Adsorption of Fe(III) on smithsonite surfaces and implications for flotation

Study on the Influence of Metal Ions on the Dispersion of Fine Calcium Gangue Minerals

In this study, the calcium gangue material calcite (−10 μm) was used to investigate the effects of different kinds of metal ions and dosages on the dispersion behavior of calcite. The test results showed that the dispersion behavior of calcite was poor under strongly alkaline conditions without the addition of metal ions, and the reason for that was calcite dissolved ions. The degree of influence of different metal ions on calcite dispersion behavior was Fe3+ > Mg2+ > Na+. The three metal ion dosage tests showed that the dispersion behavior of calcite became poorer with the increase of metal ion dosage. This mainly showed that with the increase of Na+ dosage, the trend of the dispersion behavior of calcite was not obvious, but with the increase of Fe3+ and Mg2+ dosage, the trend of calcite dispersion behavior changed more. The dispersion behavior of calcite was devastated by 5 × 10−4 mol/L Fe3+ at pH = 4−12. The different mechanisms of the three metal ions were identified by zeta potential, solution chemistry, and XPS analysis. Na+ only changed the zeta potential value of the calcite surface, which acted as a compressed electric double layer. However, the formation of metal hydroxide species or metal hydroxide surface precipitation due to the adsorption of Fe3+ and Mg2+ on the mineral surface resulted in the change of the dispersion behavior of calcite.

Effect of dextrin on flotation separation and surface properties of chalcopyrite and arsenopyrite

The flotation separation and mechanism of dextrin on chalcopyrite and arsenopyrite surface were investigated using micro-flotation tests, zeta potential measurements, infrared spectroscopy, contact angle measurement and surface adsorption experiments. The micro-flotation test showed that dextrin had obvious inhibitory effect on arsenopyrite flotation, but had no inhibitory effect on chalcopyrite flotation. After treating the surface of arsenopyrite with dextrin, the infrared spectra showed that new characteristic peaks, indicating that chemical adsorption and significant interaction between dextrin and arsenopyrite particles. Zeta potential measurements, contact angle measurement and surface adsorption experiments showed that the selective adsorption of dextrin added a large number of hydrophilic groups to the surface of arsenopyrite, but had little effect on chalcopyrite. In addition, the macromolecular chain structure of dextrin may hinder the attachment of collector molecules to arsenopyrite. The combined effect of these two aspects makes the arsenopyrite treated with dextrin lose its hydrophobicity and enables the separation of chalcopyrite and arsenopyrite.

Improved Understanding of the Sulfidization Mechanism in Amine Flotation of Smithsonite: An XPS, AFM and UV–Vis DRS Study

Sulfidization is required in the amine flotation of smithsonite; however, the sulfidization mechanism of smithsonite is still not fully understood. In this work, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS) were used to characterize sulfidized and unsulfidized smithsonite. The XPS and UV–vis DRS analyses showed that smithsonite sulfidization is a transformation of ZnCO3 to ZnS on the smithsonite surfaces. However, this transformation is localized, resulting in the coexistence of ZnCO3 and ZnS or in the formation of ZnS island structures on the sulfidized smithsonite surfaces. AFM height imaging showed that sulfidization can substantially change the surface morphology of smithsonite; in addition, AFM phase imaging demonstrated that sulfidization occurs locally on the smithsonite surfaces. Based on our findings, it can be concluded that smithsonite sulfidization is clearly a heterogeneous solid–liquid reaction in which the solid product attaches at the surfaces of unreacted smithsonite. Smithsonite sulfidization involves heterogeneous nucleation and growth of ZnS nuclei. Moreover, the ZnS might nucleate and grow preferentially in the regions with high reactivity, which might account for the formation of ZnS island structures. In addition, sphalerite-structured ZnS is more likely to be the sulfidization product of smithsonite under flotation-relevantconditions, as also demonstrated by the results of our UV–vis DRS analyses. The results of this study can provide deeper insights into the sulfidization mechanism of smithsonite.

