Low-concentration Solutions Research Articles

Design a variety of cation exchange hydrogel resins using gamma irradiation to remove hard/scale metal cations from saline water under different circumstances

This study aims to develop a series of cation exchange hydrogel resins via gamma irradiation technique through copolymerizing styrene sodium sulfonate with three acrylamide derivatives (designated as poly(X-co-styrene sodium sulfonate), where X refers to acrylamide (PAASS), methacrylamide (PMASS), and isopropyl acrylamide (PIASS)). The prepared hydrogel resins were characterized and tested for the adsorption removal of hard/scale metal cations (e.g., Ca2+, Mg2+, Ba2+, and Sr2+) from saline water under varying conditions. Results demonstrated that PMASS and PIASS displayed closed porous networks with a significant pH-responsive swelling behavior, increasing from 1.41 to 5.62 g/g in acidic conditions and approximately 41.49 to 45.83 g/g under neutral conditions swelling ratios, while PAASS exhibited an open porous network structure with the stable swelling ratio of around 35 g/g within mild and neutral pH ranges. All hydrogel resins also showed rapid initial adsorption of Ca2+ > Mg2+ > Ba2+ > Sr2+, depending on ionic metal size, with adsorption equilibrium within 3–6 h. Maximum removal was achieved at neutral-basic pH when sulfonate groups were fully deprotonated with a total capacity of about ~ 147–175 mg/g overall mixed metal ions. When exposed to lower concentration solutions, about 87% of metal ions were effectively removed.

Regulation of the physicochemical properties of nutrient solution in hydroponic system based on the CatBoost model

Too high or low nutrient solution concentrations adversely affect hydroponic vegetables’ growth and yield performance. In addition, the temperature of the solution and the dissolved oxygen (DO) content of the water are critical factors. A real-time regulation model for nutrient solutions based on the CatBoost model was developed to address the issues of low automation and accuracy of nutrient solution configuration and management. The pH, electric conductivity (EC) and DO of the nutrient solution, and the corresponding water temperature of 96 groups of hydroponic lettuce nutrient solutions (KNO3, MgSO4, Ca(NO3)2, KH2PO4, NH4H2PO4, and microfertilizer) were measured using a gradient combination test designed according to the formula of hydroponic lettuce nutrient solution. A prediction model of the nutrient solution index was constructed using a gradient-enhanced decision tree algorithm and the accuracies of the random forest, XGBoost, and CatBoost algorithms were compared. The results show that the root mean square error (RMSE), mean absolute error (MAE) and coefficient of determination (R2) of the simulated and measured values of the EC prediction model established by the CatBoost model were 248.28 µS/cm, 203.19 µS/cm and 0.946, respectively. At the same time, it was found that the hydroponic variable fertilization control system, composed of four modules–data acquisition, data decision, field control, and manual control–could predict the EC and pH value changes of the nutrient solution and timely add compounds for control. The application of nutrients based on the developed system was good and the weight of the cream lettuce (Flandria RZ) grown using the system was more than 200 g, which meets the requirement for high-quality cream lettuce production. Therefore, the CatBoost model system can be used to improve the hydroponic production system of vegetables by managing nutrients effectively.

Degradation of (1→3)(1→6)-α-D-dextran by ultrasound: Molecular weight, viscosity and kinetics

