| Kaolin is a kind of class that given priority to with the family of kaolinite mineral composition of clay mineral raw material, named after the deep Jingdezhen kaolin village in Jiangxi province. Quality pure kaolinite is white and delicate, soft soil, it has good plasticity and the physical and chemical properties such as fire resistance. The main mineral composition is consists of kaolinite, halloysite, hydromica, illite and quartz, feldspar and other minerals. The application kaolin is very extensive, it is mainly used for paper making, ceramics and refractory materials, secondly used in paints, rubber filler, enamel glaze and white cement raw material, a few used in plastics, paint, paint, grinding wheel, pencil,daily cosmetics, soap, pesticide, medicine, textile, petrochemical, building materials, national defense and other industries. But as a result of the kaolin mineral contains a lot of organic matter and coloring ions, such as iron, titanium, manganese, seriously affected the ores and the whiteness of the product, make the application scope of kaolin is restricted, lowered its economic value, so, in addition to increase the iron whitening has become an effective way to improve the kaolin application value.Fujian kaolin belongs to soft kaolin clay. The iron content is very high(1.11%), mainly in the form of iron oxide mineral. The whiteness of ore is very low just only 66.4%, which can not be directly used, must be carried out in addition to iron whitening.Using the thiourea dioxide as the reducing agent and oxalic acid as the complex agent, with the existing experimental conditions using simple and low cost iron bleaching process of Fujian kaolin, greatly reduce the content of kaolinite in the non-ferrous materials Fe2O3, increase the whiteness of the product to satisfy the plastic filler, filler of rubber and other industrial applications.The experiment mainly includes three parts:(1)Firstly analyzes the nature of the thiourea dioxide increased temperature, pH, the influence of the concentration and time on thiourea dioxide.The results show that:using thiourea dioxide as the reducing agent to increase the whitening. The highest rate of decline is in the condition of high temperature and alkaline solution and decom position generated a lotof sulfuric acidto show the strong reducibility(2) Examines thepulp density, reduction time, complex, time, pH, the amount of oxalic acid, sulfur dioxide, the amount of urea, and temperature on the influence of bleachingprocess. When the pulp concentration is 20%, reduction time is 15 min, complex time is 15 min, pH = 12, the amount of oxalic acid was 7%, the amount of sulfur dioxide urea was 0.8% and the temperature under the condition of 50 ℃,which is the best condition. The whiteness of kaolin is increased by 66.4%to 85.9% and iron content is increased by 1.11% to 0.44%, which can meet the resin, plastic, rubber and other industrial applications.(3)Using rare earth catalyst to activate urea sulfur dioxide bleach kaolin, The whiteness of kaolin is increased by 66.4%to 89.8%.⑷Using ultrasonic auxiliary urea sulfur dioxide to iron bleaching of kaolin, examines the ultrasonicpower, reduction time, complex, time, dosage of hasty, sulfur dioxide, the influence of urea dosage of bleaching process. The results is concluded that: the ultrasonic power 200 w, the complex time is 10 min,the restore time is 10 min, the dosage of oxalic acid is 6% and the dosage of thiourea dioxide is 0.6%is the best. The whiteness of undressed ore is increased by 66.4% to 87.8%, satisfying the paper making, ceramics and other industrial applications.Using sulfur dioxide urea instead of insurance can not only reduce environmental pollution but also greatly reduce the cost of bleaching. The insurance decomposes toxic sulfur dioxide gas and pollute the environment. The oxidationby-products of thiourea dioxide is sodium sulfate, urea, which is proved to be the wastewater biochemical treatment. |
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