pH Range Research Articles

A Comparative Study on Chemical Speciation of Trace Metals as a Function of Solution pH: A Multivariate Analysis and Simulation Approach

ABSTRACT Biogeochemical activity of trace elements in the environment significantly relies on their chemical speciation. Solution pH influences the chemical speciation and biogeochemical activity of trace elements in the soil-plant continuum. The current study was conducted to simulate the influence of solution pH on chemical fractions of 11 trace elements (arsenic, lead, zinc, copper, chromium, cadmium, mercury, nickel, strontium, antimony, and selenium) using Visual Minteq, a chemical equilibrium model used for the calculation of metal speciation, sorption etc. Results delineated that pH-mediated variations in the chemical speciation of trace elements differed with their type. The results of the current study revealed a dominance of chemical trace element species at acidic (1–6), neutral (7.0), and alkaline (8–14) pH. Divalent trace elements (zinc, cadmium, copper, chromium, nickel, and lead) were the dominant species at acidic pH. However, mercury dominance has a narrow pH range (1–3), while strontium dominance has a wider pH range (1–13). Nitrate, sulfate, and phosphate fractions of trace elements also occurred at pH <8. However, at pH >8, trace elements existed in hydroxide (OH) fractions. In the case of arsenic (arsenite As3+ and arsenate As5+), selenium (selenite Se4+ and selenate Se6+), and antimony (antimonite Sb3+ and antimonate Sb5+), their dominant species get oxidized with increasing pH. Multivariate analysis was conducted for various metals for their dominance as a function of pH. Moreover, Principal Component Analysis verified a linear relation of trace element fractions with pH. Results revealed that solution pH affects the chemical fractions and the phytoavailable fraction of trace elements in growth culture and associated health hazards through soil-plant transfer.

CdSe/ZnS quantum dots-doped polymer optical fiber microprobe for pH sensing

pH is an important physiological parameter within organisms, playing a crucial role in functional activities in cells and tissues. Among various pH sensing methods, optical fiber pH sensors have gained a wide attention due to their unique advantages. However, current silica optical fiber-based pH sensors face some challenges such as weak biocompatibility, low biological safety, complex or unstable surface modification. Herein, we develop what we believe to be a novel pH sensor based on a CdSe/ZnS quantum dots-doped polymer optical fiber microprobe (POF MP) grown at the end of the silica optical fiber using the free radical photopolymerization process, which has the advantages of significant compactness, high flexibility, good biocompatibility, easy functionalization, high structural stability and safety. Moreover, the size of the POF MP are controllable, which is highly significant for applications requiring specific probe sizes or those used in special terrains. The proposed sensor is demonstrated to have a sensitivity of 0.18097/pH in a wide pH range from 4.5 to 9.0, while it exhibits a highly linear correlation between fluorescence intensity and pH value (R2 = 0.99448) and good reversibility and reusability. This proposed pH sensor offers a promising solution for pH monitoring in biological environments, contributing to advancements in biosensing, microenvironment monitoring, and potential therapeutic applications.

Characterization of Moroccan Raw and Modified Clay and Its Application in Removal of Methyl Orange Dye

ABSTRACTIn this work, we study the characterization of raw clay extracted from Jbel Lahbib Region of Tetouan in the north of Morocco, and organo‐modified clay by a cationic surfactant hexadecyltrimethylammonium bromide (CJL + HDTMA). In addition, we evaluate their potential to remove organic pollutants (methyl orange, MO) in aqueous solutions by means of the absorption techniques. All samples were characterized by XRD, FTIR, SEM‐EDAX, TGA, BET, and zeta potential. The XRD results show that the principal peak d001 moved from to Åfor the modified clay, the specific surface area of the raw and modified clay is 68.28 and 1.47 m2/g, respectively. Furthermore, these results confirm the success of this modification. With raw clay extracted from Jbel Lehbib (CJL), the maximum adsorption capacity of MO is pH‐dependent. Consequently, the MO adsorption is favored in the high acidic pH range. The adsorption kinetics of MO on both clays revealed that the equilibrium is rapidly obtained. Moreover, it is shown that the experimental data for MO adsorption on the two materials best fit the pseudo‐second‐order kinetic model. The adsorption isotherms indicate that the Sips and Temkin models correctly describe the adsorption of MO on the raw with experimental maximum adsorption value of 40.9 and 66.65 mg/g for raw and modified (CJL), respectively. The energy obtained from D‐R model (6.9 KJ/mol for raw clay and 12.86 KJ/mol for modified clay) suggested that process is dominated by physisorption for raw clay and chemisorption for modified clay. Besides, the thermodynamic study revealed that MO adsorption by crude clay is exothermic ( KJ/mol), physical, and spontaneous.

