Chemical Processing Routes Research Articles

Thermodynamic approach for designing processing routes of 4Mn quenching and partitioning steel

AbstractThe study addresses the design and optimization of chemical composition and processing routes of new quenching and partitioning medium-Mn alloy using theoretical and experimental approaches. The thermodynamic calculations using Thermo-Calc and JMatPro software were carried out to characterize the influence of Mn, Si and Al contents on cementite formation and precipitation processes. The evolution of individual phases as a function of temperature under thermodynamic equilibrium conditions was estimated. The investigations included the determination of continuous cooling transformation (CCT) and the time–temperature transformation (TTT) diagrams of a model 4Mn alloy. The calculated equilibrium diagrams were compared with the experimental diagrams determined using dilatometric tests. Microstructural observations were carried out to verify the results of dilatometric measurements. The results of thermodynamic calculations and experimental tests showed the moderate agreement. It is related to the inaccuracy of currently available models in the used software and/or non-equilibrium conditions of experimental tests.

Assessing the environmental risk of fire and explosion events associated with chemical process routes

The development of inherently environmentally friendly chemical process plants is one approach to reduce or avoid potential harmful environmental consequences that could occur due to chemical plant accidents. This can be achieved by selecting the chemical process route involving the least environmental risk, during preliminary design stage. To assist the route selection process a risk-based index called Inherent Environmental Risk Index for Fires and Explosions (F&E-IERI) is proposed. The F&E-IERI assesses and ranks chemical process routes considering environmental impacts caused by accidental fires and explosions that could occur in a chemical plant. This index considers the environmental impact magnitude, fire or explosion event occurrence frequency, and the environmental element vulnerability. A higher index associated with the route indicates a higher environmental risk. The proposed index has been applied in four possible routes to produce acetone. The p-diisopropyl benzene oxidation process route to produce acetone showed the lowest F&E-IERI value indicating the route having the lowest environmental risk.

Eco-geological consequences of textile processing wastes: Risk assessment, elemental dissolution kinetics, and health hazard potential

Although substantial quantities of toxic wastes are generated from textile industries, the characteristics of textile processing wastes (TPWs) have yet scantily been investigated from ecological and agricultural perspectives. Here, the eco-geological consequences of TPWs are evaluated by considering three types of sludges (i.e., silk fibre sludge (SFS), dye mixed silk processing sludge (DSPS), and cotton processing wastewater sludge (CPWS)). The predominance of certain components between different wastes (e.g., fibrous substances in silk industry wastes (i.e., SFS and DSPS) and amorphous materials in cotton processing wastes (i.e., CPWS)) is accounted for by the use of different raw materials in different industries. According to the FTIR and other characterization analyses, all three types of TPWs were rich in carbonaceous compounds and nutrients (e.g., CNPK) because of their biological origin. Further, high accumulation of toxic metals (e.g., Cd, Cr, Cu, Zn, Pb, and Mn) was apparent with chemical-processing routes. The principal component analysis indicated strong relationships between certain environmental variables (e.g., moisture content and bulk density) and bioavailability of several metals (e.g., Cd, Zn, Cu, and Mn), while C levels in TPWs were tightly associated with Cr levels. According to the Visual MINTEQ model, the dissolution-precipitation dynamics of potentially toxic elements (e.g., Pb, Cr, and Zn) in TPWs are predicted to be controlled by the levels of phosphates/chlorides/sulphates in line with the textile processing steps employed in different factories. The great toxicity potential of CPWS (e.g., relative to SFS and DSPS) is recognized to pose significant metal-induced hazards to ecosystems and human health over time. Among the three TPWs, SFS could be prescribed for agricultural application after proper treatment (e.g., via valorization techniques) with the aid of its benign nature and high nutrient (Total N: 3.83%; available P: 118.6 mg kg−1) value.

Chemical process route selection based upon potential environmental risk of chemical releases

Chemical process route selection is a key decision taken during the preliminary design stage of chemical plant development. This work presents a risk-based methodology that can be used to select the most inherently environmentally friendly chemical process route among alternate routes to produce a chemical. An index called Inherent Environmental Risk Index for Chemical Release (Chem-IERI) is proposed which represents the potential environmental risk due to a total loss of containment event in the plant. The risk index incorporates three parameters, namely the magnitude of environmental impact, the occurrence frequency of the accidental chemical release event that results in the environmental impact and the vulnerability of the environmental element where the impact is observed. Eight environmental impacts are considered and a methodology to estimate the vulnerability of environmental elements to these impacts is proposed. A higher index value indicates a higher environmental risk. The index developed was applied to assess four possible process routes to produce acetone. Propene oxidation process route showed the lowest Chem-IERI value while cumene oxidation process route showed the highest indicating the least inherent environmental friendliness.

