Investigation of Alkane-Assisted dodecylamine on flotation desilication of magnesite Tailings: Molecular dynamics simulations and model optimization

Abstract

Investigating the reverse flotation desilication process of magnesite tailings (MT) holds substantial merit in the context of magnesium metal recovery from solid waste. However, scant attention has been devoted to exploring the influence of the carbon chain length of diverse alkanes on the reverse flocfloatation desilication of MT. This research systematically delved into the selective adsorption behavior exhibited by dodecylamine (DDA) and its compound collectors on the surfaces of quartz and magnesite. As the carbon chain length of alkanes increases, the efficacy of reverse flotation desilication of MT diminishes. Under optimized conditions, the concentration of MgO in the concentrate registers a 0.93% increment, accompanied by a 2.05% reduction in SiO2 content. The optimal MgO grade attains 42.68%. The augmenting carbon chain length of alkanes leads to a decline in the dispersibility of the compound collector and a reduction in the diffusion coefficient of the monolayer film at the alkane/water interface. The compound collector, comprising n-heptane and DDA, manifests a noteworthy synergistic promotion effect on the flotation desilication of MT. This effect reduces the multilayer adsorption of DDA, promotes more hydrogen bonding formation, and favors DDA adsorption on the quartz surface over magnesite. Consequently, issues related to froth entrapment and poor selectivity are alleviated. Longer alkane chains in the compound collectors result in a stronger van der Waals force effect between the carbon chains. This effect causes DDDA to slide more easily on the quartz surface, which is not conducive to enhancing the hydrophobicity of the surface. Furthermore, alkane-induced hydrophobic flocculation increases the floccules size of quartz, enhancing the likelihood of bubble-particle adhesion. This investigation elucidates the molecular-level mechanism underlying alkane hydrophobic flocculation with varying chain lengths, contributing a theoretical foundation and technical support for the large-scale MT management and the sustainable production of magnesium metal.