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1.
Chimia (Aarau) ; 73(9): 743-749, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31514776

RESUMO

Plastic, in the form of packaging material, disposables, clothing and other articles with a short lifespan, has become an indispensable part of our everyday life. The increased production and use of plastic, however, accelerates the accumulation of plastic waste and poses an increasing burden on the environment with negative effects on biodiversity and human health. PET, a common thermoplastic, is recycled in many countries via thermal, mechanical and chemical means. Recently, several enzymes have been identified capable of degrading this recalcitrant plastic, opening possibilities for the biological recycling of the omnipresent material. In this review, we analyze the current knowledge of enzymatic PET degradation and discuss advances in improving the involved enzymes via protein engineering. Looking forward, the use of plastic degrading enzymes may facilitate sustainable plastic waste management and become an important tool for the realization of a circular plastic economy.


Assuntos
Gerenciamento de Resíduos , Plásticos , Embalagem de Produtos , Reciclagem
2.
Waste Manag ; 99: 42-48, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31472439

RESUMO

This paper presents a novel development of sludge cellulose plastic composite (SPC) in line with the circular economy concept by using recovered sludge cellulose from wastewater treatment plant (WWTP). Bearing the aim of replacing the wood in wood plastic composite (WPC) with sludge cellulose, WPC was developed in parallel for determining the substitution potentials. In order to maximise the integration of properties, maleic anhydride (MA) and vinyltrimethoxysilane (VTMS) coupling agents were employed to refine the interfacial bonding of both SPC and WPC. In line with the main aim of circular economy - to decouple the economic value from the environmental impact, eco-efficiency analysis was performed for the developed process. The results showed that the tensile and flexural strength of the composites were substantially enhanced after both treatments, while MA appeared to be more efficient than VTMS in the refinery of interfacial bonding. Scanning electron microscope (SEM) analysis confirmed the improvement of interface by identifying well embedded and firmly bonded wood flour or sludge cellulose in the matrix. WPC was marginally more thermally stable than SPC, while SPC suggested comparable flexural properties. Eco-efficiency assessment results showed that the SPC had better environmental and economic performance than the WPC. The latter turns sludge cellulose as a promising sustainable alternative to wood or natural fibres in the production of WPC.


Assuntos
Plásticos , Madeira , Celulose , Reciclagem , Esgotos
3.
Waste Manag ; 99: 60-70, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31472441

RESUMO

Life cycle assessment of recycling rare earths from waste fluorescent powders was conducted, including the uncertainty and sensitivity analyses. Three scenarios were set in this study, namely, recycling with/without final disposal and waste fluorescent powders landfill. Recycling with final disposal presented lower environmental burden than that without final disposal due to the significant reduction of direct emissions. The evident impacts from chemicals and energy production stages were considered the main contributors to the overall environmental burden of recycling with final disposal due to their relatively high emissions of particulates matter, sulfur dioxide, heavy metals, and carbon dioxide as well as the use of fossil fuel. Compared with landfills, rare-earth recycling shows the highest environmental benefits because of the substitution of primary rare earths. To relieve the high demand of rare earths and reduce the overall environmental burden, governments are highly recommended to increase recycle rate, create a complete management system, improve energy consumption and wastewater treatment efficiency, and build an adequate recycle standard.


Assuntos
Metais Terras Raras , Eliminação de Resíduos , Gerenciamento de Resíduos , China , Pós , Reciclagem , Instalações de Eliminação de Resíduos
4.
Waste Manag ; 99: 112-121, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31476636

