Solution pH Conditions Research Articles

Turning properties of Ni/Al2O3 catalyst to improve catalytic ammonia decomposition for green hydrogen production: pH does matter!

In this study, the influence of solution pH (6.0–12.5) of the cation–anion double hydrolysis (CADH) method in the formation of Ni/Al2O3 catalyst and its catalytic performance for green hydrogen production NH3 decomposition was studied for the first time. The physicochemical properties of the prepared catalysts were systematically characterized by various analysis techniques. The results indicated that pH conditions significantly influenced both the structural properties and catalytic activity of the derived Ni/Al2O3 catalysts. The better catalytic activity for NH3 decomposition over catalysts prepared under high pH conditions (pH ≥ 10.0) is mainly due to the appropriate synergic effect of the interaction between Ni and Al2O3 support, large active Ni surface area, and suitable porosity, particle size, and basicity of the catalyst. The correlation analysis and density functional theory (DFT) calculations confirm that the percentage of surface metallic Ni plays a crucial role in controlling the catalytic activity of Ni/Al2O3 catalysts. The 40Ni/Al2O3 catalyst (Ni = 40 wt%) could achieve over 94.5 % NH3 conversion under the harsh reaction conditions of 600 °C and NH3 WHSV of 54000 mL/gcat./h, and that stably maintained for 200 h without any obvious deactivation. Overall, our work not only highlights the critical role of pH conditions in the CADH solution for cost-effective Ni/Al2O3 catalyst preparation but also proposes a promising strategy for developing a highly active, stable, and Ru-free catalyst for practical hydrogen production via NH3 decomposition.

Optimizing chromium removal from synthetic wastewater via electrocoagulation process with a natural coagulant (blended of eggshell powder and lime) using response surface methodology

The presence of chromium (Cr) in synthetic wastewater has become a serious environmental issue. Therefore, main aim of this work was to investigate Cr removal from synthetic wastewater via electrocoagulation (EC) with a natural coagulant using aluminum electrodes. The central composite design (CCD) of the response surface methodology (RSM) method was used to optimized the operating variables of solution pH (5-9), initial Cr concentration (225-475 mgL-1), reaction time (30-40 min), and applied current (0.35-0.55 A). The ANOVA results clearly shows that the quadratic model (p < 0.0001) was sufficient to the best predicting of the removal performance of Cr (R2 = 0.9994 for electrode distance of 0.5 cm and 0.9924 for 1 cm). The maximum removal (99.836% for electrode distance of 0.5 cm, and 98.175% for 1 cm) of Cr was achieved with optimized conditions of solution pH 7.053, initial Cr concentration 337.795 mgL-1, reaction time 37.148 min, and applied current of 0.505 A. From this finding, it was proved that the EC process assisted with natural coagulant is an efficient, and cost-effective method for the removal of Cr from synthetic wastewater.

Efficient removal of Cr(VI) containing tunnel wastewater by sludge biochar loaded with ferrous sulfate

The ease of agglomeration reduced the removal of pollutants by FeS particles. Hence, sludge biochar was employed as a support to produce FeS-loaded biochar composites (FeS@BC) using a solvothermal method, for removing Cr(VI) from wastewater. The performance and mechanism of Cr(VI) removal on FeS@BC were investigated through adsorption experiments and characterization techniques. The adsorption tests revealed that under optimal conditions of solution pH of 3 and dosage of 40 mg, FeS@BC achieved a removal efficiency of over 97 % for 50 mg/L Cr(VI). The presence of Cl- and NO-3 did not affect Cr(VI) removal, whereas sulfate, phosphate, and carbonate inhibited the removal process. Low concentrations of humic acid (1–5 mg/L) held a negligible influence on removing, but elevated concentrations of humic acid inhibited Cr(VI) removal. The behavior of FeS@BC in removing Cr(VI) complied with to the pseudo-second-order and the Langmuir model. At 308.15 K, the largest removal capability of FeS@BC for Cr(VI) reached 185.874 mg/g. Thermodynamic studies confirmed that the Cr(VI) removing processes on FeS@BC were a spontaneous, entropy-driven, endothermic chemical adsorption. The primary mechanism for removing Cr(VI) on FeS@BC included reduction, electrostatic adsorption, complexation, and precipitation, with the reduction process playing a crucial role. This indicated that sludge biochar loaded with FeS was an ideal material for removing Cr(VI) from wastewater.

