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This study investigated the comprehensive utilization of spent magnesia-chrome refractories through gravity separation followed by flotation. The characteristics of refractories, the effects of various process parameters on the recovery of valuable metals and the adsorption mechanism of xanthate on silver were examined comprehensively. The results revealed that the metals penetrated into the refractories from cracks and holes. The penetrated metal particles were composed of different metal elements, several of which were dissolved in refractories. The optimum parameters were derived as follows: 60% particles passing a grinding fineness of 0.074 mm for gravity separation and regrinding tailing to 80% particles passing 0.074 mm for flotation, pH 8, 500 g/t of combined collector and 200 g/t of emulsified kerosene. Under these conditions, 99% Ag, 82% Pb and 81% Bi were recovered by a closed-circuit test. The obtained concentrates can be smelt as feeding, whereas the tailings with low impurities can be used as raw material for new refractories. The electrochemical and Fourier transform infrared measurements indicated that double xanthate and silver butyl xanthate were generated on the silver surface, which could improve the floatability of metals. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pectin can achieve selectively separation between apatite and dolomite. • Quantum chemistry was used to predict the reactive site of the polymer depressant molecule. • FTIR spectrum and Raman spectrum were used to analysis the selectively mechanism of pectin. • Pectin adsorbed on the dolomite surface by chelating with calcium and magnesium ions due to COO. The difficulty of apatite and dolomite to be efficiently separated by froth flotation due to similar physical and chemical properties of both minerals in using fatty acid collectors without any depressants. In this study, pectin was explored as an efficient and environment-friendly depressant in flotation to separate apatite and dolomite. In the micro-flotation experiments, pectin displayed an intense depressing effect in dolomite flotation and slightly affected apatite flotation. Quantum chemical calculation was used to predicated the reactive site of pectin, the results demonstrated that oxygen atoms of COO , OH and C O C in pectin display the most negative regions. The Zeta potential results indicated pectin was adsorbed on the dolomite surface selectively and depressed the adsorption of sodium oleate on the dolomite surface due to electrostatic repulsion effect. The Fourier transform infrared (FTIR) spectrum measurements uncovered that the selective separation of pectin was due to OH of pectin molecules. The Raman spectrum demonstrated that weak adsorption of pectin on the apatite surface was due to C O of pectin molecule, while the strong adsorption is regard as COO and C O C of pectin for dolomite. XPS results indicated that COO of pectin can chelate with Ca2+ and Mg2+ of dolomite surface and depress dolomite flotation. Hence, pectin was be utilised as an eco-friendly and highly selective depressant. [ABSTRACT FROM AUTHOR]

• 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]

In this paper, an investigation was conducted on the effects arising from albite, K-feldspar, quartz (three particle sizes) and muscovite (two particle sizes) of spodumene flotation tailings on ceramics, as well as the corresponding crystal changes. As indicated by the results, albite and K-feldspar positively impacted the strength of ceramic materials. The flexural strength of ceramics was increased with the decrease in the particle size of quartz. The flexural strength and linear shrinkage of ceramic materials was increased with decreased particle size of muscovite. The melting of albite and the formation of eutectic phase from albite and quart filled the pores between mineral particles, which were found as the major sintering mechanism of ceramics. Furthermore, during the sintering process, the crystal phase transformation of α-quartz to β-quartz and the de-hydroxylation of muscovite and kaolinite was occurred. Lastly, tailings have the potential to be used as raw materials for ceramic materials. Quartz could be used as ridge materials and green materials for permeable ceramics, albite could be used as flux for low temperature sintered ceramics, and muscovite could be used to prepare mullite refractories. [Display omitted] [ABSTRACT FROM AUTHOR]

This work explored the use of spodumene flotation tailings (SFT) as an aggregate used in cement mortar to mitigate their environmental impact. The principal phase compositions of SFT were quartz (Qtz), feldspar (Fsp) and muscovite (Ms). So, the effects of variations in the particle size of Qtz, and mineral additives, Ms and Fsp, on the compressive strength and hydration products were examined. Ms additives imparted the lowest compressive strength. Finer Qtz aggregates (4000–106 µm) reduced the nano-pore volume, and Ms increased the nano-pore width of cement mortar. In addition, fewer hydration products, and poor crystallinity of both ettringite (Aft) and portlandite resulted in a decrease in the compressive strength of the cement mortar, eventually. Therefore, increasing the particle size or optimisation of the mineral composition of SFT could provide a facile route to improving the mechanical properties of cement mortars. [Display omitted] • SFT results fewer hydration products, and poor crystallisation. • A reduction in the Qtz particle size (4000–106 µm) reduced the compressive strength. • Ms additives imparted the lowest compressive strength because of its properties. • Finer Qtz aggregates (4000–106 µm) resulted in a reduced pore volume. [ABSTRACT FROM AUTHOR]

