Solution pH Research Articles

The corrosion behavior of borosilicate glass in the presence of cementitious waste forms.

Borosilicate glasses are widely used for radioactive waste disposal due to their ability to incorporate a variety of contaminants and radionuclides while exhibiting high durability in various disposal scenarios. This research evaluated the dissolution of borosilicate glass using both single-pass-flow-through (ASTM C1662-18) and product consistency test (ASTM C1285-21) methods with different solutions, including a cementitious-contacted water (called grout-contacted, GC, from this point) and solutions with varying levels of dissolved cementitious species such as Si, Ca, Al. The results indicated that the presence of Ca plays a crucial role in suppressing glass corrosion, as evidenced by the slower normalized dissolution rates, which were one order of magnitude lower for boron and two orders of magnitude lower for rhenium, observed in both Ca-amended and GC solutions compared to the pH 12 buffer solution. This effect is attributed to the formation of a dense, low-porosity, and strongly bonded calcium silicate hydrate (CSH) layer on the glass surface, which implies that a glass corrosion process is influenced by ion exchange involving alkali ions Na+, K+, Ca2+, and hydrogen-containing species. A small number of glass particles treated in the GC solution showed minor corrosion pits in the form of shallow craters with an average diameter of approximately 500 μm. This observation is correlated with a significant reduction, 2000 to 3000 times lower, in the cumulative volume of glass pores, indicating that smaller pore voids were "sealed" in the presence of Ca2+ ions, likely attributed to the formation of CSH precipitation or other corrosion products such as calcium carbonate saturated from the grout solution. These findings suggest that the presence of dissolved Ca in the GC solution can slow down the dissolution of borosilicate glass, contrary to the expected trend of higher dissolution rates resulting from exposure to high alkaline and thus higher pH solutions.

Ferrihydrite colloid-mediated transport of sulfamerazine in saturated porous media: Combined roles of rhamnolipid and solution pH

To date, there is still very little knowledge about the combined effects of typical biosurfactants and solution pH values on iron oxide colloid-mediated transport of sulfamerazine (SMZ, a typical sulfonamide antibiotic) in saturated porous media. Herein, the influences of rhamnolipid (a common biosurfactant in the environment) on SMZ mobility in the absence or presence of ferrihydrite (a model iron oxide) colloids in saturated quartz sand were explored. Generally, the rhamnolipid suppressed the transport of SMZ without ferrihydrite colloids owing to the bridging effect of this biosurfactant (i.e., rhamnolipid served as a bridging agent between SMZ and sand). Moreover, ferrihydrite colloids also inhibited SMZ mobility due to the deposition of colloid-associated SMZ. Surprisingly, the presence of rhamnolipid significantly influenced ferrihydrite colloid-mediated transport of SMZ, and this effect was highly dependent on the solution pH. Concretely, rhamnolipid enhanced the inhibitory effects of ferrihydrite colloids on SMZ transport at pH 5.0 because of the increased SMZ retention on the deposited colloids via the bridging effect of biosurfactant. At pH 7.0, the transport-inhibition effects of colloids were weakened by adding rhamnolipid, which was due to the colloid-associated SMZ transport and the promoting electrostatic repulsion between the free SMZ and sand/ the deposited colloids. Surprisingly, ferrihydrite colloids facilitated SMZ transport in the addition of rhamnolipid at pH 9.0. This phenomenon stemmed from the enhanced free SMZ mobility, the colloid-assisted mobility of SMZ, and the competitive deposition between SMZ– species and negatively charged colloids. Moreover, the two-site non-equilibrium model was performed to help interpret the controlling mechanisms for the synergistic effects of rhamnolipid and solution pH on colloid-mediated transport of SMZ. The outcomes of this study offer valuable knowledge about the functions of widespread biosurfactants in the environmental consequences of antibiotics in subsurface systems with iron oxide colloids.

