Boiling treatment of ABS and PS plastics for flotation separation

A new physical method, namely boiling treatment, was developed to aid flotation separation of acrylonitrile–butadiene–styrene (ABS) and polystyrene (PS) plastics. Boiling treatment was shown to be effective in producing a hydrophilic surface on ABS plastic. Fourier Transform Infrared analysis was conducted to investigate the mechanism of boiling treatment of ABS. Surface rearrangement of polymer may be responsible for surface change of boiling treated ABS, and the selective influence of boiling treatment on the floatability of boiling treated plastics may be attributed to the difference in the molecular mobility of polymer chains. The effects of flotation time, frother concentration and particle size on flotation behavior of simple plastic were investigated. Based on flotation behavior of simple plastic, flotation separation of boiling treatment ABS and PS with different particle sizes was achieved efficiently. The purity of ABS and PS was up to 99.78% and 95.80%, respectively; the recovery of ABS and PS was up to 95.81% and 99.82%, respectively. Boiling treatment promotes the industrial application of plastics flotation and facilitates plastic recycling.     

Application of dissolved air flotation on separation of waste plastics ABS and PS

The aim of this research was to separate waste plastics acrylonitrile butadiene styrene (ABS) and polystyrene (PS) by dissolved air flotation in a self-designed dissolved air flotation apparatus. The effects of wetting agents, frother, conditioning time and flotation time on flotation behavior of waste plastics ABS (w-ABS) and PS (w-PS) were investigated and the optimized separation conditions were obtained. The results showed that when using 25 mgL(-1) tannic acid, 5 mgL(-1) terpineol, 15 min conditioning time and 15 min flotation time, mixtures of w-ABS and w-PS were separated successfully by dissolved air flotation in two stages, the results revealed that the purity and recovery rate of w-PS in the floated products were 90.12% and 97.45%, respectively, and the purity and recovery rate of w-ABS in the depressed products were 97.24% and 89.38%, respectively. Based on the studies of wetting mechanism of plastic flotation, it is found that the electrostatic force and hydrophobic attraction cannot be the main factor of the interaction between wetting agent molecules and plastic particles, which can be completed through water molecules as a mesophase, and a hydrogen bonding adsorption model with hydration shell as a mesophase was proposed.     

Triboelectrostatic separation for granular plastic waste recycling: A review

The world’s plastic consumption has increased incredibly in recent decades, generating more and more plastic waste, which makes it a great public concern. Recycling is the best treatment for plastic waste since it cannot only reduce the waste but also reduce the consumption of oil for producing new virgin plastic. Mechanical recycling is recommended for plastic waste to avoid the loss of its virgin value. As a mechanical separation technology, triboelectrostatic separation utilizes the difference between surface properties of different materials to get them oppositely charged, deflected in the electric field and separately collected. It has advantages such as high efficiency, low cost, no concern of water disposal or secondary pollution and a relatively wide processing range of particle size especially suitable for the granular plastic waste. The process of triboelectrostatic separation for plastic waste is reviewed in this paper. Different devices have been developed and proven to be effective for separation of plastic waste. The influence factors are also discussed. It can be concluded that the triboelectrostatic separation of plastic waste is a promising technology. However, more research is required before it can be widely applied in industry.     

Investigation of hydrocyclones for the separation of shredded fridge plastics

The recycling of fridges produces a mixed plastic product of limited value. In order to maximise its value, the separation of the individual polymers that include high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC) and polyethylene (PE) must take place. The effectiveness of a hydrocyclone system for the separation of these plastics, using both water and calcium chloride solutions, has been investigated. In addition a qualitative procedure for the determination of the HIPS content of a mixed ABS/HIPS product, by selective dissolution in R-limonene, has been developed. It was found that the effective density of separation depended on the particle size and aspect ratio. As the particle size and aspect ratio decreased, the separation became more efficient and the offset between separation density and hydrocyclone medium density decreased. This suggests that, for efficient density separation, closely sized, fine plastic fractions are required. Using these criteria, it was found that the removal of high density plastic such as PVC was readily achieved using a hydrocyclone. A partial separation of HIPS from ABS was found to be possible, taking advantage of a small density difference, using a hydrocyclone medium density of 1035kgm(-3).     

