Incorporation Of Acoustic And Chemical Modifications To Biochar For Pollution Abatement

A series of my researches aim to develop an advanced suitable carbon activation techniques using ultrasound waves, and chemical functionalization for the application of environmental remediation. Ultrasound irradiation exfoliates the graphitic layers of biochar, and creates new/opens the blocked pores, thus creating active sites for chemical activation using amine. CO2 is one of the major air pollutants and a leading cause of the global warming. Thus, it is imperative to establish a proper CCS technology. Reductive photocarboxylation could be an effective way to attach CO2 on carbonaceous structure such as biochar. Biochars have highly porous structure, high surface area and graphitic oxide clusters that consist of the reactive oxygen functional groups such as ̶ COOH, C=O, ̶ OH that are susceptible to amine functionalization. Amine, a nucleophile, can react with CO2, which is an electrophie, to boost adsorption efficiency of the biochar. Furthermore, to identify the impact of amination, the work was carried out in the presence of two different activating agents carbodiimide-benzotriazole and potassium hydroxide and five different amines - tetraethylenepentamine, diethanolamine, monoethanolamine, polyethylenimine, piperazine and their binary and ternary mixtures. The work was further extended to investigate the role of different biomass origin on CO2 capture. Biochars were synthesized from herbaceous, agro-industrial and crop based biomasses and were subjected to three different treatment conditions that involved- I. physical activation, II. chemical activation and III. integrated ultrasonic-amine activation. The last step of this series of works involved investigating the synergistic and antagonistic impact of pyrolysis temperature (in the range of 500-800 ºC) on ultrasound activation and the subsequent CO2 adsorption. It is worth to mention that the conventional carbon activation requires elevated temperature (\u3e700 ºC) and prolonged activation time (\u3e3 hrs). While the method discussed in this dissertation was conducted at near ambient temperature for a very short duration (~30-60sec) and consumes a significantly lower level of energy than conventional carbon activation processes. In addition, this advanced carbon modification method can be adopted for other environmental applications, in addition to CO2 capture and pollutant removal from water and air

Accretion Flow Properties of EXO 1846-031 During its Multi-Peaked Outburst After Long Quiescence

We study the recent outburst of the black hole candidate EXO 1846-031 which went into an outburst in 2019 after almost 34 years in quiescence. We use archival data from Swift/XRT, MAXI/GSC, NICER/XTI and NuSTAR/FPM satellites/instruments to study the evolution of the spectral and temporal properties of the source during the outburst. Low energy X-ray flux of the outburst shows multiple peaks making it a multipeak outburst. Evolving type-C quasi-periodic oscillations (QPOs) are observed in the NICER data in the hard, hard intermediate and soft intermediate states. We use the physical Two Component Advective Flow (TCAF) model to analyze the combined spectra of multiple satellite instruments. According to the TCAF model, the accreting matter is divided into Keplerian and sub-Keplerian parts, and the variation in the observed spectra in different spectral states arises out of the variable contributions of these two types of accreting matter in the total accretion rate. Studying the evolution of the accretion rates and other properties of the accretion flow obtained from the spectral analysis, we show how the multiple peaks in the outburst flux arises out of discontinuous supply and different radial velocities of two types of accreting matter from the pile-up radius. We detect an Fe emission line at $\sim6.6$ keV in the hard and the intermediate states in the NICER spectra. We determine the probable mass of the black hole to be $12.43^{+0.14}_{-0.03}~M_\odot$ from the spectral analysis with the TCAF model. We also estimate viscous time scale of the source in this outburst to be $\sim 8$ days from the peak difference of the Keplerian and sub-Keplerian mass accretion rates.Comment: 15 pages, 8 Figures, 2 Tables (In Communication ApJ

Effect of Pyrolysis Temperature on PhysicoChemical Properties and Acoustic-Based Amination of Biochar for Efficient CO\u3csub\u3e2\u3c/sub\u3e Adsorption

© Copyright © 2020 Chatterjee, Sajjadi, Chen, Mattern, Hammer, Raman and Dorris. The present study examined the effect of pyrolysis temperature on the physicochemical properties of biochar, activation process and carbon capture. Two different categories of biochars were synthesized from herbaceous (miscanthus and switchgrass) and agro-industrial (corn stover and sugarcane bagasse) feedstock under four different pyrolysis temperatures −500, 600, 700, and 800°C. The synthesized biochars underwent sono-amination activation comprising low-frequency acoustic treatment followed by amine functionalization to prepare adsorbents for CO2 capture. The highest increment (200%) of CO2 capture capacity was observed for sono-aminated samples prepared at 600 and 700°C (maximum improvement for miscanthus), while biochars synthesized at 500 and 800°C demonstrated comparatively lesser increment in adsorption capacities that falls in the range of 115–151 and 127–159%, respectively compared to 600 and 700°C. The elevated pyrolysis temperature (particularly 600 and 700°C) resulted in increased %C and %ash contents and reduced %N contents with enhancement of micro surface area and pore volume. Thus, the superior adsorption capacity of miscanthus (at 600 and 700°C) can be attributed to their large surface areas (303–325 m2/g), high carbon contents (82–84%), and low ash contents (4–5%), as well as %N contents after sono-amination that was twice that of raw char

Properties of Faint X-ray Activity of XTE J1908+094 in 2019

We study the properties of the faint X-ray activity of Galactic transient black hole candidate XTE J1908+094 during its 2019 outburst. Here, we report the results of detailed spectral and temporal analysis during this outburst using observations from Nuclear Spectroscopic Telescope Array (NuSTAR). We have not observed any quasi-periodic-oscillations (QPOs) in the power density spectrum (PDS). The spectral study suggests that the source remained in the softer (more precisely, in the soft–intermediate) spectral state during this short period of X-ray activity. We notice a faint but broad Fe Kα emission line at around 6.5 keV. We also estimate the probable mass of the black hole to be 6.5−0.7+0.5M⊙, with 90% confidence

A Water-Soluble Wavy Coordination Polymer of Cu(II) as a Turn-On Luminescent Probe for Histidine and Histidine-Rich Proteins/Peptides

Histidine plays an essential role in most biological systems. Changes in the homeostasis of histidine and histidine-rich proteins are connected to several diseases. Herein, we report a water-soluble Cu(II) coordination polymer, labeled CuCP, for the fluorimetric detection of histidine and histidine-rich proteins and peptides. Single-crystal structure determination of CuCP revealed a two-dimensional wavy network structure in which a carboxylate group connects the individual Cu(II) dimer unit in a syn–anti conformation. The weakly luminescent and water-soluble CuCP shows turn-on blue emission in the presence of histidine and histidine-rich peptides and proteins. The polymer can also stain histidine-rich proteins via gel electrophoresis. The limits of quantifications for histidine, glycine-histidine, serine-histidine, human serum albumin (HSA), bovine serum albumin, pepsin, trypsin, and lysozyme were found to be 300, 160, 600, 300, 600, 800, 120, and 290 nM, respectively. Utilizing the fluorescence turn-on property of CuCP, we measured HSA quantitatively in the urine samples. We also validated the present urinary HSA measurement assay with existing analytical techniques. Job’s plot, 1H NMR, high-resolution mass spectrometry (HRMS), electron paramagnetic resonance (EPR), fluorescence, and UV–vis studies confirmed the ligand displacement from CuCP in the presence of histidine