The (1→3)(1→6)-α-D-dextran (alternating dextran) produced by Leuconostoc citreum SK24.002 is a novel functional exopolysaccharide, and its low molecular weight derivatives have potential applications in the food, pharmaceutical, and chemical industries. In this work, we used sonication, a green polysaccharide disruption method, to study the degradation process of this dextran by changing the intensity and duration of the sonication treatment and the concentration of the dextran solution. The molecular weight and viscosity of the dextran products were measured with a high-performance size exclusion column chromatography–multi-angle laser light scattering–refractive index system and by rheometry, respectively. The degradation efficiency of dextran was directly affected by the duration and intensity of the ultrasonic treatment and the concentration of the dextran solution. The polydispersity index fluctuated as the duration of the sonication treatment increased. The combination of a high intensity (672 W/cm2) and long (120 min) sonication treatment and a low solution concentration (3 g dextran/100 mL) was most effective for reducing the apparent and complex viscosities of dextran. The storage modulus of dextran was always slightly larger than its loss modulus, indicating that it formed a gel-like structure. The second-order kinetic model (1/Mwt - 1/Mw0 = kt) was the best fit to explain the degradation dynamics of dextran by sonication at intensities of 168 W/cm2–834 W/cm2 and with dextran solution concentrations of 1 g/100 mL – 7 g/100 mL. Our findings show that sonication is an effective way to reduce the molecular weight of alternating dextran.

Adsorption of Heavy Metals from Low Concentration Solutions onto Dried Chlamydomonas reinhardtii

Adsorption of Heavy Metals from Low Concentration Solutions onto Dried Chlamydomonas reinhardtii

Identifying solute loss from karst conduit to fissures under concentrated recharge conditions

The aquifer within karst areas exhibits significant heterogeneity, accompanied by intricate runoff processes and swift hydrological responses. The solute transport process within karst conduits is influenced by various factors, including karst development characteristics and variations in hydrodynamic conditions, thereby displaying a high level of complexity. This complexity plays a crucial role in governing the safe utilization of karst water resources and the prevention of groundwater pollution. In this paper, a typical karst conduit system in southern China is chosen to investigate the influence mechanism of hydrodynamic conditions on the solute transport process within the karst conduit. This investigation is conducted through multiple sets of field artificial tracer tests. An intriguing phenomenon was observed: When the mean flow velocity of the conduit flow is either low (<200 m/h) or high (>1000 m/h), the solute concentrations and recovery rates are low. Conversely, the solute concentration and recovery rate are highest at a medium flow velocity (560 m/h), with the recovery rates ranging from 0.13 % to 92.44 %. A theoretical formula has been derived to estimate the solute loss from conduit flow to fissure flow. When the conduit is filled with water, an increase in the mean flow velocity leads to an augmentation in the amount of water recharged from the conduit into the fissures, as well as an increase in the stored solute mass, which results in a decrease in the solute recovery rate. The condition that poses the highest risk of groundwater pollution occurs at a medium flow velocity, where the solute concentration and recovery rate are all at their maximum levels. When the recharge rate at the sinkhole is very small, both the cross-sectional area and the mean flow velocity of the karst conduit are reduced. The rough bottom of the karst conduit leads to an increase in dispersivity, resulting in low solute concentration and recovery rate. The results elucidate the reasons behind the significant variations in solute recovery rates under different hydrodynamic conditions. They provide novel evidence for comprehending the water and solute exchange processes between conduits and fissures under concentrated recharge conditions. Furthermore, these findings offer a valuable reference for assessing the risk of groundwater pollution in karst areas.

Germination and Seedling Performance of Watermelon as Affected by Chemo-priming

Seed priming is a very important operation for healthy germination and seedling growth. Though a growing body of literature, the report on seed priming on watermelon is hardly available. Thus an experiment was conducted to study the germination and seedling performance of three watermelon cultivars viz. Asian 2, Pakorea F1 and Black Red with six seed priming treatments such as hydropriming with distilled water, halopriming with 1.5N NaCl and 3% KNO3, osmopriming with 3% PEG (Polyethylene Glycol), oxidative priming with 0.1N HCl solution and control i.e. no priming. The seeds were primed overnight with the aforesaid liquids and were allowed to grow both in petridishes in dark condition within laboratory and in pot soil under natural condition in an open grill house. All three watermelon cultivars showed significant difference due to seed priming with aforesaid primers. Germination Index (GI) was found higher in Asian 2 and Black Red cultivars due to HCl priming and in Pakorea F1 due to NaCl priming, while priming with PEG and KNO3 inhibited the GI of respective cultivars. Seedling Vigor Index (SVI) was found higher in Pakorea F1 with HCl priming whereas lower in Asian 2 and Black Red cultivars with PEG priming. Both in dark (Lab) and light (open field) conditions, total seedling dry matter was found higher in Asian 2 and Black Red cultivars due to HCl priming and lower in Pakorea F1 due to PEG priming. Results showed that low concentrated (0.1N) HCl solution can be used as priming medium to enhance germination and seedling growth of watermelon seeds.

