Biblioteca Digital

Magnetic composites have a wide range of potential technological applications; however the evaluation of this material for extraction of phenolic compounds has not been sufficiently studied. Due to its high toxicity and solubility the removal of phenolic compounds from the aquatic environments has critical importance. In this work polymeric composites were prepared by anchoring Ni and Co particles on sulfonatedpoly(styrene-co-divinylbenzene) PS-DVB. The PS-DVB beads were synthesized by suspension polymerization and reacted with acetyl sulfate, aiming to obtain sulfonated copolymers. All materials were capable of removing phenol from aqueous solutions. The phenol adsorption kinetics was influenced by the polymer porosity and swelling capacity in water. The composite derivative of the more porous copolymer impregnated with nickel (C1SNi) was the most efficient in phenol removal, with the sorption equilibrium being established more rapidly than for the other composites. The pseudo second-order model was more adequate to describe the phenol adsorption process for the composite C1SNi. The Langmuir model describes successfully the phenol removal by this composite.; CNPq; CAPES; FAPERJ

O processo de adsorção por carvão ativado é uma técnica muito aplicada para tratamento de efluentes. Porém o tratamento que envolve adsorção não é um sistema completo, pois há a necessidade da destruição dos compostos que foram imobilizados na superfície do carvão. Frente a esse problema, métodos alternativos de regeneração de carvão ativado são investigados. Os processos Fenton e foto-Fenton são considerados tecnologias promissoras de tratamento de efluentes, e foram testados para regenerar o carvão ativado. Este trabalho objetiva estudar a adsorção de fenol em carvões ativados (CAs) e a consecutiva regeneração in-situ do carvão pela oxidação de (foto-) Fenton. Duas operações diferentes foram realizadas: 1) sistema de batelada, a fim de investigar a influência das concentrações de Fe2+ e H2O2; 2) adsorção contínua em leito fixo, seguido de circulação em batelada dos reagentes de Fenton pelo leito de CA saturado, para examinar a eficiência do processo real. Foram estudados dois tipos de carvão ativado: CA L27 (meso e microporoso) e CA S23 (somente microporoso). No reator de batelada as melhores condições encontradas para a mineralização do poluente no sistema Fenton homogêneo não são as melhores para a regeneração do CA: foi observada uma redução contínua da capacidade de adsorção do L27 após 3 oxidações...

O lodo de esgoto é um resíduo gerado em grandes quantidades nas ETEs. Apenas na Região Metropolitana de São Paulo em 2015 prevê-se uma produção de 1538 toneladas por dia. Diferentemente de países desenvolvidos, no Brasil a maior parte desse resíduo é enviada para aterros sanitários, sendo ignoradas outras possibilidades de utilização. A pirólise do lodo é uma alternativa à incineração, e possui vantagens como a geração de subprodutos mais úteis como, por exemplo, materiais porosos para adsorção de poluentes de meios aquosos e gasosos. Visando novas utilizações para o lodo de esgoto da ETE Barueri, a presente pesquisa teve como objetivo o estudo de sua pirólise para obtenção de produtos contendo coque e sua utilização como material adsorvente de poluentes (fenol e tartrazina) em meio aquoso. Também foi estudado o potencial de uso energético do lodo e de coques obtidos por pirólise por meio da determinação de seus poderes caloríficos. Para sua utilização na pesquisa, o lodo foi coletado, seco, macerado e passado em peneira ABNT 200, produzindo um material identificado como S2. Por análises do seu processo de pirólise determinou-se a temperatura mais indicada para formação de coque, obtendo-se o valor de 500°C. Foram então realizadas pirólises isotérmicas nessa temperatura por diferentes períodos de tempo (0...

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Phenol is a pollutant that has caused many problems even when present in low concentrations and still represents an environmental problem with difficult solution. This paper presents a study of phenol adsorption by organophilic clays, obtained from aVerde Claro bentonitic clay, from Bravo, Paraiba State, Brazil, at different partial cation exchange degrees with hexadecyltrimethylammonium (HDTMA) chloride, at increasing reacting ratios, from 20 to 120 mmol/100 g of clay, which were characterized in a previous paper. By using Freundlich isotherms obtained for each case, which presented the best correlation coefficients with experimental data, it can be seen that for equilibrium concentrations up to 0.53 mmol L(-1) of phenol, the adsorptive capacity decreases for organophilic bentonites obtained at cation exchange degrees higher than 80 mmol/100 g of clay. This indicates that in these cases, the higher is the exchange by organic cation, the higher is the difficulty for the phenol diffusion and sorption in the interlayer space of the organophilic clays. For higher equilibrium concentrations...

