Cations In Solution Research Articles

Chemistry in the Molten State: Opportunities for Designing and Tuning the Emission Properties of Halide Perovskites.

A series of monolayered lead halide hybrid perovskites (HO2C(CH2)n-1NH3)2PbX4, named (Cn)2PbX4 (n = 4-6, X = Cl, Br), exhibiting a low congruent melting temperature (Tm) (Tm = 130 °C for (C4)2PbBr4), high stability in the molten state, and whitish type emission, are reported. From the synthesis in the molten state, rare solid solutions of mixed organic cations (Cn1-xCn'x)2PbX4 (n, n' = 4-6; X = Cl, Br; 0 ≤ x ≤1) as well as solid solutions of mixed halides (Cn)2Pb(X1-yX'y)4 (n = 4-6; X, X' = Cl, Br; 0 ≤ y ≤1) have been prepared and characterized (thermal behavior, powder X-ray diffraction (PXRD), photoluminescence properties). The impact of substitutions is significant on the thermal properties, lowering the Tm down to 100 °C for (C4)2Pb(Br0.25Cl0.75)4. The emission properties are slightly tuned in the case of mixed organic cation systems, whereas modifications are more dramatic in the case of mixed halide systems, leading to emission properties through the entire visible region. These results illustrate the great opportunities offered by the congruent melting properties of halide perovskites allowing syntheses in the molten state.

Zircon-Type CaCrO4 Chromite Nanoparticles: Synthesis, Characterization, and Photocatalytic Application for Sunlight-Induced Degradation of Rhodamine B.

The degradation of organic dye pollutants is a critical environmental issue that has garnered significant attention in recent years. To address this problem, we investigated the potential of CaCrO4 chromite (CCO) as a photocatalyst for the degradation of cationic and anionic dye solutions under sunlight irradiation. CaCrO4 was synthesized via a sol-gel auto-combustion route and sintered at 900 °C. The Rietveld refined XRD profile confirmed the zircon-type structure of CaCrO4 crystallized in the tetragonal unit cell with I41/amd space group symmetry. The surface morphology of the sample was investigated by field emission scanning electron microscopy (FESEM), which revealed the polyhedral texture of the grains. Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) studies were carried out to analyze the elemental composition and chemical states of the ions present in the compound. Fourier transform infrared (FT-IR) spectroscopy analysis revealed the vibrational modes corresponding to the tetrahedral and dodecahedral metal oxide bonds. The optical band gap was approximated to be in the range of 1.928 eV by using the Tauc relation. The CaCrO4 catalyst with different contents (5, 20, 35, and 50 mg) was investigated for its photocatalytic performance for the degradation of RhB dye solution under sunlight irradiation using a UV-Vis spectrometer over the experimental wavelength range of 450-600 nm. The degradation efficacy increased from 70.630 to 93.550% for 5-35 mg and then decreased to 68.720% for 50 mg in 140 min under visible light illumination. The comparative study demonstrates that a higher degradation rate was achieved for cationic than anionic dyes in the order RhB > MB > MO. The highest deterioration (93.80%) was achieved for the RhB dye in 140 min. Equilibrium and kinetic studies showed that the adsorption process followed the Langmuir isotherm and pseudo-second-order models, respectively. The maximum adsorption capacity of 21.125 mg/g was observed for the catalyst concentration of 35 mg. From the cyclic test, it has been observed that the synthesized photocatalyst is structurally and morphologically stable and reusable. The radical trapping experiment demonstrated that superoxide and hydroxyl radicals were the primary species engaged in the photodegradation process. A possible mechanism for the degradation of RhB has been proposed. Hence, we conclude that CaCrO4 can be used as an efficient photocatalyst for the remediation of organic dye pollutants from the environment.

