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This paper presents a detailed study of a water adlayer adsorbed on Pt(111) and Rh(111) surfaces using periodic density functional theory methods. The interaction between the metal surface and the water molecules is assessed from molecular dynamics simulation data and single point electronic structure calculations of selected configurations. It is argued that the electron bands around the Fermi level of the metal substrate extend over the water adlayer. As a consequence in the presence of the water layer the surface as a whole still maintains its metallic conductivity—a result of a crucial importance for understanding the process of electron transfer through the water/metal interface and electrochemical reactions in particular. Our results also indicate that there exists a weak bond between the hydrogen of the water and the Rh metal atoms as opposed to the widespread (classical) models based on purely repulsive interaction. This suggests that the commonly used classical interactions potentials adopted for large scale molecular dynamics simulations of water/metal interfaces may need revision. Two adsorption models of water on transition metals with the OH bonds pointing towards or away of the surface are also examined. It is shown that due to the very close values of their adsorption energies one should consider the real structure of water on the surface as a mixture of these simple “up” and “down” models. A model for the structure of the adsorbed water layer on Rh(111) is proposed in terms of statistical averages from molecular dynamics simulations. © 2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract The development of an adsorbent material by 3D printing technology with high CO 2 adsorption capacity and electrical conductivity is presented for application in Electric Swing Adsorption process. The adsorbent is composed by zeolite 13X, activated carbon and binder. The prepared ink was characterized in order to determine its rheological properties. Two honeycomb monoliths, one with 30 × 30 × 43 mm3 and another one with 30 × 28 × 10 mm3 were printed. Textural characterization was performed by several techniques, including CO 2 adsorption at 273 K. A high CO 2 adsorption capacity of 3.49 mol/kg was obtained for the 3D-printed monolith at 0.15 bar and 273 K. Mechanical strength of the material was evaluated in a piece with 10 × 10 × 4 mm3. A value of 5.0 MPa was obtained. Heating of the material was tested by Joule effect through an electric current passage in the monolith, which presented a resistivity of 0.28 Ωm. An increase of temperature of about 80 K was achieved in 180 s, with a power consumption of 3.25 W. An adsorption quantity of CO 2 of 1.45 mol/kg (at 0.09 bar and 303 K) was obtained by adsorption equilibrium isotherms measurements. These experiments demonstrated that the printed material is suitable for Electric Swing Adsorption processes applied for CO 2 capture. Graphical abstract Image 1 Highlights • 3D-Printed honeycomb monolith with 43 mm of height was successfully developed. • CO 2 adsorption isotherms demonstrated a high adsorption capacity. • A power of 3.25 W for 180 seconds is needed to increase the temperature 80 K. • 3D-printed adsorbent can be used in ESA process due to the electrical properties. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen-doped mesoporous carbon (N-MC) modified glassy carbon electrode (GCE) with high electrocatalytic activity is presented for highly sensitive determination of capsaicin. Due to its moderate specific surface area (151 m2 g−1) and uniform mesostructure (3.9 nm), the N-MC/GCE enhances the adsorption kinetics of capsaicin on the electrode surface via π-π interaction between capsaicin and N-MC. Linear Sweep Voltammetry (LSV) shows significant enhancement of the oxidation peak current due to its good conductivity and excellent electrocatalytic activity. Under optimal conditions, the electrochemical sensor shows a remarkably low detection limit of 0.46 μM (S/N = 3) with a wide linear range of capsaicin from 1-10 μM and 10–40 μM. Finally, the modified electrode was successfully applied to determination of capsaicin in chili peppers with an acceptable recovery range of 82–120%. Graphical abstract Image 1 Highlights • The N-doped mesoporous carbon from PANI exhibits superior capsaicin detection. • High surface area and uniform mesostructure enhances the adsorption of capsaicin. • Graphitic-N is important in sensitive and selective determination of capsaicin. • The N-MC offers an electrochemical sensor without complicated sample preparation. [ABSTRACT FROM AUTHOR]

Abstract A unique set of 6 polar adsorptives of relatively large dipole moment and of increasing kinetic diameter were used to probe pore volumes available and their mechanism of adsorption on a well-characterised microporous carbon. Multiple adsorption isotherm measurements were made and repeatable results with relatively small standard deviations in amount adsorbed at low relative pressures were obtained. Inconsistencies were observed between calculated Gurvitsch volumes. Sources of these were analysed and identified as contributions from one or more of: (a) molecular sieve effects; (b) molecular packing effects, and; (c) 2D molecular structure formation due to hydrogen bonding. These inconsistencies were further studied by comparison with pore volumes derived via the Dubinin-Radushkevich (DR) equation. Qualitative analyses of the micropore filling processes were proposed, and substantiated by complementary DR analyses. Although most of the isotherms showed Type I character, recasting the relative pressure axis in logarithmic format highlighted clear differences as contributions from fluid-fluid and fluid-solid interactions during pore filling. Overall, the adsorptives were classified into three groups: (a) polar adsorptives with primarily specific interactions adsorbing as a condensation process over a relatively narrow relative pressure range in a medium and late pressure range (iso -PrOH, MeOH, 2-methyl, 2-butanol, H 2 O); (b) polar adsorptives with potential for non-specific interactions adsorbing as a condensation process over a relatively narrow pressure range in a medium pressure range (pyridine, iso -PrOH, 2-methyl, 2-butanol); and, (c) halogenated adsorptives adsorbing with an S-shaped uptake extending over a broad relative pressure (dichloromethane). Graphical abstract Image 1 Highlights • Six polar molecules with increasing kinetic diameter used as adsorptives. • High-resolution gas/vapour adsorption isotherms including uncertainty in the data. • Pore volumes evaluated via Gurvitsch and DR methods – inconsistencies analysed. • Low pressure isotherms show pore filling dependence on adsorptive size, shape, and polarity. • Pore filling classified into low, intermediate, and high relative pressure ranges. [ABSTRACT FROM AUTHOR]