A crescente demanda de derivados de petróleo proporciona cada vez mais a necessidade desses produtos na sociedade atual. Este fato é reconhecido pelo desenvolvimento do país, com investimentos e desenvolvimentos em produtos energéticos e não energéticos oriundos do processamento do petróleo e, como consequência, são gerados grandes volumes de efluentes, em que os componentes fenólicos são presentes contaminantes comuns. Tratam-se de compostos tóxicos, carcinogênicos e que possuem boa solubilidade em água e baixa capacidade de biodegradação. Levando-se em conta esse aspecto, este estudo propôs mitigar os impactos ambientais utilizando o processo de adsorção em carvão ativado para remoção de fenóis. Para o desenvolvimento dessa pesquisa foi realizada uma revisão bibliográfica sobre o petróleo, algumas consequências geradas devido ao seu processamento, apresentando também técnicas de tratamento do efluente água fenólica, selecionando a adsorção como método mais eficiente e econômico para o tratamento, além do estudo experimental realizado para analisar a viabilidade técnica do tratamento, em que a caracterização do adsorvente e o conhecimento da dinâmica de adsorção são imprescindíveis para esse estudo. Os métodos de caracterização utilizados foram: análise granulométrica...

We use grand canonical Monte Carlo and molecular dynamics simulations to study the adsorption of phenol on carbon materials. Activated carbon is modelled by pore size distributions based on DFT methods; carbon black is represented by a single carbon slab with varying percentages of surface atoms removed. GCMC results for the adsorption from the corresponding gas phase gave reasonable agreement with experimental adsorption results. MD simulations, that studied the influence of the presence of water and surface roughness on the arrangement of the adsorbed phenol molecules, showed that the interaction between the adsorbed molecules is strongly influenced by the presence of water.

The adsorption of phenol from dilute aqueous solutions onto new activated carbons (AC) was studied. The novel activated carbon was produced from lignocellulosic (LC) precursors of rapeseed and kenaf. Samples oxidised with nitric acid in liquid phasewere also studied. The results have shown the significant potential of rapeseed and kenaf for the activated carbon production. The activated carbons produced by carbon dioxide activation were mainly microporous with BET apparent surface area up to 1350m2 g−1 and pore volume 0.5cm3 g−1. The effects of concentration (0.1–2mM) and pH (3–13) were studied. The phenol adsorption isotherms at 25 ◦C followed the Freundlichmodel withmaximumadsorption capacities of approximately 80 and 50mgg−1 for the pristine and oxidised activated carbons, respectively. The influence of pH on the adsorption has two trends for pH below and above 10. It was possible to conclude that when phenol is predominantly in the molecular form the most probable mechanism is based on the – dispersion interaction between the phenol aromatic ring and the delocalised electrons present in the activated carbon aromatic structure. When phenolate is the major component the electrostatic repulsion that occurs at high pH values is the most important aspect of the adsorption mechanism.

The adsorption of phenol and 4-nitrophenol from aqueous solutions by carbon blacks was studied. Particular attention was paid to the characterisation of the surface chemistry and ionisation of the carbon blacks by use of a simple carbon surface ionisation model, as well as the use of a normalised form of the Freundlich equation for the analysis of the adsorption isotherms. The results indicated that the solutes interact directly with the graphene layers and that the adsorption is sensitive to the π-electron density. Phenol has a weaker interaction and is more sensitive to the system conditions. In particular, it is more sensitive to oligomerisation under certain conditions. Comparison of the results with those previously reported for activated carbons with similar points of zero charge prepared from cork confirms the existence of a significant micropore-narrowing effect in the adsorption of organic solutes by activated carbons and which can lead to up to a doubling of the value of the Freundlich exponent, nF.

The adsorption of phenol for the removal of this toxic compound has been investigated in many experimental studies whereas the simulation studies are scarce, especially comparisons with experimental data. This work aims to give deeper insight into the adsorption of phenol using GCMC and MD simulation. Carbon black is used as a reference material and comparison with experimental data for the carbon black and activated carbon data was done.

The adsorption of phenol and mercury from dilute aqueous solutions onto new activated carbons was studied. These included activated carbons produced from novel precursors, namely rapeseed, vine shoots and kenaf, and samples oxidised with nitric acid in liquid phase. The results have shown the significant potential of rapeseed, vine shoots and kenaf for the activated carbon production. The activated carbons produced by carbon dioxide activation were mainly microporous with BET apparent surface area up to 1224m2g-1 and pore volume 0.5cm3g-1. The effects of concentration and pH were studied. The phenol adsorption isotherms at 25ºC followed the Freundlich model with maximum adsorption capacities of approximately 80mgg-1 and 60mgg-1 for the pristine and oxidised activated carbons, respectively. The influence of pH on the phenol adsorption has two trends for pH smaller and bigger than 10. The maximum adsorption capacity of mercury adsorption onto activated carbon made from vine shoots reaches 1103mgg-1. The adsorption depends on the mercury species and the on the adsorbent properties, namely porosity and net surface charge.

