Influence Of Surface Properties Research Articles

Hydrogen peroxide electrosynthesis using commercial carbon blacks as catalysts: the influence of surface properties and adsorption performance

AbstractBACKGROUNDSurface properties and adsorption performance of carbon materials play a crucial role in the electrochemical two‐electron oxygen reduction to produce H2O2. However, there is still a lack of in‐depth research on commercial carbon blacks in this area. Herein, four typical commercial carbon blacks (Acetylene black (AB), Ketjen black EC 600JD, Vulcan XC 72 and Black Pearls 2000) were used as cathode catalysts to generate H2O2. Surface chemistry and pore structure of electrodes of the four carbon blacks were systematically characterized, and their effects on H2O2 adsorption, electrochemical generation and degradation were investigated.RESULTSAmong the four carbon blacks, AB has the highest content of C–O–C/COOH and CO, which are active groups catalyzing the two‐electron oxygen reduction reaction to generate H2O2. AB has the lowest level of defects and highest degree of graphitization, and AB‐modified graphite felt electrode (AB‐Ele) has the largest average pore diameter, smallest specific surface area and smaller charge transfer resistance. H2O2 production using AB‐Ele is the largest and reaches 567.7 mg L−1 at 180 min under a current density of 5 mA cm−2, and only decreases by 17.6% after 10 repeated uses.CONCLUSIONOverall, rich oxygen‐containing functional groups such as C–O–C, COOH and CO, high degree of graphitization, suitable surface area and porosity as well as weak H2O2 adsorption performance are beneficial for the two‐electron oxygen reduction reaction to generate H2O2. AB‐modified graphite felt electrode exhibits good catalytic activity and reusability in H2O2 electrosynthesis, demonstrating promising application prospects. © 2024 Society of Chemical Industry (SCI).

Effects of Common Surface Modifications on the Mechanical Properties of Miniscrews: A Systematic Review

Aim: The objective of this systematic review was to offer quantitative evidence regarding the influence of surface properties on the mechanical stability of miniscrews. Materials and Methods: The comprehensive search strategy involved querying databases, namely PubMed, Web of Science, and Scopus. PRISMA guidelines were followed to determine relevant studies according to specific eligibility criteria. The final search was conducted on 30 August 2023. In this systematic review, in vivo studies published in the English language were included. Results: A total of 364 articles were viewed, and 17 of them were considered for evaluation. Two of the articles are about human studies, while the rest are about animal studies. The number of miniscrew samples ranged between 18 and 144 (totaling 1097 with a mean of 64.52). Among the surface modifications in the articles, the sandblasting with large grit and acid etching (SLA) method was most frequently applied, followed by acid etching in second place. The control groups’ (machined surface) maximum removal torque (MRT) values varied from 2.05 to 50.50 Ncm, while maximum insertion torque (MIT) values varied from 7.23 to 19.25 Ncm. Conclusions: The development of novel applications to improve the surface properties and survival rates of miniscrews is ongoing. In future studies, emerging surface modifications should be evaluated clinically, taking into account their cost and associated harm to the environment.

Aluminium dross waste utilization for phosphate removal and recovery from aqueous environment: Operational feasibility development