Theoretical analysis and application of immobilized methanotrophs as typical adsorbent materials for adsorption/degradation of trichloroethylene

ABSTRACT Trichloroethylene (TCE) contamination presents a significant environmental challenge, necessitating efficient treatment solutions. This study aimed to develop an optimized immobilized bioreactor using methanotrophs for TCE degradation. Activated carbon fibres were identified as the optimal immobilization material, with an adsorption rate of 6–23 h – significantly faster than over 50 h for other materials – and the highest methane oxidation capacity of 0.970 mL·g−1·h−1. Adsorption kinetics indicated that activated carbon fibres followed a second-order kinetic model with a constant of 0.598 g·mg−1·h−1, suitable for low-concentration bacterial solutions. Thermodynamic analysis confirmed an exothermic process, favouring lower temperatures (288.15 K). The negative interaction energies, as per DLVO theory, suggested electrostatic attraction as a key mechanism. The bioreactor achieved 99% TCE removal within 1 h at an initial concentration of 10 mg·L−1, with visible microbial immobilization within 5 days. This research provides a novel and effective approach for using immobilized methane-oxidizing bacteria in TCE treatment, offering both theoretical and practical advancements for chlorinated hydrocarbon wastewater management.

Effect of synthesis temperature on the properties and photocatalytic performance of peroxo-titanate nanotubes prepared by bottom-up synthesis method

The alkaline treatment synthesis of titania/titanate nanotubes (TNTs) requires highly concentrated alkaline solutions (≥ 10 mol/L), which pose environmental and productivity limitations. In contrast, a bottom-up synthesis method for peroxo-titanate nanotubes (PTNTs) has been developed. This method offers two advantages: it can synthesize materials using low-concentration alkaline solutions (1.5 mol/L) and produce photocatalytic materials that are responsive to visible light. In general, the higher the crystallinity of a catalyst, the better its properties. However, PTNTs synthesized at temperatures close to their boiling point (around 100 °C) exhibit low crystallinity. This study hypothesizes a hydrothermal synthesis method at higher temperatures will enhance the crystallinity and photocatalytic performance of PTNTs, synthesizing them at temperatures ranging from 120 to 200 °C using a method capable of exceeding the boiling point. Higher synthesis temperatures resulted in improved morphological and crystallographic properties of the PTNTs. However, the formation of peroxo-bonding, crucial for visible light responsiveness, decreased. Nevertheless, peroxo-bonding formation was still achievable at the highest temperature of 200 °C, and the sample exhibited the best Rhodamine B (Rh B) photodegradation performance under visible light due to its enhanced specific surface area and crystallinity. This study highlights the novelty and environmental significance of hydrothermally synthesized PTNTs as superior photocatalysts by optimizing the synthesis temperature while using lower concentration alkaline solutions.

Amphiphilic pyrene-functionalized triazoliums for ATP recognition

Four pyrene functionalized triazolium salts with different lengths of alkyl tail from C4 to C16, i.e., PYTAZ-C4, PYTAZ-C8, PYTAZ-C12 and PYTAZ-C16, have been designed and synthesized for ATP recognition. It was revealed that the longer alkyl tail anchored receptors PYTAZ-C12 and PYTAZ-C16 exhibit low CMC values, and self-assemble nanoaggregation at low concentration in aqueous solution, which show a pyrene-based excimer emission at 496 nm. However, the shorter alkyl anchored receptors PYTAZ-C4 and PYTAZ-C8 give only the pyrene-based monomer emission at 380 nm at the test concentration of 10 μM in aqueous solution. Importantly, PYTAZ-C12 and PYTAZ-C16 exhibit a good fluorescence turn-on response toward polyphosphate anions, especially ATP, with the detection limits of 2.5 μM and 0.77 μM, respectively. Furthermore, probe PYTAZ-C16 was successfully used for fluorescence imaging of intracellular ATP in living cells.

