Magnetic Separation

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1. Magnetic Separation
1.1 Introduction
Ancient people had already practiced the filtration process in the water treatment long time ago. There is evidenced prove it by the Egyptian and Sanskrit inscription, water was treated using as early as 200 B.C [1]. Perhaps filtration was discovered and used early in the earth removes contaminants from water, by taking advantage of attractive forces between particulate matters suspended in the water and the surface of the filter media. Over the time, the filtration processes have become more complicated and better engineered, but the basic principle remains the same; the efficiency of a filtration process depends on the interaction of forces between the contaminants to be removed and the filter media. The degree to which the attractive forces dominate the repulsive forces determines how efficiently the filter will remove the contaminants. According to the basic principle of filtration, one way to improve separation processes is to strengthen the attractive force between contaminants and filter medium. This strategy underlies the development of magnetic filtration as a useful method for more effective water and wastewater treatment. Magnetic forces being employed for the magnetic filtration as a mechanism to attract contaminants to the filter medium, thereby removing them from wastewater [2]. Thus, the effectiveness of the filtration process is related directly to the strength of the magnetic force. There are factor affected to the strength of the magnetic force which are physical properties of the particle that is volume and magnetic susceptibility and the intensity of the magnetic field gradient around the wire collectors, quantified as the magnetic field density [2]. 1.2How it is being implemented

Basically, magnetic filters could only generate a low intensity field density. That why the application of the technique was limited to removing a large, highly magnetic particles, such as ferromagnetic particle which are very susceptible to a magnetic field. To overcome this problem, the range of potential applications broadened with the development of high-gradient magnetic separation (HGMS).

HGMS can capture smaller (micron sized) particles that are only weakly magnetic paramagnetic just by rising the magnetic field gradient around the filter media and this lead to the expanding the range of application of magnetic separation. When evaluating whether HGMS should be implemented to improve the separation of paramagnetic micron-sized particle, the first thing need to be done is the determination of magnetic filtration result whether it results in superior removal efficiency over non-magnetic mechanical filtration. If magnetic filtration achieves superior removal over alternative method, next step is to design a process which the removal efficiency is maximized. There a lots of commercialization of magnetic separation in the industrial application nowadays. All of them commonly use the advantage of the properties of the magnet of the bulk liquids, as opposed to the particular chemistry of the stabilizing layer. Below are the lists of application of magnetic separation according their field. 1.2.1 Biological separations

Magnetic fluids (or suspension of submicron magnetic particles) have been practical to many different biological systems to split cells and proteins. In most biological separation applications, the magnetic nanoparticles are used as tagging-agents for the biological species, which usually have a insignificant magnetic moment. Cell separation with magnetic particles has been reviewed by Safarik and Safarikova [3]. 1.2.2Environmental separation

A few techniques involving the magnetic particles for environmental separations have been projected and verified at the research level. Commonly these processes use micron-sized particles composed of magnetite that are used as magnetite tagging agents by coating them with a selective adsorbent for...
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