Thermodynamic Feasibility Research Articles

Evaluation of the possibility of using propane and hydrofluorolefin group refrigerants as an eco-friendly replacement for R134a in combined heat transformers

In connection with the gradual reduction in the use of refrigerants of HFC groups, regulated by the Paris Agreement, its amendments and additions, the question arises of finding environmentally friendly working fluids with high thermodynamic efficiency in the thermal transformer cycle. The article discusses the possibility of using refrigerants from the HFO and propane group as environmentally friendly substitutes for R134a for combined vapor compression thermal transformers. The evaluation of the thermodynamic efficiency of the machines for the joint production of heat and cold, produced on the basis of the entropy method of thermodynamic analysis, is carried out. The results of modeling a single-stage combined heat transformer showed the thermodynamic feasibility of using R290 as a substitute for R134a. The analysis of the results obtained showed the limited possibility of effective use of refrigerants of the HFO group as working bodies of combined heat transformers.

Reactivity of an air-stable dihydrobenzoimidazole n-dopant with organic semiconductor molecules

Summary 1,3-Dimethyl-2-(4-(dimethylamino)phenyl)-2,4-dihydro-1H-benzoimidazole, N-DMBI-H, is widely used as an air-stable n-dopant for organic semiconductors. Here, its reactivity is investigated with a variety of imide- and amide-containing semiconductor molecules that have reduction potentials in the range −0.54 to −1.10 V versus ferrocene. Reaction rates correlate poorly with these potentials. The more reactive of the imides form the corresponding radical anions cleanly, but kinetic isotope studies using N-DMBI-D indicate that the reaction proceeds via an initial hydride- or hydrogen-transfer step. For an amide- and ester-rigidified bis(styryl)benzene derivative the hydride-reduced product is stable under an inert atmosphere and can be observed directly; the radical anion can only be obtained in sub-stoichiometric yield and under certain reaction conditions. On the other hand, (N-DMBI)2 rapidly reduces all the imides and amides examined to the corresponding radical anions. The implications of these findings for dopant selection and use are discussed.

Energy efficient process for recovery of rare earths from spent NdFeB magnet by chlorination roasting and water leaching

Rare earth elements are one of the most essential ingredient of modern technological applications. The extraction and recovery of rare earths from primary resources generates huge overburden, which adversely affect the environment. The spent Neodymium-Iron-Boron (NdFeB) magnet can be a potential secondary resource of rare earths through urban mining and recycling. In the earlier studied hydrometallurgical processes for the recovery of rare earths from spent NdFeB magnet, use of concentrated acids during leaching, discharge of acidic effluents and involvement of energy intensive oxidation roasting operations (500–950 °C) found as the major drawbacks of the processes. In view of high energy consumption and environmental concern, the present paper is focused on the development of an energy efficient process for the recovery of rare earths from spent NdFeB magnet. In this study, conventional oxidation roasting-acid leaching method was adapted to a lower temperature chlorination roasting-water leaching process by reducing the roasting temperature to 300 °C. In the process, ammonium chloride (NH4Cl) was used as chloridizing agent. The thermodynamic feasibility for selective chlorination of rare earths in the presence of NH4Cl was studied using FactSage and Thermo Gravimetric- Differential Thermal Analysis (TG-DTA). In order to determine the most suitable chlorination roasting condition, the effect of different parameters such as temperature, NH4Cl dosage and roasting time were studied in detail. The roasted products were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy - Energy Dispersive X-Ray Spectroscopy (SEM-EDS) and chemical analysis. The rare earths were quantitatively and selectively recovered at the most suitable chlorination roasting condition (300 °C, 3 times of stoichiometric amount, 3 h) followed by water leaching. From the leach solution, rare earth oxide of 99.2% purity was produced. The leach residue containing 96.4% Fe2O3 was obtained as a by-product of the process. The lower chlorination roasting temperature and shorter roasting time (300 °C, 3 h) make the process more energy-efficient. The process with zero effluent discharge is easily scalable and environment-friendly.

