in the macrofungus Galerina vittiformis and the marine fungus Aspergillus terreus for the effective Pb uptake from soil and for the biosynthesis of PbSe quantum dots, respectively. The metal removal kinetic data for Pb(II) follow pseudo-second-order equation indicating the removal mechanism is a function of both metal ions and nature of microorganism. © 2017 by Taylor & Francis Group, LLC.
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    Removal of ammonia and particulate matter using a modified turbulent wet scrubbing system
    (2012) Byeon, S.-H.; Lee, B.-K.; Raj Mohan, B.
    Conventional scrubbers are typically modified to serve the needs of modern industries that discharge effluents that cause synergetic, adverse effects on the environment. We designed and developed a modified turbulent wet scrubber (MTWS) to remove air pollutants as they emerge from a coal furnace. Experiments were conducted to estimate the pressure drop and the efficiencies of ammonia gas and particulate removal via the MTWS. The optimum water levels and gas flow rates for effective scrubbing of ammonia gas at different concentrations and particulate matter at different feed rates were estimated. For ammonia gas at a concentration of 45 ppm, a gas flow rate of 3.5 m 3/s and a water level of 58 cm in MTWS and position B (central position of the nozzle) in the water level of the nozzle yielded efficient ammonia gas removal for the given time. Similarly, for a fly ash feeding rate of 140 mg/min, the same gas flow rate and water level in the MTWS yielded high efficiencies even for particles at the submicron level. © 2012 Elsevier B.V. All rights reserved.
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    Evaluating the performance of a turbulent wet scrubber for scrubbing particulate matter
    (Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2013) Lee, B.-K.; Raj Mohan, B.; Byeon, S.-H.; Lim, K.-S.; Hong, E.-P.
    A turbulent wet scrubber was designed and developed to scrub particulate matter (PM) at micrometer and submicrometer levels from the effluent gas stream of an industrial coal furnace. Experiments were conducted to estimate the particle removal efficiency of the turbulent scrubber with different gas flow rates and liquid heads above the nozzle. Particles larger than 1 ?m were removed very efficiently, at nearly 100%, depending upon the flow rate, the concentration of the dust-laden air stream, and the water level in the reservoir. Particles smaller than 1 ?m were also removed to a greater extent at higher gas flow rates and for greater liquid heads. Pressure-drop studies were also carried out to estimate the energy consumed by the scrubber for the entire range of particle sizes distributed in the carrier gas. A maximum pressure drop of 217 mm H2O was observed for a liquid head of 36 cm and a gas flow rate of 7 m3/min. The number of transfer units (NTU) analysis for the efficiencies achieved by the turbulent scrubber over the range of particles also reveals that the contacting power achieved by the scrubber is better except for smaller particles. The turbulent scrubber is more competent for scrubbing particulate matter, in particular PM2.5, than other higher energy or conventional scrubbers, and is comparable to other wet scrubbers of its kind for the amount of energy spent. Copyright © 2013 A&WMA.
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    Effect of chelaters on bioaccumulation of Cd (II), Cu (II), Cr (VI), Pb (II) and Zn (II) in Galerina vittiformis from soil
    (2013) Damodaran, D.; Shetty K, K.; Raj Mohan, B.
    Remediation of heavy metal contaminated soil and water streams are of great necessity as heavy metals are toxic and pose hazardous ecological impacts. Low cost mitigation measures like phytoremediation and mycoremediation are commonly employed. Mycoremediation using macro fungi (mushroom) have proven to provide effective tolerance using an efficient accumulation mechanism in removing heavy metals from soil. The current paper reports the heavy metal remediation potential of macro fungi on soil artificially contaminated with 50mgkg-1 of Cu (II), Cd (II), Cr (VI), Pb (II), and Zn (II) ions. Galerina vittiformis belonging to Strophariacea family was found to be effective in removing the heavy metal from the soil under study within 30 days. Both chemical and biological chelaters at 1, 5, and 10mmolkg-1 concentrations were found to increase the mycoremediation potential of the organism. This study showed that G. vittiformis are efficient in remediating heavy metal from contaminated soil and that their remediation potential can be enhanced by the addition of chelaters. © 2013 Elsevier Ltd.
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    Total phenolics from an endophytic fungus Penicillium sp isolated from Nothapodytes foetida and its optimization
    (2014) Sogra Fathima, B.; Raj Mohan, B.
    Microwave Assisted Extraction (MAE) of total phenolic content (TPC) from an endophytic fungus Penicillium sp. was carried out and the conditions for extraction was optimized by Response Surface Methodology (RSM). The effects of operating conditions (extraction time, extraction temperature and ratio of solvent to sample) on the extraction of TPC were studied using Central Composite Design (CCD). TPC was determined by Folin's Ciocalteau method and the results were expressed in (mg GAE/g Biomass). The optimal processing parameters were found to have significant effect on the extraction of TPC from Penicillium sp. A mathematical model with high determination coefficient R2 of 0.947 was obtained with optimal conditions of extraction of 5.88 minutes, 51.87 °C, and ratio of solvent to sample of 18.66:1. Under these conditions the experimental yield of TPC was 59.42 mg GAE/g Biomass which was close to the predicted value of 59.88mg GAE/g Biomass. This study indicated the potential use of MAE for extraction of antioxidants from the biomass of an endophytic fungus.