Charcoal Prepared from Bougainvillea spectabilis Leaves as Low Cost Adsorbent: Kinetic and Equilibrium Studies for Removal of Iron from Aqueous Solution

Biosorption is one of the effective technique for removal of metals from aqueous solutions/industrial effluents. Present work is aimed to use low cost and ecofriendly material to remove the iron metal from aqueous solution which could possibly be used at industrial level. For this purpose, Bougainvillea spectabilis leaves were used for the production of charcoal. This charcoal was activated using HCl and HNO3. The AC shows promising efficiency for the adsorption of Fe II as a function of medium pH, contact time, adsorbent dose and temperature. Maximum adsorption was observed with 0.5–0.9 g adsorbent dose, 30 min contact time and at pH 3. Adsorption showed independence of temperature in the range of 30–70 °C. Among, Freundlich and Langmuir isotherms, the adsorbate followed Langmuir isothermal model. Among kinetics models, adsorbate followed pseudo second order kinetic model with R2 values of 0.9985 and 0.9996 for HCl treated and HNO3 treated AC, respectively. These data suggest that AC synthesized from Bougainvillea leaves proved to be an excellent adsorbent for the removal of iron metal from aqueous solution.

Study on the Interaction between Galena and Sphalerite During Grinding Based on the Migration of Surface Components

In Pb-Zn ore flotation, unintentional activation of sphalerite often leads to difficult separation of Pb and Zn minerals, during which grinding plays a key role in unintentional activation. Therefore, the aim of this study was to evaluate the surface component changes of two different mineral particles and to propose the interaction between galena and sphalerite during mixed grinding using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results show that after mixed grinding of the galena and sphalerite, the Pb content on the sphalerite surface increased with the decrease of Zn and Fe contents on the sphalerite surface. The lead ions from galena were obviously absorbed onto the sphalerite surface, while the zinc and iron ions from sphalerite were not obviously migrated to the galena surface. Principal component analysis (PCA) of a dataset composed of 206 positive ion peaks of galena and sphalerite indicates that the surface components of galena and sphalerite migrated from either side to different degrees. This study successfully identified an important factor for unintentional activation of lead and zinc minerals during flotation: homogenization of surface components of different minerals during grinding.

A Mechanism for the Adsorption of 2-(Hexadecanoylamino)Acetic Acid by Smithsonite: Surface Spectroscopy and Microflotation Experiments

Zinc is mostly extracted from oxidized zinc and zinc sulfide minerals, and this process involves flotation as a key step. While it is easier to float the sulfide mineral, its consumption and depletion has led to an increased reliance on oxidized zinc minerals, including smithsonite. Hence, the development of efficient ways of collecting smithsonite by flotation is an important objective. Herein, we describe the use of 2-(hexadecanoylamino)acetic acid (HAA), a novel surfactant, as a collector during smithsonite flotation. The mechanism and flotation performance of HAA during smithsonite flotation was investigated by total organic carbon (TOC) content studies, zeta potential measurements, Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses, combined with microflotation experiments. The flotation results revealed that HAA was an excellent collector in pulp over a wide pH range (9–12) and at a relatively low concentration (2 × 10−4 mol/L), at which a recovery of close to 90% of the smithsonite mineral was obtained. TOC content studies revealed that the good flotation recovery was ascribable to large amounts of collector molecule adsorbed on the smithsonite surface, while zeta potential measurements showed that the HAA was chemically adsorbed onto the smithsonite. FTIR and XPS analyses revealed that the HAA collector molecules adsorbed onto the smithsonite surface as zinc–HAA complexes involving carboxylate moieties and Zn sites on the smithsonite surface in alkaline solution.

Density Functional Theory Study on the Surface Properties and Floatability of Hemimorphite and Smithsonite

Hemimorphite and smithsonite are all-important zinc oxide minerals. The beneficiation and separation of them using flotation method is usually considered difficultly. Minerals surface wettability and its regulation are the core issues in the flotation process, which closely correlate with the surface properties of the minerals. Therefore, an in-depth understanding of the surface properties of the two minerals is of great significance for the study of the flotation technology of them. In this study, the surface properties of the hemimorphite (110) surface and the simthsointe (101) surface, and their relationships to the mineral floatability have been investigated by first-principle calculation method based on density functional theory. The calculation results demonstrated that the hemimorphite (110) surface exhibited more obviously surface reconstruction. For the orbital energy level of the surface atoms of two minerals, the O 2p orbital is closer to the Fermi level than the Zn 3d. Chemical bond Mulliken population value indicated that the ionicity of the unsaturated linkage on the smithsonite (101) surface was stronger than that on the hemimorphite (110) surface. The absolute values of the ratios of negative charges to positive charges on the surfaces of hemimorphite and smithsonite were 1.529 and 1.256 respectively. These results implied that the O atoms on hemimorphite (110) surface are more impede collector molecule, such as hydroximic acid, bond with Zn atom, hemimorphite (110) surface is more readily wetted by water. This study provides comprehension at an atomic level to the relationship between surface properties and the floatability of hemimorphite and smithsonite.