Search

Per- and polyfluoroalkyl substances (PFAS) have concerned the public due to their worldwide distribution and the threat they pose to drinking water safety and human health. Temperature and DC field-induced electroosmotic flow (EOF) are powerful tools to regulate organic contaminant adsorption and control PFOS (as a typical PFAS) transport in porous media. However, the co-driven mechanisms of temperature–electrokinetic transport of contaminants are still unclear. Here, we investigated the synergistic mechanisms of temperature–electrokinetic co-driven PFOS adsorption on zeolite and activated carbon as model geo-adsorbents. We found that DC fields increased PFOS adsorption on activated carbon by up to 19.8%, while they decreased PFOS adsorption on zeolite by up to 21.4%. Increasing the temperature decreased the adsorption of PFOS by activated carbon and zeolite. The temperature and electrokinetic synergistically drive EOF velocity to control PFOS adsorption. Synergistic mechanisms of temperature–electrokinetic regulated kinetic and temperature-regulated thermodynamic (the Gibbs free energy change ΔG) and kinetic (liquid viscosity) under various temperatures and DC field situations were analyzed with models. A kinetic approach interlinking viscosity, EOF velocity, and the kinetic adsorption constants was established to interpret the synergistic mechanisms which can be further adopted to estimate temperature–electrokinetic induced PFOS adsorption benefits to mineral and carbonaceous adsorbents. We concluded that such kinetic regulation may provide support for controlling the transmission of PFOS.

Phosphoric acid-activated biochar has been proven to be a promising adsorbent for pollutant removal in an aqueous solution. It is urgent to understand how surface adsorption and intra-particle diffusion synergistically contribute to the adsorption kinetic process of dyes. In this work, we prepared a series of PPC adsorbents (PPCs) from red-pulp pomelo peel under different pyrolysis temperatures (150–350 °C), which have a broad specific surface area range from 3.065 m2/g to 1274.577 m2/g. The active sites on the surface of PPCs have shown specific change laws of decreasing hydroxyl groups and increasing phosphate ester groups occurring as the pyrolysis temperature rises. Both reaction models (PFO and PSO models) and diffusion models (intra-particle diffusion models) have been applied to simulate the adsorption experimental data to verify the hypothesis deduced from the Elovich model. PPC-300 exhibits the highest adsorption capacity of MB (423 mg/g) under given conditions. Due to its large quantities of active sites on the external and internal surfaces (1274.577 m2/g), a fast adsorption equilibrium can be achieved within 60 min (with an initial MB concentration of 100 ppm). PPC-300 and PPC-350 also exhibit an intra-particle-diffusion-controlled adsorption kinetic process with a low initial MB concentration (100 ppm) or at the very beginning and final stage of adsorption with a high initial MB concentration (300 ppm) at 40 °C, considering that the diffusion is likely hindered by adsorbate molecules through internal pore channels at the middle stage of adsorption in these cases.

The residual husks of the edible fruits of Psidium cattleianum were carbonized with FeCl3 as an activating agent and used as an adsorbent to remove the toxic herbicide. After the carbonization step, changes in the material’s structure were found. Activated carbon showed characteristics of microporous materials with a pore volume of 0.280 cm3 g−1 and surface area of 431 m2 g−1. Micrographs revealed the emergence of new cavities with a uniform and circular shape. The FTIR spectra showed the disappearance of some bands, remaining bands belonging to functional groups containing carbon, oxygen, and hydrogen. The XRD patterns confirmed the amorphous structure of the material even after the carbonization step, composed of amorphous graphitic carbon. EDS analysis showed that the carbon percentage increased and the oxygen decreased after the carbonization. The experiments were performed at neutral pH using 1 g L−1 of adsorbent. In equilibrium isotherms, the temperature played a considerable role in the adsorption capacity, increasing from 26.39 mg g−1 to 35.67 mg g−1 when the temperature varied from 298 to 328 K. The Liu isotherms were the ones that best fit the isotherm data. The changes in the adsorption enthalpy were endothermic (ΔH° 129.5 kJ mol−1). The general order kinetic model was the most adequate for kinetic data, presenting the lowest values of the Bayesian Information Criterion. Thus, activated carbon developed from the residues of the “araça” fruit showed promise in removing atrazine from aqueous solutions, with the great advantage of its high efficiency under neutral pH solutions and mild temperatures.

The magnetic nanoparticles maghemite were synthesized by the co-precipitation reaction and then used for the removal of hexavalent chromium from the synthetic aqueous stream. The maghemite nanoparticles were synthesized by the co-precipitation reaction of ferric and ferrous salts with oleic acid and into a water-in-oil micro emulsion using Sodium dioctyl sulfosuccinate surfactant. Dynamic light scattering and X-ray diffraction were used for the characterization of formed nanoparticles. The nanoparticles thus obtained were used as adsorbent for the adsorption of hexavalent chromium from the synthetic aqueous stream in a batch experiment and subsequently the adsorption kinetic mechanism of hexavalent chromium uptake was investigated. The uptake of hexavalent chromium was also found to be pH dependent. Experimental values of hexavalent chromium adsorption were fitted with Freundlich, Langmuir, Sips, Redlich-Peterson and Koble-Corrigan isotherms models. The best possible fits were yielded through five error functions. Adsorption thermodynamics was also studied.

In order to remove toxic graphene oxide (GO) from aqueous solution, attapulgite (ATP) was used as adsorbent to recycle it by adsorption. In this paper, the effects of different pH, adsorbent mass, GO concentration, time and temperature on the adsorption of GO by attapulgite were studied, and the adsorption performance and mechanism were further explored by XRD, AFM, XPS, FTIR, TEM and SEM tests. The results show that when T = 303 K, pH = 3, and the GO concentration is 100 mg/L in 50 mL of aqueous solution, the removal rate of GO by 40 mg of attapulgite reaches 92.83%, and the partition coefficient Kd reaches 16.31. The adsorption kinetics results showed that the adsorption equilibrium was reached at 2160 min, and the adsorption process could be described by the pseudo-second-order adsorption equation, indicating that the adsorption process was accompanied by chemical adsorption and physical adsorption. The isotherm and thermodynamic parameters show that the adsorption of GO by attapulgite is more consistent with the Langmuir isotherm model, and the reaction is a spontaneous endothermic process. The analysis shows that attapulgite is a good material for removing GO, which can provide a reference for the removal of GO in an aqueous environment.

The adsorption characteristics of chromium ions in chrome electroplating wastewater on low cost adsorbent have been conducted. Adsorbent was prepared from bovine bone waste of NaOH activated at various concentrations (0.2 to 0.8 M). Its adsorption such as adsorption isotherms and adsorption thermodynamics as well as adsorbent physico-chemical characteristics (surface active sites, crystallinity and crystal size, surface morphology and elementals composition). The result showed that amount of adsorbent surface active sites increased because of NaOH activated, the highest at 0.4 M NaOH concentration (AT0.4 adsorbent). X-ray diffraction patterns of the adsorbents showed a wide peaks and crystal size as nanocrystalline. The surface morfology was stack of aglomerates and leached of Ca and Mg due to increase Na. The adsorption result of adsorbents to chromium ions showed that the highest adsorption ability on AT0.4 adsorbent. It was suitable for Freundlich adsorption isotherm model as physical adsorption and endothermic but the tendency to be spontaneous process.

Textile wastewater discharged after the textile dyeing and finishing processes has become a concern for the environment. Textile industry uses various types of synthetic, mostly reactive dyes, and discharges enormous amounts of highly coloured waters. An adsorption process, as sustainable textile wastewater treatment method, is one of the most commonly used and effective method for removal of dyes from coloured water. This paper deals with isothermal adsorption of reactive dye Everzol Black B on commercial powdered activated carbon. Batch mode adsorption study was carried out at three different temperatures and different periods until equilibrium was reached. The residual liquid-phase dye concentration, amount of adsorbate adsorbed, and percentage of adsorbed dye were calculated after adsorption process. In order to investigate the mechanism of dye adsorption experimental data were analysed by two kinetic models. Based on the values of dye concentrations at equilibrium, thermodynamic parameters of adsorption were also determined.

