Water Solution Research Articles

Performance of metakaolin-based geopolymer molecular sieve microspheres on dynamic recovery of Cu (II)

This study reports the in-situ transformation of geopolymers into molecular sieve using a method with mild conditions. The application of geopolymer zeolites for dynamic adsorption in continuous fixed beds has been less studied, and the application of adsorbents after adsorption has been less studied. Different metakaolin-based geopolymer molecular sieve microspheres (NaA-MSM, SOD-MSM) were prepared by in-situ conversion of metakaolin as raw material and NaOH as an alkali activator. The continuous fixed-bed adsorption performance was evaluated by varying the influent flow rate, initial metal concentration, and adsorbent dosage. The maximum adsorption capacities of NaA-MSM and SOD-MSM for Cu (II) were 698.14 and 523.84 mg·g−1, respectively. In the simulated solution of real lake water, the adsorption capacities of NaA-MSM and SOD-MSM for Cu (II) were 202.94 and 154.97 mg·g−1, respectively. The results show that the synthesized molecular sieve is an excellent adsorbent for Cu (II)-containing wastewater, and the application design of recycling heavy metals in wastewater by adsorption technology and degrading dyes has been successfully constructed.

The structure of carbon dioxide at the air-water interface and its chemical implications.

The efficient reduction of CO2 into valuable products is a challenging task in an international context marked by the climate change crisis and the need to move away from fossil fuels. Recently, the use of water microdroplets has emerged as an interesting reaction media where many redox processes which do not occur in conventional solutions take place spontaneously. Indeed, several experimental studies in microdroplets have already been devoted to study the reduction of CO2 with promising results. The increased reactivity in microdroplets is thought to be linked to unique electrostatic solvation effects at the air-water interface. In the present work, we report a theoretical investigation on this issue for CO2 using first-principles molecular dynamics simulations. We show that CO2 is stabilized at the interface, where it can accumulate, and that compared to bulk water solution, its electron capture ability is larger. Our results suggests that reduction of CO2 might be easier in interface-rich systems such as water microdroplets, which is in line with early experimental data and indicate directions for future laboratory studies. The effect of other relevant factors which could play a role in CO2 reduction potential is discussed.

CONFORMATIONAL PARTICULARITIES OF A(25-35) PEPTIDE DETERMINED BY INFRARED SPECTROSCOPY

The Alzheimer’s amyloid-β (25-35) peptide retains the toxicity and ability to aggregate of the amyloid-(1-40) peptide. The study of the conformational properties of Aβ (25-35) peptide in its soluble monomeric form can play an essential role in determining the mechanism of oligomerization. In this study, we probed the secondary structure of a soluble Aβ (25-35) peptide in water solution at physiological conditions (pH 7.4). We have used Fourier Transformed Infrared Spectroscopy (FTIR) to examine the secondary structure of this peptide. The amide I bands of A (25-35) obtained from transmission-FTIR spectra consists of one main band at 1658 cm-1, at both concentrations used (200 M and 1 mM). This band show us that A (25-35) in aqueous solution was mostly organized into a -helical structure (48%). The contribution of the unordered structure was found to be about 12%. The proportion of -sheet and -turn structures are slightly lower, 12-15% and 13-14%, respectively for both concentrations. FTIR spectra of the peptide in water solution (100 µM) after incubation for 12h showed Aβ peptide conformation is critically dependent on the environmental conditions used.

Structure Formation by 3D-Printing of Cellulose from Cellulose-NMMO-Water Solutions: Analysis of Extrusion, Regeneration, and Drying Stages.