Magnetic hybrid spheres of glauconite/calcium alginate interface for methylene blue adsorption: Synthesis, characterization, and novel physicochemical insights through theoretical treatment

Fe3O4 nanoparticles were embedded within a glauconite‑calcium alginate (G/CA) matrix to create magnetic hybrid spheres (MNPs-G/CA), with the aim of purifying water from methylene blue (MB) at temperatures of 25, 40, and 50 °C. MNPs-G/CA adsorbent was characterized using numerous techniques, including elemental mapping, zeta potential, FTIR, FESEM, XRD, EDX, and TEM. The greatest amount of the removed MB was achieved under definite conditions of solution pH 8.0, MNPs-G/CA mass (25 mg), interaction time (2 h), and 200 mg/L of MB concentration. The MB uptake process kinetic followed a pseudo-second-order equation (R2 > 0.99) at all tested temperatures. The equilibrium data were fitted to a statistical physics multilayer model in conjunction with the Langmuir and Freundlich equations. The steric n parameter reveals that MNPs-G/CA adsorbent possesses a mixed adsorption orientation (i.e., ranging from 0.69 to 0.93) across various temperatures. The amount of MNPs-G/CA active positions (the NM parameter) was progressively increased from 245 mg/g to 419 mg/g. The measured adsorption capacities (Qsat) ranged from 466.49 to 664.37 mg/g, and the removal of MB molecules was consistent with an endothermic interaction. The interface between the MNPs-G/CA-MB was principally dictated by electrostatic attractions, as evidenced by the values of adsorption energies (∆E), which varied from 16.75 to 21.52 kJ/mol. The regenerated MNPs-G/CA offered over 80 % of its adsorption strength after the fourth adsorption–desorption cycle. This study contributes to our understanding of the physicochemical parameters controlling the MB adsorption mechanism on multifunctional hybrid adsorbents, like the interface between glauconite, alginate, and MNPs.

Polypyrrole-encapsulated metal oxide nanocomposite for adsorptive abatement of anionic dye from dye laden wastewater: Cost analysis and scale up design

The present work demonstrates the fabrication of an organometallic material i.e. polypyrrole-encapsulated zinc oxide (PPy@ZnO) nanocomposite for adsorptive elimination of Eriochrome black-T (EBT) dye from water. The specific surface area and pore volume of the PPy@ZnO nanocomposite were observed to be 28.726 m2/g and 0.086 cc/g, respectively. At optimum experimental conditions of solution pH; 4.0, PPy@ZnO nanocomposite dose: 1.0 g/L, contact time: 30 min and initial EBT dye concentration: 50 mg/L, maximum EBT dye removal efficiency of ∼94±1.86% was obtained. The pseudo-second-order kinetic and Langmuir isotherm model provides the best fit for the adsorption experiments, with maximum EBT dye adsorption capacity of 277.78 mg/g. The prominent adsorption mechanisms include the hydrogen bonding, π–π interactions, and electrostatic attraction. The adsorption study is spontaneous (ΔG° < 0) and endothermic (ΔH° > 0, ΔS° > 0) in nature as indicated by the thermodynamics study. The reduction in EBT dye removal efficiency was insignificant (∼10±0.94%) in surface water as compared to other real water samples. Monovalent anions (i.e., NO3–and Cl–) have minimal impact on EBT removal efficiency with reduction in removal efficiencies in the range of 4.0±1.54% to ∼11.0±1.93%. Regeneration study suggests an overall ∼20±1.45% decrease in the EBT dye removal efficiency after 5th cycle of regeneration. Response surface methodology suggests the maximum adsorption efficacy of 95±1.68% at initial EBT dye concentration of 35 mg/L, PPy@ZnO dose of 0.85 g/L and contact time of 40 min. The estimated synthesis cost of PPy@ZnO nanocomposite was determined to be ∼117 USD/kg. Batch mode scale-up design suggests a minimum of 87.48 g of PPy@ZnO nanocomposite needs to be applied to treat 50 mg/L of EBT dye loaded wastewater (50 L volume) with 95% dye removal efficiency.

Effective oxidation decomplexation of Cu-EDTA and Cu2+ electrodeposition from PCB manufacturing wastewater by persulfate-based electrochemical oxidation: Performance and mechanisms.

