precipitation ph
Recently Published Documents


TOTAL DOCUMENTS

64
(FIVE YEARS 20)

H-INDEX

14
(FIVE YEARS 3)

2021 ◽  
Vol 14 (4) ◽  
pp. 527-538
Author(s):  
Natalya V. Filatova ◽  
◽  
Nadezhda F. Kosenko ◽  
Artyom S. Artyushin

It was obtained aluminum hydroxide in the form of bayerite by precipitation with ammonia. The precipitation pH was found by the potentiometric titration. Based on the data of thermal, X‑ray diffraction and IR‑analysis it was identified the sequence of bayerite transitions up to 800 °C. The study of nitrogen adsorption- desorption allowed to determine a specific surface, a volume, and dimensions of pores for boehmite and γ- Al2O3 as 135±2 and 238±10 m2/g; 0.38 and 0.51 cm3/g; 1.7 and 3.8 nm, relatively. The value of effective activation energy for boehmite →γ- Al2O3 transition ((136±5) kJ/mol) was found by means of non- isothermal method (by Avrami equation)


2021 ◽  
Author(s):  
David Needham

Motivation: With the coronavirus pandemic still raging, prophylactic nasal and early treatment throat sprays that "puts the virus in lockdown", could help prevent infection and reduce viral load. Niclosamide has the potential to treat a broad range of viral infections if local bioavailability is optimized as mucin-penetrating solutions instead of microparticles that cannot penetrate the mucin. Experimental: pH-dependence of supernatant concentrations and dissolution rates of niclosamide were measured in buffered solutions by Nanodrop-UV/Vis-spectroscopy for niclosamide from different suppliers, as precipitated material and as cosolvates. Data was compared to predictions from Henderson Hasselbalch and precipitation pH models. Optimal microscopy was used to observe the morphologies of precipitated and converted niclosamide. Results: Supernatant-concentrations of niclosamide increased with increasing pH: from 1.77uM at pH 3.66 to 30uM at pH 8; more rapidly from 90uM at pH8.5 to 300uM at pH9.1, reaching 641uM at pH 9.5. Logarithmic rates for dissolution increased by ~3x for pHs 8.62 to 9.44. However, when precipitated from supersaturated solution, niclosamide equilibrated to much lower final supernatant concentrations, reflective of more stable polymorphs at each pH that were also apparent for niclosamide from other suppliers and cosolvates. Conclusions: Niclosamide is not niclosamide is not niclosamide. A low dose (20uM) prophylactic solution of niclosamide at a nasally safe pH of 7.9 and a (up to 300uM) throat spray at pH 9.1 would be one of the simplest and potentially most effective formulations from both an efficacy standpoint as well as manufacturing and distribution, with no cold chain. It now needs testing.


Foods ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1657
Author(s):  
Karolina Östbring ◽  
María Matos ◽  
Ali Marefati ◽  
Cecilia Ahlström ◽  
Gemma Gutiérrez

Rapeseed press cake (RPC), the by-product of rapeseed oil production, contains proteins with emulsifying properties, which can be used in food applications. Proteins from industrially produced RPC were extracted at pH 10.5 and precipitated at pH 3 (RPP3) and 6.5 (RPP6.5). Emulsions were formulated at three different pHs (pH 3, 4.5, and 6) with soy lecithin as control, and were stored for six months at either 4 °C or 30 °C. Zeta potential and droplet size distribution were analyzed prior to incubation, and emulsion stability was assessed over time by a Turbiscan instrument. Soy lecithin had significantly larger zeta potential (−49 mV to 66 mV) than rapeseed protein (−19 mV to 20 mV). Rapeseed protein stabilized emulsions with smaller droplets at pH close to neutral, whereas soy lecithin was more efficient at lower pHs. Emulsions stabilized by rapeseed protein had higher stability during storage compared to emulsions prepared by soy lecithin. Precipitation pH during the protein extraction process had a strong impact on the emulsion stability. RPP3 stabilized emulsions with higher stability in pHs close to neutral, whereas the opposite was found for RPP6.5, which stabilized more stable emulsions in acidic conditions. Rapeseed proteins recovered from cold-pressed RPC could be a suitable natural emulsifier and precipitation pH can be used to monitor the stability in emulsions with different pHs.