Deep eutectic solvents on extraction of bisphenol A from water matrices: COnductor like Screening MOdel for Real Solvents prediction and experimental validation

AbstractDensities of pure distilled water, tetra butyl ammonium bromide glycerol{[TBAB][Gly]}, and different concentration of aqueous bisphenol A (aq. BPA) (i.e., 25, 50, 75, and 100 ppm) were measured at different temperatures from 293.15–343.15 K. Further, densities of the pseudo binary mixtures of aq. BPA and {[TBAB][Gly]} over the entire mole fraction were measured at different temperatures from 293.15–343.15 K. From these measured density data, the solution thermodynamic properties of the pseudo binary mixtures of aq. BPA and {[TBAB][Gly]} were calculated, and the excess molar volume data were correlated using the Redlich–Kister polynomial equation. Furthermore, the σ‐profiles and σ‐potentials of all the studied species were generated and analyzied in terms of H‐bond donor and/or acceptor at atom and molecular levels. Finally, based on the results of aq. BPA with {[TBAB][Gly]}, tetra butyl ammonium bromide decanoic acid {[TBAB][DA]} and tetra butyl ammonium bromide oleic acid {[TBAB][OA]} based deep eutectic solvents were used for the removal of BPA from the aqueous stream at 298.15 K and 1 atm. This process was characterized in terms of distribution coefficient (D), extraction efficiency (η), and also thermodynamic feasibility of the process at different temperatures.

Degradation mechanisms, kinetics and eco-toxicity assessment of 2,4-Dinitrophenol by oxygen-containing free radicals in aqueous solution

2,4-Dinitrophenol (DNP) as a widely used chemical is harmful to human health. Highly active free radicals-based advanced oxidation technology (AOT) has been successfully applied to degrade DNP in wastewater. This work aims to systematically and comprehensively analyse the oxidative degradation of DNP caused by eleven different oxygen-containing free radicals (HO·, SO4 −· , H2PO4 ·, NO3 ·, , , BrO·, ClO·, HO2 ·, , and ) involved in wastewater treatment. The quantum chemical methods are used to clarify thermodynamic feasibility, favourable site, and characteristics of reactions between different oxygen-containing free radicals and DNP based on three reaction mechanisms of free radical addition, hydrogen atom abstraction, and single electron transfer. The DNP degradation initiated by H2PO4 ·/NO3 ·/HO· is relatively easy to proceed. The kinetic data of the above reactions assist the thermodynamic analysis results. Particularly, the reaction pathways of complete degradation process of HO· and DNP are proposed. The production paths of main intermediates/products detected in the experiments are determined. The total rate constant of HO· and DNP is calculated to be 1.23×108 M-1s-1. The ecotoxicity evaluation suggests most intermediates/products is decreased during degradation, and a small part of by-products are still toxic. In addition, some insights into the AOT treatment of wastewater containing DNP are provided.

Finding branched pathways in metabolic network via atom group tracking.

Finding non-standard or new metabolic pathways has important applications in metabolic engineering, synthetic biology and the analysis and reconstruction of metabolic networks. Branched metabolic pathways dominate in metabolic networks and depict a more comprehensive picture of metabolism compared to linear pathways. Although progress has been developed to find branched metabolic pathways, few efforts have been made in identifying branched metabolic pathways via atom group tracking. In this paper, we present a pathfinding method called BPFinder for finding branched metabolic pathways by atom group tracking, which aims to guide the synthetic design of metabolic pathways. BPFinder enumerates linear metabolic pathways by tracking the movements of atom groups in metabolic network and merges the linear atom group conserving pathways into branched pathways. Two merging rules based on the structure of conserved atom groups are proposed to accurately merge the branched compounds of linear pathways to identify branched pathways. Furthermore, the integrated information of compound similarity, thermodynamic feasibility and conserved atom groups is also used to rank the pathfinding results for feasible branched pathways. Experimental results show that BPFinder is more capable of recovering known branched metabolic pathways as compared to other existing methods, and is able to return biologically relevant branched pathways and discover alternative branched pathways of biochemical interest. The online server of BPFinder is available at http://114.215.129.245:8080/atomic/. The program, source code and data can be downloaded from https://github.com/hyr0771/BPFinder.

