Dissolution Of Mg Research Articles

Electrochemical Aziridination of Tetrasubstituted Alkenes with Ammonia

Ammonia (NH3) is an ideal nitrogen source in terms of availability, reactivity, safety, atom economy, environmental compatibility, and ease of isolation. However, its utility for amine synthesis is...

Formation of amorphous precipitates in a corroded over-aged Al-Mg-Si alloy

Coarse intermetallics and fine precipitates play an important role in the corrosion of Al alloys. So far, there is no systematic experimental investigation about the corrosion of nano-precipitates. In the present work, the morphology and chemical composition of the corroded MgSi nano-precipitates in an Al-Mg-Si alloy with different aging times have been studied by transmission electron microscopy. Coarsened βʹ precipitates occurring in the over-aged state were found to be corroded through dissolution of Mg and oxidation of the remnant Si during twin-jet electropolishing. They finally transformed to amorphous SiO2 precipitates, showing an almost unetched interface with the Al matrix. The proportion of amorphous precipitates increased with prolonging aging time, as larger precipitates were preferentially corroded. This newly discovered crystalline-to-amorphous phase transformation depletes acid electrolyte but shows no damage. Such an intragranular corrosion behavior partly accounts for why over-aged Al-Mg-Si alloys are less susceptible to pitting and intergranular corrosion.

Changes in the interfacial charge-transfer resistance of Mg metal electrodes, measured by dynamic electrochemical impedance spectroscopy

The interfacial electrochemical characteristics of unpassivated Mg metal electrodes have been studied using Staircase Galvano Electrochemical Impedance Spectroscopy (SGEIS) in THF/C6H5MgCl/AlCl3 solutions over a wide range of applied dc currents. The results shed light on the mechanism of electrochemical deposition and dissolution of Mg. We found that at the stationary condition (at the OCV, when no current flows) there is a very high interfacial charge-transfer resistance of around 40,000 Ωcm2. The impedance decreases to several hundred Ωcm2 when dynamic, though steady, processes of Mg deposition or dissolution take place. The alternating process through which impedance spectroscopy is measured is superimposed on this system. We show that the high impedance measured at the OCV with a low direct current is due to interfacial adsorption phenomena. However, the adsorption phenomena affect the interfacial charge transfer in different ways depending on the direction of the reaction. During steady-state deposition, the adsorbed layer leads to a large distance for electron tunneling, which translates to a high charge-transfer impedance across the interface. Application of relatively large steady-state negative currents leads to changes in the composition of the adsorbed layer and a significant reduction in the charge-transfer resistance. During the opposite process, dissolution, the high interfacial impedance measured is probably predominantly due to migration of Mg ions away from the Mg metal surface, across the adsorbed layer, to the bulk solution. At relatively high direct currents (and overpotentials >100 mV) the interfacial resistivity obeys Butler–Volmer kinetics, which are not complicated by adsorption phenomena.

Rapid screening alloying elements for improved corrosion resistance on the Mg(0001) surface using first principles calculations.

The poor corrosion resistance of Mg alloys is a major challenge for their applications. The corrosion of Mg alloys is mainly controlled by the anodic dissolution of Mg and the cathodic hydrogen evolution reaction (HER), which is closely related to the stability and the hydrogen adsorption of the Mg surface. In this work, the effects of alloying elements (As, Ge, Cd, Zn, Ga, Al, and Y) on the stability and the hydrogen adsorption of a Mg(0001) surface have been studied based on first principles calculations. We have developed a horizontally integrated approach to evaluate their effects on corrosion resistance using parameters such as the surface energy, vacancy formation energy, Bader charge, electron density distribution, and the adsorption free energy of H atom at different adsorbed sites. We found that the doped atoms could significantly change the surface atomic structure and electron transfer on the Mg surface. These behaviors modified the energy required to detach the nearest neighbors of doped atoms from the Mg surface, the adsorption free energy of H atoms, and the stable adsorption sites of H atoms on the Mg surface, which regulate the corrosion resistance of Mg alloys. Interestingly, we found that Y doping on the Mg surface increased the corrosion resistance and our new method had tremendous potential in the rapid screening of alloying elements that could improve the stability of Mg alloys and inhibit the hydrogen evolution reaction.

