Increasing Surface Coverage Research Articles

Effect of spinach (Spinacia oleracea) leaf extract on the aluminum (Al) as a green corrosion inhibitor in HCl medium

Green corrosion inhibitors have recently attracted much attention due to their non-toxic properties, especially plant extracts. This study used spinach leaf extract (Spinacia oleracea) as a corrosion inhibitor on aluminum in an HCl medium. Spinach leaf extract (Spinacia oleracea) was obtained by maceration method, using ethanol as the solvent, which was then distilled to purify the extract. The corrosion inhibition properties were studied by the gravimetric method. The results showed that spinach leaf extract (Spinacia oleracea) can efficiently decrease the corrosion rate of aluminum in an HCl medium, achieving a maximum efficiency of 96.7742 %. Spinach leaf extract (Spinacia oleracea) formed a protective layer on the aluminum surface via adsorption and chemisorption, thus increasing surface coverage and blocking mass transfers. As the inhibitor concentration increases, the corrosion rate decreases, and the corrosion inhibition efficiency increases. This study shows that spinach leaf extract (Spinacia oleracea) is a viable organic corrosion inhibitor option with high efficiency.

Surface Loading Dictates Triplet Production via Singlet Fission in Anthradithiophene Sensitized TiO2 Films.

Singlet fission, the process of transforming a singlet excited state into two lower energy triplet excited states, is a promising strategy for improving the efficiency of dye-sensitized solar cells. The difficulty in utilizing singlet fission molecules in this architecture is understanding and controlling the orientation of dyes on mesoporous metal oxide surfaces to maximize triplet production and minimize detrimental deactivation pathways, such as electron injection from the singlet or excimer formation. Here, we varied the concentration of loading solutions of two anthradithiophene dyes derivatized with either one or two carboxylic acid groups for binding to a metal oxide surface and studied their photophysics using ultrafast transient absorption spectroscopy. For the single carboxylic acid case, an increase in dye surface coverage led to an increase in apparent triplet excited-state growth via singlet fission, while the same increase in coverage with two carboxylic acids did not. This study represents a step toward controlling the interactions between molecules at mesoporous interfaces.

Effect of Ash and Sulphate on Corrosion of Ni-Based Alloys in a Simulated Oxyfuel Combustion Environment

AbstractAlloys of Ni–25Cr–(2Mn–1Si) under mixed deposits of ash + (0, 10, 50 and 90) wt% sulphate were exposed to an Ar–60CO2–20H2O gas at 650 and 750 °C for up to 300 h, forming both protective chromia and regions of Ni-rich oxide. The presence of ash + sulphate mixtures improved Ni–25Cr alloy protection, increasing surface coverage by thin, protective chromia compared with the deposit-free condition. Increasing sulphate proportions in these mixtures led to an accelerated chromia scale growth and reduced internal oxidation zone (IOZ). These beneficial effects were more significant at 750 °C, where surface coverage by the protective scale was increased, and a chromia band was formed beneath nonprotective regions at the IOZ-substrate interface. Alloy additions of Mn and Si generally slowed the growth of outer NiO and IOZ but did not lead to exclusive chromia scale formation.

Insight into the role of droplets in quinoa starch-based Pickering high internal phase emulsion for enzymatic hydrolysis reaction

Pickering high internal phase emulsion has emerged as potential platforms for biocatalytic reactions. Herein, native quinoa starch was used as the emulsifier to form a stable Pickering HIPE with an internal phase up to 80 %. The catalytic performance of lipase loaded in HIPE was evaluated for the enzymatic hydrolysis of hexyl hexanoate. Compared with the typical Pickering emulsion, biphasic, and monophasic systems, the Pickering HIPE system displayed higher conversion (83.54 % at 1440 min) and specific enzyme activity (1.41 U/mg), thus emphasizing the crucial role of microdroplets and large interface area created by both the starch particles and high internal phase volume. Subsequently, HIPEs with different starch concentrations were fabricated to further understand the catalysis behavior happening at compartmentalized microdroplets and interfaces. The microstructural, interfacial, and rheological properties of the HIPEs were systematically determined to explain the correlation between emulsion properties and catalytic efficiency. High starch concentration reduced the droplet size and increased the interfacial area, thus shortening the mass transfer distance and enlarging the reaction area. Meanwhile, the increased surface coverage and viscosity led to poor accessibility and limited mass movement. This trade-off made the maximum conversion be obtained at 2 wt% concentration. The study provides novel information about the role of emulsion droplets in the catalytic performance of lipase in starch-based HIPE.

