Effects of electrostatic neutralization of Keggin Fe13 on the removal of micro and nano plastic

The successful preparation and identification of Keggin-structure Fe clusters in recent years further enriched the potential application scenarios of ferric coagulants. Comparing the coagulation efficiencies and mechanisms of Fe in the removal of nano/microplastics with conventional polymeric Al and monomeric Al/Fe, this work aimed to elucidate the coagulation behaviour of Fe compared with the traditional mono ferric coagulant, which has the coagulation applied bottleneck of quick and violet hydrolysis. The results showed that Fe has a similar electrostatic neutralization potential to Al, which could keep a positively charged species, especially in acid conditions. The Fe species has a selective removal potential toward the microplastics with a polar functional group like ester. Moreover, Fe could hydrolyze to form active sol-gel hydroxides in neutral and alkalinity conditions, which is like the behaviour of traditional monomeric Fe coagulants but seldom restabilization. The electrostatic neutralization of Fe could enhance the removal of nano plastic from - 25-75% compared with monomeric Fe at pH 4. The higher floc density as a monomeric Fe coagulant and better electrostatic neutralization potential of Keggin Fe posed a good prospect for Fe to replace the monomeric Fe coagulants in conventional coagulation.