Electrical separation of plastics coming from special waste

Minimisation of waste to landfilling is recognised as a priority in waste management by European rules. In order to achieve this goal, developing suitable technologies for waste recycling is therefore of great importance. To achieve this aim the technologies utilised for mineral processing can be taken into consideration to develop recycling systems. In particular comminution and separation processes can be adopted to recover valuable materials from composite waste. In this work the possibility of recycling pharmaceutical blister packaging has been investigated. A suitable comminution process has been applied in order to obtain the liberation of the plastic and aluminium components. Experiments of electrical separation have been carried out in order to point out the influence of the process parameters on the selections of the different materials and to set up the optimum operating conditions.     

Integrated density concentration and surface treatment for selective separation of plastics from a mixture

Journal of Material Cycles and Waste Management - Froth flotation and elutriation were found to be effective in separating individual plastics from a plastic mixture by exploiting differential...     

Current recycling regulations and technologies for the typical plastic components of end-of-life passenger vehicles: a meaningful lesson for China

China became the largest automotive producer and the biggest automobile market in the world in 2009, but the scrap vehicle recycling industry is still in its beginning stage. Especially, the scrapped plastic parts recycling technology lags behind developed countries. Therefore, in-depth studies on the recycling of automotive plastics are significant and beneficial for environmental protection, energy conservation and the sustainable development of the Chinese automotive plastic industry. In this article, automotive plastic components recycling-related rules and regulations about developed countries and China are discussed first. According to the passenger vehicle plastic part types, the recycling technologies for typical plastic components of end-of-life passenger vehicle are analyzed comprehensively. Based on the combination of contemporary domestic and foreign plastic recycling technology and the result of the current research, the problems and future development for the ELVs plastic recycling industry in China are deliberated, at the same time, some constructive ideas and suggestions for the industry are provided.     

Theoretical and experimental study on the triboelectric separation of ternary plastics combination using fluidized bed

Journal of Material Cycles and Waste Management - Triboelectric separation is an efficiency and promising method to recycle waste plastics. Fluidized bed has been proved an optimal tribocharger...     

Investigation of thermal treatment on selective separation of post consumer plastics prior to froth flotation

Plastics have become the widely used materials because of their advantages, such as cheapness, endurance, lightness, and hygiene. However, they cause waste and soil pollution and they do not easily decompose. Many promising technologies are being investigated for separating mixed thermoplastics, but they are still uneconomical and unreliable. Depending on their surface characteristics, these plastics can be separated from each other by flotation method which is useful mineral processing technique with its low cost and simplicity.The main objective of this study is to investigate the flotation characteristics of PET and PVC and determine the effect of plasticizer reagents on efficient plastic separation. For that purpose, various parameters such as pH, plasticizer concentration, plasticizer type, conditioning temperature and thermal conditioning were investigated. As a result, PET particles were floated with 95.1% purity and 65.3% efficiency while PVC particles were obtained with 98.1% purity and 65.3% efficiency.     

Chemical characterization and toxicity assessment for the sustainable management of end of life cathode ray tubes

Journal of Material Cycles and Waste Management - Cathode ray tube (CRT) monitors represent currently one of the most produced category of electronic waste. In CRTs most of the glass components...     

Microwave treatment combined with wetting agent for an efficient flotation separation of acrylonitrile butadiene styrene (ABS) from plastic mixtures

Journal of Material Cycles and Waste Management - Acrylonitrile butadiene styrene (ABS), as a main component of plastics of waste electrical and electronic equipment (WEEE), shows high potential...     

Trends in waste plastics and recycling

Zero emission is an ambitious project aimed at the conversion of the conventional top-down or one-directional flow type production systems of modern society to those of a recycling type. The basic idea underlying this project is to understand in detail the material flow mechanism in a particular segment of society and to evaluate the transformability of the hitherto one-directional types of process into recycling types. The authors, members of the Zero-Emission Research Group of Japan, are investigating the material flow of plastics in Japan. The present work describes the features of this project, as well as the results obtained so far. Received: May 28, 1998 / Accepted: October 16, 1998     

Glass-ceramics obtained by the recycling of end of life cathode ray tubes glasses

This work is concerned with open-loop recycling of end of life Cathode Ray Tubes glass (an unsolved problem when considering that in Europe almost 90% of EOL electronic goods is disposed of in landfills), focusing on the development of glass-ceramics from panel or funnel glass with dolomite and alumina, and the evaluation of the tendency towards crystallisation with particular attention on composition and thermal treatment. Glasses were melted at a temperature of about 1500 degrees C and transformed into glass-ceramics by different thermal treatments (900 degrees C to approximately 1100 degrees C temperature range and 0.5 to approximately 8h soaking time). By using the evaluation of thermal, mineralogical and microstructural data it has been pointed out that a good degree of crystallisation is reached at about 1000 degrees C and with a high proportion of waste glass (50-75%) if 40-45% of CaO and MgO bearer (dolomite) is introduced. In this way alkaline and alkaline-earth silicate and aluminosilicate mainly develop probably with a surface mechanism.     

