A thermodynamic and kinetic study of trace iron removal from aqueous cobalt sulfate solutions using Monophos resin
Background: High purity cobalt has many important applications, such as magnetic recording media, magnetic recording heads, optoelectronic devices, magnetic sensors, and integrated circuits, etc. To produce 5N or higher purity cobalt in an electro-refining process, one of the challenges is to effectively reduce the Fe content of aqueous cobalt salt solution before electrolysis. This paper describes thermodynamic and kinetic investigations of the Fe adsorption process of a new sulfonated monophosphonic resin with the trade mark Monophos. Methods: Five cobalt sulfate solutions of different Co concentrations were prepared. Fe ions were removed from the solutions by ion exchange method using Monophos resin. Chemical analysis was carried out using a Perkin Elmer ICP-OES. Results: The initial Fe concentrations of about 0.9–2.0 mg/L can be reduced to about 0.3–0.8 mg/L, which is equivalent to an Fe removal rate of 60–67%. The Langmuir isothermal adsorption model applies well to the Fe removal process. A second-order type based on McKay equation fits better with experimental data than other kinetic models. The kinetic curve can be divided into two sections. For t < 30 min, particle diffusion may act as the controlling step, whereas chemical reaction may control the Fe adsorption process in the section t > 30 min. Conclusions: Monophos resin is effective for the removal of trace Fe from cobalt sulfate solution. This ion exchange process obeys the Langmuir isothermal adsorption model and the McKay equation of second-order kinetics.
Preparation of high purity cobalt
Abstract A combination of anion exchange separation, electrolytic extraction, floating zone refining and dry hydrogen treatment was used to purify cobalt. The effectiveness of each purification process was confirmed by measurements of the residual resistivity ratio (RRR) and activation analyses. Proton activation analysis revealed that all the main metallic impurities except iron were effectively removed by a combination of these processes. The effective removal of oxygen, nitrogen and carbon by dry hydrogen treatment was confirmed by activation analyses using 3 He ion beams, proton beams and γ rays. It was found that the rate-controlling step in the decarburization process was a surface reaction. The maximum RRR obtained for the purified specimen was 334, which is higher than previously reported values.
Magnetic anisotropy of L11-type (Co1-XMX)50Pt50 (M:Ni, Fe, Cr, Mn) and Co50(Pt1-XPdX)50 ordered alloy perpendicular films
We substituted 3d transition elements M (M=Ni, Fe, Cr, and Mn) for some of the Co, or Pd for some of the Pt, in L11-type Co50Pt50 ordered alloy perpendicular films, and studied magnetic and structural properties. Films were fabricated at a substrate temperature of 360oC using ultra-high vacuum (UHV) sputter film deposition. The order parameter S was almost a constant of about 0.5 when Ni was substituted for some of the Co. The uniaxial magnetic anisotropy Ku and the saturation magnetization, Ms, decreased as the Ni content increased, however, Ku maintained a relatively large value of 1.8x107 erg/cm3 (Ms=570 emu/cm3) even for a Co20Ni30Pt50 composition. In the substitutions of Fe for some of the Co, or Pd for some of the Pt, no significant variation in Ms was observed, however, the rate of decrease of Ku on increasing the Fe or Pd content was larger than when Ni was substituted. The substitution of Cr or Mn for some Co resulted in significant reductions in S, Ms and Ku. Experimental results showed the potential of Co-Ni-Pt ordered films for use in data storage applications, due to their very high Ku potential, relatively low Ms, the relatively low fabrication temperature, and good controllability of the grain orientation.