32 research outputs found

    Nanoaggregation of Polyaromatic Compounds Probed by Electrospray Ionization Mass Spectrometry

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    This paper reports the results of the first detailed experimental study on probing nanoaggregation of a polyaromatic compound. Electrospray ionization mass spectrometry (ESI–MS) was used to monitor the self-association of a well-defined polyaromatic compound, <i>N</i>-(1-hexylhepyl)-<i>N</i>′-(5-carboxylicpentyl)-perylene-3,4,9,10-tetracarboxylicbisimide (C5Pe), under various solution conditions. Gaseous ions corresponding to nanoaggregates of C5Pe molecules were directly observed on ESI mass spectra. The dominant aggregation number (<i>n</i>) was found to be less than 10, although larger nanoaggregates with an aggregation number larger than 10 were also observed. The aggregation number of C5Pe decreased by replacing toluene with xylene, while it increased with the C5Pe concentration or upon the addition of heptane to toluene as the solvent. The consecutive aggregation number was found only for small C5Pe nanoaggregates (2 ≤ <i>n</i> ≤ 11), which suggests a stepwise self-association at <i>n</i> ≤ 11. The larger nanoaggregates (<i>n</i> > 11) were formed by interactions between small nanoaggregates. The presence of naphthenic acids (NAs) was observed to hinder C5Pe self-association. The dispersive effect of NAs was found to be in the order of 1-methyl-1-cyclohexanecarboxylic acid ∼ cyclohexanebutyric acid < stearic acid < 5β-cholanic acid < 1-naphthalene pentanoic acid. The nanoaggregation behavior of C5Pe was compared to that of two other polyaromatic compounds

    Dewatering Bitumen Emulsions Using Interfacially Active Organic Composite Absorbent Particles

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    One of the major challenges in petroleum production is the formation of undesirable emulsions, which often leads to an increased cost for downstream operations. This problem is exacerbated for bitumen, which contains a greater fraction of interfacially active materials known to stabilize small emulsified water droplets that are extremely difficult to separate. To accelerate separation of emulsified water droplets from bitumen, chemical demulsifiers are extensively used to modify interfacial properties, promote droplet flocculation, and facilitate coalescence of the emulsified droplets. However, the use of chemical demulsifiers is rather system-specific as a result of the overdosing phenomenon. As an alternative to chemical demulsification, composite absorbent particles, prepared by dehydrating well-designed water-in-oil emulsion droplets, were proposed to promote dewatering of water-in-diluted bitumen emulsions. The composite particles were composed of nanosize magnetic particles dispersed in an absorbent matrix coated with an interfacially active material. The composite structure combines the absorptive capacity of sodium carboxymethyl cellulose for water with the interfacial activity of ethylcellulose while retaining the magnetic responsiveness of dispersed Fe<sub>3</sub>O<sub>4</sub> nanoparticles. Using composite absorbent particles, nearly complete dewatering of water-in-diluted bitumen emulsions was achieved by increasing the dosage of absorbent particles. The dewatering rate was improved using smaller particles of greater specific surface area or increasing mixing intensity to promote contact between absorbent particles and emulsified water droplets. Although the surface of composite absorbent particles was initially suitable for dispersing in non-aqueous media, the subsequent change in wettability upon absorption of water (hydration) caused hydrated absorbent particles to aggregate, providing an opportunity for regeneration/reuse of hydrated particles by first separation particles from diluted bitumen through gravity separation or a filtration process