The Zn2+ Destabilized Surface Film and Accelerated Corrosion of Magnesium

The effect of Zn2+ ions on the corrosion of pure magnesium (Mg) in NaCl solutions was systematically investigated by means of hydrogen evolution, weight loss, surface analysis, polarization curve and solution pH measurements. It was found that the presence of Zn2+ ions in the solution could significantly accelerate the dissolution of Mg. A new mechanism of surface film destabilization was proposed for the detrimental effect of Zn2+ on Mg corrosion, aiming to provide insight into the corrosion behavior of Zn-containing Mg alloys and the galvanic corrosion of Mg alloys coupled by Zn alloys.

(Invited) In Situ Observation of Anomalous Hydrogen Evolution on Mg Under Anodic Polarization

Mg alloys have long been considered a promising lightweight alloy system for various applications including consumer electronics, transportation, and medical equipment. However, owing to their high reactivity, Mg alloys cannot be used without proper coatings or surface treatments. Nevertheless, the chemical reactivity of Mg also opens up new ideas, such as the development of Mg-based biodegradable body implants and Mg metal battery systems. Unlike other metallic elements, Mg possesses a unique electrochemical response, especially under anodic polarization. To be specific, the rate of water reduction and hydrogen gas evolution, which is the dominant cathodic reaction on Mg in aqueous solutions, opposingly accelerates with the increase in anodic polarization. This phenomenon is the notorious negative difference effect (NDE) of Mg, or recently coined as the “anomalous hydrogen evolution”. Even after decades of research, the underlying mechanism of this peculiar electrochemical response of Mg is still under debate and yet to be elucidated.In order to have a clear picture of how the anomalous hydrogen evolution is related to the dissolution of Mg under anodic polarization, a customized cell was designed to enable high resolution in situ observation of the hydrogen evolution sites and surface morphology on Mg with an optical microscope. The compact cell is small enough to fit under the optical microscope with a short working distance at high magnification (50x-500x). The cell and the equipped reference and counter electrodes are connected to a potentiostat/galvanostat to control and monitor the polarization of the Mg working electrode. Additionally, a dynamic fluid control system is used to regulate the solution flow rate in the cell and constant circulation to avoid chemical or pH shifts. Additionally, the flowing solution also flushes away hydrogen bubbles attached to the electrode surface and ensure an unblocked view of the Mg surface. From this experimental setup, the anomalous hydrogen evolution under anodic polarization was found to be closely related to the actively propagating localized corrosion front of Mg. The relationship between hydrogen evolution response, applied anodic polarization, solution flow rate, as well as possible negative difference effect mechanisms, will be discussed. Figure 1

Biomineralization, dissolution and cellular studies of silicate bioceramics prepared from eggshell and rice husk.

The current investigation aims to replace the synthetic starting materials with biowaste to synthesize and explore three different silicate bioceramics. Pure silica from rice husk was extracted by decomposition of rice husk in muffle furnace followed by alkali treatment and acid precipitation. Raw eggshell and extracted silica were utilized for the preparation of wollastonite, diopside and forsterite by the solid-state method. The TG-DSC analysis shows that the crystallization temperature of wollastonite, diopside and forsterite was found to be 883°C, 870°C and 980°C, respectively. The phase purity of wollastonite was attained at 1100°C whereas diopside and forsterite were composed of secondary phases even after calcination at 1250°C and 1300°C respectively. All three materials behaved differently when exposed to the physiological environment, as wollastonite exhibited remarkable apatite deposition within 3days whereas a distinct apatite phase was noticed on the surface of diopside after 2weeks and forsterite shows the formation of apatite phase after five weeks of immersion. The rapid dissolution of Mg2+ ion from forsterite lowered the leaching of silicate ions into the simulated body fluid leading to poor apatite deposition over its surface. Chemical composition was found to plays a key role in the biomineralization ability of these bioceramics. Hemolysis and Lactate Dehydrogenase (LDH) release assays were performed to evaluate the hemocompatibility of silicate ceramics cultured at different concentrations (62.5, 125, and 250μg/mL) with red blood cells and mononuclear leucocytes (MLs) of mice. The hemolytic activity of all the tested bioceramics was insignificant (less than 1%). The interaction between diopside and mouse multipotent mesenchymal stromal cells (MMSCs) caused a negligible increase in the number of apoptosis-associated Annexin V-binding cells whereas forsterite and wollastonite induced an increase in the number of the apoptotic cells only at the concentration of 250μg/mL. The LDH assay did not show statistically significant changes in the proliferation of MMSCs after treatment with the bioceramics at the tested concentrations when compared to control (p>0.05). This finding showed that the death of a part of cells during the first 24h of incubation did not prevent the proliferation of MMSCs incubated with diopside, forsterite and wollastonite for 72h.

