1. Iron concentrate contains other substances, such as non-magnetic metals or other impurities. In the process of magnetic separation, although some impurities can be separated, it is difficult to completely separate them, so the total iron content of iron concentrate will be reduced.
2. It is possible that the iron concentrate itself is magnetically separated due to improper setting or treatment of magnetic separators during magnetic separation, which leads to the decrease of the total content of iron concentrate.