Near-neutral pH Solution Research Articles

Ethylene Glycol (EG)-Derived Chlorine-Resistant Cu0/TiO2-x for Efficient Photocatalytic Degradation of Nitrate to N2 without Sacrificial Agents at Near-Neutral pH Conditions: The Synergistic Effects of Cu0 and EG Radicals.

The selective photoreduction of nitrate to nontoxic nitrogen gas has emerged as an energy-efficient and environmentally friendly route for nitrate removal. However, the coexisting high-concentration chloride ions in wastewater can exert a significant influence on nitrate reduction due to the competitive adsorption and corrosion of Cl- on photocatalysts. Herein, we prepared ethylene glycol-Cu/TiO2-x (EG-Cu/TiO2-x) through a solvothermal reaction of Cu-doped TiO2 in an EG solution. The photodegradation of nitrate using EG-Cu/TiO2-x without adding sacrificial agents can efficiently occur in near-neutral pH solutions containing 50 mM Cl- with 95.26% of NO3- removal and 76.52% of N2 selectivity. Moreover, the photocatalyst performance remained at a high level after 8 cycles. In this work, NO3- was first converted to NH4+ by Cu0 and Ti3+, followed by the NH4+-to-N2 conversion by photogenerated chlorine free radicals. Compared to HO•, Cl•, and Cl2•-, ClO• is proved to play the predominant role in transforming NH4+ to N2. The EG radicals produced by UV light impede Cl- adsorption on Cu, protecting Cu0 from being corroded. What's more, photoelectrons can reduce Ti4+ to Ti3+ and protect Cu0 from being oxidized, enabling the stability of reactive sites. This work provides novel insights and understanding on designing photocatalysts for NO3- removal in solutions containing chloride ions, highlighting the significance of eliminating Cl- by EG radicals and adjusting the conversion process of NO3- for the efficient removal of NO3-.

Resistance of the welded joint of X70 steel for main gas pipelines against corrosion-mechanical cracking under cathodic polarization in near-neutral pH solutions

ABSTRACT Resistance of welded joint of X70 steel welded using Sv-08G1NMA and OK 10-74 flux wire against stress-corrosion cracking in near-neutral pH solution NS4 was investigated by slow-strain rate method, voltammetry, optical and scanning electron microscopy, electrolytic permeation of hydrogen. It was established that the stress-corrosion cracking of welded joint occurs through the base metal in the range of potentials more positive than −0.921 V by the anodic dissolution mechanism, more negative than −1.050 V is consistent with a hydrogen embrittlement mechanism, and in the potentials' range from −0.921 V to −1.050 V – both by the anodic dissolution and hydrogen embrittlement mechanism. The susceptibility to stress-corrosion cracking coefficient KS increases with the polarization potential shift −0.750 V → −0.950 V → −1.050 V as follows: for the welded joint – 1.1 → 1.16 → 1.35, for X70 steel as 1.0 → 1.12 → 1.0.

Simple incorporation and calcination of Zn-Al LDH during PEO processing in near-neutral pH solutions

Plasma electrolytic oxidation (PEO) process was employed for preparing oxide coatings on AA2024 aluminum alloy in solutions containing Zn-Al layered double hydroxide (LDH) particles. Sodium hexametaphosphate aqueous solution was selected as the standard solution, based on its almost neutral pH value considered as important for the LDH stability. Different additives to the standard solution were examined including 2-mecaptobenzothiazole (MBT) and different Zn-Al LDH compounds. The formed coatings underwent characterization regarding their morphology, chemical and phase composition, as well as assessment of their photocatalytic and corrosion protection efficiency. Coating thickening and compactness evolution were noted for all coatings with LDH additions to the standard solution. Obtained coatings are well-crystallized featuring γ-Al2O3 and two Zn-containing crystalline phases, namely ZnO and NaZnPO4, originating mainly from the LDH addition to the solution. PEO coatings obtained in this study demonstrated very reasonable photocatalytic activity for immobilized photocatalyst, reaching 51 % after 6 h under UV irradiation. The inclusion of Zn-Al LDH substantially boosted the impedance modules at low frequencies by two orders of magnitude compared to bare AA2024 alloy when exposed to a 3.5 % NaCl solution.

Organic Semiconductor-BiVO4 Tandem Devices for Solar-Driven H2O and CO2 Splitting.