Influence of Ageing on the Intergranular Corrosion of an Al–Mg–Si Alloy

This report investigates the influence of ageing on the susceptibility to intergranular corrosion (IGC) of an Al–Mg–Si alloy. The selected AA6063 Al-alloy has been exposed to ageing treatments at a predetermine temperature of 423 K for durations of 1 to 168 h to achieve the wide range of ageing states covering under- to peak- to over-aged. The ageing behaviour of the selected alloy has been determined based on the results of hardness and tensile properties. The susceptibility to IGC has been evaluated following the British standard (BS ISO-11846) method B and assessed based on the average and maximum corrosion depths apart from in-depth surface and sub-surface characterizations of corroded specimens. It has been observed that the depths of corrosion increase monotonically with increase in ageing time. With progress of artificial ageing, the dominant mode of corrosion gradually changes in the order of minor pitting, moderate pitting, pitting plus localized IGC, localized IGC and uniform IGC. The phenomenon of preferential dissolution of Mg from the β″ (Mg5Si6) and β (Mg2Si) precipitates as well as the existence of Fe-rich intermetallic particles at the grain boundaries cause the pitting and intergranular corrosion because of the formation of local galvanic cells between the lower corrosion potential of Mg-depleted precipitates or precipitate free zones and to the adjacent anodic grain boundary precipitates.

Toward a Physical Description of the Role of Germanium in Moderating Cathodic Activation of Magnesium

The role played by surface film formation in moderating cathodic activation (i.e., H2 evolution associated with anodic dissolution in NaCl [aq]) was determined for an Mg-0.3Ge (wt%) alloy and contrasted with this process in pure Mg. Cathodic activation was not detected using the scanning vibrating electrode technique (SVET) during anodic dissolution of the Mg-0.3Ge alloy under either freely corroding or anodic polarization conditions. Filament tracks that initiated under the more aggressive testing condition remained electrochemically inert. However, volumetric H2 evolution measurements revealed that Ge alloying additions “switch off” the remote cathodes observed on previously corroded pure Mg surfaces, while Ge additions did not eliminate the “local” cathode at the principal sites of anodic activity (which cannot be detected by SVET). As such, the quantity of H2 measured on the corroding Mg-0.3Ge alloy arises exclusively from cathodic H2 evolution at the anodic sites. Moderation of sustained cathodic activation by alloying with Ge was associated with the incorporation of Ge into the inner MgO/Mg(OH)2 layer during anodic dissolution of Mg. It is possible that entrapped Ge particles or GeO2 serve as an effective poison for H recombination in the overall H2 evolution reaction that would otherwise readily occur on freshly formed Mg(OH)2 at anodic dissolution sites.

Effects of the Combined Addition of Zn and Mg on Corrosion Behaviors of Electropainted AlSi-Based Metallic Coatings Used for Hot-Stamping Steel Sheets.

The effects of the combined addition of Zn and Mg on the corrosion resistance of AlSi-based coating for automotive steel sheets were investigated using a variety of analytical and electrochemical techniques. The preferential dissolution of Mg and Zn from MgZn2/Mg2Si phases occurred on the AlSi-based coating that had been alloyed with a smaller portion of Zn and Mg, which contributed to the rapid surface coverage by corrosion products with a protective nature, reducing the corrosion current density. On the other hand, localized corrosion attacks caused by the selective dissolution of Mg were also observed in the AlSi-based coating with a smaller portion of Zn and Mg. Such alloying can also worsen its corrosion resistance when coated additionally with electrodeposited paint. The mechanistic reasons for these conflicting results are also discussed.

Effect of D-fructose on the in-vitro corrosion behavior of AZ31 magnesium alloy in simulated body fluid

The effect of adding d-fructose to simulated body fluid (SBF) on the corrosion behavior of AZ31 magnesium (Mg) alloy at 37 °C and at a pH of 7.4 was studied by potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), potentiostatic polarization and hydrogen (H2) collecting techniques, Raman spectroscopy technique, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy analysis (XPS) and Fourier transformed infrared (FTIR). The results demonstrated that the addition of fructose enhanced the deposition of phosphates forming thick and compact corrosion products, which inhibited the transmission of aggressive ions into the Mg substrate. As a result, both the anodic dissolution of Mg and negative difference effect (NDE) were suppressed. Thus, the corrosion resistance of AZ31 Mg alloy in SBF was significantly improved.