Textile industry is considered to be one of the major environmental pollutants, primarily due to wastewaters quantity and composition. Wastewaters have a wide range of pH values and temperatures and mainly contain various types of pollutants, most commonly dyes, surfactants, solvents, inorganic salts etc. It is therefore necessary to treat the wastewaters by reducing the amount of harmful substances to legally limited concentrations. One of the most commonly used and effective methods of treating coloured water is adsorption, while one of the most often used adsorbent is activated carbon. In this paper, the effect of initial pH value (pH0 = 2.00, 4.00, 8.00 and 10.00) on the process of isothermal adsorption of Reactive Black 5 (RB5) dye on powdered activated carbon at 45(±1) °C was carried out. Adsorption experiments were performed at different contact times (15, 30, 60, 120 minutes and 16 hours until equilibrium is reached). In order to investigate the mechanism of adsorption kinetic studies have been also performed, using pseudo-first-order and pseudo-second-order kinetic models, as well as intraparticle diffusion model. Additional equilibrium experiments at temperatures of 29(±1), 35(±1) and 55(±1) °C at pH0 = 4.00 were also done in a wish to determine thermodynamic parameters of adsorption (standard Gibbs free energy, standard enthalpy and standard entropy changes). Results of this research showed that initial pH value significantly influences the adsorption of RB5 dye onto activated carbon. The highest adsorption capacities and efficiencies of decolouration (Ed) were observed for initial pH values of pH0 = 2.00 and 10.00 (Ed = 98.4 % and 95.6 %, respectively), while values for pH0 = 4.00 and 8.00 are much lower. High Ed values at pH0 = 2.00 can be explained by the strong electrostatic interactions between positively charged activated carbon surface and coloured anion of RB5 dye, while at pH0 = 10.00 by attractive Pi···Pi interactions. The experimental data also showed that adsorption at all pH0 values is kinetically controlled assuming a pseudo-second order process, and that intraparticle diffusion is not the only process that influences on the adsorption rate. Negative values of standard Gibbs free energy change indicated that the adsorption process is spontaneous, and that adsorption of RB5 on activated carbon at the highest temperature is energetically the most favourable. The positive value of standard enthalpy change revealed the endothermic nature of the adsorption process at pH0 = 4.00 and that hydrogen bonds are driving force for RB5 dye adsorption. The positive value of standard entropy change suggests the increased randomness in the dye-adsorbent interaction at the solid/liquid interface.

In this study seven adsorption azeotropes involving binary systems and zeolite-based adsorbents were systematically investigated. Pure component isotherms and mixed-gas adsorption data were taken from published literature except for the benzene–propene system on silicalite, which is newly presented in this work using molecular simulations. Experimental adsorbed phase composition and total amount adsorbed of the azeotropic systems were compared with the predictions of several models including: the ideal adsorbed solution theory (IAST), the heterogeneous ideal adsorbed solution theory (HIAST) and the real adsorbed solution theory (RAST) coupled with the 1-parameter Margules (1-Margules) and the van Laar equations. In the latter two models an additional loading parameter was incorporated in the expression of the excess Gibbs energy to account for the reduced grand potential dependency of the activity coefficients in the adsorbed phase. It was found that the HIAST and RAST–1-Margules models were able to predict the azeotropic behaviour of some systems with good accuracy. However, only the RAST–van Laar model consistently showed an average relative deviation below 3% compared to experimental data for both the adsorbed phase composition and the total amount adsorbed across the systems. This modified van Laar equation is therefore preferable in those engineering applications when the location of adsorption azeotropes is required with great accuracy and when there is lack of detailed characterization of the adsorbent that is needed to carry out molecular simulations.

The pace of industrialization and rapid population growth in countries such as India entail an increased input of industrial and sanitary organic micropollutants, the so-called emerging contaminants (EC), into the environment. The emission of EC, such as pharmaceuticals, reaching Indian water bodies causes a detrimental effect on aquatic life and ultimately on human health. However, the financial burden of expanding sophisticated water treatment capacities renders complementary, cost-efficient alternatives, such as adsorption, attractive. Here we show the merits of washed and milled pigeon pea husk (PPH) as low-cost adsorbent for the removal of the EC trimethoprim (TMP) and atenolol (ATN) that are among the most detected pharmaceuticals in Indian waters. We found a linear increase in adsorption capacity of PPH for TMP and ATN at concentrations ranging from 10 to 200 μg/L and from 50 to 400 μg/L, respectively, reflecting the concentrations occurring in Indian water bodies. Investigation of adsorption kinetics using the external mass transfer model (EMTM) revealed that film diffusion resistance governed the adsorption process of TMP or ATN onto PPH. Moreover, analysis of the adsorption performance of PPH across an extensive range of pH and temperature illustrated that the highest adsorption loadings achieved concurred with actual conditions of Indian waters. We anticipate our work as starting point towards the development of a feasible adsorbent system aiming at low-cost water treatment., Molecules, 26 (11), ISSN:1420-3049

In recent years, there has been significant interest in the study of spandex in high-elasticity sensors. As a new kind of special spandex, dyeable spandex shows strong adsorption capacity for anions. In this study, neutral red G was used as an anion adsorption simulator to study the adsorption mechanism of dyeable spandex on anionic materials. The structure of dyeable spandex was characterized by the modern instrumental analysis method, and the adsorption kinetics and thermodynamics of neutral red G on dyeable spandex were discussed. The results show that the use of mixed amines as chain extenders for dyeable spandex reduced the regularity of molecules and the crystallinity of spandex, which was beneficial to the diffusion adsorption of anions. On the other hand, the number of secondary amino groups increased, providing more adsorption sites under acidic conditions. The adsorption of neutral red G on dyeable spandex satisfied the quasi-second-order kinetics and the Langmuir adsorption model, indicating that dye adsorption on spandex was mainly electrostatic. The diffusion coefficient and equilibrium adsorption capacity of neutral red G on dyeable spandex increased significantly, whereas enthalpy and entropy decreased.

