Initial Temperature Research Articles

Preparation of Jackfruit Artocarpus Heterophyllus Seed Starch-Grafted Polyvinyl Acetate by Emulsion Polymerization

Abstract Petrochemical-based materials are depleting for the past decades and alternative methods to replace them are being studied over the years. This includes a wide range of probable applications such as adhesive industry. Starch, in its native form, possesses inadequate bond strength and viscosity. The said properties limit the possible applications of starch thus improvement should be employed. Jackfruit seed (JFS) starch is a viable substitute for other starches that is commonly used in the industry. This research developed a starch grafted polyvinyl acetate formula that can be used as an alternative to non-renewable and food consumable resources. Parameters such as monomer/starch ratio, temperature, and amount of initiator were observed and how it affected the graft percent, shear strength, and viscosity of the samples. This process was conducted via emulsion polymerization using PPS as initiator and SDS as emulsifier, Ethanol was also utilized to wash away homopolymers. Each run was done under ambient conditions. The samples were triplicated in the software to ensure the data credibility. From the statistical analysis, it was concluded that all three parameters which are temperature, monomer/starch ratio, and initiator amount were all significant. The appearance of 1735 cm−1 band in FTIR spectrum of the grafted starch and the visible roughness in the spherical-shaped granules in SEM photographs indicated that the VAc has been successfully grafted onto jackfruit starch. DSC analysis showed that Tg of starch-g PVAc was shifted to a little higher value as compared to Tg of native jackfruit starch which suggests that material can be used in a wider temperature range.

Shock-induced nanoscale pore collapse and hotspot in cyclotetramethylene tetranitramine (HMX)

Pore collapse induced hotspot formation is a key mechanism for initiating detonation of shocked high explosives. Accurate continuum models that faithfully capture the pore collapse dynamics and resulting hotspot temperatures for multiscale initiation of high explosive are still lacking. Here, an atomistically informed dislocation plasticity model is developed for cyclotetramethylene tetranitramine (HMX), which includes nonlinear thermoelasticity, pressure-dependent and temperature-dependent dislocation motion and homogeneous dislocation nucleation, and new melting criteria. Nanoscale pore collapse simulations based on the proposed model could well reproduce the pore collapse transition from a strength-dominated regime to a hydrodynamic regime observed in molecular dynamics results. During the pore collapse transition, dislocation motion and dislocation generation induced plasticity is decoupled and evaluated. It indicates that the homogeneous dislocation nucleation suppresses the dislocation motion. Through linkage analysis of dislocation physical quantity histories of tracer particles, this work clarifies the interplay between physical dependences and dislocation mechanisms on pore collapse behaviors for the first time. The results reveal that the transition of pore collapse regime emerges from the strong pressure-dependent homogeneous dislocation nucleation. In addition, the pore collapse responses and energy localizations of the proposed model are further compared with different strength models to prove the importance of pressure dependence and homogeneous dislocation nucleation on pore collapse behaviors. Based on the simulations of pore collapse, the potential heat sources are quantified to provide a physical understanding of hotspot formation mechanisms. The present work demonstrates a key step in multiscale modeling of high explosive initiation in that atomistic simulation results are directly used to guide and refine the mesoscale model of energetic crystal used in the continuum.

Enhancing Energy Efficiency of Cumene Production Through Reactor Output Recycling Modification in a Heat Exchanger

Cumene production generally involves irreversible and exothermic reactions that leads to an increase in product temperature and needs to be cooled for further processes. The high temperature of reactor product can be utilized as a heat transfer fluid in heat exchanger. This modification process is essential for improving energy efficiency by recycling the reactor output with high temperature as a heat transfer fluid, so that the implementation of replacing the heater with a heat exchanger can be carried out for the process of increasing the initial feed temperature. In an effort to enhance energy efficiency in the cumene production process, simulations were conducted using HYSYS and the comparison of energy efficiency for both basic and modified processes can be evidenced by comparing the total amount of energy required during the process. The results shows that the total amount of energy required for the modified process is 39,814,003.7 kJ/h, while for the basic process is 40,588,937.4 kJ/h, with a difference of 774,933.7299 kJ/h. Since the total amount of energy required in the modified process is smaller than the basic process, then the modification process will increase the energy efficiency of cumene production. Copyright © 2024 by Authors, Published by Universitas Diponegoro and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Temperature control of sulfonation reaction in a semi-batch reactor

