Rohstoffliches Recycling von glasfaserverstärktem Polyamid‐6

It is well known that polyamide 6 (PA‐6) can be depolymerised to regenerate caprolactam monomer by treatment with phosphoric acid, and can thus be subjected to tertiary recycling (=according ASTM D 5033‐90: the process technologies of producing chemicals from scrap or waste plastics). However, broad general application of this process — widely used in industrial practice especially for PA‐6 fibre waste — to fibreglass‐reinforced or filled PA‐6 is precluded by the fact that phosphoric acid reacts with the fillers. This causes a high phosphoric acid consumption; moreover, the method gives an unsatisfactory yield of caprolactam (around 56%) and also requires costly disposal of phosphorus‐containing waste. Therefore, processes have been developed for tertiary recycling of fibreglass‐reinforced or filled polyamide 6, which plays an important role as an engineering plastic. Two different processes have been investigated, viz. hydrolytic depolymerisation and catalysed depolymerisation in vacuum.     

1H-NMR Characterization of Epoxides Derived from Polyunsaturated Fatty Acids

In recent years, ¹H NMR has been used to study epoxides in lipid oxidation and industrial processes, but the peak assignments reported for monoepoxides and diepoxides have been inconsistent. Lack of clear assignments for chemical shifts of epoxides derived from polyunsaturated fatty acids (PUFA) has also limited the use of ¹H NMR in detecting and quantifying these products during both oxidative degradation and industrial epoxidation. In this study, ¹H NMR was used to characterize the epoxides synthesized from trilinolein, trilinolenin, canola oil, and fish oils by reaction with formic acid and hydrogen peroxide. Assignments for epoxides derived from PUFA in canola oil and fish oil were between 2.90–3.23 ppm and 2.90–3.28 ppm, distinct from other chemical groups in these oils. Chemical shifts of epoxy groups moved downfield with an increasing number of epoxy groups in the fatty acid chain. Hence, peaks for diepoxides appeared at 3.00, 3.09, and 3.14 ppm and for triepoxides at 3.00, 3.16, and 3.21 ppm. Results also suggested that stereoisomers of diepoxides and triepoxides were formed during the epoxidation process under the conditions of this study. These new assignments for di‐ and tri‐epoxide stereoisomers were supported by GC–MS analysis of their methyl esters, H–H COSY experiments, and a re‐evaluation of several previous epoxide‐related studies.     

A brief review on hydrometallurgical technologies for recycling spent lithium‐ion batteries

Lithium‐ion battery is a mature technology that is used in various electronic devices. Nowadays, this technology is a good candidate as energy storage for electric vehicles. Therefore, much research is focused on the development of high‐density power lithium‐ion batteries. Government regulations force manufacturers to recycle the batteries for safety and health reasons but recycling could also be interesting from an economic viewpoint since cathodes in lithium‐ion batteries contain valuable metals. The electrodes in lithium‐ion batteries will evolve to provide more energy and the recycling processes will have to fit with this evolution. Leaching, bioleaching and solvent extraction are at the centre of these processes. In this paper, recent leaching and solvent extraction strategies for recovering valuable metals from spent lithium‐ion batteries are reviewed and the evolution of these processes is discussed. © 2013 Society of Chemical Industry     

Characterization of recycled styrene butadiene rubber ground tire rubber: Combining X‐ray fluorescence,differential scanning calorimetry,and dynamical thermal analysis for quality control

Appraisal of the main rubber characterization techniques for styrene butadiene rubber (SBR) was performed on standard SBR samples as well as recycled ground tire rubber (GTR) from an industrial tire recycling facility, containing a blend of SBR and natural rubber. The aim of the work was to provide additional information relevant to quality control in the field of rubber recycling. Benchmark characterization of industrial samples by inductively coupled plasma optical emission spectrometry, atomic absorption spectrometry, solid‐state proton nuclear magnetic resonance, and elemental (CHNS) analysis are reported. X‐ray fluorescence spectrometry is shown to be rapid and quantitative for determining the zinc content in an industrial context. Thermogravimetric analysis, already used to determine carbon black and inorganic material content in rubbers and GTR, is recommended for determination of monomer weight ratios of SBR sources not containing other rubbers, but not for GTR. Differential scanning calorimetry (DSC) measurements of the glass‐transition show that changes in monomer ratio affect glass‐transition temperature values, and therefore, DSC can be used to detect changes in rubber composition from batch to batch. These results show that DSC and X‐ray fluorescence spectroscopy characterization techniques can be used for GTR and may lead to more thorough and rapid quality control procedures of these complex samples. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42692.     