Separation of nickel and iron from ferronickel via sulfuric acid leaching and hydrothermal precipitation

ABSTRACT Here, a hydrometallurgical process was proposed to separate nickel (Ni) and iron (Fe) from ferronickel. The effects of different factors, namely hydrothermal temperature, initial Fe2+ concentration, and Ni2+ concentration, on the hematite precipitation process, were detail investigated. Ferronickel powders were leached using a 120 g/L H2SO4 solution at 85 °C for 8 h. The final pH of the leaching solution was controlled at 3.0−4.5, and the Fe2+ concentration was maintained at 50−60 g/L. Copper from the ferronickel powder was first leached in the early stage of the leaching process, and then it was reduced by an excess of ferronickel powder, leading to its enrichment in the leaching residue. Approximately 50 g/L of Fe ions was successfully removed and precipitated as hematite containing 60% Fe, 0.3% Ni, and 1.5% S during hydrothermal precipitation at 200 °C for 3 h. Through evaporation crystallization at 90 °C for 8 h, large particles of nickel sulfate hexahydrate (NiSO4·6H2O) containing 19.4% Ni, 0.074% Fe, and 10.69% S were obtained. Moreover, through freezing crystallization at −8 °C for 1 h, smaller particles of NiSO4·6H2O product containing 20.3% Ni, 0.014% Fe, and 11.13% S were synthesised.

Ball milling boosted magnetic cotton husk-derived biochar adsorptive removal of oxytetracycline and ciprofloxacin from water

Oxytetracycline (OTC) and ciprofloxacin (CIP) contamination have caused serious risks to human health, and modified biochar is considered as a potential adsorbent for their removal. The typical agricultural waste of cotton husk was used as the feedstock, then was combined with γ-Fe2O3 and ball milling to innovatively synthesize nano zero-valent iron (nZVI) supporting magnetic cotton hush-derived biochar (Fe2O3@BMBC) by reductive calcination. Fe2O3@BMBC performed excellent adsorption performance with a maximum adsorption capacity for OTC (266.7 mg·g−1) and CIP (83.36 mg·g−1), and its adsorption capacity was 1.6 and 2.3 times that of cotton husk biochar (BC). Characterization analysis showed that Fe2O3@BMBC contained abundant oxygenated functional groups (e.g., -OH, C = O and Fe–O) and its surface was covered by diverse iron oxides. The high magnetization sensitivity of Fe2O3@BMBC guaranteed that it was easily to be separated by a magnet. Oxygenated functional groups (e.g., -OH, C = O and Fe–O) participated in the adsorption process, and solution pH significantly affected the adsorption behaviour, and pseudo-second-order model and Freundlich model better fitting the kinetics and isotherms data. These results confirmed that π-π conjugation, H-bonding, Fe–O complexation and electrostatic interactions contributed to the greater adsorption capacity of Fe2O3@BMBC. Ethanol + ultrasound could efficiently regenerate the used Fe2O3@BMBC and maintain its sustainable adsorption performance for OTC and CIP. Additionally, Fe2O3@BMBC performed a good environmental security in a wide pH range (from 3 to 11) in view of the low leaching risk of Fe.Graphical

Optimization of Microbial Fuel Cell Operational Parameters for the Treatment of Brewery Sludge

AbstractThis study investigates the potential of a salt bridge‐mediated microbial fuel cell (MFC) for power generation and wastewater sludge treatment in breweries. Unlike traditional “one‐parameter‐at‐a‐time” methodologies, this study uses a three‐variable Box–Behnken design response surface methodology to optimize critical MFC operational parameters. The effects of parameters such as solution pH, salt bridge molarity, and temperature were studied in the range of 4 to 10, 1 to 5 M, and 20 to 45 g L−1. The optimum operating parameters were found to be solution pH of 5.853, salt bridge molarity of 3.343 M, and temperature of 32.5 °C for chemical oxygen demand and biological oxygen demand removal efficiencies of 92.485 % and 88.51 %, respectively. Temperature was found to be the most significant factor affecting the reactor's performance.

