In this paper, magnesium hydroxide has been obtained from seawater by a well-known industrial process which involves the chemical reaction between magnesium ions of seawater with dolomite lime to ...produce the magnesium hydroxide precipitate. Furthermore, the precipitate was modified by ultrasound of high intensity. The purpose was to obtain magnesium hydroxide with high purity and reduced particle size without agglomeration. The precipitated magnesium hydroxide is characterized by the particle size distribution determined by the laser scattering method in the range of 20 nm–2 mm, and by the SEM analysis. Likewise, in order to investigate the effect of particle size on the thermal stability, thermokinetic study of magnesium hydroxide samples was performed by non-isothermal thermogravimetry in an inert atmosphere at different heating rates. The gained thermogravimetric data were utilized for the kinetic analysis, which was performed by using the isoconversional Friedman method in combination with the multivariate nonlinear regression method. For each degradation stage of investigated samples, kinetic parameters (activation energy, pre-exponential factor and kinetic model) were calculated and compared.
High purity magnesium hydroxide has been synthesised from seawater with the addition of dolomite lime as reagent. High intensity ultrasound-assisted crystallization of magnesium hydroxide was carried ...out during precipitation with the intention to obtain fine particles of Mg(OH)2 as well as to prevent their agglomeration. Investigations were conducted on magnesium hydroxide samples in the form of sludge and voluminous powder. The composition, morphology, and properties of the product were determined by chemical, XRD, FTIR, and SEM/EDS analysis. The particle size distribution was detected by the laser light scattering method. The results showed that the mean particle size of magnesium hydroxide sludge was 5.75 µm, while voluminous powder was 7.58 µm. The morphology of magnesium hydroxide voluminous powder was in the form of aggregated filamentous (up to 300 nm in size) or flake structures.
Magnezijev hidroksid visoke čistoće sintetiziran je iz morske vode uz dodatak dolomitnog vapna. Ultrazvukom visokog intenziteta potpomognuta kristalizacija magnezijeva hidroksida tijekom precipitacije odvijala se u svrhu dobivanja što finijih čestica Mg(OH)2 i sprječavanja njihove aglomeracije. Ispitivanja su provedena na uzorcima magnezijeva hidroksida u obliku mulja i voluminoznog praha. Sastav, morfologija i svojstva dobivenog produkta analizirani su kemijskom, XRD, FTIR i SEM/EDS analizom. Raspodjela veličine čestica određena je metodom raspršenja laserskog svjetla. Rezultati ukazuju na to da je srednja veličina čestica magnezijeva hidroksida u obliku mulja 5,75 µm, dok je u voluminoznom prahu 7,58 µm. Morfologija voluminoznog praha magnezijeva hidroksida je u obliku aglomeriranih nitastih (duljine do 300 nm) i ljuspičastih struktura.
The purpose of this study was to investigate the influence of a rinsing of
Mg(OH)2 precipitated from seawater by substoichiometric precipitation (80%
precipitation) and the addition of TiO2 on ...microstructural characteristics of
the MgO obtained by sintering at low temperature (1400?C). The results of
examination indicate that the method of rinsing of the magnesium hydroxide
precipitate in the technological process of obtaining MgO from seawater
significantly affects the chemical composition of samples, primarily with
regard to the CaO and B2O3 content. The samples were doped with TiO2 to
improve the evaporation of B2O3 and sintering of MgO samples that were
characterized by XRD and SEM/EDS. These techniques confirmed the high purity
of MgO samples obtained and the formation of secondary compounds in very
small quantities that have a positive effect on the densification.
nema
In this study, seawater bittern, a by-product of sea salt production containing a concentrated inorganic substance, was used to recover magnesium in the form of nanostructured magnesium ...hydroxide/oxide. Mg(OH)
2
/MgO nanostructures from seawater bittern were synthesized by a precipitation method with different addition of PVA surfactants. The aim of this study was to investigate the effects of PVA surfactant on the morpho-structural properties and thermal behavior of MgO nanostructures. Simple control of the morphology and particle size of MgO nanostructures obtained by the addition of PVA was performed during synthesis. XRD structural analysis showed that the synthesized MgO samples have good crystalline nature. The average crystallite size of the samples is 26 nm, 26 nm, 23 nm, 24 nm, 23 nm and 23 nm, respectively, which decreases with increasing PVA content. Based on the average particle size, the optimum addition of poly(vinyl alcohol) is at a mass ratio of 1:1.5, since the smallest particles are obtained and have a uniform distribution. The SEM and TEM observations show an improvement in the agglomeration behavior of MgO nanoparticles by increasing the PVA content. The constituents of the samples were confirmed by XRF and EDS analysis.
