32 research outputs found
Nanoaggregation of Polyaromatic Compounds Probed by Electrospray Ionization Mass Spectrometry
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
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
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
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
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
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
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)
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
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
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 oligoÂ(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 oligoÂ(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