    Development of a Novel Mercury Cartridge for Mercury Analysis

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    Mercury cartridges, which are a key component of semicontinuous online mercury monitors, capture low-concentration mercury from the effluent streams of coal-fired power plants and subsequently release highly concentrated pulses of mercury for spectroscopic analysis. The most common sorbent used in mercury cartridges is gold-coated silica beads (Au/SiO<sub>2</sub>), which form a reversible amalgam with elemental mercury. Ag/MC is a robust composite mercury sorbent, consisting of silver nanoparticles supported on the surface of natural chabazite, which can efficiently capture and release mercury from a real flue gas environment, making the material a potential alternative to Au/SiO<sub>2</sub> in mercury preconcentration cartridges. The performance of Au/SiO<sub>2</sub>- and Ag/MC-based mercury cartridges in capturing low-level mercury in Ar-, SO<sub>2</sub>-, and NO-containing gas streams was investigated systematically. Both SO<sub>2</sub> and NO were determined to be harmful to the performance of an Au/SiO<sub>2</sub> mercury cartridge. NO had limited impact on the performance of Ag/MC, but the presence of SO<sub>2</sub> led to reduced mercury recovery from the Ag/MC mercury cartridge. Soda lime was proven to be an effective, NO-tolerant SO<sub>2</sub> scrubber. Based on these results, a novel SO<sub>2</sub>- and NO-tolerant mercury cartridge was designed and fabricated using soda lime as a disposable SO<sub>2</sub> scrubber and Ag/MC as the reversible mercury sorbent

    Dissipation of Film Drainage Resistance by Hydrophobic Surfaces in Aqueous Solutions

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    Understanding and minimizing the film drainage resistance (forces) from a moving fluid are of great importance both scientifically and technologically. The direct and accurate measurement of film drainage resistance was made possible by integrating a speaker diaphragm of large displacement range and rapid responses with a sensitive bimorph force sensor and high resolution digital camera. Our study demonstrates that the liquid film drainage resistance can be greatly diminished or accurately controlled by increasing or controlling the hydrophobicity of solid surfaces. The results show that for a given solid surface hydrophobicity, the film drainage resistance at the point where film ruptures increases linearly with increasing bubble approach velocity. The dependence of the film drainage resistance on bubble approach velocity decreases linearly with increasing hydrophobicity of the solid surface. This finding has important implications for biological processes, microfluidic devices, and design of new materials

    Dissipation of Film Drainage Resistance by Hydrophobic Surfaces in Aqueous Solutions

    No full text
    Understanding and minimizing the film drainage resistance (forces) from a moving fluid are of great importance both scientifically and technologically. The direct and accurate measurement of film drainage resistance was made possible by integrating a speaker diaphragm of large displacement range and rapid responses with a sensitive bimorph force sensor and high resolution digital camera. Our study demonstrates that the liquid film drainage resistance can be greatly diminished or accurately controlled by increasing or controlling the hydrophobicity of solid surfaces. The results show that for a given solid surface hydrophobicity, the film drainage resistance at the point where film ruptures increases linearly with increasing bubble approach velocity. The dependence of the film drainage resistance on bubble approach velocity decreases linearly with increasing hydrophobicity of the solid surface. This finding has important implications for biological processes, microfluidic devices, and design of new materials

    Measurement of Interactions between Solid Particles, Liquid Droplets, and/or Gas Bubbles in a Liquid using an Integrated Thin Film Drainage Apparatus

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    A novel device was designed to measure drainage dynamics of thin liquid films confined between a solid particle, an immiscible liquid droplet, and/or gas bubble. Equipped with a bimorph force sensor, a computer-interfaced video capture, and a data acquisition system, the newly designed integrated thin film drainage apparatus (ITFDA) allows for the direct and simultaneous measurements of force barrier, true film drainage time, and bubble/droplet deformation under a well-controlled external force, receding and advancing contact angles, capillary force, and adhesion (detachment) force between an air bubble or oil droplet and a solid, a liquid, or an air bubble in an immiscible liquid. Using the diaphragm of a high-frequency speaker as the drive mechanism for the air bubble or oil droplet attached to a capillary tube, this newly designed device is capable of measuring forces over a wide range of hydrodynamic conditions, including bubble approach and retract velocities up to 50 mm/s and displacement range up to 1 mm. The results showed that the ITFDA was capable of measuring hydrodynamic resistance, film drainage time, and other important physical parameters between air bubbles and solid particles in aqueous solutions. As an example of illustrating the versatility, the ITFDA was also applied to other important systems such as interactions between air bubble and oil droplet, two air bubbles, and two oil droplets in an aqueous solution