Nanostructure formation and thermal stability of nanophase materials prepared by mechanical means

Abstract Mechanical attrition, mechanical alloying and other methods of extreme plastic deformation (high pressure torsion, equal channel angular pressing) have been developed as versatile alternatives to other physical and chemical processing routes in preparing nanophase materials. Here several examples are discussed including the deformation-induced nanophase formation in powder particles, in thin-foil sandwich structures and at the surface of alloys exposed to friction-induced wear, leading to the formation of nanocrystals and, in some cases, amorphous nanostructures. This opens exciting perspectives in preparing nanostructured materials with a number of different interface types in terms of structure (crystalline/crystalline, crystalline/amorphous) as well as atomic bond (metal/metal, metal/semiconductor, metal/ ceramic etc.). It is expected that the study of nanostructure formation by mechanical means in the future not only opens new processing routes for a variety of advanced nanophase materials but also improves the understanding of technologically relevant deformation processes on a nanoscopic level.

Recent Progress in the Synthesis of MoS2 Thin Films for Sensing, Photovoltaic and Plasmonic Applications: A Review.

In the surge of recent successes of 2D materials following the rise of graphene, molybdenum disulfide (2D-MoS2) has been attracting growing attention from both fundamental and applications viewpoints, owing to the combination of its unique nanoscale properties. For instance, the bandgap of 2D-MoS2, which changes from direct (in the bulk form) to indirect for ultrathin films (few layers), offers new prospects for various applications in optoelectronics. In this review, we present the latest scientific advances in the field of synthesis and characterization of 2D-MoS2 films while highlighting some of their applications in energy harvesting, gas sensing, and plasmonic devices. A survey of the physical and chemical processing routes of 2D-MoS2 is presented first, followed by a detailed description and listing of the most relevant characterization techniques used to study the MoS2 nanomaterial as well as theoretical simulations of its interesting optical properties. Finally, the challenges related to the synthesis of high quality and fairly controllable MoS2 thin films are discussed along with their integration into novel functional devices.

Inherent Safety and Economic Graphical Rating (InSafE) method for inherent safety and economic assessment

Incorporation of the economic aspect into the inherent safety assessment during the early design stage, especially the research and development (R&D) design stage, is currently scarce, however, there are various works which consider economic aspects at the later stage of process design. Similar economic evaluation is very hard to accomplish during the R&D design stage due to the limited amount of data available. This work introduces the Inherent Safety and Economic Graphical Rating (InSafE), a graphical inherent safety and economic evaluation for R&D design stage application. InSafE consists of gross profit and net profit margin for its economic assessment and eight inherent safety parameters taken from the GRAND method for its inherent safety assessment. Application of this method on methyl methacrylate process routes shows TBA and i-C4 routes as the safest and most profitable process routes. InSafe is also designed to be applicable for other inherent safety assessment methods for R&D design stage; for example, the Prototype Index for Inherent Safety (PIIS), the Inherent Chemical Safety Index (ICSI), and the Cumulative Index (CI). Economic evaluation during the R&D design stage enables users to compare the inherent safety level of a process route with its economic potential; hence, helping users in determining the best chemical process route in terms of inherent safety and economic potential before going to the next process design stage. If either one of these two aspects are not in accordance with the user’s preference, modifications can still be made on the process to achieve their inherent safety and economic preferences as it is still in the R&D stage of process design.

Theoretical Correlation of Elemental Distribution of Nd and Pr in Ce-Fe-B Microstructure With Hard Magnetic Properties

Relatively resource-rich but property inferior-Ce-Fe-B magnet can be improved by partial replacement of Ce by Nd and/or Pr. In addition to the amount of Nd/Pr, their distribution profile in microstructure plays an important role. From our first principles density functional theory (DFT) calculation, the substitution energy of Ce by Pr/Nd is negative in Ce <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sub> B (2:14:1) while that for laves phase, CeFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is positive, implying that Nd/Pr stabilize 2:14:1 and suppress the formation of the CeFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> phase. Micromagnetic simulation indicates that homogenized distribution of Nd/Pr improves squareness of demagnetization curve, while core (Ce-rich)-shell (Nd/Pr-rich) 2:14:1 grain structure enhances coercivity. Magnetic properties of Ce-Fe-B can be optimized by manipulating distribution profile of chemical element in microstructure based on their subtle difference in thermodynamic property, which is an effective pathway to design optimized chemical composition and processing route for high-performance magnet.

