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熔盐法钛白清洁工艺中硫酸氧钛溶液的制备和水解机理的研究
Alternative TitlePreparation of Titanyl Sulfate Solution and Mechanism of Titanium Hydrolysis in NaOH Roasting Method
王伟菁
Subtype博士
Thesis Advisor齐涛
2014-04
Degree Grantor中国科学院研究生院
Degree Discipline化学工艺
Keyword熔盐法   二氧化钛   酸溶   水解   动力学
Abstract钛盐工业是冶金的基础原料工业,90%以上的钛矿用于生产颜料级二氧化钛(钛白粉)。二氧化钛具有无毒无害、强遮盖性能、高白度和高耐候度等特点,因此广泛应用于涂料、塑料、造纸、化纤、橡胶和化妆品等行业。鉴于传统钛白粉生产工艺中硫酸法三废高,氯化法能耗高毒性大的问题,目前提出了一种原料适用性强、原子利用率高、介质可循环和产品可调控的碱熔盐法钛白清洁生产的新技术。该技术主要包括五大步骤:(一)碱熔:高钛渣或天然金红石与NaOH混匀在500?C煅烧制备钛酸钠α-Na2TiO3。(二)洗涤:α-Na2TiO3通过三次水洗和一次酸洗获得酸溶前驱固体NaxH2-xTiO3。(三)酸溶:NaxH2-xTiO3被酸解生成硫酸氧钛溶液(俗称钛液)。(四)水解:钛液中硫酸氧钛脱水缩聚制备白色沉淀偏钛酸(HTD)。(五)煅烧:盐处理的HTD程序升温至850?C~1000?C合成颜料二氧化钛。其中水解过程是新技术制备高品质颜料级二氧化钛的关键控制环节,没有相关工艺和机理的文献报道。所以本文系统研究了以高钛渣为原料的碱熔盐法钛白生产工艺中硫酸氧钛溶液的制备和水解过程,分析了传统六大因素对水解过程和产物偏钛酸性质的影响,优化硫酸氧钛传统水解机理并推导出水解本征动力学模型。同时详细研究了废酸循环工艺和杂质累积规律,成功用聚乙二醇改性和盐处理耦合法制备出纯度优于传统法的颜料级二氧化钛。本文主要研究成果和创新如下: (1)确定洗涤工艺的前驱体α-Na2TiO3的晶型结构。通过碱熔产物XRD谱图中58?副峰和40?主峰的峰强比,确定洗涤前驱体是六方晶系Na2TiO3。 (2)稀酸洗涤工艺与宏观动力学研究。系统考察了搅拌方式、搅拌时间、搅拌速度、液固比、温度和洗涤酸度(pH)等对钠离子去除率、钛损失率和酸洗产物结构的影响,获得优化的酸洗除杂工艺条件;除杂宏观动力学研究表明,酸洗过程是外扩散控制的离子交换过程,各个影响因子权重如下:pH值 > 液固比 > 搅拌方式 > 时间 > 温度。 (3)构建硫酸- 酸洗料NaxH2-xTiO3反应新体系。系统研究了硫酸分解酸洗料NaxH2-xTiO3即酸溶过程的热力学、工艺和宏观动力学,结果表明,酸溶过程为内扩散控制,表观活化能为28.69 kJ/mol。相对硫酸法酸解工艺,新工艺酸溶过程具有低温温和、原子利用率高、酸耗低等优势。 (4)建立熔盐法硫酸氧钛溶液(俗称钛液)水解本征动力学模型。采用红外/拉曼光谱分析硫酸氧钛水解制备偏钛酸的过程,获得SO42-存在下钛液的水解机理,推导水解本征动力学方程式并用于实际钛液的水解拟合。水解动力学研究表明,钛液中钛、硫酸和水浓度是影响水解的关键参数,该过程分为诱导期、生长期和团聚期三个阶段。通过研究得到五种主要杂质(Na、Fe、Si、Mg、Mn)对钛液水解过程的影响规律。 (5)确定熔盐法硫酸氧钛溶液水解过程优化工艺条件。系统考察了水解晶种制备方法、晶种熟化时间、晶种添加量、温度、搅拌速度、钛液钛浓度、钛液酸度、钠钛比、活性添加剂等因素对水解率和偏钛酸粒度的影响,获得优化的水解工艺条件。确定BET表征方法是统一熔盐法和传统硫酸法制备的偏钛酸粒度的有效方法。 (6)研究偏钛酸的煅烧活性和酸介质的循环。从聚乙二醇(PEG)添加量和煅烧温度两方面考察改性偏钛酸的煅烧活性,采用PEG 改性和盐处理耦合法成功制备出高纯度钛白产品。酸介质循环实验确定杂质积累规律,并采用扩散渗析膜分离法实现酸介质循环和杂质分离。
Other AbstractTitaium salt industry is one of the fundumental metallurgy industries. 90% of titanium dioxide (TiO2) has been widely used as pigment in paper, textiles, leather, and porcelain, while the rest 10% used as photocatalyst in water treatment and as sensor in enviromental monitoring. There are two main commercial manufacture methods: sulfate and chloride route. The chloride method is energy intensive and generates toxic dioxines to cause serious environmental problem. The sulfate process where low-grade ilmenite is employed as the feed materials brings more serious environmental wastes such as dilute sulfuric acid and copperas. For these reasons, a novel process, namely the NaOH roasting method, was recently proposed to realize wide titanium resources, high titanium extraction, recyclable reaction medium, and controllable TiO2 production. This new process includes five key steps: (1) Roasting. The titanium slag blended with NaOH is roasted at 500?C and titanium is converted to α-Na2TiO3. (2) Leaching. The roasted solids are leached by pure water and diluted sulfuric acid to obtain the NamH2-mTiO3 filter cake by filtration. (3) Dissolution. The NamH2-mTiO3 is dissolved by sulfuric acid to generate