The need to minimize eutrophication in water bodies and the shortage of phosphate rock reserves has stimulated the search for sequestration and recovery of phosphate from alternative sources, including wastewater. In this study, aluminium dross (AD), a smelting industry waste/by-product, was converted to high-value material by encapsulation in calcium alginate (Ca-Alg) beads, viz. Ca-Alg-AD and utilized for adsorptive/uptake removal and phosphate recovery from an aqueous environment. Encapsulation of AD in alginate beads solves serious operational difficulties of using raw AD material directly due to density difference constraining efficient contact of AD with pollutants present in water and post-treatment recovery of AD material. The phosphate removal was evaluated in both batch and continuous flow operation modes. The batch adsorption study revealed 96.86% phosphate removal from 10 mg L−1 of initial phosphate concentration in 70 min of optimal contact time. Further, the phosphate removal potential of Ca-Alg-AD beads turned out to be independent of solution pH, with an average of 95.93 ± 1.40 % phosphate removal in the 2–9 pH range. The result reflects phosphate adsorption on Ca-Alg-AD beads following a second-order pseudo-kinetic model. Ca-Alg-AD beads-based adsorption followed Freundlich and Langmuir isotherm models. Further, a continuous packed bed column study revealed a total phosphate adsorption capacity of 1.089 mg g−1. The chemical composition, physical stability, and surface properties of Ca-Alg-AD beads were analyzed by means of state-of-the-art analytical techniques, such as Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetry/Differential Thermal Analysis (TG/DTA). These characterization techniques comprehend the mechanism and influence of surface properties and morphology on the phosphate adsorption behaviour, which induce the involvement of multiple mechanisms such as ligand complexation, ion exchange, and electrostatic attraction for phosphate adsorption on Ca-Alg-AD beads.

Experimental investigation of radiative heat propagation in a simplified generic packed bed

A novel test rig for the investigation of radiative heat transfer in packed beds has been developed and is introduced with representative experimental results. The individual components and the calibration are discussed. The generic packed bed is realized in a simplified way by an arrangement of parallel rods, which represent particles in pseudo-2D. In this arrangement, electrically heated rods provide the radiation propagating through the rod array to heat the passive counterparts. A sophisticated temperature-control scheme with a large number of thermocouples and infrared-imaging provides in-depth information about heat transfer in the system. Spectral radiation intensities are determined with a Fourier-transform infrared spectroscopy, which has been modified and validated for this specific application. In order to compare the influence of different surface properties of particles on the heat propagation and surface reflections, rod samples made of stainless steel and magnesium oxide are used. The influence of material properties becomes clearly visible by comparing the high radiation intensities resulting from a stainless steel rod array to the same geometry built from magnesium oxide rods. In addition, the influence of the surface properties is particularly evident in the infrared images since the reflections are significantly higher for the stainless steel samples than for the magnesium oxide samples. The experimental results in the current work demonstrate the ability of the test rig to provide data with a well-defined accuracy as a validation base for numerical radiation simulations in packed beds.

Observation of Capillary Condensation and Pattern Bending Phenomena in Si Nanopillars Using <i>In Situ</i> TEM

Capillary condensation, a ubiquitous phenomenon involving the heterogeneous nucleation of liquid droplets, has significant implications in various industrial, biological, and atmospheric processes. Strong capillary forces induced by highly curved menisci of condensates can have potentially significant impact on the structural integrity and functionality of nanodevices. While the influence of surface properties on the nucleation and growth of water droplets has been extensively studied at microscale, our understanding of water condensation at the nanoscale remains limited due to experimental challenges in imaging liquids at nanometer scales. In this study, we employ in situ liquid phase TEM imaging and for the first time present real-time observations of water condensation dynamics on arrays of vertical silicon (Si) nanopillars. Experimental and simulation results show that nucleation of water droplets occurs at the edges of the nanopillars and substrate, followed by the growth of an interfacial layer resembling a corona around the nanopillars. Subsequently, the formation of bridges between adjacent growing coronas leads to the development of symmetric and asymmetric bridged nanopillar geometries. Importantly, we find that the formation of bridges can induce bending and collapse of the nanopillars, depending on their aspect ratios. Overall, this study provides valuable insights into the nanoscale dynamics of capillary condensation and paves the way for advanced engineering applications and optimization of various technological processes.

