Pengpeng Zhang,Guoqi Song,Chao Wang,Zhou Chen,Xiangpeng Gao,Mingyang Li
The conventional methods of separating closely related minerals like chlorite and specularite present challenges. This study delved into the pre-adsorption effect of 8-hydroxyquinoline (8-HQ) in a reverse flotation system using dextrin as a depressant and dodecylamine as a collector through single mineral flotation experiments, contact angle tests, Zeta potential determination, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The aim was to facilitate reverse flotation by pre-introducing 8-HQ to create specific adsorption with Al/Mg elements on the chlorite surface, thereby enhancing chlorite's flotation ability. Single mineral flotation experiments demonstrated that 8-HQ effectively heightened the disparity in floatability between the two minerals. When 15 mg/L of 8-HQ was added at a pH of 8, chlorite recovered 82.15 percent, while specularite only produced 19.2 percent. Results from artificial mixed minerals substantiated the feasibility of single mineral flotation. Further investigation into adsorption mechanisms revealed that 8-HQ forms steric hindrance via chelation and hydrogen bonding, preventing dextrin from adhering to the metal elements on the chlorite surface. The inherent hydrophobicity also promotes the formation of DDA hydrophobic flocs. Conversely, there was no notable adsorption between 8-HQ and specularite. Specularite could be specifically depressed by dextrin, enabling the selective separation of the two minerals. Finally, a model depicting the potential adsorption of 8-HQ on the mineral surface was proposed.
This study investigates the selective flocculation and high-gradient magnetic separation of fine-grained specularite (−12.5 μm) and quartz, utilizing two representative carboxymethyl starch (CMS) flocculants with distinct carbon chain length: short carbon chain carboxymethyl corn starch (CMCS) and long carbon chain carboxymethyl cassava starch (CMTS). The results demonstrate that CMS significantly enhances the magnetic separation recovery of specularite. Under optimal conditions, CMCS with a degree of substitution (DS) of 0.60 and CMTS with a DS of 0.25 increased the magnetic recovery of specularite from 72 % to 93 % and 92 %, respectively. Furthermore, the iron grade of the magnetic concentrate from the binary mixture (specularite and quartz) was elevated by 4 % and 6 %, while iron recovery rates improved by 17 % and 24 %, respectively. Zeta potential measurements indicate that CMS predominantly adsorbs onto the surface of specularite, with the short carbon chain CMCS-60 exhibiting stronger selectivity than the long carbon chain CMTS-25. Infrared spectroscopy (FTIR) further suggest that the carboxymethyl groups of CMS undergo strong chemical adsorption with the Fe sites on the specularite surface but hardly adsorbs on quartz. Polarized light microscopy and sedimentation tests reveal that CMS selectively adsorbs onto the specularite surface, facilitating aggregation into larger flocs, thereby improving the magnetic separation recovery of specularite. Notably, CMTS-25, the long carbon chain flocculant, promotes more efficient aggregation of specularite. However, neither CMS interacts with quartz, and the growth of specularite flocs in the binary system results in the entrapment of some quartz particles, thereby diminishing the separation efficiency. These findings provide new insights into the role of CMS in sustainable mineral processing, highlighting its potential for improving fine iron ore beneficiation while minimizing environmental impact.
Xi Zhang,Mingzhu Huangfu,Jiushuai Deng,Yu Wang,Bozeng Wu,Mingzhen Hu,Honghui Zhao,Suozhi Wu
Specularite is generally recovered by flotation, but its floatability is relatively weak. Activation is an effective method to improve the floatability of minerals. Therefore, finding an economic and effective activator to improve the recovery of specularite is an important research direction. In this study, lead nitrate as an activator was found and confirmed to improve the floatability of specularite. Its activation mechanism was further investigated by various analytical methods. The micro-flotation tests results showed that the recovery of specularite increased from 69.57% to 92.47% at a Pb 2+ concentration of 3 × 10 -5 mol/L, an approximately 23% increase, indicating that Pb 2+ could obviously activate specularite. The SEM-EDS results illustrated that the content of Pb on the specularite surface apparently increased after specularite treatment with lead nitrate, which confirmed the adsorption of Pb species on the surface of specularite. Zeta potential results showed that the zeta potential positively shifted within the pH range from 3 to 11, which was beneficial to the occurrence of electrostatic adsorption and chemisorption between negatively charged oleate species and specularite. XPS results revealed that lead species mainly adsorbed on the O atoms of Fe-O and Fe-OH at the specularite surface, and Pb atoms became new sites to interact with sodium oleate. In addition, Pb 2+ and Pb(OH) + were the predominant components that interacted with the specularite surface and formed -O-Pb and Fe-O-Pb complexes, which considerably increased the number of reactive sites on the specularite surface. After oleate components interacted with Pb-modified specularite, a denser hydrophobic layer was generated on the surface of specularite, which intensified the floatability of specularite.
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