The present study describes phenol adsorption on commercial active carbon (CAF) under alkaline conditions in the concentration range of 0.01 to 2.08 mmol L-1. Surface characterization has been performed by means of surface area measurements, IR spectroscopy and Boehm titration. The effect of temperature on the adsorption equilibrium isotherm was investigated at 23, 30, 40, 50 and 60 °C. The results showed that adsorption capacity decreased with increasing temperature. The adsorption kinetics and the role of surface characteristics on the adsorption of phenol also discussed.

The present study deals with phenol adsorption on chitin and chitosan and removal of contaminants from wastewater of a petroleum refinery. The adsorption kinetic data were best fitted to first- and second-order models for chitosan and chitin, respectively. The results of adsorption isotherms showed Langmuir model more appropriately described than a Freundlich model for both adsorbents. The adsorption capacity was 1.96 and 1.26 mg/g for chitin and chitosan, respectively. Maximum removal of phenol was about 70-80% (flow rate: 1.5 mL/min, bed height: 18.5 cm, and 30 mg/L of phenol. Wastewater treatment with chitin in a fixed-bed system showed reductions of about 52 and 92% for COD and oil and greases, and for chitosan 65 and 67%, respectively. The results show improvement of the effluent quality after treatment with chitin and chitosan.

Canonical Monte Carlo simulations, at 298 K, of the adsorption of phenol in a dilute aqueous solution on gold electrodes, at the potential of zero charge, are presented. The results suggest that the process occurs in two distinct and successive steps. Adsorption starts with the phenol oxygen atom pointing towards the gold surface and the aromatic ring in a quasi-perpendicular orientation relative to the surface. This is followed by the reorientation of the aromatic ring to a parallel configuration. The effect of the solvent is analyzed through the calculation of the potential of mean force acting on phenol. Despite the simplicity of the model and the interaction potentials used in the simulations, the results are in good agreement with experimental observations, giving insight into the microscopic details of the adsorption process of phenol at low concentrations.

Magnetic composites have a wide range of potential technological applications; however the evaluation of this material for extraction of phenolic compounds has not been sufficiently studied. Due to its high toxicity and solubility the removal of phenolic compounds from the aquatic environments has critical importance. In this work polymeric composites were prepared by anchoring Ni and Co particles on sulfonatedpoly(styrene-co-divinylbenzene) PS-DVB. The PS-DVB beads were synthesized by suspension polymerization and reacted with acetyl sulfate, aiming to obtain sulfonated copolymers. All materials were capable of removing phenol from aqueous solutions. The phenol adsorption kinetics was influenced by the polymer porosity and swelling capacity in water. The composite derivative of the more porous copolymer impregnated with nickel (C1SNi) was the most efficient in phenol removal, with the sorption equilibrium being established more rapidly than for the other composites. The pseudo second-order model was more adequate to describe the phenol adsorption process for the composite C1SNi. The Langmuir model describes successfully the phenol removal by this composite.

This work is related to removal of phenol from wastewaters by adsorption onto polymeric resins, a current alternative to activated carbon. A closed circuit, bench-scale liquid fluidized bed system was developed for this purpose. Phenol aqueous solutions with initial concentrations in the range of 0.084 to 0.451 kg/m³ were used to fluidize small permeable capsules of stainless steel screen containing a commercial resin at 308 K. Experiments were carried out using a fluidizing velocity 20% above that of the minimum fluidization of the capsules. Typically, 30 passages of the liquid volume circulating through the bed were required to reach a quasi-equilibrium concentration of phenol in the treated effluent. A simple batch adsorption model using the Freundlich isotherm successfully predicted final phenol concentrations. Suspended solids, often present in residual waters and a common cause of fixed bed clogging, were simulated with wood sawdust.

Molecularly imprinted polymers (MIPs) were fabricated on glass slides with a “sandwich” technique giving ~20 μm thick films. Methanol/water as a solvent, and polyethyleneglycol and polyvinylacetate as solvent modifiers, were used to give a porous morphology, which was studied with scanning electron microscopy and gravimetric analysis. Various MIPs were synthesized through non-covalent imprinting with phenol as the template; itaconic acid, 4-vinylpyridine, and styrene as monomers; ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and pentaerythritol triacrylate (PETA) as cross-linkers. Binding and imprinting properties of the MIPs were evaluated based on phenol adsorption isotherms. Since phenol has only one weakly acidic hydroxyl group and lacks unique structural characteristics necessary for binding specificity, the preparation of selective MIPs was challenging. The recognition of phenol via hydrogen bonding is suppressed in water, while hydrophobic interactions, though promoted, are not specific enough for highly-selective phenol recognition. Nevertheless, the styrene-PETA MIP gave modest imprinting effects, which were higher at lower concentrations (Imprinting Factor (IF) = 1.16 at 0.5 mg·L−1). The isotherm was of a Freundlich type over 0.1–40 mg·L−1 and there was broad cross-reactivity towards other structurally similar phenols. This shows that phenol MIPs or simple adsorbents can be developed based on styrene for hydrophobic binding...

