2014 Volume 61 Issue S1 Pages S139-S144
Magnetic separation using permanent magnets and/or electromagnets has been increasingly used for purification and recycling of suspended solids and water since the mid 1970's. The objectives behind the development of such magnetic separation systems include purification of kaolin clay in the paper-coating industry, wastewater recycling in the steel industry, and recycling of glass-grinding sludge in the CRT-polishing industry. Due to direct, selective, high-intensity magnetic forces on particles to be separated, the filtering speed of High Gradient Magnetic Separation (HGMS) systems, developed in the 1970's, is now 15–300 times faster than conventional filtration systems. Consequently, magnetic separation is now being applied to a broad class of weak paramagnetic materials, down to submicron particle size. Such HGMS systems have been used for large-scale manipulation of colloidal materials (i.e., up to 50 kg/hr for drainage purification and reuse systems in steel mills). In the 1980's, large superconducting magnets were adopted for field coils of HGMS systems used for kaolin clay purification. After development in the 1990's of less expensive, liquid-helium-free superconducting magnets, national research projects were initiated in Japan, Korea and China to expand their application. A particularly pressing application is the environmental remediation of soil polluted with radioactive particles in Japan.
