barium sulfate insoluble

titanium oxide and 2 per cent' sulphuric acidand 63 per cent water, are slowly added to a solution containing 1050 pounds of barium sulphide, held in a large cylindrical tank, provided with a rotary agitation :capable of producing rapid agitation. The mass isthus v rapidly agitated, and the 2 per cent of sulphuric acid contained in the titanium acid cake reacts with a small portion of the barium sulphide. This reaction may be represented by the following equation TiO H 80 The free sulphuric acid of the titanium acid cake is neutralized by thebarium sul-' phide solution, forming barium sulphate and hydrogen sulphide, as indicated by the above equation. As the sulphuric acid is present only in a small percentage, the major porltiion of the barium sulphide remains as suc very fine colloidal suspension. The barium sulphate produced is also very fine, and the presence of this. very fine barium sulphate in suspension, and also of the very fine colloidal titanium oxide, is believed to be the explanation of the great improvement in the properties of the finished lithopone.

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Titanium dioxide (TiO2) is a multifunctional semiconductor that exists in three crystalline forms: anatase, rutile, and brookite. Owing to an appropriate combination of physical and chemical properties, environmental compatibility, and low production cost, polycrystalline TiO2 has found a large variety of applications and is considered to be a promising material for future technologies. One of the most distinctive physical properties of this material is its high photocatalytic activity (Nam et al., 2019); however, more recently it has attracted growing interest because of its resistive switching abilities (Yang et al., 2008).

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 At present, Lide powder is mainly produced in China. Most of the domestic Lide powder production is still using traditional methods. The main raw materials are zinc oxide, sulfuric acid and barium sulfide (barite and coal are produced by high temperature reduction). Zinc 45% ~ 70%. The traditional method for producing the Liede powder process is to use zinc bakelite containing more than 45% zinc as a raw material to be leached with sulfuric acid to obtain a crude zinc sulfate solution, and then to remove iron by potassium permanganate, and then replace the heavy metal with zinc powder and filter to obtain zinc sulfate. The refined liquid is further subjected to metathesis reaction, pressure filtration, calcination, rinsing, drying, and pulverization with strontium sulfide to obtain a series of different types of lindose powder containing zinc sulfide of 30% or more. The whole process is carried out in an acidic (ra<7) environment, which consumes a large amount of sulfuric acid. The sulfuric acid has strong corrosiveness and requires high production equipment. The final discharged slag is acidic slag, which brings new pollution to the environment. High requirements, high production costs, and poor quality of the products obtained.

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