Processing cellulose from 4-methyl morpholine n-oxide (NMMO)-water solutions is a completely circular route that produces biodegradable cellulose fibers or films while recovering reusable NMMO [Guo, Y.; Cai, J.; Sun, T.; Xing, L.; Cheng, C.; Chi, K.; Xu, J.; Li, T. The purification process and side reactions in the N-methylmorpholine-N-oxide (NMMO) recovery system. Cellulose 2021, 28(12), 7609-7617]. Despite proven success in two-dimensional applications, challenges in transitioning to three-dimensional objects arise from the critical changes that cellulose undergoes during deposition, regeneration, and postregeneration stages. While emphasizing the critical diffusion-driven precipitation during regeneration, this investigation explores the influence of extrusion temperature, printing alignment, regeneration, and drying processes on interfilament fusion, bonding, shape integrity, and mechanical properties. Three distinct drying processes: ambient, vacuum, and freeze-drying were investigated. Tensile and flexural bending tests provided insight into the delamination of dried specimens. Ambient and vacuum drying enhanced the properties of specimens, while freeze-drying resulted in a more stable shape. The findings contribute to advancing the understanding of 3D-printing cellulose from NMMO solutions, addressing crucial aspects of the extrusion, regeneration, and drying stages for enhanced applications in sustainable manufacturing.

Ecological regulation of chemical weathering recorded in rivers

We provide a new generalized framework accounting for the effects of water and nutrient uptake by roots in the weathering zone on broad patterns of solute concentration - discharge relationships in rivers. As plants withdraw water from the subsurface, they decrease the area-normalized fluid drainage rate. This results in a discharge flux to springs and streams which is a function of water use by plants, leading to ecosystem regulation of the characteristic timescales of chemical weathering reactions and fluid flow rate. Our predictive framework quantifies the pore water and river solute chemistry generated from water-rock interactions, regulated by the effects of vegetation on water flow rates. To this we add the capacity for vegetation to enrich, passively admit, or discriminate against a given dissolved solute based on ecophysiological needs, thus further modifying the local concentration of a given chemical species in solution across a weathering profile. This uptake flux is not lost to the atmosphere in the same manner as water is removed from the subsurface via evapotranspiration. Rather, these extracted chemical species become incorporated into the topsoil as litter which may be partially or fully resolubilized, creating an upper boundary condition which depends on the uptake and recycling characteristics of the ecosystem. These processes are united through a new solution to the advection-reaction equation which allows vegetation to regulate broad patterns of stream concentration - discharge relationships. We show that ecosystems are capable of both accelerating and impeding water-rock reaction rates across the weathering profile, ultimately leading to both thermodynamic and ecological controls on the baseflow concentration of rock-derived solutes in rivers.

Electrodeposition of MnAs-Based Thin-Film as a Possible Promising Candidate in Spintronics Applications

A thin film material obtained by Mn As co-electrodeposition was electrochemically deposited. Electrodeposition was chosen because is a versatile and easily scalable technique with low costs, and achievable under ambient conditions in water solution. These advantages are often unmatched by the typical production routes of spintronic materials. The use of different substrates was investigated, and the optimal deposition conditions were sought to reach the required morphology and composition, considering also the influence of pH and O2. The deposition conditions were optimized using multivariate analysis. The samples were characterized morphologically, crystallographically, and compositionally with SEM-EDS, XRD, and XPS, suggesting that the deposit chemical composition was predominantly constituted by MnAs and MnO2. Magnetic characterization performed with a SQUID magnetometer showed that the sample disclose a ferromagnetic component. MnAs and MnO2 are known to have properties suitable for applications in spintronics, making this system interesting as an alternative for spintronic-based devices.

