Step In Recycling Research Articles

Evaluation of the Mechanical and Thermal Properties Decay of PHBV/Sisal and PLA/Sisal Biocomposites at Different Recycle Steps.

The recyclability of polylactide acid (PLA) and poly (3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV)-based biocomposites (10%, 20% and 30% by weight of sisal natural fibre) was evaluated in this work. The mechanical and thermal properties were initially determined and were shown to be similar to commodity plastics, such as polyethylene or polypropylene. Three recycle steps were carried out and the mechanical and thermal properties of recycled samples were evaluated and compared to the reference samples. The tensile modulus increased for recycled PLA biocomposites, whereas it was hardly influenced by recycling the PHBV biocomposites. The tensile strength and deformation at the break decreased notably after the first cycle in all cases. Although all the biocomposites became more brittle with recycling, the properties were conserved along until the third cycle, proving their promising recyclability. From the data obtained from the dynamic mechanical analysis, a slight decrease of the storage modulus of PHBV was observed, whereas PLA showed a significant decay of its properties at the 3rd recyclate. The PLA specimens were filled with sisal fibres until they reached 20%wt, which seemed also less subject to the embrittlement occurring along the recycling phase. The characteristic temperatures (glass transition-Tg, crystallization-Tc, melting-Tm) of all the biocomposites were not highly affected by recycling. Only a slight decrease on the melting point of the recycled PHBV was observed suggesting an overall good reprocessability. Moreover, the processing conditions lied in the same range as the conventional plastics which would facilitate potential joint valorization techniques.

Disassembly Line Balancing Optimization Method for High Efficiency and Low Carbon Emission

Disassembly is the first step in product recycling and remanufacturing. When disassembling large quantities of products, the disassembly efficiency is crucial for enterprises. Thus, disassembly line is the best choice for automated disassembly of disposal products. Disassembling products, especially complex structure of products, consume a lot of resources and energy and produce large amounts of carbon emissions. So, it is essential for disassembly line to work efficiently and environmentally. In this paper, the hybrid graph is proposed to express the direct and indirect constraint relationship among components. Then, the mathematical model of carbon emission is built by quantifying the carbon emissions in the process of product disassembly. Taking into account the basic disassembly time, direction change time and tool change time, the mathematical model of high efficiency is presented for optimizing disassembly time. Additionally, based on the traditional multi-objective disassembly line balancing problem (DLBP), a novel multi-objective optimization model of the DLBP with shortest disassembly time and minimum carbon emissions is proposed for improving disassembly efficiency and reducing the carbon emissions in the process of disassembly. Furthermore, genetic algorithm is presented for optimizing the disassembly sequence. Finally, an automobile engine is given as an example to confirm the practicality of the proposed model in solving the DLBP.

Evaluation of recycle pathways for out-of-specification uranium microspheres from the internal gelation process

During the production of uranium oxide microspheres with carbon using internal gelation, a small fraction of microspheres will not meet the required size or sphericity specification. The uranium microspheres with carbon can be rejected after they have been air-dried or converted into uranium carbide and uranium oxide (UCO) kernels. The next step for the rejected spheres was an air oxidation for carbon removal. The air-dried spheres became triuranium octoxide (U3O8) spheres, which were sometimes ground into powder. The UCO kernels became U3O8 powder during the air oxidation. The next recycle step was nitric acid dissolution of the U3O8 spheres or powders to produce acid-deficient uranyl nitrate (ADUN) solutions, which were used to make new uranium oxide microspheres with carbon and subsequently UCO kernels. The kinetics of the acid dissolution process were compared, and the impurity levels in the different ADUN solutions were determined. X-ray diffraction results for the UCO kernels from the initial and recycled ADUN solutions indicate that changes in the impurity levels can impact the uranium carbide to uranium dicarbide ratio in the UCO kernels.

Improved Biocatalytic Activity of the Debaryomyces Species in Seawater

AbstractBiocatalysis is an environmentally friendly strategy widely used in the chemical and pharmaceutical industries. One of its approaches consists in utilizing whole cells, which usually involves the consumption of large quantities of water. Oceans cover a large part of the Earth's surface, and constitute an important reservoir that can be used as an alternative to freshwater in chemical reactors. This work analyzed the behavior of several yeast halotolerant species belonging to genera Debaryomyces and Schwanniomyces in both freshwater and seawater. It concluded that these microorganisms were more resistant to organic solvents/compounds in the second medium. Their metabolic activity was also greater, which made the reduction reaction of several prochiral ketones more effective. Besides, yeasts cells displayed better performance in subsequent recycling steps, which could help reduce the costs of the process.