Preparation and characterization of calcined Ni/Mo hydrotalcite for the effective removal of lead from wastewater

ABSTRACT In this investigation, calcined Ni/Mo hydrotalcite was prepared via co-precipitation method and used as a sorbent for efficient removal of lead from aqueous solutions. The Pb2+ removal efficiency reached 99% at pH 6 and a sorbent dose of 2 g/L. The equilibrium data were satisfactorily fitted by the Langmuir and Hill models with a maximum capacity of 196.87 mg/g, indicating the monolayer sorption for lead over calcined Ni/Mo hydrotalcite. The Pb2+ sorption kinetic follows a pseudo-second-order reaction due to high correlation coefficients (R 2 > 0.99), while the Boyd’s plots confirm the external mass transfer as the rate-limiting step in the Pb2+ sorption. The temperature effect indicated a spontaneous and exothermic Pb2+ uptake. Mechanisms involved in the removal process include surface precipitation, diffusion into the solid pores and isomorphic substitution with Ni2+ of the sheets. The results showed excellent selectivity for Pb2+ removal from multi-divalent cation solutions and good reusability of the sorbent for up to 10 consecutive sorption–regeneration cycles without significant loss of the removal efficiency. As an application, the treatment of wastewater containing Pb2+, generated from the battery industry has been undertaken. The Pb2+ concentration was reduced from 5.7 to 0.6 mg/L, corresponding to an abatement of 89.5%. Therefore, the sorption using calcined Ni/Mo hydrotalcite is an efficient and suitable method for the elimination of Pb2+.

Effects of static magnetic field on the surface tension of surfactant solutions

AbstractThe magnetic field (MF) effects resulting from water or solution treatments are still of significant interest. However, a relatively small number of papers have been published dealing with the pure surfactant solutions alone. On the other hand, surfactants are applied in many industrial processes as well as in everyday life and are also present in different waste waters. Therefore, it seemed interesting to investigate whether some effects would appear after the MF treatment of pure aqueous surfactant solutions. In the earlier published papers after MF action the changes in water evaporation rate and the surface tension were found for both the cationic dodecyltrimethylammonium bromide (DTAB) and anionic sodium dodecyl sulfate (SDS) solutions. The gradient MF originated from three connected ring magnets inside which the solutions were placed. The objective of this paper is to study whether using the same magnets but in a different position the effects of the MF are observed. The given surfactant solution in a closed vessel was placed in an uniform MF when the magnets were in the “lying” position. The investigated solutions on the magnet surface remained for 24 h. In this paper, despite SDS and DTAB also the cationic hexadecyltrimethylammonium bromide (CTAB) and nonionic Triton X‐100 solutions were applied. It appeared that in the uniform MF the surface tension of cationic and anionic surfactant solutions changes. However, larger changes were observed in the gradient MF. Generally, the changes of surface tension depend on the surfactant kind and its concentration. Stronger MF influence was found for the cationic surfactant and almost no changes were observed for nonionic Triton X‐100.

Enhancement of the Texture & Morphology of Nano γ-Alumina as a Support for Naphtha Reforming Catalyst

The morphology of nano gamma alumina affects the molecule adsorption-desorption phenomena. In this case, manipulating the surface area, pore volume, and pore size by the technique of preparation to control the morphology and textural properties of gamma alumina. Washing of the synthesized boehmite gel with methanol has a significant effect. The co-precipitation method was used to prepare nano gamma alumina, which is involved by adding drop-by-drop ammonium hydroxide and aluminum nitrate nonahydrate solutions to a cetyltrimethylammonium bromide (CTAB) cationic surfactant solution at 30 C and adjust PH to 8. Nitrogen adsorption-desorption analysis (ASAP 2020), Atomic Force Microscope (AFM), and X-Ray Diffraction (XRD) were used to examine the obtained material. Surface area (362 m2/g), pore volume (0.51 cm3/g), pore size (5.2 nm), and narrow pore size distribution were obtained.