Bu çalışmada Cu(II), Ni(II), ve Co(II) iyonlarını sulu çözeltiden gidermek için adsorplayıcı olarak, ucuz maliyetli Karacadağ Skoryası (BR1) kullanıldı. BR1; XRD, XRF, FT-IR, BET ve SEM gibi yöntemlerle karekterize edildi. BR1'in irili ufaklı gözenek hacimlerinin, toplam hacmin yarısını bulduğu görüldü. Elde edilen denge verileri Langmuir, Freundlich,Temkin ve Dubinin Radushkevich (D-R) adsorpsiyon modellerine, kinetik veriler ise; yalancı-birinci dereceli model, yalancı-ikinci dereceli model (Ho ve McKay modeli), Weber-Morris ve Elovich modellerine uygulandı. Regresyon analizleri sonucu; denge çalışmaları için Langmuir Modeli, kinetik çalışmaları için ise yalancı-ikinci dereceli model, en uygun modeller olarak bulundu. Cu(II) iyonu 298,313 ve 328 K sıcaklıklarında yapılan adsorpsiyon deneylerinde qm değeri sırasıyla 1,83, 2,23 ve 3,09 mgg-1, 298 313 v3 323 K sıcaklıklarında elde edilen qm değerleri Ni(II) için; 0,73, 1,31 ve 1,80 mgg-1, Co(II) için 0,56, 0,93 ve 1,36 mgg-1 olarak bulundu. Termodinamik çalışmalarda Cu(II) iyonu için 298,313 ve 328 K sıcaklıklarında ΔG değerleri sırasıyla -13,37 -17,12 ve -20,86 kJmol-1; 298,313 ve 323 K sıcaklıklarında ΔG değerleri Ni(II) iyonları için sırasıyla -11,55 -15,07 ve -17,41, Co(II) iyonları için sırasıyla -10,36 -14,72 ve -17,63 kJmol-1 olarak bulundu. Cu(II), Ni(II) ve Co(II) için ΔH değerleri sırasıyla 61,04 58,3 ve 76,36 kJmol-1 olarak bulundu. ΔS değerleri de yine sırasıyla 0,2497 0,2344 ve 0,2910 kJmol-1K-1 olarak bulundu. Termodinamik çalışmalarda ΔH değerlerinin pozitif değerli oluşu; adsorpsiyon olayının endotermik olduğunu ve ΔG değerlerinin negatif oluşu ise olayın kendiliğinden cereyan ettiğini gösterdi. In this study, to remove copper(II), Ni(II) and Co(II) ions from aqueous solutions low-cost Karacadağ scoria were used. BR1 was characterized by XRD, XRF, FT-IR BET and SEM methods. It was observed that the large and small pore volumes of BR1 amounted to half of the total volume. The equilibrium data obtained are were applied Langmuir, Freundlich, Temkin and Dubinin Radushkevich (D-R) adsorption models, and the kinetic data were also applied to pseudo-first order model, pseudo-second order model (Ho and McKay model), Weber-Morris and Elovich models. As a result of regression analyzes; Langmuir Model for equilibrium studies and pseudo-second model for kinetic studies were found to be the most suitable models. Maximum adsorption capacity of Cu(II), Ni(II) and Co(II) ions were determined as 1,83, 2,23 and 3,09 mgg-1 ; 0,73, 1,31 and 1,80 mgg-1 0,56, 0,93 and 1,36 mgg-1 at 298,313 and 328 K for copper, 298,313 and 323 K respectively. Thermodynamic parameters such as free energy, entalpy and entropy for adsorption Cu(II), Ni(II) and Co(II) ions onto BR1 are determined as -13,37 -17,12 and -20,86 ; -11,55 -15,07 and -17,41; -10,36 -14,72 ve -17,63 kJmol-1 for free energy (∆G), 61,04 58,3 ve 76,36 kJmol-1 for entalpy, 0,2497 0,2344 ve 0,2910 kJmol-1K-1 for entropy. The positive value of ΔH in thermodynamic studies showed that The adsorption event was endothermic, also the negative ΔG values showed that the event occurred spontaneously.

International audience; The gelation of a low value-added industrial waste, phenolic oil (PO), was successfully carried out for the first time in the presence of an acid catalyst and paraformaldehyde (PF), which is a by-product of the formaldehyde industry. Therefore, the use of PO and PF can be considered a win-win situation and as an attempt to valorise these 'wastes' and integrate them into a circular economy. A broad range of formulations has been explored, and the optimal preparation conditions in terms of materials' homogeneity and yield have been identified for gels dried in different ways, leading to xerogels, cryogels and aerogels, as well as to their carbonaceous counterparts after pyrolysis at 900°C. The porous textures of the latter materials were studied in depth, and the results allowed selecting one carbon xerogel for adsorption studies of a reference molecule, methylene blue (MB), in the aqueous phase. Kinetic and equilibrium measurements, as well as the calculation of associated thermodynamic parameters, allowed elucidating the detailed adsorption mechanisms of MB in this type of carbon gel.

The sustainable development of society implies the adoption of strategies related to waste management and valorization (in a circular economy perspective) and to effluent treatment (namely for the removal of pharmaceuticals from water). Being adsorption by activated carbon (AC) a well-established method for water treatment, this work focuses on the production of AC using residues, namely sludge from pulp and paper industry, for the removal of pharmaceuticals from water. This approach aims to foster an integrated solution for the two environmental issues involved in this work. Primary pulp and paper mill sludge (PS) showed a great potential to produce carbon-based adsorbents, relatively to biological sludge (BS). Through the use of PS and a production process involving chemical activation and pyrolysis, it was possible to produce AC in both powdered and granular (using a binder agent) forms, with high surface areas (SBET) (similar to those of commercial AC with the same granulometry). The produced powdered AC presented, in batch adsorption systems, adsorption capacities for the pharmaceuticals carbamazepine (CBZ), sulfamethoxazole (SMX) and paroxetine (PAR), in the same magnitude of commercial AC. However, when applied in wastewater matrix, variations in the adsorption capacity of the produced AC for the studied pharmaceutical was observed, namely in the case of SMX, which decreased, and PAR, that increased. The produced granular AC showed, in batch adsorption systems, lower adsorption capacity for the three pharmaceuticals CBZ, SMX, and PAR, than the commercial granular AC used as reference. Also, in this case, a reduction in the adsorption capacity for CBZ and SMX was observed for wastewater matrices. In fixed-bed column studies (continuous mode) the produced granular AC presented a higher breakthrough volume and adsorption capacity for CBZ for the lower flow-rate. Also, it was observed a reduction of the adsorption capacity with the increase of the complexity of the aqueous matrix (distilled water > wastewater > multicomponente solutions – with the three pharmaceuticals – in wastewater). The application of different functionalization methods to the powdered AC surface showed to be an interesting approach, evidencing an increase in the selectivity of some functionalized AC for some of the pharmaceuticals under study, despite the general reduction in their SBET. Concluding, this work demonstrates the potential of PS from pulp and paper mill industry to produce alternative AC, particularly in the powdered form, to be applied in the removal of pharmaceuticals from water. O desenvolvimento sustentável da sociedade implica a adoção de estratégias ligadas à gestão dos resíduos e sua valorização (numa perspetiva de economia circular) e ao tratamento de efluentes (nomeadamente, para a remoção de fármacos da água). Sendo o processo de adsorção por carvão ativado (CA) um método bem estabelecido para o tratamento de águas, este trabalho incide sobre a produção de CA a partir de resíduos, nomeadamente lamas da indústria da pasta e do papel, para a remoção de fármacos da água. Esta abordagem pretende proporcionar uma solução integrada nos dois desafios ambientais anteriormente referidos. Comparativamente com as lamas biológicas (LB), as lamas primárias (LP) da indústria da pasta e do papel, mostraram ter um grande potencial para a produção de adsorventes à base de carvão. A partir de LP, e usando um processo de ativação química e pirólise, foi possível produzir CA, quer na forma de pó, quer na forma granular (usando um agente aglomerante) com elevadas áreas superficiais (SBET) (comparáveis às de CA comerciais da mesma granulometria). Os CA produzidos em pó apresentaram, em sistemas descontínuos de adsorção, capacidades de adsorção para os fármacos carbamazepina (CBZ), sulfametoxazol (SMX) e paroxetina (PAR), da mesma ordem de grandeza que os CA comerciais. Contudo, quando aplicados em matrizes de efluente real, observam-se variações na capacidade de adsorção dos CA produzidos para os fármacos em estudo, principalmente no caso do SMX, que diminuiu, e da PAR, que aumentou. O CA granular produzido apresentou, em sistemas descontínuos de adsorção, menor capacidade de adsorção para os três fármacos CBZ, SMX e PAR, do que o CA granular comercial de referência. Também neste caso, se verificou uma redução da capacidade de adsorção da CBZ e do SMX em matrizes de efluente real. Estudos realizados em colunas de leito-fixo (modo contínuo) mostraram que o CA granular produzido apresentou maior volume de rutura e maior capacidade de adsorção da CBZ para o menor fluxo. Verificou-se, ainda, a redução da capacidade de adsorção com o aumento da complexidade da matriz aquosa (água destilada > efluente real > soluções multicomponente - com os três fármacos - em efluente). A aplicação de diferentes metodologias de modificação ou funcionalização da superfície dos CA em pó mostrou ser uma abordagem interessante, observando-se um aumento de seletividade de alguns CA funcionalizados para alguns dos fármacos em estudo, apesar da redução geral da SBET destes. Em suma, este trabalho demonstra o potencial das LP da indústria papeleira para a produção de CA alternativos aos CA comerciais, em particular para a formulação em pó, e para a sua aplicação na remoção de fármacos das águas. Programa Doutoral em Química

Process chromatography modelling for process development, design, and optimization as well as process control has been under development for decades. Still, the discussion of scientific potential and industrial applications needs is open to innovation. The discussion of next-generation modelling approaches starting from Langmuirian to steric mass action and multilayer or thermodynamic consistent real and ideal adsorption theory or colloidal particle adsorption approaches is continued.