Assessing the role of mineral particles in the atmospheric photooxidation of typical carbonyl compound

Mineral particles are ubiquitous in the atmosphere and exhibit an important effect on the photooxidation of volatile organic compounds (VOCs). However, the role of mineral particles in the photochemical oxidation mechanism of VOCs remains unclear. Hence, the photooxidation reactions of acrolein (ARL) with OH radical (OH) in the presence and absence of SiO2 were investigated by theoretical approach. The gas-phase reaction without SiO2 has two distinct pathways (H-abstraction and OH-addition pathways), and carbonyl-H-abstraction is the dominant pathway. In the presence of SiO2, the reaction mechanism is changed, i.e., the dominant pathway from carbonyl-H-abstraction to OH-addition to carbonyl C-atom. The energy barrier of OH-addition to carbonyl C-atom deceases 21.33 kcal/mol when SiO2 is added. Carbonyl H-atom of ARL is occupied by SiO2 via hydrogen bond, and carbonyl C-atom is activated by SiO2. Hence, the main product changes from H-abstraction product to OH-adduct in the presence of SiO2. The OH-adduct exhibits a thermodynamic feasibility to yield HO2 radical and carboxylic acid via the subsequent reactions with O2, with implications for O3 formation and surface acidity of mineral particles.

Theoretical Engineering of Singlet Fission Kinetics in Perylene Bisimide Dimer with Chromophore Rotation.

We investigated the potential of chromophore's rotations to tune singlet fission (SF) kinetics in perylene bisimide (PBI) dimers in addition to relative horizontal displacements. The total number of 250 PBI dimers (five displacements along the long and short axis of PBI, respectively, and ten rotation angle changes from parallel to perpendicular alignment) was examined. Ground-state energies showed that dimer formation is favored in all orientations with some differences in interaction strength. Time-dependent density functional theory predicted S1 and T1 excitons' energy, and the thermodynamic feasibility of SF process was judged by the energy difference between a S1 exciton and twice of T1 excitons. In addition, we also estimated the relative rate of multiexciton generation step by the three-state kinetic model with the results of restricted active space employing double spin-flip. Nine promising orientations including two parallel PBI dimers and seven twisted ones were discussed. Wave function composition analysis showed that SF occurs mainly through the superexchange mechanism in various twisted PBI dimers, but the direct two-electron and coherent pathway could be operative at the particular positions. Quantum chemical simulations suggested the rotation as an effective tool to tune SF efficiency in PBI dimers, which is helpful to substantiate more efficient SF material.

Ammonia and borane activation by Tantalum Carbide cluster anion Ta2C4−: A theoretical approach

Activation of C–H, B–H as well N–H sigma bonds has been a subject of fundamental interest due to potential feedstock in chemical industry. The co-operative effect of the metal centers in a di-nuclear carbide cluster Ta2C4− for methane C–H activation and dissociation has recently been revealed, in which a molecule of hydrogen is evolved. Based on that, we have explored reaction pathways for ‘E−H’ sigma bond activation and dissociation processes of gaseous Ammonia (E: N) and Borane (E: B) using the stable form of the aforesaid complex at DFT levels. The geometries and energetics associated with the reactions are found to be method insensitive. The course of the reaction is initiated by a 1:1 precursor complex formed between the cluster and N (/B)H3. This complex formation is found to be more exothermic than that of its methane counterpart. In case of BH3, considerable lengthening of two B–H bonds in the first step is observed which implies that the two B–H bonds are activated simultaneously under the influence of Ta2C4−. But for NH3, N–H bond lengthening as well as activation is observed to be insignificant in this precursor complex. The chemical nature of the participating hydrogen atoms is inspected by NPA analysis (‘protic’ type in NH3 and ‘hydride’ type in BH3).The overall dehydrogenation procedures for both the molecules are found to be multi-step with high exothermicity. Highly negative net energy change in terms of Gibbs Free Energy (−31.03 kcal/mol for ammonia and −31.36 kcal/mol for borane) as well as Enthalpy (−33.68 kcal/mol for ammonia and −34.13 kcal/mol for borane), in forming a H2 molecule with stable Ta2C4N(/B)H− complex, with respect to the reactant pair govern the thermodynamic feasibility of the overall process. In a nutshell, this computational study provides a detail understanding of the activation and dissociation processes of the concerned gaseous molecules, which will be beneficial for further experimental studies.

