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2 Physicochemical Problems of Mineral Processing

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Wettability of quartz particles at varying conditions on the basis of the measurement of relative wetting contact angles and their flotation behaviour

100%

Gao S. , Ma L. , Wei D. , Shen Y.

tom Vol. 55, iss. 1

278--289

In this paper, on the basis of a modified Washburn equation, the squared incremental pressure due to liquid rising vs. time were measured instead of wicking distances before reaching equilibrium, and the relative wetting contact angles (RWCA) were applied to characterize the surface wettability of quartz particles conditioned at different concentrations of flotation reagents. Combined with the flotation experiments on quartz particles at corresponding conditions, the relationship between flotation recoveries and RWCA was analysed, which proves that RWCA can characterize the surface wettability of quartz particles accurately. The results also showed that the best reagent conditions for floating quartz are pH 12.0, a Ca2+ concentration of 1×10-3 mol/dm3 and a sodium oleate concentration of 0.75×10-3 mol/dm3, where the recovery of quartz is 86%. The surface tension of the filtrate of the pulp was determined by a fully-automatic tensiometer as well. Based on the measured values of RWCA and surface tension, the free energy changes (ΔG) before and after the adhesion of bubbles and particles per unit area at corresponding situations were calculated, respectively. The trends of ΔG varying with the concentrations of reagents were in close accordance with those of RWCA and the flotation recoveries, proving that it is more likely for particles having bigger contact angles to adhere to bubbles, resulting in a higher flotation recovery. These results give a more feasible and accurate approach to analysing the surface wettability and floatability of fine particles.

A case study on the recovery of unevenly embedded particle size in high-carbon chalcopyrite using an alkyne-based thioester collector: Flotation processing and adsorption mechanism

75%

Qi Y. , Luo Y. , Qiu X. , Wei D. , Zhang F. , Wang C.

2024

tom Vol. 60, iss. 2

art. no. 188154

Abstract: The difference in chalcopyrite's primary ore-hosting rocks (dolomite and carbonaceous slate) in the Democratic Republic of the Congo results in an extremely uneven grain size distribution. Additionally, the presence of 2.21% organic carbon in the gangue impacts flotation efficiency. To address these challenges, ore properties were analyzed using the Mineral Liberation Analyzer (MLA), X-Ray Diffractometer (XRD), and microscopy. Flotation process was modified to incorporate a "middlings regrinding" processing, utilizing PDEC (an alkyne-based thioester collector, prop-2-yn-1-yl diethylcarbamodithioate) as the collector for experimental studies. Density Functional Theory (DFT) calculations elucidated the interaction mechanism of PDEC on chalcopyrite's surface. The MLA analysis indicates that chalcopyrite is mainly found in medium to fine grains, with the presence of fine-grained copper minerals smaller than 0.04mm accounting for 16.29% of the sample. This implies that these minerals require fine grinding for effective separation. Despite interference from organic carbon, PDEC demonstrates remarkable selectivity and efficiency in chalcopyrite flotation. By employing the "middlings regrinding" flotation method, a concentrate with a Cu content of 26.79% and a recovery of 87.88% was achieved, representing an increase of 0.17% in Cu grade and 4.09% in recovery rate compared to the conventional flotation process. DFT analysis demonstrates that the S 3p orbitals in carbon-sulfur double bond of PDEC and the C 2p orbitals in its acetylene group significantly affect its collection efficiency, engaging in hybridization with the Fe 3d orbitals on the surface of chalcopyrite, thereby facilitating a robust bonding interaction.