Depletion of Host-Derived Cyanide in the Gut of the Eastern Tent Caterpillar, Malacosoma americanum

Using a colorimetric procedure, we assessed the HCN-p of black cherry leaves (Prunus serotina) ingested by the eastern tent caterpillar, Malacosoma americanum, and the cyanide content of the bolus as it passed thorough the caterpillar's digestive tract and into the detritus pool. The mean HCN-p of leaves in our study area was 1902 ± 174 (SE) ppm. Young leaves found at the tips of growing branches, which the caterpillars preferred, had a significantly higher HCN-p (3032 ± 258 ppm) than older leaves found at the middle (1542 ± 243 ppm) or base of the shoot (1131 ± 159 ppm). Following a bout of overnight feeding on young leaves, the cyanide content of the foregut and midgut boluses of early sixth-instar caterpillars averaged 631 ± 161 ppm, and 14 ± 3 ppm, respectively, indicating that host-derived cyanide is rapidly depleted as the bolus transits the gut. Some cyanide, however, remains. In three studies, the mean cyanide content of fresh fecal pellets ranged from approximately 20 to 38 ppm, while the dried, compacted pellets ranged from 63 to 85 ppm. Food in the foreguts of mature caterpillars dispersing over the ground in search of pupation sites had 417 ± 99 ppm cyanide. The potential impact of this egested and caterpillar-transported cyanide on the consumer and detritivore communities is discussed.     

Compatibilization of PE/PS and PE/PP blends. I. Effect of processing conditions and formulation

The objective of this work was to study the effectiveness of low‐cost commercial compatibilizers and several processes (internal mixer, single‐ and twin‐screw extruders) for two types of plastic blends: high‐density polyethylene/polypropylene and high‐density polyethylene/polystyrene blends, to gain insight into the recycling of wastes from those frequently encountered mixed plastics. Blends going from a pure A to a pure B component, with and without a compatibilizer, were prepared using an internal mixer, a corotating twin‐screw extruder, as well as a single‐screw extruder to follow an industrial‐convenient process. In both cases, the analyses of blend morphologies highlighted the poor adherence between the two phases in the uncompatibilized blends. Compatibilized blends display better adherence between phases and the ability to process blends made from both single‐ and twin‐screw extruders. When adding a compatibilizer, the viscosity of each blend (PE/PP or PE/PS) increased due to a better adhesion of the phases. Charpy impact tests showed that the presence of the compatibilizer in PE/PS blends increased their impact properties. Indeed, the improvement of the adhesion between the two phases enabled stress transfer at the interface. A single‐screw extruder seems to be efficient as a processing method on an industrial scale when a compatibilizer is used. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2475–2484, 2003     

Long‐Term Stability,Regeneration and Recycling of Imidazolium‐based Ionic Liquids

Ionic liquids (ILs) are discussed in many current research papers extensively in terms of their potential use in the chemical industry, as process aids and novel materials. The long‐term stability of the IL is for industrial applications as important as to know which species arise during the degradation due to thermal, mechanical, chemical or electrochemical stress. The investigation of the long‐term stability of two selected ILs over several months under process‐like conditions is presented with a subsequent analysis by LC‐MS to identify the resulting decomposition products. Knowledge about the occurring species and their analytical quantification are basis for the selection of appropriate processes for the separation of the decomposition products and the development of recycling processes for ILs. Particularly melt crystallization processes are suitable for separating structurally similar decomposition products that typically occur in the IL degradation.     