Abstract The adsorption of S-metolachlor herbicide from aqueous solution by benzenesilica materials was studied. The materials were synthesized with 1,4-bis(triethoxysilyl)benzene as organosilica precursor and Brij 76 and Pluronic P123 as surfactants. Additionally, 1,3,5-triisopropylbenzene (TPB) was used as porogen to produce microporosity. Those materials obtained by Brij-76 and P123 showed well-structured ordering. However, a disordered microporous benzenesilica material was obtained in presence of P123 and TPB. All materials proved to be efficient adsorbents for S-metolachlor. Among them, the material synthesized with Brij 76 showed the highest adsorption capacity due to its ordered structure and, mainly, to its higher proportion of mesopores. Graphical abstract Image 1 Highlights • Benzenesilicas are very efficient adsorbents for the herbicide S-metolachlor. • The removal rate is higher as the pore size increases for periodic mesoporous benzenesilicas. • The maximum adsorption capacity is higher for periodic mesoporous benzenesilicas than for non-ordered benzenesilicas. • The adsorption is physical according to the Dubinin-Raduskevich model. [ABSTRACT FROM AUTHOR]

Abstract To explore the approach for further enhancing the dye removal performance of polydopamine (PDA) coated materials, a novel composite of PDA-kaolin with reduced graphene oxide hybridization (PDA-rGO-kaolin) was synthesized and selected as a model adsorbent for methylene blue (MB) removal. The BET characteristic analysis showed that the introduction of rGO significantly increased the surface area of PDA-kaolin by 3.1 times. A series of comparative experiments on PDA-kaolin and PDA-rGO-kaolin towards MB removal in various conditions were carried out. Adsorption experiment indicated that PDA-rGO-kaolin was more satisfactory for MB removal. Kinetic analysis showed that the adsorption followed a pseudo-second-order kinetic model. The adsorption behavior could be better described by Langmuir isotherm model. Compared with PDA-kaolin, PDA-rGO-kaolin showed higher maximum adsorption capacity towards MB (39.663 mg/g). Furthermore, the adsorption of MB molecules on adsorbents was spontaneous and endothermic process according to thermodynamic experiment. Moreover, PDA-rGO-kaolin showed a good regeneration performance for MB removal. These results show that the introduction of graphene is a feasible and efficient method to improve the adsorption performance of PDA coated kaolin composite. [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA) has caused widespread concern among scholars as a result of its estrogenic toxicity. It exists mainly in natural waters, sediments, and soil, as well as sewage and wastewater sludge. Considering that BPA is a common environmental pollutant that is removed along with chemical oxygen demand (COD), nitrogen, and phosphorus in drainage treatment systems, it is important to research the fate of BPA in sewage treatment systems. In this research, laboratory batch experiments on soil degradation and adsorption were conducted with 14 C-BPA, aiming to discuss the transport and degradation characteristics of BPA in both simulated facilities and a soil trench. Based on the experimental results, the Freundlich model could be applied to fit the isothermal adsorption curve of the BPA in soil. A low mobility characteristic of BPA was discovered. The mineralization rate of BPA was fast and that of the reaction showed small fluctuations. After degradation, 21.3 and 17.7% of the BPA groups (the experimental group treated with ammonia oxidase (AMO) inhibitor and the control group) were converted into 14 CO 2 , respectively. This indicates that the nitrification and degradation of BPA had a certain competitive relationship. Besides, nitrification did not significantly affect the soil residue of BPA. Through the soil trench test, the average removal rate of BPA in the soil trench was 85.5%. 14 CO 2 was discharged via the mineralization of BPA, accounting for 2.5% of the initial input. BPA easily accumulated in the bottom soil of the soil trench. BPA and its metabolites in the effluent accounted for 14.5% of the initial dosage. The residual extractable BPA and its metabolites in the soil accounted for 51.3%, and the remaining part of the unextractable residue represented 19.8% of the initial radioactive dosage. [ABSTRACT FROM AUTHOR]

Dehydration is a critical operation in natural gas conditioning as it reduces the potential for corrosion, hydrate formation and freezing in process equipment and transportation pipelines. Water dew point adjustment is particularly challenging in the remote ultra-deepwater natural gas reserves of the Brazilian Pre-Salt fields due to their very high carbon dioxide contents – from 30% up to 90% in raw natural gas – which is a consequence from the carbonaceous rock of the reservoir structure and long term elevation of carbon dioxide content due to its injection for early enhanced oil recovery. Under this scenario, the study evaluates the impact of the carbon dioxide content of the natural gas on the performance of water dew point via water adsorption on 4 Å Zeolite molecular sieve beds. Process simulation with adsorption simulator Adsim (Aspen Technology, Inc), at varying operation pressures and carbon dioxide contents in raw natural gas, indicated that, although adsorption meets water removal specification in a condensation free operation, the high fugacity of carbon dioxide penalizes the dehydration performance due to probably two facts: (i) higher carbon dioxide fugacity in the humid natural gas imply higher saturation water content in the gas phase, which increases the service of dehydration units; and (ii) higher carbon dioxide fugacity in the humid natural gas establishes a discreet adsorption competition with water resulting in 6.5% increase of adsorbent bed volume for operating pressures of 35 bar or higher. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is one of the important fuel-element materials in high-temperature gas-cooled reactors (HTGRs), and learning the adsorption behavior of radioactive fission products on the SiC surface is essential for source-term analysis in HTGR. In this study, the adsorption behavior of cesium, strontium, silver, and iodine on β-SiC is investigated using first-principle calculations. We find that the interactions between the adatoms and SiC substrate are strong for all four types of nuclides with binding energy of approximately 1–3 eV. These results are confirmed again by analysis of the charge density difference and density of state. Furthermore, the adsorption rates of the four nuclides are obtained, and we explain that these nuclides display significant adsorption rate on the SiC surface but are not easily desorbed, which shows that the solid fission products have difficulty penetrating through the SiC. These results demonstrate that in HTGR, intact SiC could effectively obstruct the diffusion of fission products from the uranium dioxide in tri-isotropic (TRISO) particles to the primary circuit, which are first obtained in a micro perspective. [ABSTRACT FROM AUTHOR]