An azide-based sampler for monitoring abiotic reduction of chlorinated solvent contaminants in groundwater.

There is significant interest in monitoring abiotic decomposition of chlorinated solvents at contaminated sites due to large uncertainties regarding the rates of abiotic attenuation of trichloroethylene (TCE) and perchloroethylene (PCE) under field conditions. In this study, an innovative passive sampling tool was developed to quantify acetylene, a characteristic product of abiotic reduction of TCE or PCE, in groundwater. The sampling mechanism is based on the highly specific and facile click reaction between acetylene and an azide compound to form a biologically and chemically stable triazole product. In preliminary investigations using static solutions of acetylene, a strong linear relationship was observed between the quantity of azide formed and the concentration of aqueous acetylene. The product yield was stable within a solution pH range of 5-9 and in the presence of common groundwater salts or gaseous hydrocarbon molecules. Based on these results, a prototypical acetylene passive sampler was constructed, which featured a piece of PDMS membrane embedded with an azide compound and Cu(0) catalyst to form a reactive phase for acetylene capture. The sampler was evaluated in microcosm reactors containing TCE and an abiotic reductant (viz., sulfur-treated iron powder). Acetylene produced during abiotic dechlorination of TCE was effectively captured by the sampler, and the quantity of the product recovered from the sampler correlates with the amount of TCE converted. The specificity and sensitivity of the proposed acetylene sampler proffers a new diagnostic tool for monitoring abiotic degradation of chlorinated ethenes at complex contamination sites.

Impact of ions, pH and the nature of substrate on the structure and activity of a robust single-stranded DNA binding (SSB)-like protein from Phi11.

The gene gp13 in bacteriophage Phi11 has been annotated as a Single-Stranded DNA binding protein (SSB protein, GenBank accession no. NC_004615.1). SSB proteins protect Single-stranded DNA intermediates generated during replication, recombination, and repair from nuclease degradation by binding to them. This highlights the importance of SSB proteins in the DNA metabolic processes. In this investigation, we have reported a systematic analysis of the structural and functional changes induced in rGp13 (the gene product of gp13) by several factors, such as metal ions and buffers of varying pH. The nature and length of the substrate required for the optimum function of rGp13 has also been investigated. Our results suggest that rGp13 is a robust protein which maintains its structure and function over a wide range of pH, with pH 4 being an exception. The monovalent cations used in this study seemed to have a stabilizing effect on the protein. Interestingly, among the divalent cations studied, only Zn2+ ions were found to completely destabilise rGp13, with a complete loss of the parallel β-sheet and α-helical content of the protein. This, in turn, totally abolished the DNA binding activity of rGp13. Another interesting observation from this study was that rGP13 could also bind to double-stranded DNA molecules. In summary, SSBs bind to dsDNA, ensuring genome integrity, protecting ssDNA, and impacting transcriptional processes. These crucial functions highlight their significance in maintaining cellular stability.

Selective Novel Metal‐Coordinated Biomedical Agents Encompassing Tetradentate Salen Ligand: Structural Elucidation, DFT Calculation, Cytotoxic, and Antioxidant Activities Supported by Molecular Docking Approach