As indústrias químicas ligadas à agricultura e pecuária, desenvolveram diversos produtos químicos para a utilização no ambiente, entre os quais encontram-se substâncias que possuem atividade de desregulação endócrina. Nesse contexto destaca-se o herbicida glifosato (GLF), que está entre os quatro agroquímicos mais utilizados no Brasil (glifosato e seus sais; 2,4-D; acefato; óleo mineral) sendo empregado principalmente, na cultura de soja e cana-de-açúcar. A principal fonte de exposição do glifosato para os organismos vivos é a ingestão de água, visto que os sistemas convencionais de tratamento de água e efluentes, não são capazes de remover ou degradar por completo uma série de compostos orgânicos sintéticos. Nessa conjuntura faz-se necessário a utilização de métodos complementares de tratamento, dos quais a adsorção pode ser de interesse técnico e ambiental, devido sua eficiência e, principalmente, na versatilidade de matérias primas utilizadas para produção de material adsorvente. Desta forma, o objetivo desse estudo foi o reaproveitamento de sabugo de milho por meio da produção de biocarvão (BC) e carvão ativado (CA), para potencial remoção do herbicida glifosato (GLF) (formulação comercial) em meio aquoso por meio da técnica de adsorção. O BC foi submetido apenas a etapa de carbonização já o CA foi sujeito a carbonização seguido de ativação química com H3PO4.Os adsorventes foram caracterizados por análises de difração de raios X (DRX) e de infravermelho por transformada de Fourier (FTIR), adsorção e dessorção de N2, microscopia eletrônica de varredura (MEV) e determinação do potencial de carga zero (pHPCZ). O efeito do pH inicial e da massa de adsorvente também foi avaliado. Os estudos cinéticos de adsorção foram ajustados aos modelos de pseudoprimeira e pseudosegunda ordem. A natureza do processo de adsorção foi estudada por meio dos modelos de isoterma de Langmuir e Freundlich, e os parâmetros termodinâmicos calculados para as temperaturas de 23, 43 e 63°C. O tratamento ácido provocou o aumentou da área superficial (7,48 m²/g BC para 34,126 m²/g CA) favorecendo a formação de mesoporos e pouco influenciou nas cargas superficiais. A adsorção de GLF mostrou-se altamente dependente do pH e ambos adsorventes atingiram sua capacidade máxima de adsorção em pH neutro (7,0). Ambos adsorventes atingiram o equilíbrio em 60 min de ensaio, sendo que em apenas 15 min o CA atinge 93% da sua capacidade máxima de adsorção e o BC 68%, apresentando melhor ajuste ao modelo de pseudo-segunda ordem. Os dados de equilíbrio obtidos experimentalmente, para as temperaturas de 23, 43 e 63 °C, apresentaram melhor ajuste ao modelo de Langmuir para o BC indicando quimissorção, e de Freundlich para o CA indicando Fisissorção. A ativação química elevou a capacidade máxima de adsorção (qmax de Langmuir) de 1,08 mg g-1 para 1,51 mg g-1. Os valores das constantes termodinâmicas, revelaram que a adsorção de GLF é de natureza endotérmica, favorecida com o aumento da temperatura (ΔH>0), e endergônica (ΔG > 0), indicando que o processo de adsorção não é espontâneo. Like the chemical industries applied to agriculture and livestock, they develop several chemicals for use in the environment, including chemicals that can be used for endocrine disrupting activities. In this context, the use of the herbicide Glyphosate (GLF), which is among the four most used agrochemicals in Brazil (glyphosate and its salts; 2,4-D; Acephate; mineral oil) is the main used, soybean and sugar cane. The main source of exposure of glyphosate to living organisms is a water intake, since water and wastewater treatment systems are not able to remove or degrade by a complete series of synthetic organic compounds. In this situation, it is necessary to use complementary treatment methods, of which adsorption may be of technical and environmental interest, due to its efficiency and, mainly, in the versatility of raw materials used for the production of material adsorbent. Thus, the objective of this study was the reuse of corn maize through the production of biochar (BC) and activated carbon (CA), for potential removal of glyphosate herbicide (GLF) (commercial use) in aqueous medium using the technique of adsorption. The BC was subjected to only the carbonization step, while the CA was subjected to carbonization followed by chemical activation with H3PO4. The adsorbents were characterized by X-ray diffraction (DRX) and infrared analysis by Fourier transform (FTIR), adsorption and N2 desorption, scanning electron microscopy (SEM) and determination of the zero charge potential (pHPCZ). The effect of the initial pH and the adsorbent mass was also evaluated. The kinetic studies of adsorption were adjusted to the models of pseudo-first and pseudo-second order. The nature of the adsorption process was studied using the Langmuir and Freundlich isotherm models, and the thermodynamic parameters calculated for the temperatures of 23, 43 and 63 ° C. The acid treatment caused an increase in the surface area (7.48 m² / g BC to 34.126 m² / g CA) favoring the formation of mesopores and had little influence on the surface loads. The adsorption of GLF proved to be highly dependent on pH and both adsorbents reached their maximum adsorption capacity at neutral pH (7.0). Both adsorbents reached equilibrium in 60 min of testing, and in just 15 min the CA reaches 93% of its maximum adsorption capacity and the BC 68%, showing a better fit to the pseudo-second model. indicating a tendency for chemical adsorption. The equilibrium data obtained experimentally, for temperatures of 23, 43 and 63 ° C, showed a better fit to the Langmuir model for the BC indicating chemisorption, and Freundlich for the CA indicating Fisissorection. Chemical activation increased the maximum adsorption capacity (Langmuir qmax) from 1.08 mg g-1 to 1.51 mg g-1 The values of the thermodynamic constants revealed that the adsorption of GLF is endothermic in nature, favored with the increase in temperature (ΔH> 0), and endergonic (ΔG> 0), indicating that the adsorption process is not spontaneous. Outro

Adsorption refrigeration has become an attractive technology due to the capability to exploit low-grade thermal energy for cooling power generation and the use of environmentally friendly refrigerants. Traditionally, these systems work with pure fluids such as water, ethanol, methanol, and ammonia. Nevertheless, the operating conditions make their commercialization still unfeasible, especially owing to safety and cost issues as a consequence of the working pressures, which are higher or lower than 1 atm. The present work represents the first thermodynamic insight in the use of mixtures for adsorption refrigeration and aims to assess the performance of a binary system of ammonia and ethanol. According to the Gibbs’ phase rule, the addition of a component introduces an additional degree of freedom, which allows to adjust the pressure of the system varying the composition of the mixture. The refrigeration process was simulated with isothermal- isochoric flash calculations to solve the phase equilibria, described by the Peng-Robinson-Stryjek-Vera (PRSV) equation of state for the vapor and liquid phases and by the ideal adsorbed solution theory (IAST) and the multicomponent potential theory of adsorption (MPTA) for the adsorbed phase. In operating condenser and evaporator, pressure levels around atmospheric pressure can be achieved using an ammonia/ethanol mixture with a mole fraction of ethanol in the range of 0.70−0.75. A good agreement in the predictions of the adsorbed phase composition was also reported using the IAST and the MPTA methods.