Impact of polyglycidol block architecture in polystyrene-b-polyglycidol copolymers on the properties of thin films and protein adsorption

The effect of the architecture of amphiphilic polystyrene-b-polyglycidol and polystyrene-b-(polyglycidol-g-polyglycidol) copolymers on their behavior in thin films and interaction with the protein has been studied. The properties of the copolymer films surface were investigated before and after incubation in water and aqueous solution of PBS buffer. Surface sensitive techniques: time-of-flight secondary ion mass spectrometry, atomic force microscopy, and contact angle measurements show the differences in film surfaces behavior depending on the copolymer architecture. It was found that exposure of the coil-brush copolymer to an aqueous solution reoriented the PGL segments, changing the properties of the surface layer. Greater exposure of antifouling PGL chains at the surface of the copolymer film modified the interaction with bovine serum albumin, significantly reducing its adsorption. In contrast, no changes in the orientation of the PGL chains were observed after incubation of the copolymer films in an aqueous solution of protein in PBS buffer. This suggests that protein adsorption to the thin copolymer film blocks the conformational changes of the copolymer chains and reduces their mobility under the protein molecules.

A Metal Accelerator Approach for Discharging Cylindrical Lithium-Ion Batteries in a Salt Solution

Recycling lithium-ion batteries provides sustainable raw materials. Crushing and separation are necessary for extracting metals, like lithium, from batteries. Crushing a battery carries a risk of fire or explosion. Fully discharging the battery is crucial for safe production. Discharging batteries in a salt solution is a simple and cost-effective large-scale process. However, it is important to note that there is a potential risk of corrosion and loss of battery elements when batteries are immersed in a salt solution. The purpose of this study is to investigate the effectiveness of two distinct methodologies at enhancing the voltage drop of a cylindrical battery when immersed in a salt solution while preventing corrosion. These techniques involve the application of iron and copper accelerators. A 20 wt.% salt water solution was chosen based on the research of several researchers. As the current flows through the metal parts, it encounters electrical resistance and forms an electric circuit with the electrolyte solution. This interaction converts electrical energy into various physical–electrical–electrochemical phenomena, leading to a decrease in battery voltage. Research revealed that the battery can be discharged up to 100% within 4 h without causing corrosion to its components. Another point to note is that if copper conductors are used, it is possible to decrease the battery voltage by around 90% within 8 h. The gap between the copper conductor and the battery had a direct impact on the battery’s discharge rate. Reducing the distance significantly increased the discharge rate, as confirmed by experimental evidence. This discharge mechanism was thoroughly described in a schematic, and, to further explain the electrochemical reaction, the Pourbaix diagram was utilized for both the Fe-Na-Cl and Cu-Na-Cl systems. Moreover, our theoretical predictions were validated through a chemical and mineralogical analysis of the precipitates that formed in the solution.

Enzyme activity test paper with high wet strength and anion adsorption properties fabricated from whole cationized softwood chemical fiber

Paper-based test film material is widely used in a variety of test instruments for different applications. The enzyme activity test paper sheet is one of the most popularly used test papers. Here we present a novel fabrication of paper-based enzyme activity test paper without cationic resin added in. The chemical pulping fibers were first beaten to different degrees (from 14.6 to 41.5°SR) with a PFI beater. After that, the fibers were modified with a cationic agent (3-chloro-2-hydroxypropyl trimethyl ammonium chloride) under the system of alkali and water solution. Finally, the test papers were made with the modified fiber by a regular paper former in lab. The results showed that beating is beneficial for the improvement of the cationization reaction which is indicated by the Zeta potential, FTIR and EDS. The main mechanisms involved are the destruction of crystalline zone, increase of free hydroxyl group and defibrillation. This hypothesis was supported by the SEM, XRD and fiber analyzer. Beating under the optimized condition, the wet strength and liquid absorbability of test paper can meet the application requirement, and the test results of enzyme activity are quite close to those of commercial test papers.