ABSTRACTSeveral physicochemical and analytical methods were employed to elucidate the structural analysis of some novel complexes derived from the {3,4‐bis‐[(3‐ethoxy‐2‐hydroxy‐benzylidene)‐amino]‐phenyl}‐phenyl‐methanone (ESAB ligand). Decomposition point determination, elemental analysis (CHN), spectroscopy (IR, NMR, and mass spectrometry), conductivity, magnetic susceptibility, UV–Vis spectrum study, and theoretical investigations were among these methods. With conductance values ranging from 7.5 to 15.12 Ω−1 cm2 mol−1, molar conductance values showed that the Zn (II), Cu (II), and Ru (III) complexes are nonelectrolytes in fresh DMSO solutions, with the exception of the ESABRu complex, which is a monoelectrolyte. According to IR spectra, the ligand uses the (N &amp; O) donor sites from the (C=N &amp; C‐O) groups in the ligand moiety to coordinate through the metal ions in a tetradentate form. A 1:1 (metal:ligand) molar ratio was proposed by Job's approach based on analytical data from solution complexation. According to the stability constant (Kf) values, the complexes' stability order was found to be ESABRu &gt; ESABCu &gt; ESABZn. The pH profile showed that the complexes under study are stable throughout a broad pH range, usually between pH = 4 and pH = 10. The complexes' geometric structures and ligand coordination capabilities were inferred with the use of magnetic and electronic spectrum studies. The DFT method uses quantum chemical simulations to evaluate the electronic structures of the ligand under investigation and its complexes. The unbound ligand's B3LYP level, B3LYP/6/311G* degree, and the complexes' B3LYP/6/311G**/LANL2DZ functional categories were employed in the computations of the density function concept (DFT). The findings revealed the consistency between the experimental and DFT computations. Natural bond orbital (NBO) analysis was used to investigate bond strength between molecules' charge exchange, hyperconjugative connections, and molecular equilibrium. By computing the hyperpolarizability (β) and molecular polarizability (α) parameters, the ensuing nonlinear optical properties were investigated, leading to a number of surprising optical properties for the produced compounds. The antipathogenic activity of the generated materials was experimentally verified against a subset of gram (+) and gram (−) bacteria as well as some fungi using the agar well diffusion method. Additionally, hepatic cellular carcinomas, cells from colon and breast cancer, were utilized to test the cytotoxic activity of the ESAB ligand and its metal chelates. Furthermore, the examined compounds' ability to suppress the DPPH radical was examined. Additionally, simulations of molecular docking were performed to ascertain how the produced compounds attached to the specific protein binding sites.

Highly Efficient Removal of Organic Pollutants with HCO3−-Enhanced Ru(III)/NaClO Process

The design of efficient advanced oxidation processes (AOPs) in the presence of bicarbonate has long attracted considerable attention in the field of environmental catalysis. In this study, sodium bicarbonate (NaHCO3) as one of the most abundant substances in actual water, was introduced to a NaClO/Ru(III) system to enhance the removal of acid orange 7(AO7). NaHCO3 could significantly improve the removal efficiency of the Ru(III)/NaClO process in HCO3− at a pH range of 6.9–10.0. Ru(V)=O was identified as a dominant reactive species involved in the degradation of pollutants in the NaHCO3/NaClO/Ru(III) system. HCO3− interacts with Ru(III) to generate Ru(III)-HCO3−, which enhances the activation performance of Ru(III) under neutral or alkaline conditions. The removal of AO7 was significantly enhanced with increasing NaHCO3 concentration, and the rate constant increased more than 2-fold to 4-fold as NaHCO3 concentrations increased from 0 to 100 mM at pH 6.9 and 8.5. This study proposed a novel strategy to enhance the Ru(III)/NaClO process with environmentally friendly inorganic ligands and highlights its potential applications in the removal of pollutants.

Influence of pH on Indium Deposition Rates: A Comprehensive Electrochemical Analysis

Abstract Binary indium-tin (In-Sn) and ternary indium-tin-bismuth (In-Sn-Bi) alloys hold significant promise for reducing soldering temperatures in electronic assembly. However, traditional metallurgical methods are unsuitable for fabricating micro-solder joints, making alloy electroplating essential for fine-pitch interconnects. The co-electroplating of alloy constituents is often hindered by substantial differences in reduction potentials. Therefore, sequential electroplating followed by high-temperature reflow emerges as a more practical solution. Nonetheless, challenges persist, particularly due to the limited understanding of indium (In) deposition kinetics and its strong dependence on pH. This study investigates the influence of pH on In plating rates and overall deposition kinetics. The thickness and cross-sectional morphology of electroplated In films are analyzed across a pH range of 2.2–3.3, with plating conditions optimized to identify the most effective parameters. Structural properties, uniformity, and potential oxide inclusions in the electroplated films are assessed using X-ray diffraction and differential scanning calorimetry. Plating at pH 2.9 in a solution of 0.12M In₂(SO₄)₃ and 0.70M Na₂SO₄ produces the highest deposition rate and the most structurally homogeneous layers. Deviations from this optimal pH inevitably promote side reactions that markedly reduce deposition rates and compromise film quality.