ABSTRACT Due to the basic dynamic nature of a batch or semi-batch reactor, during operation, the control duty may be altogether a set point tracking problem rather than a regulatory task with a fixed set point. In addition to that in a large number of exothermic reactor control, usually the reaction mass has to be raised to a higher temperature for initiation, and after the reaction sets in large amount of heat has to be extracted, so that the control system have the capabilities to heat as well as to cool the reaction mixture (like LAB Sulfonation). This may be done by manipulating the ratio of hot and cold streams of heat transfer fluids to make a mixed stream to be used as the heat transfer medium by using two 2-way control valves, and heating and cooling loads are splitted between them. The choice of this reactor type has been made on the basis of that the target system of our study is Sulfonation of Linear Alkyl Benzene (LAB) to synthesize the product, Linear Alkyl Benzene Sulfonic Acid (LABSA) which is the active species for manufacturing of domestic or industrial detergents. The reaction is essentially carried in semi-batch jacketed reactor.

Adsorptive Sequestration of Methylene Blue Dye from Aqueous Solution Using Novel Roystonea regia fruit Pericarp: Isotherm, Kinetics, and Thermodynamics

The batch adsorptive sequestration of methylene blue from an aqueous solution using unripe Roystonea regia fruit pericarp biomass was investigated in this study. The characteristic nature of the biosorbent was studied using various analytical instruments including Fourier Transform Infra-red spectrophotometer, Scanning Electron Microscope, Energy Dispersive X-ray, X-ray diffractometer, and the Brunauer-Emmett Teller. The adsorption study was perfomed at different experimental conditions including pH, contact time, initial dye concentration, temperature, agitation speed, and biosobent dose. From the results of this study, the optimum biosorption of MB was achieved at 120 min contact time, pH 10, room temperature (298 K), 150 rpm agitation speed and dosage of 100 mg/150 mL dye solution. With 132.30 mgg-1 maximum sorption capacity, the Langmuir isotherm best describes the biosorption equilibrium data. At all initial concentrations, the biosorption kinetics of methylene blue onto the biosorbent fitted best to the pseudo-second order kinetics model, with R2 values ≥ 0.999 and qcal being similar to the qexp. The kinetics study also showed the involvement of intra-particle diffusion in the rate-determining step; although not as the sole limiting step of the sorption process. The results of the thermodynamics study showed the high feasibility, spontaneity, and exothermic nature of the biosorption of methylene blue onto the biosorbent. This study concludes that Roystnea regia fruit pericarp would make an economically viable and renewable biosorbent for practical eco-friendly sequestration of MB dye from wastewaters.

Effects of an Annular Baffle on Heat Transfer to an Immersed Coil Heat Exchanger in Thermally Stratified Tanks

Abstract The effect of a cylindrical baffle on heat transfer to an immersed heat exchanger is investigated in initially thermally stratified tanks. The heat exchanger is located in the annular region created by the baffle and the tank wall. Three different cases of initial thermal stratification are explored, and in each case, experiments are conducted with and without the baffle in the stratified tank and in a comparable isothermal tank with the same initial energy, enabling exploration of the role of the baffle in a stratified tank and the role of stratification in tanks with or without the baffle. The baffle maintains the high initial temperature of the upper zone of the stratified tank for 10–16 min, as cool plumes that form on the heat exchanger are confined to the annular baffle region until they exit at the bottom of the tank. Regardless of stratification, the baffle always improves heat transfer to the immersed heat exchanger. In the isothermal tanks, the baffle increases total energy extracted in the first 30 min of discharge by over 20%. In stratified tanks, the baffle increases total energy extracted in 30 min of discharge by 9–16%. Initially, improvement in heat transfer in stratified tanks is due to the higher driving temperature differences around the heat exchanger. Later, after all the water from the hot zone has entered and flowed through the baffle, the tank is basically isothermal, and velocity increases as the fluid temperature drops, maintaining rates of heat transfer higher than that in the tank without the baffle. Stratification improves heat transfer in tanks without a baffle because, by design, the driving temperature difference between the heat exchanger wall and the surrounding fluid is considerably higher. However, in tanks with the baffle, stratification has only a modest positive effect on heat transfer to the immersed heat exchanger.

