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Click to add WeChatThe chemical production and processing of kaolin clay uses chemicals to selectively dissolve the iron impurities present in kaolin clay, and then removes the iron. There are mainly oxidation method, reduction method, oxidation-reduction method, acid solution method and chlorination method.
The kaolin oxidation purification method mainly uses a strong oxidant (sodium hypochlorite) under weakly acidic conditions. The iron impurities in kaolin are oxidized into water-soluble ferrous ions, which are then filtered and washed to complete the separation and purification. This method is mainly suitable for the separation of minerals containing pyrite impurities in kaolin.
The kaolin reduction production method is to use a reducing agent to reduce the insoluble iron impurities in the trivalent state of kaolin into soluble divalent iron ions, and then After filtering and washing, the selection is completed. There are three commonly used methods: insurance powder method, thiourea dioxide method and acid-soluble hydrogen method.
Insurance powder method: It uses sodium dithionite as a reducing agent to reduce iron oxides into soluble iron ions. However, this method should be washed and filtered in time, otherwise ferrous iron Will be re-oxidized and turn yellow.
Thiocarbamide dioxide method: First heat the thiourea dioxide in an alkaline medium, use a strong sound field to reduce the sulfuric acid, and then reduce the ferric iron in the kaolin to dicarboxylic acid. Valence soluble iron and remove it. This method can only produce strong reducing sulfuric acid under high temperature and strong alkali conditions.
Acid-dissolved hydrogen method: Utilize the displacement reaction between active metals and acid solvents (sulfuric acid, hydrochloric acid, oxalic acid), and the generated hydrogen will reduce the ferric iron in kaolin to divalent iron , and then complete the iron removal. This method is mainly used to select minerals whose whiteness of kaolin is lower than 70°.
Most kaolin minerals contain both divalent and trivalent iron, so they need to be purified through the oxidation + reduction method. First use an oxidizing agent to oxidize ferrous iron to ferric iron, then use a reducing agent to reduce ferric iron to dissolved ferrous iron, and then complete iron removal through filtration and washing. This method has a good bleaching effect on kaolin containing a small amount of disseminated and star-shaped iron impurities.
The acid dissolution method is to convert the insoluble iron impurities in kaolin into soluble substances in an acidic solution, and then filter and wash the kaolin to achieve Separation of impurities. In acid solutions, sulfuric acid can cause kaolinite lattice destruction, so hydrochloric acid and oxalic acid are often used.
The chlorination method to process kaolin is to add chlorine salt for high-temperature roasting under the action of carbon to convert the iron oxide into chloride. As the melting point decreases, CO and CO2 airflow overflows to achieve iron removal and whitening of kaolin. During the chlorination process of this method, chloride solid particles will be produced.
The above 5 methods are methods of chemical beneficiation of kaolin. In actual mineral processing plants, kaolin has different selection processes due to differences in its own ore properties. A suitable process plan should be designed according to its ore characteristics. , can you get the ideal kaolin product.
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