دانلود رایگان مقاله انگلیسی جداسازی پلاستیک زباله مخلوط از طریق شناوری مغناطیسی - الزویر 2018

abstract

Separation becomes a bottleneck of dealing with the enormous stream of waste plastics, as most of the extant methods can only handle binary mixtures. In this paper, a novel method that based on magnetic levitation was proposed for separating multiple mixed plastics. Six types of plastics, i.e., polypropylene (PP), acrylonitrile butadiene styrene (ABS), polyamide 6 (PA6), polycarbonate (PC), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE), were used to simulate the mixed waste plastics. The samples were mixed and immersed into paramagnetic medium that placed into a magnetic levitation configuration with two identical NdFeB magnets with like-poles facing each other, and Fourier transform infrared (FTIR) spectroscopy was employed to verify the separation outputs. Unlike any conventional separation methods such as froth flotation and hydrocyclone, this method is not limited by particle sizes, as mixtures of different size fractions reached their respective equilibrium positions in the initial tests. The two-stage separation tests demonstrated that the plastics can be completely separated with purities reached 100%. The method has the potential to be industrialised into an economically-viable and environmentally-friendly mass production procedure, since quantitative correlations are determined, and the paramagnetic medium can be reused indefinitely.

4. Conclusion

In this study, magnetic levitation was applied for separating multiple mixed plastics which were simulated using six types of plastics, i.e., PP, ABS, PA6, PC, PET, and PTFE. The experiments were carried out in two segments: (1) initial separation for proving the concept, and (2) two-stage separation for extracting all the plastics. The results show that this process is not affected by particle sizes, as all three size fractions have the similar floating curves during the initial separation. Some floating behaviours are explained using the mathematical expression of magnetic buoyancy force. In the two-stage separation, the material extraction was complete as purity of each type of plastic has reached 100%. The correlation between magnetic field, material density and levitated height is given for potential scale-up of this experimental configuration. Further, the implications of this method are discussed such as recycling WEEE and ELV, as well as its limitations in mathematic model and unexplained assembly in the centreline. For future industrialisation, a unified mathematic model is highly desirable and needed with the purpose of determining the magnets and extraction, since these parameters are largely affecting the cost and energy of this process. This work indicates that separation of multi-plastics is effective and efficiently enabled by the magnetic levitation process, and this provides an environmental and promising approach for mitigating the problem of ever-increasing waste plastic stream.