    Measurement of Interactions between Solid Particles, Liquid Droplets, and/or Gas Bubbles in a Liquid using an Integrated Thin Film Drainage Apparatus

    No full text
    A novel device was designed to measure drainage dynamics of thin liquid films confined between a solid particle, an immiscible liquid droplet, and/or gas bubble. Equipped with a bimorph force sensor, a computer-interfaced video capture, and a data acquisition system, the newly designed integrated thin film drainage apparatus (ITFDA) allows for the direct and simultaneous measurements of force barrier, true film drainage time, and bubble/droplet deformation under a well-controlled external force, receding and advancing contact angles, capillary force, and adhesion (detachment) force between an air bubble or oil droplet and a solid, a liquid, or an air bubble in an immiscible liquid. Using the diaphragm of a high-frequency speaker as the drive mechanism for the air bubble or oil droplet attached to a capillary tube, this newly designed device is capable of measuring forces over a wide range of hydrodynamic conditions, including bubble approach and retract velocities up to 50 mm/s and displacement range up to 1 mm. The results showed that the ITFDA was capable of measuring hydrodynamic resistance, film drainage time, and other important physical parameters between air bubbles and solid particles in aqueous solutions. As an example of illustrating the versatility, the ITFDA was also applied to other important systems such as interactions between air bubble and oil droplet, two air bubbles, and two oil droplets in an aqueous solution

    PENGARUH PUPUK ORGANIK PADAT LIMBAH KELAPA SAWIT DAN PUPUK NITROGEN TERHADAP SIFAT KIMIA TANAH SERTA PERTUMBUHAN DAN HASIL SAWI (Brasicca juncea)

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    Penggunaan pupuk sintetik dalam jangka panjang dapat merusak tanah dan menurunkan hasil tanaman sehingga tanah tidak mampu lagi meningkatkan produktivitasnya. Hal ini menuntut kita untuk mencari teknologi alternatif yang mampu mengurangi penggunaan pupuk sintetik adalah dengan menggunakan bahan organik. Namun kebutuhan unsur hara yang di butuhkan oleh tanaman tidak semuanya dapat dipenuhi oleh pupuk organik sehingga penggunaannya perlu dikombinasikan dengan pupuk sintetik. Tujuan penelitian ini adalah untuk mendapatkan kombinasi dosis pupuk organik padat dan pupuk nitrogen terhadap sifat-sifat kimia tanah serta pertumbuhan dan hasil sawi. Penelitian ini dilaksanakan pada bulan Juni-September 2016 di rumah kaca dan Laboratorium Ilmu Tanah Universitas Bengkulu. Tanah yang digunakan adalah Ultisol yang berasal dari daerah Kandang Limun Kecamatan Muara Bangkahulu. Pada penelitian ini digunakan benih sawi (panah merah) yang ditanam pada polibag yang disusun berdasarkan Rancangan Acak Lengkap dengan tiga ulangan dan 12 perlakuan yaitu P0N0 Kontrol, P0N1 : 50 kg ha -1 , P0N2 : 100 kg ha -1 urea, P1N0 : 7.5 ton ha -1 POP, P1N1 : 7.5 ton ha -1 POP + 50 kg ha -1 urea, P1N2 : 7.5 ton ha -1 POP + 100 kg ha -1 urea, P2N0 : 15 ton ha -1 tanpa urea, setara dengan 7.5 gr polibag - 1, P2N1 : 15 ton ha -1 POP + 50 kg ha urea, P2N2 : 15 ton ha -1 POP + 100 kg ha -1 urea, P3N0 : 22.5 ton ha -1 tanpa urea, P3N1 : 22.5 ton ha -1 POP + 50 kg ha -1 urea, P3N2: 22.5 ton ha -1 POP + 100 kg ha urea. Variabel pengamatan pada penelitian ini adalah N Total, P tersedia, K-dd, Al-dd, C-Organik, pH H O, Jumlah daun, kehijauan daun, berat basah berangkasan atas, berat basah brangkasan bawah, berat kering berangkasan atas dan berat kering berangkasan bawah. Hasil penelitian menunjukkan bahwa penambahan pupuk organik pada dosis 15 ton ha 2 POP tanpa urea, dapat memperbaiki sifat kimia tanah yang diindikasikan dari peningkatan P tersedia, K dapat ditukar, pH tanah dan penuruan Al-dd pemberian 15 ton ha POP + 100 kg ha -1 urea sampai 22,5 ton ha -1 POP tanpa urea, menghasilkan jumlah daun dan bobot basah tanaman tertinggi. -1 -1 -1 -

