Influence of operating parameters on the performance of magnetic seeding flocculation

In the present study, magnetic seeding flocculation was applied to remove copper (200 mg/L) and turbidity (180 mg/L) from simulated microetch copper waste. Fe3O4 particles (40 to 1600 mesh) were used as magnetic seeds. Poly-aluminum chloride (PAC) and anionic polyacrylamide (PAM) were added as coagulant and flocculant, respectively. The effect of operating factors, such as the dosages of the coagulant and flocculant, initial pH of the wastewater, and dosage and size of the magnetic seeds, on copper and turbidity removal was systematically investigated. In addition, settling speed, floc-size distribution, and volume of sludge were measured with and without the addition of magnetic seeds to compare the efficiency of magnetic seeding to that of traditional flocculation. The results indicated that the highest settling speed, the largest floc size, and the smallest volume of sludge were obtained simultaneously when the dosage and size of magnetic seeds were 2.0 g/L and 300-400 mesh, respectively. High removal efficiencies of 98.53 and 94.72 % for copper and turbidity, respectively, were also achieved under this condition; values that are 4.11 and 0.61 % higher, respectively, than those found in traditional flocculation. The high performance might be attributed to efficient collision of particles and slightly moderate vortex centrifugal force of inertia among the magnetic seeds, which could produce larger magnetic flocs with lower moisture.