Polyoxometalate oxate solution: An electrolyte additive to sustainably improve the anodes electrode of aqueous Zn ion batteries

Aqueous zinc-ion batteries (AZIBs) are favored by researchers because of their high safety performance and abundant zinc resources. In this work, low-cost was selected as the electrolyte additive to continuously improve the problems faced by the anode. Molybdenum-based solution can be reduced on the surface of zinc anode to form a uniform protective layer, and polyoxometalate can disperse metal elements more evenly, so that Zn2+ deposition is more uniform and AZIBs has more stable cycling performance. The symmetric battery assembled after adding Polyoxometalate oxate solution can maintain a stable potential of more than 1900 h at 5mA cm−2 and 1mAh cm−2, which is three times the cycle time of the battery assembled with ZnSO4 as the electrolyte (600 h). In addition, Mo has a certain anti-corrosion effect, which can prevent the corrosion reaction on the surface of zinc anode. The Tafel diagram shows that the corrosion current decreased from 1.995 mA cm−2 to 1.584 mA cm−2 after the addition of polyoxometalate oxate solution. The contrast effect is more obvious in SEM images. Different from the traditional zinc anode surface optimization, the addition of polyoxometalate oxate solution can continuously form auxiliary nucleation sites on the negative electrode surface to make Zn2+ deposition more uniform. When Na doped vanadium dioxide was used as the cathode to form full battery, the specific capacity could still reach 143.73mAh g−1 after 1000 cycles at the current density of 2 A/g. In this study, adding low concentration of polyoxometalate oxate solution to the electrolyte can continuously generate a stable protective layer during the battery operation, providing a feasible scheme for continuous improvement of AZIBs zinc anode.

Three-Dimensional (3D) Surface-Enhanced Raman Spectroscopy (SERS) Substrates for Sensing Low-Concentration Molecules in Solution.

The use of surface-enhanced Raman spectroscopy (SERS) in liquid solutions has always been challenging due to signal fluctuations, inconsistent data, and difficulties in obtaining reliable results, especially at very low analyte concentrations. In our study, we introduce a new method using a three-dimensional (3D) SERS substrate made of silica microparticles (SMPs) with attached plasmonic nanoparticles (NPs). These SMPs were placed in low-concentration analyte solutions for SERS analysis. In the first approach to perform SERS in a 3D environment, glycerin was used to immobilize the particles, which enabled high-resolution SERS imaging. Additionally, we conducted time-dependent SERS measurements in an aqueous solution, where freely suspended SMPs passed through the laser focus. In both scenarios, EFs larger than 200 were achieved, which enabled the detection of low-abundance analytes. Our study demonstrates a reliable and reproducible method for performing SERS in liquid environments, offering significant advantages for the real-time analysis of dynamic processes, sensitive detection of low-concentration molecules, and potential applications in biomolecular interaction studies, environmental monitoring, and biomedical diagnostics.

Bifunctional SnO2/NiO/rGO nanocomposite electrode for hydrogen evolution reaction and detection of winter wheat cold-resistant RNA.