Four slow pyrolyzed biochars produced from wood (WDB), corncobs (CCB), rice husks (RHB) and sawdust (SDB) were evaluated for adsorption, desorption and regeneration of phosphate (PO4 3−-P) from anaerobically digested liquid swine manure. The PO4 3−-P adsorption capacity increased followed by initial concentrations increasing. Maximum PO4 3−-P adsorptions at initial 150 mg/L of PO4 3−-P (highest load) were average of 7.67, 6.43, 5.73 and 5.41 mg/g for WDB, CCB, RHB and SDB, respectively. Pseudo second order kinetics model could best fit PO4 3−-P adsorption, which indicated the chemisorption via precipitation was the main mechanism for PO4 3−-P removal. The sorption process was reversible and the adsorbed PO4 3−-P could be desorbed in both neutral (57–78%) and acidic solution environments (75–88%) for all biochars. Meanwhile, regenerated biochar could re-adsorb up to 5.62 mg/g at the highest initial PO4 3−-P of 150 mg/L. The present finding implied biochar could be effectively used to recover PO4 3−-P from anaerobic digestate.

Bare, uncoated magnetite nanoparticles, synthesized using an electrochemical surfactant-free synthesis, have highly oxidized surfaces that prevent aggregation. These particles have demonstrated highly intriguing biological activity showing extremely potent antibiotic activity against both gram-positive and gram-negative bacteria with little toxicity to rats. This difference in activity could be ascribed to the nature of the protein corona. The kinetics and thermodynamics of the binding of bovine serum albumin (BSA), used as a model serum protein, to these magnetite nanoparticles were analyzed. There is no significant change in particle diameter by dynamic light scattering following adsorption, indicating corona formation does not induce aggregation. The maximum adsorption capacity of the particles was determined to be 300 mg of BSA per gram of magnetite. The particles are able to adsorb 90% of the BSA at protein concentrations as high as 500 mg/L. The adsorption is best described using a pseudo second order model and a Langmuir Type III isotherm model. Thermodynamic analysis showed that the process is entropically driven and is spontaneous at all tested temperatures and conditions. However, it appears to be a weak to moderate physical adsorption. This moderate binding affinity could indicate the differential biological activity of these particles towards bacteria and mammalian cells and further support the contention that these are potentially useful new tools for targeting antibiotic-resistant bacteria.

Bu çalışmada, bitkisel tabaklanmış deri tıraş atıklarının deri sanayi atık suyunda bulunan üç değerlikli kromun giderilmesinde adsorban olarak kullanılabilirliği araştırılmıştır. Adsorban miktarı, süre ve pH'ın Cr(III) adsorpsiyonu üzerine etkileri araştırılarak, optimum koşullar belirlenmiştir. Ayrıca deri tıraş atıkları-krom adsorpsiyonuna ilişkin izoterm, kinetik ve termodinamik çalışmalar yapılmıştır. Sonuçlara göre elde edilen verilerin Langmuir izotermine uyduğu gözlenmiş ve maksimum adsorpsiyon kapasitesi 10,24 mg/g, Langmuir sabiti ise 0,100 L/g olarak bulunmuştur. Kinetik çalışmalara göre, adsorpsiyonun, Pseudo-2. mertebe Lagergren hız denklemi modeline uygun olduğu, adsorpsiyon termodinamiği incelendiğinde, adsorpsiyonun endotermik olduğu, adsorpsiyon sırasında katı/çözelti ara yüzeyinde düzensizliğin arttığı ve adsorpsiyonunun kendiliğinden gerçekleştiği tesbit edilmiştir. Bu sonuçlar, bitkisel tabaklanmış deri tıraş atıkları üzerinde krom adsorpsiyonun fiziksel ve kimyasal yolla gerçekleşen karmaşık bir süreç olduğunu göstermektedir., In this work, usability of vegetable tanned leather shavings as an adsorbent to remove Cr(III) of heavy metal ions from effluent of leather industry was investigated. Optimum conditions were determined by investigating the effects of adsorbent amount, time, pH and temperature on Cr(III) adsorption. Furthermore, kinetic, isotherm and thermodynamics studies were performed related to adsorption between leather shavings and chromium. According to findings the data fit to Langmuir isotherm with Langmuir constant of 0,100 L/g and with 10,24 mg/g maximum adsorption capacity. When adsorption kinetic was investigated, it was found out that the data fit to Lagergren pseudo 2. order kinetic model. In terms of thermodynamic results show that the adsorption phenomenon was endothermic, so that the randomness of solid-solution interface increased during the adsorption and the adsorption happened spontaneously. These results show that Cr(III) adsorption on vegetable tanned leather shavings is a complex process taking place in physical and chemical ways.

This work is focused on the investigation of the mechanism (isotherm), nature/strength (thermodynamics) and rate (kinetics) of CO2 adsorption on a commercial activated carbon in a sound assisted fluidized bed. Langmuir and Freundlich equations were used to model the CO2 adsorption isotherm in the low pressure region (i.e. typical of a combustion flue gas). Then, adsorption behaviour was elucidated by energy function such as standard Gibbs free energy, enthalpy and entropy. The isosteric heat of adsorption was also evaluated. Finally, this study also presented a kinetic analysis of CO2 adsorption, from which CO2 binding on activated carbon was deduced to follow pseudo-first order kinetic.

We present a molecular theory to study the adsorption of different species within pH-sensitive hydrogel nanofilms. The theoretical framework allows for a molecular-level description of all the components of the system, and it explicitly accounts for the acid-base equilibrium. We concentrate in the adsorption of hexahistidine, one of the most widely used tags in bio-related systems, particularly in chromatography of proteins. The adsorption of hexahistidine within a grafted polyacid hydrogel film shows a non-monotonic dependence on the solution pH. Depending on the salt concentration, the density of the polymer network, and the bulk concentration of peptide, substantial adsorption is predicted in the intermediate pH range where both the network and the amino acids are charged. To enhance the electrostatic attractions, the acid-base equilibrium of adsorbed hexahistidine is shifted significantly increasing the degree of charge of the residues, as compared to the bulk solution. Such shift depends critically on the conditions of the environment at the nanoscale. At the same time, the degree of dissociation of the network becomes that of the isolated acid-group in a dilute solution, which means that the network is considerably more charged than when there is no adsorbate molecules. This work provides fundamental information on the physical chemistry behind the adsorption behavior and the response of the hydrogel film. This information can be useful in designing new materials for the purification or separation/immobilization of histidine-tagged proteins. Fil: Longo, Gabriel Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina Fil: Olvera de la Cruz, Monica. Northwestern University; Estados Unidos Fil: Szleifer, Igal. Northwestern University; Estados Unidos

The ideal adsorbed solution theory (IAST) is the most widespread theory for multicomponent adsorption interpretation. It postulates the existence of an adsorbed phase which behaves as a Raoult ideal solution. The theory results in a system of nonlinear algebraic equations which are solved to know the composition of the adsorbed mixture at equilibrium. In this paper an investigation on an alternative method for the IAST equations solution is proposed which is based on the minimisation of an objective function representing the iso-spreading pressure condition. This approach to the solution of the IAST equations reduces in some cases the computational effort and mitigates the issues of the currently adopted approaches (inversion of functions and initial guess). For binary systems, direct search minimisation approach is faster than the classic IAST equations solution approach up to 19.0 (Dual Langmuir isotherm) and 22.7 times (Toth isotherm). In ternary systems, this difference decreases to 10.4 (O'Brien and Myers isotherm) times. Compared to FASTIAS approach, direct search minimisation is up to 4.2 times slower in ternary systems. (C) 2014 Elsevier Ltd. All rights reserved.

Nano-Mg(OH)2, with low biological toxicity, is an ideal nano-carrier for insecticidal protein to improve the bioactivity. In this work, the adsorption features of insecticidal protein by nano-Mg(OH)2 have been studied. The adsorption capacity could reach as high as 136 mg g−1, and the adsorption isotherm had been fitted with Langmuir and Freundlich models. Moreover, the adsorption kinetics followed a pseudo-first or -second order rate model, and the adsorption was spontaneous and an exothermic process. However, high temperatures are not suitable for adsorption, which implies that the temperature would be a critical factor during the adsorption process. In addition, FT-IR confirmed that the protein was adsorbed on the nano-Mg(OH)2, zeta potential analysis suggested that insecticidal protein was loaded onto the nano-Mg(OH)2 not by electrostatic adsorption but maybe by intermolecular forces, and circular dichroism spectroscopy of Cry11Aa protein before and after loading with nano-Mg(OH)2 was changed. The study applied the adsorption information between Cry11Aa and nano-Mg(OH)2, which would be useful in the practical application of nano-Mg(OH)2 as a nano-carrier.

