Effects of high-efficiency depressant carboxymethyl chitosan on the flotation separation of fine-grained ilmenite and titanaugite: Experimental investigation and mechanism analysis

Abstract

This study employs carboxymethyl chitosan (CMCS) as a green depressant and systematically investigates its effect on the flotation separation of fine-grained ilmenite and titanaugite. Flotation tests demonstrated that in NaOL system, adding CMCS could achieve a concentrate with 33.09% TiO₂ grade and 61.41% recovery, successfully realizing efficient separation of fine-grained ilmenite and titanaugite. Through Zeta potential measurements, FTIR spectroscopy, XPS analysis, ToF-SIMS, turbidity tests, and optical microscopy observations, combined with DFT calculations, the selective depression mechanism of CMCS was elucidated. The findings suggested that the –NH₂ and –COO^- groups in CMCS were adsorbed onto Ca and Mg sites on the titanaugite surface through hydrogen bonding and chemical adsorption, forming a stable hydrophilic layer, while selectively inducing the flocculation of fine-particle titanaugite. In contrast, CMCS exhibited weaker interaction with ilmenite, allowing ilmenite to be effectively collected by NaOL. DFT calculations further confirmed that the N and O atoms in CMCS’s dual functional groups (–NH₂ and –COO^-) formed chemical bonds with Ca and Mg atoms on the titanaugite surface through electron transfer and orbital hybridization, significantly enhancing the stability of binding. Therefore, CMCS demonstrated remarkable depression performance in the flotation separation of fine-grained ilmenite and titanaugite through selective chemisorption and bridging flocculation.