RESUMO

This study developed a novel method, surface pretreatment using sodium hypochlorite along with flotation, to facilitate separation of waste polycarbonate from plastic mixtures for recycling. Surface pretreatment was observed that has an obviously negative effect on the floating ratio of polycarbonate and the floating ratio of poly-methyl-methacrylate, polystyrene, and polyvinylchloride was not affected in flotation, and this difference in floating ratio can be expected to separate polycarbonate from plastic mixtures. The optimum conditions obtained included sodium hypochlorite concentration of 0.05 M, pretreatment temperature of 70.0 °C, pretreatment time of 60.0 min, frother dosage of 10.8 mg/L, and flotation time of 4.0 min. Under optimum conditions, polycarbonate was separated effectively from multiple plastic mixtures, and the purity and recovery were 99.8% and 100.0%, respectively. The major mechanism of surface pretreatment was ascertained by the aid of Fourier transform infrared, scanning electron microscope, energy dispersive spectrometer, and X-ray photoelectron spectroscopy, and the hydrophilic groups, pitting, and protuberances introduced on polycarbonate surface caused the reduced floating ratio of polycarbonate. Accordingly, this method can be expected to improve the recycling quality of waste plastics, and provides technological insights in the environmentally friendly disposal of waste plastics.


Assuntos
Plásticos , Eliminação de Resíduos , Cimento de Policarboxilato , Reciclagem , Hipoclorito de Sódio
5.
Waste Manag ; 97: 71-81, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31447029

RESUMO

The effect of recycling on the thermo-mechanical and water absorption behavior of polypropylene (PP)/sisal fiber and polylactic acid (PLA)/sisal fiber composites were studied. The PP-based non-biodegradable composites and PLA-based biodegradable composites were recycled for four times. The effect of recycling was determined by examining the morphology, thermo-mechanical properties, and water absorption behavior and the obtained results were compared. The results showed that the incorporation of sisal fibers in the PP and PLA matrix enhances the tensile modulus and percentage crystallinity of the composites. The tensile strength and modulus of the sisal fiber reinforced PP composites were not affected with recycling. Even though the tensile properties of PLA and PLA/sisal fiber reinforced composites are superior to PP and PP/sisal fiber composites, the PLA-based composites show a dramatic decrease in tensile strength and modulus after the first recycling due to the degradation of the polymer. The thermal stability of the PP/sisal fiber composites was not affected by the repeated recycling process. On the other hand, the PLA-based composites with higher sisal fiber content show a bit lower thermal stability after recycling. The PP-based composites show fluctuations in percentage crystallinity with recycling. On the other hand, a remarkable increase in percentage crystallinity for PLA and PLA-based composites was observed with increasing recycling times. Water diffusion study divulges that the diffusion of water into the polymer composites was reduced with recycling, irrespective of the polymer matrix.


Assuntos
Polipropilenos , Água , Poliésteres , Reciclagem
6.
J Agric Food Chem ; 67(35): 9858-9867, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31389230

RESUMO

Farnesene is an important chemical platform for many industrial products, such as biofuels and polymers. We performed high-efficiency utilization of corncobs for ß-farnesene production by separate hydrolysis and fermentation with an optimized Escherichia coli strain. First, we developed a recycling strategy for both corncob pretreatment and cellulose hydrolysis, which saved great amounts of pretreatment reagents and presented a 96.83% cellulose conversion rate into glucose. However, the corncob hydrolysate strongly repressed cell growth and ß-farnesene production, being caused by high-concentrated citrate. Through expressing a heterologous ATP citrate lyase and screening for a suitable expression host, an optimized strain was constructed that produced ß-farnesene at 4.06 g/L after 48 h in a 5 L fermenter, representing an approximately 2.3-fold increase over the initial strain. Therefore, the proposed strategy about the recycling process and repression elimination was successful and suitable for the production of lignocellulosic-based ß-farnesene, which can be further studied to scale up for industrialization.