“Sichuanvirus”, a novel bacteriophage viral genus, able to lyse carbapenem-resistant Klebsiella pneumoniae

BackgroundCarbapenem-resistant Klebsiella pneumoniae (CRKP) is a severe threat for human health and urgently needs new therapeutic approaches. Lytic bacteriophages (phages) are promising clinically viable therapeutic options against CRKP. We attempted to isolate lytic phages against CRKP of sequence type 11 and capsular type 64 (ST11-KL64), the predominant type in China.ResultsWe recovered a lytic phage from sewage collected at a wastewater treatment station in Sichuan province, China. We obtained the genome of this phage and found that it is distinct from all known phages with the highest overall DNA similarity (12.5%, 16% coverage and 78.4% identity) with phage vB_EcoM_PHB05 (accession no. NC_052652) in ICTV. This phage represents a novel viral genus of the subfamily Stephanstirmvirinae, for which we proposed “Sichuanvirus” as the genus name. This phage has a narrow host range lyse specific for KL64 Klebsiella. This phage has no genes referring to antimicrobial resistance, virulence, and lysogen and is stable to a wide range of pH and temperatures. We also obtained three bacterial mutants resistant to the phage and performed genome sequencing for them. We therefore discovered that the interruption of a capsular polysaccharide biosynthesis-related gene wcaJ by insertion sequences mediated the resistance to this phage.ConclusionWe recovered and characterized a phage of “Sichuanvirus”, a novel viral genus of subfamily Stephanstirmvirinae, which is suitable for phage therapy. The discovery of this phage expands the arsenal against CRKP.

The Haemagglutinin Gene of Bovine-Origin H5N1 Influenza Viruses Currently Retains Receptor-binding and pH-fusion Characteristics of Avian Host Phenotype.

Clade 2.3.4.4b H5N1 high pathogenicity avian influenza virus (HPAIV) has caused a panzootic affecting all continents except Australia, expanding its host range to several mammalian species. In March 2024, H5N1 HPAIV was first detected in dairy cattle and goats in the United States. Over 891 dairy farms across 16 states have tested positive until 25th December 2024, with zoonotic infections reported among dairy workers. This raises concerns about the virus undergoing evolutionary changes in cattle that could enhance its zoonotic potential. The Influenza glycoprotein haemagglutinin (HA) facilitates entry into host cells through receptor binding and pH-induced fusion with cellular membranes. Adaptive changes in HA modulate virus-host cell interactions. This study compared the HA genes of cattle and goat H5N1 viruses with the dominant avian-origin clade 2.3.4.4b H5N1 in the United Kingdom, focusing on receptor binding, pH fusion, and thermostability. All the tested H5N1 viruses showed binding exclusively to avian-like receptors, with a pH fusion of 5.9, outside the pH range associated with efficient human airborne transmissibility (pH 5.0 to 5.5). We further investigated the impact of emerging HA substitutions seen in the ongoing cattle outbreaks, but saw little phenotypic difference, with continued exclusive binding to avian-like receptor analogues and pHs of fusion above 5.8. This suggests that the HA genes from the cattle and goat outbreaks do not pose an enhanced threat compared to circulating avian viruses. However, given the rapid evolution of H5 viruses, continuous monitoring and updated risk assessments remain essential to understanding virus zoonotic and pandemic risks.

Schlesneria sphaerica sp. nov., a neutrophilic, xylan-degrading planctomycete from a mountain wetland, and emended description of the genus Schlesneria.

