Kaustubha Mohanty

Enhanced CO2 sequestration by a novel microalga: Scenedesmus obliquus SA1 isolated from bio-diversity hotspot region of Assam, India.

The present study aimed to isolate a high CO2 and temperature tolerant microalga capable of sequestering CO2 from flue gas. Microalga strain SA1 was isolated from a freshwater body of Assam and identified as Scenedesmus obliquus (KC733762). At 13.8±1.5% CO2 and 25 °C, maximum biomass (4.975±0.003 g L(-1)) and maximum CO2 fixation rate (252.883±0.361 mg L(-1) d(-1)) were obtained which were higher than most of the relevant studies. At elevated temperature (40 °C) and 13.8±1.5% CO2 maximum biomass (0.883±0.001 g L(-1)) was obtained. The carbohydrate, protein, lipid, and chlorophyll content of the CO2 treated SA1 were 30.87±0.64%, 9.48±1.65%, 33.04±0.46% and 6.03±0.19% respectively, which were higher than previous reports. Thus, SA1 could prove to be a potential candidate for CO2 sequestration from flue gas as well as for the production of value added substances.

CO2 biofixation and carbonic anhydrase activity in Scenedesmus obliquus SA1 cultivated in large scale open system

The present study deals with the large scale open system cultivation of the novel microalga: Scenedesmus obliquus SA1 (KC733762) previously isolated in our laboratory. SA1 strain was cultivated in open system at varying CO2 levels ranging from 0.03% to 35% (v/v) and subsequently the carbonic anhydrase activity (CA) and the biochemical properties were monitored. Maximum biomass concentration (1.39 ± 0.023 g L(-1)), CO2 fixation rate (97.65 ± 1.03 mg L(-1)d(-1)) and total CA activity (166.86 ± 3.30 E.U./mg chla) were obtained at 35% CO2. CA inhibitors: acetazolamide and ethoxyzolamide inhibited the external and internal enzyme activity in SA1. High CO2 levels were favorable for the accumulation of lipids and chlorophyll. The present results suggested that SA1 possessed high CO2 tolerance and high carbohydrate, lipid and chlorophyll content when cultivated in open system thus being suitable for CO2 mitigation in outdoor ponds and subsequent generation of value added products.

Pyrolysis kinetics and thermal behavior of waste sawdust biomass using thermogravimetric analysis

The present study reports pyrolysis behavior of three waste biomass using thermogravimetric analysis to determine kinetic parameters at five different heating rates. Physiochemical characterization confirmed that these biomass have the potential for fuel and energy production. Pyrolysis experiments were carried out at five different heating rates (5-25 °C min-1). Five model-free methods such as Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), Friedman, Coats-Redfern, and distributed activation energy (DAEM) were used to calculate the kinetic parameters. The activation energy was found to be 171.66 kJ mol-1, 148.44 kJ mol-1, and 171.24 kJ mol-1 from KAS model; 179.29 kJ mol-1, 156.58 kJ mol-1, and 179.47 kJ mol-1 from OFW model; 168.58 kJ mol-1, 181.53 kJ mol-1, and 184.61 kJ mol-1 from Friedman model; and 206.62 kJ mol-1, 171.63 kJ mol-1, and 160.45 kJ mol-1 from DAEM model for PW, SW, AN biomass respectively. The calculated kinetic parameters are in good agreement with other reported biomass.

Characterization of nonconventional oil containing seeds towards the production of bio-fuel

This work presents the thermochemical characterization of some nonconventional oil containing seeds. The non-edible and less-edible oil seeds such as Mahua (Madhuca indica), Karanja (Pongamia pinnata), Niger (Hyoscyamus L. Niger), and Linseed (Linum usitatissimum) were characterized on the basis of their degradation profile, oil percentage, cellulose, hemicelluloses, lignin, and mineral content. TGA analysis confirmed that the active pyrolytic zone for all the seeds lies in the temperature range between 150 and 450 °C. It was observed that these seeds contain maximum percent of oil/extractives such as Mahua: 57.16%, Karanja: 53.19%, Niger: 39.75%, and Linseed: 33.55%. The result indicated that these seeds contains higher amount of celluloses than that of hemicelluloses and lignin. The elemental analysis confirmed that these types of biomasses are suitable for pyrolysis due to the presence of less sulphur, less moisture, and higher volatile matter content. The suitability as a feed for fuel production was ...

Preparation and Characterizations of Ceramic Microfiltration Membrane: Effect of Inorganic Precursors on Membrane Morphology

Ceramic disc type microfiltration membranes (50 mm diameter and 5 mm thickness) were prepared by the paste method from different compositions of clay, kaolin, and binding agents like sodium carbonate, sodium metasilicate, boric acid, and sintered at different temperatures. All the membranes were characterized by TGA, SEM, XRD, water permeability test, and acid–base treatment. With the increase of sintering temperature, the pore size as well as the permeability and flexural strength were increasing while porosity and pore density were decreasing. It was found that with increasing the amount of kaolin and decreasing the amount of clay the pore diameter was decreasing. A membrane prepared from 18% clay, 62% kaolin, and 20% binding material and sintered at 1000°C has shown the lowest average pore size of 0.31 μm with porosity, pore density, and flexural strength of 0.22, 4.80 × 1012 m−2 and 12.81 MPa respectively. The membrane pore size and pore density were predicted directly from the particle size distribution of the clay and kaolin and were suitably represented by second-order polynomials.

