磷灰石的形貌控制及其在环境净化中的应用
文献类型：学位论文
| 作者 | 朱荣海 |
| 学位类别 | 博士 |
| 答辩日期 | 2010-01-11 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 王丹 |
| 关键词 | 磷灰石 形貌控制 重金属离子 选择性催化还原 |
| 其他题名 | Morphology control of apatite and its applications in envionment purification |
| 学位专业 | 化学工程 |
| 中文摘要 | 磷灰石是一种天然矿物材料，在自然界中广泛存在。磷灰石化学性质稳定，具有良好的表面化学性质和离子交换性质，在硬组织修复、药物缓释、无机抗菌剂、生化分离介质、水处理和催化等领域具有广泛的应用。磷灰石的宏观性质与其形貌、尺寸、组成等密切相关，但是现有的技术对这些方面的调控还存在明显的不足，在一定程度上限制了磷灰石的应用。因此，磷灰石的形貌调控及其应用成为了当前的研究热点。本论文采用液相合成方法，发展了磷灰石的形貌调控方法，制备了形貌与组成各异的磷灰石材料，并研究了磷灰石在重金属离子吸附和选择性催化还原NOx方面的应用。主要结果如下：（1）采用共沉淀法，制备了直径在2~15 μm范围内由纳米棒组成的球形羟基磷灰石颗粒和锶取代球形羟基磷灰石颗粒。该方法具有过程简单、粒径分布均匀和球形度好等优点。采用均相共沉淀法制备了由直径为100~500 nm的棒状物组成的粒径在25~82 μm的类球形羟基磷灰石颗粒。均相共沉淀法制备类球形羟基磷灰石反应体系中，添加一定量的NaF可以制备粒径分布均匀的、椭球状的、氟取代的磷灰石。添加NaF以后，可以极大的提高磷灰石相的形成速度。（2）在水热反应温度为200℃下， pH值为9.7、EDTA/Ca的摩尔比为1时，可形成形貌规则、尺寸较大的棒状羟基磷灰石。以水和DMF为混合溶剂，添加PEG1000，在水热反应条件下机械搅拌可以得到由纳米棒组装而成的毫米级空心球形羟基磷灰石颗粒。（3）在一定吸附时间内，球形羟基磷灰石对Cd2+的吸附量比传统块状材料大。吸附量随Cd2+浓度增加而增加，符合弗罗因德利希吸附等温式。Cd2+的吸附量随着pH值增加而升高。脱附剂的pH值越低则Cd2+的脱附量越大，采用pH值为2.88的冰醋酸溶液为脱附剂时，脱附量为26.53%。羟基磷灰石对各种金属离子吸附能力强弱的次序依次是：Pb2+> Cu2+> Cd2+> Zn2+ > Ni2+。共沉淀法和水热法制备羟基磷灰石的比表面与吸附量均成线性关系，并且水热法制备的羟基磷灰石的吸附能力明显高于共沉淀法制备的样品。（4）羟基磷灰石负载Cu的催化剂在中低温范围内对NH3选择性催化还原NOx的效果较好。催化剂中Cu的含量大于2.24%时，在中低温区间反应活性差别很小。增加反应体系中O2浓度、烟气流量和水的存在都会降低催化活性。DRIFTS结果表明，气态的NO(g)与吸附态的NH2(a)反应生成NH2OH(a)的过程是该反应的速度控制步骤。O2可以与NOx在催化剂的表面形成稳定的硝酸盐物种而占据一定的活性中心，影响NH3在催化剂表面的吸附，从而降低催化剂的反应活性。 |
| 英文摘要 | Apatite is a type of widely existing natural mineral material. Apatite has excellent chemical stability, surface property and ion-exchanged property and has been widely used in the field of hard tissue repair, controlled release carrier of medicine, inorganic antibacterium materials, separation medium, water treatment, catalysis and so on. There are obviously limitations in controlling the morphology, dimension and compositon of apatite, which are basis of the micro-scale properties of apatite, so the application of apatite has been restricted to a certain extent. Therefore, the morphology control of apatite and its application has been one of the research topics. This study develops morphology control method via solution synthesis approach and prepares various kinds of apatite. Additionally, the sorption property of heavy metal ions and selective catalytic reduction of NOx by NH3 were also studied. The results are as follows: (1) Hydroxyapatite and Sr substitute hydroxyapatite microspheres with the diameter range 2~15 μm, which were composed of nanorods, have been successfully prepared by co-precipitation method. Sphere-like hydroxyapatite particles with diameter range 25~82 μm has been prepared by homogeneous co-precipitation process and the particles were built up of numerous hexagonal prism with diameter ranging from100 to 500 nm. When added certain amount of NaF in the homogeneous co-precipitation systerm, ellipsoidal fluorapatite with narrow size distribution can be obtained and the formation time of apatite phase greatly reduced. (2) It was in favor of the formation of larger hexagonal prism with the reaction conditions: pH value was 9.7, the mole ratio of EDTA/Ca was 1 and the hydrothermal reaction temperature was 200 oC. Hydroxyapatite hollow spheres with the diameter ranging from 0.43 to 0.72 mm, which is composed of nanorods, has been prepared by using ethanol and DMF as solvent with the assistant of of PEG 1000 under hydrothermal reaction condition. (3) The sorption amount of Cd2+ by hydroxyapatite spheres was larger than that of traditional bulk materials in certain sorption time. The sorption amount increased with the initial concentration of Cd2+ and the solution pH value. The Freundlich adsorption isotherms can be applied to our experimental results. Cd2+ desorption amount increased with the decreasing pH value of the extracting solution. When using HAc solution with the pH value of 2.88 as extracting solution, the desorption rate was 26.53%. The sorption ability for different heavy metal ions by hydroxyapatite follows the sequence: Pb2+> Cu2+> Cd2+> Zn2+ > Ni2+. When Cd2+ sorption amount was plotted against the samples specific surface area, linear dependence were observed for the samples prepared by precipitation method and hydrothermal method respectively. The samples prepared by hydrothermal method had higher sorption ability for Cd2+. (4) Cu loaded hydroxyapatite (HAP) catalyst for the selective catalytic reduction (SCR) of NOx by NH3 has been studied and shows good catalytic performance in the medium temperature range. When the Cu loading amount exceeded 2.24%, the catalytic performance shows little dependence on Cu loaded amount in the medium temperature range. Some reaction conditions, such as increasing O2 concentration or the total flow rate and the existence of water, would suppress the catalytic performance. DRIFTS results show the rate-determing step was the formation of NH2OH(a) from NO(g) and NH2(a). O2 can reacted with NOx on the surface of the catalyst and the formed stable nitrate species can block the activity center, resulting in the reduction of the catalytic activity. |
| 语种 | 中文 |
| 公开日期 | 2013-09-22 |
| 页码 | 141 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1626]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 朱荣海. 磷灰石的形貌控制及其在环境净化中的应用[D]. 中国科学院研究生院. 2010. |
入库方式： OAI收割
来源：过程工程研究所
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