STUDY ON THE PREPARATION OF TITANIUM DIOXIDE POWDER FOR PRODUCING PIGMENT FROM 85% SYNTHETIC RUTILE (TiO 2 ) Tran Van Son, Cao Hung Thai, Than Van Lien Nguyen Dinh Van, Doan Thi Mo and Hoang Bich Ngoc Institute for Technology of Radioactive and Rare Elements, VAEC, Vietnam. ABSTRACT: Our project has elucidated factors that influence hydrolytic process of titanisulfat solution and bleaching products after hydrolyzing. Appropriate conditions for hydrolyzing such as: concentration of TiO 2 230gTiO 2 /l; temperature of hydrolytic process 100 0 C; and nucleating solution: 1.31% compared with weight of titanium dioxide in the solution has been determined. Appropriate conditions for bleaching process: concentration of sulfuric acid in the solution: 8%; bleaching time: 35 minutes; and temperature of the solution: 80 0 C have also been chosen. After hydrolyzing and bleaching, the sample is dried, calcined at 900 0 C for 2 hours and ground into TiO 2 powder containing 97-98% TiO 2 ; 0.012-0.017% Fe 2 O 3 ; < 0.001% Cr; 0.8-1.44% SiO 2 ; <0.01% Al 2 O 3. Key words: 85% TiO 2 synthetic rutile, titanium dioxide powder 92-98% TiO 2 Introduction Titanium dioxide is used in many fields such as paper, rubber and consumer s goods industries. Besides, it is used for producing paint, coating oil, printing ink, plastics, glass fiber, condensers, ceramics, welding flux, cosmetics, catalyst, soap, toothpaste and so on. Titanium ore in Vietnam has abundant reserves (about 35 million tons). In 2005, output of raw titanium ore was 415.200 tons, 90% of which was exported. However, our current demand for titanium pigment is increasing; we have to import powder of titanium from France and Korea, which has high price. Therefore, it is very necessary to study on producing titanium dioxide powder from 85% synthetic rutile. Experiments and results I. Initial materials Research sample containing 85% TiO 2 synthetic rutile is produced from ilmenite beach sands from Ha Tinh by reducing and removing iron from reduced ilmenite by Becher process, the characteristics of the synthetic rutile are shown in the table 1. Table 1: The characteristics of the synthetic rutile Component TiO 2 Fe Cr Particle size Content, % 85.07 5.15 0.19 < 40 μm The synthetic rutile sample is digested in sulfuric acid, the digested cake is dissolved in 10% sulfuric acid solution. Liquor for hydrolyzing may contain 160 g of TiO 2, 10 g of Fe and 0.1 g of Cr per liter. 270 The Annual Report for 2007, VAEC
2. Study on hydrolytic process 2.1. Effect of hydrolytic temperature TiO 2 solution 210.97g/l is hydrolyzed by heating to 90, 95 and 100 0 C, adding 10ml of nucleus 0.96% compared with weight of titanium dioxide in the solution. After hydrolysis is completed, precipitated hydrolysate is filtered, washed, dried and calcined. The results of experiments are shown in the table 2. Table 2: Effect of temperature on the hydrolytic process Temp, 0 C 90 95 100 TiO 2, % 95.52 95.67 95.78 Fe, % 0.25 0.22 0.15 Cr, % 0.021 0.018 0.014 TiO 2 recovery, % 89.54 89.76 90.47 The experimental results showed that appropriate temperature for hydrolyzing is 100 o C. 2.2. Effect of TiO 2 concentration TiO 2 solutions 171.15; 191.34; 210.97; 230.25 and 249.57g/l are hydrolyzed by heating to 100 0 C, adding 10 ml of nucleus 1.18; 1.05; 0.96; 0.88 and 0.81%, respectively (compared with weight of titanium dioxide in the solution). After hydrolysis is completed, that precipitated hydrolysates are filtered, washed, dried and calcined. The results of experiments are shown in the table 3. Table 3: Effect of TiO 2 concentration on the hydrolytic process TiO 2 conc., g/l 171.15 191.34 210.97 230.25 249.57 TiO 2, % 94.64 94.97 95.78 96.58 96.02 Fe, % 0.35 0.28 0.15 0.09 0.13 Cr, % 0.032 0.027 0.014 0.011 0.013 TiO 2 recovery, % 88.57 89.73 90.47 92.61 95.58 The experimental results show that appropriate concentration of TiO 2 is 230g/l. II.3. Effect of nucleus TiO 2 solutions 230.47g/l is hydrolyzed by heating the solution to 100 0 C, with 0.5, 10, 15, 20 ml of nucleus (corresponding with 0; 0.44; 0.88; 1.31; 1.75% titanium dioxide in the solution). After hydrolysis is completed, that precipitated hydrolysates are filtered, washed, dried and calcined. The results of experiments are shown in the table 4. Table 4: Effect of nucleus on the hydrolytic process Nucleus, % 0 0.44 0.88 1.31 1.75 TiO 2, % 94.14 95.37 96.58 97.85 97.17 The Annual Report for 2007, VAEC 271
