Sorption of palladium(II), rhodium(III), and platinum(IV) on Fe3O4 nanoparticles

Abstract The adsorption of palladium(II), rhodium(III), and platinum(IV) from diluted hydrochloric acid solutions onto Fe 3 O 4 nanoparticles has been investigated. The parameters studied include the contact time and the concentrations of metals and other solutes such as H + and chloride. The equilibrium time was reached in less than 20 min for all metals. The maximum loading capacity of Fe 3 O 4 nanoparticles for Pd(II), Rh(III), and Pt(IV) was determined to be 0.103, 0.149, and 0.068 mmol g −1 , respectively. A sorption mechanism for Pd(II), Rh(III), and Pt(IV) has been proposed and their conditional adsorption equilibrium constants have been determined to be log K = 1.72 , 1.69, and 1.84, respectively. Different compositions of eluting solution were tested for the recovery of Pt(IV), Pd(II), and Rh(III) from Fe 3 O 4 nanoparticles. It was found that 0.5 mol L −1 HNO 3 can elute all of the metal ions simultaneously, while 1 mol L −1 NaHSO 3 was an effective eluting solution for Rh(III), and 0.5 mol L −1 NaClO 4 for Pt(IV). In competitive adsorption, the nanoparticles showed stronger affinity for Rh(III) than for Pd(II) and Pt(IV).