<p>Inexpensive flocculant-modified iron tailings sands (ITS) were converted into effective flocculation materials for cyanobacteria blooms. After composite modification with polyaluminum chloride (PAC) and polyacrylamide (PAM), the surface charge of ITS was altered from negative to positive, and surface adhesion was increased by ∼1.5 times. PAC/PAM-modified ITS (PP-ITS) had strong flocculating effects on cyanobacteria, facilitating their removal. When the dosage of PP-ITS was 150 mg/L and the ratio of flocculant to ITS was 1:20, the elimination rate of cyanobacteria was as high as 90%. The flocs formed were better than those with chitosan-modified clays (CS-CA) and PAC-modified ITS (PAC-ITS) in terms of settling velocity, size, and recovery ability. The positively charged groups in the flocculant, such as -NH₂ and Al³⁺, are attracted to negatively charged ions on the surface of ITS, altering the surface charge. Additionally, hydrogen bonds could form between amide side groups, and surface adhesion was improved through molecular association. Coupled with the strong bridging and sweeping effects of the flocculant, the flocs generated by PP-ITS formed rapidly and were large and resilient. The use of PP-ITS could effectively treat cyanobacteria blooms as well as solve the problem of ore tailings disposal. These results are of practical importance for engineering strategies to control cyanobacteria blooms, though there are still some issues that need to be addressed, such as how cyanobacteria flocs are collected and utilized after settling.</p>