Fe, % 0.21 0.12 0.09 0.07 0.082 Cr, % 0.028 0.017 0.011 0.009 0.01 TiO 2 recovery, % 88.56 90.62 92.61 94.24 93.67 The experimental results showed that appropriate amount of nucleus is 15 ml (corresponding with 1.31% titanium dioxide in the solution). 3. Study on bleaching process 3.1. Experimental sample Experimental sample is prepared by hydrolyzing solution TiO 2 230.47g/l at 100 0 C, with nucleus 1.31% (compared with weight of titanium dioxide in the solution). Hydrolytic time is 4 hours. After hydrolysis is completed, the precipitated hydrolysates are filtered and washed to obtain products for bleaching process. The results are shown in the table 5. Table 5: The composition of the sample for bleaching process Component TiO 2 Fe Cr Content, % 97.76 0.07 0.01 3.2. Effect of bleaching acid concentration Experimental samples are washed by 4, 6, 8, 10 and 12% sulfuric acid solution, concentration of TiO 2 200 g/l, temperature 50 0 C, and then add 2g of zinc powder for 1 kg TiO 2, bleaching time is 30 minutes. After bleaching, the sample is filtered, dried and calcined at 900 0 C for 2 hours and ground into TiO 2 powder. The experimental results are shown in the table 6. Table 6: Effect of bleaching acid concentration Acid conc., % 4 6 8 10 12 TiO 2, % 97.87 97.89 97.92 97.95 97.97 Fe, % 0.032 0.030 0.024 0.024 0.022 Cr, % 0.007 0.006 0.005 0.005 0.005 TiO 2 recovery, % 96.32 96.07 95.86 95.54 94.79 The experimental results showed that appropriate acid concentration is 8%. 3.3. Effect of bleaching time Experimental sample is washed by sulfuric acid solution 8%, concentration of TiO 2 200g/l, temperature 50 0 C, add 2g of zinc powder for 1kg TiO 2, bleaching time is 20, 25, 30, 35 and 40 minutes. After bleaching, the samples are dried, calcined at 900 0 C for 2 hours and ground into TiO 2 powder. The experimental results are shown in the table 7. 272 The Annual Report for 2007, VAEC
Table 7: Effect of bleaching time Time, minute 20 25 30 35 40 TiO 2, % 97.86 97.90 97.92 97.96 97.98 Fe, % 0.035 0.028 0.024 0.021 0.021 Cr, % 0.0073 0.0064 0.005 0.0042 0.0042 TiO 2 recovery, % 96.30 96.02 95.86 94.81 94.77 The experimental results showed that appropriate bleaching time is 35 minutes. 3.4. Effect of bleaching temperature Experimental sample is washed by sulfuric acid solution 8%, concentration of TiO 2 200g/l, temperature 50 60, 70, 80 and 90 0 C, add 2g of zinc powder for 1kg TiO 2, bleaching time is 35 minutes. After bleaching, the samples are dried, calcined at 900 0 C for 2 hours and ground into TiO 2 powder. The experimental results are shown in the table 8. Table 8: Effect of bleaching temperature Temp., 0 C 50 60 70 80 90 TiO 2, % 97.96 97.99 98.04 98.09 98.12 Fe, % 0.021 0.019 0.014 0.012 0.012 Cr, % 0.0042 0.0038 0.0024 0.0014 0.0014 TiO 2 recovery, % 94.81 94.67 94.39 94.26 94.32 The experimental results showed that appropriate bleaching temperature is 80 0 C. 4. Proposing a flow sheet for preparation TiO 2 powder from 85% TiO 2 synthetic rutile According to above experimental results, we have proposed the following flow sheet for preparation of TiO 2 powder from 85% TiO 2 synthetic rutile (figure). 85% TiO 2 synthetic rutile Digestion H 2 SO 4 Leaching Dilute acid Filtration Sludge Concentration The Annual Report for 2007, VAEC 273
Hydrolysis Nuclei Filtering & washing Bleaching Filtering & washing Dry & calcination Milling TiO 2 powder Fig. 1: Flow sheet for preparation TiO 2 powder Conclusion 1. The theme has researched factors influencing on hydrolytic process, the experimental results showed that appropriate conditions for hydrolytic process are as follows: concentration of TiO 2 in the solution is 230g TiO 2 /l; temperature of the solution is 100 0 C; nnucleating the solution with 1.31% compared with weight of titanium dioxide in the solution. 2. Factors affecting bleaching process were also researched. Appropriate conditions were determined as follows: concentration of sulfuric acid in the solution is 8%; the bleaching time is 35 minutes; and temperature of the solution is 80 0 C. 3. We have proposed a flow sheet for preparation TiO 2 powder using 1 kg TiO 2 powder containing 97-98% TiO 2, 0.012-0.017% Fe 2 O 3, < 0.001% Cr; 0.8-1.44% SiO 2, <0.01% Al 2 O 3. REFERENCES [1]. Cao Hùng Thái, Nguyễn Đức Hưng, Tổng quan về các hoạt động khoa học công nghệ trong lĩnh vực sa khoáng ven biển. Viện Công nghệ xạ hiếm, Tuyển tập công trình khoa học 1985-2000. [2]. Cao Hùng Thái, Xây dựng quy trình công nghệ nung khử Ilmenit và tách sắt kim loại để thu sản phẩm titandioxit 92-94% TiO 2. Đề tài cấp bộ mã số BO/05/03-01. [3]. Cao Văn Hồng, Viện Nghiên cứu Mỏ và Luyện kim: Định hướng phát triển công nghệ luyện kim, chế biến sâu quặng Titan Việt Nam trong giai đoạn 2006-2010 và những năm tiếp theo. Tuyển tập báo cáo khoa học, Hội nghị khoa học kỹ thuật Mỏ toàn quốc lần thứ XVII. [4]. Hoàng Nhâm, Hoá học vô cơ, Nhà xuất bản Giáo dục. [5]. Nguyễn Đức Vận, Hoá học vô cơ, Nhà xuất bản Khoa học và Kỹ thuật. [6]. Nguyễn Mạnh Khôi, Xây dựng cơ sở sản xuất bột màu TiO 2 200 tấn/năm. Viện Công nghệ xạ hiếm, 1990. 274 The Annual Report for 2007, VAEC
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