Aconvenient, non-toxic, and low-cost tin dioxide (SnO2)/nickel oxide (NiO)/reduced graphene oxide (rGO) nanocatalytic electrode was investigated, which can effectively promote the hydrogen evolution reaction and can also be used to construct a sensitive winter wheat cold-tolerant RNA sensor. Due to the good synergy and photocurrent generation between SnO2 and NiO, which accelerates the electron transfer and catalyzes the hydrolysis reaction, the resultant data for the hydrogen evolution reaction in alkaline environment of this material are very impressive, with cathodic current densities of up to 10mAcm-2. The marvelous heterostructures and photovoltaic properties form a signal amplification system, which enables the nanocomposites to have an excellent linear sensitivity in low-concentration RNA solutions. The single-stranded complementary RNA of the target RNA was immobilized on the surface of the nanocomposites, which enabled the materials to recognize the target RNA under enzyme-free conditions. The test results showed that the modified electrode materials had good single detection performance in a wide linear range from 0.1nM to 2mM, with the limit of detection (LOD) of 0.078nM. The developed nanocomposite electrode has good performance in hydrogen evolution and winter wheat cold-resistant RNA detection, and is a bifunctional device with superior performance.

Thermal conductivity of binary Al alloys with different alloying elements

This work investigates the physical properties of several binary Al-Si/Ni/Fe/Cu/Mg alloys with varying alloying element contents and microstructures. The findings indicate that as the content of alloying elements increases, the number of secondary phases in binary Al alloys rises, and these phases become coarser. In hypereutectic compositions, primary phases in Al-Ni and Al-Fe alloys take on a needle-like morphology with high aspect ratios, forming a dendritic network. Regarding properties, in the hypoeutectic region, both thermal conductivity and electrical conductivity of binary alloys initially decrease sharply, followed by a more gradual decline with the addition of alloying elements. This trend occurs because thermal conductivity is mainly influenced by supersaturated solid solutions. In hypereutectic Al-Ni and Al-Fe alloys, the presence of large, needle-like primary phases significantly hinder the heat transfer, resulting in a more apparent reduction in both thermal conductivity and electrical conductivity. Among the five binary alloys, Al-Ni and Al-Fe alloys, which have lower solute concentrations of alloying elements in the Al matrix, exhibit the highest thermal and electrical conductivity. Furthermore, with increasing alloying element contents, the phonon thermal conductivity of Al-Si alloy increases more markedly compared to other alloys. The study will offer a fundamental understanding for the development of advanced alloys.

Nanosecond Pulse-Driven Oxygen Bubble Plasma Activation of Low-Concentration Alcohol Solutions and its Sterilization Mechanism.

To address the current use of high-concentration (70-75%) alcohol solutions as disinfectants, which are known for their drawbacks such as flammability and strong odor, a new approach based on nanosecond pulse-driven bubble discharge in low-concentration ethanol solutions is proposed. Research findings indicate that O2 bubble plasma activated ethanol solution (PAES) exhibits superior sterilization efficacy. A 3 min treatment using 10% alcohol eliminated all bacteria (reducing the bacterial count by 7 orders of magnitude) with an energy requirement of only 10.9 J/ml, whereas the same treatment with air PAES achieved less than a one-order reduction and O2/N2/air plasma activated water (PAW) achieved even less. Furthermore, to delve deeper into the key factors of PAES sterilization, concentrations of inorganic reactive species (H2O2, NO2 -, NO3 -, ONOO-, pH) and organic components resulting from alcohol decomposition (CH3CHO, CH3CH2OH, CH3COOH, and CH3COOOH) were analyzed using assay kits and GC-MS. Their variations at different storage temperatures (4 °C and -20 °C) were compared with the corresponding bactericidal effects. The results identified peroxyacetic acid (CH3COOOH) as a key bactericidal factor in PAES, showing that CH3COOOH over time at different storage temperatures correlated with their bactericidal effects. The study also revealed that O2 PAES stored at -20 °C maintained complete bacterial elimination even after 4 days. Therefore, PAES has the potential to replace high-concentration alcohol solutions for sterilization.