Investigation and Optimization of Biosorbent Capacities of Some Plants Used in Daily Life

In this study, sage, chamomile, and tarragon leaves, which are used as spices and consumed as beverages in daily life, were considered as different biosorbents that can be used in water purification by biosorption. At the same time, the effects of the parameters of initial dye concentration (10-200 mg/L), temperature (20-50 ⁰C) and contact time (0-120 min) on biosorption capacity were investigated. The biosorption processes were found to follow Freundlich isotherm and pseudo-second order (PSO) reaction kinetics. In the study, the process was also modeled using multi-tree evolutionary computation based automatic programming (AP) methods. The methods used initial dye concentration, temperature, and contact time as variables. According to the simulation results, these methods obtained nonlinear mathematical models of the processes with R^2 values as high as 0.99 for each biosorbent. By providing the most accurate models to accurately predict biosorption capacity, this study will make a significant contribution to the field of water treatment using experimental and AP methods.

Electron-irradiation induced unconventional phase transition of β-Ga2O3 epitaxial single-crystal thin film observed by in-situ TEM

In this work, the phase transition process of β-Ga2O3 thin films under heating and (or) electron irradiation condition was investigated by in-situ transmission electron microscopy. It is found that only under the high temperature, β-Ga2O3 did not undergo phase transition even when the temperature was up to 1000 °C. When under electron irradiation condition, the unconventional phase transition from β-Ga2O3 to δ-Ga2O3 occurred with a slow rate. When electron irradiation was coupled with a thermal field, the initial temperature of phase transition decreased, and the speed of phase transition also greatly accelerated. The new phase maintains crystallography relationship with the β-Ga2O3 parent phase as following: [010]β//[011‾]δ, (200)β//(2‾11)δ, and (402‾)β//(411)δ. The results reveal that electron irradiation can trigger the phase transition process from β-Ga2O3 to δ-Ga2O3, and the high temperature obviously accelerates the rate of phase transition process.

Influence of temperature and cumulative strain on microstructure and mechanical properties of multi-directional forged Mg-Gd-Y-Zn-Zr alloy

The multidirectional forging (MDF) experiments of Mg-Gd-Y-Zn-Zr alloy were performed. The effects of temperature and cumulative strain on microstructure and mechanical properties of multi-directional forged Mg-Gd-Y-Zn-Zr alloy were studied. The results showed that the recrystallization ratio of the alloy gradually increased with the initial forging temperature after 3 passes of MDF. Under the condition of the initial forging temperature of 500 °C, the grain size was gradually refined with increasing MDF passes, and the average grain size was refined to 1.49 μm after 12 MDF passes. With the increase in MDF passes, the maximum texture density of the alloy gradually decreased. The mechanical properties gradually increased with the MDF passes. In the first 6 MDF passes, the mechanical properties greatly increased, but after that, the increase gradually slowed down with additional MDF passes. The optimal mechanical properties were obtained after 12 MDF passes, and the tensile strength, yield strength, and elongation after fracture were 362 MPa, 294 MPa, and 14.5%, respectively.

