Ultrafine particulate aerosols less than 100 nm diffuse
randomly
in the air and are hazardous to the environment and human health.
However, no technical standards or commercial products are available
for filtering particle sizes under 100 nm yet. Here, we report the
development of a porous poly(l-lactic acid) (PLLA) nanofibrous
membrane filter with an ultra-high specific surface area via electrospinning
and a post-treatment process. After PLLA fibres were electrospun and
collected, they were treated by acetone to generate a blossoming porous
structure throughout each individual fibre. Characterizations of morphology,
crystallinity, and mechanical and thermal properties demonstrated
that the porous structure can be attributed to the nonsolvent-induced
spinodal phase separation during electrospinning and solvent-induced
recrystallization during post treatment. The blossoming porous structure
with high specific surface area contributed to excellent filtration
efficiency (99.99%) for sodium chloride (NaCl) ultrafine aerosol particles
(30–100 nm) with a low pressure drop (110–230 Pa). Notably,
under 7.8 cm/s air flow rate, the membrane samples performed better
for filtering smaller-sized aerosol particles than the larger ones
when evaluated by the quality factor (0.07). Finally, this finding
demonstrates that the electrospun membrane with a hierarchical pore
structure and high specific surface area hold great potential in applications
as air-filtering materials.
Porous poly(L-lactic acid) (PLLA) nanofibrous membrane with the high surface area was developed by electrospinning and post acetone treatment and used as a substrate for deposition of chitosan. Chitosan was coated onto porous nanofibrous membrane via direct immersion coating method. The porous PLLA/chitosan structure provided chitosan a high surface framework to fully and effectively adsorb heavy metal ions from water and showed higher and faster ion adsorption. The composite membrane was used to eliminate copper ions from aqueous solutions. Chitosan acts as an adsorbent due to the presence of aminic and hydroxide groups which are operating sites for the capture of copper ions. The maximum adsorption capacity of copper ions reached 111.66±3.22 mg/g at pH (7), interaction time (10 min) and temperature (25 °C). The adsorption kinetics of copper ions was established and was well agreed with the second-order model and Langmuir isotherm. Finally, the thermodynamic parameters were studied.
The ionic liquid 1-ethyl-3-methylimidazole acetate ([EMIM]OAc) was found to be a mild and effective catalyst for the efficient, one-pot, three-component synthesis of 2-aryl-4,5-diphenyl imidazoles at room temperature under ultrasonic irradiation. This procedure has many obvious advantages compared to those reported in the previous literatures, including avoiding the use of harmful catalysts, reacting at room temperature, high yields, simplicity of the methodology.
The basic ionic liquid 1-butyl-3-methylimidazolium hydroxide, [bmIm]OH, efficiently catalyzes the condensation reaction of aldehydes and ketones with hydroxylamine hydrochloride under ultrasound irradiation. Compared with conventional methods, the main advantages of the present procedure are milder conditions, shorter reaction time and higher yields.
The rheological properties of high concentrated wood pulp cellulose 1-allyl-3-methy-limidazolium Chloride ([Amim]Cl) solutions were investigated by using steady shear and dynamic viscoelastic measurement in a large range of concentrations (10-25 wt %). The measurement reveals that cellulose may slightly degrade at 110 C in [Amim]Cl and the Cox-Merz rule is valid for 10 wt % cellulose solution. All of the cellulose solutions showed a shear thinning behavior over the shear rate at temperature from 80 to 120 C. The zero shear viscosity (g o ) was obtained by using the simplified Cross model to fit experimental data. The g o values were used for detailed viscosity-concentration and activation energy analysis. The exponent in the viscosity-concentration power law was found to be 3.63 at 80 C, which is comparable with cellulose dissolved in other solvents, and to be 5.14 at 120 C. The activation energy of the cellulose solution dropped from 70.41 to 30.54 kJ/mol with an increase of concentration from 10 to 25 wt %. The effects of temperature and concentration on the storage modulus (G 0 ), the loss modulus (G 00 ) and the first normal stress difference (N 1 ) were also analyzed in this study.
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