Shot peening coverage effect on laser powder bed fused steel

Developing effective strategies for enhancing the damage tolerance of laser powder bed fusion (LPBF) components remains a formidable challenge in the disruptive additive manufacturing field. The typical shot-peening (SP) is a promising and efficient post-treatment procedure owing to its capability to introduce compressive residual stress, enhance the surface integrity, shrinkage the subsurface lack-of-fusion (LoF) defects of LPBF components. However, there is still a significant gap in understanding the appropriate utilization of the SP procedure to enhance fatigue performance, hindering its full potential in practical applications. This study systematically investigated the influence of surface coverage (150 %, 300 %, and 450 %) on surface characteristics, subsurface characteristics, and mechanical properties of LPBF 304L austenitic steel. Though evaluating the feasibility of severe shot peening and observing post-deformed microstructures, the process-microstructure-performance relationship of shot-peened LPBF austenitic steel was preliminarily established for the first time. The results indicated that increasing surface coverage up to a threshold (300 % in this work) could effectively enhance the strength and fatigue performance without significantly sacrificing ductility, primarily attributed to the increased gradient strain generated by the gradient deformation structures as well as the shrinkage of detrimental near-the-surface defects. The excessive surface coverage may be detrimental to ductility and fatigue performance, as it directly increases the severe plastic deformation and near-saturated micro-defects in the gradient deformation layer, substantially weakening the strain gradient's capability to accommodate dislocation flow during deformation. The findings suggested careful selection of shot peening coverage to balance enhanced mechanical properties and minimal introduction of detrimental defects.

Enhanced Efficiency and Stability of Sky Blue Perovskite Light-Emitting Diodes via Introducing Lead Acetate.

All-inorganic metal halide perovskite is promising for highly efficient and thermally stable perovskite light-emitting diodes (PeLEDs). However, there is still great room for improvement in the film quality, including low coverage and high trap density, which play a vital role in achieving high-efficiency PeLEDs. In this work, lead acetate (Pb(Ac)2) was introduced into the perovskite precursor solution as an additive. Experimental results show that perovskite films deposited from a one-step anti-solvent free solution process with increased surface coverage and reduced trap density were obtained, leading to enhanced photoluminescence (PL) intensity. More than that, the valence band maximum (VBM) of perovskite films was reduced, bringing about a better energy level matching the work function of the hole-injection layer (HIL) poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT: PSS), which is facilitated for the hole injection, leading to a decrease in the turn-on voltage (Vth) of PeLEDs from 3.4 V for the control device to 2.6 V. Finally, the external quantum efficiency (EQE) of the sky blue PeLEDs (at 484 nm) increased from 0.09% to 0.66%. The principles of Pb(Ac)2 were thoroughly investigated by using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). This work provides a simple and effective strategy for improving the morphology of perovskite and therefore the performance of PeLEDs.

Near Equilibration Times in the Diffusion-Controlled Adsorption.

A model of the Frumkin isotherm following adsorption on the surface of the rotating disk is developed with the purpose to calculate the time that is needed for the establishment of the near equilibrium state between the amount of adsorbate and the bulk concentration of surfactant. The "near" is quantified as 99% of the proper equilibrium surface coverage. The near equilibration time depends on the bulk concentration and on the coefficient of molecular attraction in the adsorbed layer. In the vicinity of the inflection point of the isotherm, this time exhibits sharp spike. It is caused by the diminished flux that increases surface coverage very slowly but continues for a long time. Eventually, both the flux and the surface coverage increase with time drastically under the influence of the exponential part of the Frumkin isotherm.