Photoelectrochemical (PEC) devices offer a promising platform toward direct solar light harvesting and chemical storage through artificial photosynthesis. However, most prototypes employ wide bandgap semiconductors, moisture-sensitive inorganic light absorbers, or corrosive electrolytes. Here, the design and assembly of PEC devices based on an organic donor-acceptor bulk heterojunction (BHJ) using a carbon-based encapsulant are introduced, which demonstrate long-term H2 evolution and CO2 reduction in benign aqueous media. Accordingly, PCE10:EH-IDTBR photocathodes display long-term H2 production for 300 h in a near-neutral pH solution, whereas photocathodes with a molecular CO2 reduction catalyst attain a CO:H2 selectivity of 5.41±0.53 under 0.1 sun irradiation. Their early onset potential enables the construction of tandem PCE10:EH-IDTBR - BiVO4 artificial leaves, which couple unassisted syngas production with O2 evolution in a reactor completely powered by sunlight, sustaining a 1:1 ratio of CO to H2 over 96 h of operation.

Effects of cathodic protection potential on microbiologically induced corrosion behavior of X70 steel in a near-neutral pH solution

Sulfate reducing bacteria (SRB) are considered as one of the main causes for the failures of buried metal pipes. Although many researchers reported that more negative cathodic protection potential was required in environments containing SRB, SRB would increase the concentration of hydrogen adsorbed on steel surface and thus lead to hydrogen embrittlement. In the study, the optimum cathodic protection (CP) potentials of X70 steel in bacterial and sterile media were evaluated with electrochemical impedance spectroscopy. The morphology and composition of corrosion products were characterized by a scanning electron microscope (SEM), an energy dispersion x-ray spectrometer (EDS), and an x-ray photoelectron spectrometer (XPS). The corrosion morphology of X70 steel in NS4 medium was pits and the corrosion in the bacterial medium was more serious than that in the sterile medium. The corrosion products of X70 steel were FeOOH and Fe2O3 in the sterile medium, whereas its corrosion products in the bacterial medium were FeOOH and FeS. When CP potential was −775 mV, SRB growth was promoted and the optimal protection effect on X70 steel was achieved in the bacterial NS4 medium. Pits were still observed under the biofilm and the corresponding corrosion mechanism was extracellular electron transfer (EET). When CP potential was −875 mV, X70 steel realized the optimal protection in the sterile NS4 solution. However, CO2 hydrolysis and SRB metabolism in the bacterial medium resulted in hydrogen-induced pits. When CP potential was −1025 mV, the growth of SRB was inhibited and severe hydrogen evolution corrosion occurred on X70 steel in bacterial and sterile NS4 media. The optimal CP potential for pipeline steel in the sterile medium may lead to hydrogen corrosion in the bacterial medium when H+ concentration was high.

Stress corrosion cracking of X80 steel heat-affected zone in a near-neutral pH solution containing Bacillus cereus

Bacillus cereus (B. cereus) is observed to have varying effects on the stress corrosion cracking (SCC) sensitivity of different microstructures in the simulated heat-affected zone (HAZ) of X80 steel. At open circuit potential (OCP), the SCC sensitivity of different microstructures increased from 3.40–7.49% in an abiotic medium to 10.22–15.17% in a biotic medium. At −0.9 V (SCE), it increased from 22.81–26.51% to 35.76–39.60%. The increment in SCC sensitivity upon exposure to B. cereus was highest in the coarse-grained HAZ (7.68 and 16.79% at OCP and −0.9 V, respectively), followed by the intercritical and fine-grained HAZs. Owing to differences in the phase composition, grain boundary type, dislocation density, and surface volta potential, the initial adhesion number and position of B. cereus in the microstructure of the HAZ were differed, resulting in different sensitivities to SCC.