Chemisches Recycling für Kunststoffe: Status und Perspektiven

The mechanical recycling of plastics has been established on an industrial scale for years but has technical and economic limits. Chemical recycling processes lead back to monomers or to the raw materials, so that in the end new goods can be produced for all areas of application of plastics. The variety of chemical recycling processes is large. The capacities of the plants are still low today and the profitability is strongly influenced by the oil price. The profitability limit is currently between 50 and 60 US $ per barrel.     

浅谈工业污水处理和回收利用

本研究主要针对工业污水在处理和回收利用方面的内容做出简要分析,希望所得结果能够引起大家的关注和重视。文章首先针对工业污水的处理的分类情况以及处理原则进行了介绍,并且进一步介绍了工业污水的回收利用标准以及工业污水回收利用的处理工艺,其中包括工业污水回收利用的方式、分散式工程污水回收利用的规划以及集中式工业污水回收利用的规划等。     

钢铁工业含锌含氰废水的化学预处理研究

采用氧化法、沉淀法去除钢铁工业含锌含氰废水中的氰化物和锌离子。由实验得出优化工艺条件:pH为9～10,温度为25℃,有效氯质量浓度为250 mg/L,搅拌反应时间为30 min。工业应用考察结果表明,污水混合池外排出水的总氰化物平均为4.42 mg/L,锌离子平均为14.71 mg/L,能达到湘潭钢铁集团有限公司内部工业循环用水的标准要求(Q/OHAB 801.1—2009)(总氰化物≤10 mg/L,锌离子≤30 mg/L)。     

Aposematism in Archips cerasivoranus Not Linked to the Sequestration of Host-derived Cyanide

This study addressed the question of how caterpillars of Archips cerasivoranus feeding upon Prunus virginiana cope with the cyanogenic compounds of their food. Analysis by ion chromatography showed that young and aged leaves of P. virginiana consumed by the caterpillars during spring have hydrogen cyanide potentials (HCN-ps) of 2,473 +/- 130 ppm and 1,058 +/- 98 ppm, respectively. Although less than 3% of the cyanide released as the caterpillars feed escapes into the atmosphere, the larva's bright-yellow aposematic coloration and conspicuous activity can not be attributed to the sequestration of cyanide. Only six of 25 samples of the caterpillars' defensive regurgitants collected from 12 field colonies contained cyanide (17.6 +/- 6.54 ppm), less than 5% of the quantity previously reported to occur in the regurgitant of the tent caterpillar M. americanum. Only seven of 13 caterpillars assayed had detectable quantities of cyanide in their bodies (3.9 +/- 0.9 ppm). The fecal pellets that encase the cocoon contained no cyanide, nor did the frass that litters the leaf shelters. The small quantities of cyanide that occur in the caterpillar compared to the HCN-p of ingested plant material appear attributable to paced bouts of feeding and the maintenance of a highly alkaline foregut that inhibits cyanogenesis.     

ELECTROCHEMICAL DESTRUCTION OF COMPLEX CYANIDE

A batch electrochemical cell consisting of a pair of stainless steel wire-mesh electrode was used to electrochemically decompose concentrated cuprous cyanide waste solution. The concentrations of free, complex, and total cyanide were measured as a function of electrolysis time for various cell currents. The total cyanide concentration in the waste solution was reduced from 1200 ppm to less than 50 ppm with an electric power consumption on the order of 14-34 kWH per kilogram of cyanide destroyed. Copper was recovered in its metallic form at the cathode and as CuO deposit at the anode with a combined recovery rate greater than 90%. In addition, cyanide complex was found to chemically decompose at the stainless steel meshes, rendering a coulombic efficiency greater than 100% in some of the experimental runs.     

ELECTROCHEMICAL DESTRUCTION OF COMPLEX CYANIDE

A batch electrochemical cell consisting of a pair of stainless steel wire-mesh electrode was used to electrochemically decompose concentrated cuprous cyanide waste solution. The concentrations of free, complex, and total cyanide were measured as a function of electrolysis time for various cell currents. The total cyanide concentration in the waste solution was reduced from 1200 ppm to less than 50 ppm with an electric power consumption on the order of 14-34 kWH per kilogram of cyanide destroyed. Copper was recovered in its metallic form at the cathode and as CuO deposit at the anode with a combined recovery rate greater than 90%. In addition, cyanide complex was found to chemically decompose at the stainless steel meshes, rendering a coulombic efficiency greater than 100% in some of the experimental runs.     