Tuning pore size and density of rigid polylactic acid foams through thermally induced phase separation and optimization using response surface methodology

Rigid polylactic acid (PLA) foams fabricated via thermally induced phase separation (TIPS) utilizing a ternary solution of PLA, Tetrahydrofuran (THF), and water. The PLA gels were stabilized mechanically by the substituting of the THF/water solvent mixture with ethanol as non-solvent and subsequently vacuum dried. A comprehensive characterization of PLA foams was achieved by Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD) and Brunauer–Emmett–Teller (BET) analyses. The BET area obtained in the PLA foam is up to 18.76 m2/g. The Response Surface Methodology (RSM) was utilized to assess the impacts of four independent variables (polymer concentration, solvent composition, quench temperature, and aging time) on the pore size and density of PLA foam. The experimental findings demonstrated that the fabrication parameters could be fine-tuned to govern the morphology of the pores, comprising their size and density. The optimal values of parameters for cell size were identified by RSM to be 8.96 (wt%), 91.60 (w/w), 5.50 °C, and 3.86 h for the optimum cell size of 37.96 µm (37.78 by Genetic Algorithm). Optimum density by RSM 88.88 mgr/cm3 (88.38 mgr/cm3 by Genetic Algorithm) was obtained at 5.00 (wt%), 89.33 (w/w), 14.40 °C and 2.65 h.

Influence of acidity and alkalinity of water environment on water stability of asphalt mixture: Phase II-microscopic erosion mechanism

Acidity and alkalinity of water environments have been proven to influence the water stability of asphalt mixture. However, the relevant influencing mechanism still remains unclear. To fulfill this research gap, this study conducted a series of microscopic tests, aiming at unveiling the microscopic erosion mechanism of the water environment on the water stability of asphalt mixture for better moisture stability achieved. Specifically, the asphalt-aggregate interfacial transition zone (ITZ) samples were prepared by combining #70 asphalt with limestone and granite, respectively, which were then immersed in water solutions at 3 different pH levels (pH = 3.0, 7.0, and 11.0) for 7 days. The chemical composition and microstructure of the asphalt film on the surface of the ITZ samples pre and post-treatment were scrutinized using the Fourier Transform Infrared Spectroscopy (FTIR) and the Atomic Force Microscope (AFM), while the development of microcracks at the asphalt-aggregate interface were identified and traced utilizing the Scanning Electron Microscope (SEM). The test results indicate that after treatment with acidic and alkaline aqueous solutions, the asphalt film's surface is enriched with polar components such as asphaltenes, resins, and aromatic fractions. The migration of these polar components to the surface of the asphalt film reduces the adhesion between asphalt-aggregate, leading to the formation of microcracks at the asphalt-aggregate interface. The most severe crack development occurs in alkaline water environment, followed by acidic water environment. It is interestingly noted that the adhesion at the asphalt-granite interface is improved under the acidic environment. This improvement may be attributed to the covalent nature of silica, which hinders the adsorption of ions from acidic solution into the asphalt film. This hindrance effectively prevents water intrusion at the asphalt-aggregate interface, thereby reducing the adhesion loss. These findings can help elucidate the mechanism of water damage in asphalt pavement exposed to real-world conditions and enhance its water stability with effective countermeasures proposed.

Biomimetic Charge‐Neutral Anion Receptors for Reversible Binding and Release of Highly Hydrated Phosphate in water

Control of phosphate capture and release is vital in environmental, biological, and pharmaceutical contexts. However, the binding of trivalent phosphate (PO43‐) in water is exceptionally difficult due to its high hydration energy. Based on the anion coordination chemistry of phosphate, in this study, four charge‐neutral tripodal hexaurea receptors (L1 ‐ L4), which were equipped with morpholine and PEG terminal groups to enhance their solubility in water, were synthesized to enable the pH‐triggered phosphate binding and release in aqueous solutions. Encouragingly, the receptors were found to bind PO43‐ anion in a 1:1 ratio via hydrogen bonds in 100% water solutions, with L1 exhibiting the highest binding constant (1.2´103 M‐1). These represent the first neutral anion ligands to bind phosphate in 100% water and demonstrate the potential for phosphate capture and release in water through pH‐triggered mechanisms, mimicking native phosphate binding proteins. Furthermore, L1 can also bind multiple bioavailable phosphate species, which may serve as model systems for probing and modulating phosphate homeostasis in biological and biomedical researches.