Magnetic Seed-Assisted Iron Recovery from the Reductive Leaching Solution in Hydrometallurgical Process

The recovery of iron is the key step for zinc recycling by electrolysis in zinc hydrometallurgy industry. Iron exists mainly as ferrites in the zinc neutral leaching residue and is difficult to decompose. In this paper, the reductive leaching process using sulfur dioxide was adopted to replace the traditional hot-acid leaching method, and the magnetic seed-assisted iron precipitation was developed. Under the optimum reductive leaching conditions, the initial concentration of sulfuric acid, the temperature and the partial pressure were determined as: 80 g/L H2SO4, 90 °C, 200 kPa at the fixed liquid/solid ratio of 10:1 and the stirring speed of 400 rpm. The most suitable iron precipitation reaction conditions were as follows: the pH: 3.0–3.5; the temperature: 95 °C. The recovery of iron mainly depended on the oxydrolysis of the ferrous. The ferrous precipitated as goethite and its crystallinity noticeably decreased with decreasing pH. The addition of the magnetic seeds shortened the reaction time from 4.5 to 3.0 h when the iron precipitation rate reached more than 99%. Simultaneously, the loss rates of zinc and cadmium in the iron process were also reduced from 10.96% and 9.27% to 4.23% and 3.73%, respectively. Besides, the sedimentation and filtration performance were greatly improved after the addition of magnetic seeds. The adsorption and inclusion were the main reasons for better sedimentation and filtration performance and higher metal loss rate.

Depolymerization of End‐of‐Life Poly(bisphenol A carbonate) via Alkali‐Metal‐Halide‐Catalyzed Methanolysis

AbstractChemical recycling, composed of depolymerization and polymerization, of end‐of‐life polymers (plastics) can contribute to a sustainable and resource‐conserving society. In this respect, we have installed a straightforward procedure for the first step (depolymerization) of the chemical recycling of end‐of‐life poly(bisphenol A carbonate). Operating with a combination of methanol and catalytic amounts of potassium fluoride end‐of‐life poly(bisphenol A carbonate) was depolymerized to the building blocks bisphenol A and dimethyl carbonate. With the assistance of microwave heating, an excellent rate of depolymerization (>99%) was observed within short reaction times (5 min) and turnover frequencies up to ∼1844 h−1 were realized. Noteworthly, bisphenol A and dimethyl carbonate could be applied as monomers for new poly(bisphenol A carbonate), therefore a closed cycle for poly(bisphenol A carbonate) is feasible.

A Study on the Plant Litter Decomposition Using Mycoflora for Sustainable Environment

Most of the agricultural, forest and field crop litters are consisting lignocelluloses, cellulose, hemicellulose and lignin. Among these cellulose is most predominant constituent followed by hemicellulose and lignin. The lignin together with the hemicellulose, encrust the cellulose chains forming a barrier which prevents wetting and access of cellulose-degrading enzymes therefore, the decomposition of litters can be achieved by breaking this association at first. The biodegradation of lignin of field crop litters representing a key step for carbon recycling in land ecosystem, as well as for industrial utilization of plant biomass, humification of dead organic matter by the application of certain bacterial and fungal species. The present study revealed the process of decomposition of plant litters. The fungal species colonized different types of plant litters on the basis of enzymatic activities and resource specificity. The mixtures of microorganisms could degrade lignocellulosic materials of wheat stubbles more efficiently than any individual species; Aspergillus niger, Aspergillus flavus, Aspergillus terreus, Fuserium equiseti, Trichoderma lignorum and Stachybotrys atra. A mixture of fungi and Streptomyces caused 48.0% decomposition while decomposition by an individual species viz. Aspergillus flavus was 36.90% only. It was found that, fungi have better abilities to decompose wheat straw than bacteria and actinomycetes. The mineralisation of plant residues could accelerate the rate of decomposition.

Porous High-Valence Metal-Organic Framework Featuring Open Coordination Sites for Effective Water Adsorption.