Study the Effect of “Di-dodecyl amine” as a Corrosion Inhibitor for Carbon Steel in HCl Medium

Numerous organic compounds have been investigated for their potential to reduce corrosion under various circumstances. This study investigated the effects of di-dodecyl amine, an organic chemical, on carbon steel metal corrosion at different temperatures while HCl acid was present. The examination was carried out using accepted methods for polarization, weight loss, and corrosion process testing. The obtained findings demonstrated that the corrosion rate reduces with increasing inhibitor concentration, leading to increased inhibition efficiency. Furthermore, as shown in the weight loss technique, the corrosion rate lowers with increasing surface coverage with organic inhibitor at 313 °C. In the anodic and cathodic polarization methods, as well as in the inhibition efficiency, it is observed to see the cathodic and anodic curves through which the occurrence of the potential and corrosion current is known. The current and corrosion potential decreases with increasing inhibitor concentration. The amines and methyl motiveless in this inhibitor's composition give it their efficacy since they may coat the metal surface and stop corrosion

The Antibacterial Activity of Hierarchical Patterns of Nanostructured Silicon Fabricated Using Block Copolymer Micelle Lithography

Herein, the fabrication of four different nanostructured silicon surfaces by using a combination of block copolymer micelle lithography is reported on. Nanoparticle hard masks are evaluated for their ability to produce single‐height nanoneedle arrays. Low‐density (3 features μm−2) and high‐density (201 features μm−2) single‐height arrays are produced from Au or α‐Fe2O3 masks, respectively. These single‐height arrays are then used as substrates to produce nanostructured surfaces with two distinct nanoneedle arrays concerning height, diameter, and density. These dual‐height arrays have feature densities of 31 and 9 features μm−2. All surface types are then tested for their antibacterial activity against Gram‐negative bacteria, Pseudomonas fluorescens, over 24 h. No difference in surface coverage of P. fluorescens when comparing the structured silicon surface types to planar controls is observed. However, all of the structured silicon types show an increase in dead cell surface coverage ranging from 9 to 29% compared to planar controls. Density of the pillars appears to be more important than the difference in height of pillars when it comes to antibacterial activity. This work seeks to add to the literature by investigating the effects of feature density, as well as the impact of a dual‐height arrangement of nanoneedles against P. fluorescens.

Thermally annealed large-scale gold nanostructure platform for long-term and label-free electrochemical monitoring of cellular metabolism

In recent developments, an electrochemical method has emerged as a promising tool that enables real-time and non-destructive monitoring of cell viability and functionality in vitro. However, the restricted cell cultivation area and poor adhesion properties of the gold nanostructure film impede its potential as a new analytical tool for cellular research. In this study, we present an advanced platform designed for prolonged cell growth, differentiation, and drug screening, while providing electrochemical detection capability. The thermal annealing process, implemented after gold nanostructure deposition, was found to induce structural reformation on the indium tin oxide (ITO) film through Ostwald ripening and coalescence, leading to increased surface coverage and reduced height. The resulting optimized platform, referred to as the thermally annealed large-scale gold nanostructure (TLGN), offers an expanded cell culture area (about 227 mm2) with sustained resistance to gold film detachment, a critical challenge observed in previously reported electrodes, lasting up to 4 weeks under exposure to cell culture medium. Using TLGN, redox signals were successfully detected from a substantial number of human cervical cancer cells (470,000 cells) at days in vitro 5, a cell count that is 10.35 times higher compared to our previous gold nanostructure electrode. The cells were continuously monitored for up to 4 days under treatment with the anticancer drug (CB-839). Furthermore, the TLGN platform demonstrated its effectiveness in electrochemically monitoring the osteogenesis of human mesenchymal stem cells over a differentiation period of 28 days, based on observed changes in cellular metabolism. In summary, the TLGN platform proves invaluable not only for assessing drug accumulation and potential cytotoxicity at the cellular level but also for real-time monitoring of mitochondrial dynamics during cellular differentiation.

On the surface segregation of Sn in cold-rolled Fe under continuous annealing conditions

The surface segregation of Sn in cold-rolled Fe-0.03Sn and Fe-0.01Sn (at.%) model alloys was investigated for annealing parameters characteristic of continuous galvanizing lines (CGLs). The most significant increase in surface coverage occurred during linear heating between 500 and 675 °C, where no significant change in segregation was observed with isothermal holding for 60 – 480 s at peak annealing temperatures of 675 – 825 °C. While the bulk diffusion of Sn in Fe determined the segregation rate during extended isothermal holding up to 10800 s, it could not account for the rapid increase in coverage during heating. It was determined that Sn segregation was accelerated during linear heating by rapid diffusion along dislocation pipes in the cold-rolled starting microstructure. Integrating the decrease in diffusivity due to recrystallization into the McLean model for interfacial segregation resulted in an experimentally verified description of segregation kinetics during linear heating. It was also able to predict the experimentally observed increase in segregation when the linear heating rate between 500 °C and 675 °C was decreased from 5 to 1 °C/s. No significant difference in surface segregation was observed between the 0.01 and 0.03 at.% Sn addition for isothermal holding of 480 s or less, which can be explained by the saturation of easy adsorption sites. A bond-breaking model was used to illustrate their origin from imperfect coordination within the surface layer. As significant surface segregation can be achieved within the CGL processing window, Sn microalloying appears as a promising strategy to improve galvanized coating quality.