Complex wastewater matrices such as printed circuit board (PCB) manufacturing wastewater present a major environmental concern. In this work, simultaneous decomplexation of metal complex Cu-EDTA and reduction/electrodeposition of Cu2+ was conducted in a persulfate-based electrochemical oxidation system. Oxidizing/reductive species were simultaneously produced in this system, which realized 99.8% of Cu-EDTA decomplexation, 94.5% of Cu2+ reduction/electrodeposition under the conditions of original solution pH = 3.2, electrode distance = 3cm, [Na2S2O8]0 = 5mM, current density = 12mA/cm2, and reaction time = 180min. The total treatment cost is as low as 0.80 USD/mol Cu-EDTA. Effective mineralization (74.1% total organic carbon removal) of the solution was obtained after 3h of treatment. •OH and SO4•- drove the Cu-EDTA decomplexation, destroying the chelating sites and finally it was effectively mineralized to CO2, H2O and Cu2+. The mechanisms of copper electrodeposition on the stainless steel cathode and persulfate activation by the BDD anode were proposed based on the electrochemical measurements. The electrodes exhibited excellent reusability and low metal (total iron and Ni2+) leaching during 20 cycles of application. This study provide an effective and sustainable method for the application of the electro-persulfate process in treating complex wastewater matrices.

KOH-activated biochar and chitosan composites for efficient adsorption of industrial dye pollutants

The treatment of dye pollutants remains a challenge in the current management of the water environment. In this study, an innovative biochar material co-modified with KOH and chitosan was synthesized. The morphology and physicochemical properties of the modified biochar material were assessed by SEM, FTIR, XPS, XRD, and thermogravimetric analyses. The results revealed a significant enhancement in chitosan loading due to the pretreatment of biochar with KOH. The co-modified biochar with KOH and chitosan (CHKBC) exhibited an enriched composition of functional groups such as − COOH, −NH2, and − OH, leading to a substantial increase in the maximum adsorption of MB by the biochar from 8.83 mg g−1 to 62.04 mg g−1, a 7.03-fold increase. The excellent adsorption performance of CHKBC for MB was maintained at different solution temperature (288–––318 K) and pH (5–––11) conditions. The main adsorption mechanisms of MB removal by CHKBC involved ion exchange, pore filling, electrostatic attraction, π - π interactions, and hydrogen bonding. Overall, CHKBC has higher chitosan loading, more uniform chitosan distribution, and better adsorption efficiency of MB. It is a promising adsorption material with low cost and a simple production process.

Cation exchange to montmorillonite induces selective adsorption of amino acids

Concentrating simple organic molecules, such as amino acids, in the adsorbed phase could have been an early step in prebiotic evolution towards more complex bio-macromolecules on the early Earth. Smectite clay minerals represent potential selective sorbents for prebiotic molecules because of their negative structural charge and high surface area. This study evaluated the adsorption behavior of amino acids to montmorillonite, a well-characterized smectite, at varying pH and fluid compositions. At both pH 5 and 7 in a sodium chloride fluid, amino acids with basic sidechains (L-arginine and L-lysine), which are primarily cationic under these conditions, were selectively adsorbed to montmorillonite with Langmuir constants much greater than amino acids that were predominantly zwitterionic or anionic in solution. On average, the Langmuir constants for the cationic amino acids were 30 (pH 5) and 50 (pH 7) times greater than the constants for zwitterionic amino acids and 120 (pH 5) and 80 (pH 7) times greater than the constants for L-glutamic acid. Under the same pH conditions in a magnesium chloride solution, the adsorption of L-arginine and L-lysine was substantially inhibited with Langmuir constants ∼ 10 times smaller. These observations suggest that cation exchange is the dominant adsorption mechanism for amino acids on montmorillonite. X-ray diffraction and infrared spectroscopy indicate that L-arginine and L-lysine enter the smectite interlayer where the protonated amino sidechain has the strongest interactions with the mineral surface, further supporting adsorption driven primarily through electrostatic interactions. Therefore, smectites on the early Earth may have selectively concentrated cationic amino acids, providing a potential template for the polymerization of α-amine linked peptides.