Effect of short T6 heat treatment on the microstructure and the mechanical properties of newly developed die-cast Al–Si–Mg–Mn alloys

A short T6 heat treatment for Al–Si–Mg–Mn die-cast alloys was developed with a solution treatment time of only 10 min at 540 °C. Excellent mechanical properties were achieved with a yield strength of 334–349 MPa and elongation of 2.6–4.6%, which is competitive with other die-cast alloys subjected to T6 heat treatment. The effects of solution time and temperature on the expansion of porosity were assessed. There is no apparent porosity expansion in T6 heat-treated alloys with short solution treatment or through prolonged solution time with lower temperatures. The short solution treatment enables the dissolution of Mg and spheroidizes eutectic Si and Mg2Si, associated with minimizing the growth of α-Al grains. The π-AlFeMnSiMg which forms during the final quaternary eutectic reaction transforms into nano-scale body-centred α-AlFeMnSi phase with dissolution of Si and Mg after the shot T6 heat treatment. The peak ageing hardness was determined by the solution temperature, and the highest peak aged hardness was obtained under a short T6 heat treatment. The coherent β’’ precipitate with needle-like morphology was found after this heat treatment.

Biodegradation behavior of micro-arc oxidation coating on magnesium alloy-from a protein perspective

Protein exerts a critical influence on the degradation behavior of absorbable magnesium (Mg)-based implants. However, the interaction mechanism between protein and a micro-arc oxidation (MAO) coating on Mg alloys remains unclear. Hereby, a MAO coating was fabricated on AZ31 Mg alloy. And its degradation behavior in phosphate buffer saline (PBS) containing bovine serum albumin (BSA) was investigated and compared with that of the uncoated alloy. Surface morphologies and chemical compositions were studied using Field-emission scanning electron microscope (FE-SEM), Fourier transform infrared spectrophotometer (FT-IR) and X-ray diffraction (XRD). The degradation behavior of the bare Mg alloy and its MAO coating was studied through electrochemical and hydrogen evolution tests. Cytotoxicity assay was applied to evaluate the biocompatibility of Mg alloy substrate and MAO coating. Results indicated that the presence of BSA decreased the degradation rate of Mg alloy substrate because BSA (RCH(NH2)COO‾) molecules combined with Mg2+ ions to form (RCH(NH2)COO)2Mg and thus inhibited the dissolution of Mg(OH)2 by impeding the attack of Cl‾ ions. In the case of MAO coated Mg alloy, the adsorption of BSA on MAO coating and the formation of (RCH(NH2)COO)2Mg exhibited a synergistic effect and enhanced the corrosion resistance of the coated alloy significantly. Furthermore, cell bioactive assay suggested that the MAO coating had good viability for MG63 cells due to its high surface area.

Clarifying the Role of Mg2Si and Si in Localized Corrosion of Aluminum Alloys by Quasi In Situ Transmission Electron Microscopy

The role of magnesium silicide (Mg2Si) and silicon (Si) particles in the localized corrosion of aluminum (Al) alloys was investigated herein. Sub-micrometer-sized Mg2Si and Si particles were grown in the Al matrix of Al-Mg-Si and Al-Si alloys, respectively, and characterized by transmission electron microscopy (TEM). A quasi in situ TEM technique was used to study an identical location containing Mg2Si or Si particle in the Al matrix, prior to and following a period of immersion in 0.1 M NaCl at pH 6, 2, and 12. At pH 6 and 2, Mg2Si was initially “anodic,” preferentially dealloying via selective dissolution of Mg, resulting in the development of SiO-rich remnants that are electrochemically inert. The SiO-rich remnants at pH 2 physically detached from the Al matrix. Silicon particles were electrochemically inert at pH 6, while “cathodic” at pH 2, dissolving the Al matrix at their periphery. It was observed that copper (Cu) was redeposited on Si particles at pH 2. At pH 12, Mg2Si and Si were “cathodic” to the Al matrix. This study clarifies, and provides new insights into, the characteristics of Al alloy physical manifestation of corrosion associated with Mg2Si and Si at the nanoscale.