Amine-modified bentonite (TEPA-Bn) has been prepared with tetraethylenepentamine (TEPA) as a modifier. The structure of Ca-based bentonite (Ca-Bn), TEPA-Bn and TEPA-Bn after adsorbing Cu 2+ ,Ni 2+ ,Cd 2+ had been characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and simultaneous thermal gravimetric/differential thermal gravimetric (TG/DTG) analysis. The TEPA had been intercalated into Ca-Bn interlayer space but had not changed its original crystal structure. The thermal stability of TEPA-Bn was stronger than Ca-Bn while the hydrophilicity of it reduced. The adsorption ability of TEPA-Bn to Cd 2+ , Ni 2+ , Cu 2+ was much better than Ca-Bn, the saturated adsorption capacity to Cd 2+ , Ni 2+ , Cu 2+ were 14.88, 8.88 and 13.05 times as much as Ca-Bn, respectively. The adsorption behavior of Cu 2+ , Ni 2+ , Cd 2+ on to TEPA-Bn were studied by isothermal models, including Freundlich, Langmuir, Dubinin-Radushkevich Florry-Huggins, and Tempkin models. The Freundlich model simulated the experimental data best, the adsorption of Cu 2+ , Ni 2+ , Cd 2+ onto TEPA-Bn was a multilayer, heterogeneous chemical process. The variety of thermodynamic parameters (DH > 0, DS > 0, DG < 0) under different temperature indicated that the adsorption process of Cu 2+ , Ni 2+ , Cd 2+ on TEPA-Bn was endothermic and spontaneous. KEY WORDS : Amine-modified bentonite, TEPA, Heavy metal ions, Adsorption thermodynamics, Characterization Bull. Chem. Soc. Ethiop. 2016 , 30(3), 357-367 DOI: http://dx.doi.org/10.4314/bcse.v30i3.4

Nano-Mg(OH) 2 , with low biological toxicity, is an ideal nano-carrier for insecticidal protein to improve the bioactivity. In this work, the adsorption features of insecticidal protein by nano-Mg(OH) 2 have been studied. The adsorption capacity could reach as high as 136 mg g −1 , and the adsorption isotherm had been fitted with Langmuir and Freundlich models. Moreover, the adsorption kinetics followed a pseudo-first or -second order rate model, and the adsorption was spontaneous and an exothermic process. However, high temperatures are not suitable for adsorption, which implies that the temperature would be a critical factor during the adsorption process. In addition, FT-IR confirmed that the protein was adsorbed on the nano-Mg(OH) 2 , zeta potential analysis suggested that insecticidal protein was loaded onto the nano-Mg(OH) 2 not by electrostatic adsorption but maybe by intermolecular forces, and circular dichroism spectroscopy of Cry11Aa protein before and after loading with nano-Mg(OH) 2 was changed. The study applied the adsorption information between Cry11Aa and nano-Mg(OH) 2 , which would be useful in the practical application of nano-Mg(OH) 2 as a nano-carrier.

The adsorption isotherms and structural evolution of alkyl quaternary ammonium bromide (C n TAB) on graphite oxide (GO) were measured by means of an elemental analyzer, X-ray diffraction and Fourier transform infrared spectroscopy. In order to interpret the adsorption mechanism of surfactants onto GO, the adsorption kinetics and thermodynamics were further investigated. It was found that GO is a relatively efficient adsorbent within a wide range of temperatures (297–353 K), and the C n TAB was intercalated and then agglomerated into the interlayer spacing of GO via ionic bonding and hydrophobic bonding. The saturation amount of alkyl ammonium adsorbed on GO was decreased with the rise in temperature, and the experimental data fitted well into the modified Langmuir (Langmuir-Freundlich) equation. In addition, the negative values of ΔG and ΔH showed that the adsorption process of C n TAB onto the GO was spontaneous and exothermic.

Pyridine is a toxic component in industrial wastewater, which is difficult to remove using conventional methods. In this study, the cost-effective coke powder was used to remove pyridine from a pyridine simulation wastewater. The removal efficiency and adsorption capacity of pyridine reached up to 67.32% and 0.4488 mg/g, respectively, at a coke powder concentration of 60 mg/L and an adsorption time of 30 min. The pyridine removal efficiency and adsorption capacity of coke powder reached saturation when the initial concentration was 40 mg/L. The pH of 2&ndash, 12 in the solution was found to have little effect on the pyridine adsorption process of coke powder, while the coke powder with lower ash content was of better adsorbability for pyridine. The coke powder was regenerated by heat treatment, and reused for pyridine adsorption. It was found that the pyridine removal efficiency slightly decreased after nine times of reuse, in addition to a small cumulative weight loss rate of coke powder. Adsorption isotherm analysis showed that the adsorption of pyridine by coke powder could be well described by the Freundlich isothermal adsorption model, indicating multi-molecular layers mainly dominated the adsorption of pyridine on the surface of coke powder.

This study presents the kinetic and thermodynamic investigation of the adsorption of crystal violet (CV) on used black tea leaves (UBTL) from aqueous solution to evaluate the feasibility of the process. The effects of concentration, solution pH and temperature on adsorption kinetics were carried out in batch process. Kinetic studies have shown that the adsorption data partially follow simple first order, second order and pseudo second order kinetic equations for different initial concentrations at pH 2.0. The equilibrium amount adsorbed, equilibrium concentration and rate constant were calculated from better fitted pseudo second order kinetic plots for different initial concentrations. The equilibrium amount adsorbed (200 mg/g at 30 oC) increased with the increase of temperature, indicated endothermic nature of the adsorption. The apparent activation energy of adsorption was determined from Arrhenius plot using pseudo second order rate constant and the value, Ea = 83.1 kJ/mol, revealed the process is chemisorption. Thermodynamic parameters: DHo, DGo and DSo, were determined from the equilibrium adsorption constant and the results obtained confirmed that the adsorption process was feasible, less spontaneous and endothermic. The equilibrium amount adsorbed was found to be increased with increase of solution pH from 2.0 to 6.0 indicating electrostatic interaction between cationic CV with anionic surface of UBTL dominated at higher pH due to the low zero point charge of pH of UBTL.

In this study, asparagine functionalized magnetic nanoparticles (Fe3O4-Aspa) were prepared and characterized by fourier transform infrared spectroscopy, x-ray diffractometer, scanning electron microscopy, transmission electron microscopy, vibrational sampling magnetometer and pHzpc. The functionalized magnetic nanoparticles were applied for Ni(II) adsorption by batch adsorption technique under different variable factors such as temperature, pH, contact time, adsorbent dosage etc. The study indicates that the adsorption reaction has fast kinetics with applied pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich model. The pseudo-second order model found to be best linear fit with experimental data of Ni(II) adsorption. The high correlation coefficient (R2) of 0.996, 0.998, 0.998 and 0.999 at 20, 40, 60 and 80 mg l−1 of aqueous solution reveal that the pseudo-second order model is suitable for Ni(II) ions adsorption. The effect of contact time on Ni(II) adsorption has described that solution equilibrium was achieved within 70 min at optimized pH 6. The experimental adsorption capacity values were applied to Langmuir and Freundlich isotherm model and found satisfactory result through best linear fitting of Langmuir isotherm model with high R2 of 0.999, 0.998 and 0.996 at 303, 308, and 313 K, respectively. The adsorption thermodynamics of parameters are found to be as 344.087 (kJ mol−1), 101.583 (kJ mol−1 K−1) and 1.640–1.172 (kJ mol−1), respectively at ΔH°, ΔSº and ΔGº which indicates that the adsorption process is spontaneous with exothermic nature. © 2016 Taiwan Institute of Chemical Engineers

