Concentrating and Reclaiming Magnetic Fluids.
U S Pat 4 435 302 1984 Mar; :
Magnetic fluids (ferrofluids) are recovered by flocculating the magnetic particles with hcl, separating the flocculated particles, and redispersing them with an aqueous nh3 solution, preferably with heating. Thus, 50 ml of 175 g magnetic fluid was mixed with 450 ml h2o to simulate the washer discharge from a density-separation system. The diluted fluid of 17 g saturation magnetization was acidified with hcl, flocculated, filtered, mixed with approximately 5 ml nh4oh, and heated to boiling. The fluid volume was 40 ml and its magnetization was 200 g, stronger than the original.
U.S. Pat. 4,435,302, Mar. 6, 1984; Chem. Abstr. 98:183,212M