通过测定铝盐高温水解过程固液平衡相图离析纯聚铝化合物并解析其晶体结构研究聚铝形态的演变机理

The hydrolyzation and polymerization species and their evolvement rules of Al salts is not only an important scientific problem for revealing the action mechanisms of Al-series flocculants and for synthesizing the highly efficient coagulants, but also a significant scientific problem for understanding the transport and transformation law of Al in the global environment and for preventing Al pollution, however, the problem has perplexed scientists for a century. Because various species coexist in a hydrolyzed Al solution at each temperature, the distribution of every species is going to change from monent to moment, it is difficult to isolate pure compounds from the solution and more difficult to grow a large enough single-crystal for structure solving. Also, because the structurally known Al species are very limited, how an Al monomer was developed into Al(OH)3 has still not been reached to a consensus. In our completed two NNSFC projects, 34 polyaluminum compounds were prepared under the direction of the phase diagrams determined at 25-100℃ and ordinary pressure;17 crystal structures were solved;2 evolution mechanisms were obtained, a SSSS polymerization mode and theory, and a local basification degree symmetrical equalization principle were summed up; and the flocculation performance of P-Al13 was proved to be more superior than K-Al13. Based on these achievements, this project will determine the phase diagrams during Al salts being hydrolyed at more than 100℃ and higher pressure, isolate more pure polyaluninum compounds, capture advanced species from NaOH hydrolyzed Al solution,grow single-crystals and solve their structures. For those species who are difficult to grow single-crystals, the structures will be solved from their powder XRD data by equipping powerful softwares and high speed computer. For those very small single-crystals,the structures will be solved by using the synchrotron radiation diffraction method. The final target is to do our best for obtaining a complete and unified evolution mechanism, polymerization model and theory of polyaluminum species.

铝盐的水解聚合形态及其演变规律既是探明铝系絮凝剂作用机理、合成高效混凝剂的重要科学问题，也是地球环境中铝迁移转化和铝污染防治的重大科学问题，但却困扰了科学家近百年。因每一温度下都是多种形态并存其分布时刻变化，因而从中离析纯聚铝化合物很难，得到适合解结构的单晶更难。由于结构已知的聚铝形态数量有限，所以单体铝究竟如何演变成氢氧化铝迄今尚无统一认识。本项目将在前两个项目所测100℃及以下常压相图指导下制备出34种聚铝化合物，解析出17种晶体结构，得出两条演变机理，总结出SSSS 聚合模式和局部碱化度对称均衡原理，证明P-Al13比K-Al13絮凝性能更佳的基础上，测定100℃以上中压相图，离析聚铝纯品，捕获强制水解高级形态，培养单晶解结构；对难培养单晶的拟配备强有力粉末解结构软件和快速计算机解结构；对微小单晶拟用同步辐射法解结构；从而为最终得出完整统一的聚铝形态形成演变机理和聚合模型理论做贡献。

测绘了125℃、150℃、175℃水热条件AlCl3-Al2O3-H2O体系和120℃常压条件AlCl3-Al(OH)3-H2O体系及75℃和100℃常压条件Al2(SO4)3-Al(OH)3-H2O体系6张固液平衡相图，为进一步研究AlCl3-Al2(SO4)3-Al(OH)3-H2O等四组分体系四面体相图奠定了厚实的基础。在相图指导下成功地从复杂的铝盐强制和自发水解溶液中离析出（或捕捉到）42种聚铝化合物，采用单晶X-射线结构分析与粉末X-射线衍射数据Rietveld全谱拟合结构解析相结合的手段解析了其中38种聚铝化合物的晶体结构，发现了其中23种聚合程度不同、连接方式各异的聚铝形态，大大丰富了聚铝形态的品种，为创建新的或优化已有的聚铝形态的形成和演变机理准备了丰硕的结构信息。在本课题组提出的局部碱化度对称均衡（LBDSE）原理（水解聚合反应总是在局部碱化度对称性上最不均衡的地方发生）引导下，纠正了历史文献中的4个错误结构，澄清了许多模糊认识。根据新获得的聚铝形态的结构信息，在本课题组提出的SSSS聚合模型和理论（聚铝形态的形成和演变经由“拼挂摆移”（Splicing, Suspending, Swinging, Slipping）聚合模式或其组合交替进行，各种形态按其有效内部碱化度由小到大的顺序在LBDSE原理引导下连续发展）指导下，总结出能够反映迄今为止所有聚铝形态形成演变过程的一条主要路径和四条分支路径。证明了氯化P─Al13的絮凝性能比K─Al13优越得多；发现溴化P─Al13、碘化P─Al13及碘化Al4 & Al1的絮凝性能可与氯化P─Al13媲美。围绕铝盐水解形态学和絮凝问题指导研究生开展各有侧重的研究完成了9篇硕士学位论文，获得了3项发明专利。研究成果在全国水处理化学大会和Separation and Purification Technology等国际知名期刊发表后被国内外同行广泛认同关注和引用，这些成果对加深铝盐水解过程及聚铝形态形成演变规律的认识具有重要作用，达到了预期的研究目标。