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Herein, poly(aniline‐co‐pyrrole) has been synthetized and investigated to adsorb phenylbutazone (PBZ), ceftiofur (CEF) and prednisolone (PRD) in aqueous medium as proof of concept. After proper adsorbent characterization, some studies were carried out in batch process, i. e., contact time, pH, and concentration. The adsorption mechanism has been conducted using kinetic and isothermal models. It was found that the reaction equilibrium was reached in 20 min for all analytes. The best fit for the experimental data were obtained employing the models of dual‐site Langmuir–Freundlich, Fritz–Schlunder and Langmuir, with R2=0.999, 0.952 and 0.974, for PBZ, CEF and PRD, respectively. For PBZ, CEF and PRD, poly(aniline‐co‐pyrrole) provided a Qmax=238.8 mg g−1 and Kmax=0.086 L g−1, Q=0.028 mg g−1 and Kmax=3.258 L g−1, Q=13.66 mg g−1 and KL=0.005 L g−1, respectively. Finally, the copolymer was evaluated in solid phase extraction, which showed recovery around 70 % for PBZ, offering also exciting opportunities for further application in the separation process. [ABSTRACT FROM AUTHOR]

SBA‐15/polypyrrole composite was synthesized by polymerizing pyrrole in the presence of SBA‐15. The samples were characterized using the following techniques: low‐angle XRD, wide‐angle XRD, FTIR, FESEM, TGA, HRTEM, and BET. From the low‐angle XRD analysis, it confirms the formation of a mesoporous hexagonal structure (p6 mm). From the HRTEM image, an orderly arrangement of mesopores is evident. Using adsorption techniques, our objective is to remove sunset yellow, indigo carmine, titan yellow, and orange G dye from aqueous solutions with SBA‐15/polypyrrole composite. The removal efficiency for all the dyes was greater than 90 %. The isotherm was verified to follow the Langmuir isotherm model. The maximum adsorption capacities for sunset yellow, indigo carmine, titan yellow, and Orange G were found to be 78.74 mg/g, 83.33 mg/g, 78.74 mg/g, and 106.38 mg/g, respectively. The adsorption kinetics followed a pseudo‐second‐order model, and the R2 value was greater than 0.99 for all the dyes. The thermodynamic parameters of ΔG°, ΔS°, and ΔH° showed negative values, indicating that the adsorption was spontaneous, decreased entropy, and was exothermic. The recycling of the SBA‐15/polypyrrole composite resulted in a 90 % removal efficiency for three cycles. Therefore, the present adsorbent could be applied to treat industrial effluents that contain these dyes. [ABSTRACT FROM AUTHOR]

The current study discusses application of the lanthanum ions (La3+) as an activating agent incorporated /immobilized into coconut shell–based granular activated carbon (GAC) for porosity development; subsequently, the carbon material is used for the adsorption of phenol from aqueous solutions. The new carbons were characterized using FTIR, XRD, CHNO, burn off, and carbon yield. The surface functional groups were determined by Boehm titration. The Brunauer–Emmett–Teller (BET) surface area of the carbons is 953 m2 g−1 (GACLa1073), 997 m2 g−1 (GAC383), and 973 m2 g−1 (GACO383). Langmuir, Freundlich, Dubinin–Radushkevich, and John–Sivanandan Achari (J‐SA) isotherm models on the equilibrium isotherm data were examined for the new carbon‐phenol system. It is found that the Langmuir isotherm fits better with a monolayer adsorption capacity, highest for GACLa1073 (387.59 mg g−1) followed by GAC383 (303.03 mg g−1) and GACO383 (197.62 mg g−1). Kinetic studies reveal that the adsorption system follows the pseudo–second‐order kinetic model. Isotherm analysis by the phase change method of John‐Sivanandan Achari (J‐SA) isotherm gives a better insight into adsorption phenomena, which is accompanied by regeneration studies of carbon with >75% for GACLa1073 after three cycles. [ABSTRACT FROM AUTHOR]