Development of δ-Bi2O3/Bi2SiO5 heterostructures based on biogenic silica for photocatalytic treatment from organic pollutants

ABSTRACT δ-Bi2O3/Bi2SiO5 heterostructural photocatalysts with different contents of bismuth in samples (X-Bi-Si, where X = 10–60% Bi2O3) were prepared by the facile sol–gel method using bismuth nitrate and biogenic silica from rice husk biomass as precursors. FT-IR, scanning electron microscope, XRD, energy-dispersive X-ray fluorescence, and UV–Vis methods were systematically used to characterize the as-obtained materials. The photodegradation of methyl orange (MO) in neutral aqueous solutions (pH (6.8)) under UV irradiation was studied to evaluate their photocatalytic activities. The phase composition, morphology, and photocatalytic activity of the samples depended on the content of bismuth oxide in the samples. The maximum degree of MO degradation was 45% for 50-Bi-Si samples containing photoactive δ-Bi2O3 and Bi2SiO5 phases.

PH Measurement and Modelling as a Link between High School Chemistry and Mathematics

Investigating the acidity and alkalinity of solutions is linked to understanding the pH of solutions. At the secondary school level, this also means understanding the concept of the logarithmic function, which is a suitable topic for developing mathematical literacy. The objective was to design a laboratory activity in which students would not only measure solutions with the expected pH, but also construct a graph from the measured values without being aware of the dependence of pH on H3O+ concentration. This would enable them to identify the function that best fits the obtained curve. The problem presented discusses the limitations of the design and provides teachers with a basis for preparing the laboratory exercise, including a worksheet for students. The validation of the laboratory activity demonstrates that during the implementation of the exercise, students are able to construct a graph from the measured values and solve application problems related to understanding the concept of a logarithmic function.

Direct potentiometric bicarbonate/carbon dioxide sensing based on polymeric membranes doped with selective meso-bisubstituted calix[4]pyrrole ionophores.

We evaluated in this work the properties of a promising class of HCO3- ionophores, which have not been recognized previously. Three types of neutral or charged calix[4]pyrroles with meso-bisubstituted groups were evaluated as ionophores for polymeric membrane HCO3- selective electrodes. Optimizing membrane components, such as ionophores, lipophilic additives and plasticizers, yielded ISEs exhibiting Nernstian response to HCO3- with improved linear range and detection limits, while the selectivity sequence differs significantly from the Hofmeister series. Interference from important biological and environmental species was reduced significantly, especially that from SCN-, NO3-, Br- and Cl-, which are always at high concentrations in related samples. In order to provide more insights into the properties of the ionophores and performance of the proposed ISEs, the stability constants of anion-ionophore complexes in the membrane phase were determined. Studies on the influence of the sample solution pH demonstrated that the proposed ISEs can be employed in a wide pH range of 3.0-9.0 with fast response (<30 s), good reversibility and long shelf life. Moreover, the proposed ISEs were used to quantify the concentration of HCO3- and dissolved CO2 in mineral and beverage samples with good recoveries.

Adsorption–desorption and leaching behavior of benzovindiflupyr in different soil types

Benzovindiflupyr is a succinate dehydrogenase inhibitor fungicide that targets mitochondrial function for disease control. In this study, we investigated the adsorption–desorption and leaching behavior of benzovindiflupyr in eight soil types using the batch equilibrium method and the soil column leaching method. A Freundlich model (r2 > 0.9959) was used to better characterize the adsorption-desorption process in eight soil types, with adsorption coefficients (KF-ads) ranging from 2.303 to 17.886. KF-ads was significantly and positively correlated (p < 0.05) with the organic carbon content. High temperatures and increased initial pH of aqueous solutions led to a decrease in benzovindiflupyr adsorption in the soil. The adsorption was also influenced by factors such as ionic strength, humic acid, surfactant type, microplastic type, and particle size and concentration. Moreover, benzovindiflupyr exhibited low leachability in all four soils selected, but different leaching solutions affected the risk of benzovindiflupyr migration to groundwater. Overall, this study provides insights into the adsorption characteristics of benzovindiflupyr in different soils and provides key information for environmental risk assessment.

