Studies On Chromatographic Separation Of Zirconium And Hafnium Using Macroporous Silica-based Agent Material

The separation of zirconium and hafnium is a global problem. Traditional separationmethods including pyrometallurgical technology and hydrometallurgical technology arereviewed. It indicates that there are still many problems inherent inextricable, such ashigh initial investment, strict material requirements, poor purification ability forpyrometallurgical process and emulsification, phase disengagement and large solventconsumption etc. for solvent extraction as the main method of hydrometallurgicaltechnology. So it is urgently needed to develop environment-friendly separation method.Extraction chromatography is a new rising separation method for its convenience andhigh efficiency in recent years. Combining the high selectivity of solvent extraction andthe high efficiency of column, it has some attractive advantages to separate Zr and Hfsuch as low cost and little pollution.The selection of novel extractants and design of extracion process are very important.Amide extractants have been considered to be the new substitute forphosphorus-containing extractants and have large potential for extraction of f-metalelements. In this paper, an amide extractant and several other kinds of extractants areloaded into silica-based macroporous polymer composite, then their adsorption selectivitytowards Zr and Hf is studies in detail. The main content is as follows:1. Based on silica-based macroporous polymer composite, several kinds of adsorbentswith different extractants were synthesized. The products were characterized by meansof SEM and TG-TDA.2. The effects of acid type, acid concentration, adsorption temperature, contact time,metal ion concentration and solution proportioning etc. on the adsorption behaviorwere studied by batch experiments. The results indicated that the adsorbent which wasloaded N,N,N’,N’-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) had the optimaladsorption capacity in HCl solution and the maximum separation factor was obtainedat the acidity of1.5M HCl. 3. By fitting to different isotherms, kinetic models and calculation of thermodynamicparameters, the adsorption mechanism was analysed. It was found that the processwere spontaneous endothermic reactions with a monolayer adsorption on ahomogeneous surface. Reduction of temperature can increase the adsorption differencefor better separation. The reaction rate was controlled by both intraparticle and filmdiffusion step in chemical reaction.4.Column adsorption data showed that Hf had less breakthrough time and volume thanthat of Zr, which meaned that the adsorbent had more stronger affinity to Zr.Desorption shew that0.5mol/L oxalic acid could elute Zr and Hf effectively.Regeneration date indicated that the column adsorption capacity did not reduceobviously with3times of recycle.