Insights on the combustion and pyrolysis behavior of three different ranks of coals using reactive molecular dynamics simulation

The process of combustion and pyrolysis of coal can be considered to be convoluted where numerous intermediates are expected to form during the course of the reaction. In this work, we have investigated the reactive products using the ReaxFF force field for three different ranked (low to high) coals, namely lignite, bituminous, and anthracite. It was observed that during the pyrolysis and combustion processes, the gases CO and CO2 were predominant. The formation rate of CO and CO2 was found to be higher for lignite coal which agreed with the experimental trend reported in the literature. In a similar manner, the fraction of CO and CO2 was found to be higher in the pyrolysis process. Further, a large number of principal intermediates such as methane, ethane and ethylene are also generated for low to high ranking (lignite, bituminous, and anthracite) coal. The pyrolysis and combustion processes were affected by temperature (2000–4000 K) with respect to the formation of various intermediates (methane, ethane and ethylene). They were found to be high throughout irrespective of the rank of coal. A higher temperature (2000–4000 K) was adopted in the reactive molecular dynamics (MD) simulation so as to visualize the chemical reactions within a computationally affordable time.

Biosorption of Cr(VI) on immobilized Hydrilla verticillata in a continuous up-flow packed bed: prediction of kinetic parameters and breakthrough curves

abstract In this work, biomass of Hydrilla verticillata, a waste weed was used in its immobilized form to remove hexavalent chromium from aqueous solutions. The powdered biomass was entrapped in polyvinyl alcohol and packed bed studies were carried out using beads of immobilized H. verticillata. Bed height, influent Cr(VI) concentrations, and influent flow rate were variable parameters for the present study. The overall performance of the biosorbent was satisfactory as very high Cr(VI) uptake (45.83 mg g−1) was observed. Three different models—Bed depth service time (BDST), Yoon–Nelson, and Thomas—were studied and fitted to the experimental data. The correlation coefficient values were all above 0.96, whereas the BDST model fitted the data best. From the Thomas model, Thomas rate constant, K Th was calculated and found to be 0.0215 L mg−1 h−1. The data obtained from the Yoon–Nelson model indicated that τ (148 min at 5 mg L−1) values were very similar to experimental (140 min at 5 mg L−1) results. Desorpti...

Effect of Co-pyrolysis of mahua seed and waste polystyrene on quality of liquid fuel

Mahua seed (Madhuca indica) was co-pyrolyzed with waste polystyrene (Thermocol) with an aim to increase the yield and fuel properties of the pyrolytic oil. Co-pyrolysis was carried out at a temperature of 525 °C in a semi-batch reactor. Co-pyrolysis experiments were performed by varying Mahua seed to waste polystyrene ratios such as 1:1, 2:1, 4:1, and 8:1. The condensed liquid product was collected as aqueous and oil phase. The fuel properties and composition of the co-pyrolytic oil were evaluated and compared with that of Mahua seed pyrolytic oil. The process was optimized on the basis of high energy content of the pyrolytic oil. The synergistic effect of waste polystyrene during co-pyrolysis with Mahua seed (at the ratio of 2:1) yielded high calorific value, low pH, and low viscous co-pyrolytic oil in comparison with seed pyrolytic oil. Gas chromatography–mass spectrometry (GC-MS) analysis of co-pyrolytic oil confirmed that the amount of esters increased during co-pyrolysis, which resulted in an increas...

Polymer enhanced ultrafiltration of mercury using chitosan impregnated ceramic membrane

Abstract This work reports the removal of mercury from synthetic wastewater by polymer enhanced ultrafiltration (PEUF). A ceramic membrane was prepared from locally available clay and the membrane surface was impregnated using chitosan to reduce the pore size to ultrafiltration range. The average pore size of the membrane was determined from air permeability data and found to be 12 nm. Polyvinyl alcohol (PVA) was used as the chelating agent. The effects of PVA dose, mercury concentration, pH and transmembrane pressure on mercury rejection were investigated. Rejection increased with the increase of PVA dose and decreased with the increase of initial mercury concentration and transmembrane pressure. The maximum rejection of mercury and PVA was found to be 85% and 99.7% respectively. The optimum pH for the operation was also determined. The flux declination rate was observed to be more at higher PVA dose and less at higher pressure. A preliminary membrane cost estimation approach was adopted based on the man...

Prediction of Selective Extraction of Cresols from Aqueous Solutions by Ionic Liquids Using Theoretical Approach

This work reports the prediction of selective extraction of cresol from aqueous solutions using ionic liquids (ILs) as the solvent. Judicious screening of various ILs was carried out for all the three forms of cresol (i.e., o-cresol, m-cresol, and p-cresol). A quantum chemical based theoretical model “conductor-like screening model for real solvents” (COSMO-RS) was used to predict the selectivity of cresol in aqueous medium at infinite dilution. A screening of 360 possible ILs from 15 cations and 24 anions was carried out to determine the best IL for the removal of cresol from water. Amongst the phosphonium and imidazolium based cations, trihexyl tetradecylphosphonium [THTDP] and 1-octyl-3-methylimidazolium [OMIM] gave the highest selectivity other than the anions bromide and chloride. The selectivities for different cresols followed the pattern: m-cresol > p-cresol > o-cresol. Similarly for pyridinium and quinolium based cations, 1-ethylpyridinium [EPY] and 1-octylquinolium [OQU] gave the highest selectivity. Amongst the two cations studied for pyrrolidinium based cations, 1-hexyl-1-methylpyrrolidinium [HMPL] was the best. Trihexyl tetradecylphosphonium salicyclate [THTDP][SAL] gave the highest selectivity of 662 amongst all the ILs screened.