An Effective Approach of Nanoscale CaF2 Addition into ZTA Composite to Enhance Tribological Characteristics in Dry Sliding

ABSTRACT This work was carried out to establish a noble technique to enhance tribological characteristics of zirconia toughened alumina (ZTA) ceramic composite by adding 10 wt% nano CaF2 (∼50 nm) via chemical co-precipitation method. Result of the tribological tests, carried out using ball-on-disk tribo-pair in dry sliding, showed a considerable improvement in coefficient of friction up to ∼55% and the wear rate ∼35% in CaF2/ZTA composite as compared to pure ZTA composite fabricated via chemical processing route followed by hot pressing. In the later stage, a similar CaF2/ZTA ceramic composite was fabricated by traditional physical mixing process of commercial CaF2 and ZTA powders followed by hot pressing using the same parameters and the tribological performances were compared. The specimen fabricated via chemical route possessed better responses in terms of tribo-mechanical behaviors as compared to the specimen fabricated via traditional mixing. Various phases of the composites were examined by X-ray diffraction. Elemental distribution and the worn surface were characterized by energy dispersive X-ray analysis and field emission scanning electron microscopy, respectively.

Synthesis by Hydrothermal Treatment of ZnO-Based Varistors Doped with Rare Earth Oxides and Their Characterization by Impedance Spectroscopy

ZnO-based ceramic varistors have shown excellent electrical and dielectric properties due to their characteristics microstructures represented by the arrangement of their grains and grain boundaries that allow the absorption and flow of energy when subjected to an electrical surge. Their properties and characteristics depend on their chemical compositions and processing routes. Typical processing routes involve several stages of grinding and precalcination—which are time consuming processes. Because of this, this study proposes a simpler and cheaper alternative route for processing ceramic varistors. The alternative process proposed is the mixing of the precursor oxides by means of a hydrothermal treatment. The characteristics and properties of the synthesized ceramic varistors were evaluated by means of scanning electron microscopy, X-ray diffraction and impedance spectroscopy, considering the effect of the addition of rare earth oxides (La2O3, CeO2 and Nd2O3). The results showed that the mixing of the oxides through hydrothermal treatment produces ceramic varistors with characteristics and properties similar to those obtained by other processing routes. Furthermore, it was observed that the addition of rare earth oxides affects the characteristics and properties of the ceramic varistor depending on the type of rare earth oxide added, its concentration and ionic radius.

Studying the effect of adding Titanium Dioxide (TiO2) nanoparticles on the compressive strength of chemical and heat-activated acrylic denture base resins

ABSTRACT The commonly used acrylic resins for fabricating denture base suffer from poor mechanical properties. This study aimed to assess the effect of incorporating Titanium Dioxide (TiO2) nanoparticles (NPs) as a reinforcement agent on the compressive strength of different acrylic denture base materials. Thirty-two cylindrical specimens (22 mm in height and 12 mm in diameter) were prepared from PMMA resins with and without TiO2 NPs. They were allocated into two main groups according to the materials used such as cold cure and heat cure denture base resins and then divided into two subgroups each containing eight specimens: control (without nanoparticles) and experimental (with 2 wt.% TiO2 NPs). TiO2 NPs were synthesised via a chemical processing route. Particle morphology and size distribution were assessed using SEM and AFM while XRD technique was employed to determine the crystalline structure of the NPs. Compression test was performed on the specimens using a universal Instron testing machine to compare the compressive strength. Size of crystalline TiO2 NPs varied between 40 and 80 nm. The mean compressive strength for the cold cure acrylic resin (control group) and its nanocomposite (experimental group) were found to be 15.37 MPa and 17.42 MPa while for the heat cure acrylic resin and its nanocomposite were 23.04 MPa and 24.30 MPa. A statistically significant difference was recorded between the compressive strengths of cold cure acrylic resin and its nanocomposite. However, the difference was non-significant in the case of heat cure acrylic resin. The compressive strengths of both cold cure and heat cure acrylic resins increased after the incorporation TiO2 NPs.