Removal of Methyl Violet 2B and Direct Black 22 from Single and Binary System Using a Magnetic Zeolite/MgO/Starch/Fe3O4 Nanocomposite

This study focuses on the preparation and characterization of magnetic zeolite (FSM-Zeo) using starch, magnesium oxide, and Fe3O4. Various analyses, including BET, FTIR, SEM, EDS, XRD, Zeta potential, and VSM, were conducted to assess the properties of FSM-Zeo. The adsorption capacity of FSM-Zeo was investigated for methyl violet (MV-2B) and direct black 22 (DB-22) in both single and binary dye solutions. Key parameters such as adsorbent amount, initial dye concentration, contact time, temperature, initial pH, and ionic strength were examined in the single system. Kinetic and isotherm studies revealed that DB-22 and MV-2B adsorption followed the pseudo-second-order model. Moreover, Freundlich and Langmuir models were confirmed for MV-2B and DB-22 adsorption on FSM-Zeo, respectively. In the binary system, the presence of MV-2B enhanced the adsorption of DB-22, resulting in higher removal compared to the single dye solution. A synergistic effect was observed due to the interaction between DB-22 and MV-2B, promoting the adsorption of DB-22 on FSM-Zeo.

Microwave promoted graft copolymerization of poly(ethylacrylate) onto k-carrageenan for removal of Cd and Ni from aqueous solution

Microwave promoted graft copolymerization of poly (ethyl acrylate) onto kappa-carrageenan in presence of a redox pair (ascorbic acid and potassium persulfate) led to the formation of a novel copolymer hydrogel, kappa-carrageenan-graft-poly (ethylacrylate). By varying the reaction conditions such as the microwave power, reaction time, concentration of kappa-carrageenan, ascorbic acid and persulfate, copolymers of highest percentage grafting was obtained and characterized by FT-IR, SEM, TGA and XRD. The copolymer was evaluated as an adsorbent for the adsorption of Ni(II) and Cd(II). Various adsorption parameters such as contact time, pH, initial metal ion concentration, temperature, electrolyte strength and adsorbent dosage were varied to obtain the optimum conditions for the adsorption. The adsorption data for Cd(II), fitted better for Langmuir and Ni(II), fitted much better for Freundlich adsorption isotherm model. Maximum adsorption obtained for cadmium ions and nickel ions was 308.6 mg/g-1 and 305.8 mg/g-1 respectively. The adsorption of both metal ions followed pseudo second order kinetic model. The positive ΔH values endorsed the adsorption process to be endothermic in nature. The negative values of ΔG indicate the spontaneity of the adsorption process while the positive ΔS values showed that the adsorption of metal ions proceeded with increased randomness at the surface of the copolymer. High recovery percentage of the metal ions from the adsorbent indicates that the copolymer can be used for more adsorption cycles.

Efficient removal of Rhodamine B dye using biochar as an adsorbent: Study the performance, kinetics, thermodynamics, adsorption isotherms and its reusability

Removal of toxic dyes such as Rhodamine B is essential as it pollutes aqueous and soil streams as well. This comprehensive study explores the potential of Calophyllum inophyllum seed char as an efficient bio-adsorbent based on their characteristic properties and a comparative study between various carbon-based adsorbents on the adsorption capacity of Rhodamine B dye. In this study, the char was prepared from Calophyllum inophyllum seed using a slow pyrolysis process (298 K/min) at an optimum temperature of 823 K and used as an adsorbent for the removal of Rhodamine B from water. The resulting char was mesoporous and had 155.389 m2/g surface areas (BET) and 0.628 cc/g pore volume. The formation of pores was observed from the SEM analysis. The adsorption studies were tested and optimized through various parameters such as solution pH, adsorbent dosage, initial dye concentration, stirring speed, contact time, and solution temperature. Maximum 95.5 % removal of Rhodamine B was possible at the pH: 2, stirring speed: 100 rpm, time: 25 min, temperature 308 K, and dose: 1.2 g/L. The highest adsorption capacity at equilibrium was determined to be 169.5 (mg/g) through Langmuir adsorption isotherm studies and followed pseudo 2nd order kinetics. The thermodynamics study confirmed the adsorption processes were spontaneous (ΔG°=−0.735 kJ/mol) and endothermic (ΔH° = 4.1 kJ/mol) processes. The reusability study confirmed that the mesoporous char can be reused as an efficient adsorbent for up to 3 cycles for environmental remediation.