Present study deals with the fluoride removal from aqueous solution by using hybrid adsorbent fabricated with Mg/Fe composite oxide and alginate via simple blending method. The fluoride adsorption capacity of the resulting hybrid adsorbent was systematically evaluated with batch adsorption experiments in various operation parameters including initial pH, adsorbent dose, co-existing anions, contact time and temperature. The results indicated the hybrid adsorbent kept good adsorption performance for fluoride over a broad pH range and even in the presence of co-existing anions. With adsorbent dose of 10 g/L, 96.6% of fluoride ion can be reduced from aqueous solution of 10 mg/L at natural pH. The adsorption of fluoride onto the adsorbent is found to be a multi-step rate-limiting reaction with exothermic nature and follows pseudo-second order kinetics. Thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) coupled with energy dispersive spectrum (EDS) and Fourier transform-infrared spectroscopy (FT-IR) were employed to characterize the hybrid material and explore the possible adsorption mechanism. It is suggested that ligand exchange and electrostatic interaction played an important role in the process of fluoride adsorption. Regeneration of adsorbent was also conducted, and 83.3% of the original fluoride removal rate was maintained after three regeneration cycles. [ABSTRACT FROM AUTHOR]

We validate a miniaturized pulsed laser source for use in time-domain (TD) diffuse optics, following rigorous and shared protocols for performance assessment of this class of devices. This compact source (12 6 mm2) has been previously developed for range finding applications and is able to provide short, high energy (×100 ps, ×0.5 nJ) optical pulses at up to 1 MHz repetition rate. Here, we start with a basic level laser characterization with an analysis of suitability of this laser for the diffuse optics application. Then, we present a TD optical system using this source and its performances in both recovering optical properties of tissue-mimicking homogeneous phantoms and in detecting localized absorption perturbations. Finally, as a proof of concept of in vivo application, we demonstrate that the system is able to detect hemodynamic changes occurring in the arm of healthy volunteers during a venous occlusion. Squeezing the laser source in a small footprint removes a key technological bottleneck that has hampered so far the realization of a miniaturized TD diffuse optics system, able to compete with already assessed continuous-wave devices in terms of size and cost, but with wider performance potentialities, as demonstrated by research over the last two decades. [ABSTRACT FROM AUTHOR]

Removal and recovery of toxic metals from wastewater by adsorption is an efficient alternative, especially when using uncommon adsorbents. In the present work, silver and copper binary adsorption onto Verde-lodo bentonite was evaluated in static systems. Kinetic studies under different initial metal concentrations and molar fractions were performed. Kinetic models were adjusted to experimental data, and the External mass transfer resistance model (EMTR) presented the best fitting. The binary kinetic assays revealed that copper presents higher adsorption capacity than silver. Higher total concentrations presented an influence on the adsorption process due to increasing competition for active sites. Equilibrium studies were carried out and the results confirmed the preferential copper adsorption in binary solution with silver. Copper ions were better adsorbed at higher temperatures and silver ions at lower temperatures. The maximum adsorption capacities were 0.110 mmol/g for copper at 60 °C and 0.090 mmol/g for silver at 20 °C. Binary equilibrium models were fitted and the Langmuir-Freundlich model best represented the experimental data. The comparison between Verde-lodo clay characterization, prior and post adsorption, indicated that the process caused no significant changes in the morphology, crystal structure, functional groups and thermal stability of the material. [ABSTRACT FROM AUTHOR]

The spatial heterogeneity of dissolved arsenic (As) concentrations in shallow groundwater of the Bengal Basin has been attributed to transport of As (and reactive carbon) from external sources or to the release of As from within grey sand formations. We explore the latter scenario in this detailed hydrological and geochemical study along a 300 m transect of a shallow aquifer extending from a groundwater recharge area within a sandy channel bar to its discharge into a nearby stream. Within the 10–20 m depth range, groundwater ages along the transect determined by the 3 H– 3 He method increase from <10 yr in the recharge area to a maximum of 40 yr towards the stream. Concentrations of groundwater As within the same grey sands increase from 10 to 100 to ∼500 μg/L along this transect. Evidence of reversible adsorption of As between the groundwater and sediment was obtained from a series of push–pull experiments, traditional batch adsorption experiments, and the accidental flooding of a shallow monitoring well. Assuming reversible adsorption and a distribution coefficient, K d , of 0.15–1.5 L/kg inferred from these observations, a simple flushing model shows that the increase in As concentrations with depth and groundwater age at this site, and at other sites in the Bengal and Red River Basins, can be attributed to the evolution of the aquifer over 100–1000 years as aquifer sands are gradually flushed of their initial As content. A wide range of As concentrations can thus be maintained in groundwater with increases with depth governed by the history of flushing and local recharge rates, without external inputs of reactive carbon or As from other sources. [ABSTRACT FROM AUTHOR]