Assuntos
Escherichia coli/genética , Escherichia coli/metabolismo , Lignina/metabolismo , Sesquiterpenos/metabolismo , Fermentação , Glucose/metabolismo , Hidrólise , Engenharia Metabólica , Reciclagem , Resíduos/análise , Zea mays/química , Zea mays/microbiologia
7.
J Environ Manage ; 248: 109313, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31374434

RESUMO

End of life photovoltaic panels of different technologies (poly crystalline Si, amorphous Si, and CdTe) were treated mechanically in pilot scale by single shaft shredder minimizing the production of fine fractions below 0.4 mm (<18% weight). Grounded material was sieved giving: an intermediate fraction (0.4-1 mm) of directly recoverable glass (18% weight); a coarse fraction (which should be further treated for encapsulant removal), and fine fractions of low-value glass (18%), which can be treated by leaching for the removal of metal impurities. Encapsulant removal from coarse fraction was successfully performed by solvent treatment using cyclohexane at 50 °C for 1 h giving high-grade glass (52% weight), which can be reused for panel production. Experimental results of solvent treatment were compared with those from thermal treatment by economic analysis and Life Cycle Assessment, denoting in both cases the advantages of solvent treatment in recovering high-value glass.


Assuntos
Compostos de Cádmio , Pontos Quânticos , Telúrio , Vidro , Reciclagem , Silício , Solventes
8.
J Environ Manage ; 248: 109282, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31374435

RESUMO

This research work was an exploration of the feasibility of utilizing a lithium slag (LS) and fly ash (FA)-based binder for cemented fine tailings backfill (CFTB). Extensive experiments were conducted with different combinations of LS and ordinary Portland cement (OPC), along with FA as an additive. The unconfined compressive strength (UCS), micromorphology and slump values were analyzed. The results showed that (i) the LS and FA had a significant influence on the strength of binders. The OPC-LS-FA ratio of 2:1:1 appeared to be optimal with the highest strength and was referred as the LS and FA-based binder (LFB). (ii) The LFB significantly improved the UCS of the CFTB. The UCS values of CFTB specimens curing for 7,28 and 56 days reached 0.95 MPa,2.28 MPa and 3.37 MPa, respectively, with a 10 wt% content of LFB. The strength satisfied the strength requirement of backfill for supporting the surrounding rock of stopes in the Yinshan lead-zinc mine (0.8 MPa, 2.0 MPa, 3.0 MPa). (iii) The pore-filling effect of the secondary hydration products, which was mainly produced by LFB, played a significant role in the early stage (<7 days), while the pozzolanic activity worked mostly in the mid-long period (>28 days). (iv) The LFB reduced the slump value of CFTB slurry by 2.6%-9.4% compared with OPC when the mass concentration increased from 58% to 64%, which was acceptable to satisfy the requirements of better fluidity and less transportation resistance in the Yinshan lead-zinc mine. Therefore, the LFB could be utilized as an alternative cementitious material for CFTB, which also provides a safe and economical approach to recycle LS and FA in an underground mine.


Assuntos
Cinza de Carvão , Lítio , Força Compressiva , Materiais de Construção , Reciclagem
9.
Waste Manag ; 96: 1-8, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31376953

RESUMO

Samples of sunflower Waste Cooking Oils (WCOs) subjected to several cycles of frying were treated with water under four different combinations of temperature and pH. Several aspects of the chemical composition of edible, non-treated and processed samples was determined by three different analytic techniques: headspace Solid-Phase Microextraction (HS-SPME) coupled with gas-chromatography (GC), 1H NMR spectroscopy and ESI-MS spectrometry. Thus, a characteristic chemical fingerprint of each sample was derived and proposed as useful set of tools for the optimization of recycling of WCOs. On the basis of the presented results, a mini-plant for the production of bio-lubricants and bio-solvents with a circular economy approach was designed and herein described.