Multiple Heat Recovery System for an Industrial Thermal Peeling Press Machine—Experimental Study with Energy and Economic Analyses

The enhancement of energy systems in industrial zones is attracting the attention of researchers from all over the world. At the same time, optimization and advancement in heat recovery systems are now generating major interest in the energy sector. In this context, the present study suggests a new multiple heat recovery system should be applied to an industrial thermal peeling press machine. The new system consists of multiple sources of energy: the heat excess in the chimney, the exhaust gas of the chimney, and the exhaust gas of the boiler. To proceed with testing the potential of the suggested system, a hydraulic thermal peel press machine in the wood industry undergoes different tests to achieve the best configuration that will enable this machine to reach its operational temperature when heating. Five test configurations are proposed, designed, and applied experimentally on this machine. Many parameters were effective during the experimental tests, such as water flow rate, ambient air temperature, and initial water temperature. It was found that the application of the multiple heat recovery system increases the rate of heating from around 7 °C/min to around 13 °C/min. In terms of energy and economy, the “chimney + boiler only” configuration proved to be the best system to apply during the fall and winter seasons.

Laminar flame speed measurement and combustion mechanism optimization of methanol–air mixtures

AbstractLaminar flame speeds of methanol/air mixtures at 338–398 K are measured by the heat flux method, extending the range of equivalence ratio up to 2.1. And a new optimized methanol mechanism with 94 reactions is proposed by using the particle swarm algorithm, adjusting 20 Arrhenius pre‐exponential factors in their uncertainty domains. The optimized model is compared with eight methanol combustion mechanisms and experimental data published in recent years, covering a wide range of initial temperatures (298–1537 K), pressures (0.04–50 atm) and equivalence ratios (0.5–2.1). The results show that the optimized mechanism not only improves the accuracy of ignition delay time with rapid compression machine at low temperature but also moderately improve the description of laminar flame speed in lean and stoichiometric conditions. Meanwhile, the optimized model significantly enhances the prediction accuracy of CH3 and CH2O radical, and perfectly captures the evolution trend of HCO radical in laminar flat flame. Overall, the optimized mechanism provides the best overall description of the currently available measurements, leading to more accurate and comprehensive prediction of ignition delay time, laminar flame speed and species concentration.

Rapid millisecond heating via ferromagnetic resonance in MnFe2O4 nanoparticles

This study undertakes an exhaustive analysis of rapid heat generation in MnFe2O4 nanoparticles through ferromagnetic resonance within an ultra-fast timeframe of 1 ms. Real-time monitoring of temperature during single-field-pulse excitations provided detailed insights into the temperature rise profiles. By integrating micromagnetic simulations with analytical modeling—taking into account both convective and radiative losses—we have deepened our understanding of the heat transfer dynamics at play. Adjusting the analytical model to align with experimental temperature profiles enabled us to determine the efficiency of converting spin dissipation energy into heat, which stands at 17%. This figure reflects not only the surface area of the nanoparticles but also includes considerations for radiative and convective losses. Notably, employing a low AC-field strength of 17.6 Oe facilitated a rapid temperature increase of up to 90 K in just 0.5 s, showcasing a peak initial temperature rise rate of approximately 680 K/s. This research advances the frontiers of high-power heat generation driven by spin dynamics and provides a comprehensive exploration of heat transfer mechanisms over exceptionally short pulse durations. These findings could revolutionize precise and rapid temperature management at the nanoscale, unlocking prospects in bio applications, accelerated material processing, and inducing color and phase shifts in polymer matrices.