Highly Efficient Sensing of Hydrogen Peroxide Based on Atomically Dispersed Iron- and Nitrogen-Doped Carbon

Electrochemical hydrogen peroxide (H2O2) sensors are valuable tools in biological research and industrial applications for in situ monitoring H2O2 levels with the advantages of simplicity, portability, rapid response, and low cost. Herein, we demonstrate a novel electrochemical sensing platform based on Fe- and N-doped C composite (Fe–N–C) modified electrodes for sensitive detection of H2O2. This platform showed an excellent response to H2O2 reduction in near-neutral pH solutions with a low reduction potential and high sensitivities. The results of site-poisoning experiments suggest that the atomically dispersed Fe–Nx sites, which resemble the peroxidase-type enzymes, contribute to the high activity of the Fe-N-C catalyst for the H2O2 reduction reaction. Further, we developed a screen-printed electrode (SPE) modified with Fe–N–C with excellent electrocatalytic performances, including a favorable sensitivity (24.95 ± 0.77 μA μM−1 cm−2) and a low detection reagent (40 μl solution). Moreover, the as-prepared Fe–N–C/SPE was successfully applied to H2O2 sensing in an actual milk sample, with good recovery (between 98% and 102%). The as-prepared Fe–N–C/SPE sensor also exhibits superior selectivity, stability, and reproducibility, making it a promising candidate as a portable platform for H2O2 analytes, further improving its practical H2O2 sensing applications.

Efficient Retention and Alpha Spectroscopy of Actinides from Aqueous Solutions Using a Combination of Water-Soluble Star-like Polymers and Ultrafiltration Membranes.

We explored two approaches to recover uranium and plutonium from aqueous solutions at pH 4 and pH 7 using water-soluble star-like polyacrylamide polymers with a dextran core. In the first approach, a solution comprising a neutral or ionomer polymer was mixed with a radionuclide solution to form polymer–metal complexes that were then retained by ultrafiltration (UF) membranes under applied pressure. The same polymers were first deposited on the membrane in the second approach using pressure-driven flow. The applied polymers had an overall diameter of gyration of 120 nm, which exceeded the nominal diameter of the UF membrane pores. The polymers showed a high affinity to uranyl but could also be used to extract Pu from neutral or near-neutral pH solutions. Direct-flow single-step filtration and alpha spectrometry demonstrated that the UF membranes containing star-like copolymers could recover 99% of U and up to 60% of Pu from deionized water after filtering 15 mL solutions containing 25 ppm and 33 ppb of the actinides, correspondingly. The sorption capacity of the polymers for uranium could be measured as 1mg U per mg of the polymer after six subsequent filtration steps. Alpha spectroscopy of the deposited actinides revealed peculiarities of the structural organization of polymers and their complexes with U or Pu, depending on the approach. Though both approaches were efficient, the second approach (deposition of the polymer on the membrane followed by filtration) has an additional advantage of protecting the membrane pores from capillary collapse by filling them with the polymer chains. Therefore, these polymer-modified membranes could be used either in continuous or multi-step filtration process with drying after each step without deterioration of their sorption characteristics.

Nitrate-reducing-bacteria assisted hydrogen embrittlement of X80 steel in a near-neutral pH solution

The effect of nitrate-reducing bacteria (NRB) on the hydrogen embrittlement of X80 steel in a near-neutral pH solution was studied by various tests. NRB promote the formation of numerous pits under static load after 120 days and enlarge the polarization current at the same polarization potential. The increasing probability of hydrogen penetration into the biotic medium further leads to hydrogen embrittlement higher than 7–17% of the sterile medium. Under the same failure risk of 40%, NRB can cause hydrogen deterioration of steel, and the safe cathodic potential range will be narrowed from − 0.79–− 1.08 V to − 0.79–− 0.86 V (saturated calomel electrode).

Multiphysics modeling of environment assisted cracking of buried pipelines in contact with solutions of near-neutral pH

This paper presents a multiphysics model to predict environment assisted cracking in buried pipelines exposed to near-neutral pH solutions. In the calculation of crack growth rates, we involve two main cracking modes: hydrogen-facilitated fatigue and hydrogen-facilitated anodic dissolution. The former is fully coupled under the hydrogen-enhanced localized plasticity theory with a focus on hydrogen embrittlement produced by hydrogen diffusion and trapping. This provides formalism to account for contributions of electrochemical corrosion and variation of mechanically-diffusive hydrogen on the crack growth rates. The latter is explicitly quantified using the high-resolution crack tip fields. A competitive-based model is employed to evaluate crack growth rates. The model is verified by comparing experimentally measured and numerically simulated crack growth rates of a full-scale test reported in the literature. The results of this investigation show that the effect of hydrogen on the anodic-dissolution results in conservative predictions of the crack growth rates.