SVET and ToF-SIMS Studies on the Galvanic Corrosion of β-phase/Aluminum Couple in Aqueous Solutions as a Function of pH

The galvanic corrosion of the β-phase (Al3Mg2)/Al couple has been studied using electrochemical methods, scanning vibrating electrode technique (SVET) and Time of flight-secondary ion spectroscopy (ToF-SIMS). Polarization tests reveal that Al3Mg2 is anodic relative to pure Al at pH ≤ 10. Visualization of the current density distribution over the Al3Mg2/Al galvanic couple by SVET reveals that at pH 2, an intense and stochastic anodic current density is evolved from Al3Mg2 while a heavy cathodic current flux is sustained on the surrounding Al matrix. At pH 6 and 10, localized both cathodic and anodic regions are seen on Al3Mg2 indicating its self-dissolution while the surrounding Al matrix remained relatively inert. However, at pH 13, a reversal of polarity occurs and Al3Mg2 becomes cathodic relative to Al. The severity of the galvanic coupling of Al3Mg2 to Al is in the order pH 13 > pH 2 > pH 6 > pH 10. ToF-SIMS analysis reveals that the dealloying of Al3Mg2 in the galvanic couple is by selective dissolution of Mg leading to the deposition of corrosion products dominated by Mg compounds in an acidic and neutral environment. In an alkaline environment, a relatively thin hydroxide rich film is formed.

Structure and in vitro dissolution of Mg and Sr containing borosilicate bioactive glasses for bone tissue engineering

Borosilicate bioactive glasses are promising for bone tissue engineering. The objective was to assess the impact of magnesium and/or strontium, when substituted for calcium on the glasses' thermal and dissolution properties. Both Mg and Sr substitution appeared to enhance the hot forming domain, i.e. the ability to hot process (sinter, draw fibres) without adverse crystallization. Structural analysis indicated that substitution of MgO and/or SrO for CaO results in changes in the BO3/BO4 ratio as well as in the ratio between bridging and non-bridging oxygen atoms in the silicate structure. Additionally, a de-shielding effect was noticed when Ca, Mg and Sr are present together in the glass network, possibly owing to PO43− charge-balanced preferentially by Na+. The Mg and/or Sr substitution resulted in a lower ion release in simulated body fluid and delayed formation of hydroxyapatite. However, once this layer formed it consisted of a Mg/Sr-substituted apatite. This work highlights the effect of combined ionic substitutions on bioactive glass structure and properties.

Corrosion of Commercial Mg–Al Alloys: AZ31B, AM60, and AZ91D

Aqueous corrosion, atmospheric corrosion, and ionic liquid dissolution studies were performed on commercial alloys AZ31B, AM60, and AZ91D and compared with previously reported results for single-phase binary Mg–Al alloys containing similar Al concentrations (αMg-2 at% Al, αMg-5 at% Al, and Mg-8 at% Al). Polarization studies in 0.6 M NaCl were used to characterize the aqueous free corrosion behavior during 20-h free immersion. Accelerated corrosion testing was performed using a rotating-disk electrode which revealed the evolution of an Al-rich mud-cracking and platelet morphology. Atmospheric droplet testing showed rapid pH increases that depended on the Al concentration in the alloy. Time-dependent contact angle measurements showed that the degree of droplet wetting increased during free corrosion by ∼50° over 20 h in 0.6 M NaCl. Ionic liquid dissolution studies in 1:2 M choline chloride:urea deep eutectic solvent were performed in order to examine the current-voltage behavior of these alloys in the absence of water and hydrogen reduction. The results of these studies revealed the formation of nanowire corrosion morphologies within a honeycomb lattice structure which we attribute to selective dissolution of Mg via a two-dimensional step-flow process.

