Investigation of tribo-electrostatic separation mechanism for thermoplastics in e-waste based on functional group distribution and surface potential

IF 8.1 1区工程技术 Q1 ENGINEERING, CHEMICAL

Separation and Purification Technology Pub Date : 2025-01-23 DOI:10.1016/j.seppur.2025.131764

Xin He, Zhongxin Zhong, Yixuan Ouyang, Jianbo Wang

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Abstract

With the global dramatic increase in e-waste, recycling thermoplastics in e-waste through tribo-electrostatic separation has become essential. In this study, the internal and external functional group distribution of four typical thermoplastics including polyvinyl chloride (PVC), high impact polystyrene (HIPS), polypropylene (PP) and acrylonitrile–butadiene–styrene (ABS) were analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). A certain degree of oxidation, mainly exhibited as –OH, existed in all thermoplastics. For the first time, atomic force microscopy (AFM) was employed to assess surface potentials of thermoplastics, and their total electronegativity was calculated by integrating the content and electronegativity of various functional groups. The order of surface potential and total electronegativity in four thermoplastics is consistent: PVC (−4.08 V, 2.74) > HIPS (−8.36 V, 2.59) > PP (−9.18 V, 2.57) > ABS (−11.30 V, 2.56). Both content and electronegativity of functional groups in thermoplastics significantly influence surface potential levels. The variations in volume resistivity and relative dielectric constant (RDC) of thermoplastics under different environmental conditions suggested that low relative humidity and low temperature (particularly lower temperature) are more conducive to separation. Effective separation and recycling of binary mixed thermoplastics could be accomplished via tribo-electrostatic method. Thermoplastics with higher surface potential are more inclined to gain electrons and negatively charged, finally enriched in positive electrode. The greater the surface potential difference between two thermoplastics, the higher purity of their separation products. For instance, both positive and negative product purities of the ABS-PVC exceeded 97 % (surface potential difference of 7.22 V).

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基于官能团分布和表面电位的电子垃圾中热塑性塑料摩擦-静电分离机理研究

随着全球电子垃圾的急剧增加，通过摩擦静电分离回收电子垃圾中的热塑性塑料已成为必不可少的。采用傅里叶变换红外光谱（FTIR）和x射线光电子能谱（XPS）分析了聚氯乙烯（PVC）、高冲击聚苯乙烯（HIPS）、聚丙烯（PP）和丙烯腈-丁二烯-苯乙烯（ABS）四种典型热塑性塑料的内外官能团分布。所有热塑性塑料都存在一定程度的氧化，主要表现为-OH。首次采用原子力显微镜（AFM）评价热塑性塑料的表面电位，并通过对各种官能团的含量和电负性进行积分计算其总电负性。表面电位和总电负性的顺序在四个热塑性塑料是一致的:PVC(−4.08 V, 2.74) 祝辞 臀部(−8.36 V, 2.59) 祝辞 PP(−9.18 V, 2.57) 祝辞 ABS(−11.30 V, 2.56)。热塑性塑料中官能团的含量和电负性都显著影响表面电位水平。不同环境条件下热塑性塑料的体积电阻率和相对介电常数（RDC）的变化表明，低相对湿度和低温（特别是低温）更有利于分离。摩擦静电法可以有效地分离和回收二元混合热塑性塑料。表面电位高的热塑性塑料更倾向于获得电子并带负电荷，最终富集在正极。两种热塑性塑料的表面电位差越大，其分离产物的纯度越高。例如，ABS-PVC的正负产品纯度均超过97 %（表面电位差为7.22 V）。

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来源期刊

Separation and Purification Technology 工程技术-工程：化工

CiteScore

14.00

自引率

12.80%

发文量

2347

审稿时长

43 days

期刊介绍： Separation and Purification Technology is a premier journal committed to sharing innovative methods for separation and purification in chemical and environmental engineering, encompassing both homogeneous solutions and heterogeneous mixtures. Our scope includes the separation and/or purification of liquids, vapors, and gases, as well as carbon capture and separation techniques. However, it's important to note that methods solely intended for analytical purposes are not within the scope of the journal. Additionally, disciplines such as soil science, polymer science, and metallurgy fall outside the purview of Separation and Purification Technology. Join us in advancing the field of separation and purification methods for sustainable solutions in chemical and environmental engineering.