Effect of Nitrate-Reducing-Bacteria on Stress Corrosion Cracking Behavior of Simulated Heat-Affected Zone Microstructures of X80 Steel in a Near-Neutral Ph Solution

Effect of Nitrate-Reducing-Bacteria on Stress Corrosion Cracking Behavior of Simulated Heat-Affected Zone Microstructures of X80 Steel in a Near-Neutral Ph Solution

Corrosion mechanism of nitrate reducing bacteria on X80 steel correlated to its intermediate metabolite nitrite

The effect of nitrate reducing bacteria (NRB) on corrosion of X80 steel in near-neutral pH solution was studied using various electrochemical and surface techniques. NRB promoted the uniform and pitting corrosion of X80 steel, especially the depth and density of pits. The biofilm formed by NRB hinders the anodic reaction, but still accelerates the corrosion rate. The corrosion of NRB on X80 steel is not only related to the extracellular electron transfer, but also the concentration difference of the intermediate metabolite nitrite. When the nitrite concentration difference is lower than 6 mmol/L, the extracellular electron transfer of bacteria plays a dominant role in differential concentration corrosion, while when the nitrite concentration difference is higher than 6 mmol/L, it is the corrosion inhibition effect of γ-Fe2O3 oxidized by nitrite.

Fundamentally understanding the effect of Non-stable cathodic potential on stress corrosion cracking of pipeline steel in Near-neutral pH solution

In order to fundamentally understand the effect and mechanistic aspects of non-stable cathodic polarization (NSCP) on stress corrosion cracking (SCC) of pipeline steels, square wave polarization (SWP) was employed to investigate the interference of NSCP on SCC behavior of an X80 pipeline steel in a near-neutral pH environment. It was found that alterative stages of SWP, i.e., pulse current and stable current period, play different roles in SCC. The former mainly contributes to the local anodic dissolution (AD) process, while the latter strengthens the process of cathodic hydrogen evolution, thus resulting in increased susceptibility to SCC. Essential electrochemical processes involved above were analyzed in combination of physical and electrochemical models.

Galvanic Corrosion Behavior between Aluminum and Iron in Chloride Solutions at Near-Neutral pH and Corrosion Prevention By Anodizing

The joints between steels and aluminum alloys are expected to be used as multi-material structures due to their low cost, high stiffness, and high corrosion resistance. When aluminum alloys are connected to steels, galvanic corrosion is expected to occur because the corrosion potentials of aluminum alloys are lower than those of iron and steels. In the case of the galvanic corrosion in chloride solutions at near-neutral pH, the anodic reaction on aluminum alloys are oxide film formation and/or pitting. For pure Al and aluminum alloys, the generation of localized corrosion is evaluated by the critical potential for localized corrosion, such as pitting potential. In this study, the electrode potential under galvanic coupling and pitting potential were compared. Surface modification is effective methods for improvement on corrosion resistance of aluminum alloys. However, there is little research related to the galvanic corrosion between steels and aluminum alloys. In this research, the galvanic corrosion behavior of pure aluminum coupled to pure iron in chloride containing near-neutral pH solutions and the effect of anodizing on galvanic corrosion were investigated.Pure iron and pure aluminum were prepared as specimens in this research. The specimen surface of aluminum was polished down to 0.25 µm with a diamond paste. The iron surface was also polished down to 1 µm with a diamond paste. Diluted synthetic seawater (200 mg/L Cl-, pH 8.2) was used as the electrolyte for electrochemical measurements. The electrode area was ca. 10 mm2. Ag/AgCl (3.33 M KCl) was used as the reference electrode. Galvanic currents and electrode potentials were measured. The distance between iron and aluminum electrodes was kept at 10 mm. A zero resistance ammeter was used to measure the galvanic currents. The electrode potential of pure aluminum was also measured. Additionally, anodizing in sulfuric acid was conducted to pure aluminum in various voltages and times. Galvanic current measurements were carried out between these anodized specimens and pure iron to evaluate the effect of anodizing on galvanic corrosion prevention.The galvanic currents and electrode potentials of pure aluminum coupled to pure iron were measured. The galvanic currents were anodic currents. The oscillations of galvanic currents and electrode potentials were generated during the measurements. Filiform corrosion was observed on pure aluminum after the measurements. The generation of filiform corrosion was caused by higher electrode potentials of pure aluminum coupled to pure iron compared with the initiate potential for filiform corrosion.The time variation of galvanic currents and electrode potentials of anodized aluminum coupled to pure iron were also measured in the diluted synthetic seawater (pH 8.2). Pure aluminum specimens were anodized at 4, 8 and 16 V at 18 s. The oscillations were observed in the galvanic currents of anodized aluminum (4 and 8V); however, no oscillation was measured on the specimen anodized at 16 V. After the measurements, pitting was observed on anodized aluminum (4 and 8V). However, no pitting was observed on the specimen anodized at 16 V. The thickness of anodic oxide film was measured. It was confirmed that the thickness of the oxide film increased with anodizing voltage. Consequently, it was indicated that the galvanic corrosion resistance of pure aluminum for galvanic corrosion was enhanced by the increase of the thickness of the oxide film.

