Abstract
Triboelectric separation as an inexpensive and environmentally friendly technique could contribute to material-specific sorting. However, the application as a widespread method is limited due to the complexity of the process. In particle wall collisions, various parameters like collision energy and angle, work function of the contact partners, humidity, surface roughness, etc. influence the particle charging in a hardly predictable way. This study investigates the possibilities of forced triboelectric particle charging by applying an electrical potential to the metal contact partner (copper/steel pipe). The variations included different pipe lengths (0.5 m–3 m), particle materials, and particle sizes for limestone. A distinction is made between the net charge of the particles and the positive, negative, and neutral mass fractions. The work functions of the investigated materials vary from about 3.2 eV to >8.5 eV for glass, limestone, artificial slag, and lithium aluminate particles. With the applied high-voltage potential, the particle net charge can be shifted linearly. For limestone, it is shown that the neutral fraction is highest at the Point of Zero Net Charge (PZNC). This observation may identify an approach for the material selective separation of one target component from a multi-material mixture.
Highlights
Academic Editors: Chiharu Tokoro, The phenomenon of triboelectric charging has been known for a long time
The triboelectric charging depends on a large variety of influencing parameters related to the materials used and on the way of contacting the two surfaces that themselves may depend on the environmental conditions such as relative humidity [9,10,11] and temperature [12,13]
To get a rapid overview of the sensitivity of the triboelectric charging on different parameters, the net charge of the powders was measured by an Faraday cup electrometer (FCE) as a function of the applied voltage
Summary
Academic Editors: Chiharu Tokoro, The phenomenon of triboelectric charging has been known for a long time. It can have disastrous effects, such as high-voltage discharges and dust explosions, and offers a number of useful applications, such as in triboelectric nanogenerators (TENG) [1,2,3,4]. The benefits of easy operation, low-energy consumption, and no uptake of water and chemicals are offset by the challenges regarding a limited understanding of the particle charging behavior, where the standard triboelectric series can only be used as a rough orientation [8]. An improved understanding of the triboelectric charging and specific manipulation of the particle charge is needed for an improved separation process. The triboelectric charging depends on a large variety of influencing parameters related to the materials used (work functions, humidity, adsorbates, chemical surface modifications, surface curvature, surface roughness, etc.) and on the way of contacting the two surfaces (number, intensity, and duration of contacts) that themselves may depend on the environmental conditions such as relative humidity [9,10,11] and temperature [12,13]
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