Removal of Chromium (VI) from Water Using Orange peel as the Biosorbent: Experimental, Modeling, and Kinetic Studies on Adsorption Isotherms and Chemical Structure

The present work aims to assess the effectiveness and efficiency of orange peels as a low-cost biosorbent for removing Cr(VI) from an aqueous solution by the biosorbent process. The orange peels as adsorbent was characterized using different methods, such as FTIR, pHpzc, equilibrium pH, TGA, XRD, SEM, and (BET). The tests were conducted in the batch mode, and the effects of different parameters, such as the pH, dosage of the bioadsorbent, influent Cr(VI), and time, on the biosorption of Cr(VI) were investigated. The adsorption kinetics proved that a contact time of 90 min resulted in the highest (approximately 97.8%) Cr(VI) removal, with an adsorption capacity of 4.96 mg/g. Moreover, the increase in the biosorbent dosage (from 1 to 10 g/L) resulted in the enhancement in the Cr(VI) removal effectiveness. Moreover, the pH of the solution also affected significantly the effectiveness of the removal. The tests were conducted under acidic pH solution conditions, and the prediction of the pH value at a zero charge (pH pzc) was confirmed experimentally. Furthermore, the results from the batch-mode assays were successfully tested by an experimental design (full factorial design). The biosorption of Cr(VI) on orange peels occurred mostly according to the pseudo-second-order kinetic model and the uptake of Cr(VI) was satisfactorily described by the Langmuir model.

A novel monolithic Zn/Cr-LDH composite for in-tube solid-phase microextraction of acidic herbicides from water samples

A monolithic composite based on Zn/Cr-layer double hydroxide (Zn/Cr-LDH) was introduced for in-tube solid-phase microextraction (IT-SPME) of chlorophenoxy acetic acid (CPAs) herbicides. A polymeric monolith composed of methacrylic acid (MAA) and Zn/Cr-LDH was simply prepared in a polypropylene tube by in situ polymerization method. 2,4-Dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) were identified and measured using gas chromatography coupled to mass spectrometry (GC-MS). The fabricated composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FT-IR). The extraction efficiency was enhanced by optimizing crucial factors, such as salt concentration, sample solution pH, extraction, and desorption conditions. Under the optimum conditions, low detection limits (LODs) were obtained in the range of 0.01–0.05 ng mL−1 with good linearity in the range of 0.1–500 ng mL−1 and coefficient of determinations (R2) better than 0.9975. The inter and intra-assay precisions (RSD%, for n = 3) were achieved in the range of 7.1–8.2% and 6.8–7.9%, respectively. The monolithic composite displayed satisfying extraction performance and effective clean-up of CPAs from water samples.

Efficient separation and recovery of Co and Ni from ammonium sulfate roasting‐water leaching solutions of oceanic cobalt‐rich crusts by sulfide precipitation and P507–Cyanex 272 synergistic extraction

AbstractOceanic cobalt‐rich crusts contain many valuable metals including Co, Ni, Cu, and Mn, of which Co and Ni are scarce metal resources on terrestrial land. Co, Ni, Cu, and Mn in cobalt‐rich crusts can be efficiently extracted by the ammonium sulfate roasting‐water leaching (ARWL) process, but separating and recovering Co and Ni from the leaching solution containing high concentrations of Mn is a challenging problem. In this study, a combination of sulfide precipitation and P507–Cyanex 272 synergistic extraction is proposed for the separation and recovery of Co and Ni from the ARWL solutions of oceanic cobalt‐rich crusts. Under the optimum sulfide precipitation conditions, Co and Ni were precipitated with 99.85% and 99.63% efficiency, respectively, while Mn was coprecipitated with only .79% efficiency. The Co–Ni mixed sulfides were dissolved by dilute sulfuric acid under oxidative conditions to obtain a solution containing 12.584 g/L Co, 11.012 g/L Ni, and a small amount of Mn. Subsequently, Co and Mn were extracted from this solution using P507–Cyanex 272 synergistic extraction, the single‐stage extraction efficiencies of Co and Mn were 95.76% and 99.73%, respectively, and the coextraction efficiency of Ni was 3.02%, under the conditions of a feed solution pH of 3.0, an extractant saponification degree of 70%, a total extractant concentration of 20% (P507 to Cyanex 272 ratio of 3:7), and an O/A ratio of 1.1:1. The results of the thermodynamic study showed that the reaction of Co extraction by this mixed extraction system was exothermic. Ni in the organic phase was washed with an H2SO4 concentration of .12 mol/L, followed by stripping of Co and Mn with an H2SO4 concentration of .6 mol/L. Mn in the stripping solution was removed by oxidative precipitation with (NH4)2S2O8, after which the Co3O4 product was obtained by precipitation with (NH4)2C2O4 and calcination. Similarly, NiC2O4·2H2O can be obtained from the raffinate by (NH4)2C2O4 precipitation. Finally, a flowsheet was developed for the separation and recovery of Co, Ni, Cu, and Mn from the ARWL solutions of oceanic cobalt‐rich crusts. The study provides a promising scheme for the recovery of various valuable metals from deep‐sea cobalt‐rich crusts or manganese nodules.