The design and preparation of a porous high-valence metal-organic framework (MOF) featuring open coordination sites are of utmost importance for the development of adsorbent materials. Here in this work, the three-dimensional (3D) high-valence MOF [Er(dcbp)3/2(DMF)(H2O)2]·2H2O (HV-MOF-1; H2dcbp = 4,4'-dicarboxy-2,2'-bipyridine, DMF = N,N-dimethylformamide), which possesses permanent porosity and two open coordination sites, has been prepared and characterized. In the 3D framework, the dcbp molecules display two different bridging styles, resulting in ordered diamondlike pores with bared carboxyl oxygen and pyridine nitrogen atoms on dcbp exposed directly to the pores, generating hydrophilic characteristics and high water affinity. In addition, the open coordination sites act as arms to fix the adsorbed water molecules, providing high water adsorption capacity (5.95 mmol g-1) and selectivity. More importantly, the activated HV-MOF-1 species shows an energy-saving step for recycling (operation under 120 °C), demonstrating promise as a candidate for an adsorbent material with considerable water adsorption-desorption cycles.

FUNCTIONAL ROLES OF LIPID METABOLITE CDP DIACYLGLYCEROL AND ITS SYNTHASE ENZYMES: RECENT DEVELOPMENTS

Phospholipids are basic building-block molecules for biological membranes. Biosynthesis of phospholipids i.e phosphatidylinositol, phosphatidylglycerol and phosphatidylserine requires a central liponucleotide intermediate named cytidine-diphosphate diacylglycerol (CDP-DAG). The CDP-DAG synthase (CDS) is an integral membrane enzyme catalysing the formation of CDP-DAG, an essential step for phosphoinositide recycling during signal transduction. New roles are being ascribed to the CDP-DAG in signalling and pathophysiological conditions. This pathway may also be the target of novel drugs to be used in neuro-psychiatric conditions.
 Key words: Phospholipids, Cytidine diphosphate, diacylglycerol, phosphatidic acid, phosphatidylglycerol.

Evaluating the material resource efficiency of secondary aluminium production: A Monte Carlo-based decision-support tool

The contamination of aluminium streams during the different life cycle stages by alloy mixing and/or accumulation of foreign elements, in combination with the limited melt purification options during remelting, represents an important limiting factor in recycling. Consequently, in secondary aluminium production, primary aluminium is used to dilute the concentration of the residual elements, and alloying elements are added to adjust the composition to the target alloy specifications. However, adding elements, for which their refinement in a subsequent recycling step is problematic, results in permanent down-cycling or ‘quality losses’. Hence, it is crucial to more efficiently control the composition of the metal streams prior to remelting. This article focuses on the aluminium cascade recycling chain and presents a Monte Carlo-based decision-support tool aiming to: i) identify all feasible clustering solutions per case based on input/output analysis; ii) quantify their environmental effect, and analyze the trade-offs; iii) consider scrap composition uncertainty/variability. Results reveal that primary resource additions can be minimized by optimizing metal sorting, and thus closing the recycling loop more effectively. Case studies are presented to illustrate the different functions of the tool, including examination of the Pareto front, and evaluation of the ‘recyclability’ of a scrap stream or a sorting solution into different alloy systems.

CRISPR/Cas9-Mediated Homology-Directed Genome Editing in Pichia pastoris.

State-of-the-art strain engineering techniques for themethylotrophic yeast Pichia pastoris (syn. Komagataella spp.) include overexpression of endogenous and heterologous genes and deletion of host genes. For efficient gene deletion, methods such as the split-marker technique have been established. However, synthetic biology trends move toward building up large and complex reaction networks, which often require endogenous gene knockouts and simultaneous overexpression of individual genes or whole pathways. Realization of such engineering tasks by conventional approaches employing subsequent steps of transformations and marker recycling is very time- and labor-consuming. Other applications require tagging of certain genes/proteins or promoter exchange approaches, which are hard to design and construct with conventional methods. Therefore, efficient systems are required that allow precise manipulations of the P. pastoris genome, including simultaneous overexpression of multiple genes. To meet this challenge, we have developed a CRISPR/Cas9-based kit for gene insertions, deletions, and replacements, which paves the way for precise genomic modifications in P. pastoris. In this chapter, the versatile method for performing these modifications without the integration of aselection marker is described. A ready-to-use plasmid kit for performing CRISPR/Cas9-mediated genome editing in P. pastoris based on the GoldenPiCS modular cloning vectors is available at Addgene as CRISPi kit (#1000000136).