Effects of Organic Surface Contamination on the Mass Accommodation Coefficient of Water: A Molecular Dynamics Study.

The mass accommodation coefficient (MAC), a parameter that quantifies the possibility of a phase change to occur at a liquid-vapor interface, can strongly affect the evaporation and condensation rates at a liquid surface. Due to the various challenges in experimental determination of the MAC, molecular dynamics (MD) simulations have been widely used to study the MAC on liquid surfaces with no impurities or contaminations. However, experimental studies show that airborne hydrocarbons from various sources can adsorb on liquid surfaces and alter the liquid surface properties. In this work, therefore, we study the effects of organic surface contamination, which is immiscible with water, on the MAC of water by equilibrium and nonequilibrium MD simulations. The equilibrium MD simulation results show that the MAC decreases almost linearly with increasing surface coverage of the organic contaminants. With the MAC determined from EMD simulations, the nonequilibrium MD simulation results show that the Schrage equation, which has been proven to be accurate in predicting the evaporation/condensation rates on clean liquid surfaces, is also accurate in predicting the condensation rate at contaminated water surfaces. The key assumption about the molecular velocity distribution in the Schrage analysis is still valid for condensing vapor molecules near contaminated water surfaces. We also find that under nonequilibrium conditions the adsorption of the water vapor molecules on the organic surface results in an adsorption vapor flux near the contaminated water surface. When the water surface is almost fully covered by the model organic contaminants, the adsorption flux dominates over the water condensation flux and leads to a false prediction of the MAC from the Schrage equation.

FeCx-coated biochar nanosheets as efficient bifunctional catalyst for electrochemical detection and reduction of 4-nitrophenol

Herein, we present the exceptional performance of FeCx-coated carbon sheets (FC) derived from the pyrolysis of waste biomass as a bifunctional catalyst for electrochemical detection and catalytic reduction of 4-nitrophenol (4-NP). Despite having a lower surface area, larger particle size, and lesser N content, the FC material prepared at a calcination temperature of 900 °C (FC900) outperforms the other samples. Deeper investigations revealed that the FC900 efficiently facilitates the charge transfer process and enhances the diffusion rate of 4-NP, leading to increased surface coverage of 4-NP on the surface of FC900. Additionally, relatively weaker interactions between 4-NP and FC900 allow the facile adsorption and desorption of reaction intermediates. Due to the synergetic interplay of these factors, FC900 exhibited a linear response to changes in 4-NP concentration from 1 μM to 100 μM with a low limit of detection (LOD) of 84 nM (S/N = 3) and high sensitivity of 12.15 μA μM−1 cm−2. Importantly, it selectively detects 4-NP in the presence of five times more concentrated 2-aminophenol, 4-aminophenol, catechol, resorcinol, and hydroquinone and ten times more concentrated metal salts such as Na2SO4. NaNO3, KCl, CuCl2, and CaCl2. Moreover, FC900 can accurately detect micromolar levels of 4-NP in river water with high recovery values (99.8–103.5 %). In addition, FC900 exhibited outstanding catalytic activity in reducing 4-NP to 4-aminophenol (4-AP), achieving complete conversion within 8 min with a high-rate constant of 0.42 min−1. FC900 also shows high recyclability in six consecutive catalytic reactions due to Fe magnetic property.