Effects of solution pH and preparation conditions on the electrochemical behaviors of Pt(111)-Nafion interface

The Nafion ionomer is one of the important components in the membrane electrode assemblies of proton exchange membrane fuel cells, and acts as both the proton conductor and the binder for nanocatalysts and carbon supports. To gain a better understanding of the structure-performance relationship for the membrane electrode assemblies, Pt(111)-Nafion model interfaces are fabricated, and factors affecting their electrochemical behaviors, especially the adsorption and poisoning behavior of sulfonic acid groups, have been systematically investigated using electrochemical cyclic voltammetry. Experiments show that the adsorption amount and potential of sulfonic acid groups at the interface can be influenced by solution pH and processing conditions (heat treatment, solvent type, and membrane thickness). It can be inferred that the adsorption process of sulfonate groups involves the participation of protons, and thus the number of protons, sulfonate groups and water molecules at the interface will affect the adsorption process. Additionally, our results indicate that heat treatment can regulate the poisoning effect of sulfonic acid groups at the interface, thus improving ORR activity. These findings have important implications for optimizing the preparation conditions of catalyst layers in fuel cells, improving fuel cell performance, and enhancing our understanding of the electrode-Nafion interface.

Simple and efficient removal of azo dyes from water samples by dispersive solid-phase micro-extraction employing graphene oxide with high oxygen content

ABSTRACT A technique based on dispersive solid-phase micro-extraction (DSPµE), employing graphene oxide (GO) particle with a higher oxygen content synthesised by through a modification of the Hummers method was investigated. GO particle was characterised using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Dubinin-Radushkevich, and Freundlich models. DSPµE parameters such pH effect, adsorbent amount, and contact time were optimised in the dye removal process. The proposed method was applied for the removal of three azo dyes in tap water samples: sunset yellow (SY), allure red (AR), and tartrazine (TAR). The water samples were previously analysed using large volume sample stacking capillary electrophoresis (LVSS-CE). Maximum removal capacity was achieved under the optimal conditions of pH solution (pH = 6.0), GO amount (10.0 mg), and contact time (10 minutes) with percentages at 99.0%. The precision was measured in terms of recovery (% desorption) and relative standard deviation from 95.5 to 98.0%, RSD (<10.0%). Two positive water samples for SY and TAR were completely free of azo dyes after application of the proposed method, whereas AR was not detected in any of the ten samples.

Effective separation of V(IV) and Fe(III) from sulfuric acid solution by solvent extraction with P507 and N235

A selective and highly effective method is proposed for the extraction and separation of V(IV) and Fe(III) using the trioctyl tertiary amine (N235) and 2-ethylhexyl hydrogen-2-ethylhexylphosphonate (P507). Various solvent extractants for extracting and separating V(IV) and Fe(III) have been studied; P507 and N235 appear to be the most active solvent extractants offering high extraction efficiency and separation factor. The effect of pH, composition and concentration of extractant mixture on the extraction efficiency and separation factor was investigated using the general conditions of 1:1 (v/v) organic to aqueous ratio and 0.2 g/L and 0.5 g/L of V(IV) and Fe(III), respectively. Results showed that the maximum separation factor was 31, and the extraction efficiencies of Fe(III) and V(IV) were 89.4% and 15.3%, respectively, under the conditions of initial solution pH of 1.2, VP507:VN235 of 1:2 and total extractant concentration of 30% (v/v). The hydrogen bond (N-H+···O=P) between P507 and N235 was generated upon mixing, which produced the P507 monomer as indicated by the slope analysis, software simulation, and Fourier transform infrared (FT-IR) spectral analysis. The monomer of P507 can heighten the extraction efficiency, as well as effectively weaken the stability of vanadium containing extraction complex. In addition, the extraction complexes [2(R3NH···OP(O)R2)VO]2+ and [3(R3NH···OP(O)R2)Fe]3+ were formed by a cation exchange process. The mixed extraction system extracted and separated V(IV) and Fe(III) more effectively than that by pure P507 or N235.

