title: Adsorption of precious metals in water by dendrimer modified magnetic nanoparticles.
abstract: Magnetic nanoparticles modified by third-generation dendrimers (MNP-G3) and MNP-G3 further modified by ethylenediaminetetraacetic acid (EDTA) (MNP-G3-EDTA) were conducted to investigate their ability for recovery of precious metals (Pd(IV), Au(III), Pd(II) and Ag(I)) in water. Experiments were carried out using batch reactors for the studies of adsorption kinetics, adsorption isotherms, competitive adsorption and regeneration. The pseudo second-order model is the best-fit model among others suggesting that the adsorption of precious metals by MNP-G3 in water is a chemisorption process. Three adsorption isotherms namely Langmuir, Freundlich and Dubinin-Radushkevich isotherm were examined and the results showed the similarities and consistency of both linear and nonlinear analyses. Pd(IV) and Au(III) with higher valence exhibited relatively better adsorption efficiency than Pd(II) and Ag(I) with lower valence suggesting that the adsorption of precious metals by MNP-G3 is a function of valence. In the presence of the competing ion Zn(II), the adsorption efficiency of MNP-G3 for all four precious metals was declined significantly. The use of MNP-G3-EDTA revealed an increase in the adsorption efficiency for all four precious metals. However, the low selectivity of MNP-G3 towards precious metals was not enhanced by the modification of EDTA onto the MNP-G3. The regeneration of metal-laden MNP-G3 can be readily performed by using 1.0% HCl solution as a desorbent solution.
authors.affiliation: Institute of Environmental Engineering, National Chiao Tung University, 300 Hsinchu, Taiwan.
authors.forename: Chia-Hsin
authors.initials: CH
authors.lastname: Yen
authors.affiliation: Department of Civil and Environmental Engineering, National University of Kaohsiung, 811 Kaohsiung, Taiwan. Electronic address: lien.sam@nuk.edu.tw.
authors.forename: Hsing-Lung
authors.initials: HL
authors.lastname: Lien
authors.affiliation: Department of Civil and Environmental Engineering, National University of Kaohsiung, 811 Kaohsiung, Taiwan.
authors.forename: Jung-Shing
authors.initials: JS
authors.lastname: Chung
authors.affiliation: Institute of Environmental Engineering, National Chiao Tung University, 300 Hsinchu, Taiwan.
authors.forename: Hund-Der
authors.initials: HD
authors.lastname: Yeh
keywords: Adsorption; Dendrimer; Magnetic nanoparticles; Nanotechnology; Precious metals