Highly sensitive and recognizable detection for trifluralin with alkyl-decorated fluorescent porous polymers

The sensing materials and portable devices with high sensitivity and specific recognition are urgently demanded for monitoring the pesticide residue in soil, water and food. Herein, two fluorescent porous polymers with carbazole-based chromophores decorated by n-butyls are synthesized through A3 + B2 and A3 + B4 condensation polymerizations, respectively. The hierarchical pores ranging from ultramicropore to mesopore are adjustable by varying the crosslinking density in the networks. The fluorescent quenching coefficient and limit of detection for trifluralin exceptionally reach 4.57 × 105 M−1 and 6.0 ppb, and the polymers exhibit ultra-sensitive recognizable ability for trifluralin in water. The quenching efficiencies for trifluralin in water, aqueous solutions of various cations and anions, vegetable juice and soil filtrate remain nearly the same. In particular, the fabricated polymer plates are portable and show visual fluorescent quenching for trifluralin solution at an extremely low concentration, and the plates can be easily recovered and repeatedly used. The results revealed in this manuscript are helpful for deeply understanding the effects of porosity parameters and alkyl-decorated chromophore groups on the sensitive and recognizable sensing mechanism for trifluralin.

Surface modification of polymers using cationic polyelectrolyte solutions

Surface modification of polymers using cationic polyelectrolyte solutions

Cationic Solution and Solid-State Emitters - Robust Imaging Agents for Cells, Bacteria, and Protists.

A library of eight different cationic emitters with emission properties in solution and in solid-state (solution and solid-state emitters - SSSE) is presented. These compounds, bearing either ammonium or pyridinium groups, have been investigated regarding their photophysical properties as well as their potential application in biological imaging. Besides high quantum yields as well as a high degree of stability during the imaging process, it was additionally revealed that a broad range of biological targets can be addressed, such as different bacterial strains, human cells as well as protists. The reported SSSE approach employing the mentioned robust emitters for biological imaging, will contribute to a rapid and facile way to design and apply affordable emitters with outstanding properties. Additionally, these emitters will overcome the drawbacks of classical luminophores and agents featuring well-known aggregation-induced emission (AIE) or aggregation-caused quenching (ACQ) properties.

Improving Crystallization and Stability of Perovskite Solar Cells Using a Low-Temperature Treated A-Site Cation Solution in the Sequential Deposition.

The two-step sequential deposition is a commonly used method by researchers for fabricating perovskite solar cells (PSCs) due to its reproducibility and tolerant preparation conditions. However, the less-than-favorable diffusive processes in the preparation process often result in subpar crystalline quality in the perovskite films. In this study, we employed a simple strategy to regulate the crystallization process by lowering the temperature of the organic-cation precursor solutions. By doing so, we minimized interdiffusion processes between the organic cations and pre-deposited lead iodide (PbI2) film under poor crystallization conditions. This allowed for a homogenous perovskite film with improved crystalline orientation when transferred to appropriate environmental conditions for annealing. As a result, a boosted power conversion efficiency (PCE) was achieved in PSCs tested for 0.1 cm2 and 1 cm2, with the former exhibiting a PCE of 24.10% and the latter of 21.56%, compared to control PSCs, which showed a PCE of 22.65% and 20.69%, respectively. Additionally, the strategy increased device stability, with the cells holding 95.8% and 89.4% of the initial efficiency even after 7000 h of aging under nitrogen or 20-30% relative humidity and 25 °C. This study highlights a promising low-temperature-treated (LT-treated) strategy compatible with other PSCs fabrication techniques, adding a new possibility for temperature regulation during crystallization.

Regression modelling for concentration dependent mass density and specific volume of aqueous surfactant solutions

ABSTRACT. In the present work, mathematical models relating mass density and specific volume of solution with concentration for aqueous solutions of anionic (sodium lauryl sulfate - SLS) and cationic (cetyltrimethylammonium bromide - CTAB) surfactants (0-10% (w/w)) have been investigated. The experimental studies were performed to study the effect of solution concentration on mass density and specific volume of solution. Mass density increases, and specific volume decreases with an increase in solution concentration for both surfactants. Linear, quadratic, cubic, quartic, quintic, and exponential models were fitted to the experimental data to check the applicability. The models were validated based on the coefficient of determination (R2) and the sum of square of error (SSE) to be unity and zero, respectively. Modelling results reveal that the quintic model was fitted to study the effect of density on solution concentration for both surfactants.
 
