The influence of metal cations on the behaviour of carboxymethyl celluloses as talc depressants

Investigation of Cellulose-Based Materials Applied in Life Sciences Using Laser Light Scattering Methods

This review emphasizes the practical importance of laser light scattering methods for characterizing cellulose and its derivatives. The physicochemical parameters like molecular weights, the radius of gyration, hydrodynamic radius, and conformation will be considered when the reproducibility of polymer behavior in solution is necessary for the subsequent optimization of the property profile of a designed product. Since there are various sources of cellulose, and the methods of cellulose extraction and chemical modification have variable yields, materials with variable molecular weights, and size polydispersity will often result. Later, the molecular masses will influence other physicochemical properties of cellulosic materials, both in solution and solid state. Consequently, the most rigorous determination of these quantities is imperative. In this regard, the following are presented and discussed in this review: the theoretical foundations of the light scattering phenomenon, the evolution of the specific instrumentation and detectors, the development of the detector-coupling techniques which include a light scattering detector, and finally, the importance of the specific parameters of polymers in solution, resulting from the data analysis of light scattering signals. All these aspects are summarized according to the chemical classification of the materials: celluloses, esters of cellulose, co-esters of cellulose, alkyl esters of cellulose, ethers of cellulose, and other heterogeneous cellulose derivatives with applications in life sciences.

Effect of the Molecular Weight of Carboxymethyl Cellulose on the Flotation of Chlorite

The present study aimed to investigate the influence mechanism of carboxymethyl cellulose (CMC) on the flotation of fine chlorite. To this end, a series of flotation tests, sedimentation tests, and microscope analyses were conducted. Flotation tests revealed an inverse relationship between particle size and the recovery of chlorite, indicating that finer particles exhibited higher recovery rates. Moreover, it was observed that the recovery of fine chlorite was significantly associated with the water recovery (proportion of water entering the floated product to the weight of water in the initial flotation suspension) and a variety of frother types. Based on these findings, it can be inferred that froth entrainment may constitute a crucial component of the recovery mechanism underlying fine chlorite. Thus, reducing froth entrainment (the phenomenon of hydrophilic minerals entering floated products through foam water) is the key to depress chlorite flotation. Flotation tests indicate that fine chlorite recovered into froth products can be depressed effectively by CMC with a high molecular weight. The results of sedimentation tests and microscope analyses in the presence of CMC prove that CMC with a high molecular weight generates flocculation on fine chlorite particles while that with a low molecular weight does not. It is suggested that the depression of chlorite flotation may be attributed to the reduction in the entrainment resulting from the flocculation induced by CMC.

New insights into the aggregation and disaggregation between serpentine and pyrite in the xanthate flotation system

HYPOTHESIS

In xanthate flotation system, the aggregation of serpentine on sulfide minerals significantly weakened their floatability. And it was generally assumed that the electrostatic attraction was of the dominant driver for coating of serpentine slimes. In this paper, the hydrophobic interaction between the "talc-like" cleavage plane of serpentine and the xanthate-hydrophobized surface of sulfide minerals was proposed as the dominated driver.

EXPERIMENTS

To evaluate the aggregation of serpentine on pyrite surface, a novel experimental protocol was designed, and the aggregation behavior and mechanism in the absence and presence of sodium isobutyl xanthate (SIBX) were explored through in situ optical microscope, micro-flotation, contact angle, zeta potential and FT-IR. Afterwards, the disaggregation mechanism of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) to the aggregates of serpentine on pyrite surface was revealed.

FINDINGS

The electrostatic attraction facilitated the slight aggregation of serpentine slimes on bare pyrite surface. The hydrophobic interaction between the "talc-like" plane of serpentine and SIBX-covered pyrite significantly promoted the aggregation between them, which remarkably weakened the floatability of pyrite. The attendance of HEDP anions reversed the surface potential of the octahedral Mg-O layers of serpentine from the positive into the negative, thus to prevent the aggregation of the HEDP-anchored serpentine with the SIBX-covered pyrite via the strong electrostatic repulsion between them. As a result, the disaggregation as well as SIBX flotation separation of pyrite from serpentine was realized. This investigation also provided new insights into the aggregation and disaggregation between serpentine and sulfide minerals during froth flotation.

