Regulation of hydrogen bonding on microbubble flocs in the hybrid ozonation-coagulation (HOC) process enhances organic matter removal

The separation zone in flotation is generally considered the site of solid-liquid separation of insoluble particles. However, the residual dissolved organic matter (DOM) can be effectively removed in the separation zone of the hybrid ozonation-coagulation (HOC) process was firstly discovered. DOM removal in the separation zone was mainly attributed to the in-situ formation of microbubble flocs mediated by the interaction between ozone and flocs. Ozone can regulate the oxygen containing groups on the surface of flocs, which induces formation of multilayer reaction sites. Hydrogen bonding to polar oxygen containing groups on microbubble flocs was the dominant driver of DOM removal, and –COOH and –OH were identified as the surface hydrogen bond donors. This indicated that the hydrogen bond reaction can be enhanced by the modification of ozone for flocs in the separation zone. Furthermore, surface hydroxyl groups formed by the Al acted as active sites for the connection between ozone and flocs. Ozone accelerated the transformation of tetrahedral Al to octahedral Al in flocs, which can enhance microbubble flocs generation. Moreover, microbubble floc-HA, a flotation product, exhibited higher surface hydrophobicity than conventional flocs, which resulted in high flotation efficiency.