DEVELOPMENT OF A LOW-TEMPERATURE DESILICONIZATION METHOD FOR ZIRCON CONCENTRATE AFTER ACTIVATION WITH NH₄HF₂

The relevance of the research is caused by the expediency of developing a technology for processing zircon concentrates to obtain a concentrate of baddeleyite, which is used for the production of high-temperature ceramics with the possibility of regenerating the main reagent. In this case, the resulting silicon dioxide as a by-product can be used for the manufacture of products from silicate ceramics. The main aim of the research is to determine the maximum degree of desiliconization of the activated zircon concentrate with an aqueous solution of ammonium hydrofluoride to obtain a baddeleyite concentrate; propose a scheme for processing activated zircon concentrate to produce baddeleyite concentrate and silicon dioxide. Objects: ammonium hydrogen fluoride solution, zircon concentrate after thermoactivation, water solution of ammonia. Methods: experimental research, X-ray fluorescence, X-ray crystallography, atomic emission spectroscopy, infrared spectroscopy. Results. The conditions for silicon selective removal from activated zircon concentrate with the production of baddeleyite concentrate as a target product and silicon dioxide as a by-product are determined. The influence of ammonium hydrofluoride concentration in the leaching solution on the degree of desiliconization of the activated zircon concentrate is insignificant. The optimal conditions for leaching are as follows: concentration of NH4HF2 solution - 30 %, duration - 60 minutes, temperature - 90 degrees C; the ratio of solid to liquid is 1:5. Under these conditions, more than 97 % of silicon goes into solution. While the leaching zirconium dioxide partially reacts with the leaching agent to form ammonium heptafluorozirconate, which is less soluble in water than ammonium fluorides and ammonium hexafluorosilicate. Subsequent calcination converts ammonium heptafluorozirconate back into zirconium dioxide. The produced solution of ammonium hexafluorosilicate is used to obtain amorphous silicon dioxide and ammonium fluoride solution, which serves as a raw material in regeneration of the leaching solution with its reuse for processing a new batch of raw materials. Based on the results of the work, a technological scheme for the production of baddeleyite concentrate is proposed. The scheme is characterized by the absence of waste.