Enhanced treatment properties of iron oxide amended sands coupled with polyelectrolyte to humic acid

To improve the removal efficiency of micropollutant humic acid at low temperature, microflocculation filtration experiments were conducted with homemade iron oxide amended sands (IOAS), cationic polyelectrolyte (CPE) and polyaluminium chloride (PACl). Fractal properties of flocs structures and IOAS surface and their effects on the removal efficiency of humic acid were investigated. Results showed that IOAS had a porous surface with fractal dimensions (D) (D = 1.744) and a strong adsorption capacity for humic acid. The flocs produced by PACl were small in size, loosely packed with a higher D, and therefore settled slowly. By contrast, the formed flocs by adding CPE with only 1~5% of PACl had strong and open structures with a high effective density, rapid settling velocity and a lower D. Compared with PACl flocs, the larger size CPE flocs and PACl+CPE flocs deposited and packed up on IOAS, creating smaller pores and resulting in a lower D and higher filtration capacity.