Catalytic Flue Gas Treatment from Nitriding Processes

Efficient control and minimization of emissions from technical processes is of major concern in industrial development and process operation. The technical process in the focus of the present contribution is the nitriding process of metallic specimen. The ammonia content in nitriding process flue gases reaches up to 618 g·m^–3 (80 vol.‐%) and needs to be reduced to less than 30 mg·m^–3 (40 ppm) to fulfill present regulations. Exhaust gases from nitriding processes today are burnt in flares without emission control where fuels need to be added that produce additional exhaust gas components. The objective of this investigation is to develop an alternative gas cleaning route for nitriding processes based on catalytic dissociation of ammonia. The decomposition was studied for different catalysts at varying process conditions. With these results a dissociation pilot plant was successfully tested in a technical‐scale nitriding process.     

Wastewater Minimization in Pulp and Paper Industries through Energy‐Efficient Reverse‐Osmosis Membrane Processes

Fresh water consumption and wastewater management is a mandatory task to conserve water resources and to reduce wastewater discharge from chemical production processes. Such objectives have been addressed in many industrial sectors which consume large amounts of fresh water. Possibilities for reducing wastewater volumes by regeneration and recycling routes in the pulp and paper industry are analyzed. During pulp preparation and paper making processes by the Kraft pulping method a large amount of water is required to deliver the finished paper product. Reverse osmosis (RO) is applied for the analyses as an interception separation technology to reduce salt concentrations in wastewater streams for recycling purposes. The RO network synthesis problem is formulated as mixed integer nonlinear programming model which is solved using the general algebraic modeling system. A preliminary cost estimate indicates economic incentives by installation of RO units to avoid wastewater discharge and generate relatively clean water streams for inter‐plant usage.     

Al-rich sludge treatments towards recycling

A treatment method towards recycling of Al-rich sludges to produce high-alumina refractory ceramics is proposed. These sludges are collected in wastewater treatment units of industrial plants dealing with anodising or surface coating processes. This industrial residue usually contains significant amounts of soluble salts such as Na, K, Mg, Ca and Al sulphates that make direct recycling problematic. The removal of these salts from the as-received sludges by washing is ineffective due to its gel-like consistency. The treatment consists of calcining and subsequent washing operations, followed by removal of sulphates by precipitation as BaSO₄. The treated sludges could then be well dispersed and processed by slip casting.     

Salt‐free softening by thermo‐reversible ion‐adsorbing hydrogels

In this article, we demonstrate the properties of a hydrogel capable of adsorbing calcium cations from aqueous streams at ambient temperatures (10–25°C) and showing almost complete desorption of the bound calcium ions at slightly elevated temperatures (40–50°C). Successful breakthrough experiments in a fixed bed column set‐up show the potential of the hydrogel in softening water streams from 150 ppm toward <10 ppm hardness levels. The regeneration ability is based on the thermo‐reversible internal ion pair–formation mechanism of the hydrogel. Additionally, it was shown that the thermo‐reversible adsorption mechanism was successful for magnesium and copper ions too. The exploration of the properties of hydrogel CS‐1B14 is the first step in the development of sustainable water‐softening processes, both at industrial scale as well as for household applications, using low‐grade residual heat to regenerate these gels. In this way, the use of concentrated brine streams, acid/caustic treatment, or high regeneration temperatures is avoided. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40216.     