Adsorption and photocatalytic decomposition of anionic and cationic surfactants are presented. Two different types of photocatalysts were studied, commercial TiO2‐P25 (Evonik) with pHpzc = 5.65 and nitrogen‐modified TiO2/N pHpzc = 6.7 (point of zero charge). Two different types of surfactants were used: anionic surfactant NaDBS (sodium dodecylbenzene sulfonate) and cationic surfactant BtCl (benzethonium chloride). Obtained adsorption isotherms of NaDBS and BtCl comply with the conditions of monolayer Langmuir model isotherms. The maximal anionic surfactant adsorption took place at acidic pH and it was higher for TiO2/N (196 mg g−1) than for commercial TiO2‐P25 (140 mg g−1). There was the opposite situation in the case of cationic surfactants, higher adsorption took place at alkaline condition and it was higher for TiO2/N (100 mg g−1) than for commercial TiO2‐P25 (85 mg g−1). Photocatalytic degradation has been found to be more effective in neutral and high than in low pH solutions for both surfactants. It is mainly the difference between charges of the surface of photocatalysts and ionic parts of individual surfactants that determined the effectiveness for each of them. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Pomelo (Citrus grandis) is the largest citrus fruit, the peel of which is a well‐known agricultural wastes. Disposal of pomelo peel after consumption is a serious environment problem. As a natural, versatile bio‐absorbent, pomelo peel has shown excellent adsorption capacity for several pollutants, attributed to its micro‐pores; however, there is no relevant report on its adsorption capacity for natural products or food ingredients. The ability of pomelo peel to adsorb epigallocatechin‐3‐gallate (EGCG) was examined in this study. The physicochemical characterizations of pomelo peel were determined by Fourier transform infrared spectroscopy, scanning electron microscopy and high‐performance liquid chromatography. The adsorption process of EGCG onto pomelo peel from aqueous solution was carried out at a range of concentrations (50–800 mg L−1) and temperatures (25, 40 and 55 °C). RESULTS: The main components of pomelo peel are composed of dietary fiber, which provide sufficient adsorption sites during the adsorption process. The adsorption of EGCG onto pomelo peel showed excellent fitness with a pseudo‐second‐order model. Both Langmuir and Freundlich models were able to describe the isothermal adsorption of EGCG onto pomelo peel. The results of thermodynamic analysis suggested that adsorption is spontaneous and endothermic in nature, and that the process is likely to be dominated by a physisorption mechanism. CONCLUSION: The results of this study indicate that pomelo peel has potential adsorption capacity for EGCG, which can be used as an effective, low‐cost carrier for delivery of natural products in functional food and dietary supplement applications. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Molecular simulation, through the computation of adsorption isotherms, is a useful predictive tool for the selective capacity of nanoporous materials. Generally, adsorbents are modelled as rigid frameworks, as opposed to allowing for vibrations of the lattice, and this approximation is assumed to have negligible impact on adsorption. In this work, this approach was tested in an especially challenging system by computing the adsorption of the chiral molecules 2‐pentanol, 2‐methylbutanol and 3‐methyl‐2‐butanol in the all‐silica and germanosilicate chiral zeolites STW and studying their lattice vibrations upon adsorption. The analysis of single‐ and multicomponent adsorption isotherms showed the suitability of STW‐type zeolites as molecular sieves for chiral separation processes, which pose a challenging task in the chemical and pharmaceutical industries. Moreover, new experimental adsorption data validate the force field employed. The results reveal that the lattice vibrations of the all‐silica framework are sorbate‐independent, while those of germanosilicate STW show host–guest coupling modulated by uptake and sorbate type that disrupts the chiral recognition sites. This study indicates that the effects of intrinsic flexibility on the selective capacity of nanoporous materials may range from low to high impact, and some of them could not have been foreseen even after examination of the structural dynamics of an empty framework. [ABSTRACT FROM AUTHOR]