The integration of expanded bed adsorption (EBA) with hydrophobic charge-induction chromatography (HCIC) affords a promising new technology to capture antibody from the complex feedstock. New EBA resin T-ABI was prepared with hydrophobic charge-induction ligand 5-aminobenzimidazole (ABI) and used to separate monoclonal antibody (mAb) from CHO cell culture broth. The static and dynamic adsorption behaviors of hIgG and mAb were investigated, and the typical properties of pH dependence and salt tolerance were found. High dynamic binding capacities at 10% breakthrough (18.1-21.4 mg/mL resin) were obtained even for high operation velocities (711-1203 cm/h) in an expanded bed. By optimization of loading pH, elution pH, and expansion factor, hIgG could be separated from the protein mixture (2 mg/mL hIgG and 10 mg/mL bovine serum albumin) with high efficiency. Finally, mAb was separated directly from the CHO cell culture broth with T-ABI EBA under optimized conditions (loading at pH 7.0, elution at pH 4.0 or 4.5, expansion factor of 2.0), and the purity reached 93.7-97.7% with the recovery of 72.6-79.4%. The results indicated that T-ABI resin was suitable to capture hIgG from the complicated feedstock. New separation process with T-ABI EBA showed a promising potential for antibody purification with high productivity and process efficiency, which combined the advantages of HCIC and EBA. [ABSTRACT FROM AUTHOR]

The electronic and magnetic properties of borophene functionalized by 3 d transition metal (TM) atom adsorption are investigated by using first-principles calculations. The results show that the 3 d TM atoms can be adsorbed on borophene with high binding energies ranging between 5.9 and 8.3 eV. Interestingly, the originally nonmagnetic borophene tends to be ferromagnetic when Ti, V, Cr, Mn, and Fe atoms are adsorbed, and the magnetic moments are dominated by the TM atoms. The origin of the ferromagnetism is discussed based on the Stoner criterion. Our results indicate that the magnetic properties of borophene can be effectively tuned through the adsorption of 3 d TM atoms, which could have promising applications in spintronics and nanoelectronics. [ABSTRACT FROM AUTHOR]

Recently, the paper [2] introduced a method for model order estimation based on penalizing adaptively the likelihood (PAL). In this paper, we use the PAL based order estimation method for a nonlinear sinusoidal model and study its asymptotic statistical properties. We prove that the estimator of the model order using the PAL rule is consistent. Simulation examples are presented to illustrate the performance of the PAL method for small sample sizes and to compare it with that of three information criterion-based methods. [ABSTRACT FROM AUTHOR]

Spatial simulations are a valuable tool in understanding dynamic spatial processes. In developing these simulations, it is often required to make decisions about how to represent features in the environment and how events unfold in time. These spatial and temporal choices have been shown to significantly alter model outcomes, yet their interaction is less well understood. In this paper, we make use of a simple group foraging model and systematically vary how features are represented (cell size of the landscape) as well as how events unfold in time (order in which foragers take action) to better understand their interaction. Our results show similar nonlinear responses to changes in spatial representation found in the literature, and an effect of the order in which agents were processed. There was also a clear interaction between how features are represented and how events unfold in time, where, under certain environmental representations results were found to be more sensitive to the order in which individuals were processed. Furthermore, the effects of feature representation, scheduling of agents, and their interaction were all found to be influenced by the heterogeneity of the spatial surface (food), suggesting that the statistical properties of the underlying spatial variable will additionally play a role. We suggest that navigating these interactions can be facilitated through a better understanding of how these choices affect the decision landscape(s) on which agents operate. Specifically, how changes to representation affect aggregation and resolution of the decision surface, and thereby the degree to which agents interact directly or indirectly. We suggest that the challenges of dealing with spatial representation, scheduling, and their interaction, while building models could also present an opportunity. As explicitly including alternate representations and scheduling choices during model selection can aid in identifying optimal agent–environment representations. Potentially leading to improved insights into the relationships between spatial processes and the environments in which they occur. [ABSTRACT FROM AUTHOR]

Adsorption, a fundamental process in heterogeneous catalysis is known to be dependent on the adsorbate–adsorbate and surface–adsorbate bonds. van der Waals (vdW) interactions are one of the types of interactions that have not been examined thoroughly as a function of adsorbate coverage. In this work we quantify the vdW interactions for atomic adsorbates on late transition metal surfaces, and determine how these long range forces affect the coverage dependent adsorption energies. We calculate the adsorption energies of carbon, nitrogen, oxygen, sulfur, fluorine, bromine and chlorine species on Pt(111) and Pd(111) at coverages ranging from 1 4 to 1 ML using the BEEF-vdW functional. We observe that adsorption energies remain coverage dependent, and this coverage dependence is shown to be statistically significant. vdW interactions are found to be coverage dependent, but more significantly, they are found to be dependent on molecular properties such as adsorbate size, and consequently, correlate with the adsorbate effective nuclear charge. We observe that these interactions account for a reduction in the binding energy of the system, due to the destabilizing attractive interactions between the adsorbates which weaken its bond with the surface. [ABSTRACT FROM AUTHOR]