concentrated titanyl sulfate solution. (4) Hydrolysis. Hydrated titanium dioxide (HTD) is precipitated by heating titanyl sulfate solution at boiling point. (5) Calcination. The coating HTD is clacinated to obtain the final TiO2 production. Similar to the sulfate process, hydrolysis is an essential step to control the structure of HTD in this new process, and in turn decides the TiO2 pigment quality. However, the titanium hydrolysis in concentrated solution, especially the mechanism is rarely reported in the literature and is very significant for the development of this new process. The research is about the preparation and the hydrolysis of the titanyl sulfate solution. In addition, the acid cycle, the accumulation of impurities, and the modification of HTD were further researched to supplement the hydrolysis process. The results and innovative progresses are obtained as follows: (1) The crystalline structure of α-Na2TiO3 obtained from the NaOH roasting with high titanium slag was confirmed by the peak strength ratio of assistant peak (58o) to main peak (40o), which coincided with the information of Rhombohedral Na2TiO3 ( I(012)/I(110) = 0.26). (2) The conditional optimization and macroscopical kinetics of leaching were studied. The effect of stirring method, stirring time, stirring speed, mass ratio of liquid to solid, temperature and pH value on the impurity removal ratio and the structure of NaxH2-xTiO3 were systematically studied. The kinetics of leaching process is an ion exchange process controlled by diffusion in product layer. (3) A novel reaction system of diluted sulfuric acid and NaxH2-xTiO3 was established with systematical thermoldynamic and kinetic researches. The kinetic result indicates that the titanium dissolution process is in the shrinking core model controlled by diffusion in product layer with the apparent activation energy of 28.69 kJ/mol. (4) The proposed mechanism of the hydrolysis with the role of SO42- was investigated by using FTIR and Raman spectra. The intrinsic kinetics model of the hydrolysis in titanyl sulfate solution was established on basis of the mechanism and further the model parameters of reaction constant k was successfully aggressed from the experimental data. The hydrolysis effect of the concentrations of the impurities, such as sodium, ferrum, silicon, magnesium, and manganese on the hydrolysis percentage and the particle mean size were systematically studied. (5) The hydrolysis process was systematically optimized with the effects of seeding preparation, seeding time, the dosage of seed, temperature, stirring speed, initial titanium concentration, initial acid concentration, Na/Ti mass ratio, and surface active agent on the hydrolysis percentage and the particle mean size of the hydrated t
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/15518
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
王伟菁. 熔盐法钛白清洁工艺中硫酸氧钛溶液的制备和水解机理的研究[D]. 中国科学院研究生院,2014.
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