 KEY WORDS: Density, Surfactant, Cetyltrimethylammonium bromide, Sodium lauryl sulfate, Modelling, Regression
 
 Bull. Chem. Soc. Ethiop. 2023, 37(4), 1047-1054. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i4.19

Multifunctional Layer-by-Layer Coating Based on a New Amphiphilic Block Copolymer via RAFT-Mediated Polymerization-Induced Self-Assembly Process.

In this hi-tech world, the "smart coatings" have sparked significant attention among materials scientists because of their versatile applications. Various strategies have been developed to generate smart coatings in the past 2 decades. The layer-by-layer (LbL) technique is the most commonly employed strategy to produce a smart coating for suitable applications. Here, we present a smart coating with healing, antifogging, and fluorescence properties fabricated by the LbL assembly of an anionic amphiphilic block copolymer latex and cationic inorganic POSS (polyhedral-oligomeric-silsesquioxane) nanoparticles. In this case, a new anionic block copolymer (BCP), {poly(sodium styrene sulfonate)-block-poly[2-(acetoacetoxy)ethyl methacrylate]}, (PSS-b-PAAEMA) was synthesized via surfactant-free RAFT-mediated emulsion polymerization using the PISA technique. The PSS-b-PAAEMA was characterized by 1H NMR, dynamic light scattering, scanning electron microscopy, and transmission electron microscopy analyses as well as by UV-vis and photoluminescence spectroscopy. For LbL coating fabrication, an amine-modified glass was successively dipped in the anionic latex and cationic POSS solution. The transparent coating exhibited good fluorescence properties under UV light (blue color). The antifogging performance of the coating was also investigated using both cold-warm and hot-vapor techniques. Additionally, the coating surface showed a significant healing activity with a healing efficiency of >75% through ionic interaction. Thus, this finding provides a simple low volatile organic compound (VOC) water-based LbL coating with multifunctional properties that can be a potential material for versatile applications.

Role of pH and cations on emulsion formation and stability of crude oils

Emulsification plays a crucial role in various areas. However, undesirable emulsions, especially water-in-oil (W/O) emulsions, formed during crude oil production, transportation, processing, and stockpiling, become significant issues in the petroleum industry. Various studies have focused on evaluating the factors affecting emulsion stability and their mechanisms, which hardly explain the relationship with emulsion formation. This study assessed the effects of pH and cations on the transformation of emulsion types and their stability based on the observed emulsion formation process and emulsion particle sizes. It was found that the final W/O emulsions were transformed from water-in-oil-in-water (W/O/W) emulsions for all brine conditions. At neutral pH, more W/O emulsions were formed through the transformation of W/O/W emulsion, but the high pH broke down most of the W/O/W emulsion into free water and oil. Emulsion particles’ zeta potential or electrokinetics plays a significant role in W/O/W emulsion stability at high pH. The transformation of emulsion types in cation solutions was similar to neutral pH; the amount of W/O emulsion depends on cation species. The W/O/W emulsion stability under different pH in the following order: neutral pH < low pH < high pH, whereas final W/O emulsion stability is as follows: high pH < low pH < neutral pH; MgCl2 < CaCl2 < NaCl. The stability of the emulsion is influenced by the properties of the crude oil, such as viscosity and TAN/TBN ratio, which affect the oil film thickness of the W/O/W. Based on these findings, a stability mechanism is proposed for the emulsion under different pH and cations.