Subjective Scaling Elimination Test for Index-based Inherent Safety Assessment Methods

The index-based inherent safety assessment method is preferable in comparing alternative chemical process routes due to its ability to be used in the early process design stage with limited details availability of the route assessed. However, the current index-based inherent safety assessment methods available have the shortcoming of subjective scaling. The Numerical Descriptive Inherent Safety Technique (NuDIST) is an inherent safety assessment method for the research and development design stage that overcomes the shortcoming of subjective scaling by incorporating logistic functions in its scoring assignment. The aim of this paper is to verify the NuDIST method in comparison with the Prototype Index for Inherent Safety (PIIS) and Inherent Safety Index (ISI) in terms of subjective scaling elimination. The inter-boundary case subjective scaling is considered solved if the scores difference between sub-edge boundaries is small while the intra-boundary case subjective scaling is considered solved if every value in a range has different scores. The results of the subjective scaling elimination test agree that NuDIST eliminates the shortcomings of subjective scaling with positive results for both inter-boundary and intra-boundary.

Biotechnological recycling of critical metals from waste printed circuit boards

AbstractCritical metals are key raw materials for new generation clean energy production. The extraction of critical metals often follows the difficult processing of primary ores and they are many times recovered as the companion metals. With the depletion of primary reserves, the focus has now shifted to processing the urban mines, like electronic (e‐)waste. Among the different types of e‐waste, the waste printed circuit boards (WPCBs) are the major reservoir of high‐value critical metals and are usually treated by the traditional pyro‐ and/or hydro‐metallurgical techniques. However, the application of microbial activities in metals recycling is rapidly emerging as a green technology in comparison to smelter or chemical processing. The application of microorganisms (bacteria/fungi) in WPCBs’ recycling is being increasingly explored in order to meet the parallel objectives of resource recovery and pollution mitigation. Therefore, the present article assesses the current frontiers in bioleaching of critical metals from WPCBs and contains discussions on process fundamentals, challenges, and perspectives. The applicability of microbial recycling of WPCBs at a higher scale in terms of a circular economy and urban mining notion, the techno‐economic analysis, and environmental sustainability in comparison to the chemical processing route are also discussed. © 2020 Society of Chemical Industry

Extraction of Rare Earth Elements from Phospho-Gypsum: Concentrate Digestion, Leaching, and Purification

Rare earth-bearing gypsum tailings from the fertilizer industry are a potential source for an economically viable and sustainable production of rare earth elements. Large quantities are generated inter alia in Catalão, Brazil, as a by-product in a fertilizer production plant. Hitherto, the gypsum has been used as soil conditioner in agriculture or was dumped. The cooperative project, “Catalão Monazite: Economical exploitation of rare earth elements from monazite-bearing secondary raw materials,” intends to extract rare earth elements from these gypsum tailings. In this paper, a chemical process route to obtain a mixed rare earth carbonate from a monazite concentrate, was investigated. The results of the digestion, leaching, and precipitation experiments are presented and discussed herein. This includes reagent choice, process parameter optimization through experimental design, mineralogical characterization of the feed material and residues, purification of the leach solution, and precipitation of the rare earth as carbonates. The results showed that a rare earth extraction of about 90% without the mobilization of key impurities is possible during a sulfuric acid digestion with two heating stages and subsequent leaching with water. In the following purification step, the remaining impurities were precipitated with ammonium solution and the rare earth elements were successfully recovered as carbonates with a mixture of ammonium solution and ammonium bicarbonate.

Evaluation of Simultaneous Saccharification and Fermentation of Oil Palm Empty Fruit Bunches for Xylitol Production

The biological process route of xylitol production from lignocellulosic materials, via enzymatic hydrolysis which is followed by fermentation, offers a more sustainable or greener process than the chemical process route. Both the enzymatic hydrolysis and the fermentation processes are conducted at moderate process condition and thus require less energy and chemicals. However, the process proceeds slower than the chemical one. In order to improve process performance, the enzymatic hydrolysis and the fermentation processes can be integrated as Simultaneous Saccharification and Fermentation (SSF) configuration. This paper discusses the evaluation of SSF configuration on xylitol production from Oil Palm Empty Fruit Bunches (OPEFB). To integrate two processes which have different optimum temperature, the performance of each process at various temperature was first evaluated. Later, SSF was evaluated at various hydrolysis and fermentation time at each optimum temperature. SSF showed better process performance than the separated hydrolysis and fermentation processes. The best result was obtained from configuration with 72 hours of prior hydrolysis followed by simultaneous hydrolysis and fermentation, giving yield of 0.08 g-xylitol/g-OPEFB.

