Positron annihilation lifetime spectroscopy study of the formation of mesoporous materials from the zeolite precursor

In this work, positron annihilation lifetime spectroscopy was used for the structural characterisation of porous materials prepared from amorphous zeolite precursors acting as the starting materials and hexadecyltrimethylammonium bromide acting as a mesoporous template. The best fits of the obtained lifetime spectra provide a four-component exponential decomposition. The lifetime values of the long-lived components point to the presence of mesoporous voids. Infrared and X-ray analyses show that the obtained materials consist partly of a crystalline zeolite structure

Utjecaj koncentracije silicija i aluminija u tekućoj fazi na brzinu rasta mikrokristala zeolita A i X

Kinetics of the crystal growth of zeolites A and X was measured during their crystallization, at 80 °C, from an amorphous aluminosilicate precursor dispersed in a 1.4 M NaOH solution containing different amounts of dissolved NaAlO2 or Na2SiO3. The crystallization pathway and fractions of zeolites A and X in the crystalline end product strongly depend on the composition of the liquid phase of the crystallizing system. Analyses of the changes of the concentrations of aluminum, cAl, and of silicon, cSi, in the liquid phase as well as of the dimension, Lm, of the largest crystals of zeolites A and X during crystallization, have shown that the growth rate of zeolite A crystals is size-independent, and that the growth is governed by the reaction of monomeric and/or low-molecular aluminate, silicate and aluminosilicate anions from the liquid phase on the surfaces of growing zeolite crystals. Influence of the composition of the liquid phase of the crystallizing system on the course of crystallization process and on the growth rates of zeolite A and zeolite X crystals are discussed in terms of the possible distribution of aluminate, silicate and/or aluminosilicate anions in the liquid phase.Brzine rasta kristala zeolita A i X mjerene su tijekom kristalizacije pri 80 °C iz amorfnoga alumosilikatnoga prekursora dispergiranoga u 1,4 M otopini NaOH koja je sadržavala različite količine otopljenoga NaAlO2 ili Na2SiO3. Tijek kristalizacije i frakcije zeolita A i X u produktima kristalizacije značajno ovise o sastavu tekuće faze kristalizacijskoga sustava. Analizom promjena koncentracija aluminija, cAl i silicija, cSi u tekućoj fazi te veličine Lm, najvećih kristala zeolita A i X tijekom kristalizacije, utvr|eno je da je brzina rasta kristala neovisna o njihovoj veličini te da se rast kristala odvija reakcijom monomernih i/ili niskomolekularnih aluminatnih, silikatnih i alumosilikatnih aniona iz tekuće faze na površini rastućih kristala zeolita. Utjecaj sastava tekuće faze kristalizacijskih sustava na tijek procesa kristalizacije i brzinu rasta kristala zeolita A i X razmatran je u odnosu na moguće raspodjele aluminatnih, silikatnih i alumosilikatnih aniona u tekućoj fazi

Utjecaj koncentracije silicija i aluminija u tekućoj fazi na brzinu rasta mikrokristala zeolita A i X

Kinetics of the crystal growth of zeolites A and X was measured during their crystallization, at 80 °C, from an amorphous aluminosilicate precursor dispersed in a 1.4 M NaOH solution containing different amounts of dissolved NaAlO2 or Na2SiO3. The crystallization pathway and fractions of zeolites A and X in the crystalline end product strongly depend on the composition of the liquid phase of the crystallizing system. Analyses of the changes of the concentrations of aluminum, cAl, and of silicon, cSi, in the liquid phase as well as of the dimension, Lm, of the largest crystals of zeolites A and X during crystallization, have shown that the growth rate of zeolite A crystals is size-independent, and that the growth is governed by the reaction of monomeric and/or low-molecular aluminate, silicate and aluminosilicate anions from the liquid phase on the surfaces of growing zeolite crystals. Influence of the composition of the liquid phase of the crystallizing system on the course of crystallization process and on the growth rates of zeolite A and zeolite X crystals are discussed in terms of the possible distribution of aluminate, silicate and/or aluminosilicate anions in the liquid phase.Brzine rasta kristala zeolita A i X mjerene su tijekom kristalizacije pri 80 °C iz amorfnoga alumosilikatnoga prekursora dispergiranoga u 1,4 M otopini NaOH koja je sadržavala različite količine otopljenoga NaAlO2 ili Na2SiO3. Tijek kristalizacije i frakcije zeolita A i X u produktima kristalizacije značajno ovise o sastavu tekuće faze kristalizacijskoga sustava. Analizom promjena koncentracija aluminija, cAl i silicija, cSi u tekućoj fazi te veličine Lm, najvećih kristala zeolita A i X tijekom kristalizacije, utvr|eno je da je brzina rasta kristala neovisna o njihovoj veličini te da se rast kristala odvija reakcijom monomernih i/ili niskomolekularnih aluminatnih, silikatnih i alumosilikatnih aniona iz tekuće faze na površini rastućih kristala zeolita. Utjecaj sastava tekuće faze kristalizacijskih sustava na tijek procesa kristalizacije i brzinu rasta kristala zeolita A i X razmatran je u odnosu na moguće raspodjele aluminatnih, silikatnih i alumosilikatnih aniona u tekućoj fazi