Formation of hierarchically structured martensites in pure iron with ultrahigh strength and stiffness

Strong steels are primarily fabricated by introducing spatial obstacles (e.g., stacking faults and precipitates) that inhibit dislocation slips under stress to achieve high strength. However, for most low-carbon steels, such obstacles are difficult to form mainly because the martensitic transition is kinetically unfavorable by conventional methods, which precludes the attainment of high-strength materials in these steels with low solute contents. Here, we report an innovative high-pressure preparation of martensitic pure Fe with involving nano-effect, which leads to the formation of ultrastrong bulk iron with exceptionally high yield strength, ultimate strength, and hardness of 2.9 GPa, 3.7 GPa, and 9.0 GPa, respectively, exceeding those of high-speed steels. Such extraordinary mechanical properties are closely attributed to its high-density martensites with unique multiscale hierarchical structures formed due to complex phase transitions under pressure.

Thermo-controlled microfluidic generation of monodisperse alginate microspheres based on external gelation.

Droplet-based microfluidic systems have received much attention as promising tools for fabricating monodisperse microspheres of alginate solutions with high accuracy and reproducibility. The immediate and simple ionotropic gelation of alginate, its biocompatibility, and its tunability of mechanical properties make it a favorable hydrogel in the biomedical and tissue engineering fields. In these fields, micron-sized alginate hydrogel spheres have shown high potential as cell vehicles and drug delivery systems. Although on-chip microfluidic gelation of the produced alginate droplets is common, several challenges remain. Complicated chemical and microfabrication processes are required, and the risk of microchannel clogging is high. In the current study, we present an easy-to-use microfluidic external gelation process to produce highly spherical and monodisperse microspheres from very low-concentrated alginate-RGD solution [0.5% (w/v)]. To accomplish this, gelatin, a thermo-sensitive and inexpensive biomaterial, was incorporated into the alginate solution as a sacrificial biomaterial that mediates the off-chip external gelation of the alginate with Ca2+, and avoids droplet coalescence. Utilizing the methodology mentioned above, we successfully generated monodisperse alginate microspheres (AMs) with diameters ranging from 27 μm to 46 μm, with a coefficient of variation of 0.14, from a mixture of Arg-Gly-Asp (RGD)-modified very low viscosity alginate and gelatin. These RGD-AMs were used as microcarriers for human umbilical vein endothelial cells. The described easy-to-use and cost-effective microfluidic off-chip external gelation strategy exhibits comparable advantages to on-chip external gelation and demonstrates superiority over the latter since clogging is impossible.

Improving oral absorption of a rapidly crystallizing parent drug using prodrug strategy: Comparison of phosphate versus glycine based prodrugs

With an increasing number of Biopharmaceutical Classification System (BCS) II/IV pipeline compounds, solubilizing and supersaturating formulation strategies are becoming prevalent. Beyond formulation and solid form strategies, prodrugs are also employed to overcome solubility-limited absorption of poorly water-soluble compounds. Prodrugs can potentially yield supersaturated systems upon conversion to the parent drug intraluminally and thus enhance absorption. However, supersaturation also increases the driving force for crystallization, resulting in low solution concentrations, which can potentially negate the advantage of prodrugs. In this work, two unique solubility-enhancing prodrugs, phosphate and glycine esters, were investigated for a rapidly crystallizing parent drug. Ex vivo absorption studies using rat tissue and in vivo studies in dogs were performed. Conversion rate of the phosphate prodrug to the parent was dependent on the milieu and increased ∼24-fold in the presence of intestinal contents as medium and tissue relative to neat buffer. In contrast, conversion of the glycine prodrug was minimal under any conditions tested, suggesting that the conversion occurs after absorption into the enterocytes. Phosphate prodrug showed a non-linear increase in parent drug absorptive flux across rat intestinal tissue with concentration when intestinal contents were used as donor media. This was attributed to rapid conversion and high supersaturation of the parent drug which subsequently resulted in crystallization at high doses in the donor chamber. Glycine prodrug did not undergo complete conversion at high doses and was absorbed unchanged on the basolateral side, indicating saturation of the converting enzymes in the enterocytes. The combined flux (parent drug and glycine) showed a linear increase with dose and crystallization was not observed. Under physiological conditions, glycine prodrug that is absorbed unchanged from the intestine can potentially undergo complete conversion in hepatocytes after absorption and make the parent drug systemically available. Thus, glycine prodrug provided overall higher absorption compared to phosphate prodrug. The observed flux levels for both the prodrugs were higher compared to the parent drug alone, highlighting an advantage to use of a prodrug strategy to improve absorption of such compounds. Oral dosing in a dog PK study revealed that the bioavailability using the phosphate prodrug was ∼50% whereas, it was ∼100% with glycine prodrug, supporting the in vitro observations.