Assuntos
Óleos Vegetais , Microextração em Fase Sólida , Culinária , Cromatografia Gasosa-Espectrometria de Massas , Reciclagem
10.
Waste Manag ; 96: 175-180, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31376962

RESUMO

Recycling resources from millions of tons of e-wastes are a global challenge. E-wastes is complex and contains both toxic organics and valuable metals. Therefore, the technologies for e-wastes recycling are totally different from those used for mineral separation. Current technologies for e-wastes tend to focus on recycling materials with high economic value and ignore components that cannot be recycled or have low reuse value. As a result, some secondary pollution problems inevitably occur due to the recycling process. Based on these problems, we summarize the universal characteristics of e-wastes and explore new approaches to achieve complete resource recycling of e-wastes with minimum secondary waste generation. A concept of element recycling is proposed to achieve complete resource recycling of e-wastes in the study. We can use the properties of the elements in different types of e-wastes to achieve e-wastes recycling, i.e., recycle of elements in e-wastes. Under the guidance of element recycling, various e-wastes types have common connections. If element recycling in e-wastes is realized, all components in e-wastes can be fully recycled without/with minimal production of secondary waste. The two case studies are discussed to clarify the concept and principle of element recycling. This study explores the recycling of e-wastes from a new perspective-element recycling in e-wastes. The concept of element recycling is significant for resource recycling from e-wastes.


Assuntos
Resíduo Eletrônico , Metais , Reciclagem
11.
Waste Manag ; 96: 181-189, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31376963

RESUMO

In this work, an environmentally-friendly leaching process for the recovery of indium (In) and tin (Sn) from LCD panel waste was investigated. Easily degradable citrates (C6H5O73-), i.e., sodium citrate and citric acid, were used as complexing agents. The morphology and composition of the species present in the LCD powder before and after the leaching processes were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The concentrations of In, Sn, and iron (Fe) present in the leachate were determined by atomic absorption spectrometry (AAS). The necessary thermodynamic conditions for achieving substantial In recovery were established by using MEDUSA software. The optimal process conditions were determined experimentally by varying the initial citrate concentration as well as by using reducing or oxidizing media, respectively hydrazine (N2H4) or hydrogen peroxide (H2O2). It was found that using N2H4 in a citrate solution as a reducing agent enhances the leaching efficiency. However, high concentrations of Sn and Fe with respect to In were found in the LCD powder. Therefore, a pretreatment processes to first remove the excess of Sn and Fe, which compete with In for the citrate, was implemented. Leaching with 1 M citrate, 0.2 M N2H4, at pH = 5, using sodium hydroxide (NaOH) at solid:liquid (S:L) ratio of 20 g∙L-1, yielded a remarkably high In recovery of 98.9% after 16.6 h.


Assuntos
Resíduo Eletrônico , Cristais Líquidos , Citratos , Ácido Cítrico , Peróxido de Hidrogênio , Índio , Reciclagem , Estanho
12.
Waste Manag ; 96: 206-214, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31376966

RESUMO

This two paper series describes a method to develop and evaluate new recycling strategies for WEEE plastics. Part A presents a SWOT analysis that leads to five recycling strategies for the optimal integration of new dismantling based recycling processes for plastic components in an established post-shredder separation infrastructure. In this paper the technical feasibility of the strategies is demonstrated by means of LCD TV back cover housings. The component recycling is shown to produce recycled PC/ABS with phosphorous flame retardants suitable for direct re-application in electronic products. The high quality is characterized by a good mechanical and aesthetical properties as well as a recovered flammability. HIPS with brominated flame retardants was recycled to produce masterbatches. The technical feasibility of this strategy was proven by mechanical and flammability testing. However, the presence of deca-BDE requires this material to be incinerated. A combination of EU legislation research and forecasting shows that the origin of this flame retardant are TV models produced before 2008 and restricted concentrations still need to be expected for decades to come. Further, a blending strategy of HIPS/PPE is shown to improve the mechanical properties of post-shredder recycled HIPS. The evaluation of refeeding ABS/PMMA into the post-shredder recycling process of ABS indicates only partial compatibility. Further, complications due to density differences make this strategy more suitable for polymers that are already commercially recycled such as ABS and HIPS. Colour is identified as a key requirements that limits the use of WEEE plastics in high-quality products.