Biomimetic Charge-Neutral Anion Receptors for Reversible Binding and Release of Highly Hydrated Phosphate in water.

Controlof phosphate capture and release is vital in environmental, biological, and pharmaceutical contexts. However, the binding of trivalent phosphate (PO43-) in water is exceptionally difficult due to its high hydration energy. Based on the anion coordination chemistry of phosphate, in this study, four charge-neutral tripodal hexaurea receptors (L1 - L4), which were equipped with morpholine and PEG terminal groups to enhance their solubility in water, were synthesized to enable the pH-triggered phosphate binding and release in aqueous solutions. Encouragingly, the receptors were found to bind PO43- anion in a 1:1 ratio via hydrogen bonds in 100% water solutions, with L1 exhibiting the highest binding constant (1.2´103 M-1). These represent the first neutral anion ligands to bind phosphate in 100% water and demonstrate the potential for phosphate capture and release in water through pH-triggered mechanisms, mimicking native phosphate binding proteins. Furthermore, L1 can also bind multiple bioavailable phosphate species, which may serve as model systems for probing and modulating phosphate homeostasis in biological and biomedical researches.

Rapid preparation of Mo2CTx MXene by hydrothermal etching in ammonium hydrogen fluoride solution

In this paper, we report a novel method to rapidly prepare two-dimensional Mo2CTx MXene in a low-concentration etching solution. By this method, highly pure Mo2CTx MXene was synthesized from Mo2Ga2C by hydrothermal etching at 180 ℃ in the solution of ammonium hydrogen fluoride (NH4HF2). The whole process requires only 2 h and the etching solution concentration is only 1 M. Compared with the acid solutions used in other methods, NH4HF2 used in this method is in solid state and its water solution is mild for handling. Compared with other methods, this method requires a lower concentration of etching solution and a much shorter etching time. The Mo2CTx MXene made this method have comparable microstructure and properties with those made by other methods. The initial discharge capacity as an anode of lithium-ion batteries (LIB) was 139.35 mAh g-1 at 0.1 A g-1. After 150th cycles, the final discharge capacity was 62.42 mAh g-1 at 0.1 A g-1. The electrochemical performance is slightly higher than the sample made by general HF etching. This is the first report to make Mo2CTx MXene from the etching of bifluoride salt. Due to the short etching time and low concentration of the etching solution, this method can rapidly make Mo2CTx MXene at in low cost, which provides a route to explore the large-scale production of Mo2CTx MXene.

Synergistic effects of La-doping on ZnO nanostructured photocatalysts for enhanced MB dye degradation

In this work, we present the design and characterization of pristine and La-doped ZnO photocatalysts, prepared via a facile co-precipitation technique. A comprehensive range of characterization techniques was employed to analyze the physicochemical properties of these synthesized nanostructured photocatalysts. The slight shift in the position of peaks in the X-ray diffraction (XRD) pattern confirms successful doping (La3+) of ZnO. Additionally, the identified wurtzite phase further validates the presence of ZnO nanostructures. Subsequent photocatalytic investigations were conducted using model solutions of water and methylene blue (MB) dyes under solar irradiation, meticulously comparing the performance of pure ZnO with La3+ doped ZnO. Over the time span of 90 min, the 5 % La-doped ZnO photocatalysts exhibited an impressive 98 % degradation efficiency for MB dye, surpassing the performance of the pristine ZnO counterpart (0 % La), which achieved only 51 % degradation. This emphasizes the pronounced enhancement resulting from the incorporation of La ions. The photoluminescence (PL) spectra insights with 5 % La3+doping exhibit significant quenching, caused by the suppression of charge carrier recombination, which enhances the photocatalyst's charge transport. X-ray photoelectron spectroscopy (XPS) spectra provided crucial insights into the elemental composition and chemical states of the 5 % La3+ doped ZnO nanostructures. Through systematic reusability assessments, it was established that the 5 % La-doped ZnO photocatalysts maintain their efficiency for up to four cycles, without displaying a significant reduction in removal efficacy. This emphasizes the inherent reliability and robustness of the developed photocatalysts.