The analysis of protein C-termini is of great importance, because it not only provides valuable information about protein function, but also facilitates the elucidation of proteolytic processing. However, even with the recent methods for the global profiling of protein C-termini, the identification of C-termini is still far behind that of N-termini due to the lack of basic residue and low reactive carboxyl group. Therefore, an unbiased and complementary method for C-termini profiling is imperative. In this work, we developed a negative enrichment strategy to achieve the in-depth analysis of C-terminome. Proteins were firstly amidated to block carboxyl groups, followed by lysyl endoproteinase (LysC) digestion to generate C-terminal peptides with α-amines and internal peptides bearing both α- and ε-amines. After the α-amines were blocked by site-selective dimethylation or succinylation, the remaining ε-amines on internal peptides were labeled with phosphate groups. Finally, internal peptides were depleted by TiO, leaving exclusively the fraction of C-terminal peptides for LC-MS/MS analysis. With Escherichia coli ( E. coli) digests as the sample, the efficiency of amidation, dimethylation/succinylation, phosphate labeling and TiO depletion was proved high. With the combination of dimethyl and succinic blocking strategy, our method enabled the identification of 477 unique C-terminal peptides in E. coli. In comparison with the C-terminal amine-based isotope labeling of substrates (C-TAILS) method, 83 C-termini were identified by both methods, whereas 369 C-termini were unique to C-TAILS and 394 to our dataset. The method proposed is therefore efficient and possibly promotes the comprehensive profiling of C-termini. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

This article deals with role and importance of adsorption in the activated sludge substrate degradation. This process is typically described according to the Monod-Michaelis-Menten (M-MM) kinetics, which is based on the assumption that the substrate has been preadsorbed on floes in order for the biochemical reaction to take place. However, the simple and generalised use of M-MM equation in wastewater treatment modelling could be misleading in describing some specific scenarios, where substrate in the liquid phase is not in equilibrium with substrate inside the floes and, in general, when adsorption and kinetic rates are not comparable. This can occur in numerous process configurations, during plant start-up, when substrate peaks or significant fluctuations are met, in batch processes. An experimental test has been carried out with the aim to investigate the characteristics of the adsorption mechanism and its relationship with the stored mass degradation. Direct application of M-MM kinetics failed in fitting the experimental data. External transport and Glueckauf and Coates particle-phase diffusion relations have been adopted to study substrate transfer to active sites. Andrews and Busby model has then been applied and an excellent accordance with the experimental data has been found. As a final aim of the work, transition from adsorption-to-kinetics has been modelled, which has shown to be very effective for a full understanding of phenomena. [ABSTRACT FROM AUTHOR]

Recycling alum flocs may promote the removal of NOM during the coagulation process. The performance of alum-humic-floc (AHF), poly aluminum chloride (PACl) and AHF and PACl mixtures (AHF+PACl) in the removal of humic acid (HA) were comparatively evaluated in regards to their coagulation behaviors and floc structure characteristics. Jar tests were conducted at neutral pH and in a dosage range from 6.11 to 26.49 mg Al/L. The dual coagulant, AHF with additional PACl, could significantly improve the removal efficiency of organic matter and residual turbidity, which probably depended on the physical adsorption and the charge neutralization mechanism. The experimental data using AHF fit with BET and Freundlich models, which indicated that the adsorption of HA onto AHF was a multilayer adsorption. Floc characterization was also performed to investigate the relationship between floc structure and organic matter removal. The highest removal efficiency of organic matter and residual turbidity occurred when using the combination of AHF with additional PACl as the coagulant, which suggested that fractal dimension of the flocs was the most significant factor in determining the removal of pollutants from the water solution. HA was released again into solution during floc breakage. The combination of AHF and PACl demonstrated a lower release of organic matter after breakage and the stronger dissolved organic carbon (DOC) removal capacity during re-growth process. The functional group on the AHF was the main factor in site-specific hydrogen bonding, which is the main mechanism for removal of HA. [ABSTRACT FROM AUTHOR]

Nanosilica filled polylactide (PLA)/Poly(methyl methacrylate) (PMMA) 50/50 blends with varying silica concentrations were prepared by melt mixing. In this work, the effects of silica concentration and the preferential adsorption between silica and the component on the thermo-mechanical and rheological properties of PLA/PMMA blends were systematically investigated. The results of DSC indicate the miscibility of PLA/PMMA/silica nanocomposites in the solid state, and the incorporation of nanosilica does not only increase the glass transition temperature but also extend the broadness of glass transition. Local nanoscale heterogeneities in the miscible blends are proposed due to the self-concentration of the components, and the presence of nanosilica increased the concentration fluctuation and dynamic heterogeneity of the PLA/PMMA blends. A distinct “crater” structure can be observed in the fractured surfaces of the blend nanocomposites. According to the results of SEM and rheological measurements, it was proposed that PLA molecules were selectively adsorbed on the surface of nanosilica, and the preferential adsorption of PLA changed the blend composition in the “crater” structure and the bulk matrix. The phase separation temperature of the filled PLA/PMMA blends was also improved by the incorporation of nanosilica, implying a potential role of nanosilica in improving the phase stability of PLA/PMMA blends. In addition, nanosilica could increase and entanglement density and decrease the entanglement molar mass of the blends in a concentration-dependent manner. [ABSTRACT FROM AUTHOR]

Novel high capacity hybrid sorbents for CO 2 capture have been developed based on zinc-functionalized ionic liquid (IL) impregnated into mesoporous silica beads derived from calcium alginate template beads. Pore modification and development of a surface-confined layer of IL synergistically enhanced the uptake capacity (up to 8.7 wt%) and kinetics of these materials. Spectroscopic and thermophysical signatures of the IL impregnated materials confirm the existence of a highly confined IL layer at low IL:SiO 2 ratio, and multilayer-mimicking bulk phase at higher IL loading. Our results clearly demonstrate that developing a thin layer of zinc-functionalized IL onto porous silica beads effectively enhances the uptake kinetics by exposing interaction sites across a large surface area, and facilitating diffusion through the pore network of the support. [ABSTRACT FROM AUTHOR]