Assuntos
Resíduo Eletrônico , Retardadores de Chama , Estudos de Viabilidade , Plásticos , Reciclagem
13.
Waste Manag ; 96: 57-64, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31376970

RESUMO

The aviation industry generates a significant amount of comingle waste. Nowadays, companies are making efforts to enhance waste management and reduce waste generation. In order to improve present practices and implement a proper waste management system, the quantities, materials, and typology of waste generated need to be studied. A total of 145 airplanes were analysed. We differentiated 5 strips of duration and identified 4 different generation sources within the cabin associated to the business and tourist passenger classes. We classified and characterized the waste into 20 different materials. Results provide a detailed, representative and adapted study of the catering waste generated in the aviation industry. The characterization, which allows distinguishing between manipulated and unmanipulated materials, aims at providing useful information to reduce the generation of waste. The analysis performed in the present study shows that the flying distance increases the waste generation, as more food is served. It also shows that organic matter, paper/cardboard and packaging are the dominant materials in the waste generated in flights. The results of the characterizations obtained allow making some recommendations. The use of bi-compartmentalized waste trolleys to separate on-board recyclable materials from the rest is desirable to obtain a clean recoverable waste stream. Supressing unpopular food from menus, identified analysing the leftovers, could also reduce the amount of waste generated. (This characterization study is part of the European project LIFE + Zero Cabin Waste.). Changes in the CE 1069/2009 regulation would allow more waste to be recycled instead of landfilled. Ultimately, the information obtained from this study will be used to design a more sustainable waste management system.


Assuntos
Gerenciamento de Resíduos , Aeronaves , Alimentos , Embalagem de Produtos , Reciclagem
14.
Waste Manag ; 96: 75-85, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31376972

RESUMO

Recycling of plastic is an important step towards circular economy. However, plastic from household waste (HHW) is a heterogeneous and contaminated resource, leading to recycled plastic with reduced quality, limiting the potential for closed-loop recycling. In addition to regulatory requirements for the chemical composition of recycled plastic, reduced physical and mechanical properties may limit the potential for closed-loop recycling. Consequently, this study analyses the thermal degradation, processability and mechanical properties of a range of reprocessed PET, PE and PP samples from source-separated plastic in HHW. On this basis, the potential for closed-loop recycling is evaluated. The study demonstrated that PET, PE and PP recycling represent different challenges. Potential degradation of the PET polymer can be reversed in a decontamination process, making PET waste well-suited for closed-loop, multiple times recycling, even when the degree of heterogeneity in the waste is high. The processability of different kinds of PE and PP packaging types varied considerably, especially for PP. Consequently, current recycling of mixed PP waste and even separate recycling of individual PP waste packaging types, will not technically facilitate recycling into new packaging products. This highlights the importance of PE and PP waste homogeneity when sent to reprocessing. Such homogeneity may be achieved through additional plastic sorting and regulatory harmonisation of product design, accounting for polymer properties and recyclability. Degradation of PP during recycling was shown to be substantial, representing another important limitation for PP recycling, necessary to address in the future.


Assuntos
Plásticos , Reciclagem , Polietilenotereftalatos , Polímeros , Embalagem de Produtos
15.
Waste Manag ; 96: 9-14, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31376974

RESUMO

In the professional literature there is no information on the efficiency of waste treatment in MBT (mechanical-biological waste treatment) systems in Poland. This knowledge is currently particularly important as it will decide on the role of the MBT system in the new reality of the circular economy, and consequently on the direction and necessary scope of modernization of these systems. The article presents a series of technical and technological indicators designated for one of the recently commissioned MBT plants against the background of minimum, maximum and average values of these parameters set for 20 systems with various MBTs covered by the research as part of the review of technological solutions used in Poland, made in 2015. For the system in Marszów, respectively in 2017 and 2018, the average value of the ratio of underscreen to overscreen fraction was 1.4; the losses of mass in the biological treatment process amounted to 28.7 and 29.4%; energy demand - 46.6 and 44.3 kWh/Mg; the aeration index - 16.7 m3/(Mg h); the average waste recycling rate - 15.2 and 17.3%; the share of fuel fraction recovery - 11.6 and 16,6% and the share of waste sent to landfill - 33.2 and 32.3%.