Study on the Effect of Surface Properties of Non-Metallic Materials on the Growth Mechanism of Crystallization Fouling

In order to alleviate the serious problem of scaling in oilfield water injection pipelines, we developed a scale collection device and applied it in the field based on the idea to “change passive descaling to active descaling”, but the effect is not stable, so we need to improve the descaling effect. Firstly, this paper analyzed the effect of surface physical properties of eight non-metallic materials on CaCO3 scale growth and their mechanisms through shear experiments. Then, the influence of surface properties (roughness, contact angle, surface energy) on the scale growth characteristics was investigated. Finally, the influence of material surface properties on the friction coefficient was studied by a cyclic experiment. The results showed that except for PTFE (polytetrafluoroethylene), the fouling amount of the other seven materials changed abruptly at 18 h, and the maximum fouling amount of FRP was 2.05 g/m3. It was found by scanning electron microscopy that the fouling particles on the surface of FRP were interconnected and presented in the form of flakes, which was related to the larger surface wettability, surface energy, and roughness. At the same time, the surface properties of the material have a certain relationship with the friction coefficient, and the influence of the contact angle on the friction coefficient is greater than the surface energy and roughness.

Influence of surface properties on the adhesion of bacteria onto different casings

Bacteria adhere to the surfaces of sausage casing and form biofilms, which causes food spoilage and quality deterioration. However, bacterial adhesion to the casing surfaces has not received enough attention and has not been extensively studied. In this study, the effect of the physicochemical properties of casing surfaces on bacterial initial adhesion were investigated with Leuconostoc mesenteroides as model bacteria. The adhesion of Leuconostoc mesenteroides onto 5 types of casings were systematically investigated, including animal casings, collagen casings, cellulose casings, fiber casings, and nylon casings, which are the most frequently encountered casings in sausage processing. It was found that the number of viable cells on the casings following the trend as: animal casings > collagen casings > fiber casings > cellulose casings > nylon casings after 4 h of incubation time. This phenomenon might be due to the different physicochemical properties of the different casings. Therefore, physicochemical factors, including zeta potential, hydrophobicity and roughness of casings, zeta potential and hydrophobicity of Leuconostoc mesenteroides, were further characterized. In terms of hydrophobic interactions, the results showed that the number of bacteria attached to the casings did not conform to the trend of hydrophobic interaction. In terms of electrostatic interactions, the results showed that the number of bacteria attached to the casings did not conform to the trend of hydrophobic interaction. The casings with different surface roughnesses in a range of 1.67–20.83 μm, the variation of bacterial adhesion quantity was in good agreement with the variation trend of casing roughness, the result showed that the surface roughness was the key factor dominating the bacterial adhesion rate compared with the surface hydrophobicity and zeta potential. The results give new insights to explore the mechanism of bacterial adhesion on casings and prevent sausage spoilage.

Influence of Surface Properties and Microbial Growth Media on Antibacterial Action of ZnO

Nano- and microscale ZnO demonstrate robust antibacterial action, although the driving mechanisms remain undetermined. In this study for commercial ZnO nano-powders and home-grown ZnO microparticles of varying morphologies we probe the response to bacterial growth media in isolation and with Staphylococcus aureus bacteria. ZnO microparticles are synthesized via a controllable hydrothermal method and subjected to biological assays with varying microbial environments. Changes in the optoelectronic, structural and chemical properties of these crystals before and after such exposure are characterized utilizing temperature-dependent photoluminescence spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. This is done to evaluate the impact of surface-surface interactions in antibacterial assays and the role ZnO surface and morphological properties play in these processes. In our experiments various bacterial environments are employed to elucidate the effects of media interactions on the cytotoxic efficacy of ZnO. In particular, minimum inhibitory concentration assays with Staphylococcus aureus reveal that microscale particles exhibit antibacterial efficacy comparable to that of the nano-powders, indicating that intra-bacterial internalization is not necessary for antimicrobial action. In our studies we determine that the nature of structural and optoelectronic changes in ZnO depends on both the media type and the presence (or absence) of bacteria in these media. Further evidence is provided to support significant cytotoxicity in the absence of particle internalization in bacteria, further highlighting the role of surface and media interactions in this process.