Investigation of the interfacial phenomena in the presence of nonionic surfactants and a silica nanoparticle at the n-decane-water interface: Insights from molecular dynamics simulation

In chemical enhanced oil recovery (EOR), the nanoparticles can be employed as conveyors to transfer the surfactants and impede the reduction of surfactant concentration. Here, a set of molecular dynamic simulations were carried out to examine the ability of hydrophobic silica nanoparticle (NP) to deliver the nonionic surfactant (Triethylene glycol monododecyl ether; C12E3) into the n-decane-water interface. Another set of simulations in which only surfactant molecules are initially located at the interface was performed in order to better characterize the influence of NP on the surfactant adsorption film.The NP exhibited high efficiency in delivering surfactant molecules to the n-decane-water interface. In addition, for the C12E3-NP and n-decane-NP, the Coulombic interactions are weaker than the van der Waals interactions confirming the nonpolar property of the silica nanoparticle. The density profiles indicate that as the concentration of surfactants increases at the interface, NP separates more from the surfactant layer. The interfacial tension (IFT) of n-decane-water systems containing only surfactants decreases as the surface coverage of the surfactants increases. Moreover, it was also proved that the intrinsic width of the interface increases with an increment in the surface coverage of surfactants. The surfactant molecules exhibit a great tendency to contribute as acceptors to the formation of hydrogen bonds with water molecules. With an increment in the surface coverage of surfactant molecules, the 2D radial distribution functions between the centers of mass (COMs) of surfactant tails show oscillations. Appeared oscillations represent the correlation between the surfactant tails. Presence of NP causes the oscillations start at lower surfactant coverage than without NP. The surfactant tails choose a random distribution at the low surface coverage of surfactants. In addition, they tend to be oriented partially perpendicular to the interface with an increase in surfactant surface coverage. Besides, NP causes the surfactant tails to orient more perpendicular to the interface than surfactants alone.

IONIC RADII OF HALIDE IONS AND ITS CORROSION INHIBITORY ENHANCEMENT ON SIDA ACUTA.

Corrosion Inhibitory efficiencies of Sida acuta leaf extracts in combination with halide ions (F-, Cl-, Br- and I-) as an enhancement on aluminum corrosion in H2SO4 was studied at room temperature (25oC) under varying acid concentrations of 0.05M, 0.1M and 0.5M using weight loss method. From the results obtained, Sida acuta acts as a good inhibitor for aluminum corrosion in acidic environment and it's inhibitory efficiencies increases with time of exposure. Based on the experimental results, the corrosion rate increases rapidly in the blank with a weight loss accelerating from 0.009g to 0.038g but with the introduction of plant extract, weight loss got reduced from 0.007g to 0.027g as well as having inhibition efficiency of 36% to 12% as the concentration of the acid was increased from 0.05M to 0.5M over the time series of 24 h to 96 h.. However, the inhibitory efficiency of Sida acuta in H2SO4 medium was further improved when halide ions were introduced. The weight loss of NaI moved from 0.002g to 0.011g and hence had the highest inhibition efficiency among the halide ions from 78% to 50% , NaBr showed a weight loss ranging from from 0.003g to 0.022g as well as having inhibition efficiency of 67% to 42% while NaCl showed a weight loss of 0.005g to 0.023g as well as having inhibition efficiency of 55% to 32% as the acid concentration was increased from 0.005M to 0.5M over the time exposure of 24 h to 96 h.. Nevertheless, the weight loss of NaF increases rapidly from 0.020g to 0.050g even more than the blank under the same reaction conditions and hence does not show inhibition efficiency. Therefore, the increase in inhibition efficiency (%I) and surface coverage (?) in the presence of the halides was found to be in a special sequence. . This synergistic effect increased according to the following pattern Cl- < Br -< I- suggesting a possible role by ionic radii in the corrosion inhibitory process which also increase in the order, F/F – ( 0.072/0.133nm), Cl/ Cl- (0.099/0.181nm) < Br/ Br - ( 0.114/ 0.195nm) < I/ I- ( 0.133/0.216 nm) . Fluoride ion does not show any inhibitory enhancement on Sida acuta owing to its least ionic radius..

IONIC RADII OF HALIDE IONS AND ITS CORROSION INHIBITORY ENHANCEMENT ON SIDA ACUTA.