Influence of crystallographic texture on susceptibility to stress corrosion cracking mechanism of API 5L X52 steel for sour service

This work studies the relationship between the early stage of stress corrosion cracking (SCC) mechanism and the crystallographic texture of API 5L X52 steel for sour service in a near-neutral pH solution. Experimental evidence of the SCC initiation of X52 steel for sour service was obtained using SEM and EBSD techniques. The results show that the crack initiation mechanism behaves like a synergistic combination of chemical attack and stress concentration at pits, being the last one the driving force to crack transition. In addition, it was found from both X-ray macrotexture and EBSD microtexture measurements that the cracks initiation process depends strongly on the material’s texture characteristics and the presence of the texture fiber {0 0 1}//ND in X52 steel for sour service can increase its susceptibility to SCC. In a quantitative manner, the influence of the crystallographic texture in the SCC mechanism was explained through the relationship between the initiation of SCC cracks and the predictions of the anisotropy of Young’s modulus using EBSD measurements.

The AC corrosion and SCC mechanism of X80 pipeline steel in near-neutral pH solution

This paper studied the mechanism of alternating current (AC) promoting corrosion and improving SCC susceptibility in near-neutral pH solution. It was found that AC can result in local corrosion. X80 steel generated some pitting under the effect of full wave AC for the anodic dissolution. Some acuity pitting generated due that hydrogen induced anodic dissolution for negative half-wave AC. However, X80 steel generated some larger radius pitting for the positive half wave AC which was related to anodic dissolution. AC can facilitate ion migration from the result of crack propagation experiment. The SCC susceptibility of X80 steel in NS4 near neutral pH solution was negative half wave AC > full wave AC > positive half wave AC. The finite element results showed that AC can promote hydrogen precipitation. AC promoted X80 steel corrosion for facilitating ion migration and improved SCC susceptibility for assisting hydrogen precipitation.

Assessment by finite element modelling of the mechano-electrochemical interaction at double-ellipsoidal corrosion defect with varied inclinations on pipelines

In this work, a 3-dimensional finite element model was developed to assess the double-ellipsoidal corrosion defect on an X100 steel pipe exposed to a near-neutral pH solution, where the double-ellipsoidal defect is more representative than the usually used ellipsoid of the realistic defects generated on the pipelines. Results confirm that the axial lengths of the two ellipsoidal defects affect the local stress and anodic current density distributions, and the effect depends on the inclination of the defect on the pipeline. When the primary axis of the corrosion defect is perpendicular to the axial direction of the pipeline, the maximum stress and anodic current density happen at the defect’s deepest site, which is not necessarily the defect center. The reduced ratio of the axial lengths of the two ellipsoids, i.e., the increased difference of the axial lengths, remarkably increases the local stress concentration and anodic current density at the deepest site of the defect, making it the location of the fastest corrosion growth. When the corrosion defect is parallel to the axial direction of the pipeline, the maximum stress and anodic current density is always located at the center of the defect. The reduction in the axial length ratio does not obviously affect the stress and anodic current density.

Bifunctional nanozyme activities of layered double hydroxide derived Co-Al-Ce mixed metal oxides for antibacterial application

Marine biofouling is an expensive problem that needs evolved chemical or physical antifouling strategies. However, most of the current antifouling materials that would damage the environment through metal leaching and bacteria resistance are being halted. Nanozyme is one kind of environmental antifouling materials through generating reactive oxygen species (ROS). We prepared various contents of CeO2 that could uniform disperse compounding with Co3O4 and CoAl2O4 to form a stable Co-Al-Ce mixed metal oxide (MMO) by a layered double hydroxide derived method. We find that coupling with CeO2 can improve the peroxidase (POx) activity. When the molar ratio of Ce is 2.5% and the calcination temperature is 200°C, the POx activity of Co-Al-Ce MMO is the best caused by the good dispersion of catalytically active components and the high specific area (150.10±4.95 m2/g). This novel Co-Al-Ce MMO also exhibits an antibacterial mode of action Gram-negative bacteria in near-neutral pH solution through generating ROS (mainly ·O2−) in the presence of H2O2. Ce containing MMO can be utilized as potential green marine antifouling material.