Hydrazine modified g-C3N4 with enhanced photocatalytic activity for degradation of indigo carmine

Polymeric graphitic carbon nitride (g-C3N4) was obtained from urea and modified by heat polymerization at 550 °C in the presence of hydrazine as a modifier agent. The influence of in-situ generated NH3 by hydrazine decomposition at different contents (0.5, 1, 1.5, and 2 mL) on the physicochemical properties and surface properties (water contact angle and point of zero charge) of the g-C3N4 were investigated. The modified g-C3N4 were analyzed by X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, Fourier Transform Infrared, water contact angle, surface area, and the point of zero charge. The in-situ generated NH3 induced an evolution from nano-flakes to lamellar plate morphology depending on stacked interplanar. The influence of surface properties on the photocatalytic response of the unmodified and modified g-C3N4 was tested in the photodegradation of indigo carmine dye at pH = 3.5 and 6.5 solutions under blue LEDs light. The photostability of the samples was tested after 4 cycles of reaction. The properties (surface area (SA); water contact angle (WCA), and optical gap) influence the photocatalytic response, which was summarized in a single parameter defined as SA/(WCA*gap). The maximum value of this product match with results obtained for the most active photocatalyst (U-Hz1).

How Interfacial Properties Affect Adhesion: An Analysis from the Interactions between Microalgal Cells and Solid Substrates.

Microalgal biofilm, a stable community of many algal cells attached to a solid substrate, plays a significant role in the efficient accumulation of renewable energy feedstocks, wastewater treatment, and carbon reduction. The adhesion tendency of microalgal cells on solid substrates is the basis for controlling the formation and development of microalgal biofilm. To promote the adhesion of microalgal cells on solid substrates, it is necessary to clarify which surface properties have to be changed in the most critical factors affecting the adhesion. However, there have been few systematic discussions on what surface properties influence the adhesion tendency of algal cells on solid substrates. In this study, the essential principle of microalgal cell adhesion onto solid substrates was explored from the perspective of the interaction energy between microalgal cells and solid substrates. The influence of surface properties between microalgal cells and solid substrates on interaction energies was discussed via extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) theory and a sensitivity analysis. The results showed that surface properties, including surface potential (ξ) and surface free energy components, significantly affect the adhesion tendency of microalgal cells on different solid substrates. When the solid surface possesses positive charges (ξ > 0), reducing ξ or the electron donor components of the solid substrate (γs-) is an effective measure to promote microalgal cell adhesion onto the solid substrate. When the solid surface possesses negative charges (ξ < 0), an increase in either γs- or the absolute value of ξ should be avoided in the process of microalgae adhesion. Overall, this research provides a direction for the selection of solid substrates and a direction for surface modification to facilitate the adhesion tendency of microalgal cells on solid substrates under different scenarios.

Influence of surface properties on the dynamics of fluid flow

In this paper, we study how the fluid flow near the surface of a monocrystalline body is affected by the surface properties due to atom-surface scattering. We propose a toy model for this system by parameterizing the surface with a periodic function of the tangential position. This allows us to derive the velocity probability density function in the Knudsen layer and determine statistical averages of fluid velocity and stress tensor components in the region of interest. The results of this analysis provide a potentially more fundamental and accurate explanation for empirically observed phenomena such as the no-slip boundary condition, boundary layer formation, and the onset of hydrodynamic instability.

Shape Engineering of TiO2 Microrobots for "On-the-Fly" Optical Brake.

Hybrid microrobots have recently attracted attention due to their ability to combine different energy sources and/or external stimuli for propulsion and performing desired tasks. Despite progresses in the past, on-demand speed modulation for hybrid microrobots has not been analyzed in detail. Herein, the influence of surface properties and crystallite size on the propulsion mechanism of Pt/TiO2 chemical/light-driven hybrid microrobots is investigated. The morphology of urchin-like Pt/TiO2 microrobots leads to "on-the-fly" optical brake behavior under UV irradiation. In contrast, smooth Pt/TiO2 microrobots demonstrate accelerated motion in the same conditions. The comparison between two types of microrobots also indicates the significance of a high surface area and a high crystallite size to increase their speed. The results demonstrate the profound impact of surface features for next-generation smart micro/nanorobots with on-demand reaction capability in dynamically changing environments.

