Iron removal from clayey weathered granite using magnetic separation and classification.

Abstract

Weathered granite has been expected to be an alternative material for potteries. Weathered granite, known as “Ao-saba”, contains kaolin clay at around 10 % and this kaolin clay can be recovered by elutriation. However, elutriation residue contains colored minerals like biotite containing iron, which is not appropriate for raw materials for potteries. To use elutriation residue as raw materials, colored minerals have to be removed. This study applied classification and magnetic separation to removal of colored minerals from clayey weathered granite. Classification tests revealed that colored minerals like biotite were only contained in a smaller grain group of elutriation residue. This result meant that classification was effective for recovery of a bigger grain group of elutriation residue where colored minerals did not exist. Then, magnetic separation tests were conducted to remove biotite from a smaller grain group of elutriation residue. In magnetic separation tests, colored minerals were completely removed from any size of elutriation residue. Therefore, it was demonstrated that classification and magnetic separation were an effective method for iron removal from clayey weathered granite.