Ultra-trace analysis of chromium ions (Cr3+/Cr6+) in water sample using selective fluorescence turn-off sensor with natural carbon dots mixed graphene quantum dots nanohybrid composite synthesis by pyrolysis

This study was aimed to implement the one-pot pyrolysis for hybrid nanomaterial synthesis consisting of graphene quantum dots (GQDs) from solid citric acid and carbon dots (CDs) which was hydrothermally derived from the herbal plant extract of “Houttuynia cordata”, denoted as Carbon Dots mixed Graphene Quantum Dots (CDs@GQDs). The nanohybrid were structurally characterized by XPS, FT-IR, Fluorescence, and UV–Visible absorption spectroscopy, and their morphological images were also analyzed by HR-TEM and FE-SEM/EDX. The quantum yield was found to be 15 %, higher than that of intact CDs or GQDs. Upon excitation at a maximum wavelength of 355 nm, and emission in the 450 nm. In this case, it was observed that the nanohybrid exhibit a high degree of selectivity towards Cr6+ ion when employed as a fluorescence quenching sensor from screening test with different metal ions. Therefore, the optimization conditions of solution pH, concentration of nanohybrid, H2O2 concentration as an oxidizing agent, reaction duration time with the aid of ultrasonication were carried out in details and the permissible limit of Cr3+ presence in the target analyte was all undertaken in order to enhance the detection of Cr6+ species. Its linear calibration curve was such y = 0.37x + 55.7, with a coefficient of determination (r2) value of 0.9816. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 17.2 nM, and 52.2 nM. Consequently, the nanohybrid as a green chelating agent in the selective assessment of ultra-trace amount of Cr6+ in spiked water sample model was also done with good recoveries in both bottled drinking water and tap water samples ranging from 102.86 to 114.23 %.

Montmorillonite modified Ni/Mg/Al ternary layered double hydroxide nanoflowers with enhanced adsorption features

A hydrothermal technique was employed to synthesize Ni/Mg/Al ternary L.D.H.s modified with montmorillonite (NMA-MMT-LDHs). Many characterization methods, including X-ray diffraction (XRD), scanning electron microscopy (S.E.M.), Fourier transform infrared (FTIR), and Brunauer, Emmett, and Teller (B.E.T.), were used to assess the physiochemical properties of the produced analytes. Congo red and methylene blue were utilized as model dyes to treat textile waste with the synthesized analytes. The batch adsorption model was utilized to conduct the adsorption experiments under varying contact time, adsorbent dosage, and solution pH conditions. A pseudo-second-order kinetics and the Langmuir adsorption model control the adsorption process. The maximum monolayer adsorption capacities of C.R. and M.B. were determined to be 344 and 200 mg/g, respectively. As the quantity of dosage increased from the 0.01–0.04 g, the percent removal efficiency (%) increased from 75 to 87 % for S2-LDH, 84–88 % for S2-MMT, 86–93 % for S3-MMT, and 95–97% for S4-MMT for C.R. dye and 82–85 % for S2-LDH, 83–89 % for S2-MMT, 83–91 % for S3-MMT, and 84–92 % for S4-MMT for M.B. dye. The removal percentage of C.R. dye for adsorbents S2-LDH, S2-MMT, S3-MMT, and S4-MMT were 75 %, 84 %, 86 %, and 95 %, respectively and 82 %, 83 %, 83 %, and 85 %, respectively for the M.B. dye removal. The presence of MMT significantly increases the affinity of Ni/Mg/Al-LDHs (NMA-LDHs), and the designed production technique can be used to produce a variety of compositionally distinct adsorbent materials.

Dual-Responsive Supramolecular Chiral Assemblies from Amphiphilic Dendronized Tetraphenylethylenes.