Assuntos
Eliminação de Resíduos , Gerenciamento de Resíduos , Polônia , Reciclagem , Resíduos Sólidos , Instalações de Eliminação de Resíduos
16.
Waste Manag ; 98: 92-101, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31437714

RESUMO

The total and leachable metal content from mixtures of weathered municipal solid waste incinerator bottom ash (MSWI BA) and conventional natural or recycled aggregates was investigated with a focus on utilization of MSWI BA as a partial component in a road base. Two weathered bottom ashes were combined with various aggregates in multiple replacement percentages of up to 85% traditional aggregate, with the goal of mitigating leaching and direct human exposure risk. Al leaching was found to decrease proportionally to the mass of bottom ash included in the blended products, with over 90% reduction in blends with 85% recycled concrete aggregate (RCA). Release of Sb from the bottom ashes was predominantly controlled by solubility. Sb concentrations were reduced from 0.043 and 0.037 mg/L to 0.006 and 0.007 mg/L for facility A and B respectively blended with the highest tested proportion of RCA, near compliance drinking water standards of 0.006 mg/L. The high pH and presence of calcium-bearing minerals in recycled concrete appeared to facilitate significant immobilization of Sb in comparison to other aggregates. Similar results were observed for several other elements and material blends. Results indicate that blending MSWI BA with conventional aggregates is a feasible recycling application. Blending effectively mitigates environmental risk associated with the un-encapsulated use of MSWI BA in road construction.


Assuntos
Cinza de Carvão , Incineração , Materiais de Construção , Reciclagem , Resíduos Sólidos
17.
Waste Manag ; 98: 126-134, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31445457

RESUMO

Solar cell industry produces high quantities of waste in form of broken, damaged, and rejected cells, whereas milling and filtering practices are typically used to recover the valuable materials (Al, Ag and Si) from such Waste Solar Cell Wafers (WSCWs). This recycling approach has its disadvantages, e.g. excessive energy consumption and dust emission causing loss of valuable metals. To fulfil the concept of Zero Waste for WSCWs, the authors present a sustainable technology for liberation of valuable metals from WSCWs and synthesis of added value products, in particular Ag nanoparticles and Al microparticles. The suggested technology consisted of three different approaches combined to liberate each material individually. The technology started with an Al layer disintegration process using Dimethyl Sulfoxide (as an eco-friendly and sustainable solvent) supported by ultrasonic treatment to break van der Waals' bonding between spherical Al microparticles that compose the Al paste layer, thus liberating Al in microparticle suspension form with particle size ∼3 µm, recovery rate >98%. After that, leaching by nitric acid and other eco-friendly reagents (Sodium Chloride, Ammonia solution and glucose syrup) assisted by ultrasonic treatment was used to dissolve Ag and later precipitate it in form of nanoparticles with avg. size 30 nm, yield >92%. Finally, etching using paste containing phosphoric acid was done to remove anti-reflection coating and purify the Si substrate with final recovery rate >99%. SEM-EDS, XRD, FTIR, and TEM were used for analysis of extracted materials as well as changes in the solvent. Investigation was also concerned with determining economic/global warming impacts of the technology.


Assuntos
Resíduo Eletrônico , Nanopartículas Metálicas , Reciclagem , Prata , Tecnologia
18.
Waste Manag ; 97: 140-148, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31447021

RESUMO

An environmentally benign vacuum pyrolysis (VP) approach is employed to recover Li and Co from spent LiCoO2-based lithium-ion batteries (LIBs). First, the electroactive materials were separated from the current collector by the VP method from 623 to 823 K with an attempt to choose an appropriate temperature. Then, the as-received cathode materials were mixed with different amounts of graphite from the anode to selectively convert LiCoO2 to Co or CoO and Li2CO3 by carbothermic reduction under vacuum and at 873 to 1273 K. After carbothermic reduction, the pyrolyzed powder was leached in water to separate Li2CO3 from Co/CoO. By alternating the C/LiCoO2 mass ratio and the pyrolysis temperature, a recovery rate reaches over 93% for Li and 99% for Co. Finally, the recovered CoO and Li2CO3 were used to regenerated LiCoO2 that delivered a specific capacity of 145 mAh g-1 at 1C and retaining 93% of the initial capacity after 100 cycles. Overall, a multi-vacuum-pyrolysis approach offers a closed-loop route for the management of spent LIBs without using any hazardous chemicals.