In this study, a natural loess soil was evaluated as an adsorbent of Li+ in seawater. Only Li+ was adsorbed preferentially by loess over other cations in seawater despite having the lowest concentration. The adsorption studies of Li+ with loess were assessed using the batch equilibration method. In batch adsorption experiment, the various factors such as agitation time, initial concentration, and amount of dose were investigated. Adsorption isotherm and kinetic studies were performed to quantify the adsorption capacity and adsorption rate of Li+ by loess from seawater. The equilibrium data of adsorption were fitted by using the Freundlich and Langmuir isotherm models. It was seen that the Langmuir isotherm is better in describing the adsorption process of Li+ by loess due to its higher correlation coefficient R2 value. The maximum adsorption capacity of loess for Li+ obtained by Langmuir isotherm was 0.193 mg/g. The pseudo-first-order, the pseudo-second-order, and the intra-particle diffusion kinetic models were employed to analyze the time-dependent adsorption rate of Li+. It was found that the adsorption of Li+ closely follows the pseudo-second-order kinetic model, from which a very accurate estimation of the equilibrium adsorption capacity ( qe,cal) was achieved, as well as the higher R2. Because of its low-cost and high selectivity towards Li+, loess could be probably an applicable adsorbent for the recovery of Li+ from seawater. [ABSTRACT FROM AUTHOR]

A series of four micro- or mesoporous metal-organic frameworks [UiO-66(Zr), UiO-66(Zr)_NH2, MIL-100(Fe), MIL-127(Fe)] were synthesized in powder form and pelletized in the form of spheres by using a polyvinyl-based binder. The effect of pelletization on the adsorption of a series of gasses (N2, CO, CO2, CH4, C2H6, C3H8, C3H6, C4H10) at 303 K was evidenced in the adsorption isotherms and the enthalpies of adsorption measured by using microcalorimetric analysis. As expected, uptakes of gas per gram of material were lower for the spheres than for the powder. However, taking into account the bulk density, this tendency was inverted, suggesting that the spherical materials are of distinct interest for gas-based applications. Nevertheless, other effects including partial pore restriction and active site 'protection' may equally be evidenced for some pelletized materials, suggesting that the polyvinyl binder may play a more complex role. [ABSTRACT FROM AUTHOR]

Two zeolitic imidazolate frameworks, ZIF-9 and ZIF-71, are evaluated by adsorption experiments and molecular simulations with respect to their potential towards olefin/paraffin separation. Pure component adsorption isotherms are measured and compared to grand-canonical Monte-Carlo (GCMC) simulations. The experiments show that the adsorption of the paraffin is favorable over the olefin in both structures. Whereas the isotherms are predicted well by simulations for ZIF-71, in case of ZIF-9 only the saturation loading could be computed accurately because the latter material seems to undergo a so-called gate-opening effect upon adsorption of guest molecules; ZIF-71 does not show this effect. Both structures show promising results with respect to olefin/paraffin separation. [ABSTRACT FROM AUTHOR]

Activated carbons are one of the most common industrial adsorbents in liquid-phase applications. It is known that the surface groups of the activated carbon can have a significant influence on the adsorption process from the liquid phase. Therefore, it is desirable to measure surface groups on activated carbons. This opens up the possibility to use group-contribution methods to model and predict adsorption isotherms. An idea is presented to characterize the inner surface of activated carbons by three types of surface groups: aromatic, polar, and nonpolar surface groups. The amounts of these surface groups were calculated from excess adsorption isotherms of probe molecules on ten activated carbons. This lays the groundwork for further simulation studies of liquid-phase adsorption using group-contribution methods. [ABSTRACT FROM AUTHOR]

The aim of the present study is to explore the possibility of utilizing fly ash, loess and activated charcoal for the adsorption of Li in aqueous solution. Batch adsorption experiments were performed to evaluate the influences of various factors like initial concentration, contact time, and temperature. The adsorption data showed that fly ash and activated charcoal are not effective for the adsorption of Li. On the contrary, loess showed much higher adsorption capacity for Li. The adsorption of Li on loess was highly concentration dependent. It was found that the adsorption capacity of loess is favored at a lower Li concentration. At equilibrium, approximately 95% of adsorption was achieved by loess. The equilibrium data were fitted well to the Freundlich isotherm model. The pseudo-second-order kinetic model appeared to be the better-fitting model because it has higher R2 compared to the pseudo-first-order kinetic models. The thermodynamic parameters such as free energy Δ G, the enthalpy Δ H, and the entropy Δ S were calculated. [ABSTRACT FROM AUTHOR]

