Nanoscale Zero-Valent Iron Coated with Magnesium Hydroxide for Effective Removal of Cyanobacteria from Water

The effects of nanoscale zero-valent iron (NZVI, as a benchmark) and a novel core–shell structured nanoparticle, magnesium hydroxide coated NZVI (NZVI@Mg(OH)2), on the removal and viability of a cyanobacterium, Microcystis aeruginosa, in water were investigated. Dosing of these two nanoparticles at concentrations between 20 and 100 mg/L led to various degrees of sedimentation of cyanobacterial cells from the water column. NZVI@Mg(OH)2 exhibited much better ability to remove cyanobacteria than NZVI. A cell removal efficiency of 86.6% was achieved after 0.5 h with the lowest dosage (20 mg/L) of NZVI@Mg(OH)2, whereas the highest dosing concentration of NZVI (100 mg/L) resulted in the removal of only 57.5% of cells. This improved effectiveness can be attributed to the reduction in electrostatic repulsion between the cyanobacterial cells and NZVI@Mg(OH)2. The membrane integrity of the settled cyanobacterial cells in the sediment was significantly disrupted after the addition of a 100 mg/L dose of NZVI, which m...