Flotation Separation of Chalcopyrite and Talc Using Calcium Ions and Calcium Lignosulfonate as a Combined Depressant

As a major gangue mineral in sulfide ores, talc is difficult to separate from chalcopyrite in the flotation process due to its natural floatability, which affects the subsequent smelting process. In this study, the effects of calcium ions and calcium lignosulfonate (CLS) as a combination depressant for talc were systematically investigated along with the fundamental mechanisms. The results of our flotation tests showed the talc floating can be effectively depressed via the combination depressant effect of calcium ions and CLS over the pH range of 6–12. Measurements of the adsorption capacity, zeta potential, and Fourier transform infrared (FTIR) showed an enhancement of the adsorption capacity and adsorption strength of CLS on the talc surface after calcium ions were added. This result indicates that calcium ions adsorbed onto the talc, neutralized the negative charge on the surface of talc, generated the binding site with CLS, and formed the [talc-Ca2+/Ca(OH)+-CLS] system by strong adsorption. Further, the coverage rate of CLS on talc was significantly improved after the addition of calcium ions, as shown in the AFM imaging.

The Effect of the Ionic Strength of Process Water on the Interaction of Talc and CMC: Implications of Recirculated Water on Floatable Gangue Depression

Previous studies speculate that hydroxo species present in flotation pulps at pH > 9, particularly those of polyvalent cations, selectively adsorb onto gangue minerals. Such species supposedly enhance the depressive action of carboxymethyl cellulose (CMC) onto gangue via an acid-base interaction between the positively charged mineral surface and the negatively charged CMC molecule. Thus, the hydrophilicity of gangue minerals is enhanced, preventing the dilution of the concentrate. However, as there is little evidence to support these claims for complex process waters of increasing ionic strength, it is important to investigate. Adsorption data and mineral surface charge analyses provide a fundamental understanding of how electrolytes and their ionic strengths affect gangue mineral-depressant adsorption. It is strongly anticipated that decoupling these effects will allow process operators to tailor their process water quality needs towards best flotation operating regimes and, in the long run, effect closed water circuits. Thus, using talc as a proxy for naturally floatable gangue common in sulfidic Cu–Ni–PGM ores, this work investigates the influence of the ionic strength of process water on the adsorption of CMC onto talc for a perspective on how saline water in sulfidic ores would affect the behavior and therefore management of floatable gangue. In the presence of CMC, the microflotation results showed that the rate of talc recovery decreased with increasing ionic strength of process water. Increases in ionic strength resulted in an increase in the adsorption of CMC onto talc. Talc particles proved to have been more coagulated at higher ionic strength since the settling time decreased with increasing ionic strength. Furthermore, the zeta potential of talc particles became less negative at higher ionic strengths of process water. It is thus proposed that increases in the ionic strength of process water increased the zeta potential of talc particles, enhancing the adsorption of CMC onto talc. This in turn created a more coagulated nature on talc particles, increasing their hydrophilicity and thereby retarding floatability.

Selective Flotation of Cassiterite from Calcite with Salicylhydroxamic Acid Collector and Carboxymethyl Cellulose Depressant

Cassiterite is the most common and important tin-bearing mineral, and calcite, a primary gangue mineral is generally found in tin deposit. The flotation separation of cassiterite from calcite remains a challenge due to their similar response to traditional reagents. In cassiterite flotation, sodium oleate (NaOL) and sodium silicate (SS) have been widely used as a collector and a depressant, respectively. However, the low selectivity of NaOL and the large amount of SS required (which leads to serious problems in wastewater treatment) remain a difficult issue. In this study, a novel reagent scheme using lead nitrate as the activator, salicylhydroxamic acid (SHA) as the collector and carboxymethyl cellulose as the depressant was employed to improve the separation selectivity of cassiterite from calcite. Results of the flotation experiment using this new reagent scheme showed that compared with the previously reported scheme using benzohydroxamic acid (BHA) as the collector, the separation of cassiterite from calcite exhibited a higher selectivity and selectivity index (SI). The mechanism of the selective separation was investigated by zeta potential measurements, Fourier transform infrared and X-ray photoelectron spectroscopy analysis.