Alteration of freezing paradigms of an impact water droplet on different cold surfaces

The influence of surface properties on the dynamics and freezing of an impact water droplet is investigated under various impact velocities and surface temperatures. Three distinct icing paradigms are found, namely the widely observed Central-Pointy Icing paradigm (CPI), the annular paradigm with Exterior Freezing front First (EFF), and the annular paradigm with Interior Freezing front First (IFF). High impact velocities and low surface temperatures are beneficial to the IFF icing paradigm. Upon decreasing the impact velocity and/or increasing the surface temperature, the IFF paradigm transits to EFF and ultimately to CPI. The interior freezing front occurring prior to the exterior one is mainly attributed to the small difference of the thickness between the central and peripheral liquid, and the large temperature difference between the droplet and liquid-substrate interface. Raising the impact velocity and surface wettability enhances droplet spreading, resulting in a small thickness difference. The liquid-substrate interface temperature is collectively determined by surface temperature, density, thermal conductivity and specific heat capacity of the solid surface. A freezing paradigm map described by the dimensionless temperature and the maximum spreading diameter is proposed to evaluate the conditions under which one of the three distinct freezing paradigms appears. A large spreading area and a low liquid-substrate interface temperature are prerequisites for the emergence of IFF paradigm.

The influence of RO membrane surface properties on surfactant fouling in radioactive wastewater treatment

Reverse osmosis (RO) has been shown to be an efficient treatment method for radioactive wastewater, which has been employed in nuclear power plants. However, the fouling on RO membrane surface should be solved to fabricate modified RO membranes with selective and fouling-resistant surface, which is essential for the further widespread application of RO. To provide fundamental insights into fouling control methods, the influence of surface properties on surfactant fouling was investigated with modified RO membranes. The results showed that surfactant fouling reduced the flux of RO membranes by 35 %–75 %. The interfacial free energies associated with the surfactants and RO membranes surface were calculated by XDLVO theory to explain surfactant fouling mechanisms. The interfacial free energies associated with CTAB and RO membrane surface increased from 3.18 to 41.22 and 69.62 mJ m−2 and SDBS increased from 20.21 to 34.07 and 43.97 mJ m−2, Tween 80 increased from -2.63 to 3.98 and 9.61 mJ m−2 with PEI and EPTAC grafting. The results indicated that the changes of interfacial free energies were mainly caused by the changes of membrane hydrophilicity and surface charge. Fabricating RO membrane with hydrophilic and neutrally charged surface was potential for improving all kinds of surfactants resistant capability. Besides, surfactant fouling had great influence on membrane permeability. The changes of radioactive nuclide rejections were mainly caused by the changes of membrane surface charge while the increase of boron rejection was attributed to the rise of membrane surface steric-hindrance. Therefore, the membrane hydrophilicity and surface charge should be carefully considered in radioactive wastewater containing surfactants treatment.

Biofilms on Restorative Materials.

Biofilm formation depends on many factors, one of them being the surface (substrate) on which the biofilm is formed, and dental restorative materials are such substrates. Biofilms play a crucial role for caries formation and inflammation of gingival, periodontal, or mucosal tissues next to restorations. Even general health problems such as systemic infections in immunocompromised patients may result from biofilms on dental materials (e.g., on dentures). Furthermore, biofilms may change material or surface properties. Biofilms on restorative materials have been investigated by several in vitro, in situ, and in vivo methods measuring a large number of different endpoints. Basically, datasets obtained from different methodological approaches are most suitable for final assessments. While surface properties like wettability or surface free energy (SFE) influence biofilm formation to a certain extent, the most relevant surface properties are material roughness followed by surface chemistry. The pellicle, which is formed rapidly on restorations after in vivo exposure, masks or levels off the influence of surface properties like wettability or SFE on biofilm formation. The prevention of biofilm formation is mainly based on general oral hygiene regimens. Furthermore, optimal polishing of restorative materials is instrumental. Several antimicrobial substances have been incorporated into restorative materials, which act by being released or as surface repellents. However, the optimal biofilm-preventive restorative material has not been found so far. New approaches in this context should aim at: (1) better understanding the role of the biofilm matrix (extracellular polymeric substance), and (2) implementing ecology-based approaches for the modification of dysbiotic disease-associated biofilms.

