Surface Chemistry Parameters Research Articles

Probing Surface Chemistry Effects on Effective Diffusion Coefficients in Hierarchically Porous Media Through Multiscale Simulations

AbstractMultiscale diffusion simulations in a realistic macro‐mesoporosity model of a silica‐based chromatographic bed are performed to study the effect of relevant surface chemistry parameters, namely length and ligand density of surface‐tethered alkyl chains, on effective mesopore and bed diffusion coefficients. Efficient linker schemes enable integration of interfacial dynamics information obtained from molecular dynamics simulations at the single‐mesopore level into the hierarchical porosity and multiscale transport model.

Simulation of CH3OH ice UV photolysis under laboratory conditions

Context. Methanol is the most complex molecule that is securely identified in interstellar ices. It is a key chemical species for understanding chemical complexity in astrophysical environments. Important aspects of the methanol ice photochemistry are still unclear, such as the branching ratios and photodissociation cross sections at different temperatures and irradiation fluxes. Aims. This work aims at a quantitative agreement between laboratory experiments and astrochemical modelling of the CH3OH ice UV photolysis. Ultimately, this work allows us to better understand which processes govern the methanol ice photochemistry present in laboratory experiments. Methods. We used the code ProDiMo to simulate the radiation fields, pressures, and pumping efficiencies characteristic of laboratory measurements. The simulations started with simple chemistry consisting only of methanol ice and helium to mimic the residual gas in the experimental chamber. A surface chemical network enlarged by photodissociation reactions was used to study the chemical reactions within the ice. Additionally, different surface chemistry parameters such as surface competition, tunnelling, thermal diffusion, and reactive desorption were adopted to check those that reproduce the experimental results. Results. The chemical models with the code ProDiMo that include surface chemistry parameters can reproduce the methanol ice destruction via UV photodissociation at temperatures of 20, 30, 50, and 70 K as observed in the experiments. We also note that the results are sensitive to different branching ratios after photolysis and to the mechanisms of reactive desorption. In the simulations of a molecular cloud at 20 K, we observed an increase in the methanol gas abundance of one order of magnitude, with a similar decrease in the solid-phase abundance. Conclusions. Comprehensive astrochemical models provide new insights into laboratory experiments as the quantitative understanding of the processes that govern the reactions within the ice. Ultimately, these insights can help us to better interpret astronomical observations.

Machine learning model for understanding laser superhydrophobic surface functionalization

A general machine learning (ML) framework of surface wetting is proposed by considering a broad range of factors, including solid surface topography, solid surface chemistry, liquid properties, and environmental conditions. In particular, an XGBoost-based ML model is demonstrated for learning the surface wetting behaviors processed by a laser-based surface functionalization process, namely nanosecond laser-based high-throughput surface nanostructuring (nHSN). This is the first known attempt to apply machine learning to surface wetting by considering both surface topography and surface chemistry properties. Novel microscale and nanoscale topography parameters viz., roughness, fractal, entropy, feature periodicity are defined with suitable computer algorithms to comprehensively describe the surface topography. A novel set of surface chemistry parameters such as polarity, volume, and amount of functional groups are also used as the machine learning model input. Upon analyzing the importance of each parameter for the nHSN process, surface chemistry shows the greatest importance in determination of surface wettability, while surface morphology also plays a part in influencing the wettability. • A machine learning model is firstly proposed for surface wettability considering both topography and chemistry. • Fractal dimension, 2D-entropy, and periodicity are used to describe surface morphology. • Polarity and functional groups are used to describe surface chemistry. • The results showed that the surface chemistry is the dominant feature while surface topography plays a supportive role.

Grafting of amino groups onto carbon fibers by bromination followed by ammonolysis

Because of the low content of chelating groups onto carbon fibers (CFs), their adsorptive parameters are poor, and this has negative effects on their applications as lightweight sorbents. In this work, we established a modification method to incorporate amine groups into carbon fiber surfaces by bromination followed by ammonolysis to create an interfacial layer which can adsorb heavy metal ions from solutions. The changed chemical composition, surface morphology, and thermal stability were investigated. Thermoprogrammed desorption mass-spectrometry and thermal analysis showed thermal transformation and interplay between forms of the grafted bromine groups of 0.5 mmol/g and the resulting amino groups of 0.44–0.56 mmol/g. After grafting, the surface chemistry parameters were improved due to the covalent bonding and grafting of the amine groups as interface modifier. Scanning electron microscopy observation also confirmed that the surface morphology maintains the same, without impairment of fiber properties. This work is therefore a beneficial approach towards enhancing the adsorption parameters by controlling the interface layer of CFs.

