淀粉及其衍生物结构-吸附构象-抑制性能关系的Monte Carlo方法研究

项目名称： 淀粉及其衍生物结构-吸附构象-抑制性能关系的Monte Carlo方法研究

项目编号： No.50804055

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 电工技术

项目作者： 李海普

作者单位： 中南大学

项目金额： 20万元

中文摘要： 对于氧化矿反浮选富集，高效高选择性抑制剂的选用及开发十分重要。项目以典型的铝土矿反浮选脱硅为研究对象，从吸附构象的角度探讨了淀粉类大分子的结构与抑制性能的关系。通过小型浮选实验、动电位、吸附量、原子力显微镜、表面张力测定等手段考察了多种淀粉对一水硬铝石可浮性的影响及其吸附构象、抑制机理等，对吸附过程进行了热力学和动力学研究，并利用Monte Carlo模拟的方法研究了分子结构对其在均质表面吸附层厚度的影响。结果表明：各淀粉在矿物表面均具有较强的吸附，其中羧甲基淀粉随取代度的增加更趋于卧式吸附，阳离子淀粉呈环状吸附，两性淀粉介于二者之间，高度支链的蜡质玉米淀粉吸附层均匀平滑。吸附方式决定了淀粉对捕收剂十二胺的罩盖作用大小，再加上荷电高分子对阳离子捕收剂的静电作用，最终表现为蜡质玉米淀粉以及阳离子淀粉的优良抑制效果。淀粉在对十二胺小分子进行罩盖的同时，还会通过其疏水螺旋空腔与捕收剂的疏水碳链发生络合作用，每条支链淀粉两端各容纳一个十二胺碳链，使"淀粉-碘-DDA"体系对紫外光的最大吸收波长和吸收强度均有所下降。基于Monte Carlo的模拟计算为了解高分子在固体表面的吸附提供了丰富信息。

中文关键词： 淀粉衍生物；吸附构象；构效关系；作用机理；Monte Carlo模拟

英文摘要： In the process of reverse flotation of oxide ore, it is of importance to choose and develop the right depressants with high efficiency and high selectivity. The current project focused on the mechanism of the typical desilication of bauxite by examining the relationship between the structure of depressants (derivatives of starch) and their depressing performance in the aspect of adsorption conformation. The adsorption behavior of starches on diaspore was explored by investigating their floatability, adsorbed amount, adsorption conformation, and heat effect, as characterized by micro-flotation test, potential determination, AFM, and surface-tension measurement. In addition, a kinetic and thermodynamic study was performed to help understanding the adsorption process in view of the driving force. The Monte Carlo simulation was also used to provide the statistic information of the thickness of adsorption layer on the homogenous solid affected by the structural factors of macromolecules. The results showed that all kinds of starches concerned presented strong adsorption on mineral surfaces. It was found that the higher substitution of CMS corresponded to a higher propensity to adopt the laying-down mode in adsorption. In contrast, CAS was readily to give a loop conformation. As for AMS, the situation was mixed. The high-branched WMS showed good performance in depressing diaspore with smoother adsorption layer, mainly benefiting from the covering-effect by trapping the DDA molecules in their side-branch jungle. CAS, which carried positive charges, acted as good depressant due to the dispelling and covering action on DDA. A detailed investigation suggested that the inclusion complex could form between starch and DDA molecules. The color producing tests aided by iodine indicated that the hydrophobic chain of DDA had good chances to enter the hydrophobic helix of amylose and replace some seats pre-occupied by iodine. The resultant amylose-Iodine-DDA system featured the decreased λax and corresponding intensity. It can be roughly determined by calculation that each long branch of amylose can accommodate two DDA molecules using its two ends. The Monte Carlo simulation has provided useful information in probing the adsorption conformation of macromolecules on solid surface.

英文关键词： Derivatives of starch; Adsorption conformation; Relationship of structure and performance; Interaction mechasism; Monte Carlo simulation