Structure optimization of separating nozzle for waste plastic recycling

The wide application of plastic products had led to a large amount of waste plastics, which brought serious environmental pollution problems. Although separation is the first step of waste plastic recycling, the injection separating device is still not fully optimized. In this paper, the influences of nozzle outlet diameter, contraction ratio, length of contraction section, total length of nozzle, and distance between two nozzles on plastic separating device were systematically simulated and analyzed using computational fluid dynamics (CFD) software. Based on the Witozinsky curve, the optimal parameters combination of nozzle outlet diameter, contraction ratio, length of contraction section, and distance between two nozzles were found to be 6 mm, 1.6, 4 mm, and < 12 mm. Therefore, a new streamlined nozzle was designed. Best separation result was also obtained under this parameters combination, which indicated the good agreements between experimental data and simulation results.

Aluminium sheet metal scrap recycling through friction consolidation

Abstract In the last decades, several direct-recycling techniques have been developed and investigated in order to avoid material remelting, typical of the conventional aluminum alloys recycling processes. Moreover, the remelting step for aluminum recycling is affected by permanent material losses. Solid-state recycling processes have proven to be a suitable strategy to face such issues. Friction Consolidation is an innovative solid state-recycling technology developed for metal chips. During the process, a rotating die is plunged into a hollow chamber containing the material to be processed. The work of friction forces decaying into heat soften the material and, together with the stirring action of the die, enable solid bonding phenomena producing a consolidated metal disc. This technology has been successively applied to metal chips; in this paper, the feasibility of the process to recycle sheet metal scrap is investigated. The quality of the obtained billets is evaluated through morphological observation and hardness measurements.

Functional analysis of Arabidopsis and maize transgenic lines overexpressing the ADP-ribose/NADH pyrophosphohydrolase, AtNUDX7.

The conserved poly(ADP-ribosyl)ation (PAR) pathway consists of three genetic components that are potential targets to modulate the plant's energy homeostasis upon stress with the aim to improve yield stability in crops and help secure food supply. We studied the role of the PAR pathway component ADP-ribose/NADH pyrophosphohydrolase (AtNUDX7) in yield and mild drought stress by using a transgenic approach in Arabidopsis thaliana and maize (Zea mays). Arabidopsis AtNUDX7 cDNA was overexpressed in Arabidopsis and maize by means of the constitutive Cauliflower Mosaic Virus 35S promoter and the strong constitutive Brachypodium distachyon pBdEF1α promoter, respectively. Overexpression of AtNUDX7 in Arabidopsis improved seed parameters that were measured by a novel, automated method, accelerated flowering and reduced inflorescence height. This combination of beneficial traits suggested that AtNUDX7 overexpression in Arabidopsis might enhance the ADP-ribose recycling step and maintain energy levels by supplying an ATP source in the poly(ADP-ribosyl)ation energy homeostasis pathway. Arabidopsis and maize lines with high, medium and low overexpression levels of the AtNUDX7 gene were analysed in automated platforms and the inhibition of several growth parameters was determined under mild drought stress conditions. The data showed that the constitutive overexpression of the Arabidopsis AtNUDX7 gene in Arabidopsis and maize at varying levels did not improve tolerance to mild drought stress, but knocking down AtNUDX7 expression did, however at the expense of general growth under normal conditions.

Genomics and biochemistry investigation on the metabolic pathway of milled wood and alkali lignin-derived aromatic metabolites of Comamonas serinivorans SP-35