Strong Magnetic p-n Heterojunction Fe3O4-FeWO4 for Photo-Fenton Degradation of Tetracycline Hydrochloride

With the abuse of antibiotics, its pollution poses an increasing threat to the environment and human health. Effective degradation of organic pollutants in water bodies is urgent. Compared to traditional treatment methods, advanced oxidation processes that have developed rapidly in recent years are more environmentally friendly, efficient and applicable to a wider range of organic compounds. FeWO4 was used in this study as the iron-based semiconductor material to modify and optimize the material design. Fe3O4/FeWO4 composites were prepared by a two-step hydrothermal method. The crystal structure, surface morphology, electrochemical properties and separability of the composite semiconductor were analyzed by XRD, XPS, UV-vis, SEM, EDS and Mott-Schottky. The results showed that, when the initial contaminant concentration was 30 mg/L, the initial solution pH was 4, the dosage of the catalyst was 25 mg and the dosage of hydrogen peroxide was 30 μL, the degradation efficiency of tetracycline hydrochloride (TCH) could reach 91% within 60 min, which was significantly improved compared to the performance of the single semiconductors Fe3O4 and FeWO4. In addition, the catalyst prepared in this experiment can be easily recovered by magnetic separation technology in practical application, which will not affect the turbidity of water while reducing the cost of catalyst separation and recovery.

Enhancing environmental sustainability: Butea monosperma leaves as a key component in WO3-based composites for water purification and therapeutic applications.

In this research, a novel nano-biocomposite material, namely, tungsten trioxide-Butea monosperma leaf powder (WO3@BLP), is an effective and eco-friendly adsorbent used for the mitigation of congo red (CR) and crystal violet (CV) dyes from its aqueous phase. The as-prepared WO3@BLP was characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), DLS analysis, and TGA. Many factors such as solution pH, WO3@BLP dose, temperature, contact time, and initial CR/CV dye concentrations were exploited to monitor the adsorption efficiency of WO3@BLP composites. The biosorption of both CR and CV dyes followed the Langmuir isotherm, with maximum adsorption capacities (qmax) reaching 84.91 mg g-1 for CR at pH 2.3 and 162.75 mg g-1 for CV at pH 8, fitting of kinetics data to the PSO model with closed values of qeexp (mg g-1) and qecal (mg g-1), i.e., 25.69 to 25.38 mg g-1 for CR dye and 29.06 to 29.08 mg g-1 for CV dye. The interaction mechanism behind the adsorption of CR and CV dyes onto the WO3@BLP bionanocomposite includes electrostatic interaction and surface complexation. The synthesized materials were tested for antifungal activity against three different Candida cells, i.e., C. albicans ATCC 90028, C. glabrata ATCC 90030, and C. tropicalis ATCC 750, by using broth dilution method on the minimum inhibiting concentration (MIC). Furthermore, the cytotoxicity of nano-formulated WO3@BLP was studied by in vitro hemolytic assay on a human host. Overall, this research presents a pioneering nano-biocomposite, WO3@BLP, as a sustainable adsorbent for CR and CV dye removal, adhering to Langmuir isotherm and pseudo-second-order kinetics. Its multifaceted approach includes elucidating interaction mechanisms, demonstrating antifungal activity, and assessing cytotoxicity, marking a significant advancement in environmental remediation.

Sustainable Processes of Biosorption of Pb(II) Ions from Synthetic Wastewater Using Waste Biomass from Mullein Leaves

