Contents lists available at ScienceDirect Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm Method to evaluate and prove-the-concept of magnetic separation and/or classification of particles Paulo A. Augusto a,b, ⁎ , Teresa Castelo-Grande a,b , Angel M. Estévez a , Domingos Barbosa b , Paul M. Costa a a APLICAMA, Departamento de Ingeniería Química y Textil, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain b Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal ARTICLE INFO Keywords: Magnetic classification Magnetic separation Design Optimization Magnetic particles Proof of concept Low-cost method Mili and microfluidics ABSTRACT When designing new magnetic separators and/or classifiers or optimizing existing ones, it is usual to face several obstacles: the high cost of a proof of concept full laboratorial setup (including preliminary optimization procedures and/or feasibility demonstrations), time-consuming experiments, lack of flexibility of the assembled laboratorial apparatus, feed complexity, among others. In this work a method and corresponding methodology are proposed to apply in such cases, representing a low-cost, flexible and robust alternative to overcome the mentioned obstacles, from which working parameters of a laboratorial or even larger version of the device may be extrapolated. This represents a powerful tool when designing magnetic separators. In the proposed methodology by determining in one experiment the magnetic force required to separate/classify a particle in a certain point, it may be derived immediately the change in magnitude and shape of the magnetic force index (B B ∇ ) that must exist to separate other particles (with the same or different magnetic susceptibility) in another point, and it is possible to estimate, for example, the optimum, maximum or minimum value of other variables affecting the competing forces (e.g. radius of the particles, fluid density, rotation velocity), and also determine the critical limits of separation by extrapolating and obtaining the magnetic force required in those limits. It represents an open field allowing determining freely the values of the main variables. This methodology and associated method also allow repeating quickly and easily the experiments with different sets of geometrical design and positions. A case study was analyzed and tested for both processes: magnetic separation and magnetic classification, with good results, that allowed to conclude about the feasibility of the system for both processes, and to determine the best configuration geometry. The main objective of the present study was to demonstrate a cheap method and corresponding methodology that may be applied when designing magnetic separators and/or classifiers. 1. Introduction Magnetic separation is a long-established method for the purifica- tion/removal of substances from fluids [1–7], mainly in mining processing industries [8,9]. In the last two decades, high developments were witnessed in application of magnetic separation to biomedical and biological downstream processing applications, mainly due to the development of nanomagnetic functionalized particles [10–16]. Other new applications, like environmental remediation and improvement in chemical processing technologies have also emerged in this century [17]. However, although many different devices have been “proposed” only some of these were developed and even fewer applied commer- cially. Important obstacles have been: time and money spent in preliminary tests; large spectrum of variables that play a role in the process and need to be optimized; feed complexity, among others. In fact, after designing new magnetic separators, a laboratorial-scale set of experiments with the proposed devices is always required. Nowadays there is no established method/methodology/protocol to optimize or test a Proof-of Concept (POC) magnetic separator (or classifier). In fact when intended to test a POC of a magnetic separator/ http://dx.doi.org/10.1016/j.jmmm.2016.10.154 Received 7 September 2016; Received in revised form 25 October 2016; Accepted 27 October 2016 ⁎ Corresponding author at: APLICAMA, Departamento de Ingeniería Química y Textil, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain. E-mail address: pauloaugusto@usal.es (P.A. Augusto). Journal of Magnetism and Magnetic Materials 426 (2017) 405–414 0304-8853/ © 2016 Elsevier B.V. All rights reserved. Available online 08 November 2016 crossmark