In this study, magnetite nano-particles (Fe3O4, MNPs) were synthesized by chemical co-precipitation method and characterized by FTIR, TEM and VSM methods at first. After that, some adsorption experiments were performed for removal of hexavalent chromium [Cr(VI)] ions from aqueous media by MNPs. Finally, thermodynamic and kinetic properties of Cr(VI) adsorption on MNPs were investigated. Mean particle size and magnetization saturation (Ms) of synthesized MNPs were about 15 nm and be 75 emug-1, respectively. Under optimum adsorption conditions, capacity and removal percentage of Cr(VI) adsorption were found to be 33.45 mg/g and 88%, respectively. According to calculated thermodynamic parameters after adsorption experiments, Cr(VI) adsorption process was a result of endothermic reactions. Langmuir and Freundlich isotherm models were investigated and it was observed that the removal of Cr(VI) could be better described by the Langmuir model. Kinetic investigations showed that the pseudo-second-order model have a better description of the Cr(VI) adsorption., Bu çalışmada, hekzavalent krom [Cr(VI)] iyonlarının manyetit nano-partikülleri (Fe3O4, MNP) ileadsorpsiyonu prosesinin kinetik ve termodinamik özelliklerinin araştırılması amaçlanmıştır. Bu amaçdoğrultusunda, ilk olarak kimyasal ikili çöktürme tekniği kullanılarak MNP sentezlendi ve elde edilen ürünlerFTIR, TEM ve VSM gibi metotlar ile karakterize edildi. Daha sonra, sulu ortamdan Cr(VI) iyonlarınıngiderilmesi için MNP ile bir dizi adsorpsiyon deneyleri yapıldı. Son olarak da Cr(VI) iyonlarının MNP ileadsorpsiyonu prosesinin kinetik ve termodinamik çalışmaları yapıldı. Sentezlenen nano-partiküllerin ortalamatene boyutunun 15 nm ve mıknatıslanma doygunluğunun da 75 emug-1 olduğu tespit edildi. Optimumadsorpsiyon şartlarında, adsorpsiyon kapasitesi ve Cr(VI) giderim yüzdesi sırasıyla 33.45 mg/g ve %88 olarakhesaplandı. Adsorpsiyon deneyleri sonrası hesaplanan termodinamik parametrelere göre MNP ile Cr(VI)adsorpsiyonu endotermik reaksiyonların sonucu oluşan bir proses olduğu söylenebilir. Langmuir ve Freundlichizoterm modelleri araştırıldı ve adsorpsiyon prosesinin Langmuir modeli ile daha iyi açıklanabilir olduğu tespitedildi. Kinetik araştırmalar sonucunda ise MNP ile Cr(VI) iyonlarının adsorpsiyonu için sözde-ikinci-derecekinetik model ile daha iyi bir açıklama getirilebilir

This study is aimed at the synthesis and characterization of the mesoporous magnetic-poly(divinylbenzene-1-vinylimidazole)[m-poly(DVB-VIM))microbeads(average diameter = 53-212 mu m); their application as adsorbent in the removal of Cu(II) ions from aqueous solutions was investigated. The mesoporous m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The mesoporous m-poly(DVB-VIM) microbeads were characterized by N-2 adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM), and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cu(II) ions from aqueous solutions such as pH, initial concentration, amount of mesoporousm-poly(DVB-VIM)) microbeads, contact time, and temperature were analyzed. Langmuir, Freundlich, and Dubinin-Radushkvich isotherms were used the model adsorption equilibrium data. The Langmuir isotherm model was the most adequate. The pseudo first-order, pseudo-second-order, Ritch-second-order, and intraparticle diffusion models were used to describe the adsorption kinetics. The experimental data fitted to pseudo second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy changes. Morever, after the use in adsorption, the mesoporous m-poly(DVB-VIM) microbeads with paramagnetic property was separated via the applied magnetic force. These features make the mesoporous m-poly(DVB-VIM) microbeads a potential candidate for support of Cu(II) ions removal under magnetic field.

WOS: 000250079800033 The effects of temperature, pH and ionic strength on the adsorption of crystal violet (CV+) by raw, Ni-saturated (Ni-), Co-saturated (Co-) and Zn-saturated (Zn-) bentonite samples were investigated. The amounts of CV+ adsorbed in equilibrium at 298.15 K were 0.27, 0.37, 0.49 and 0.54 mmol g(-1) bentonite, which correspond to 108%, 148%, 196% and 216% of the cation exchange capacity (CEC) of the raw, Ni-, Zn- and Co-saturated bentonite samples, respectively. The adsorption of the dye on these samples is pH-independent within the range (2.5-8.5), and it increases with ionic strength from 0 to 0.6 mol l(-1). Thermodynamic and Langmuir parameters showed that cation -saturated bentonite samples have relatively stronger ability than the raw bentonite towards the crystal violet (CV+) cation. (C) 2006 Elsevier Ltd. All rights reserved.

The minimisation of the distance function between the Gibbs energy of mixing and its common tangent plane (or line) is applied to adsorbed solutions. A specific algorithm to deal with the associated bilevel programming problem is presented and discussed. This approach is validated with experimental data and ideal adsorbed solution theory calculations for an ideal case and with experimental data for two non-ideal cases at low and high pressure. While the presently adopted non-ideal formulation provides solutions fulfilling only the necessary condition for equilibrium, the common tangent plane approach proposed in this paper enables the direct evaluation of the necessary and sufficient solution.

Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)-vinylphenyl boronic acid(VPBA)) [m-poly(EG-VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG-VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG-VPBA) microparticles were characterized by N-2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG-VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin-Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG-VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic parameters (free energy change, Delta G(0) enthalpy change, Delta H-0; and entropy change, Delta S-0) for the adsorption have been evaluated.

The present study deals with the characterization of primary sewage sludge-derived activated carbons which were used for phenol adsorption from the synthetic wastewater. The waste-derived adsorbents were prepared by a two-step process: chemical activation (with ZnCl2 and KOH) followed by pyrolysis. The mesoporous adsorbents were found to have BET surface area comparable to commercial activated carbon (surface area = 495-515 m(2)/g). The adsorption runs were performed in orbital shaker with synthetic phenolic wastewater (phenol concentration = 50-250 mg/L) to investigate the effect of various reaction parameters. The equilibrium phenol adsorption data could be described by Redlich-Peterson isotherm model and the pseudo first-order kinetic model exhibited the best fit to time-based adsorption data. The phenol adsorption was endothermic for all adsorbents. The performance of the thermally regenerated waste-derived adsorbents in the wastewater treatment was found to reduce significantly.

Materials capable of cost-effective on-board hydrogen storage and delivery are currently being sought worldwide as a means to facilitate a hydrogen-based energy transition in the transportation sector. Among the solutions proposed, hydrogen storage by physisorption on porous solids constitutes a main avenue of research, and for intelligent design of such materials a detailed knowledge of gas adsorption thermodynamics is of the utmost importance. Analysis of the available data for hydrogen adsorption on alkali and alkaline-earth cation exchanged zeolites clearly shows that standard adsorption enthalpy (D H0) and entropy (D S0) are correlated, in the sense that larger D S0 values correspond to larger D H0 values. It was also shown that, referring to absolute values, the relative rate at which adsorption entropy changes decreases gradually as adsorption enthalpy increases thus resulting in a non-linear correlation between D H0 and D S0. These results are discussed and corresponding implications for hydrogen storage via physisorption are highlighted.

