Study of Influence of Parameters of Leaching Fluorine from Spent Pot Lining

摘要

In aluminium preparation by means of electrolysis of alumina-cryolite melts one of the largest-scale type of industrial waste is spent pot lining (SPL). Chemical composition of SPL carbon part consists of various elements with fluorine as the main one. One of the solutions of the problem of reducing environmental load by means of storage of waste of this type is extraction of valuable components (such as fluorine), that can be used further for preparation of fluorine entities (cryolite, calcium fluoride), that are brought back to electrolytic process. We have held experiments on extracting fluorine from SPL by caustic liquor leaching under effect of ultrasonic oscillations on a pulp, increasing the degree of fluorine solubilization. By means of mathematical planning method of a factor experiment cross impact of three leaching parameters was stated, maximum concentration of fluorine ions in the solution (20.21 gr/dm~(3)) was achieved in following conditions: NaOH concentration - 2%, solid-liquid ration - 6:1, process length - 90 min. The degree of fluorine extraction from SPL is 69.87%.