Mechanism of selective transportation of metal ions across chelating membranes in electrodialysis

The presented research explains the mechanism of selective transportation mass in electrodialysis by chelating membrane according to the electrosorption and specific diffusivity. The Nernst-Planck equation was applied for modelling and defining the character of mass transportation. The chelating membrane is developed by the chemical grafting of hydroxyquinoline (HQ), which guarantees selectivity. The investigation of mass transportation was determined using a single-component solution of transition metal cations like Co2+, Mn2+and Ni2+, as well as from alkaline metal classes like Li+ and Mg2+. Finally, the multi-component solutions were tested to confirm the chelating membrane's specific character and mass transportation mechanism. The chemical and electrochemical investigations like FTIR and EIS confirmed the appearance of the chelating reactions between membrane and cobalt cations only. According to the creation of aqua complexes of HQ and Co2+, the PAN-5C8Q membrane could transport in a significant majority only Co2+ against other mono- and divalent cations. The transport number against the Mn2+, Ni2+, Mg2+ and Li+ for Co2+got over 0.6.

Elecrtochemical Investigation of Heterogeneous Cation-Exchange Membranes Modified by Polyanilin in Solutions of Monovalent and Divalent Cations

A series of composite ion-exchange membranes based on a heterogeneous cation-exchange MK-40 membrane and polyaniline was obtained under the conditions of electrodiffusion of a monomer and an oxidizing agent. The process of polyaniline synthesis on the membrane surface was accompanied by the registration of chronopotentiograms and the pH of the solution leaving the desalination compartment. The initial MK-40 cation-exchange membrane and the composites based on it were studied by voltammetry and chronopotentiometry in NaCl, CaCl2, and MgCl2 solutions in the same electrodialysis flow cell in which the composites were obtained. To calculate the transport numbers of counterions in membranes in CaCl2 and MgCl2 solutions by the chronopotentiometric method, the apparent fraction of the conducting membrane surface in the NaCl solution was calculated based on experimental data on the potentiometric transport numbers of counterions in the membrane. The conditions for the synthesis of polyaniline on the surface of a heterogeneous MK-40 membrane, leading to the preparation of samples with selectivity to singly charged ions, are revealed.

Nanoparticle-induced drag reduction for polyacrylamide in turbulent flow with high Reynolds numbers

• Nanoparticles enhance the drag reduction effect of polyacrylamide solution. • The drag reduction of nanoparticles and polyacrylamide is observed at Re over 6000. • The combination of nanoparticles with cationic polyacrylamide is optimized. • Nanoparticles act as nodes to protect the polymer chain from shear breaking. Although having been increasingly studied, there is still controversy as to when the addition of nanoparticles could improve the drag reduction performance of polymer drag reducer and particularly what is the underlying mechanism from the fluid dynamics viewpoint. The drag reduction effects of adding SiO 2 nanoparticles to various polymer polyacrylamide (PAM) solutions were examined in this work. The optimal combination of SiO 2 nanoparticles with cationic polyacrylamide was confirmed. Interestingly, the addition of SiO 2 nanoparticles to cationic polyacrylamide solution was shown to be quite efficient for reducing drag, but only at higher flow rates with Reynolds numbers more than 6000, below which the nanoparticle addition is even negative. The addition of SiO 2 nanoparticles to the PAM solution is supposed to play a dual role. The first is an increase in flow resistance caused by the Brownian motion of nanoparticles, while the second is a decrease in flow resistance caused by acting as nodes to protect the polymer chain from shear-induced breaking under high shear action. At optimal nanoparticle concentration and under higher Reynolds numbers, the later effect is dominant, which could improve the drag reduction performance of polymer drag reducers. Our work should serve as a guide for the application of natural gas fracturing, where the flow rate is frequently very high.