A technique to determine ore variability in a sulphide ore

Ore variability is a big challenge for mineral processing operations, especially in the flotation of complex polymetallic sulphide ores. Processing and blending strategies are determined mostly based on chemical and mineralogical characterization. However, surface characteristics of sulphide minerals is an equally important parameter affecting flotation performance. Changes in surface characteristics of sulphide minerals are usually studied at laboratory scale by using sophisticated equipment, such as ToFSIMs, XPS, etc. In this paper, use of Oxidation Index methodology based on the EDTA extraction technique was evaluated for determination of the presence of secondary copper minerals and surface oxidation of sulphide minerals using a low grade VMS ore deposit from Turkey. These two surface chemistry parameters are known to influence flotation performance significantly, particularly in the copper flotation stage. Therefore, ore variability across the entire ore deposit was evaluated using the relationship between Oxidation Index and flotation performance. The results showed that this methodology can potentially be used as a practical and cost effective method for mapping an ore body regarding variations in surface chemistry of sulphide minerals, prediction of flotation recoveries and selectivity.

Aquatic behavior and toxicity of polystyrene nanoplastic particles with different functional groups: Complex roles of pH, dissolved organic carbon and divalent cations

Herein we systematically examined the roles of water chemistry (pH, dissolved organic carbon (DOC), and divalent cations) and particle surface functionality that control the aqueous stability, aggregation, and toxicity of engineered nanoplastic particles in simulated natural environmental conditions. Model polystyrene latex nanoparticles (PLNPs) with three different functional groups, namely unmodified (uPLNPs), amine-modified (aPLNPs), and carboxyl-modified (cPLNPs), were investigated. Results indicate that the presence of only DOC increased the surface charge and exhibited negligible effects on the size distribution of the PLNPs in aqueous suspensions. The presence of the divalent cations (Ca2+ and Mg2+) was observed to decrease the surface charge and increase the size of the PLNPs. The coexistence of DOC and the divalent cations enhanced the extent of aggregation of the PLNPs in the water columns. The surface modification and pH were sensitive factors influencing the stability of PLNPs during long-term suspension when DOC and the divalent cations coexisted. Direct visual further testified the conclusions on the combined effects of solution and surface chemistry parameters. Furthermore, in situ transmission electron microscope observations revealed that the enhancement of PLNP aggregation in the presence of DOC and the divalent cation was caused by bridge formation. Toxicity test indicated the PLNPs exhibited acute toxicity and physical damage to Daphnia magna. The more complex the solution conditions, the more toxicity the aPLNPs and cPLNPs. Analysis of mode of toxic action implied that the PLNPs mainly caused the accumulation of oxidative damage to the gut of D. magna.

An assessment of applicability of existing approaches to predicting the bioaccumulation of conventional substances in nanomaterials.

The experimental determination of bioaccumulation is challenging, and a number of approaches have been developed for its prediction. It is important to assess the applicability of these predictive approaches to nanomaterials (NMs), which have been shown to bioaccumulate. The octanol/water partition coefficient (KOW ) may not be applicable to some NMs that are not found in either the octanol or water phases but rather are found at the interface. Thus the KOW values obtained for certain NMs are shown not to correlate well with the experimentally determined bioaccumulation. Implementation of quantitative structure-activity relationships (QSARs) for NMs is also challenging because the bioaccumulation of NMs depends on nano-specific properties such as shape, size, and surface area. Thus there is a need to develop new QSAR models based on these new nanodescriptors; current efforts appear to focus on digital processing of NM images as well as the conversion of surface chemistry parameters into adsorption indices. Water solubility can be used as a screening tool for the exclusion of NMs with short half-lives. Adaptation of fugacity/aquivalence models, which include physicochemical properties, may give some insights into the bioaccumulation potential of NMs, especially with the addition of a biota component. The use of kinetic models, including physiologically based pharmacokinetic models, appears to be the most suitable approach for predicting bioaccumulation of NMs. Furthermore, because bioaccumulation of NMs depends on a number of biotic and abiotic factors, it is important to take these factors into account when one is modeling bioaccumulation and interpreting bioaccumulation results. Environ Toxicol Chem 2018;37:2972-2988. © 2018 SETAC.

Development of a turbulent flotation model from first principles and its validation

A first principle flotation model has been derived from the basic mechanisms involved in flotation. It consists of a set of analytical equations for various sub-processes such as bubble generation, bubble-particle collision, attachment, detachment, bubble coarsening, and froth phase recovery. A computer simulator based on the model can predict flotation from both hydrodynamic and surface chemistry parameters such as bubble size, particle size, energy dissipation rate, ζ-potentials, contact angles, etc. The model predictions are in good agreement with the flotation results obtained in both laboratory and pilot-scale tests. The model-based simulator can be used to design and diagnose flotation circuits. Typical input parameters include the size-by-class mineralogical composition of a feed, flotation cell characteristics, flow rates, and the types and dosages of reagents.

