Physicochemical processes that occur in mechanical activation of kaolinite in centrifugal-planetary mills in the presence of concentrated sulfuric acid were studied. A scheme of formation of aluminum sulfate in the course of acid activation was analyzed.The constant rise in the consumption of metallic aluminum, alumina, and other products formed in processing of aluminum-containing raw materials results in an increase in the share of unconventional, secondary, and technological kinds of raw materials involved in the processing procedures [1]. Kaolinites have long attracted the researchers' attention as a promising raw material, which can be successfully processed with mineral acids and, in particular, sulfuric acid [2].Sulfuric acid methods for processing of layered aluminum-containing silicates have been intensively developed since the middle of the last century as a promising area of research. The common feature of various kinds of these techniques is the stage of preliminary activation of a raw material, which is performed in autoclaves or by a thermal or thermochemical method.In the course of a thermal activation, kaolinite loses the most part of its structural water and passes into a metastable state, which makes it possible to extract Al(III) with hot H 2 SO 4 solutions. The thermochemical activation of kaolinite is performed by its treatment with sulfuric acid at elevated temperatures, which leads to disintegration of the structure of the mineral and to formation of Al 2 (SO 4 ) 3 crystal hydrates [3].The elevated pressures and temperatures used in these kinds of activation are technologically and environmentally dangerous, impose strict requirements to the equipment employed, and lead to an increase in the number of process procedures and, in the end, to a higher cost of the product [4,5].The mechanical activation of kaolinite in centrifugal-planetary mills with high specific energy supplied to a substance being activated has demonstrated a high efficiency. This method yields, at a short time of activation, a product with a high reactivity, whose processing with acid solutions under moderate heating results in virtually complete recovery of Al(III) in the form of a sulfate [6].Previously, a method has been suggested for mechanochemical activation of kaolinite in AGO mills in the presence of concentrated H 2 SO 4 [7,8]. The method provides virtually complete extraction of Al(III) from the product in the form of a sulfate with water without heating. This technique ensures environmental safety of processing of the raw materials because the amount of solid products formed is at a minimum and the acidity of wastewater is low.In this work we studied physicochemical processes occurring in dry mechanical activation of kaolinite and its combined mechanochemical activation in the presence of concentrated H 2 SO 4 . EXPERIMENTALWhite kaolinite from the Puzla deposit, Komi Republic, was used in the study. According to the results of elemental analysis, the kaolinite contains the following components (wt %): 37.2 Al 2...

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