    Dewetting Dynamics of a Solid Microsphere by Emulsion Drops

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    A novel micropipet technique was developed to quantify the dewetting dynamics of individual microsphere particles by emulsified viscous crude oil drops in aqueous media. This technique allowed dynamic microscale receding contact angles of water to be measured in situ for solid–oil–water systems. System parameters, including modification of glass microspheres and characteristics of oil drops, were varied to study their effect on dewetting dynamics of the systems. Increasing solvent dosage in viscous oil was found to decrease static receding contact angle of water for clean and bitumen-treated glass surfaces, but showed a negligible effect on static receding contact angle for ethyl cellulose (EC)-treated glass surface. Interestingly, dynamic dewetting behavior exhibited a strong dependence on surface modification and the addition of solvent to viscous oil. No dewetting dynamics was observed for clean hydrophilic glass surface. For bitumen- or EC-treated glass surfaces, more rapid dewetting dynamics of water were determined with increasing addition of solvent to viscous oil. Both de Gennes viscous dissipation hydrodynamic and the Blake/Haynes molecular-kinetic models were developed for the current system to understand the observed dynamic dewetting characteristics

    Probing Single-Molecule Adhesion of a Stimuli Responsive Oligo(ethylene glycol) Methacrylate Copolymer on a Molecularly Smooth Hydrophobic MoS<sub>2</sub> Basal Plane Surface

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    Molybdenum disulfide (MoS<sub>2</sub>) has been receiving increasing attention in scientific research due to its unique properties. Up to now, several techniques have been developed to prepare exfoliated nanosize MoS<sub>2</sub> dispersions to facilitate its applications. To improve its desired performance, as-prepared MoS<sub>2</sub> dispersion needs further appropriate modification by polymers. Thus, understanding polymer–MoS<sub>2</sub> interaction is of great scientific importance and practical interest. Here, we report our results on molecular interactions of a biocompatible stimuli-responsive copolymer with the basal plane surface of MoS<sub>2</sub> determined using single molecule force spectroscopy (SMFS). Under isothermal conditions, the single-molecule adhesion force of oligo­(ethylene glycol) methacrylate copolymer was found to increase from 50 to 75 pN with increasing NaCl concentration from 1 mM to 2 M, as a result of increasing hydrophobicity of the polymers. The theoretical analysis demonstrated that single-molecule adhesion force is determined by two contributions: the adhesion energy per monomer and the entropic free energy of the stretched polymer chain. Further data analysis revealed a significant increase in the adhesion energy per monomer with a negligible change in the other contribution with increasing salt concentration. The hydrophobic attraction (HA) was found to be the main contribution for the higher adhesion energy in electrolyte solutions of higher NaCl concentrations where the zero-frequency of van der Waals interaction were effectively screened. The results illustrate that oligo­(ethylene glycol) methacrylate copolymer is a promising polymer for functionalizing MoS<sub>2</sub> and that one can simply change the salt concentration to modulate the single-molecule interactions for desired applications
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