Carboxymethylcellulose adsorption on molybdenite: the effect of electrolyte composition on adsorption, bubble-surface collisions, and flotation

The adsorption of carboxymethylcellulose polymers on molybdenite was studied using spectroscopic ellipsometry and atomic force microscopy imaging with two polymers of differing degrees of carboxyl group substitution and at three different electrolyte conditions: 1 × 10(-2) M KCl, 2.76 × 10(-2) M KCl, and simulated flotation process water of multicomponent electrolyte content, with an ionic strength close to 2.76 × 10(-2) M. A higher degree of carboxyl substitution in the adsorbing polymer resulted in adsorbed layers that were thinner and with more patchy coverage; increasing the ionic strength of the electrolyte resulted in increased polymer layer thickness and coverage. The use of simulated process water resulted in the largest layer thickness and coverage for both polymers. The effect of the adsorbed polymer layer on bubble-particle attachment was studied with single bubble-surface collision experiments recorded with high-speed video capture and image processing and also with single mineral molybdenite flotation tests. The carboxymethylcellulose polymer with a lower degree of substitution resulted in almost complete prevention of wetting film rupture at the molybdenite surface under all electrolyte conditions. The polymer with a higher degree of substitution prevented rupture only when adsorbed from simulated process water. Molecular kinetic theory was used to quantify the effect of the polymer on the dewetting dynamics for collisions that resulted in wetting film rupture. Flotation experiments confirmed that adsorbed polymer layer properties, through their effect on the dynamics of bubble-particle attachment, are critical to predicting the effectiveness of polymers used to prevent mineral recovery in flotation.

The Adsorption Layer in the System: Carboxymethylcellulose/Surfactants/NaCl/MnO(2)

The influence of surfactants (anionic sodium dodecyl sulfate, and nonionic tert-octylphenol ethoxylate with 9.5EO) and their mixtures on the adsorption of carboxymethylcellulose (CMC) in the presence of 0.001 M NaCl on the manganese dioxide surface (MnO₂) was studied. The increase in CMC adsorption was observed in all measured systems in the presence of surfactants. The reason for this is the formation of complexes between polymer macromolecules and surfactants. Moreover, the dependence between the amount of surfactants adsorption and the CMC initial concentration was also studied. It proves that surfactant adsorption does not depend on the initial concentration of CMC. Another observation is that the increase in pH caused the decrease in CMC adsorption. The explanation of this phenomenon is connected with the influence of pH on the dissociation degree of the polyelectrolyte, kind and concentration of the surface active groups of the adsorbent. To characterize the compact and diffuse adsorption layer the surface charge density and the zeta potential of MnO₂ in the presence of CMC and surfactants were measured. The surface charge density of MnO₂ decreases in the presence of CMC or CMC/surfactant complexes. This is due to the presence of negatively charged groups in the compact part of the electric double layer. The zeta potential of MnO₂ is also lower in the presence of CMC and the CMC/surfactants complexes. The main reason for that is the shift of the slipping plane towards the bulk solution.

Quartz crystal microbalance with dissipation monitoring and surface plasmon resonance studies of carboxymethyl cellulose adsorption onto regenerated cellulose surfaces

Adsorption of anionic polyelectrolytes, sodium salts of carboxymethyl celluloses (CMCs) with different degrees of substitution (DS = 0.9 and 1.2), from aqueous electrolyte solutions onto regenerated cellulose surfaces was studied using quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR) experiments. The influence of both calcium chloride (CaCl(2)) and sodium chloride (NaCl) on CMC adsorption was examined. The QCM-D results demonstrated that CaCl(2) (divalent cation) caused significantly greater CMC adsorption onto regenerated cellulose surfaces than NaCl (monovalent cation) at the same ionic strength. The CMC layers adsorbed onto regenerated cellulose surfaces from CaCl(2) solutions exhibited greater stability upon exposure to flowing water than layers adsorbed from NaCl solutions. Both QCM-D and SPR results showed that CMC adsorption onto regenerated cellulose surfaces from CaCl(2) solutions increased with increasing CaCl(2) concentration up to the solubility limit (10 mM). Voigt-based viscoelastic modeling of the QCM-D data indicated that the CMC layers adsorbed onto regenerated cellulose surfaces had shear viscosities of η(f) ≈ 10(-3) N·s·m(-2) and elastic shear moduli of μ(f) ≈ 10(5) N·m(-2). Furthermore, the combination of SPR spectroscopy and QCM-D showed that the CMC layers contained 90-95% water. Adsorption isotherms for CMCs in CaCl(2) solutions were also obtained from QCM-D and were fit by Freundlich isotherms. This study demonstrated that CMC adsorption from CaCl(2) solutions is useful for the modification of cellulose surfaces.