• Oleate hydroxamic acid was synthesized and applied to bastnaesite flotation. • OLHA significantly increased the hydrophobicity of the bastnaesite surface. • OLHA and SHMP have competitive adsorption on the bastnaesite surface. • OLHA was interacted with bastnaesite by chemical absorption. Hydroxamic acid collectors display excellent selectivity but poor collecting ability in bastnaesite flotation. Improving the collecting capacity of hydroxamic acid collector appropriately become an effective method to enhance the performance of flotation reagents. A novel oleate hydroxamic acid (OLHA) as a collector was synthesized and applied to bastnaesite flotation in this work. The structure of OLHA was characterized by Fourier transform infrared spectrometry (FTIR) and nuclear magnetic resonance spectroscopy (NMR). The single mineral and artificial mixed minerals flotation experiments results show that OLHA achieved efficient flotation separation of bastnaesite and barite when odium hexametaphosphate (SHMP) was used as depressant. The contact angle, zeta potential, FTIR and X-ray Photoelectron Spectroscopy (XPS) measurements were performed to investigate the adsorption mechanism of OLHA. The contact angle results show that OLHA significantly improved the surface hydrophobicity of bastnaesite. Zeta potential and FTIR results show that in the presence of SHMP, OLHA selectively adsorbs to the surface of bastnaesite. Over all, OLHA adsorbs on the surface of bastnaesite through chemically adsorption, and strengthen the hydrophobicity of bastnaesite surface. Therefore, OLHA is a promising collector for bastnaesite flotation. [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]

The agglomeration of bastnaesite and fine fluorite severely reduces the recovery of bastnaesite, and a method to address this issue is urgently needed. Using measurement techniques such as micro-flotation, contact angle, zeta potential, in situ attenuated total reflectance-Fourier transform infrared (In situ ATR-FTIR) spectroscopy, and extended theory for calculating the stability of solution colloid (E-DLVO theory), this study investigated the selective adsorption mechanism of sodium hexametaphosphate (SHMP). The flotation results indicated that when sodium oleate (NaOL) was used as the collector, SHMP was 2.5 × 10−6 M, showing an outstanding flotation separation of bastnaesite from fine fluorite. The contact angle and zeta potential results showed that SHMP selectively increased the surface hydrophobicity and decreased the surface potential of fluorite. Additionally, in situ ATR-FTIR spectroscopy measurements revealed that HPO 4 2- and H 2 PO 4 - of SHMP chemically reacted with Ca2+ ions on the surface of fluorite and finally formed CaHPO 4 and Ca(H 2 PO 4) 2 stable complexes. However, SHMP was adsorbed by bastnaesite. Furthermore, EDLVO theoretical calculations confirmed that with the addition of SHMP, the electrostatic attraction of the double electric layer between the particles weakened 10 times, hydration repulsion was intense, and the total force between the particles changed from attractive to repulsive. The results also showed that fluorite and bastnaesite dispersed each other. Thus, SHMP can be used as a high-performance selective depressant for the fluorite flotation to realize bastnaesite flotation. [Display omitted] [ABSTRACT FROM AUTHOR]

The effects of sodium salts on the sulfidation behavior, phase transformation, ZnS particle growth, and zinc floatability of lead smelting slag (LSS) were investigated by roasting experiments and flotation tests. The roasting results indicated that sodium salt additives could enhance the reactivity of zinc sulfidation and the percentage of liquid phase and thus promoted the sulfidation of LSS and the growth of ZnS particles. However, with the increase in temperature, the positive effects were reduced because the reactivity of the sulfidation and the percentage of liquid phase were not the determining factors at high temperatures. The effect of Na 2 CO 3 was stronger than Na 2 SO 4 , while Na 2 SO 4 was stronger than NaCl on the sulfidation of zinc and the growth of ZnS particles. The addition of Na 2 CO 3 or Na 2 SO 4 favored the conversion of marmatite to wurtzite, which could be evaporated at temperatures above 1000 °C. Flotation test results revealed that sodium salt additives had different influences on the zinc grade and recovery at different temperatures. Na 2 CO 3 was the best additive in roasting for increase in zinc grade, due to the formation of metallic iron rather than iron sulfides. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Gemini surfactant EDDA was synthesized and innovatively used as a collector for bastnaesite flotation. • Compared with NaOL and DDA, EDDA exhibited a certain specificity for bastnaesite. • EDDA is physisorption on bastnaesite surface by static electricity and hydrogen bonds. • EDDA provides more coordination atoms to bastnaesite. The effective separation of bastnaesite from calcium-containing gangue minerals such as calcite is often difficult and the development of more environmentally-friendly and efficient collectors is imperative. A novel cationic Gemini surfactant ethane-1,2-dodecyldimethylammonium bromide (EDDA) was designed and synthesized in the laboratory, and the flotation performance of EDDA was investigated by micro-flotation and artificial mixed minerals experiments. When the EDDA concentration was 1.5 × 10−4 mol/L at pH 7, the grade of REO and the recovery with EDDA were 70.35 % and 88.45 %, respectively. While the grade of REO of NaOL and DDA were only 35.4 % and 44.15 %, indicating that EDDA has excellent selective collecting ability for bastnaesite. The contact angle test depicts that the hydrophobicity of bastnaesite surface enhances while the wettability of calcite surface almost unchanged. The adsorption mechanism was investigated by means of Fourier transform infrared spectroscopy (FTIR), zeta potential and X-ray photoelectron spectroscopy (XPS). The analysis results indicate that EDDA adsorbs on the surface of bastnaesite through electrostatic and hydrogen bonding, and strengthened the surface hydrophobicity of bastnaesite instead of calcite. The study reports the feasibility of applying EDDA for the separation of bastnaesite from calcite. [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]