Supramolecular assembly of amphiphilic molecules in aqueous solutions to form stimuli-responsive entities is attractive for developing intelligent supramolecular materials for bioapplications. Here we report on the supramolecular chiral assembly of amphiphilic dendronized tetraphenylethylenes (TPEs) in aqueous solutions. Hydrophobic TPE moieties were connected to the hydrophilic three-fold dendritic oligoethylene glycols (OEGs) through a tripeptide proline-hydroxyproline-glycol (POG) to afford the characteristic topological structural effects of dendritic OEGs and the peptide linker. Both ethoxyl- and methoxyl-terminated dendritic OEGs were used to modulate the overall hydrophilicity of the dendronized TPEs. Their supramolecular aggregates exhibited thermoresponsive behavior that originated from the dehydration and collapse of the dendritic OEGs, and their cloud point temperatures (Tcps) were tailored by solution pH conditions. Furthermore, aggregation-induced fluorescent emission (AIE) from TPE moieties was used as an indicator to follow the assembly, which was reversibly tuned by temperature variation at different pH conditions. Supramolecular assemblies from these dendronized amphiphiles exhibited enhanced supramolecular chirality, which was dominated mainly by the interaction balance between TPE with dendritic OEG and TPE with POG moieties and was modulated through different solvation by changing solution temperature or pH conditions. More interestingly, ethoxyl-terminated dendritic OEG provided a much stronger shielding effect than its methoxyl-terminated counterpart to prevent amino groups within the peptide from protonation, even in strong acidic conditions, resulting in different responsive behavior to the solution temperature and pH conditions for these supramolecular aggregates.

Electrokinetic ion rectification coupled with surface charge and thermal dependence in the conical nanochannel

With the further development of nanotechnology, electrokinetic ion rectification (ICR) is receiving increasing attention. Since the chemical equilibrium boundary is more suitable for expressing the wall charging characteristics and the coincidence of asymmetric temperature with ICR, we first propose an ICR ion transport model that couples the chemical equilibrium boundary with asymmetric temperature. In this work, ICR under different electrical boundary conditions is studied. The effects of membrane thermal conductivity, solution pH, and geometric conditions on the rectification performance are further explored in combination with surface charge and temperature dependence. The results show that the rectification ratio of the constant σ model and constant ζ model has a significant deviation compared to the multi-ion model, and the electrical boundary conditions can be simplified by changing the external conditions. By controlling the thermal conductivity of the membrane, the distribution of temperature difference within the reservoir or nanochannel can be determined, which affects the enrichment or depletion of ions in the nanochannel and ultimately achieves the goal of optimizing the rectification ratio. The optimal ICR ratio can be obtained by adjusting pH, and optimizing geometric conditions can significantly improve rectification performance. These studies provide helpful information for ion transport control and optimization of micro/nanofluid devices.

Construction of molecular enrichment accelerators via assembly of enzyme surface grafted polymer and cyclodextrin achieving rapid and stable ester catalysis for biodiesel synthesis

Efficient and stable catalysis has always been the core concept of enzyme catalysis in industrial processes for manufacturing. Here, we constructed molecular enrichment accelerators to synergistically enhance enzyme activity and stability by assembling enzyme surface grafted polymer and cyclodextrin. At 40 °C, the enzyme activity of CalB-PNIPAM212/β-CD was 2.9 times that of CalB-PNIPAM212. The enzyme activity of CalB-PNIPAM428/γ-CD had reached 1.61 times that of CalB. At the same time, the stability of CalB-PNIPAM212/β-CD and CalB-PNIPAM428/γ-CD are slightly better than that of CalB under high temperature, organic solution and extreme pH conditions. The synergistic increase in activity and stability of the lipase-polymer assembly was achieved due to the structure of assembly, in which the role of cyclodextrin could enrich substrate affecting molecular diffusion. In addition, the lipase-polymer assembly proved to be an efficient catalyst for biodiesel synthesis, with a biodiesel conversion 1.4 times that of CalB at 60 °C. Therefore, this simple and low-cost lipase-polymer assembly provides new possibilities for the construction of high-efficiency industrial biocatalytic catalysts.

Constructing Z-scheme Nd:Bi2WO6/CdS nanostructures for efficient degradation of organic pollutants: Structural, optical and photocatalytic properties, and mechanistic insights

Bismuth tungstate-based semiconductor materials exhibit unique environmental purification and energy conversion capabilities, becoming a hotspot to address the environmental pollution and energy shortage. However, the high recombination rate of carriers and dissatisfactory photocatalytic degradation efficiency limit their practical application. Here, different pH conditions of precursor solution were used to synthesize Nd:Bi2WO6 nanostructures with in situ CdS epitaxial layer (NBWO/CS) and their structure, optical properties and photocatalytic performance were studied in detail. Under the optimized pH = 6, the resulting NBWO/CS exhibits the best performance at 58.7% for RhB within 2 h, which is ascribed to the excellent separation of photogenerated electron-hole pairs. In addition, the mechanisms of photocatalytic degradation for organic contaminants as well as generation and separation of carriers were further exposed. This work provides theoretical foundations and technical support for the development of high-performance photocatalytic materials to decontaminate the environment and convert energy.