Performance of tribocatalysis and tribo-photocatalysis of pyrite under agitation

Pyrite (FeS2) is an abundant natural mineral with photocatalytic activity that can be used to degrade pollutants. However, the low efficiency of the photogenerated electron–hole pair separation of pyrite affords poor degradation performance, thereby limiting its applications in catalysis. Introducing tribocatalysis in a pyrite photocatalysis process is a potential method for enhancing the catalytic effect of pyrite to use it as an alternative for expensive and complex synthetic catalysts. In this work, the tribocatalytic and tribo-photocatalytic performances of natural pyrite were systematically studied. Under magnetic stirring, a removal rate of 95% for methylene blue (MB) was achieved via tribocatalysis for 48 h and via tribo-photocatalysis for 3 h, respectively. Tribo-photocatalysis was realized through the stacking effect of tribocatalysis and photocatalysis, which constituted 37.5% and 62.5% of MB removal, respectively. The main reactive oxygen species of the tribocatalysis reaction was •OH, as proved using free-radical trapping experiments, and the •OH was mainly produced by the Fenton reaction that occurred after the friction between pyrite and PTFE rotor. Natural pyrite can collect the tiny mechanical energy and light energy in the environment to effectively degrade the dyes, such as MB, rhodamine B and so on. Although the types of pollutants currently explored are limited, the advantages of non-toxic, high stability and extensive resources exhibited by pyrite catalyst make it has great application potential in the fields of self-power purification in natural environment and self-cleaning system in industry.