Contamination of quartz by iron in energy-intensive grinding in air and liquids of various polarity

Abstract

The influence of mill power and grinding environment on the contamination of quartz by iron during vibration grinding was studied. It was found that the Fe content of ground powders increased with an increase in specific grinding energy that was independent of the conditions of energy supply, that is whether it was supplied by varying the mill power or the grinding time. The specific contamination expressed as the ratio of Fe content to newly created surface area depended upon the physical properties of the grinding environment. The influence of grinding conditions on the state of the iron in the products of grinder wear was investigated by Mössbauer spectroscopy and by measuring the magnetic susceptibility of the ground powders. It was shown that the iron produced from grinder wear is present in tow main forms: as a magnetically ordered form identical with the basic material of the grinder and in a form of finely dispersed iron/iron compound showing superparamagnetic behaviour. Based on the results obtained, the formation of a silica-supported iron or iron oxide catalyst was presumed. By this assumption, the catalytic decomposition of water and methanol that takes place during quartz at grinding by iron containing grinders can be explained.