We present a systematic study of metal-organic frameworks (MOFs) for the storage of oxygen. The study starts with grand canonical Monte Carlo simulations on a suite of 10 000 MOFs for the adsorption of oxygen. From these data, the MOFs were down selected to the prime candidates of HKUST-1 (Cu-BTC) and NU-125, both with coordinatively unsaturated Cu sites. Oxygen isotherms up to 30 bar were measured at multiple temperatures to determine the isosteric heat of adsorption for oxygen on each MOF by fitting to a Toth isotherm model. High pressure (up to 140 bar) oxygen isotherms were measured for HKUST-1 and NU-125 to determine the working capacity of each MOF. Compared to the zeolite NaX and Norit activated carbon, NU-125 has an increased excess capacity for oxygen of 237 % and 98 %, respectively. These materials could ultimately prove useful for oxygen storage in medical, military, and aerospace applications. [ABSTRACT FROM AUTHOR]

The structural and chromatographic characterization of two novel fluorinated mesoporous materials prepared by covalent reaction of 3-(pentafluorophenyl)propyldimethylchlorosilane and perfluorohexylethyltrichlorosilane with 2.5 μm fully porous silica particles is reported. The adsorbents were characterized by solid state 29Si, 13C, and 19F NMR spectroscopy, low-temperature nitrogen adsorption, elemental analysis (C and F), and various chromatographic measurements, including the determination of adsorption isotherms. The structure and abundance of the different organic surface species, as well as the different silanol types, were determined. In particular, the degree of so-called horizontal polymerization, that is, Si-O-Si bridging parallel to the silica surface due to the reaction, under 'quasi-dry' conditions, of trifunctional silanizing agents with the silica surface was quantified. Significant agreement was found between the information provided by solid-state NMR, elemental analysis, and excess isotherms regarding the amount of surface residual silanol groups, on the one hand, and the degree of surface functionalization, on the other. Finally, the kinetic performance of the fluorinated materials as separation media for applications in near-ultrahigh-performance liquid chromatography was evaluated. At reduced velocities of about 5.5 (ca. 600 bar backpressure at room temperature) with 3 mm diameter columns and toluene as test compound, reduced plate heights on the order of 2 were obtained on columns of both adsorbents. [ABSTRACT FROM AUTHOR]

Porous carbon fiber with hollow structure and hydrophilic groups was successfully prepared from cotton. The structures and surface chemical properties of the porous carbon fiber were characterized by nitrogen adsorption isotherms, thermogravimetry, FTIR spectroscopy, and scanning electron microscopy. The morphologies of porous carbons prepared under different conditions were observed and compared. The resulting porous carbons had a microporous structure with a pore size distribution around 0.7-2.0 nm. The pyrolysis and decomposition of cotton to form a condensation cross-linked ring structure took place from 230 to 350 °C. Nitrogen-containing groups could be incorporated into the carbon matrix by urea decomposition during the carbonization process. The porous carbon contained more hydrophilic groups and its fiber structure was kept; the carbon yield was improved in the presence of KOH/urea. The porous carbon fiber showed high adsorption capacities of CO2 as a result of its surface hydrophilic groups and developed pore structure. [ABSTRACT FROM AUTHOR]

The adsorption isotherms of hydrogen on microporous zeolite ZSM-5, at supercritical conditions, have been modeled using the monolayer lattice density functional theory (LDFT) models, where the simple cubic lattice, face-centered cubic lattice, body-centered cubic lattice and tetragonal lattice structures are assumed for the arrangements of the adsorption sites inside pores based on the size and shape of the zeolite. The results indicate that the monolayer LDFT models appear to be effective in describing hydrogen adsorption on zeolite ZSM-5 at supercritical conditions, and the calculated adsorption isotherms agree well with the experimental isotherms measured previously. The layer density of adsorbed phase is presented versus the bulk density and temperature. It is found that the densities of adsorbed phase on adsorbent surface are much higher than the bulk density for temperature range under study. However, in the core region, the layer densities are close to the bulk density. The monolayer adsorption is suitable for hydrogen on ZSM-5 zeolite. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Ad- and desorption are common techniques for the purification of natural substances. The main drawback is the tedious experimental procedure for resin and solvent screening. An approach of fully automated batch experiments is presented. In order to fulfill all requirements like automation of flexible dosing of loose resins, handling organic solvents, and providing reproducible conditions, these experiments are performed on a custom-built modular robotic platform. The batch ad- and desorption experiments were fully automated for the determination of essential process parameters like kinetics, isotherms, and thermodynamic parameters without the need of manual intervention. Thus, the hands-on time could be significantly reduced by more than 90 % which contributes to improved health and safety outcome by preventing the contact of operators to potentially hazardous materials. [ABSTRACT FROM AUTHOR]