(Invited) Primary Electrodeposition of Lithium Metal for Secondary Batteries

The secondary lithium metal system is the ultimate negative electrode given its phase, redox potential and mass. To maximize the energy density of a cell the lithium metal should be in coulombic balance with the cathode of choice, but the large scale manufacturing of thin lithium foils remains a challenge. In this presentation we will review the programmers and challenges of primary production of lithium foil directly from lithium salt and oxides, and compare the efficacy of these films to thermal and chemical processing routes.

Hydrogen embrittlement of a microalloyed bainitic forging steel

The hydrogen embrittlement (HE) of a novel microalloyed bainitic forging steel with a strength level of 1100 MPa was evaluated using electrochemical charging and slow strain rate tensile test method with notched round bar specimens. The results show that the susceptibility to HE of the as-forged bainitic forging steel is notably higher than that of the quenched and tempered (Q&T) steel at same strength level, which is ascribed primarily to the presence of a relatively high amount of large blocky martensite/austenite (M/A) constituents of the former. It was found that low-temperature tempering treatment at 200 °C could significantly alleviate the susceptibility to HE by a relative decrease of ~ 35% of the as-forged bainitic forging steel at no expense of strength and ductility, though its resistance to HE is still a little lower than that of the Q&T steel. Thus, it is suggested that efforts concerning refining of the large blocky M/A through optimizing chemical composition and processing route could help to further alleviate the susceptibility to HE of the tested bainitic forging steel.

Properties mismatching and distribution on structural steels welded joints

The paper presents results of combined, conventional and non-conventional, approach for evaluation of mechanical and technological properties of structural steel's welded joints. The selected structural steels are in the range of most common used strength level(s), as well as corresponding various chemical composition concept(s) and processing routes. A short review regarding weldability is presented based on recommendation provided in EN 1011-2, manufacturers recommendation, and own results. However, even it is a well-known fact, mismatching of properties is presented rather to provide sense of its level for particular steel grades. Moreover, the level of under-matching of weakest weld zone (coarse grained heat affected zone), provided by mean of welding thermo-cycle simulation is presented. This is due to the fact that such estimation is not possible with everyday conventional (standardized) testing. The most important design and technological properties of welded joint(s) are considered; e.g. strength, ductility, hardness, microstructure and toughness.

Preparation and characterisation of mechanically milled particles from waste alpaca fibres

In this work, a chemical free green processing route was followed to fabricate alpaca powders from waste alpaca fibres. The waste fibres were converted into powders with the average particle size of 2.5 μm without using any chemicals neither in pre-treatment nor in powder fabrication process. Despite visible morphological changes of the powder samples, Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared (FTIR) revealed no chemical change or shift in the functional groups. The crystallinity of the powdered samples decreased with the reduction of particle size in different stages of the milling process. The differential scanning calorimetry (DSC) and thermogravimetric (TGA) test results revealed that the thermal stability of the alpaca powder was almost similar to that of alpaca fibre. The air jet-milled powder showed an increase in moisture regain and moisture content by around 38% and 33% respectively than that of alpaca fibres. The results suggest that alpaca powders have a great potential to be introduced to a wide range of new applications.

Development of an Oxidation Method for Prior Austenite Grain Boundary Revelation

The prior austenite grain size is a very important quantitative parameter which has a great influence on steel final microstructure and properties. Therefore, its measurement is a useful metallographic tool. To measure the austenitic grain size, it is necessary to reveal the prior austenitic grain boundaries by applying contrast methods. The technical literature reports many limitations to achieve satisfactory results using known methods that are, generally, susceptible to steel chemical composition and processing routes. In this context, this study proposed an oxidation method to reveal the prior austenite grain boundaries in different steel grades. This method was evaluated in the samples of AISI 4340 and AISI 1030 steels. Aiming to confirm the proposed technique efficiency, a parallel and classical method, based on picric acid etching, was applied to same steels. In the suggested oxidation method, the samples were mechanically ground, polished, and then austenitized in an argon atmosphere with low oxygen partial pressure. The obtained results confirm the success of the proposed method for both studied steels.