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.

Keywords

Al-starch / chelation / structure / characteristic / flotation

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