Produced water is the main effluent linked to the activity of extraction of oil and their caring management is necessary due to the large volume involved, to ensure to minimize the negative impacts of discharges of these waters in the environment. This study aimed to analyze the use of retorted shale, which is a reject from the pyrolysis of pirobituminous shale, as adsorbent for the removal of phenols in produced water. The material was characterized by different techniques (grain sized analysis, thermal analysis, BET, FRX, FT-IR, XRD and SEM), showing the heterogeneity in their composition, showing its potential for the removal of varied compounds, as well as the phenols and their derivatives. For the analysis of the efficiency of the oil shale for the adsorption process, assays of adsorption balance were carried through, and also kinetic studies and dynamics adsorption, in the ETE of the UTPF of Petrobras, in Guamaré-RN. The balance assays shown a bigger conformity with the model of Langmuir and the kinetic model more adjusted to describe the adsorption of phenols in retorted shale was of pseudo-second order. The retorted shale presented a low capacity of adsorption of phenols (1,3mg/g), when related to others conventional adsorbents...

Humic-based organic compounds containing phenol or benzoic acid groups strongly compete with phosphates for specific binding sites on the surface of these colloidal particles. To study the interactions between phenol groups and the surface binding sites of unmodified or modified colloidal particles, chemical force spectrometry (CFS) was used as a tool to measure the adhesion force between an atomic force microscopy (AFM) tip terminated with a phenol self-assembled monolayer and colloidal particles under varying pH conditions. Two modification methods, co-precipitation and post-precipitation, were used to simulate the naturally-occurring phosphate and humic-acid adsorption process. The pH dependence of adhesion forces between phenol-terminated tip and colloidal particles could be explained by an interplay of electrostatic forces, the surface loading of the modifying phosphate or humic acid species and ionic hydrogen bonding. Polydimethylsiloxane (PDMS) is a widely-used polymer in microfluidic devices. PDMS surfaces are commonly modified to make it suitable for specific microfluidic devices. We studied the surface modification of PDMS using four perfluoroalkyl-triethoxysilane molecules of differing length of perfluorinated alkyl chain. The results show that the length of fluorinated alkyl chain has important effects on the density of surface modifying molecules...

This paper reviews some recent canonical Monte Carlo simulations of the Au(210)/H2O interface using a DFT force field developed by us. New results are reported on the solvent contribution to the potential of mean force (PMF) for the phenol adsorption, from a dilute aqueous solution, onto the Au(210) surface. The Monte Carlo simulations show the common features normally observed in the simulation of water in contact with metallic surfaces, where the water molecules adsorb forming bilayers. The molecules adsorbed over the Top gold sites form hydrogen bonds between the first and second solvent layers. The PMF calculations indicate that the phenol molecule penetrates the solvent layers with the aromatic ring in a perpendicular configuration and the oxygen atom pointing to the surface. The PMF results also suggest the existence of hydrogen bonds between the phenol molecule and the first solvent layer of the water molecules adsorbed onto the Top .

Activated carbons used in the precious metals extraction industry are characterized by large internal surface areas and a great affinity for metal ions. The purpose of this research is to prepare activated carbon from a South African bituminous coal by physical activation that is suitable and cost-effective for use in the extraction of metals. The quality of the coal-based activated carbon may not prove to be as good as activated carbon produced from other traditional sources, but the production costs involved may make South African coal a feasible alternative feedstock. The activated carbons produced were characterized by Brunauer, Emmett, and Teller (BET) surface area, activated carbon pH, and phenol adsorption studies and the results compared to the results from a commercially available activated carbon, Norit RO 0.8 (control sample). Bituminous coals from various sources including Witbank Seam 4 and Free State coal were used in this study. The preparation method chosen was physical activation using superheated steam. The effects of process variables such as activation time (1-3 h) and temperature (600-800ºC) were studied in order to optimize those parameters. The activated carbon surface area was characterized by means of nitrogen adsorption isotherms at 77K. BET surface area analysis showed that Witbank Seam 4 coal activated at a temperature of 800ºC and activation time of 3 hours resulted in a surface area of 340 m²/g. Quality control of each sample was performed by measuring the pH of a known amount of the prepared activated carbon in distilled water over time. Results showed that the pH of some of the prepared activated carbons reached a value of 11. Phenol adsorption results for the different activated carbons prepared corresponded well to the results obtained for the Norit RO 0.8 activated carbon sample.