Corrosion resistance and biocompatibility of calcium-containing coatings developed in near-neutral solutions containing phytic acid and phosphoric acid on AZ31B alloy

Calcium phosphate (Ca-P) coatings were fabricated by micro-arc oxidation (MAO) on AZ31B magnesium alloy in near-neutral pH solutions (pH 7.6–7.9) and the influences of EDTA-CaNa2, phytic acid (IP6), phosphoric acid (PA), and treatment time on coating properties were investigated by an orthogonal experiment. The results show that coating corrosion resistance is synergistically determined by coating characteristics with coating thickness playing a particularly important role. EDTA-CaNa2 acts as a corrosive agent of magnesium alloys and the increased concentration increases calcium content but decreases corrosion resistance of MAO coatings. As a strong chelating agent, IP6 can promote EDTA-CaNa2 solubility and therefore increases the calcium content more effectively than PA does. Compared with PA, IP6 more effectively improves corrosion resistance mainly by increasing coating thickness and bonding strength between coating and substrate, although the uniformity of anodic coatings becomes worse due to the greater interfacial tension of the IP6 solution than that of the PA solution. During MAO, P and F compete with each other to enter into anodic coatings. F amount in MAO coatings is closely related to the coating biocompatibility. MAO coatings developed in the solution composed of both IP6 and PA achieve low F content (3.49 at%) and good biocompatibility, while those fabricated in solutions containing only IP6 or PA achieve high F content (higher than 19.00 at%) and exhibit high toxicity.

Decoupling feldspar dissolution and precipitation rates at near-equilibrium with Si isotope tracers: Implications for modeling silicate weathering

Here we show that the isotope tracer experimental method for kinetic studies, aided by the recent advance and accessibility of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) analysis for non-traditional stable isotopes, can provide unidirectional dissolution rates at near-equilibrium conditions. For a long time, the only rates available at near-equilibrium were net reaction rates—dissolution rates minus precipitation rates. This is because the conventional experimental method of kinetic studies is based on element concentrations and can only provide net rates. The availability of unidirectional rates allows us to re-examine some fundamental concepts and practices of modeling weathering in geochemistry.In this study, we used the 29Si isotope tracer to conduct albite and K-feldspar dissolution experiments at near-equilibrium conditions in near-neutral pH solutions at 50 °C. Results show that the saturation indices (SI) of solutions approached zero with respect to albite and K-feldspar after ∼240–360 h (h), but 29Si/28Si ratios of the experimental solutions indicated continual dissolution for another 720–1440 h. The rates of total Si precipitation were much smaller than the rates of Si dissolution. The experimental solutions were supersaturated with respect to amorphous Al(OH)3, gibbsite, quartz, allophane, imogolite, and kaolinite. The SI of the solutions remained constant with respect to these phases while Al concentrations slightly decreased and Si concentrations slightly increased, indicating the coupled feldspar dissolution and precipitation of secondary phases, such as albite → amorphous Al(OH)3 + quartz or albite → solution + Al-Si phase(s), instead of significant albite and K-feldspar precipitation (the reverse reaction) at 50 °C. Reaction path modeling of the temporal evolution of Si, Al, Na, and pH revealed that albite dissolution (without significant backward reaction) coupled with the precipitation of a secondary phase with a Si:Al ratio of ∼2:1 can successfully match the experimental data.Given the negligible feldspar precipitation reactions in low-temperature systems (e.g., T < 100 °C), we recommend modeling feldspar weathering using unidirectional forward rates together with secondary phase precipitation rates in near-equilibrium, feldspar-undersaturated systems. This can be accomplished with minor modifications in geochemical modeling software or input files. The coupled feldspar dissolution with secondary phase precipitation arrests the system in a near-equilibrium steady state. Using affinity-based rate equations such the classical linear Transition State Theory rate law or the Burch empirical relation together with far-from-equilibrium rate data will predict significant feldspar precipitation in solutions undersaturated but close to equilibrium with respect to feldspars, which is unlikely at near ambient temperatures.