Calcium alginate cohered beads of copper hexacyanoferrate (CuHCF), and iron hexacyanoferrate (FeHCF), were prepared and studied for their competence in the environmental Cs decontamination. The influence of temperature and solution pH, parameters which are crucial for effective decontamination are studied in detail. Kinetic study performed at varying temperatures showed that adsorption of Cs onto CuHCF is faster than on FeHCF, the difference observed mainly due to the difference in the adsorption capacities of the materials. Additionally, an important environmental issue, which is often omitted, the possibility of release of the ferrocyanide ion into the effluent solution, is discussed in detail. The concentration of total cyanide in the effluent solution passed through FeHCF is comparatively very high beyond pH 4. In contrary, it is lower than in CuHCF passed solution at pH below 4. Based on these results, FeHCF is a good option in highly acidic solutions, and for weakly acidic to slightly alkaline pH, CuHCF is effective. [ABSTRACT FROM AUTHOR]

A continuous-flow adsorption/desorption process for the recovery of phenolic compounds (PCs) from olive mill wastewaters (OMWs) was developed in a 0.53 m packed column, using a previously selected resin (Amberlite XAD16) and an actual OMW. The main goals of the study were (i) to evaluate the PC adsorption/desorption performances of XAD16 by means of adsorption isotherms and adsorption/desorption breakthrough tests, and (ii) to develop a reliable model of the process. A combination of centrifugation and microfiltration resulted necessary to attain a high suspended solid removal (98.5%) and thus avoid clogging of the packed bed. The quality of two packing procedures was evaluated by means of frontal analysis tests. XAD16 performed well in terms of both adsorption yield at 20% breakthrough (87–88%) and PC/COD selectivity (PC/COD adsorption constant = 7–9). The desorption solvent (acidified ethanol) was effectively regenerated by vacuum distillation. The adsorption breakthrough curves were successfully simulated with a 1-D convection/dispersion model with mass-transfer ( R 2 = 0.95–0.99; k L a = 0.8–2.5 · 10 −3 1/s), whereas an equilibrium adsorption model with dispersion failed to predict the experimental data. In the perspective of a process scale-up, the simulation of the best-performing operational condition was used to evaluate the process performances for different column lengths (0.5–10 m). A precise and automated HPLC method for total PC measurement was developed and compared to the traditional Folin–Ciocalteu methodology. Further research is needed to optimize the desorption step, to scale up the process and to evaluate the long-term resin performances. [ABSTRACT FROM AUTHOR]

Adsorption of ibuprofen and tetracycline onto a commercial granular activated carbon, multi-walled carbon nanotubes, and two low-cost activated carbons synthesized in the laboratory, has been investigated. The kinetic experimental data obtained at 30 °C and 250 r.p.m. were fitted to pseudo-first, pseudo-second and Elovich models, obtaining a high accuracy between the experimental data and the pseudo-second order equation. Therefore, the equilibrium adsorption data were analyzed by using Langmuir, Freundlich, Sips, Guggenheim–Anderson–de Boer, and Tempkin models. The highest ibuprofen adsorption capacity was obtained for AC-RH activated carbon, 239.8 mg g −1 , and in the case of tetracycline removal was of 845.9 mg g −1 onto the peach stones activated carbon. These results are linked to the textural and chemical surface properties of the adsorbents. Fixed-bed experiments allowed obtaining good removal efficiencies at breakthrough time, 97.2% for ibuprofen and 96.1% for tetracycline onto activated carbon from rice husk. Desorption efficiencies were moderate in all systems, being higher by using NaOH solution at high concentration as elution agent. Finally, the important role of the acidic functionalities in the adsorption process was demonstrated by the accomplishment of FTIR studies of the adsorbents before and after the adsorption of both pharmaceutical compounds. [ABSTRACT FROM AUTHOR]

The adsorption of dioxin–modeling compounds on activated carbon has been investigated in this manuscript. A series of benzene compounds with different numbers and types of substituent groups were chosen as the dioxin–modeling compounds, and the gas adsorption behaviors were evaluated using a fixed-bed reactor. The adsorption results showed that the methyl, chlorine and phenolic substituent groups on a benzene ring can greatly promote gas adsorption, especially the phenolic group, the addition of which increased the adsorption capacity to more than 1.5 times that of benzene. The adsorbed AC samples were detected by TPD-MS with the combines between adsorbate and adsorbent analyzed, the methyl and chlorine groups enhanced the attraction between the gaseous compounds and AC, while the phenolic group reduced the combine force due to its oxidation on AC. The effect of an increasing number of chlorine substituents on the adsorption of gases and the combine forces were investigated. On average, the capacity of gas adsorption doubled and the desorption temperature increased by 20 K with one chlorine substituent on a benzene ring. The attachment of chlorine substituent groups to the AC lactone and quinone groups has been verified again, and the increasing chloric substituent groups consumed more oxygen groups. According to the linear relationships between gas properties and adsorption behaviors, the actual dioxin adsorption capacity has been inferred to be 600 mg/g or greater, showing that dioxin is much more easily adsorbed on AC than the conventional organic gases. [ABSTRACT FROM AUTHOR]