The aim of this study is to evaluate mullein (Verbascum thapsus) as a cost-effective and sustainable adsorbent for the biosorption of Pb(II) ions from synthetic wastewater samples. Biosorption of mullein was investigated as a function of initial Pb(II) concentration (25–400 mg L−1), biosorbent dosage (2–20 g L−1), solution pH (3–7), and contact time (10–120 min). Mullein as a material with a high affinity for Pb(II) ions had a biosorption efficiency of 98.56% under the optimal conditions: pH 6, initial concentration of Pb(II) at 100 mg L−1, contact time of 90 min, and biosorbent dosage of 20 g L−1. The FTIR spectra of mullein leaves showed that oxygen-containing functional groups on the surface are potentially active sites for the biosorption of Pb(II) ions. EDS analysis and the pHPZC value confirmed the adsorption of Pb(II) ions at the active sites of the mullein. Kinetic and isotherm data enabled insights into the modes of Pb(II) biosorption on the mullein surface which were best explained with the pseudo-second-order kinetic model and the Freundlich adsorption isotherm. Biosorption occurs on the mullein surface via multilayer adsorption. The reusability of mullein showed that the native biosorbents can be reused five times, showing the economic and sustainable benefit of this low-cost biosorbent material.

A Mechanistic Insight into the Acidic-stable MnSb2O6 for Electrocatalytic Water Oxidation.

The abundant, active, and acidic-stable catalysts for the oxygen evolution reaction (OER) are rare to the proton exchange membrane-based water electrolysis. Mn-based materials show promise as electrocatalysts for OER in acid electrolytes. However, the relationship between the stability, activity and structure of Mn-based catalysts in acidic environments remains unclear. In this study, phase-pure MnSb2O6 was successfully prepared and investigated as a catalyst for OER in a sulfuric acid solution (pH of 2.0). A comprehensive mechanistic comparison between MnSb2O6 and Mn3O4 revealed that the rate-determining step for OER on MnSb2O6 is the direct formation of MnIV=O from MnII-H2O by the 2H+/2e- process. This process avoids the rearrangement of adjacent MnIII intermediates, leading to outstanding stability and activity.

Highly Compressible, Superabsorbent, and Biocompatible Hybrid Cryogel Constructs Comprising Functionalized Chitosan and St. John's Wort Extract.

Biobased porous hydrogels enriched with phytocompounds-rich herbal extracts have aroused great interest in recent years, especially in healthcare. In this study, new macroporous hybrid cryogel constructs comprising thiourea-containing chitosan (CSTU) derivative and a Hypericum perforatum L. extract (HYPE), commonly known as St John's wort, were prepared by a facile one-pot ice-templating strategy. Benefiting from the strong interactions between the functional groups of the CSTU matrix and those of polyphenols in HYPE, the hybrid cryogels possess excellent liquid absorption capacity, mechanical resilience, antioxidant performance, and a broad spectrum of antibacterial activity simultaneously. Thus, owing to their design, the hybrid constructs exhibit an interconnected porous architecture with the ability to absorb over 33 and 136 times their dry weight, respectively, when contacted with a phosphate buffer solution (pH 7.4) and an acidic aqueous solution (pH 2). These cryogel constructs have extremely high compressive strengths ranging from 839 to 1045 kPa and withstand elevated strains of over 70% without developing fractures. Moreover, the water-swollen hybrid cryogels with the highest HYPE content revealed a complete and instant shape recovery after uniaxial compression. The incorporation of HYPE into CSTU cryogels enabled substantial improvement in scavenging reactive oxygen species and an expanded antibacterial spectrum toward multiple pathogens, including Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and fungi (Candida albicans). Cell viability experiments demonstrated the cytocompatibility of the 3D cryogel constructs, which did not induce changes in the fibroblast morphology. This work showcases a simple and effective strategy to immobilize HYPE extracts on CSTU 3D networks, allowing the development of novel multifunctional platforms with promising potential in hemostasis, wound dressing, and dermal regeneration scaffolds.