Waste Heat Utilization for the Energy Requirements of a Post Combustion CO <sub>2</sub> Capture Retrofit Study of a Cement Manufacturing Facility

This paper presents a preliminary investigation of utilizing waste heat available from a cement manufacturing facility for carbon dioxide (CO2) capture and compression processes. The cement manufacturing facility considered in this study emits 600,000 - 750,000 tonnes of CO2 annually while producing 800,000 – 1,000,000 tonnes of clinker. Determining an alternative energy source for amine regeneration will be a major deliverable and a challenging component of this study. Previously utilized methods from the power industry do not apply in this situation since cement plants do not normally produce steam. Cement manufacturing is an energy intensive process resulting in multiple high temperature exhaust gas streams. In this study, preliminary thermodynamic investigations of the utilization of thermal energy have been performed in two gas streams including kiln flue gas and clinker cooler air exhaust. The scenarios investigated in this study include (1) direct recovery of heat using heat recovery boilers and (2) employing of duct firing to increase the temperature of the flue gas prior to heat recovery. The recovered energy can be used for the amine regeneration process. The use of duct burning subsequently produced excess heat which exceeded the energy need for amine regeneration. However, this option can be utilized to produce medium pressure steam which can then be paired with the installation of a back pressure turbine to produce electricity. The results obtained in this study focused solely on the thermodynamic feasibility and efficiency. To justify whether the proposed strategies are practical or not, several factors including CAPEX and OPEX, requirements for modifications to the existing plant, impacts on the existing cement kiln process, and complexity and reliability of the proposed heat recovery system need to be further considered.

Thermodynamic feasibility evaluation of an innovative salinity gradient solar ponds-based ORC using a zeotropic mixture as working fluid and LNG cold energy

Thermodynamic feasibility evaluation is investigated for a salinity gradient solar pond-based power generation system. A dual-pressure evaporation organic Rankine cycle using the zeotropic mixture as working fluid is employed for power generation. To increase power generation, liquefied natural gas cold energy is used as a heat sink. Furthermore, to reach reliable results, transient analysis is conducted on the overall system. Also, the solar pond walls shading effect as well as heat losses that could not be ignored (i.e., evaporation heat loss from pond surface) is considered in the simulation. The results show that for a system located in Urmia, Iran, the annual average solar pond energy efficiency for the first year is obtained 20%. Different zeotropic mixtures are examined to achieve the optimal thermal performance of the system. It is concluded that the system using R245ca/R236ea with a mass fraction of 0.6/0.4 has the optimal thermal performance among selected zeotropic mixtures. In this case, the values of the system generated power and exergy destruction are obtained 95.67 MJ year−1 m−2 and 133.7 MJ year−1 m−2, respectively, with an energy efficiency of 3.28%.