A novel approach for facile synthesis of cost-optimal catalyst for high-performance lithium-air battery

We have developed a novel and efficient cathode for advanced lithium-air batteries by employing a new approach and facile strategy. In this method, we prepared core-shell structured ZIF-8@ZIF-67 crystals with epitaxial growth using a hydrothermal technique. By subjecting these crystals to carbonization at a temperature 200 °C higher than the degradation initiation temperature (i.e. 600 °C according to thermogravimetric results), we successfully obtained functionalized nanoporous hybrid carbon materials. These hybrid carbon materials consist of hierarchical nitrogen-doped carbon @ cobalt anchored/nitrogen doped carbon (NC@CNC), where the nitrogen-doped carbon (NC) serves as the core and the cobalt anchored/nitrogen doped carbon (CNC) forms the shell. It is worth noting that electrochemical characterization data strongly support the superior performance of this nanoporous hybrid carbon material. It combines the advantageous properties of individual mesopores of nitrogen-doped carbon and the catalytic activity of cobalt‑nitrogen doped carbon. In particular, the cathode material, i.e. NC@CNC, exhibits a remarkable specific capacitance of 10,000 mAh·g−1, as calculated from the galvanostatic charge-discharge curves obtained at a current density of 50 mA·g−1. This impressive performance highlights the potential of our developed material in enhancing the efficiency and overall performance of lithium-air batteries.

Numerical Simulation of the Hydrogen-Based Directly Reduced Iron Melting Process

In the context of carbon reduction and emission reduction, the new process of electric arc furnace (EAF) steelmaking based on direct hydrogen reduction is an important potential method for the green and sustainable development of the steel industry. Within an electric furnace for the hydrogen-based direct reduction of iron, after hydrogen-based directly reduced iron (HDRI) is produced through a shaft furnace, HDRI is melted or smelted in an EAF to form final products such as high-purity iron or high-end special steel. As smelting proceeds in the electric furnace, it is easy for pieces of HDRI to bond to each other and become larger pieces; they may even form an “iceberg”, and this phenomenon may then worsen the smelting working conditions. Therefore, the melting of HDRI is the key to affecting the smelting cycle and energy consumption of EAFs. In this study, based on the basic characteristics of HDRI, we established an HDRI melting model using COMSOL Multiphysics 6.0 and studied the HDRI melting process, utilizing pellets with a radius of 8 mm. The results of our simulation show that the HDRI melting process can be divided into three different stages: generating a solidified steel layer, melting the solidified steel layer, and melting HDRI bodies. Moreover, multiple HDRI processes are prone to bonding in the melting process. Increasing the spacing between pieces of HDRI and increasing the preheating temperature used on the HDRI can effectively reduce the aforementioned bonding phenomenon. When the melting pool temperature is 1873 K, increasing the spacing of HDRI to 10 mm and increasing the initial HDRI temperature to 973 K was shown to effectively reduce or eliminate the bonding phenomenon among pieces of HDRI. In addition, with the increase in the melting pool temperature, the time required for melting within the three stages of the HDRI melting process shortened, and the melting speed was accelerated. With the increase in the temperature used to preheat the HDRI, the duration of the solidified steel layer’s existence was also shortened, but this had no significant impact on the time required for the complete melting of HDRI. This study provides a theoretical basis for the optimization of the HDRI process within EAFs.

Manipulation of Bowl-Shaped Nanoparticles Self-Assembled from a Bipyridine Pendant Containing Homopolymer.

The morphological control and transformation of soft nanomaterials are critical for their physical and chemical properties, which can be achieved by dynamically regulating the hydrophilicity of amphiphilic polymers during self-assembly. Herein, an amphiphilic homopolymer poly(N-(2,2'-bipyridine)-4-acrylamide) (PBPyAA) with bipyridine pendants is synthesized, and the effect of various parameters including initial concentration, temperature, pH, and metal ion coordination on the self-assembly behavior and morphology of the assemblies is investigated. Upon changing the initial concentration of PBPyAA, bowl-shaped nanoparticles (BNPs) with precisely controlled diameter, opening size, and thickness are obtained. With the decrease of pH of the solution, the negatively charged surface of BNPs transforms to a positively charged state. Furthermore, the addition of divalent metal ions (Co2+, Mn2+, and Zn2+) induces the transformation of BNPs to vesicles and giant vesicles. The effect of the above factors on the morphology of the assemblies is essential to change the hydrophilicity of PBPyAA dynamically, leading to variation of the local viscosity during self-assembly. Overall, manipulation of the structural parameters of BNPs and transformation of BNPs to vesicles are achieved, providing fresh insights for the precise control of the morphologies of soft nanomaterials.