BackgroundThe efficient depolymerization and utilization of lignin are one of the most important goals for the renewable use of lignocelluloses. The degradation and complete mineralization of lignin by bacteria represent a key step for carbon recycling in land ecosystems as well. However, many aspects of this process remain unclear, for example, the complex network of metabolic pathways involved in the degradation of lignin and the catabolic pathway of intermediate aromatic metabolites. To address these subjects, we characterized the deconstruction and mineralization of lignin with milled wood lignin (MWL, the most representative molecule of lignin in its native state) and alkali lignin (AL), and elucidated metabolic pathways of their intermediate metabolites by a bacterium named Comamonas serinivorans SP-35.ResultsThe degradation rate of MWL reached 30.9%, and its particle size range was decreased from 6 to 30 µm to 2–4 µm—when cultured with C. serinivorans SP35 over 7 days. FTIR analysis showed that the C–C and C–O–C bonds between the phenyl propane structures of lignin were oxidized and cleaved and the side chain structure was modified. More than twenty intermediate aromatic metabolites were identified in the MWL and AL cultures based on GC–MS analysis. Through genome sequencing and annotation, and from GC–MS analysis, 93 genes encoding 33 enzymes and 5 regulatory factors that may be involved in lignin degradation were identified and more than nine metabolic pathways of lignin and its intermediates were predicted. Of particular note is that the metabolic pathway to form the powerful antioxidant 3,4-dihydroxyphenylglycol is described for the first time in bacteria.ConclusionElucidation of the β-aryl ether cleavage pathway in the strain SP-35 indicates that the β-aryl ether catabolic system is not only present in the family of Sphingomonadaceae, but also other species of bacteria kingdom. These newly elucidated catabolic pathways of lignin in strain SP-35 and the enzymes responsible for them provide exciting biotechnological opportunities for lignin valorization in future.

Plastic waste management, a matter for the 'community'.

Plastic waste management, a matter for the 'community'.

Nafion as effective and selective heterogeneous catalytic system in O-metalation of silanols and POSS silanols

Herein, we demonstrate the first use of Nafion as heterogeneous catalyst in O-metalation of compounds containing SiOH moiety (silanols and POSS silanols). Our methodology permits efficient and highly selective formation of SiOE bonds (E = Si, Ge, B) within molecules, under mild conditions with excellent yields. This approach allows syntheses of various unsymmetrical disiloxanes, germasiloxanes and borasiloxanes, as well as introduction of a wide range of functional groups into silsesquioxanes. It is worth noting that Nafion can be reused for further experiments and its catalytic activity in this process is well-maintained for more than 10 recycling steps, without a decrease in yield or selectivity.

Revealing salt-expedited reduction mechanism for hollow silicon microsphere formation in bi-functional halide melts

The thermochemical reduction of silica to silicon using chemical reductants requires high temperature and has a high activation energy, which depends on the melting temperature of the reductant. The addition of bi-functional molten salts with a low melting temperature may reduce the required energy, and several examples using molten salts have been demonstrated. Here we study the mechanism of reduction of silica in the presence of aluminum metal reductant and aluminum chloride as bi-functional molten salts. An aluminum–aluminum chloride complex plays a key role in the reduction mechanism, reacting with the oxygen of the silica surfaces to lower the heat of reaction and subsequently survives a recycling step in the reaction. This experimentally and theoretically validated reaction mechanism may open a new pathway using bi-functional molten salts. Furthermore, the as-synthesized hollow porous silicon microsphere anodes show structural durability on cycling in both half/full cell tests, attributed to the high volume-accommodating ability.

Prediction studies of environment-friendly biodegradable polymeric packaging based on PLA. Influence of specimens’ thickness on the hydrolytic degradation profile

Application of new biodegradable polymer packaging based on polylactide (PLA), susceptible to organic recycling, can help in the waste reduction in landfills. In this paper, the results of the study on abiotic degradation of PLA and its blend containing 15 mol% of poly[(R,S)-3-hydroxybutyrate], as a model for the first step of organic recycling were presented. The samples used for this study have different shapes and thicknesses: rigid films and cuboid-bars. Particular emphasis was placed on determining the pattern of degradation products released into the medium. Originally, the results of present study revealed that the application of electrospray ionization mass spectrometry supported by high performance liquid chromatography allowed envisaging the differences in the degradation products pattern released from the studied PLA-based samples differing in thickness. The significant differences in degradation products pattern were predominately observed in the first steps of incubation process and are caused by an autocatalytic effect, which occurs mainly during degradation of the large size PLA samples. Although, the thickness of PLA-based packaging changes the degradation product patterns, however this does not increase the total amounts of acids released to the medium. Thus, it may be concluded that thickness should not affect significantly organic recycling of the packaging.

Risk Assessment and Countermeasure Research of Lithium Battery Air Transport

Lithium batteries are used more and more widely and play a role in many fields. However, lithium batteries often cause accidents during air transport. From lithium battery cell production to battery assembly and battery recycling and other steps, six links will involve air transport. At present, domestic and international research on lithium battery only presents an improved method of battery material, but there is less research on the risk of lithium battery air transport. This study is to put lithium batteries into the air transport system to be considered, and made some suggestions.