A joint experimental and theoretical investigation of the binding mechanism between zein and folic acid in an ethanol–water solution

ABSTRACT The aim of the present study was to determine the binding mechanisms between zein and folic acid in an ethanol – water solution. Fluorescence spectroscopy demonstrated that folic acid quenched the fluorescence intensity of zein by both dynamic and static fluorescence quenching mechanisms, with static quenching playing a prominent role. The binding constants (Ka) of the zein-folic acid complex at 292, 302, and 312 K were evaluated to be 5.97 × 105, 3.00 × 105 and 1.54 × 105 L/mol, respectively. The process of folic acid binding zein was driven by ∆H0 = –51.24 kJ/mol, ∆S0 = –64.90 J/mol•K. Van der Waals forces and hydrogen bonding primarily governed the formation of the zein-folic acid complex. Confirmation of the complex formation was obtained via UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy, which also revealed alterations in the secondary structure of zein upon binding to folic acid. Measurements of particle size and zeta potential demonstrated an enhancement in the stability of the complex system. Scanning electron microscopy and transmission electron microscopy showed the complex to possess a spherical morphology, with significant changes in the zein’s morphology following its binding to folic acid. Additionally, zein increased the photostability of folic acid against UV light radiation. Molecular docking and molecular dynamics simulations were used to investigate the binding mechanisms involved further, and the results effectively elucidated the observed experimental phenomena. This research establishes a significant theoretical foundation for the utilization of zein as a system for delivering and safeguarding folic acid.

Photocatalytic performance of ZnO and ZnO/Zn3(PO4)2 coatings formed by plasma electrolytic oxidation of zinc

In this study, plasma electrolytic oxidation (PEO) of zinc in a water solution containing 10 g/L Na3PO4⋅12H2O + 2 g/L KOH, was used for the preparation oxide of coatings for application in photocatalysis for degradation of organic dyes. Degradation of methyl orange (MO) as a model of organic dyes under simulated sunlight was used. In coating formed after 2 min of PEO, the pure phase hexagonal wurtzite ZnO was identified, while in coatings formed for a long time of PEO (up to 5 min) monoclinic phase of Zn3(PO4)2 was identified together with ZnO (ZnO/Zn3(PO4)2 coatings). ZnO/Zn3(PO4)2coatings show better photocatalytic activity (PA) than ZnO coating. The ZnO/Zn3(PO4)2 coating with the highest PA was formed after 4 min. Coupling ZnO with Zn3(PO4)2 reduce the recombination rate of photo-generated electron/hole pairs in ZnO which leads to an increase in PA of ZnO/Zn3(PO4) coatings compared to pure ZnO coating. This is confirmed by photoluminescent measurements. According to photocatalytic and photoluminescence measurement mechanism of the light-induced degradation of MO over ZnO/Zn3(PO4)2 coatings is suggested.

The role of sulfate in the hydrothermal replacement of aragonite single crystals by calcite