Recent advances in constraint and machine learning-based metabolic modeling by leveraging stoichiometric balances, thermodynamic feasibility and kinetic law formalisms

Understanding the governing principles behind organisms’ metabolism and growth underpins their effective deployment as bioproduction chassis. A central objective of metabolic modeling is predicting how metabolism and growth are affected by both external environmental factors and internal genotypic perturbations. The fundamental concepts of reaction stoichiometry, thermodynamics, and mass action kinetics have emerged as the foundational principles of many modeling frameworks designed to describe how and why organisms allocate resources towards both growth and bioproduction. This review focuses on the latest algorithmic advancements that have integrated these foundational principles into increasingly sophisticated quantitative frameworks.

Thermodynamic, Economic and Sustainability Analysis of Solar Organic Rankine Cycle System with Zeotropic Working Fluid Mixtures for Micro-Cogeneration in Buildings

Globally there are several viable sources of renewable, low-temperature heat (below 130 °C), particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and suitable system to generate electrical power from renewable sources based on its beneficial usage of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled through the greater matching of the temperature profiles of the WF and the heat source/sink. This paper demonstrates the thermodynamic, economic and sustainability feasibility, and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines first the thermodynamic performance of ORC systems using zeotropic mixtures to generate electricity powered by a low-temperature solar heat source for building applications. A thermodynamic model is developed with a solar-driven ORC system both with and excluding a regenerator. Twelve zeotropic mixtures with varying compositions are evaluated and compared to identify the best combinations of mixtures that can yield high performance and high efficiency in their system cycles. The study also examines the effects of the volume flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane and butane/propane are selected for parametric study to investigate the influence of operating parameters on the system’s efficiency and sustainability index. For zeotropic mixtures, results disclosed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a substantial enhancement in cycle efficiency can be obtained by a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also revealed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar ORCs. Moreover, a detailed economic with a sensitivity analysis of the solar ORC system was performed to evaluate the cost of the electricity and other economic criteria. The outcome of this investigation should be useful in the thermo-economic feasibility assessments of solar-driven ORC systems using working fluid mixtures to find the optimum operating range for maximum performance and minimum cost.

Does Underthrusting Crust Feed Magmatic Flare‐Ups in Continental Arcs?

AbstractEpisodic magmatic flare‐ups are documented in many continental arcs worldwide. Yet, the causes of such episodicity and the sources feeding the flare‐ups are not well‐understood. In this study, we use a 1‐D numerical model and scaling analysis to assess the mass balance and thermodynamic feasibility of generating arc magma as a result of partial melting of underthrusted retro‐arc lower crust. Results show the magma volumetric flux or magmatic thickening rate, is directly correlated with the crustal underthrusting rate and the relative timescales of heat transfer and underthrusting. For a continental arc with dimensions similar to the Sierra Nevada arc in California, we show with a constant underthrusting rate of 5 km/Myr, the magmatic thickening rate is 0.1–0.3 km/Myr. This is slightly below the baseline of arc magma thickening rate (∼0.3 km/Myr) from the mantle wedge and accounts for 10%–30% of the magmatic thickening rate during a flare‐up. The cumulative volume of magma generated from the partial melting of a 20‐km‐thick underthrusted lower crust is on the order of 105 km3, about 10%–40% of the estimated magma volume generated during a flare‐up. Therefore, we argue partial melting of underthrusted lower crust plays a partial or subsidiary role in driving a magmatic flare‐up event. Additional melts from the mantle and/or other crustal sources are needed to achieve the observed magmatic output during flare‐ups. The arc root developed by partial melting of the underthrusted crust reduces the time needed to obtain the critical thickness for root foundering, thus influencing the tempo of arc magmatism.