Assessment of the surface chemistry of carbon blacks by TGA-MS, XPS and inverse gas chromatography using statistical chemometric analysis

Abstract Four carbon blacks with different specific surface areas and surface chemistries (C32, C71, C159 and C178) were analyzed by transmission electron microscopy (TEM) and nitrogen adsorption isotherms at 77 K. Their surface chemistries were analyzed by X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis coupled with mass spectrometry (TGA-MS) and inverse gas chromatography (IGC). The carbon blacks contained 2.7–5.8 wt% volatiles corresponding to OH, C O, C O and COO groups. The surface chemistry parameters obtained with the different experimental techniques were inter-related by using chemometric statistical analysis tools. The application of this methodology showed that the carbon blacks with lower specific surface area (C32 and C71) had basic character (electron donor) mainly due to C O and C O groups, whereas the carbon black with the highest specific surface area (C178) showed acidic character (acceptor electron) due to its high content of OH groups. Moreover, the total surface energy and the dispersive component of the surface energy of the carbon blacks increased with the increase of their specific surface area. In general the specific interactions of the carbon blacks also increased with the increase of their specific surface area although C71 is exceptional due to higher oxygen content corresponding to C O groups.

Preparation of dealuminated faujasites for adsorption of volatile organic compounds

A series of dealuminatead faujasitic zeolites, obtained from the ammonium form of Y zeolite, was prepared by two different methodologies: a relatively common self-steaming method, where temperatures in the range 813 to 1093 K were used, and a less well studied solid-state dealumination method using ammonium hexafluorosilicate, which employed a lower temperature (453 K) than those used in the self-steaming method. It was possible to obtain samples by solid-state dealumination with both high levels of dealumination and good crystallinity. Textural and surface chemistry parameters, such as the micropore volume and the hydrophobic character of the surface, respectively, were correlated with the extent of dealumination. The adsorption isotherms of two selected volatile organic compounds (VOCs), one oxygenated (methyl ethyl ketone) and the other chlorinated (1,1,1-trichloroethane), were measured at 298 K by the gravimetric method. For one of the samples obtained by solid-state dealumination in particular, the adsorption isotherms of the studied VOCs presented adequate characteristics for the adsorption of these molecules, namely significant adsorption capacity and a moderately rectangular shape. This latter aspect can be of importance, for instance, in terms of regeneration of the adsorbent.

Surface effects on pool boiling CHF

The influence of the surface of horizontally and vertically oriented ribbon heaters made of stainless steel 302 or steel 1010 on pool boiling CHF in FC-72 or H2O was studied. The ribbon was 50 mm long, 5 mm high and 76.4μm thick. Surface treatment was performed with different sandpapers and etching in diluted acid. In the centre line average Ra range from 0.02 to 1.5μm, the pool boiling CHF on stainless steel 302 ribbon heaters in FC-72 increased from 87.6 to 115.4kW/m2 and in H2O it increased from 410.8 to 499.7kW/m2, while for steel 1010 ribbon heaters the CHF increased in H2O from 309.7 to 443.9kW/m2. On an etched heater surface, pool boiling CHF in H2O on both stainless steel 302 and steel 1010 increased by 51% with respect to a sanded surface with the same Ra. It appears that a multiparametric heating surface characteristic and the surface chemistry parameters need to be included in the study.

The role of hydrodynamic and surface forces in bubble–particle interaction

In modeling flotation, the process of bubble–particle interaction is usually divided into three subprocesses, including collision, adhesion and detachment. Of these, the hydrodynamics of bubble–particle collision has been studied most extensively by many investigators, and the results are useful for the design and scale-up of flotation cells. The process of adhesion, on the other hand, is least understood because it is essentially controlled by the chemistry of the system, which is complex and difficult to model mathematically. However, it is possible to determine the probability of the bubble–particle adhesion from the induction times that can be measured experimentally under different chemical environments. Furthermore, the new information reported in the literature on the hydrophobic forces of both particles and bubbles allow prediction of adhesion probabilities using various surface chemistry parameters. Consideration of both the hydrodynamic and surface force parameters is essential in predicting flotation rates from first principles.

Surface chemistry parameters in ecological cleanup of oily wastewater

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSurface chemistry parameters in ecological cleanup of oily wastewaterSamuel. KaufmanCite this: Environ. Sci. Technol. 1976, 10, 2, 168–173Publication Date (Print):February 1, 1976Publication History Published online1 May 2002Published inissue 1 February 1976https://doi.org/10.1021/es60113a013RIGHTS & PERMISSIONSArticle Views92Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (664 KB) Get e-Alerts Get e-Alerts