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    Uptake of certain heavy metals from contaminated soil by mushroom-Galerina vittiformis
    (Academic Press, 2014) Damodaran, D.; Shetty K, K.; Raj Mohan, B.
    Remediation of soil contaminated with heavy metals has received considerable attention in recent years. In this study, the heavy metal uptake potential of the mushroom, Galerina vittiformis, was studied in soil artificially contaminated with Cu (II), Cd (II), Cr (VI), Pb (II) and Zn (II) at concentrations of 50 and 100. mg/kg. G. vittiformis was found to be effective in removing the metals from soil within 30 days. The bioaccumulation factor (BAF) for both mycelia and fruiting bodies with respect to these heavy metals at 50. mg/kg concentrations were found to be greater than one, indicating hyper accumulating nature by the mushroom. The metal removal rates by G. vittiformis was analyzed using different kinetic rate constants and found to follow the second order kinetic rate equation except for Cd (II), which followed the first order rate kinetics. © 2013 Elsevier Inc.
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    An optimization study of microwave assisted extraction of oil from oily sludge using response surface methodology
    (CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Kumar, B.; Raj Mohan, B.
    Petroleum oily sludge, a hazardous waste, generated by the refineries and at the production sites in huge quantities comprises of a mixture of petroleum hydrocarbons, asphaltenes, long chain paraffinic wax, waste water, sediments and metals. The present study is aimed to recover oil from the petroleum oily sludge using n-heptane as the solvent in microwave assisted solvent extraction process and to optimize the process variables for the recovery of oil from the oily sludge. The simultaneous effects of process variables such as irradiation time (2 - 10 minutes), solvent to sludge ratio (40 – 80 wt %), reactant volume (100 – 300 ml) and microwave power (80 – 400 W) on the recovery of oil were evaluated. A central composite design (CCD) and response surface methodology (RSM) were used for the optimization of the extraction process. Based on the CCD, quadratic model was developed to correlate the extraction process variables with the responses and the model was analysed using appropriate statistical method (ANOVA). Optimization of process variables shows that the maximum recovery of oil was about 88.6% at 100 ml of reactant volume with microwave power output of 351 W at 6.5 minutes of irradiation time with 58.99% of nheptane to sludge ratio. © 2014 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
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    Microwave-Assisted Extraction of Wax from Oily Sludge: An Experimental Study and its Process Variables Optimization Using Response Surface Methodology
    (Bellwether Publishing, Ltd., 2015) Kumar, B.; Raj Mohan, B.
    The wax present in petroleum sludge, generated by refineries and at crude production sites, consists of paraffin hydrocarbons (C18–C36) known as paraffin wax and naphthenic hydrocarbons (C30–C60). The present study is aimed at the recovery of wax from petroleum oily sludge by microwave-assisted solvent extraction using a Toluene/MEK mixture and subsequently de-crystallizing the wax. The process variables affecting the microwave-assisted solvent extraction are optimized for recovery of wax. The simultaneous effects of process variables such as irradiation time (2–10 minutes), solvent to sludge ratio (40–80 wt%), reactant volume (100–300 ml), and microwave power (80–400 W) on the recovery of wax were evaluated. A central composite design and response surface methodology were used for the optimization of the extraction process. Based on the central composite design, quadratic models were developed to correlate the extraction process variables with the responses and the models were analyzed using appropriate statistical methods for analysis of variance. Optimization of process variables shows the maximum recovery of wax was about 79.57% at 300 ml of reactant volume with microwave power output of 400 W at 7.6 minutes of retention time with 56.56% of Toluene/MEK to sludge ratio. © 2015, Taylor & Francis Group, LLC.
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    Insights into the optical and anti-bacterial properties of biogenic PbSe quantum rods Optical and anti-bacterial properties of biogenic PbSe quantum rods
    (Elsevier, 2016) Jacob, J.M.; Raj Mohan, B.; Akshay Gowda, K.M.
    The detailed optical properties of lead selenide (PbSe) quantum rods biosynthesized in marine Aspergillus terreus were apprehended theoretically using ab initio calculations based on the experimental absorption spectrum. These studies indicate that the absorption coefficient of the biosynthesized PbSe quantum rods increases linearly with incident photon energies. The variation of other optical constants like extinction coefficient, refractive index and reflectance was comparable to that of the chemically synthesized counterparts. Further, the high dielectric constant and remarkable fluorescence of the biogenic PbSe quantum rods pronounce their application in opto-electronic devices in the Near Infra-Red and Ultraviolet spectral regime. The biosynthesized PbSe quantum rods were also found to possess appreciable anti-bacterial activity against various gram positive and gram negative bacterial species thus enhancing the relevance of the same for practical utility. Based on these results it can be concluded that biogenic PbSe quantum rods can be envisaged as potential candidates for bio-imaging, bio-sensing and other photo-voltaic applications. © 2014 The Authors