Dynamics and thermodynamics of core/shell formation of icosahedral NimAgn bimetallic nanostructures

The molecular dynamics and multiple histogram techniques were used to understand the core/shell formation of bimetallic silver-nickel nanostructures at sizes of 55 and 147 atoms. Two core/shell structures of 55 atoms icosahedra, Ag13Ni42 and Ni13Ag42 with their isomers, Ni13(Ni29Ag13) and Ag13(Ag29Ni13) were considered. In the case of 147 atoms icosahedra, homogeneous motifs (either Ag or Ni) of the core, inner shell, and outer shell were produced along with their heterogeneous isomers. Energetically, nickel-core structures are found to be more favorable than corresponding silver-core motifs. Constant volume heat capacity was used to characterize the phase transition of each cluster. The trend in the variation of melting temperatures of 55 atoms icosahedra with the nickel composition aggreses with the observed trend in the energy variation, thus values of heat capacity reveals more solid-like characteristics of NicoreAgshell motifs and liquid-like characteristic of AgcoreNishell motifs. Thermodynamic feasibility of the nickel-core/silver-shell formation was established by comparing Helmholtz free energy changes in the transition of silver atoms from the center to the shell and nickel penetration from shell to the center. The free energy changes in surface mixing and segregation of silver atoms revealed that the mixing of silver atoms with nickel atoms on the surface is more favorable than segregation. In a low nickel environment, the formation of homogeneous core/shell structures occurs, while in moderate nickel composition, mixing of silver atoms is favorable than being in the homogeneous core/shell configurations.

Discerning the thermodynamic feasibility of the spontaneous coexistence of multiple functional vegetation groups

Can the Second Law of Thermodynamics explain why ecosystems naturally organize into a complex structure composed of multiple vegetation species and functional groups? Ecosystem structure, which refers to the number and type of plant functional groups, is the result of self-organization, or the spontaneous emergence of order from random fluctuations. By considering ecosystems as open thermodynamic systems, we model and study these fluctuations of throughput signatures on short timescales to determine the drivers and characteristics of ecosystem structure. This diagnostic approach allows us to use fluxes of energy and entropy to calculate an ecosystem’s estimated work and understand the thermodynamic behavior of the system. We use a multi-layer canopy-root-soil model to calculate the energy and entropy fluxes of different scenarios for field sites across various climates. At each site, scenarios comprised of native individual plant functional groups and a coexisting multi-group composition scenario including all functional groups observed at the site are compared. Ecosystem-scale calculations demonstrate that entropy fluxes and work efficiency—the work performed for the amount of radiation entering the ecosystem—are greatest in the multi-group scenario when its leaf area is significantly larger than each of its individual functional groups. Thus, we conclude that ecosystems self-organize towards the vegetation structure with the greatest outgoing entropy flux and work efficiency, resulting in the coexistence of multiple functional groups and performing the maximum amount of work within the constraints of locally available energy, water, and nutrients.

Mechanistic Insights into the Conversion of Biorenewable Levoglucosanol to Dideoxysugars

A molecular understanding of the conversion of biorenewable threo- and erythro-levoglucosanol (LGOL) to 3,4-dideoxysugars in aqueous medium is provided based on first-principles simulations. The synthetic importance of this transformation is that these intermediates can be quantitatively hydrogenated to (S,S)/(S,R) hexane-1,2,5,6-tetrol (tetrol), whose stereochemistry depends on which dideoxy sugar intermediates are formed during LGOL conversion. The thermodynamic and kinetic feasibility of the acetal (R₂C(OR)₂) hydrolysis in LGOL is investigated via computing the free energy profile. In aqueous medium, the rate-determining step of LGOL hydrolysis is the protonation of the anhydro-bridge oxygen atom of LGOL concurrent with ring opening, yielding the cyclic forms of 3,4-dideoxymannose (DDM) and 3,4-dideoxyglucose (DDG) from threo- and erythro-LGOL, respectively. The measured activation energies of LGOL hydrolysis are 20.5 and 23.6 kcal/mol for DDM and DDG formation, respectively. These values are in agreement with the computed protonation free energies of 17.1 and 18.2 kcal/mol, respectively. Based on the simulations, a Bronsted base-catalyzed isomerization from DDG or DDM to 3,4-dideoxy fructose (DDF) is preferred with lower apparent activation free energy barriers compared to the acid-catalyzed isomerization. In summary, this study provides mechanistic information about the conversion of the biomass-derived anhydro-sugar LGOL to 3,4-dideoxy sugars, which are precursors to renewable high-value chemicals.