Aging properties of polyethylene and polylactic acid microplastics and their adsorption behavior of Cd(II) and Cr(VI) in aquatic environments

In this study, we examined the aging characteristics of polyethylene (PE) and polylactic acid (PLA) microplastics (MPs), examining the adsorption behaviors and mechanisms concerning Cd(II) and Cr(VI) under both single and binary systems. The results revealed that aging treatment changed the physicochemical properties of MPs. The aging mechanisms of PLA and PE MPs were shown to be similar by the 2D-FTIR-COS study. These mechanisms involve the formation of oxygen-containing functional groups through the combination of carbon chain breakdown and oxygen. Aged MPs had a greater ability to adsorb metal ions than pristine MPs, with PLA MPs outperforming PE MPs. After 30 days of aging, Cd(II) adsorption increased by 40.61 % and 25.49 % for PE and PLA MPs, respectively, while Cr(VI) adsorption increased by 37.50 % and 69.29 %, respectively. The adsorption ability of PE and PLA MPs with Cd(II) or Cr(VI) under binary systems was less than that under single systems, with Cd(II) exhibiting more adsorption competitiveness than Cr(VI). Humic acid (HA), ionic species and strength, solution pH, and adsorption of Cd(II) and Cr(VI) were found to be significantly correlated. Further investigation into the adsorption mechanisms of Cd(II) and Cr(VI) on PE and PLA MPs revealed that pore-filling, electrostatic interactions, complexation, and hydrogen bonding play important roles in the adsorption process. The study's conclusions are crucial for assessing the risk associated with concurrent contamination by metal ions and microplastics.

Development of an Efficient Process for the Separation of Co(ii), Mn(ii), and Ni(ii) from Chloride Solution by Precipitation

ABSTRACT The demand for nickel, cobalt, and manganese is increasing owing to their critical role in the performance of lithium-ion batteries. Precipitation is simpler to operate than solvent extraction in the separation of metal ions. In this work, precipitation-based procedures were developed to separate Co(II), Mn(II) and Ni(II) from synthetic chloride solutions. Dimethylglyoxime (DMG) was effective in selectively precipitating Ni(II) from the chloride solutions containing Co(II) and Mn(II). Solution pH greatly affected the precipitation of Ni(II) by DMG. In the first procedure, Ni(II) was first precipitated using DMG from solution with initial pH 6 at a DMG/Ni(II) molar ratio of 3, a reaction time of 30 min and then Co(II) was separated from the filtrate by precipitation with Na2S, with optimal conditions being an initial pH of 6, a Na2S/Co(II) molar ratio of 2 and a reaction time of 15 min. In the second procedure, both Ni(II) and Co(II) was simultaneously precipitated with Na2S, leaving Mn(II) in the filtrate. Then the mixed sulfides of Co(II) and Ni(II) were dissolved by using HCl solution containing NaClO as an oxidizing agent. From the leaching solution, Ni(II) was separated by precipitation with DMG. Optimum conditions for the separation conditions were obtained. In both procedures, the separation degree among the three metal ions was higher than 99%. The developed procedures were simple and effective for the separation of the three metal ions compared to solvent extraction.

A Chemically Robust 2D Ni-MOF as an Efficient Heterogeneous Catalyst for One-Pot Synthesis of Therapeutic and Bioactive 2-Amino-3-Cyano-4H-Pyran Derivatives.

Despite possessing numerous catalytic advantages of MOFs, developing 2D frameworks having excellent chemical stability along with new catalytic properties, remains a grand challenge. Herein, by employing a mixed ligand synthetic approach, we have constructed a 2D Ni-MOF, IITKGP-52, which exhibits excellent framework robustness in open air, water, as well as over a wide range of pH solutions (2-12). Benefitting from its robustness and abundant Lewis acidic open metal sites, IITKGP-52 is explored in catalyzing the heterogeneous three-component condensation reaction for the tandem synthesis of bioactive 2-amino-3-cyano-4H-pyran derivatives with low catalytic loading, greater compatibility for a wide range of substrates, excellent recyclability and superior catalytic efficiency than the previously employed homo and heterogeneous systems. IITKGP-52inaugurates the employment of MOF-based catalysts for one-pot synthesis of therapeutic and bioactive 2-amino-3-cyano-4H-pyran derivatives.

A Chemically Robust 2D Ni-MOF as an Efficient Heterogeneous Catalyst for One-Pot Synthesis of Therapeutic and Bioactive 2-Amino-3-Cyano-4H-Pyran Derivatives.