Three Schiff bases, 2-acetylpyridine thiosemicarbazone ( I), 2-acetylpyridine-(4-methylthiosemicarbazone) ( I), and 2-acetylpyridine-(4-phenylthiosemicarbazone) ( I) were tested against corrosion of cast iron in aqueous solutions of HCl, NaOH, NHCl, and NaCl by means of a mass loss method and electrochemical measurements. The inhibition efficiency is directly proportional to inhibitor concentration, while it decreases with prolonged immersion time and at low temperatures. In order to study the effect of an additive, synergism of KI was also studied. The adsorption of Schiff bases in corrosive media obeys Langmuir's isotherm, both in the presence and absence of KI. The UV-Vis, FT-IR, WAXD and SEM analyses were carried out to support the mechanism of corrosion inhibition. The ΔG values reveal that the inhibition was mainly due to physisorption of the inhibitor molecules on the surface of cast iron. The electrochemical polarization results showed the predominantly cathodic nature of the inhibitors. [ABSTRACT FROM AUTHOR]

The surface properties of a series of imidazoline-based dissymmetric bis-quaternary ammonium (DBA) salts with different hydrophobic chain lengths DBA-12, DBA-14 and DBA-16 were determined. The adsorption behaviors of these compounds in 1 M HCl solution and their inhibitive effect on Q235 steel (U12350) were investigated using the weight-loss method, polarization, and electrochemical impedance spectroscopy. Results indicate that the three inhibitors all showed good inhibition performance for Q235 Steel in 1 M HCl solution and were found to be mixed-type inhibitors. The adsorption behavior of the three inhibitors can fit the Langmuir isotherm equation and the values of $$ \Updelta G_{\text{ads}}^{0} $$ are around or lower than 40 kJ mol, indicating that there is a stronger chemical adsorption. [ABSTRACT FROM AUTHOR]

Industrial wastewater may contain high molybdenum concentrations, making treatment before discharge necessary. In this paper, the removal of molybdate anions from water is presented, using clinoptilolite zeolite coated with magnetite nanoparticles. In batch experiments the influence of pH, ionic strength, possible interfering (oxy)anions, temperature and contact time is investigated. Besides determination of kinetic parameters and adsorption isotherms, thermodynamic modeling is performed to get better insight into the adsorption mechanism; molybdenum is assumed to be adsorbed as a FeOMoO2(0H).2H2O inner-sphere complex. At the optimum pH of 3, the adsorption capacity is around 18 mg molybdenum per gram adsorbent. The ionic strength of the solution has no influence on the adsorption capacity. Other anions, added to the molybdenum solution in at least a tenfold excess, only have a minor influence on the adsorption of molybdenum, with the exception of phosphate. Adsorption increases when temperature is increased. It is demonstrat-ed that the adsorbent can be used to remove molybdenum from industrial wastewater streams, and that the limitations set by the World Health Organization (residual concentration of 70&mgr;g/1 Mo) can easily be met. Water Environ. Res., 84, 753 (2012). [ABSTRACT FROM AUTHOR]

This work investigated the use of ultrafiltration (UF) or microfiltration (MF) membranes combined with natural minerals for the pre-treatment of wastewater containing high amounts of lead. The effects of initial lead concentration, solution pH, membrane pore size, mineral type and concentration and mineral - metal contact time were investigated. Lead removal accomplished by the UF system was higher in wastewater compared to that obtained in aqueous solutions and this was attributed to the formation of insoluble metal precipitates/complexes, which were effectively retained by the membranes. At pH = 6 the dominant removal mechanism was precipitation/complexation, while mineral adsorption enhanced lead removal. The combined use of minerals and UF/MF membranes can effectively remove lead from wastewater resulting in a final effluent that can be further treated biologically with no biomass inhibition problems or can be safely discharged into municipal sewers. Kinetics investigation revealed a two-stage diffusion process for all minerals employed. The Langmuir isotherm exhibited the best fit to the experimental data. [ABSTRACT FROM AUTHOR]