Aragonite (CaCO3) is a stable calcium carbonate phase under high pressure conditions. However, its formation in (sub)surface environments, where calcite is the stable polymorph, is widespread. Regardless of its origin, aragonite is expected to undergo transformation into calcite under moderate pressures and temperatures. However, this transformation does not always take place, which results in the presence of abundant aragonitic relics in the geological record. Traditionally, this preservation has been explained by the presence of chemical inhibitors that prevent the conversion of aragonite to calcite. While it is widely accepted that magnesium (Mg) plays a key role in the polymorphic selection of CaCO3, the influence of other ions has also been suggested. This work evaluates the effect that different concentrations of sulfate (SO42−) in the fluid has on the progress of the aragonite-to-calcite transformation at 220 °C. Our results show that, upon reaction with deionized water or sulfate-poor solutions ([SO42−]aq < 0.1 mM), aragonite single crystals are extensively replaced by calcite aggregates (crystal size > 15 µm) through an interface coupled dissolution-precipitation reaction. The replacement starts at the aragonite crystal surfaces and advances inwards thanks to the development of an extensive network of fractures. Contrarily, when the solution bears higher concentrations of sulfate ([SO42−]aq > 0.1 mM), only a thin layer of smaller crystals of calcite (< 10 µm) form on the aragonite substrates, without any further transformation taking place. We interpret that these smaller crystals exert too little crystallization pressure and fail to promote the development of a network of fractures. In the absence of this network, the aragonite-calcite transformation cannot take place. The transformation does not occur neither when the experiments are conducted with deionized water and fragments of gypsum or anhydrite together with the aragonite grains. The results of this study shed light on the influence of dissolved sulfate in the kinetics of the fluid-driven transformation of aragonite into calcite. These results are useful to understand the preservation of aragonite in a variety of current geological settings and provide valuable insights for better understanding the diagenesis of sedimentary carbonates.

Novel Biomaterial-Derived Activated Carbon from Lippia Adoensis (Var. Koseret) Leaf for Efficient Organic Pollutant Dye Removal from Water Solution

Today, various pollutants, such as dyes from industries, are being released into the environment worldwide, posing significant challenges that require sustainable attention and advanced solutions. This research focuses on the synthesis and characterization of a novel biomaterial-based activated carbon (AC) derived from Lippia Adoensis (Koseret) leaves and investigates its effectiveness in removing MB from aqueous solutions. The biomaterial adsorbent derived from LA was subjected to proximate analysis, pH-point zero charge (pHpzc), FT-IR, and SEM characterization. The pHpzc results indicated a slightly acidic surface functional group for AC. The impact of temperature and chemical impregnation (H&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;PO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;, NaCl and NaOH) was examined, with the optimal temperature of AC preparation found to be 600°C. The use of H&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;PO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; for the chemical activation of biomaterials resulted in a high AC surface area. Batch adsorption experiments involved varying pH (2–10), dosage (0.1–0.35 g/50ml), initial concentration (10–35 ppm) and contact time (15–105 min). The optimal parameters were determined as pH = 8, dose = 0.25g, concentration = 10 ppm, and contact time = 75 min. The maximum adsorption capacity and removal efficiency were calculated as 3.99 and 92.2%, respectively. Thermodynamic analysis confirmed the spontaneous and endothermic nature of the system. Adsorption isotherm and kinetic studies revealed a good fit with the Langmuir isotherm (R&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;= 0.999), indicating monolayer adsorption and the pseudo-second order model, respectively. These findings suggest that the use of LA-AC could offer a cost-effective solution for the removal of methylene blue from water, contributing to the solution of water pollution challenges and promoting the adoption of eco-friendly wastewater treatment technologies.

Electrochemical study of the reactivity of furfural and 5-hydroxymethylfurfural with aliphatic primary (di)amines

Furfural (FF) and 5-hydroxymethylfurfural (HMF) are important and prospective renewable sources for chemical, fuel, material or pharmaceutical industry, the furfurylamines being the desired precursors. In this contribution new effects related to the reactivity of FF and HMF with various aliphatic primary (di)amines were observed using an electrochemical approach in water solutions. Following an initial investigation of electroreduction, the course of condensation reactions in basic buffers under various stoichiometric conditions was electrochemically monitored. Using five aliphatic amines and two (α,β- and α,ω-) diamines, a variety of products (mainly Schiff-bases) was identified. As a pilot study for “one-pot” reductive amination, the mixture of FF and n-PrNH2 was electrochemically reduced in basic buffers. The vicinal diamine (analogue of a pinacol) was the main product, together with the expected furfurylamine.