The flocculation performance of isodose anionic polyacrylamide (PAM) with different parent solution concentrations (c) for ferric oxide suspension was investigated.It is found that the flocculation performance of PAM could be improved and impaired with the increase of cpemp.Moreover

the concentration of 0.3 g/L is the optimal parent solution concentration (cop) of PAM.Through scaling theory analysis and rheological measurements

cop is proved to approach the critical entanglement concentration (ce).Conductivity test results of PAM parent solution and the conductivity varieties of stirring water added PAM reveal that there exits a charge shielding phenomenon when cp is above cop.The number of PAM effective charges decreases due to the charge shielding

which deteriorates PAM flocculation performance.On the other hand

the flocculation performance of dilute PAM solutions can be enhanced in case of mixing dilute PAM solutions with appropriate amount of -cyclodextrin (CD).There exists intermolecular hydrogen bond between PAM and -CD

which makes several PAM molecules bridged by one -CD molecule.The observed variations of flock sizes and flocculation performance after PAM being bridged can explain the reason of the poor performance for dilute parent solutions

that is

PAM could hardly form flock with ample size and sedimentate sufficiently because the molecules are relatively isolated when the parent solution concentration is below cop.