Effect of Fluoroalcohol Chain Extension Modified HTPB Binder on the Combustion Performance of Aluminized Propellants

To enhance both the mechanical properties of hydroxyl-terminated polybutadiene (HTPB) binder and the combustion efficiency of aluminized propellants, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (OFHD) was employed as a chain extender to impart mechanical regulation to the HTPB binder. Mechanical testing showed that the mechanical properties of fluoride-modified HTPB polyurethane (FPU) were significantly improved: the peak tensile strength of the optimized samples reached 1.99 MPa, and the elongation at break attained 486%. The structural characterization of the FPUs was conducted using Fourier transform infrared (FTIR) spectroscopy. Thermogravimetry-mass spectrometer (TG-MS) analysis revealed that the initial thermal decomposition temperature of the FPU shifted from 170 °C to 162 °C, accompanied by the release of fluorine-containing fragments during decomposition. Analysis of the combustion residue indicated that the addition of OFHD can reduce the agglomeration of aluminum (Al) powder in aluminized propellants. Dynamic pressure characteristics results showed an augmented pressurization rate under argon and oxygen atmospheres, increased by 18.67% and 37.29%, respectively. Heat release tests indicated that the aluminized propellants with the addition of OFHD had a higher combustion heat, being increased by 6.57%. The binder system is expected to be applied in aluminized propellants to improve the mechanical properties and combustion efficiency of Al powder.

Amino-Functionalized Lotus Stem Hydrochar for Rapid Adsorption and In Situ Detoxification of Cr(VI) from Water.

The development of low-cost, efficient, and environmentally friendly adsorbents is the key to highly toxic hexavalent chromium [Cr(VI)] removal by adsorption. In this paper, amino-functionalized lotus stem hydrochar (ALSHC) was prepared from an agricultural waste lotus stem (LS) for the adsorption removal of Cr(VI) from water. The effects of the initial Cr(VI) concentration, contact time, temperature, coexisting anions, and reusability of ALSHC on Cr(VI) removal were examined in detail. The adsorption mechanism was further discussed by investigating the impact of the solution's initial pH, the relation between the pH change in solution and Cr(VI) removal during the process, the changes of chromium (Cr) species in solution and on ALSHC during adsorption, and the XPS characterization. The results demonstrated that ALSHC effectively removed Cr(VI) from water with rapid adsorption (the removal rate reached 80.90% in only 10 min) and in situ detoxification. Most importantly, ALSHC still had better adsorption performance (adsorption capacity of 30.95 mg g-1) than commercially activated carbon, even at pH = 9.00. The adsorption of Cr(VI) by ALSHC accorded with the pseudo-second-order kinetic model and Langmuir isotherm model, indicating a monolayer chemisorption process. The adsorption process was shown to be spontaneous and endothermic based on the thermodynamic characteristics (ΔG0 < 0, ΔH0 > 0, and ΔS0 > 0). The mechanism of Cr(VI) removal was mainly composed of three parts in sequence: Firstly, Cr(VI) in solution was quickly adsorbed onto ALSHC with protonated -NH2 through electrostatic attraction; subsequently, the adsorbed Cr(VI) on ALSHC was mostly detoxicated by in situ reduction; and finally, the reduced Cr(III) and the remaining Cr(VI) were fixed on the ALSHC surface by complexation. The prepared ALSHC displayed a certain superiority in Cr(VI) adsorption and had the prospect of further development.