Thermodynamic evaluation of CCHP system based on biomass gasification by exploring the feasibility of using CO2 as gasification agent

The initial purpose of adopting combined cooling heating and power (CCHP) system is to achieve cascade utilization of fuel energy as well as stepping into low-carbon society. In this study, CO2 is used as gasification agent instead of conventional option of using steam in the biomass gasification unit for reducing CO2 emissions and increasing energy efficiency. To determine the thermodynamic feasibility during the process, exergy analysis has been performed within the whole process as well as its individual units. From the analytical results, it discloses that gasification and combustor irreversibilities yield the highest exergy destruction in the CCHP system, which account for 44.19% and 20.79% of the overall exergy destruction, respectively. Exergy analysis emphasises that both losses and irreversibilities can contribute to loss of efficiency system performance. Additionally, focusing on the influences of key parameters on system performance has been highlighted as well. The outcomes suggest that the optimum gasification temperature and CO2/C are 825 °C and 0.25 respectively. Under the optimal design parameters, the energy efficiency and PESR can reach 53.25% and 10.17% in summer respectively. In addition, a preliminary economic analysis is involved and the financial feasibility of this CCHP system is further demonstrated.

Molecular modeling study of tectoquinone and acteoside from Tectona grandis linn: a new SARS-CoV-2 main protease inhibitor against COVID-19

Coronavirus disease 2019 (COVID-19), a highly contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has drastically changed the lifestyle of people around the globe. Due to the lack of specific and effective antiviral drugs, transmission of the disease increases exponentially and makes it more serious and harder to control. Drugs that were assumed to be effective against COVID-19 have failed in various stages of clinical trials and this made the scientific community more disappointed. But, the race of researchers for developing new and effective antiviral to stop the disease progression still continues and our work is one among them. This study is an attempt to analyze the action of Tectoquinone and Acteoside; an important phytocompound, on SARS-CoV2 viral protease via in silico approach. The compounds were selected on the basis of their molecular docking values and they were subjected to molecular dynamics simulations about 50 ns to determine the stability and the thermodynamic feasibility between the target and the ligands. Binding energies like hydrogen bonding, hydrophobic and electrostatic interactions of the complexes were determined after MD simulations. The Pharmacokinetics and drug likeness evaluation of the compounds provide a strong evidence for the use of these compounds in developing drugs for clinical trials. Thus, the current study reveals the potential phytoconstituents present in Tectona grandis Linn to inhibit COVID-19 viral protease and thereby act as a lead therapeutic agent. Communicated by Ramaswamy H. Sarma

Mechanochemical leaching of Zn from low-grade smithsonite using Fe2(SO4)3 solution

Herein, the first-ever use of Fe2(SO4)3 solution as a leaching reagent to leach Zn from smithsonite under mechanical activation is reported. Thermodynamic calculations demonstrate that the leaching reaction's Gibbs free energy change is negative at ambient temperature and pressure (298.15 K, 100 kPa), implying the thermodynamic spontaneity and feasibility of the reaction. The feasibility assessment of leaching confirmed that ZnCO3 can be converted to water-soluble ZnSO4 through a near-stoichiometric reaction with Fe2(SO4)3 solution. Furthermore, X-ray diffraction analyses show that Fe3+ ions precipitate into the leaching residues in the form of an amorphous phase. Leaching experiments with low-grade smithsonite are performed to determine the leaching effect of natural smithsonite ore using Fe2(SO4)3 solution. Optimum conditions (the Fe/Zn molar ratio: 1.4, the rotational speed of the planet carrier comprising the mill: 300 rpm, the mechanochemical leaching time: 60 min, the liquid–to–solid ratio 1–10 mL·g−1) yielded a leaching efficiency of 99.6%. The proposed process provides a new simple approach for extracting Zn from carbonate-type Zn oxide ores.