The Influence of Time-dependent Surface Properties on Sprint Running Performance between Male and Female Athletes

Background: The body of research on field based player-surface interaction consists of some contradictory findings and the comparison of male and female physiological responses on different surfaces is limited. Objective: The study investigates the influence of surface properties on sprint running before and after completing a muscle fatiguing intervention. Methodology: Muscle activity was recorded using surface electromyography (EMG). The vastus medialis (VM), biceps femoris (BF), medial head of the gastrocnemius (MG), and the tibialis anterior (TA) sites were selected for analysis. The mechanical properties (MPs) of each field were shown to be different using ASTM F-3189 protocol. Results: A statistically significant three-way repeated measures ANOVA interaction between field properties, sprint trial and muscle groups was determined, F(3,36) = 10.82, p = .006, ηρ2 = .474. Further analyses revealed an interaction effect between field properties and sprint trial, F(1,12) = 26.57, p = .001, ηρ2 = .689, between muscle groups and field properties F(1,12) = 8.78, p = .012, ηρ2 = .422 and between muscle group and sprint trial F(1,12) = 7.29, p = .019, ηρ2 = .378. In addition, pre-intervention mean sprint time was less on the field possessing more energy return by 9.1%. Post-intervention sprint test results show a significant difference for BF peak muscle activity on the field displaying greater force attenuation. Conclusion: Both pre and post intervention sprint results suggest time-dependent properties associated with a sport field could potentially influence muscle activation patterns differently for males and females.

Effects of Surface Properties on Gastrocnemius Medialis and Vastus Lateralis Fascicle Mechanics During Maximal Countermovement Jumping.

Interactions between human movement and surfaces have previously been studied to understand the influence of surface properties on the mechanics and energetics of jumping. However, little is known about the muscle-tendon unit (MTU) mechanics associated with muscle activity and leg adjustments induced by different surfaces during this movement. This study aimed to examine the effects of three surfaces with different properties (artificial turf, hybrid turf, and athletic track) on the muscle mechanics and muscle excitation of the gastrocnemius medialis (GM) and vastus lateralis (VL) during maximal countermovement jumping (CMJ). Twelve participants performed maximal CMJs on the three sport surfaces. GM and VL muscle fascicles were simultaneously imaged using two ultrafast ultrasound systems (500 Hz). MTUs lengths were determined based on anthropometric models and two-dimensional joint kinematics. Surface electromyography (EMG) was used to record GM and VL muscle activity. Surface mechanical testing revealed systematic differences in surface mechanical properties (P = 0.006, η2: 0.26–0.32, large). Specifically, the highest force reduction and vertical deformation values have been observed on artificial turf (65 ± 2% and 9.0 ± 0.3 mm, respectively), while athletic track exhibited the lowest force reduction and vertical deformation values (28 ± 1% and 2.1 ± 0.1 mm, respectively) and the highest energy restitution (65 ± 1%). We observed no significant difference in CMJ performance between the three surfaces (∼35–36 cm, P = 0.66). GM and VL fascicle shortening (P = 0.90 and P = 0.94, respectively) and shortening velocity (P = 0.13 and P = 0.65, respectively) were also unaffected by the type of surface. However, when jumping from greater deformable surface, both GM muscle activity (P = 0.022, η2 = 0.18, large) and peak shortening velocity of GM MTU (P = 0.042, η2 = 0.10, medium) increased during the push-off phase. This resulted in a greater peak plantar flexion velocity late in the jump (P = 0.027, η2 = 0.13, medium). Our findings suggest that maximal vertical jumping tasks in humans is not affected by common sport surfaces with different mechanical properties. However, internal regulatory mechanisms exist to compensate for differences in surface properties.