Synthesis of SnS/SnO Nanostructure Material for Photovoltaic Application

Research Highlights&#x0D; &#x0D; Successfully synthesized SnS/SnO nanostructured material using successors ionic layer absorption and reaction (SILAR) technique.&#x0D; Granular nanocrystals were visible in the materials, and they were strewn unevenly and randomly throughout the glass surface.&#x0D; It was found that the sample processed at room temperature had the largest energy band gap.&#x0D; The transmittance in the visible area of the spectrum was stable and SnS/SnO was at its maximum in the UV region&#x0D; &#x0D; In this research, the SILAR method was used to synthesize environmentally-friendly SnS/SnO material for photovoltaic application, where 0.1 M of tin (II) chloride dihydrate (SnCl2.2H2O) was used to create the cationic precursor solution, and 0.01 M of thioacetamide (C2H5NS) was used to create the anionic precursor solution. The X-ray diffraction patterns of SnS/SnO material deposited on glass substrate at various deposition temperatures recorded a major peak at 45oC at 2 theta of 31.8997o, which corresponds to the face-centered cubic crystal structure (FCC). Diffraction peaks are visible in the pattern at planes 111, 200, 210, 211, and 300, which correspond to angles of 26.58°, 31.89°, 39.61°, 44.18°, and 54.85°, respectively. It was discovered that the crystallite/grain size and the lattice parameters decrease as the temperature of the deposition material rises. Granular nanocrystals were visible in the materials, and they were strewn unevenly and randomly throughout the glass surface. The spectra of the absorbance demonstrate that as light radiation passed through SnS/SnO films, it absorbed radiation as the wavelength increased from the UV region to the ultraviolet region of the spectra. It was discovered that the precursor temperature influences the material's absorbance; as the temperature rises, the absorbance decreases, making SnS/SnO an excellent material for photovoltaic systems. The transmittance in the visible area of the spectrum was stable and SnS/SnO was at its maximum in the UV region, it increased as the wavelength increased in the NIR region. It was found that the sample processed at room temperature had the largest energy band gap. SnS/SnO reveals an increase in thickness from 114.42 – 116.54 nm which resulted in a downturn in the resistivity of the deposited film from 9.040×109 – 6.455×109 (Ω·cm) while the conductivity of the deposited material increased from 1.106×10-10 – 1.549×10-10 (Ω·cm)-1.

Effect of Surfactants on Reverse Osmosis Membrane Performance

The aim of this study was to evaluate the performance of a reverse osmosis (RO) membrane in surfactant removal using various surfactant model aqueous solutions. The separation tests were performed with laboratory scale units in a dead-end configuration. Cellulose Acetate (CA) and Polyamide (PA) RO membranes were used with nonionic, anionic, or cationic surfactants at a wide range of concentrations. Membrane performance was evaluated using permeate flux and total organic carbon (TOC) rejection. The effects of surfactant type and concentration on RO membranes were assessed. Permeate flux of the PA membrane depended on the surfactant type and concentration. The separation of cationic surfactant aqueous solutions yielded the lowest permeate flux, followed by nonionic and anionic surfactant aqueous solutions, respectively. Surfactant adsorption on the membrane surface occurred at very low concentration of cationic and nonionic surfactants due to electrostatic and hydrophobic interactions, respectively, which affected permeate flux, and micelles did not affect the permeate flux of PA membrane. However, for CA membrane the permeate flux was not affected by the feed solution. Both membranes exhibited satisfactory TOC rejection (92–99%). This study highlights the importance of assessing interactions between membrane material and surfactant molecules to mitigate membrane fouling and guarantee a better performance of the RO membrane.

An endoscopically compatible fast-gelation powder forms Janus-adhesive hydrogel barrier to prevent postoperative adhesions