Corrosion Inhibitory efficiencies of Sida acuta leaf extracts in combination with halide ions (F-, Cl-, Br- and I-) as an enhancement on aluminum corrosion in H2SO4 was studied at room temperature (25oC) under varying acid concentrations of 0.05M, 0.1M and 0.5M using weight loss method. From the results obtained, Sida acuta acts as a good inhibitor for aluminum corrosion in acidic environment and it's inhibitory efficiencies increases with time of exposure. Based on the experimental results, the corrosion rate increases rapidly in the blank with a weight loss accelerating from 0.009g to 0.038g but with the introduction of plant extract, weight loss got reduced from 0.007g to 0.027g as well as having inhibition efficiency of 36% to 12% as the concentration of the acid was increased from 0.05M to 0.5M over the time series of 24 h to 96 h.. However, the inhibitory efficiency of Sida acuta in H2SO4 medium was further improved when halide ions were introduced. The weight loss of NaI moved from 0.002g to 0.011g and hence had the highest inhibition efficiency among the halide ions from 78% to 50% , NaBr showed a weight loss ranging from from 0.003g to 0.022g as well as having inhibition efficiency of 67% to 42% while NaCl showed a weight loss of 0.005g to 0.023g as well as having inhibition efficiency of 55% to 32% as the acid concentration was increased from 0.005M to 0.5M over the time exposure of 24 h to 96 h.. Nevertheless, the weight loss of NaF increases rapidly from 0.020g to 0.050g even more than the blank under the same reaction conditions and hence does not show inhibition efficiency. Therefore, the increase in inhibition efficiency (%I) and surface coverage (?) in the presence of the halides was found to be in a special sequence. . This synergistic effect increased according to the following pattern Cl- < Br -< I- suggesting a possible role by ionic radii in the corrosion inhibitory process which also increase in the order, F/F – ( 0.072/0.133nm), Cl/ Cl- (0.099/0.181nm) < Br/ Br - ( 0.114/ 0.195nm) < I/ I- ( 0.133/0.216 nm) . Fluoride ion does not show any inhibitory enhancement on Sida acuta owing to its least ionic radius..

Chemical vapour deposition in narrow capillaries: Electro-osmotic flow control in capillary electrophoresis

BackgroundIn capillary electrophoresis (CE), the inner surface of fused-silica capillaries is commonly covalently modified with liquid silanes to control electroosmotic flow (EOF). This liquid phase deposition (LPD) approach is challenging for long and narrow-diameter capillaries (≥1 m, ≤25 μm ID) inhibiting commercial production. Here, we use chemical vapour deposition (CVD) to covalently modify capillaries with different silanes. Using a home-built CVD device, capillaries were modified with neutral (3-glycidyloxypropyl) trimethoxysilane (GPTMS), the weak base (3-aminopropyl) trimethoxysilane (APTMS), the weak acid 3-mercaptopropyltrimethoxysilane (MPTMS) and the neutral hydrophobic trichloro(1H,1H,2H,2H-perfluorooctyl) silane (PFOCTS). Gas-phase modification of GPTMS with acid and ammonia allowed further modification of the surface prior to molecular layer deposition (MLD) of poly(p-phenylene terephthalamide) (PPTA) using the self-limiting sequential reaction between terephthalaldehyde (TA) and p-phenylenediamine (PD) vapours. ResultsCapillaries coated with GPTMS by CVD showed a greater reduction in EOF at all pH values than the conventional LPD. APTMS showed a reduction of the EOF at pH 9, with EOF reversal observed below pH 6. MPTMS provided a slightly lower EOF than an unmodified capillary at high pH, and a slightly higher EOF at lower pH. PFOCTS provided the most consistent EOF as a function of pH. The deposition of successive layers of PPTA resulted in increased surface coverage of the polymer and a greater reduction in EOF at pH higher than 5. The stability of a 10 μm ID GPTMS coated capillary was tested at pH 8.8 in a 200 mM CHES/Tris BGE for the separation of inorganic anions. Over 1.5 months of continuous operation (≈4130 runs), the reproducibility of the apparent mobilities for chloride, nitrite, nitrate and sulfate were 2.43%, 2.56%, 2.63% and 3.05%, respectively. The intra-day and inter-day column-to-column reproducibility and batch-to-batch reproducibility for all the coated capillaries ranged between 0.34% and 3.95%. SignificanceThe study demonstrates the superior performance of CVD coating for suppressing the EOF compared to LPD allowing the easy modification of long lengths of narrow capillary. The variation in silane, and the ability of MLD to modify and control the surface chemistry, provides a simple and facile method for surface modification. The stability of these coatings will allow long-term capillary electrophoresis monitoring of water chemistry, such as for monitoring fertiliser run-off in natural waters.

Apparent Failures in Interpretation of Interfacial Characterization When Formulating Emulsions Stabilized by Cellulose Nanocrystals.

