Insight of feature and structure for Al-starch colloidal depressant based on experiments and density function theory computation

Abstract

Al-starch has been successfully used in the inhibition for fine chlorite and calcite, while its fundamental feature and structure have not been explored. This study has found that the size and zeta potential of Al-starch are much larger than those of single starch. When starch chelates with aluminum ions, the initial characteristic peaks of Fourier transform infrared spectroscopy shift significantly, and new O—Al functional group appears. Meanwhile, the X-ray photoelectron spectroscopy detects the increase of O and Al atom concentration, and the O—Al peaks and metal group peaks are generated after the reaction of starch with Al ions. Moreover, the single molecule of starch is optimized through the cluster calculation, involving the trans-glucose and cis-glucose. The trans-glucose is easier chelated with aluminum ions to obtain optimal structure. Under this structure, the O₁ and O₆ of starch molecules covalently bind Al³⁺ to form the O₁—Al—O₆ chelation structure with shortest bond length and lowest interaction energy. Meanwhile, the frontier molecular orbital analysis confirms that the Al³⁺ provides empty orbitals to accept the electrons of glucose during the chelation. Furthermore, an efficient flotation separation of scheelite from ultrafine calcite and chlorite is achieved using Al-starch, which demonstrates the feasibility of this depressant.

摘要

Al-淀粉作为微细粒脉石矿物的抑制剂, 已成功用于细粒绿泥石和方解石的浮选抑制, 但其基本 特性和结构尚不明确。研究发现, Al-淀粉的粒径和Zeta 电位远大于单一淀粉的。当淀粉与铝离子螯合 时, 傅里叶变换红外光谱的初始特征峰明显移位, 出现新的O—Al 官能团。同时, X-射线光电子能谱 检测到随着O和Al 原子浓度的增加, 淀粉与Al 离子反应后产生O—Al 峰和金属基团峰。团簇模型计算 结果表明, 优化后的淀粉单分子包括反式葡萄糖和顺式葡萄糖两种, 反式葡萄糖更容易与铝离子螯合 形成最佳结构。在这种结构下, 淀粉分子中的O₁和O₆与Al³⁺通过化学键结合, 形成键长最短、作用能 最低的O₁—Al—O₆螯合结构。同时, 前线分子轨道分析证实了Al³⁺在螯合过程中提供了空轨道来接受 淀粉单分子提供的电子。混合矿试验进一步表明了Al-淀粉具有较好的选择性和应用前景, 可以实现 白钨矿与超细方解石和绿泥石的有效浮选分离。