Aerobic chemoorganotrophic planctomycetes of the genus Schlesneria colonize a wide spectrum of freshwater ecosystems. The only described species of this genus, S. paludicola, is represented by ellipsoid-shaped, moderately acidophilic bacteria isolated from acidic peat bogs. Here, we characterize a novel neutrophilic member of this genus from a mountain wetland, strain T3-172T. This isolate possesses unpigmented, non-motile, spherical cells, which grow on media containing some mono- and polysaccharides in the pH range of 6.0-7.5 and at temperatures between 15 and 37°C. Good growth is observed on xylan, one of the major plant cell wall biopolymers. The genome of strain T3-172T is 7.16 Mb in size and contains two unlinked sets of rRNA genes, 93 tRNA genes, and about 5500 potential protein-coding genes. Among the latter, the GH5 family protein is identified as the most reliable candidate for the cleavage of xylan. The 16S rRNA gene sequence of strain T3-172T displays 97.8% similarity to that of S. paludicola MPL7T, and the average nucleotide identity between the genomes of these planctomycetes is 71.6%. We, therefore, propose a novel species of the genus Schlesneria, S. sphaerica sp. nov., with strain T3-172T (=KCTC 102306T=VKM B-3856T) as the type strain.

Green-Emitting AIEgen for Fluorescent Switch-Off Detection of Multi-Cations and Applications.

An easy-to-synthesize aggregation-induced emission (AIE) active Schiff base HNSA was obtained by condensing equimolar amount of 3-hydroxy-2-naphthohydrazide and salicylaldehyde. In pure DMSO, HNSA is non-fluorescent, but increasing the HEPES (H2O, 10 mM, pH 7.4) fraction (fHEPES) ≥ 90% showed an intense green fluorescence with maximum fluorescence intensity at 515nm. The SEM analysis of HNSA at fHEPES 95% supported the formation of sheet-like self-aggregates of HNSA. The HNSA aggregates were found to be emissive over a wide pH range from pH 2.20 to 7.50. Further, metal ions sensing ability by AIE luminogen (AIEgen) HNSA was performed in fHEPES 95%. The fluorescence intensity of AIEgen HNSA was quenched by Co2+, Ni2+, Cu2+ and Fe2+ ions with an estimated detection limit of 0.43 µM, 0.48 µM, 6.26 µM, and 6.74 µM, respectively. AIEgen HNSA coated paper strips were developed for the visual detection of these metal ions. Also, AIEgen HNSA was successfully utilized to qualitatively detect metal ions in chickpea and lima bean sprouts. In addition, AIEgen HNSA was used to prepare green fluorescent gelatin gel and fluorescent invisible ink to write on filter paper to transfer confidential information. The probe AIEgen HNSA was employed to quantify metal ions in real environmental water samples.

Easy and Fast Detection of Hypochlorite by a Bithiophene-Based Fluorescent Turn-on Sensor and its Applications to Test Strips, Real Water Samples, and Smartphone-Assisted Platform.

We report a bithiophene-based fluorescence probe BDT (2,2'-(((1 E, 1'E)-[2,2'-bithiophene]-5,5'-diylbis(methaneylylidene))bis(azaneylylidene))bis(4-(tert-butyl)phenol)) for recognizing ClO-. BDT selectively responded to ClO-, leading to a blue fluorescence enhancement in a mixture of DMF/HEPES buffer (9:1, v/v). Importantly, BDT showed an ultrafast response (within 1 s) to ClO- among the fluorescent turn-on chemosensors based on bithiophene. BDT recognized ClO- through cleavage reaction with a low detection limit of 2.16 µM, and it had the ability to sense ClO- across a pH range of 3-11. The recognition mechanism for ClO- was investigated by 1H nuclear magnetic resonance (NMR) titration, electrospray ionization mass spectrometry (ESI-MS), and density functional theory (DFT) calculations. In addition, BDT could be used to detect ClO- using test strips as a convenient tool, allowing real-time monitoring rapidly. Practically, BDT exhibited reliable recoveries for quantifying ClO- using a smartphone application with a spike-and-recovery method in real water samples such as drinking, tap, mineral, and river water.

Sensitive Fluorescent Probe for Al3+, Cr3+ and Fe3+: Application in Real Water Samples and Logic Gate.