Cellulose nanocrystals (CNCs) are sustainable particles that are effective at stabilizing emulsions by adsorbing at droplet interfaces and providing a steric barrier to coalescence. However, CNCs have surface charges that reduce the coverage of the emulsion droplets due to the electrostatic repulsion between CNCs. In such cases, adding salt is a typical (and straightforward) way to adjust the formulation so that the charges are screened, allowing increased coverage of the droplets. At the outset of this work, we hypothesized that characterization of the interfacial tension and interfacial shear rheology of the oil-water interface would be correlated to interfacial coverage and therefore predictive of the optimal salt concentration for emulsion stability. Included in the methods section as a useful reference to others is the presentation of a detailed derivation for the equations needed to compute interfacial shear moduli in a custom, double-gap geometry. In contrast to our hypothesis, we found that interfacial tension did not correlate well with emulsion stability and that the native surface-active compounds in corn oil overwhelmed any influence of the CNCs on the interfacial tension. Additionally, we found that interfacial shear rheology (which can be painstakingly difficult to measure) was not a useful tool for formulating these emulsions. This is because at commonly used concentrations of CNCs, the bulk rheology is increased to a much greater degree than that of the interface, making the details of the interfacial rheology unimportant. Finally, we found that at concentrations of CNCs that are typical in industrial processes, characterizing the bulk viscoelastic properties of the aqueous suspending phase without added oil (a relatively simple measurement) is sufficient to predict the influence of NaCl concentration on charge screening between the CNCs and, by extension, increased surface coverage of droplets for greater emulsion stability.

Adsorptive removal of pharmaceutical contaminants: Accurate description of tailing breakthrough curves

Fixed bed adsorption is a well-established method used to remove various contaminants, including pharmaceuticals, from aqueous solutions. Mathematical modeling plays a pivotal role in analyzing the dynamic behavior of fixed bed adsorption processes. The classic Bohart–Adams model, dating back over a century, is commonly used to describe fixed bed breakthrough curves. However, it encounters difficulties in effectively interpreting tailing breakthrough curves resulting from the slow approach of the fixed bed to saturation. This study presents an enhanced version of the Bohart–Adams model, specifically tailored to address the challenge of analyzing tailing breakthrough data concerning pharmaceutical contaminant adsorption in fixed bed adsorbers. The new formulation incorporates a conceptual steric hindrance model, proposing that the tailing breakthrough behavior is a consequence of a reduction in the rate of adsorption as surface coverage increases. Through rigorous testing, the new model showcased superior performance compared to the original model, accurately describing the tailing breakthrough curves commonly observed with pharmaceutical contaminants such as diclofenac, sulfamethoxazole, and tetracycline. Additionally, comparative analyses of the new model, a mechanistic model, and the empirical Yan model conclusively demonstrated the superiority of the newly proposed approach. The new Bohart–Adams model can be used to precisely predict breakthrough and exhaustion times or optimize column operating conditions.

Ion solvation as a predictor of lanthanide adsorption structures and energetics in alumina nanopores

Adsorption reactions at solid-water interfaces define elemental fate and transport and enable contaminant clean-up, water purification, and chemical separations. For nanoparticles and nanopores, nanoconfinement may lead to unexpected and hard-to-predict products and energetics of adsorption, compared to analogous unconfined surfaces. Here we use X-ray absorption fine structure spectroscopy and operando flow microcalorimetry to determine nanoconfinement effects on the energetics and local coordination environment of trivalent lanthanides adsorbed on Al2O3 surfaces. We show that the nanoconfinement effects on adsorption become more pronounced as the hydration free energy, ΔGhydr, of a lanthanide decreases. Neodymium (Nd3+) has the least exothermic ΔGhydr (−3336 kJ·mol−1) and forms mostly outer-sphere complexes on unconfined Al2O3 surfaces but shifts to inner-sphere complexes within the 4 nm Al2O3 pores. Lutetium (Lu3+) has the most exothermic ΔGhydr (−3589 kJ·mol−1) and forms inner-sphere adsorption complexes regardless of whether Al2O3 surfaces are nanoconfined. Importantly, the energetics of adsorption is exothermic in nanopores only, and becomes endothermic with increasing surface coverage. Changes to the energetics and products of adsorption in nanopores are ion-specific, even within chemically similar trivalent lanthanide series, and can be predicted by considering the hydration energies of adsorbing ions.