Search Results (3)

High-purity fluorene is widely used in optoelectronic materials, biology, medicine, and other fields. It is a kind of industrial chemical with high added value. In this paper, zone melting purification technology was used to study the purification effect of fluorene on the zone travel rate, the zone length, the zone passing number, and the zone temperature difference. The concentration distribution of fluorene and the impurities 2-methylbiphenyl, 4-methylbiphenyl, 4-methyldibenzofuran, and dibenzofunan along the moving direction of the melting zone was obtained. A one-pass zone refining model of fluorene was established; the effective distribution coefficients of the four impurities above were obtained via mathematical software fitting; and the equilibrium distribution coefficients were further calculated, which were 0.2441, 0.5850, 0.2377, and 0.3497, respectively. The k₀ of all impurities was less than 1. The purification effect of fluorene can be improved by using a larger zone length in the initial zone melting purification process, a smaller zone travel rate in the whole zone melting purification process, multiple zone melting purification processes, and a larger zone temperature difference. After four zone melting purification processes, the purity of fluorene increased from 97.62% to 99.08%, which was nearly 1.5% higher than the initial purity of fluorene. Zone melting purification technology provides a new idea for the preparation of high-purity fluorene. Full article

The increasing demand for ultra-high purity aluminum for technological applications has led to the improvement of refining methods in recent decades. To achieve ultra-purity levels (>5N), the common industrial way is to firstly purify aluminum from 2N8 up to 4N8 via three-layer electrolysis, followed by fractional crystallization (usually zone melting). Since both of these methods are very cost- and time-intensive, this paper aims at providing other alternatives of purification. For this purpose, here, the purification of some selected impurities through cooled-finger fractional crystallization method and vacuum distillation have been the focus of this investigation. Both processes are more environmentally friendly than three-layer electrolysis and require less time than zone melting. In this paper, both methods were explored for the aluminum purification. Moreover, the effect of process parameters on the purification efficiency of iron, zinc, and silicon has been investigated. At the end, the effectiveness of the two processes was compared and advantages and disadvantages were summarized. The results showed that the cooling finger process effectively removed iron and silicon impurities, but the removal efficiency of zinc was low. The vacuum distillation process successfully removes zinc in the first stage of distillation. Iron and silicon removal requires additional distillation stages to achieve lower impurity levels. Full article

Aluminum and aluminum-based alloys have been used for many years. In view of the increase in material purity requirements of advanced technology products, research regarding high-purity aluminum has gained significant attention in recent years. In this review, we seek to describe the fundamental purification principles and the mechanisms of various segregation techniques used to produce high-purity aluminum. Moreover, we aim to provide an overview of high-purity aluminum production, with particular emphasis on: (a) principles on how to produce high-purity aluminum by layer- and suspension-based segregation methods; (b) discussion of various influencing process parameters for each technique, including three-layer electrolysis, vacuum distillation, organic electrolysis, suspension-based segregation, zone melting, Pechiney, Cooled Finger, and directional solidification; as well as (c) investigations of fundamental working principles of various segregation methods and corresponding reported end-purification for the production of HP-Al. Eventually, the end-reported product purity, and advantages and disadvantages of various purification methods and technologies are summarized. By analyzing and comparing the characteristics of different methods, we put forward suggestions for realizing efficient and environmentally friendly production of high-purity aluminum in the future. Full article