Hierarchical pore-enhanced ion transport and defect-induced dual strong interactions for highly efficient lithium extraction

In the past decade, adsorption method has attracted great attention on the lithium extraction. The key issue in adsorption technology is to develop adsorbents with high adsorption capacity, selectivity, and recycle-stability. Here, the highly efficient metal–organic framework adsorbents were developed for lithium extraction, which were fabricated by the in-situ conversion of MIL-121 in alkali solution. The adsorbent after acid activation, termed as H-CAOMIL, was featured with the hierarchical porosity, enhanced density of free carboxylic groups, and exposed aluminum-oxygen defect sites to enhance the ion transport and provide dual strong interaction for Li+. H-CAOMIL exhibited the remarkable Li+ adsorption capacity (QLi+ = 5.28 mg/g) and selectivity (αKLi = 21.33, αNaLi= 9) from low-concentration lithium-containing solutions. Moreover, the H-CAOMIL can be easily regenerated in weakly acidic solution. Impressively, Li+ adsorption capacity retained at 92 % of the initial capacity even after five adsorption–desorption cycles. Furthermore, the comprehensive characterizations and theoretical calculations indicated that the specific coordination of COO-Li and AlO-Li played a crucial role in the recovery capacity and selectivity of Li+. This work offers precious insights for the future exploration of highly efficient adsorbents for lithium extraction.

Electrochemical recovery of ruthenium via carbon black nano-impacts

The recovery of ruthenium from low-concentration solutions poses a significant challenge due to its scarcity and rising economic value, and nano-impact electrochemistry has emerged as a promising method for efficient recovery of critical metals from solution through deposition during impacts of non-metallic nanoparticles. In this study, we investigate the redox chemistry of ruthenium on carbon black via the impact technique and demonstrate the ability to recover ruthenium from solution. The reduction (electrodeposition) and oxidation of Ru3+ ions in solution onto carbon black nanoparticles can be observed during nano-impacts with the respective onset potentials of these redox processes agreeing with those obtained from solution voltammetry. Upscaled experiments focusing on the electroreduction process, led to the formation of RuOx deposits, confirmed through scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) analysis, X-ray photoelectron spectroscopy (XPS) analysis, and thermogravimetric analysis (TGA). Under partially-optimised conditions, >90 % recovery of Ru(III) from a 1 mM solution was achieved in ca. 8 h.

Ion-selective electrode based on polyurethane-immobilized di-(2-ethyl hexyl) phosphoric acid for low-concentration aqueous Pb2+ detection and quantification

This study used a polyurethane (PU)-based ion selective electrode (ISE) immobilized with di-(2-ethyl hexyl) phosphoric acid (D2EHPA) to detect and quantify Pb2+ ions at low concentrations (10−10 to 10−1 M) in aqueous solution. PU, synthesized from castor oil (Ricinus communis L.), was utilized as the ISE membrane matrix. The ISE demonstrated a sensitivity of 26.24 ± 0.12 mV/decade, a detection limit of 1.44 × 10−7 M, and a response time of 10 s. We maintained the measurement stability for up to six days of storage.The results of Pb2+ quantification produced by ISE were compared with the results using atomic absorption spectroscopy (AAS), indicating similar Pb2+ concentrations in both artificial and real wastewater samples (calculated t-value < theoretical t-value). Therefore, this ISE is suitable for detecting trace levels of Pb2+ and quantifying them with high accuracy.