Construction of single probes for simultaneous detection of common trivalent metal ions has attracted much attention due to higher efficiency in analysis and cost. A naphthalimide-based fluorescent probe K1 was synthesized for selective detection of Al3+, Cr3+ and Fe3+ ions. Fluorescence emission intensity at 534nm of probe K1 in DMSO/H2O (9:1, v/v) was significantly enhanced upon addition of Al3+, Cr3+ and Fe3+ ions while addition of other metal ions (Li+, Na+, K+, Ag+, Cu2+, Fe2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Hg2+, Ca2+, Mg2+, Ce3+, Bi3+ and Au3+) did not bring about substantial change in fluorescence emission. The calculated detection limits were 0.32 µM, 0.81 µM, and 0.27 µM for Al3+, Cr3+, and Fe3+, respectively. Probe K1 displayed strong anti-interference ability, a large Stokes shift, rapid response, and applicability in a wide pH range for the simultaneous detection of Al3+, Cr3+ and Fe3+ in real water samples. Job's plot test showed that the stoichiometric ratio of the complexes formed between probe K1 and the trivalent metal ions was 1:1. The reversible application of probe K1 was realized by addition of Na2EDTA. A molecular logic gate was built based on the input-output information. This approach may provide a basis for highly selective and sensitive detection of common trivalent cations and for design of memory devices.

Bifunctional adsorbents based on hyper-cross-linked polymers containing carbonyl and amine species for the efficient removal of diclofenac from water in a broad pH range.

Development of new adsorbents for the efficient removal of organic pollutants from water is one of the most emerging environmental issues. Current studies in this field focus on improving the adsorption capacity of various materials and/or broadening the pH range in which the adsorbents can efficiently remove target pollutants. In this study, we designed bifunctional hyper-cross-linked polymers (HCPs) containing both carbonyl and amine species to investigate the effect of amine functional groups on the efficiency of adsorptive removal of non-steroidal anti-inflammatory drugs (NSAIDs) from water. We revealed that post-synthesis functionalization of carbonyl-rich HCPs with amine species does not have a significant impact on the adsorption capacity of these polymers under strongly acidic conditions (pH < 4; qe ∼ 544 mg/g), but significantly extends the pH range in which bifunctional polymers can adsorb diclofenac. For example, at native pH (pH ∼ 6), bifunctional HCP-based adsorbents exhibited an adsorption capacity approximately 8 times higher than that of pristine materials (qe = 191 vs. 24 mg/g, respectively). Furthermore, it was revealed that the adsorbents designed in this study can efficiently remove diclofenac from complex water matrices and exhibit high stability in several adsorption-desorption cycles. Moreover, we demonstrated that selecting a cross-linker with a longer chain results in a polymer with a lower surface area and smaller average pore size, while enabling higher efficiency in amine incorporation via post-synthesis functionalization. This latter feature was crucial for ensuring the high adsorption capacity of HCP-based adsorbents in the removal of NSAID at neutral pH.

Fabrication and simulation of silicon nanogaps pH sensor as preliminary study for Retinol Binding Protein 4 (RBP4) detection

In this research, a silicon nanogap biosensor has the potential to play a significant role in the field of biosensors for detecting Retinol Binding Protein 4 (RBP4) molecules due to its unique nanostructure morphology, biocompatibility features, and electrical capabilities. Additionally, as preliminary research for RBP4, a silicon nanogap biosensor with unique molecular gate control for pH measurement was developed. Firstly, using conventional lithography followed by the Reactive-ion etching (RIE) technique, a nanofabrication approach was utilized to produce silicon nanogaps from silicon-on-insulator (SOI) wafers. The critical aspects contributing to the process and size reduction procedures were highlighted to achieve nanometer-scale size. The resulting silicon nanogaps, ranging from 100 nm to 200 nm, were fabricated precisely on the device. Secondly, pH level detection was performed using several types of standard aqueous pH buffer solutions (pH 6, pH 7, pH 12) to test the electrical response of the device. The sensitivity of the silicon nanogap pH sensor was 7.66 pS/pH (R² = 0.97), indicating that the device has a wide range of pH detecting capacity. This also includes the silicon nanogap biosensor validated by simulation, with the sensitivity obtained being 3.24 μA/e.cm² (R² = 0.98). The simulation of the sensitivity is based on the interface charge (Qf) that represents the concentration of RBP4. The results reveal that the silicon nanogap biosensor has excellent characteristics for detecting pH levels and RBP4 with outstanding sensitivity performance. In conclusion, this silicon nanogap biosensor can be used as a new electrical RBP4 biosensor for biomedical diagnostic applications in the future.