Postoperative adhesions occur widely in various tissues, bringing the risk of secondary surgery and increased medical burden. Hydrogel barriers with Janus-adhesive ability can achieve physical isolation of adjacent tissues and are therefore considered an ideal solution. However, integrating endoscopic delivery convenience and viscoelastic Janus hydrogel formation remains a great challenge. Here, we present a report of the insitu formation of Janus-adhesive hydrogel barrier using a sprayable fast-Janus-gelation (FJG) powder. We first methacrylate the polysaccharide macromolecules to break the intermolecular hydrogen bonds and impart the ability of rapid hydration. FJG powder can rapidly absorb interfacial water and crosslink through borate ester bonds, forming a toughly adhesive viscoelastic hydrogel. The Janus barrier can be simply formed by further hydrating the upper powder with cationic solution. We construct rat models to demonstrate the antiadhesions efficiency of viscoelastic FJG hydrogels in organs with different motion modalities (e.g., intestine, heart, liver). We also developed a low-cost delivery device with a standardized surgical procedure and further validated the feasibility and effectiveness of FJG powder in minimally invasive surgery using a preclinical translational porcine model. Considering the advantages in terms of therapeutic efficacy, clinical convenience, and commercialization, our results reveal the great potential of Janus-gelation powder materials as a next-generation antiadhesions barrier.

Simultaneous removal of aqueous same ionic type heavy metals and dyes by a magnetic chitosan/polyethyleneimine embedded hydrophobic sodium alginate composite: Performance, interaction and mechanism

Heavy metals and azo dyes caused huge harm to the aqueous system and human health. A magnetic chitosan/polyethyleneimine embedded hydrophobic sodium alginate composite (MCPS) was designed and prepared to simultaneously remove aqueous same ionic type heavy metals and azo dyes. In mono-polluted system, the optimal pH for Cr(VI), MO (methyl orange), Cu(Ⅱ) and MB (methylene blue) were 3, 2, 6 and 12 with a saturated adsorption capacity of 87.53, 66.41, 351.03 and 286.54 mg/g, respectively. Pseudo-second-order was suitable to describe the adsorption kinetics of them and the adsorption isotherms were more consistent with the Langmuir isotherm model being a spontaneous, endothermic, and entropy-increasing process. In binary-polluted system, MCPS possessed simultaneous adsorption for Cr (Ⅵ)-MO and Cu(Ⅱ)-MB pollutants at their optimal pH, in addition, whether in anionic or cationic solution, the removal of heavy metals were promoted with the add of azo dyes but the removal of azo dyes were suppressed with the add of heavy metals. Both Cr (Ⅵ)-MO and Cu(Ⅱ)-MB pollutants could be effectively adsorbed and desorbed from MCPS by changing the pH of the aqueous solution to realize recyclability. Lastly, removal mechanism was revealed in detail by FT-IR, EDS and XPS.

Mitigation of tribocorrosion of metals in aqueous solutions by potential-enhanced adsorption of surfactants

Corrosion and corrosive wear occur commonly on metals surface in aqueous solutions. External electric field is usually considered as one of the factors to accelerate corrosion or corrosive wear of materials in the presence of conventional electrolytes. This work aims to reposition widely believed perspective by experimental justification which have been conducted in aqueous solutions containing surfactants. Electric potential of metal surfaces was modulated externally within the electrochemical potential window of the metal electrode-solution-counter electrode system, which actively regulated the adsorption or desorption of surfactant molecule in the aqueous solution over the electrodes to form a molecular barrier of electron transportation across the electrode-electrolyte interface. The advantage of the approach over the anodic passivation is negligible redox reactions on the protected electrode surface while a better lubricious and wear resistant film than oxide is maintained in the meantime. Tribopairs of several metal/metal and metal/ceramic were tested by employing a ball-on-disc tribometer with anionic and cationic surfactants solutions. For anionic surfactant as the modifier, positive surface potential enables coefficient of friction to be decreased by promoting the formation of adsorption film on metal surface in aqueous solutions. For cationic surfactant, negative surface potential plays a role in decreasing the coefficient of friction. Phase diagrams of friction and wear in wide ranges of surfactant concentration and surface potential were plotted for the tested metal/metal and metal/ceramic tribopairs. These results indicate that the adsorption behavior of molecules or ions at the metal-aqueous interface can be well regulated when an external electric field is present without inducing corrosion or corrosive wear.