A hexagonal mesoporous silica (HMS) and its postfunctionalized counterparts with propyl (P-HMS) and aminopropyl (AMP-HMS) were prepared and characterized by elemental analysis, N2 adsorption, powder x-ray diffraction, Fourier-transform infrared, and surface charge measurements. Batch experiments were further performed to systematically investigate adsorption properties of these materials toward two nonpolar aromatic compounds (pyrene and pentachlorobenzene) and three phenolic compounds (2,4-dichlorophenol, pentachlorophenol, and 4-methyl-2,6-dinitrophenol) in aqueous solutions. The adsorption isotherms were well described by the Freundlich model and varied in adsorption linearity. For HMS and P-HMS, the adsorption of pyrene and pentachlorobenzene was much stronger than that of pentachlorophenol at pH slightly greater than 6. Alternatively, for AMPHMS, pentachlorophenol and 4-methyl-2,6-dinitrophenol showed comparable or stronger adsorption affinity than the other target compounds did, suggesting that a major role is played by electrostatic interactions of the two phenols. Furthermore, adsorption decreased with increasing pH for all adsorbate-adsorbent combinations except that of pentachlorophenol and 4-methyl-2,6-dinitrophenol on AMP-HMS, which showed bell-shaped curves with the maximum adsorption at pH close to the pKa. The advantages of reversible adsorption and fast adsorption/desorption kinetics (<5 min), as compared to commercial microporous activated carbons, make AMP-HMS a promising candidate to remove selected phenolic compounds in water treatment. [ABSTRACT FROM AUTHOR]

The adsorption process is gaining interest as an effective process for advanced water and wastewater treatment. Phenol, as a toxic material in industrial effluents, should be removed because of its environmental and health effects. The present study involves an investigation of the use of three carbonaceous materials-activated carbon laboratory-grade (ACL), almond shell charcoal (ASC), and walnut shell charcoal (WSC)-as adsorbents for the removal of phenol from aqueous solutions. For the first time, the adsorptive removal of phenol using ASC and WSC was investigated. Findings have been compared with (ACL) results. Batch experiments were carried out to obtain adsorption equilibrium isotherms with phenol-spiked synthetic solutions. The effects of adsorbent amounts, pH0, initial concentration, and contact time on the adsorption of phenol were studied. Maximum removals of phenol from contaminant water with ACL, ASC, and WSC were 99.87, 91.36, and 78.17%, respectively, and from industrial wastewater were 99.71, 85.54, and 65.49%, respectively. [ABSTRACT FROM AUTHOR]

This work investigated the adsorption of autoantibodies such as anti-SS-A/Ro, anti-SS-B/La, anti-Sm, and anti-dsDNA on protein L-agarose gel. In order to determine better conditions for IgG adsorption on this matrix, some buffer systems were tested. Adsorption data were analyzed using the Langmuir and Langmuir–Freundlich isotherm models. The experimental isotherms were best described by the Langmuir–Freundlich model, which indicated negative and positive cooperativities for binding in the presence of PBS and HEPES buffers, respectively. TheKd values for phosphate buffered saline solution (PBS) and hydroxyethylpiperazine ethanesulfonic acid (HEPES) were 2.8 × 10−7 M and 3.2 × 10−7 M, respectively, which indicate a high affinity between IgG and the immobilized protein L. The amount of protein adsorbed per amount of protein loaded was high for anti-Sm (44%) and anti-dsDNA (46%), but low for anti-SS-B/La (9%). The amount of albumin adsorbed was lower than 0.06 mg/mL, which may remove the need for a plasma replacement solution in clinical apheresis. [ABSTRACT FROM AUTHOR]

Summary Water activity in hygroscopic solids determines the behaviour of many materials in storage as well as in drying and freezing operations. Available data concerning phycocolloid gels, such as those of agar-agar and derivatives, are scarce in spite of their interest for pharmacology and the food industry. Thus, we have determined the isotherms of adsorption and desorption of agar-water gels by means of a gravimetric procedure, at 25, 40, 60 and 80 °C, determining the effect of temperature on the heat of desorption by the isosteric heat method, using the Henderson model. [ABSTRACT FROM AUTHOR]