CPL- n porous coordination polymers (PCPs) in general exhibit concomitant structural expansion during adsorption without a sudden gate-opening feature, but implications on the practical aspects of gas separation or storage are yet to be understood. In an attempt to gain further knowledge, we have gathered CO 2 and CH 4 adsorption/desorption and fractional uptake data using Cu 2 (pzdc) 2 L ( pzdc : pyrazine-2,3-dicarboxylate) variants CPL-2 ( L : 4,4′-bipyridine) and CPL-5 ( L : 1,2-Di (4-pyridyl) ethylene). Both exhibited good affinity toward CO 2 probably because of interactions with the adsorbate permanent quadrupole moment. Adsorption and desorption of CO 2 also features hysteresis that increases in size upon an increase in the maximum pressure registered during a complete adsorption/desorption cycle. Furthermore, the size of the hysteresis increases with an increase in equilibration time interval ( t e ), suggesting that the structural expansion proceeds at a slower rate compared to the adsorption one. CO 2 heats of adsorption (max. −27 kJ mol −1 ) and desorption (max. 36 kJ mol −1 ) also reflect the aforementioned framework expansion, particularly in the case of CPL-2. Diffusion time constants calculated using a phenomenological model show hysteresis up to gas pressures of ca. 0.4 atm. The structural changes seem beneficial for the equilibrium separation of bulk quantities of CO 2 from CH 4 as evidenced by selectivity values based on the Ideal Adsorbed Solution Theory ( S IAST ∼ 6.7 avg.), which are larger than those of MOFs with similar pore dimensions. Although kinetic selectivity values are similar to that of other metal organic frameworks (MOFs), these are smaller than those of small pore zeolites. [ABSTRACT FROM AUTHOR]

A new approach is proposed for pre-concentrating emerging pollutants, taking nalidixic acid as representative. The approach consists of performing successive adsorption–desorption cycles in order to remove the pollutant from the main stream, generating a new stream with higher pollutant concentration during the adsorbent regeneration. For accomplishing these scopes (efficient removal and capability for pre-concentrate), adsorbents presenting both high adsorption capacity and regeneration easiness are needed. In this work, the performance of three different adsorbents is studied: activated carbon (GF-40), multi-walled carbon nanotubes (MWCNTs) and high surface area graphite (HSAG-500). Adsorption experiments were performed at 25 °C, whereas two different desorption temperatures (35 and 40 °C) were chosen in order to evaluate the ability of the materials for concentrating the NAL. The adsorption breakthrough curves were modeled considering different models: Bed Depth Service Time (BDST), Thomas and Yoon-Nelson. Although activated carbon largely presents the highest adsorption capacity, it is difficult to regenerate needing long regeneration times, leading to very dilute regeneration solutions. By contrast, MWCNTs present lower adsorption capacity, but they are more easily regenerated leading to higher NAL concentrations. [ABSTRACT FROM AUTHOR]

Organo-montmorillonites (OMts) modified by cationic surfactant (hexadecyltrimethylammonium bromide, C16) and zwitterionic surfactant (hexadecyldimethyl (3-sulphonatopropyl) ammonium, Z16) were used to remove phenol and Cu(II) from aqueous solution. The OMts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), Fourier-transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and C, H, and N elemental analyses. Besides the independent adsorption of single contaminants, simultaneous and sequential adsorption of phenol and Cu(II) onto OMts were also investigated. The organic carbon contents of the two OMts were similar but the basal spacing of Z16 modified montmorillonite (Z16-Mt) was larger than that of C16 modified montmorillonite (C16-Mt) indicating a higher packing density of surfactant and hydrophobicity in C16-Mt with a slight higher adsorption capacity toward phenol. On the other hand, C16-Mt showed much lower capacity in adsorbing Cu(II) as compared with raw montmorillonite. On the contrary, the adsorption capacity of Z16-Mt toward Cu(II) was comparable with that of raw montmorillonite. The equilibrium data of phenol and Cu(II) were fitted satisfactorily with Linear and Langmuir models, respectively. In the sequential adsorption system, the adsorption of one contaminant was not affected by the other pre-adsorbed one; desorption of pre-adsorbed contaminant was also investigated. For both two contaminants, one did not affect the adsorption of the other one onto Z16-Mt and C16-Mt in the simultaneous system. Z16-Mt could rapidly and efficiently remove both phenol and Cu(II) simultaneously. The adsorption kinetics followed the Pseudo-second order model. The results of this work might provide novel information for developing new effective adsorbents toward organic contaminants and heavy metals. [ABSTRACT FROM AUTHOR]

Microengraving is a novel immunoassay for characterizing multiple protein secretions from single cells. During the immunoassay, characteristic diffusion and kinetic time scales τD and τK determine the time for molecular diffusion of proteins secreted from the activated single lymphocytes and subsequent binding onto the glass slide surface respectively. Our results demonstrate that molecular diffusion plays important roles in the early stage of protein adsorption dynamics which shifts to a kinetic controlled mechanism in the later stage. Similar dynamic pathways are observed for protein adsorption with significantly fast rates and rapid shifts in transport mechanisms when C0* is increased a hundred times from 0.313 to 31.3. Theoretical adsorption isotherms follow the trend of experimentally obtained data. Adsorption isotherms indicate that amount of proteins secreted from individual cells and subsequently captured on a clean glass slide surface increases monotonically with time. Our study directly validates that protein secretion rates can be quantified by the microengraving immunoassay. This will enable us to apply microengraving immunoassays to quantify secretion rates from 104-105 single cells in parallel, screen antigen-specific cells with the highest secretion rate for clonal expansion and quantitatively reveal cellular heterogeneity within a small cell sample. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases present amongst the highest mortality risks in Western civilization and are frequently caused by arteriosclerotic vessel failure. Coronary artery and peripheral vessel reconstruction necessitates the use of small diameter systems that are mechanically stress-resistant and biocompatible. Expanded polytetrafluorethylene (ePTFE) is amongst the materials used most frequently for non-degradable and bio-degradable vessel reconstruction procedures, with thermoplastic polyurethanes (TPU) representing a promising substitute. The present study describes and compares the biological adsorption and diffusion occurring with both materials following implantation in rat models. Gel electrophoresis and thin-layer chromatography, combined with mass spectrometry and mass spectrometry imaging, were utilized to identify the adsorbed lipids and proteins. The results were compared with the analytes present in native aorta tissue. It was revealed that both polymers were severely affected by biological adsorption after 10 min in vivo. Proteins associated with cell growth and migration were identified, especially on the luminal graft surface, while lipids were found to be located on both the luminal and abluminal surfaces. Lipid adsorption and cholesterol diffusion were found to be correlated with the polymer modifications identified on degradable thermoplastic urethane graft samples, with the latter revealing extensive cholesterol adsorption. The present study demonstrates an interaction between biological matter and both graft materials, and provides insights into polymer changes, in particular, those observed with thermoplastic urethanes already after 10 min in vivo exposure. ePTFE demonstrated minor polymer modifications, whereas several different polymer signals were observed for TPU, all were co-localized with biological signals. [ABSTRACT FROM AUTHOR]