Laboratory accelerated and field exposure testing of MgRP and MgORP on AA2024-T351: Chemical and electrochemical protection effects

Two Mg-based coatings consisting of Mg-rich primer (MgRP) and MgO-rich primer (MgORP) with and without topcoat were exposed to laboratory accelerated lifecycle testing (LALT) and outdoor field environments. The coatings were tested in parallel exposure studies utilizing ASTM B117, modified ASTM B117 (cyclic wet-dry, dark-UV exposure in ASTM synthetic ocean water), rural inland (Charlottesville, VA), and coastal marine (Kennedy Space Center) field exposure. Several characterization and electrochemical diagnostic techniques were used to continuously assess coating performance as a function of time in various exposures, enabling comparison of LALT to field exposures. The coating systems were evaluated with respect to the intact coating and to a machined scribe defect. The fate of Mg2+ upon dissolution of Mg and MgO with respect to pigment depletion, corrosion product formation, and repartitioning from the coating into the scribe was monitored with XRD and EDS. The capacity for MgRP and MgORP to provide barrier, cathodic, and chemical corrosion protection to AA2024-T351 substrate was evaluated. The ultimate ability of these coatings to protect the AA2024-T351 substrate both in the scribe and under the coating was gauged with optical profilometry assessment of corrosion damage. The Mg and MgO-based coating systems exhibited several desirable aspects of a corrosion preventative coating. The corrosion damage quantified both under the intact coating and within the scribe was much less than the corrosion damage measured on uncoated controls. Within a given exposure, the reduction of corrosion damage in the scribe correlated with the amount of Mg2+ which was released from the coating and repartitioned into the scribe. The open circuit potential of the coated substrate was depressed to more negative potentials than the bare substrate in 5 wt% NaCl, with non-topcoated samples establishing more negative potentials. The barrier properties remained high throughout the exposures for topcoated samples, which also better preserved the pigment from depletion. Comments are made regarding differences between the Mg and MgO-based coatings and the various laboratory and field exposures.

Improved longevity of nanoscale zero-valent iron with a magnesium hydroxide coating shell for the removal of Cr(VI) in sand columns

Nanoscale zero-valent iron (NZVI) has been engineered as an attractive tool for in-situ groundwater remediation. However, the poor mobility and aqueous corrosion of NZVI in the porous subsurface have hindered its practical applications. In this research, the NZVI surface was coated with a novel Mg(OH)2 shell (NZVI@Mg(OH)2) to improve the feasibility of NZVI for remediation. In the column tests for continuous removal of Cr(VI) from the flowing water, the Mg(OH)2 shell greatly improved the delivery of NZVI into the sand columns. Coating NZVI with Mg(OH)2 shell also showed considerably greater chemical stability than bare NZVI and thus greater resistance to aqueous corrosion. In addition, the dissolution of Mg(OH)2 allowed the reactivity to be gradually recovered along the sand column for Cr(VI) reduction. As a result, compared to bare NZVI in the columns, NZVI@Mg(OH)2 significantly prolonged the breakthrough period of Cr(VI) and hence increased the columns’ Cr(VI) removal capacity. Moreover, the Cr(III) produced was effectively immobilized by NZVI@Mg(OH)2, even under an acidic condition (pH 4.0). The results show that Mg(OH)2 coating is a promising technique to improve the longevity and capacity of NZVI for full-scale in-situ soil and groundwater remediation.

Influence of surface dissolution on sodium oleate adsorption on ilmenite and its gangue minerals by ultrasonic treatment

Selective separation of ilmenite from gangue minerals after ultrasonic preconditioning was studied in terms of surface dissolution. After preconditioning, ilmenite exhibited better single-mineral flotation capacity while titanaugite and olivine had lower recoveries. Significant separation could be obtained at pH 6.0 after ultrasonic treatment (500 W, 5 min). Zeta potentials of preconditioned titanaugite and olivine shifted positively compared to those of raw titanaugite and olivine treated with sodium oleate (NaOL), respectively. Meanwhile, the zeta potential of ilmenite was similar before and after NaOL adsorption. Mineral dissolution results indicate that ultrasonic preconditioning promotes the dissolution of Mg and Fe species but not the Ca species. The dissolution of Ca and Mg is much higher than that of Fe. According to solution chemistry calculation, Fe(OH)3 precipitate is dominant at pH greater than 2.5, and Ca2+, Mg2+, Fe2+, and Fe(OH)+ are dominant under acidic conditions. Microcalorimetric measurements demonstrate that the preconditioned ilmenite releases more heat during NaOL adsorption than titanaugite and olivine do. XPS results reveal that ultrasonic treatment facilitates the conversion of Fe2+ to Fe3+. After preconditioning, Fe species interacted with NaOL to promote the latter’s chemisorption on ilmenite and olivine, while Ca2+ was more likely to interact with NaOL on titanaugite.