Assuntos
Lítio , Pirólise , Fontes de Energia Elétrica , Reciclagem , Vácuo
19.
Waste Manag ; 98: 160-172, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31450178

RESUMO

Sorting at industrial scale is required to perform mechanical recycling of plastics in order to obtain properties that could be competitive with virgin polymers. As a matter of fact, the most part of the various types of plastic waste are not miscible and even compatible. Mid-Infrared (MIR) HyperSpectral Imagery (HSI) is viewed as one of the solutions to the problem of black plastic sorting. Many Waste of Electrical and Electronic Equipment (WEEE) plastics are black. Nowadays, these materials are difficult to sort at an industrial scale because the main used pigment to produce this color, carbon black, masks the Near-Infrared (NIR) spectra of polymers, the currently most used technology for acute sorting in industrial conditions. In this study, laboratory Fourier-Transform Infrared (FTIR) in Attenuated Total Reflection mode (ATR) has been used as a theoretical toolbox based on physical chemistry to help building an automated HSI discrimination despite its limited conditions, especially shorter wavelengths ranges. Weaker resolution and very short acquisition times are other HSI limitations. Helping fast and exhaustive laboratory characterizations of polymeric waste stocks is the other goal of this study. This study focusses on polyolefins as they represent the second biggest fraction of WEEE plastics (WEEP) after styrenics and since little quantities mixed to styrenics during mechanical recycling can lead to important decrease in mechanical properties. Twelve references were thus evaluated and compared between each other and with real waste samples to highlight spectral elements, which can enable differentiation. Charts compiling the signals of discussed polymers were built aiming to the same objective.


Assuntos
Resíduo Eletrônico , Plásticos , Polienos , Polímeros , Reciclagem
20.
Waste Manag ; 99: 31-41, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31470264

RESUMO

To avoid the formation of undesired Cl compounds during polyvinyl chloride (PVC) wastes treatment and facilitate the recycling of valuable NaCl and dechlorinated hydrocarbons as feedstocks, advanced dechlorination (de-Cl) process should be developed. Here, an up-scale ball mill reactor was established for the de-Cl of real PVC wastes, including sealing strips from waste refrigerators and crushed cable coverings from waste cables. The effects of NaOH on de-Cl were validated with lab-scale studies and the influences of mechanical conditions were innovatively investigated. A maximum de-Cl degree of 99% was obtained with 1 M NaOH in ethylene glycol for sealing strips, whereas a maximum de-Cl degree of 92% was obtained with Φ1.27 cm stainless steel balls at a moderate rotation speed for cable coverings. The remaining Cl content in the sample residues was small and decreased with decreasing residue size, resulting in minimum contents of 0.49% and 0.61% for sealing strips and cable coverings, respectively. The de-Cl behavior was consistent with a shrinking-core model and the meaning of kinetic parameters was illustrated. The ball milling process was simulated by discrete element method (DEM). A positive correlation was observed between the apparent rate constant of the experimental de-Cl process and the specific impact energy calculated using DEM simulations. The combined experimental and simulation approach suggested that the surface of PVC is first dechlorinated and then crushed into fine particles by ball milling to expose the inner unreacted surface. For industrial application, the balance of chemical and mechanical conditions should be optimized.


Assuntos
Etilenoglicol , Cloreto de Polivinila , Halogenação , Reciclagem , Hidróxido de Sódio
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