No abstract

The synthesis of magnesium oxide with high adsorptive properties by the sulfate3ammonia and sulfate3carbonate methods and the effect exerted by the conditions of synthesis of magnesium oxide and hydroxide on their adsorptive activity were studied. The thermograms of the synthesized samples are presented. The activity of the samples, evaluated by the iodine number, was determined in relation to the synthesis conditions.

At the present time, the Satldnsk group of deposits belonging to the 'Magnezit' complex forms the raw material base for the production of magnesia-and magnesia-spinellide refractories in Russia. However, the quality of magnetite mined in the Satldnsk deposit is deteriorating constantly due to increased weight content of the oxides of calcium and silicon.Widening the raw material base for the production of refractories and exploring the possibility of introducing new types of magnesia raw materials into the technological processes are the tasks requiring immediate a~tention. A number of phosphorite and dolomite deposits having large reserves of these minerals can be used for obtaining magnesium oxide by chemical processing of the industrial waste products or the mineralogical raw materials directly.Under laboratory conditions, we worked out the principles of the production technolo~ of magnesium hydroxide from dolomitized waste products obtained when processing phosphate raw materials at the 'Fosforit' Design and Production Complex (KPO). The process was verified and improved under industrial and industrial-test conditions. An experimental batch of the product was developed for carrying out technological testing.The raw materials included the dolomitized tailings obtained during the beneficiation of the dumped (graded) ore at the flotation plant. Their chemical composition was as follows: 25-33%* CaO, 15-18% MgO, 2-4% P205, 30-36% CO 2, 0.5-0.8% F%O 3, 0.2-0.3 % A1203, 0.1-0.2% F, and 3-6% undissolved residue (u.r). Commercial-grade sulfuric acid was used as an acidic reagent and ammoniacal liquor was used as a neutralizing agent. The leaching process of magnesium involves selective dissolution of the components during the interaction of sulfuric acid with the dolomitized tailings of the phosphate raw materials. The optimum pH values (in conjunction with a high rate of decomposition and preferential dissolution of the carbonates) were found to be in the 2.5-4 range. When the degree of extraction of MgO is 75-95 %, the quantity of dissolved phosphorous amounts to 1-5 %.Fig~ares i and 2 show the flow sheet of pilot plant production and the schematic of the location of the equipment and the technological process. Dolomitized tailings of the phosphate raw materials are fed into the reactor from the receiving bunker using a screw feeder (see Fig. 2). Sulfuric acid and water are also introduced into the reactor from the discharge tanks for maintaining the desired liquid-to-solid ratio. The suspension obtained after the stage of leaching is gravity-tEd into another reactor 2 where ammonia-aided neutralization is carried out for removing the impuri}ies of phosphorous, sesquioxides, and silicon from the liquid phase. The neutralized suspension enters the vacuum filter 3 from the reactor 2. The moist filter cake is sent for making building materials and the filtrate is directed into the receiver tank 4 for carrying out additional decontamination and removal of suspended matter. Using a pump 5, the clarified solution is fed ...