Influence of surface properties on electro‐chemical supercapacitors utilizing Callerya atropurpurea pod derived porous nanocarbons: Structure property relationship between porous structures to energy storage devices

AbstractSurface properties always play a dominant role in the energy storage devices. Understanding the surface phenomena is the key to tune the energy storage device using biowaste based porous nano carbons. Here, Callerya atropurpurea pod derived peculiar porous nanocarbons are synthesized by pyrolysis at different temperatures without any synthetic templates approach. Elaborate analysis of surface textures on the effect of pore size, volume and specific surface area on specific capacitance and frequency response behavior of nanocarbons were studied in detail. Electrochemical characterizations establish the mutuality of porosity and microtextural properties of nanocarbons with specific capacitance. The electrochemical characterization of the novel materials as supercapacitor electrode shows a high specific capacitance of 326.54 F g−1 at 0.25 A g−1 in 1.0 M KOH. A practical symmetric supercapacitor device is fabricated with a specific capacitance of 86.38 F g−1 at 0.1 A g−1, and high energy density of 27.0 Wh kg−1. This symmetric supercapacitor also possesses outstanding capacitance retention of 92.16% for 5000 charge discharge cycles and also stability of 97.17%, after voltage holding at the maximum voltage for 100 hours. Present manuscript gives the strong evidence for structure‐property relationships so that one can tune the energy storage devices effectively.

Influence of surface properties and antecedent environmental conditions on particulate-associated metals in surface runoff

Particulate-associated trace metals have been regarded as an important pollution source for urban surface runoff. Cd, Pb, Cu, Zn and total solids (TS) washed off two different surfaces (low-elevated facade and road surfaces) under two kinds of antecedent environmental conditions (dry and snow-melting) were determined in this study. Wet-vacuuming sweeping (WVS) and surface washing (SW) methods, representing the maximum pollution potential and common rainfall-induced wash-off condition respectively, were used to collect the particulate matters. The result shows that the wash-off concentrations of trace metals were found in the order of Cd (2.28 ± 2.08 μg/l) < Pb (435.85 ± 412.61 μg/l) < Cu (0.93 ± 0.61 mg/l) < Zn (2.52 ± 2.30 mg/l). The snow-melting process had a considerable influence on the wash-off concentrations of the trace metals on both road and facade surfaces. It reduced >38% and >79% of metals and TS concentrations in the facade surface and road surface runoff respectively. The wash-off concentrations of Cd, Cu, and Zn on the road surface 45–780% higher than those on the facade surfaces. The sensitivity analysis based on the Bayesian network indicates that the wash-off concentrations of metals were mainly dependent on the antecedent environmental conditions or the surface properties while the sampling methods had a minor influence. Therefore, to accurately model the pollutant migration in the surface runoff requires an improving method considering different surfaces and antecedent environment conditions.

A surface characterization platform approach to study Flowability of food powders

The surface properties of powders used in beverages have been investigated using IGC (Inverse Gas Chromatography) to assess surface energy and interactions, and X-Ray Photoelectron Spectroscopy (XPS) to evaluate elemental surface composition. The influence of surface properties on powder flowability was studied. The physical attributes of the powders were also determined in the study, and flow properties were determined using a powder rheometer and a rotating drum with image analysis. Five coffee powder samples, generated by three different processes (spray-drying, freeze-drying and milling) and three cocoa beverage powders (agglomerated and simple mixed) were used for this study. The data showed that the differences observed at the surface are detectable by both techniques, IGC and XPS. The results suggest that flow may be inhibited in powders with higher levels of hydrophobic functional groups exposed at the surface. The results also indicate that while powder flow is influenced by physical attributes such as particle size distribution, a major factor is that of the chemical composition at the surface, which in turn has a direct effect on interparticle cohesiveness. We present an assessment platform, geared toward understanding bulk powder behavior, based on the surface techniques, from a thermodynamic (IGC), spectroscopy/structural (XPS) and visualization (SEM) approaches to optimize process and product development.