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• Alkali pretreatment could improve the floatability difference between spodumene and feldspar. • The surface dissolution improved the flotation kinetic parameters of spodumene. • Alkali pretreatment changed the mineral surface ions distribution. The surface chemistry and morphology of minerals produced by alkali pretreatment affects their flotation behaviors. This study systematically investigated the impact on the mineral surface dissolution using NaOH as a modifier, which could modify the surface properties of minerals and improve the floatability difference between spodumene and feldspar. Various characterizations including flotation experiments, flotation kinetics analysis, SEM analysis, microcalorimetry analysis, zeta potential measurements, XPS analysis and ICP-MS analysis were conducted. Single minerals and actual ore flotation experiment results were in good agreement, and the flotation grade and recovery of Li 2 O in spodumene concentrates increased by 1.11 % and 6.99 %, respectively, after NaOH pretreatment. The flotation kinetics results demonstrated the cumulative recoveries of spodumene exhibited the best agreement with the first-order kinetic model and the flotation kinetic constant was improved after alkali pretreatment. Microcalorimetric results indicated the absolute values of the reaction heat for spodumene were higher than that of feldspar reacted with collectors after the alkali pretreatment. XPS and ICP results demonstrated the amounts of Al active sites on the spodumene surface was significantly increased after alkali pretreatment compared to that on the feldspar surface, improving the selective adsorption of NaOL. [ABSTRACT FROM AUTHOR]

• 1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP) was used as a calcite depressant in smithsonite flotation. • The selective adsorption of HEDP on calcite surface hindered the adsorption of NaOL. • HEDP adsorbed on calcite surface by forming HEDP-Ca six-membered ring chelates. Removing calcite is a tricky problem in smithsonite flotation because of its better floatability. 1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP), a scale inhibitor in water treatment industry, was chosen as a calcite depressant. This study validated the effectiveness of HEDP in separating smithsonite from calcite by flotation using sodium oleate (NaOL) as the collector, and obtained a 70% recovery difference in a single mineral flotation. Artificial mixed mineral flotation obtained a concentrate with a grade of 44% and a recovery of more than 80%. Zeta potential, Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) tests were conducted to obtained some crucial information on the adsorption of NaOL and HEDP, demonstrating that the adsorption of HEDP on calcite surfaces was stronger than smithsonite. The intense adsorption of HEDP on calcite surfaces was attributed to chelation with surface calcium sites. Quantum chemical calculations suggested that the selectivity of HEDP was closely related to the phosphate groups. HEDP was chemically adsorbed on calcite surface by complexing with calcium sites to form six-membered ring chelate. Partial oxygen atoms of phosphate groups dominated in the reaction with calcium sites, and the deprotonation of phosphate groups enhanced the reactivity. [ABSTRACT FROM AUTHOR]

• NaOL/ND13 first used to separate spodumene and feldspar and showed a better selectivity. • NaOL/ND13 co-absorbed much stronger on the spodumene surface than that of feldspar. • NaOL/ND13 had a stronger chemical reaction with Al sites on spodumene than on feldspar. The mixed anionic/cationic collector sodium oleate/ N-lauryl-1, 3-propylene diamine (NaOL/ND13) was firstly used to separate spodumene from feldspar and exhibited high selectivity. The flotation experiments of single and artificial-mixed mineral showed that the mixed NaOL/ND13 (NaOL: ND13 = 5:1) exhibited excellent flotation separation performance for spodumene from feldspar at pH 8.0. The zeta potential measurement results showed that NaOL and ND13 adsorbed on the mineral surface through chemical and electrostatic adsorption, respectively. The FTIR measurement results showed that the dominant species of NaOL/ND13 adsorbed strongly on mineral surface than each of its components and the interaction between collector and spodumene surface was stronger than that of feldspar surface. Contact angle measurements showed the mixed NaOL/ND13 amplified the difference in surface hydrophobicity between spodumene and feldspar. Ultra-microcalorimetric measurements showed the greater the absolute values of the net reaction heat for spodumene and feldspar reacted with collectors, the better their flotation separability. XPS further showed that NaOL/ND13 had strong chemical reaction with Al sites on mineral surface, but the interaction of NaOL/ND13 with spodumene was stronger than that with feldspar. Therefore, the results of this study are expected to provide more reference value and a meaningful guide for the development of selective flotation collectors for spodumene and feldspar. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesized ethane-1,2-dodecyldimethylammonium bromide (EDDA) for flotation process. • Reverse froth flotation of limonite. • Used cationic gemini surfactant EDDA as collector for flotation separation of quartz from limonite. • Obtained iron recovery of 86.14% and iron grade of 59.63% at natural pH (7–8) and EDDA 1 × 10-5mol/L. • Provided efficient flotation separation of limonite and quartz without depressant. In this paper, a cationic gemini surfactant ethane-1,2-dodecyldimethylammonium bromide (EDDA) was synthesized and used as a novel collector for the reverse froth flotation of limonite and quartz. According to the pure mineral flotation results, EDDA has good floatation ability and selectivity to quartz over the entire pH range of the slurry and is significantly more effective than dodecylamine (DDA). The experimental results of artificial mixed minerals show that EDDA can achieve high-efficiency separation of limonite and quartz without adding depressant. When the slurry is at natural pH (7–8) and EDDA is 1 × 10-5 mol/L, the concentrate with iron recovery of 86.14% and iron grade of 59.53% can be obtained. The zeta potential measurement shows that the EDDA has a significant effect on the potential of quartz. The results of FT-IR analysis confirmed the physical adsorption between EDDA and quartz. The agent preferentially modifies the quartz surface, improves the hydrophobicity of the quartz, and realizes the effective separation of limonite and quartz. [ABSTRACT FROM AUTHOR]