Evaluation of material recycling for plastics: environmental aspects

“Zero emissions” is a concept envisaging the creation of a sustainable society with minimal disposal of resources. In order to realize zero emissions for plastics, it is important to establish a method for quantitatively evaluating candidate recycling processes. In this study, the principle of the substitution factor (SF) is introduced. A quantitative evaluation of the recycling process for plastics was then carried out. The production process for monofilament plastics was examined. The recycling of plastics discarded during the production process could be substituted in small amounts for virgin materials, giving reduced CO₂ emissions. Furthermore, production using recycled material mixed with virgin material was more effective in reducing CO₂ emissions than when recycled materials only were used. Received: November 19, 1999 / Accepted: November 28, 2000     

废旧塑料的再生及其在制管行业中的应用

总结了再生、降解、焚烧及填埋等几种废旧塑料处置方式的特点,指出对于品种单一、老化程度低的废旧塑料应优先选择再生利用.重点介绍了废旧聚氯乙烯塑料、聚乙烯塑料、聚丙烯塑料、氯化聚氯乙烯塑料的再生及其在制管行业中的利用情况进展.     

废旧塑料的简易分类方法

塑料制品因其具有质量轻、外观美、加工方便、经济实用等特点而颇受人们青睐,广泛用于各行各业和日常生活用品中,但塑料制品的大量使用也给环境造成了严重污染,消除塑料污染的最积极的办法是对废旧塑料进行回收再利用.塑料种类繁多,不同类别的塑料性质和用途都不相同.介绍几种塑料分类的简易方法,以利于废旧塑料的回收利用.     

日本含氯塑料的再生利用

含氯塑料的使用及再生利用有利于节能减排,介绍了含氯塑料和其再生利用的特性,以及日本含氯塑料的再生利用现状和存在的问题,提出推动再生利用技术开发和构筑高效回收运转体系等应对措施.     

Behaviour of biodegradable plastics in composting facilities

Composting is a preferred treatment strategy for biodegradable plastics (BDPs). In this sense, the collection of BDPs together with organic household wastes is a highly discussed possibility. Under the aspect of the behaviour of BDPs in composting facilities, a telephone survey was carried out with selected composting facility operators. They were interviewed with respect to treated wastes, content of impurities, processes for impurity separation, experiences with biodegradable plastics and assumptions to the behaviour of biodegradable plastics in their facility. Forty percent of the facilities had some experiences with BDPs due to test runs, and also since the occurrence of BDPs in their waste was known. The majority of the operators expressed apprehension regarding an increase of impurities resulting from a combined collection of biowaste and BDPs. In the facilities, measures for the impurity separation from the biowaste were used in common practice - in 33% of the cases, separation of disturbing plastics was done before composting, in 33% after composting, and in 13% before and after composting. The most important separation processes for conventional plastics were sieving and manual sorting. In two cases air classification was also used. When asked about the separation possibility of the conventional but not of the biodegradable plastics in their facilities, the majority of operators were not in a position to comment or they replied that it was not an option. No problems were seen in most cases if the impurity separation follows composting. If impurity separation takes place before composting it was often assumed that the BDPs are mainly separated by sieving. In conclusion, in more than half of the cases, BDPs would not be composted if delivered to a composting facility. Under the actual conditions regarding the collection and the treatment/disposal possibilities, an application of BDPs seems to only be reasonable for clean (i.e., source separated on their own) fractions of BDPs.     

Modelling piloted ignition of wood and plastics

To gain insight in the startup of an incinerator, this article deals with piloted ignition. A newly developed model is described to predict the piloted ignition times of wood, PMMA and PVC. The model is based on the lower flammability limit and the adiabatic flame temperature at this limit. The incoming radiative heat flux, sample thickness and moisture content are some of the used variables. Not only the ignition time can be calculated with the model, but also the mass flux and surface temperature at ignition. The ignition times for softwoods and PMMA are mainly under-predicted. For hardwoods and PVC the predicted ignition times agree well with experimental results. Due to a significant scatter in the experimental data the mass flux and surface temperature calculated with the model are hard to validate. The model is applied on the startup of a municipal waste incineration plant. For this process a maximum allowable primary air flow is derived. When the primary air flow is above this maximum air flow, no ignition can be obtained.