In order to improve the properties of sintered MgO (80 % precipitation) obtained from seawater, an investigation was carried out with (0, 1, 2) w/% of nano-TiO2 and micro-TiO2 additions during ...sintering at a temperature of 1500 °C (1 h and 2 h). The effects of the TiO2 addition on its microstructural properties, density, porosity and chemical composition after sintering were observed. The SEM/EDS analysis confirmed the formation of a homogeneous microstructure composed mainly of periclase grains and well-distributed secondary phases. CaTiO3 and MgTiO4 are predominantly located at the inter- and intra-periclase grain boundary surfaces during cooling. The microstructure of the MgO samples with the addition of nano-TiO2 become more compact, having a positive impact on the porosity and density of the samples. The addition of 1 w/% of nTiO2 represents the optimal amount for the improvement of the properties of the MgO samples (80 % precipitation) obtained from seawater.
We have examined the effect of distilled water with a pH of 12.50 during the rinsing of a precipitate of magnesium hydroxide, obtained from seawater by sub-stoichiometric precipitation with 80% of ...the stoichiometric quantity of dolomite lime as the precipitation reagent. However, with this precipitation method the content of B2O3 in the product increases, i.e., magnesium oxide obtained from seawater. The purpose of this study was not only to reduce the B2O3 quantity as much as possible, but also to determine the minimum number of rinses needed to obtain calcined magnesium oxide with a satisfactory quality. Specifically, boron causes significant disturbances in the electrolysis of magnesium chloride used to obtain metal magnesium if magnesium chloride obtained from seawater is used as the cell charge, and it also adversely affects the quality of the refractory material produced from the sintered magnesium oxide obtained from seawater. The results indicate that if this method of rinsing the magnesium hydroxide precipitate is used, the B2O3 content in the MgO samples (80% precipitation) is 0.069 mass %, which is 66% less than the B2O3 content in samples prepared without rinsing the magnesium hydroxide with alkalized distilled water (B2O3 = 0.200 mass %). We found that it is sufficient to carry out the rinsing by decantation three times, as further rinsing does not cause a further reduction in the amount of B2O3 in the sample. This rinsing method does not change the CaO content in calcined magnesium oxide, which indicates that further rinsing should be done with non-alkalized distilled water.
Magnezijev hidroksid visoke čistoće sintetiziran je iz morske vode uz dodatak dolomitnog vapna. Ultrazvukom visokog intenziteta potpomognuta kristalizacija magnezijeva hidroksida tijekom ...precipitacije odvijala se u svrhu dobivanja što finijih čestica Mg(OH)2 i sprječavanja njihove aglomeracije. Ispitivanja su provedena na uzorcima magnezijeva hidroksida u obliku mulja i voluminoznog praha. Sastav, morfologija i svojstva dobivenog produkta analizirani su kemijskom, XRD, FTIR i SEM/EDS analizom. Raspodjela veličine čestica određena je metodom raspršenja laserskog svjetla. Rezultati ukazuju na to da je srednja veličina čestica magnezijeva hidroksida u obliku mulja 5,75 µm, dok je u voluminoznom prahu 7,58 µm. Morfologija voluminoznog praha magnezijeva hidroksida je u obliku aglomeriranih nitastih (duljine do 300 nm) i ljuspičastih struktura.
Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna .
The process of activated sintering of magnesium oxide obtained from sea water (by precipitation with 80 % and 120 % of the stoichiometric quantity of the dolomite lime) was examined with addition of ...1, 2 and 5 wt.‐% TiO2, at temperatures of 1600 °C and 1700 °C with soaking at the maximum temperature of 1, 3 and 5 hours, respectively. The product density and porosity were examined and the dependencies obtained were described by appropriate analytical expressions. The compatibility relationships between the addition of TiO2 and the B2O3 content in the sintered magnesium oxide samples were determined, based on an important theorem due to Onsanger. The phenomenological cofficients were calculated for two irreversible processes, namely, those of formation of Ca2B2O5and CaTiO3, respectively.
This paper aims to determine operating conditions that might be used in the production of good‐quality sintered magnesium oxide, i.e., magnesium oxide with a low boron oxide content. To this end, the process of activated sintering of magnesium oxide obtained from sea water (by precipitation with 80 % and 120 % of the stoichiometric quantity of the dolomite lime) was examined with the addition of 1, 2 and 5 wt.‐% TiO2, at temperatures of 1600 °C and 1700 °C with soaking at the maximum temperature of 1, 3 and 5 hours, respectively. The values and results obtained for the sintered MgO samples were investigated and analyzed by the authors.
To determine in-hospital and post-discharge mortality, readmission rates, and predictors of invasive mechanical ventilation (IMV) in patients treated at intensive care unit (ICU) due to acute ...exacerbations of chronic obstructive pulmonary disease (AECOPD).
A retrospective observational cohort study included all patients treated at a respiratory ICU for AECOPD during one year. A total of 62 patients (41 men) with mean age 68.4±10.4 years were analyzed for outcomes including in-hospital and post-discharge mortality, readmission rates, and IMV. Patients' demographic, hematologic, biochemical data and arterial blood gas (ABG) values were recorded on admission to hospital. Mean duration of follow-up time was 2.4 years.
Of 62 patients, 7 (11.3%) died during incident hospitalization and 21 (33.9%) died during the follow-up. The overall 2.4-year mortality was 45.2%. Twenty nine (46.8%) patients were readmitted due to AECOPD. The average number of readmissions was 1.2. Multivariate analysis showed that blood pH, bicarbonate levels, low albumin, low serum chloride, and low hemoglobin were significant predictors of IMV during incident hospitalization (P<0.001 for the overall model fit).
High in-hospital and post-discharge mortality and high readmission rates in our patients treated due to AECOPD at ICU indicate that these patients represent a high risk group in need of close monitoring. Our results suggested that anemia, hypoalbuminemia, and elevated troponin levels were risk factors for the need of IMV in severe AECOPD. Identification of such high-risk patients could provide the opportunity for administration of an appropriate and timely treatment.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Aim To determine in-hospital and post-discharge mortality, readmission rates, and predictors of invasive mechanical ventilation (IMV) in patients treated at intensive care unit (ICU) due to acute ...exacerbations of chronic obstructive pulmonary disease (AECOPD). Methods A retrospective observational cohort study included all patients treated at a respiratory ICU for AECOPD during one year. A total of 62 patients (41 men) with mean age 68.4 + or - 10.4 years were analyzed for outcomes including in-hospital and post-discharge mortality, readmission rates, and IMV. Patients' demographic, hematologic, biochemical data and arterial blood gas (ABG) values were recorded on admission to hospital. Mean duration of followup time was 2.4 years. Results Of 62 patients, 7 (11.3%) died during incident hospitalization and 21 (33.9%) died during the follow-up. The overall 2.4-year mortality was 45.2%. Twenty nine (46.8%) patients were readmitted due to AECOPD. The average number of readmissions was 1.2. Multivariate analysis showed that blood pH, bicarbonate levels, low albumin, low serum chloride, and low hemoglobin were significant predictors of IMV during incident hospitalization (P < 0.001 for the overall model fit). Conclusion High in-hospital and post-discharge mortality and high readmission rates in our patients treated due to AECOPD at ICU indicate that these patients represent a high risk group in need of close monitoring. Our results suggested that anemia, hypoalbuminemia, and elevated troponin levels were risk factors for the need of IMV in severe AECOPD. Identification of such high-risk patients could provide the opportunity for administration of an appropriate and timely treatment.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
