Rahul R. Bhosale

Cellulose assisted combustion synthesis of porous Cu–Ni nanopowders

Porous nanopowders of Cu–Ni were synthesized using cellulose fibres as impregnation media at ambient pressure using combustion based techniques. The synthesized nanopowders were characterized using XRD, BET, SEM, TEM etc. The phase development during the synthesis process was evaluated by performing TGA/DTA experiments. The effect of the amount of precursor on the microstructure and porosity of the nanomaterials was investigated and compared with Cu–Ni synthesized using the Solution Combustion Synthesis (SCS) method. The syntheses of nanopowders proceed via ignition in the reaction media containing metal precursors which is followed by high temperature cellulose combustion. Total pore volume and average pore diameter in case of cellulose assisted synthesized samples were found to be greater as compared to SCS samples.

Kinetics of Absorption of Carbon Dioxide in Aqueous Solution of Ethylaminoethanol Modified with N-methyl-2-pyrolidone

In this paper, kinetics of absorption of CO2 in an aqueous ethylaminoethanol (EAE) and formulated solvent (aqueous blend of EAE and N-methyl-2-pyrrolidone (NMP)) was studied in a stirred cell reactor by using a fall in pressure technique. The reaction pathways for CO2–aqueous EAE system were comprehensively described using both zwitterion and termolecular mechanisms. The physico-chemical properties such as density (ρ) and viscosity (μ) of aqueous EAE and formulated solvent and the solubility ( ) and diffusivity of CO2 ( ) in these solvents were estimated experimentally. The reactive absorption of CO2 in an aqueous EAE was observed to be first order with respect to both CO2 and EAE concentrations. Addition of NMP in aqueous EAE enhances the by 40%, which ultimately results into higher CO2 absorption rates in formulated solvent (∼20% higher) compared to that of the aqueous EAE. Effect of concentration of EAE (0.5 to 2 kmol/m3) and temperature (303 to 318 K) on CO2 absorption kinetics was studied in detail and it was realized that the rate of absorption of CO2 in aqueous EAE and formulated solvent was significantly affected by the change in these parameters. The findings obtained during the temperature dependency study further indicates that the activation energy of the absorption of CO2 in aqueous EAE (80.2 kJ/mol) was relatively lower in comparison with the activation energy of the absorption of CO2 in formulated solvent (88.95 kJ/mol). The overall reaction of CO2 with the formulated solvent could be regarded as the reaction of CO2 with aqueous EAE in parallel with the reaction between CO2 and aqueous NMP.

Solar Thermochemical Hydrogen Production via Terbium Oxide Based Redox Reactions

The computational thermodynamic modeling of the terbium oxide based two-step solar thermochemical water splitting (Tb-WS) cycle is reported. The 1st step of the Tb-WS cycle involves thermal reduction of TbO2 into Tb and O2, whereas the 2nd step corresponds to the production of H2 through Tb oxidation by water splitting reaction. Equilibrium compositions associated with the thermal reduction and water splitting steps were determined via HSC simulations. Influence of oxygen partial pressure in the inert gas on thermal reduction of TbO2 and effect of water splitting temperature () on Gibbs free energy related to the H2 production step were examined in detail. The cycle () and solar-to-fuel energy conversion () efficiency of the Tb-WS cycle were determined by performing the second-law thermodynamic analysis. Results obtained indicate that and increase with the decrease in oxygen partial pressure in the inert flushing gas and thermal reduction temperature (). It was also realized that the recuperation of the heat released by the water splitting reactor and quench unit further enhances the solar reactor efficiency. At K, by applying 60% heat recuperation, maximum of 39.0% and of 47.1% for the Tb-WS cycle can be attained.