Zr-based Metal-organic Framework [Zr6O4(OH)4(3.2b-ttdc)6] for Effective Mercury (II) Sorption from Water

Abstract: The objective of this work is to study MOFs with ligands containing thienothiophene groups as linkers and evaluate their practical application as sorbents for mercury removal from water. This evaluation will be compared with MOFs containing 2,6-naphthalenedicarboxylic acid and terephthalic acid linkers. The study of Hg2+ sorption from solutions was carried out by shaking the MOFs (10 mg) with the solution at 25 °C for 24 hours. Determination of chemical elements in solutions was performed using an Agilent 8800 triple quadrupole ICP-MS spectrometer (ICP-QQQ) equipped with an octopole reaction- collision cell in a standard configuration. Within 24 hours, 97.8% of Hg2+ ions were removed from the solution, even at an initial Hg2+ concentration as low as 1 mg·L-1. An important part of the work was studying the possibility Zr-ttdc regeneration for repeated use. Using iodide solution as a desorbing agent proved more productive, ensuring the desorption of Hg2+ through competitive complex formation due to the high stability constants of the corresponding mercury complexes. With a 0.1 M potassium iodide solution at pH 6.5, 99% of the sorbed mercury was desorbed in one desorption cycle. The efficiency of [Zr6O4(OH)4([3.2-b]ttdc)6] in adsorbing mercury from aqueous solutions was thoroughly evaluated and compared to [Zr6O4(OH)4(bdc)6] and [Zr6O4(OH)4(2.6-ndc)6], which lack sulfur- containing linkers. The findings highlight the potential of functionalized MOFs for water purification as well as application in analytical chemistry for the concentration of mercury. Notably, [Zr6O4(OH)4([3.2-b]ttdc)6] demonstrated stability in water in a wide pH range, underscoring its promise for diverse environmental chemistry applications. result: In this study, investigation of a new member of the MOFs family with thienylthiophenic acid (H2ttdc) as a dicarboxylate bridging ligand, were conducted. To elucidate the mechanism of mercury sorption by MOFs, a series of experiments were performed using sorbents based on various organic blocks, including 2,6-naphthalenedicarboxylic acid, thieno[3,2-b]thiophenic acid, and terephthalic acid. To evaluate the kinetics of the adsorption process, the effect of contact time on the sorption efficiency was studied. Within 24 hours, 97.8% of Hg2+ ions were removed from the solution, even at an initial Hg2+ concentration as low as 1 mg∙L-1. This demonstrates the high sorption efficiency of Hg2+ by Zr-ttdc from aqueous solutions. Depending on the source, a number of other elements (Cu, Pb, Zn, Fe, Mn, etc.) may also be present. Their influence on the efficiency of mercury sorption under optimal conditions was studied and it was shown that interfering effects from cations are practically absent. The situation is completely different for anions. Due to competitive complex formation, mercury sorption can be suppressed. It was shown that anions such as nitrate, sulfate, formate, and acetate at concentrations of 100 mg·L-1 do not affect mercury sorption efficiency. However, in the presence of chloride or iodide, sorption is suppressed. In the case of chloride, the sorption efficiency decreases to 90% and below when the chloride concentration in the solution is 50 mg/L and higher. An important part of the work was studying the possibility Zr-ttdc regeneration for repeated use. Using iodide solution as a desorbing agent proved more productive, ensuring desorption of Hg2+ through competitive complex formation due to the high stability constants of the corresponding mercury complexes. With a 0.1 M potassium iodide solution at pH 6.5, 99% of the sorbed mercury was desorbed in one desorption cycle. The feasibility of reusing the sorbent was demonstrated with potassium iodide solution regeneration over 6 sorption-desorption cycles.

Untangling the role of single-atom substitution on the improvement of the hydrogen evolution reaction of Y2NS2 MXene in acidic media.