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2014, Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2014, Bu çalışmada, üre-formaldehit reçinesi (UFR) ve bu reçinenin nanokompozitleri hazırlanıp, atık sulardan metilen mavisi (MB) ve kırmızı grlt (RG) boyar maddelerinin uzaklaştırılması için adsorbant olarak kullanılabilirliği incelenmiştir. Nanokompozitler (UFM ve UFH), UFR sentezi sırasında içerisine kütlece % 2 ve % 5 oranlarında tabakalı silikat montmorillonit (MMT) ve haloysit nanotüp (HNT) killeri eklenerek elde edilmiştir. Üre-formaldehit reçineleri kondenzasyon polimerizasyonu ile asitli ortamda sentezlenmiştir. MMT içeren UFM ve HNT içeren UFH nanokompozitleri de asitli ortamda in-situ polimerizasyon yöntemiyle hazırlanmıştır. Hazırlanan örneklerin FTIR, XRD ve TGA karakterizasyonları yapılarak sentezlenen örneklerin yapısal tanımlamaları yapılmıştır. Hazırlanan örneklerin adsorpsiyon kapasiteleri incelenerek, örneklerin adsorpsiyon kapasitesilerinin (qt), nanokompozit içerisindeki kil yüzdelerinin artmasıyla arttığını ve MMT içeren örneklerin HNT içerenlere göre daha yüksek adsorptiyon kapasitesine sahip olduğunu görülmüştür. Farklı deneysel parametrelerin etkisi incelenmiş ve adsorpsiyon kapasiteleri kıyaslanmıştır. Adsorpsiyon kinetiği çalışmalarında, verilerin yalancı ikinci derece hız denklemine uyduğu belirlenmiştir. 30, 40 ve 50 °C sıcaklıklarda boyar madde adsorpsiyonu deneyleri yapılarak sıcaklık arttıkça adsorpsiyon kapasitesinin arttığı bulunmuş ve her iki boyar madde için de termodinamik hesaplamalar kullanılarak aktivasyon enerjileri, adsorpsiyon denge sabitleri, adsorpsiyon Gibbs serbest enerjileri, adsorpsiyon entalpileri, adsorpsiyon entropileri saplanmıştır. Bu hesaplamalardan adsorpsiyon tipinin fiziksel adsorpsiyon olduğu, adsorpsiyonun kendiliğinden gerçekleşmediği ve adsorpsiyonun endotermik olduğu bulunmuştur. Sonuçlar Freundlich, Langmuir, Temkin and Dubinin–Radushkevich adsorpsiyon izotermlerine uygulandığında, MB adsorpsiyonu için Freundlich izoterm modelinin ve RG adsorpsiyonu için Langmuir izoterm modelinin daha uygun olduğu bulunmuştur., In this study, urea-formaldehyde resin (UFR) and its nanocomposites were prepared and investigated as adsorbent to remove methylene blue (MB) and red grlt (RG) dyes from wastewater. Layered silicate montmorillonite (MMT) and halloysite nanotube (HNT) were used for the production of urea-formaldehyde resin nanocomposites (UFM and UFH); the additive content was choosen as 2wt.% and 5wt.%. UFR was synthesized by condensation polymerization under acid condition. UFM and UFH containing MMT and HNT were also produced under acidic condition by in-situ polymerization technique. The synthesized samples were structurally defined by performing FTIR, XRD and TGA characterizations. Adsorption capacities of the prepared samples were investigated. Changes of adsorption capacities (qt) with time data showed adsorption capacity of resin nanocomposites increased by increasing of percentage of clay and the samples which containing MMT had higher adsorption capacity than that of HNT containing samples. The effect of the various experimental parameters was investigated. For the adsorption kinetics investigation, the pseudo second order rate equation was fitted to the adsorption data. The data taken from the experiments at 30, 40 and 50 °C temperatures, the activation energies, adsorption equilibrium constants, Gibbs adsorption energies, adsorption enthalpies, and adsorption entropies were calculated. From these calculations the type of adsorption (physical adsorption), the spontaneity of adsorption (nonspontaneous), and the type of heat of adsorption (endothermic) was found. The adsorption data were applied on the Freundlich, Langmuir, Temkin and Dubinin–Radushkevich isotherms. Freundlich model for MB and Langmuir model for RG were the best fitted isotherm model., Yüksek Lisans, M.Sc.

Current oil sand mining operations in the Athabasca basin are predominantly aqueous-based. Extracts containing large amounts of fines lead to the formation of stable organoclay suspensions in froths giving lower yields and greater tailing wastes and making the development of more efficient extraction methods desirable from both economical and environmental perspectives. We examine an indole-kaolinite system as a model for these oil fines and their resistance to washing in nonaqueous solvents. The prepared organoclays show indole loading exclusively on the external surface of the clay. Micron-scaled vermicular structures, similar to natural kaolinite, are observed. Their formation is believed to be driven by strong adsorbate-adsorbate interactions. Indole is the primary adsorbate, as solvent adsorption is shown to be minimal based on both experimental and computational results. Isotherms are constructed and parameters calculated from linear regression analysis fitted to the Brunauer-Emmett-Teller equation. Monolayer quantities calculated match well to the theoretical amount calculated from surface areas measurements. Washing the organoclays with both toluene and isopropanol results in a 50% decrease of loaded organic material, leaving a monolayer equivalent of organic matter. The statistical-mechanical 3D-RISM-KH molecular theory of solvation is employed to perform full sampling of solvent orientations around a kaolinite platelet and gain insights into the preferred orientation and adsorption thermodynamics of indole on kaolinite in toluene and heptane solvents. In its preferred orientation, indole is hydrogen-bonded to one or two O atoms at the aluminum hydroxide surface of kaolinite. The calculated solvation free energy and potential of mean force for adsorption of indole and solvents on kaolinite in solution yield the increasing adsorption strength order of heptane < toluene < indole on the aluminum hydroxide surface. Multilayer adsorption profiles are predicted based on the integrated three-dimensional distribution functions of indole, toluene, and heptane. © 2013 American Chemical Society.

The magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter 53-212 mu m) were synthesized and characterized; their use as adsorbent in removal of Cr(VI) ions from aqueous solutions was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterized by N-2 adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as pH, initial concentration, contact time and temperature were analyzed. Langmuir, Freundlich and Dubinin-Radushkvich isotherms were used as the model adsorption equilibrium data. Langmuir isotherm model was the most adequate. The pseudo-first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models were used to describe the adsorption kinetics. The apparent activation energy was found to be 5.024 kJ mol(-1), which is characteristic of a chemically controlled reaction. The experimental data fitted to pseudo-second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. The thermodynamic parameters obtained indicated the endothermic nature of adsorption of Cr(VI) ions. Morever, after the use in adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property were separeted via the applied magnetic force. The magnetic beads could be desorbed up to about 97% by treating with 1.0 M NaOH. These features make the m-poly(DVB-VIM) microbeads a potential candidate for support of Cr(VI) ions removal under magnetic field.

The interactions of furan and its hydrogenated derivatives (2,3-dihydrofuran, 2,5-dihydrofuran, tetrahydrofuran, and diethyl ether) with the isolated silanol groups at the surface of a highly dehydrated amorphous silica have been investigated by means of IR spectroscopy, at both constant and variable temperature. The adsorbate molecules studied form H-bonds of different strengths with surface silanols. With hydrogenated derivatives, the interaction involves the basic O atom, whereas with the aromatic furan molecule, the interaction probably occurs at the C═C double bond. The spectroscopic features of the stretching mode of H-bonded silanols change with the interacting molecule: classical correlations are observed. Because isolated silanols act as an ideal thermodynamic ensemble, the Langmuir model applies to all interactions. The fraction of silanols engaged in H-bonding can be measured from the decrement in intensity of the 3745 cm−1 band, so that corresponding optical isotherms can readily be drawn. The...

Materials capable of cost-effective on-board hydrogen storage and delivery are currently being soughtworldwide as a means to facilitate a hydrogen-based energy transition in the transportation sector. Amongthe solutions proposed, hydrogen storage by physisorption on porous solids constitutes a main avenue ofresearch, and for intelligent design of such materials a detailed knowledge of gas adsorption thermodynamicsis of the utmost importance. Analysis of the available data for hydrogen adsorption on alkali and alkaline-earth cation exchanged zeolites clearly shows that standard adsorption enthalpy (Δ