Kinetics of thermal degradation of renewably prepared amines useful for flue gas treatment

N-ethylmonoethanolamine (EMEA) and N-N-diethylmonoethanolamine (DEMEA) can be prepared from renewable resources and appear to be commercially attractive solvents for post-combustion CO2 capture by absorption/stripping process. In this paper, the thermal degradation of these renewably prepared amines was studied at 423 K and compared with other amines such as monoethanolamine, diethanolamine, triethanolamine, and N-methyl diethanolamine. Furthermore, an investigation of the kinetics of thermal degradation of aqueous EMEA and DEMEA was conducted by using a 600 ml high-temperature high-pressure reactor in the temperature range of 393 to 423 K and amine concentration range of 1 to 3 kmol m−3, respectively. Estimation of the active solvent content of the reaction mixture samples obtained during the degradation experiments was performed using a gas chromatograph (GC) equipped with a Flame Ionization Detector (FID) and a Tenax GC column. The obtained results indicate that the rate of thermal degradation of both aqueous EMEA and DEMEA increases with the increase in the initial amine concentration and temperature. Additionally, the degradation reaction was observed to be first order with respect to the initial amine concentration. Two intrinsic kinetic power law models were formulated to describe the kinetics of the thermal degradation of aqueous EMEA and DEMEA and the kinetic parameters were predicted by using the linear least-squares regression analysis. The kinetic rate constants for the thermal degradation of these renewably prepared amines were determined (both experimentally and by the models) and on the basis of their temperature dependency, the activation energy for the degradation reaction was estimated. This work represents the first attempt towards obtaining the intrinsic kinetic data for thermal degradation of aqueous EMEA and DEMEA and formulating a kinetic model that fits the data based on the initial rate of degradation.

Solar hydrogen production via erbium oxide based thermochemical water splitting cycle

The erbium oxide based water splitting (Eb-WS) cycle was thermodynamically studied by using the HSC Chemistry software and databases. The first step of the Eb-WS cycle involves thermal reduction of Er2O3, whereas the second step corresponds to the production of H2 via water splitting reaction. Equilibrium compositions associated with the thermal reduction and water splitting steps were determined by performing HSC simulations. Influence of partial pressure of oxygen ( PO2) in the inert purge gas on thermal reduction temperature ( TH) and equilibrium compositions associated with the solar thermal dissociation of Er2O3 was identified. Furthermore, energy and exergy analysis of the Eb-WS cycle was carried out to estimate the cycle ( ηcycle) and solar-to-fuel conversion efficiency ( ηsolar−to−fuel). Simulation results indicate that the ηcycle and ηsolar−to−fuel of Eb-WS cycle increase with the decrease in TH. Also, the ηcycle and ηsolar−to−fuel can be increased further via the recuperation of the heat release...

PdZn nanoparticle electrocatalysts synthesized by solution combustion for methanol oxidation reaction in an alkaline medium

Herein, we report the synthesis of PdZn nanoparticle (NP) electrocatalysts for the methanol oxidation reaction (MOR). The PdZn NPs were synthesized by solution combustion synthesis in the presence of Pd(NO3)2·xH2O, Zn(NO3)2·6H2O and glycine in H2O, where glycine acted as a fuel. In this synthesis, the glycine amount was varied with a fixed stoichiometric ratio of Pd- and Zn-precursors at 1 : 1 to obtain two electrocatalysts (PdZn/C) of fuel-high (glycine to metal nitrate ratio = 1.75), PdZn/C (1.75) and fuel-low (glycine to metal nitrate ratio = 0.5), PdZn/C (0.5). The NPs were characterized by X-ray diffractometry, transmission electron microscopy and scanning electron microscopy for the crystallite size, morphology and elemental composition of the electrocatalysts. High-angle annular dark-field-scanning transmission electron microscopy coupled to energy dispersive X-ray spectroscopy was used to obtain the elemental distribution maps of the aggregated NPs, which confirmed the NPs with Pd and Zn in the alloyed state. X-ray photoelectron spectroscopy was performed to analyze the electronic structures of the elements in the samples. The NPs were then applied in the electrocatalysis for MOR in an alkaline medium. We found that PdZn/C showed an improved electrocatalytic activity by a factor of ∼1.4–1.9 in comparison with Pd/C synthesized using the same method. The MOR on PdZn/C (1.75) began at an earlier onset potential and higher current density than for Pd/C and PdZn/C (0.5). Stability tests were performed by chronoamperometry on PdZn/C and Pd/C, and the results showed a higher stability of PdZn/C (1.75) compared to PdZn/C (0.5) and Pd/C. The fuel amount affected the NP sizes, reaction yield and electrocatalytic properties.