The production of hydrogen (H2) fuel through electrocatalysis is emerging as a sustainable alternative to conventional and environmentally harmful energy sources. However, the discovery of cost-effective and efficient materials for this purpose remains a significant challenge. In this study, we explore the potential of the transition-metal-substituted Y2NS2 MXene as a promising candidate for hydrogen production through the hydrogen evolution reaction (HER). Using density functional theory (DFT) calculations, we first analyzed the Pourbaix diagram, and dissolution potential which showed the stability and resistance to corrosion of the sulfur termination. Later, we address the kinetic limitations of HER on bare Y2NS2 by introducing single-atom substitutions of Y atoms with 3d transition metals. Nine distinct structures were evaluated, revealing that Fe-substituted Y2NS2 exhibits the highest HER activity under acidic conditions, as indicated by volcano plot analyses. Further investigation of the bonding characteristics and electronic density of states highlights the crucial role of Fe d-orbitals and the weak interactions at the sulfur-terminated surface in enhancing the HER efficiency. These findings provide insights into the design of advanced, cost-effective materials for HER catalysis, paving the way for their application as efficient electrochemical catalysts across a wide pH range.

Synthesis of zirconium-based metal-organic framework/gelatin aerogel for removing phosphate and fluoride from aqueous solutions.

This study describes the preparation of novel hybrid aerogels derived from gelatin (Gel), incorporating Br-functionalized zirconium-based metal-organic framework (UiO-66-Br; MOF) as modifying agent to effectively eliminate phosphate and fluoride ions from aqueous environments. The adsorption performance of MOF decorated Gel (Gel-xMOF) hybrid aerogels was investigated under different conditions, including agitation time, adsorbent dosage, solution pH, initial phosphate and fluoride concentrations, coexisting ions, and temperature. The functional groups of the gelatin network, coupled with UiO-66-Br, enhanced the adsorption performance of phosphate and fluoride ions from aqueous solutions. The structural features and physicochemical parameters were evaluated using several characterization tools. The mesoporous Gel-1.5MOF aerogels exhibited Langmuir adsorption capacities of 20.81 and 7.42 mg/g for phosphate and fluoride, respectively. Reusability and coexisting experiment results suggest that the as-prepared Gel-1.5MOF aerogels have the potential for practical applications. Electrostatic attraction and ligand exchange primarily govern the adsorption mechanism of both ions, followed by hydrogen bonding and pore-filling mechanisms. This investigation offers new insights into the successful elimination of phosphate and fluoride ions across a broad pH range.

Dolomite dissolution, pH neutralization, and potentially toxic element immobilization in stormwater bioretention beds.

The importance of pH in stormwater bioretention beds cannot be overstated since it impacts plant and microbial populations and removal of potentially toxic elements (PTEs) from stormwater runoff. This study investigated the effects of dolomite amendment on pH neutralization and subsequent PTE immobilization in bioretention media. To assess dolomite dissolution, pH neutralization, and PTE immobilization, engineered bioretention media was amended with different dolomite ratios and samples of dolomite-amended media were collected from two bioretention beds, one and two months after installation. The effects of inflow conditions and operational time on dolomite dissolution and PTE immobilization were investigated through a column study. Laboratory batch experiments revealed that pH neutralization was fast and reached the recommended pH range of 5 to 8 within 5min. Among the 1-D column conditions, intermittent inflow had the highest porewater Mg and Ca concentrations, indicating greater dolomite dissolution. Batch experiments on field-collected media showed that pH neutralization was substantial within 1month, and continued during the second month, due to dolomite dissolution. Dissolved (batch experiments) and column porewater Mg and Ca concentrations supported instantaneous Ca and a relatively slow Mg dissociation during dolomite dissolution. Among the monitored PTEs, dissolved and porewater concentrations (μg/L) were found to decrease with time, in the order Mn>Fe>Zn>Cu>Pb>Cd, with Cr mainly undetected in all experimental conditions. However, as pH became neutralized to slightly basic (pH~8), dissolved and porewater As concentrations increased. The study suggests that pH neutralization and PTE immobilization depend on the soil-to-dolomite ratio and hydrological properties such as inflow rate, dry-wet cycle, and soil-water contact time. Dolomite amendment to engineered media can be an effective measure for intercepting contaminants, improving ecosystem health, and enhancing biochemical contaminant breakdown, though consideration should be given to bioretention bed design features and system hydrology.