Preparation of crosslinked β‐cyclodextrin polymer beads and their application as a sorbent for removal of phenol from wastewater

BACKGROUND: Phenols are commonly encountered in aqueous effluents from various manufacturing processes such as oil refineries, coke plants, and phenolic resin plants, and are toxic substances that should be removed from the aquatic environment. This paper reports on the preparation of beaded crosslinked β‐CyD polymers, and the removal of phenol by the β‐CyD adsorbent from raw industrial wastewater discarded from phenolic resin processing. RESULTS: Crosslinked β‐CyD prepolymer was synthesized by treatment of β‐CyD with hexamethylene diisocyanate (HDI) at a molar ratio of 1:8. The suspension of the resulting powdery prepolymer in aqueous sodium alginate was added dropwise into an aqueous calcium chloride solution to precipitate the spherical β‐CyD prepolymer gels. The spherical prepolymer gel was lyophilized and re‐crosslinked with HDI to provide the β‐CyD polymer beads. The physical properties of the beads were as follows: average diameter: 3.4 mm; average compressive strength: 2.17 MPa; porosity: 47.0%; specific surface area: 3.48 m² g^?1. The removal of phenol from raw industrial phenolic wastewater with the β‐CyD polymer beads was carried out in either a shaker or an upflow column at 25 °C. After seven episodes of accumulated adsorption, the initial phenol concentration of 89000 ppm decreased to as low as 350 ppm in the shaker and 490 ppm in the upflow column. CONCLUSION: Adsorbent [β‐CyD/HDI(1/8)]/HDI polymer beads having a good regular shape and high mechanical stability were newly prepared by a stepwise crosslinking method. The results of sorption experiments show that the beads exhibit high sorption capacities for phenolics in raw industrial wastewater. Copyright © 2008 Society of Chemical Industry     

Operability of an Industrial Methanol Synthesis Reactor with Mixtures of Fresh and Partially Deactivated Catalyst

Disposal of spent catalyst is a common practice in industrial methanol synthesis. However, the spent catalyst has, generally, a good level of activity and can be used if mixed with fresh catalyst. In this work the operation of an industrial methanol synthesis reactor with mixtures of fresh and partially deactivated catalyst was investigated using a one‐dimensional transient model. Analysis of the deactivation behavior of low‐pressure methanol synthesis catalyst shows there is an extremely sharp rate of deactivation in a small part of the catalyst life‐time, which is followed by a relatively slow rate of deactivation in the remaining catalyst cycle‐time. Different configurations were studied for catalyst recycling, and two limiting cases are discussed in detail in this paper, namely layered and homogeneous (mixed) bed models. In the first one, the catalyst was segregated into two alternate layers of fresh and partially deactivated catalyst, while in the second homogeneity of the catalyst bed was simulated by segregating a large number of alternate layers of fresh and partially deactivated catalyst. It was observed in both cases that when catalyst recycling is used, the process does not depart significantly from the standard operating conditions, and also that the mixed bed had less influence on the reactor performance than layered one.     

Recycling of polypropylene‐based eco‐composites

BACKGROUND: Renewable resources and recyclable thermoplastic polymers provide an attractive eco‐friendly quality as well as environmental sustainability to the resulting natural fibre‐reinforced composites. The properties of polypropylene (PP)‐based composites reinforced with rice hulls or kenaf fibres were investigated with respect to their recyclability. Rice hulls from rice processing plants and natural lignocellulosic kenaf fibres from the bast of the plant Hibiscus cannabinus represent renewable sources that could be utilized for composites. Maleic anhydride‐grafted PP was used as a coupling agent to improve the interfacial adhesion between fillers and matrix. Composites containing 30 wt% reinforcement were manufactured by melt mixing and their mechanical and thermal properties were determined. The composites were then pelletized and reprocessed by melt mixing. Finally, structure/properties relationships were investigated as a function of the number of reprocessing cycles. RESULTS: It is found that the recycling processes do not induce very significant changes in flexural strength and thermal stability of the composites. In particular PP‐based composites reinforced with kenaf fibres are less sensitive to reprocessing cycles with respect to PP‐based composites reinforced with rice hulls. CONCLUSION: The response of PP‐based composites reinforced with rice hulls or kenaf fibres is promising since their properties remain almost unchanged after recycling processes. Moreover, the recycled composites are suitable for applications as construction materials for indoor applications. In fact, the flexural strength and modulus of these materials are comparable to those of conventional formaldehyde wood medium‐density fibreboards. Copyright © 2008 Society of Chemical Industry