The separation and capture of CO2 have become an urgent and important agenda because of the CO2-induced global warming and the requirement of industrial products. Membrane-based technologies have proven to be a promising alternative for CO2 separations. To make the gas-separation membrane process more competitive, productive membrane with high gas permeability and high selectivity is crucial. Herein, we developed new cellulose triacetate (CTA) and cellulose diacetate (CDA) blended membranes for CO2 separations. The CTA and CDA blends were chosen because they have similar chemical structures, good separation performance, and its economical and green nature. The best position in Robeson’s upper bound curve at 5 bar was obtained with the membrane containing 80 wt.% CTA and 20 wt.% CDA, which shows the CO2 permeability of 17.32 barrer and CO2/CH4 selectivity of 18.55. The membrane exhibits 98% enhancement in CO2/CH4 selectivity compared to neat membrane with only a slight reduction in CO2 permeability. The optimal membrane displays a plasticization pressure of 10.48 bar. The newly developed blended membranes show great potential for CO2 separations in the natural gas industry.
Currently, cellulose acetate (CA) membranes dominate membrane-based CO2 separation for natural gas purification due to their economical and green nature. However, their lower CO2 permeability and ease of plasticization are the drawbacks. To overcome these weaknesses, we have developed high-performance mixed matrix membranes (MMMs) consisting of cellulose triacetate (CTA), cellulose diacetate (CDA), and amine functionalized zeolitic imidazolate frameworks (NH2-ZIF-8) for CO2 separation. The NH2-ZIF-8 was chosen as a filler because (1) its pore size is between the kinetic diameters of CO2 and CH4 and (2) the NH2 groups attached on the surface of NH2-ZIF-8 have good affinity with CO2 molecules. The incorporation of NH2-ZIF-8 in the CTA/CDA blend matrix improved both the gas separation performance and plasticization resistance. The optimized membrane containing 15 wt.% of NH2-ZIF-8 had a CO2 permeability of 11.33 Barrer at 35 °C under the trans-membrane pressure of 5 bar. This is 2-fold higher than the pristine membrane, while showing a superior CO2/CH4 selectivity of 33. In addition, the former had 106% higher CO2 plasticization resistance of up to about 21 bar and an impressive mixed gas CO2/CH4 selectivity of about 40. Therefore, the newly fabricated MMMs based on the CTA/CDA blend may have great potential for CO2 separation in the natural gas industry.
Carbon nanotubes have exceptional mechanical properties which make them very attractive for the development of composite membranes. In this research, NH 3 /N 2 gas permeation behavior of flat sheet composite membranes was examined. The cellulose acetate-multiwalled carbon nanotubes composite membranes were synthesized using solution casting method. The morphology and dispersion of carbon nanotubes were observed through SEM. However, the composite membranes were also characterized using several analytical techniques such as X-ray diffraction analysis, tensile testing analysis, and thermal gravimetric analysis. Characterization of these membranes depicted that carboxylic group functionalized MWCNTs are extremely compatible with CA. The permeation experiments were performed with NH 3 and N 2 to explore the host-guest interaction of MWCNTs with chosen gases. The permeability of NH 3 was found pronounced compared to N 2 . The NH 3 /N 2 selectivity up to 90 was documented.
Abstract
Objective: To develop and validate a method on Dissociation Enhanced Lanthanide Fluorescence Immunoassay for neonatal heel prick blood human thyroid stimulating hormone and the establishment of its reference value in the local population.
Methods: The multi-centre cross-sectional validation study was conducted from September 2016 to September 2018 at Zahra Beau Naqvi Foundation Welfare Trust laboratory, Islamabad, Pakistan, and comprised samples related to newborns aged 1 month or less taken from neonatal units of 39 hospitals based in Punjab, Khyber Pakhtunkhuwa, Gilgit-Baltistan and Azad Jammu and Kashmir. Samples were collected after 24 hours of birth using the heel prick test. The samples were dried and sent to the laboratory for assessment where Dissociation Enhanced Lanthanide Fluorescent Immunoassay was used to estimate thyroid stimulating hormone levels. Data recorded included age, gender, and birth detail, like gestational age, mode of delivery etc. Data was analysed using SPSS 21. Method validation and reference value were manually calculated.
Results: Of the 14,147 samples received, 8,207(58%) related to boys and 5,940(42%) to girls. Most samples 4903(34.6%) came from Peshawar. The overall mean age of the newborns was 5.6±4.8 days. Thyroid stimulating hormone data was divided into three groups; positive with median value 27.8±36.6 uIU/ml, negative with median 1.42±1.60 uIU/ml, and borderline with median 11.4±4.12uIU/ml. Prevalence of congenital hypothyroidism in high-risk population in the positive group was 39(0.3%), negative 14,012(99.0%) and borderline 96(0.7%). Continuous...
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