Characterization of floc size, strength and structure in various aluminum coagulants treatment

Flocs generated in various aluminum coagulants treatment exhibit difference in size, strength and structure. The formation, breakage and re-formation of flocs were investigated by using a laser diffraction instrument (Malvern Mastersizer 2000, Malvern, UK). Different Al coagulants – conventional Al salt (AlCl3), polyaluminum chloride (PAC-1) and the purified polyaluminum chloride (PAC-2) – were investigated for the coagulation of humic acid (HA). The results showed the properties of HA flocs depend on which species of aluminum used. The monomeric and dimeric aluminum species (denoted as Almono) formed the largest and strongest HA flocs with longest growth time. The HA flocs formed by Al13O4(OH)7+24 (Al13 for short) is the smallest and weakest. The properties of HA flocs made it possible to investigate the relationship between the flocs growth process and aluminum species.

This figure shows formation, breakage and re-formation of HA flocs in different aluminum coagulants treatment. AlCl3 yielded the largest flocs and have better ability to resist shear.Figure optionsDownload as PowerPoint slide