Selective depression of calcite by a novel depressant thiodisuccinic acid and its application in flotation separation of cassiterite

Thiodisuccinic acid (TDA) can selectively inhibit calcite. • Cassiterite recovery exceeded 93 % while calcite recovery dropped to 24.04 %. • TDA only weakly adsorbs on cassiterite without affecting NaOL collection. • TDA forms stable chelates with calcite Ca atoms via carboxyl oxygen chemisorption. • TDA occupies calcite active sites to realize its selective flotation depression. Since cassiterite and calcite exhibit comparable inherent floatability, their high-efficiency flotation separation has long been a major technical challenge in the field of tin ore beneficiation. To address this challenge, thiodisuccinic acid (TDA), a novel depressant, was first deployed in the flotation system of cassiterite and calcite in this study. With sodium oleate (NaOL) adopted as the collector, selective depression of calcite and simultaneous efficient recovery of cassiterite were realized. Single mineral flotation results demonstrate that under the optimized conditions with pH 9, TDA dosage of 100 mg/L, and NaOL dosage of 40 mg/L, the recovery of cassiterite reaches 93.42 %, while the recovery of calcite merely reaches 24.04 %. Flotation tests on artificially mixed ores further verify that the addition of depressant TDA raises the tin grade of concentrate from 41.56 % to 53.18 %. Meanwhile, the tin recovery stays above 93 %, which realizes effective upgrading of tin concentrate. Analyses of contact angle, zeta potential, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) reveal that TDA undergoes chemical adsorption on the calcite surface and forms a dense adsorption layer, which significantly reduces its hydrophobicity. In contrast, only feeble physical adsorption takes place between TDA and cassiterite, which does not interfere with the normal collection of cassiterite by NaOL. Density functional theory (DFT) calculations further corroborate the chemical adsorption mechanism between TDA and calcite at the atomic scale. TDA interacts with Ca atoms on the calcite surface through oxygen atoms of carboxyl groups in its molecules and forms stable chelates. TDA occupies the adsorption sites on the calcite surface and hinders the adsorption of NaOL, thereby achieving selective depression of calcite. This study provides a green and efficient technical scheme for the high-efficiency flotation separation of cassiterite and calcite, and also offers a reference for the flotation separation of similar refractory oxide ores. Download: Download high-res image (188KB) Download: Download full-size image