Solar thermochemical Dy2O3/DyO water splitting cycle for hydrogen production

The thermodynamic analyses of the dysprosium oxide-based water splitting (Dy-WS) cycle are reported in this paper. The first step of the Dy-WS cycle involves thermal reduction of Dy2O3, whereas water splitting reaction is the following second step. HSC simulation experiments (by varying the partial pressure of O2 and reaction temperature) are performed to identify the equilibrium compositions associated with both the above given steps. Exergy and energy analysis of the Dy-WS cycle is performed to estimate various solar reactor process parameters including the solar-to-fuel conversion efficiency with and without heat recuperation. The HSC simulation results indicate that the solar-to-fuel conversion efficiency for the Dy-WS cycle is comparable with the ceria cycle.

Thermodynamic exergy analysis of dysprosium oxide-based solar thermochemical water-splitting cycle

The effect of water splitting temperature on the parameters required for the design of solar thermal reactor to conduct the dysprosium oxide based water splitting (Dy-WS) cycle was investigated by using the HSC Chemistry software. The effect of water splitting temperature on the absorption efficiency of the solar reactor, net solar energy required to run the Dy-WS cycle, re-radiation heat losses from the solar reactor, heat rejected by different coolers and water splitting reactor involved in this cycle, and solar-to-fuel energy conversion efficiency with and without heat recuperation was explored. Obtained results indicate that the Dy-WS cycle carried out by using the thermal reduction temperature = 2280 K and water splitting temperature = 1000 K yields into solar-to-fuel energy conversion efficiency = 10.3%. This efficiency can be increased up to 14.62% by employing heat recuperation (50%).

Advanced wastewater treatment using microalgae: effect of temperature on removal of nutrients and organic carbon

This study evaluated the use of mixed indigenous microalgae (MIMA) as a treatment process for wastewaters and CO2 capturing technology at different temperatures. The study follows the growth rate of MIMA, CO2 Capturing from flue gas, removals of organic matter and nutrients from three types of wastewater (primary effluent, secondary effluent and septic effluent). A noticeable difference between the growth patterns of MIMA was observed at different CO2 and different operational temperatures. MIMA showed the highest growth grate when injected with CO2 dosage of 10% compared to the growth for the systems injected with 5% and 15 % of CO2. Ammonia and phosphorus removals for Spirulina were 69%, 75%, and 83%, and 20%, 45% and 75 % for the media injected with 0, 5 and 10% CO2. The results of this study show that simple and cost-effective microalgae-based wastewater treatment systems can be successfully employed at different temperatures as a successful CO2 capturing technology even with the small probability of inhibition at high temperatures.

Thermochemical Conversion of CO2 into Solar Fuels Using Ferrite Nanomaterials

This paper reports the synthesis of Ni x Fe 3-x O 4 nanoparticles via sol-gel method. For Ni x Fe 3-x O 4 synthesis, the Ni and Fe precursor salts were dissolved in ethanol and propylene oxide (PO) was added dropwise to the well mixed solution achieve gel formation. As-prepared gels were aged, dried and subsequently calcined upto 600°C in air. The calcined powders were characterized by powder x-ray diffractometer (XRD), BET surface area, as well as scanning (SEM) and transmission (TEM) electron microscopy. The derived Ni x Fe 3-x O 4 nanoparticles were further examined towards thermochemical conversion of CO 2 into solar fuels by performing several reduction/re-oxidation cycles using a thermogravimetric analyzer (TGA).