The removal of Cr(VI) ions from aqueous solutions via adsorption onto black rice husk ash was studied at different conditions from kinetics point of view. The effects of certain parameters on the removal of Cr(VI) were investigated, including initial pH, contact time, adsorbent dose, initial concentration and temperature. Adsorption process was found to be highly pH dependent. The kinetic data of Cr(VI) sorption are in a good agreement with pseudo-second-order kinetic model at all studied temperatures and initial concentrations. The kinetic parameters of the adsorption process were estimated — rate constant, initial rate of adsorption and activation energy. [ABSTRACT FROM AUTHOR]

Chrysotile nanotubes (ChNTs) synthesized under hydrothermal conditions were functionalized by surface grafting in toluene with 3-mercaptopropyltrimethoxysilane (MPTMS). The mercapto functionalized ChNTs (ChNTs-SH) were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N 2 adsorption–desorption. The adsorption of Pb(II) and Cd(II) on ChNTs-SH was investigated systematically by evaluating the effects of contact time, adsorbent dosage, initial pH and temperature. Initial pH could play an important role on the adsorption of Pb(II) and Cd(II) onto ChNTs-SH. The adsorption kinetics and isotherms of Pb(II) and Cd(II) on ChNTs-SH indicated that the kinetic data of adsorption reactions were well described by the pseudo-second-order model (R 2 = 0.9960 and 0.9970, respectively) and the adsorption isotherms were fitted well by the Langmuir model ( q m Pb(II) = 83.96 mg/g, q m Cd(II) = 39.23 mg/g at 298 ± 1 K). The thermodynamic parameters (Δ G , Δ H and Δ S ) indicated that the adsorption process of Pb(II) and Cd(II) on ChNTs-SH was spontaneous and endothermic. ChNTs-SH could obviously improve the adsorption capacity for Pb(II) by 225.4% and for Cd(II) by 123.5% as compared with ChNTs. Overall, ChNTs-SH could provide a potential remedy for heavy metal contamination in wastewater. [ABSTRACT FROM AUTHOR]

A comparative numerical analysis of three approaches for the breakthrough curve modeling has been performed using the experimental data of packed-bed fluoride adsorption on a novel aluminum-doped bone char using micro-columns. The performance of traditional Thomas and Yan breakthrough equations, a mass transfer model for a mobile fluid flowing through a porous media, and an artificial neural network with the optimal brain surgeon approach have been studied and discussed in the data fitting of asymmetric fluoride breakthrough curves. Results of this study highlighted the relative merits of tested breakthrough curve models for the non-linear adsorption data analysis involved in water defluoridation using a new adsorbent. In particular, the application of artificial neural networks is reliable for fitting highly non-linear adsorption patterns of priority water pollutants. [ABSTRACT FROM AUTHOR]

A kind of typical metal-organic frameworks (MOFs) material, HKUST-1 was prepared by hydrothermal method and characterized by XRD and SEM. The results of characterizations manifested that HKUST-1 showed a regular octahedral crystal structure. The as-prepared HKUST-1 was modified by several kinds of organic base materials and the 2 adsorption behaviors of modified HKUST-1 materials were evaluated. The 2 adsorption capacities of different base modified HKUST-1 varied with the base intensity of modified organic base materials. [ABSTRACT FROM AUTHOR]

This study focuses on the adsorption behavior of using Lemna minor (Duckweed) as a potential low-cost biosorbent for the removal of methyl violet 2B (MV). The effects of parameters such as contact time (30-240 min), settling time (30-240 min), pH of dye solution from pH 2 to 12 were studied. Optimum contact time and settling time for the maximum removal of MV were 2 and 1 h, respectively. Maximum MV removal was observed at its ambient pH. Elemental analysis and functional group characterization of the biosorbent were carried out using X-ray fluorescence and Fourier-transformed infrared spectroscopy, respectively. Surface morphology of Duckweed, before and after adsorption of MV, was characterized using scanning electron microscope, and ionic strengths and pre-treatment of biosorbent were also investigated. Six different isotherm models, namely Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Redlich-Peterson and Sips isotherms, were performed on the equilibrium adsorption isotherm of MV. Experimental data for adsorption of MV correlate well with both the Langmuir and Sips isotherm models. The maximum biosorption capacity ( q) at 298 K was 332.5 mg g (Langmuir) and 307.3 mg g (Sips) for MV, which is far superior to most biosorbents reported. Kinetics study followed the pseudo-second order. [ABSTRACT FROM AUTHOR]