Application of a New Functionalized MWCNTs for the Construction of Surfactant Potentiometric Sensors

The multi-walled carbon nanotubes (MWCNTs) were noncovalently functionalized with tetraoctadecylammonium tetraphenylborate (TODA-TPB) used as a sensing element and incorporated into a liquid PVC membrane of the new fast, low drift and sensitive potentiometric sensor (FCNSS) for anionic surfactants (ASs). The sensor exhibits a sub-Nernstian response for both dodecyl sulfate (DS) and dodecylbenzenesulfonate in H2O and in 10 mM Na2SO4. The lower limits of detection for DS and DBS in H2O were 1.5 · 10−7 and 2.0 · 10−7 M and in 10 mM Na2SO4, they were 2.0 · 10−7 M for both surfactants. The response time of the sensor varied between 8 and 12 s, depending on AS concentration and its signal drift was 2.1 mV/hour. The FCNSS exhibited excellent selectivity for DS against nearly all anions usually found in commercial products. It was successfully employed for end-point detection at potentiometric titrations of ASs in detergent products and effluents. This work is licensed under a Creative Commons Attribution 4.0 International License

Micro/mesoporous aluminosilicate materials via dual templating, Part 1: synthesis and characterization

In a quest for optimal synthesis procedure of hierarchically porous zeolite by dual template method, a series of materials was prepared starting from zeolite yielding precursor with an addition of surfactant as a mesoporogen. Characterization of the obtained materials showed that all samples possess micro and mesoporous structures, which ratio depends on the amount of surfactant present in the reaction mixture. However, in the most of the samples separation of phases occurred, and crystalline zeolite phase along amorphous MCM-41 like phase were detected, except for the sample obtained from the modified precursor, where only crystalline zeolite phase was obtained, with a specific and unusual morphology. Adsorption isotherm of that sample resembles the isotherms obtained for post synthesis modified samples

Trauma Related Fat Embolism Syndrome in Forensic Practice

The fat embolism syndrome (FES) in forensic practice is observed usually in cases of polytrauma related deaths. FES is rare, but serious complication after trauma. The most cases of post traumatic fat embolism are not fatal and it’s very likely that many cases of mild fat embolism are overlooked. We describe a case of fat embolism syndrome in a young man after high energy injury. Upon concrete ceiling fell on his shoulders he had open fractures of both tibias and massive haematoma of the left hip joint. Transport immobilization of both legs was performed with admitting of analgesia during transportation to the hospital. Immediately after admission to hospital he underwent surgery. Several hours after osteosynthesis of both tibias, in ICU patient became hemodinamically and respiratory unstable. He developed global cyanosis and metabolic acidosis with significant decrease of oxygen pressure in the blood. Control chest radiograph showed typical »snow-storm« like pulmonary infiltrations. Deep bradicardy occurred followed by cardiopulmonary arrest. CPR was unsuccessful and the patient suddenly died within 12 hours from the incident. Histologic confirmation of fatty droplets the most commonly observed in the lung capillaries, brain capillaries or disseminated throughout the body remains diagnostic standard. We present one case of FES to emphasize the arising need of a quantitative analysis of both the size and localization of the fat emboli in order to grade the severity of FES and its relative contribution in pathophysiology of death. The postmortem diagnosis of fat embolism syndrome (FES), traditionally based on the histological demonstration of fat globules seems not to be enough, nowadays. A quantitative analysis of both the size and localization of the fat emboli has been discussed as reliable method of grading the pulmonary fat embolism in order to determine its relative functional contribution in death pathogenesis