Despite possessing numerous catalytic advantages of MOFs, developing 2D frameworks having excellent chemical stability along with new catalytic properties, remains a grand challenge. Herein, by employing a mixed ligand synthetic approach, we have constructed a 2D Ni-MOF, IITKGP-52, which exhibits excellent framework robustness in open air, water, as well as over a wide range of pH solutions (2-12). Benefitting from its robustness and abundant Lewis acidic open metal sites, IITKGP-52 is explored in catalyzing the heterogeneous three-component condensation reaction for the tandem synthesis of bioactive 2-amino-3-cyano-4H-pyran derivatives with low catalytic loading, greater compatibility for a wide range of substrates, excellent recyclability and superior catalytic efficiency than the previously employed homo and heterogeneous systems. IITKGP-52inaugurates the employment of MOF-based catalysts for one-pot synthesis of therapeutic and bioactive 2-amino-3-cyano-4H-pyran derivatives.

Rare Earth Element Binding and Recovery by a Beta Roll-Forming RTX Domain.

The Block V of the RTX domain of the adenylate cyclase protein from Bordetella pertussis is disordered, and upon binding eight calcium ions, it folds into a beta roll domain with a C-terminal capping group. Due to their similar ionic radii and coordination geometries, trivalent lanthanide ions have been used to probe and identify calcium-binding sites in many proteins. Here, we report using a FRET-based assay that the RTX domain can bind rare earth elements (REEs) with higher affinities than calcium. The apparent disassociation constants for lanthanide ions ranged from 20 to 75 μM, which are an order of magnitude higher than the affinity for calcium, with a higher selectivity toward heavy REEs over light REEs. Most proteins release bound ions at mildly acidic conditions (pH 5-6), and the high affinity REE-binding lanmodulin protein can bind 3-4 REE ions at pH as low as ∼2.5. Circular dichroism (CD) spectra of the RTX domain demonstrate pH-induced folding of the beta roll domain in the absence of ions, indicating that protonation of key amino acids enables structure formation in low pH solutions. The beta roll domain coordinates up to four ions in extreme pH conditions (pH < 1), as determined by equilibrium ultrafiltration experiments. Finally, to demonstrate a potential application of the RTX domain, REE ions (Nd3+ and Dy3+) were recovered from other non-REEs (Fe2+ and Co2+) in a NdFeB magnet simulant solution (at pH 6).

Wheat growth, yield, nutrient concentration and soil chemical properties influenced by liming in an acid soil

Soil acidity has negative effects on both plants and soil. Furthermore, liming is the most common and effective management practice used to neutralize the acid produced in the soil and the problems associated with soil acidification. The study evaluated whether liming impacts wheat growth, yield, nutritional status basis exchangeable, and their related soil acidity indices. A greenhouse experiment was performed under a completely randomized arrangement, with four lime application rates equivalent to (0, 4.0, 8.0, and 12.0 Mg ha−1). The results showed that all yield components significantly increased with increasing lime addition rate. The grain yield, shoot and root dry weight, and plant and spike height improved quadratically (R 2 = 0.909, 0.950, 0.976, 0.902, and 0.891, respectively). Additionally, the lime rate influenced P and Mg concentrations in the shoot, and the concentrations of Cu and Zn. With increasing lime rate, the soil exchangeable Ca and Mg concentrations increased quadratically (R 2 = 0.969 and 0.984), while the soil exchangeable K and Al concentrations decreased significantly. The pH of the soil solution increased linearly (R 2 = 0.994) with the lime addition rate. Liming significantly reduced the exchangeable Al3+ and Al + H in the soil. Finally, liming improves wheat yield in acid soil by reducing the negative effects of Al and H by increasing soil pH, Ca2+, and Mg2+ concentration, consequently improving root growth and resulting in wheat yield. Liming increased the grain yield by 188.7, 198.2, and 322.8% following the increase of lime rate, if compared to the control. Furthermore, lime enhances plant resilience by raising pH and improving soil nutrient availability and the root system.