2021 ◽  
Vol 282 ◽  
pp. 119566
Author(s):  
Weidong Zhang ◽  
Kelsey Lassen ◽  
Claude Descorme ◽  
Jose Luis Valverde ◽  
Anne Giroir-Fendler

Author(s):  
A. Benkhelif ◽  
M. Kolli ◽  
M. Hamidouche

In this study, a high valued product submicronic ?-alumina is successfully extracted from aluminum slags generated by the local aluminum industry. The extraction technique is based on the leaching of slags by H2SO4 followed by precipitation. The coarser aluminum-rich fractions of the slags are used in this study instead of the finer oxide-rich fractions that were commonly used in previous studies. The precipitation of the leached slags by NH4OH is controlled by zetameter in order to determine the optimal precipitation pH. Then, the obtained gel showing the higher precipitation rate and the finer particle size is calcined at 1200 ?C and characterized by XRF, XRD, FTIR, SEM, EDS and laser granulometry. Even without any pretreatment of slags, the XRF analysis reveals that a high purity and high extraction efficiency of 99.2% and 93.75% respectively can be achieved just at a leaching acid concentration of 15%. XRD spectrum shows that the produced alumina is a pure a-corundum, which is confirmed by FTIR spectrum showing only the Al-O bonds. The laser granulometry shows that the recovered powder exhibit a wide particle size distribution. It is between 50 nm and 20 ?m while the average particle size (d50) is about 400 nm. SEM observations reveal that the grains are in the form of submicronic whiskers. The above characteristics allow the obtained alumina powder in this study to be used in the usual applications of alumina such as refractory, ceramic fibers, abrasive, etc. The obtained powders may assume also applications as a thermally stable substitute for the commonly used transition alumina powders, which need further investigations in future studies.


Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Rui Qu ◽  
Guilin Han

Rainwater is an essential pathway to remove fine particulate matter and dissolved atmospheric pollutants (e.g., SO2, HNO3, and NH3). Acid rain (pH < 5.6) has been a severe environmental issue in China since the 1970s, adversely impacting ecosystem health. This study focuses on the influence of anthropogenically induced anions (SO42– and NO3–) and alkaline cations (Ca2+ and NH4+) on acid rain in Chinese cities. In this review, cities with high population density east of the Hu Huanyong Line that divides China geographically according to its uneven economic development were studied. Coastal and central areas of China to the east of the line are characterized by a much faster developing economy and rapid urbanization. The observed trends and spatial variability of acidity and chemical composition in rainwater are discussed in relation to industrialization and environmental changes in China. Over the past 3½ decades, the precipitation pH in the urban regions has exhibited reduced acidity. A mixed nitric–sulfuric acid rain type has become prominent due to the significant decrease in SO42– via desulfurization. Ca2+ levels have decreased, while NH4+ has increased slightly due to more vehicular transportation. In addition, the neutralization capacity of Ca2+ and NH4+ has decreased from north to south. Overall, the acid rain problem in Chinese cities has been alleviated in recent years.


2020 ◽  
Vol 20 (20) ◽  
pp. 12223-12245
Author(s):  
Viral Shah ◽  
Daniel J. Jacob ◽  
Jonathan M. Moch ◽  
Xuan Wang ◽  
Shixian Zhai

Abstract. Cloud water acidity affects the atmospheric chemistry of sulfate and organic aerosol formation, halogen radical cycling, and trace metal speciation. Precipitation acidity including post-depositional inputs adversely affects soil and freshwater ecosystems. Here, we use the GEOS-Chem model of atmospheric chemistry to simulate the global distributions of cloud water and precipitation acidity as well as the total acid inputs to ecosystems from wet deposition. The model accounts for strong acids (H2SO4, HNO3, and HCl), weak acids (HCOOH, CH3COOH, CO2, and SO2), and weak bases (NH3 as well as dust and sea salt aerosol alkalinity). We compile a global data set of cloud water pH measurements for comparison with the model. The global mean observed cloud water pH is 5.2±0.9, compared to 5.0±0.8 in the model, with a range from 3 to 8 depending on the region. The lowest values are over East Asia, and the highest values are over deserts. Cloud water pH over East Asia is low because of large acid inputs (H2SO4 and HNO3), despite NH3 and dust neutralizing 70 % of these inputs. Cloud water pH is typically 4–5 over the US and Europe. Carboxylic acids account for less than 25 % of cloud water H+ in the Northern Hemisphere on an annual basis but 25 %–50 % in the Southern Hemisphere and over 50 % in the southern tropical continents, where they push the cloud water pH below 4.5. Anthropogenic emissions of SO2 and NOx (precursors of H2SO4 and HNO3) are decreasing at northern midlatitudes, but the effect on cloud water pH is strongly buffered by NH4+ and carboxylic acids. The global mean precipitation pH is 5.5 in GEOS-Chem, which is higher than the cloud water pH because of dilution and below-cloud scavenging of NH3 and dust. GEOS-Chem successfully reproduces the annual mean precipitation pH observations in North America, Europe, and eastern Asia. Carboxylic acids, which are undetected in routine observations due to biodegradation, lower the annual mean precipitation pH in these areas by 0.2 units. The acid wet deposition flux to terrestrial ecosystems taking into account the acidifying potential of NO3- and NH4+ in N-saturated ecosystems exceeds 50 meqm-2a-1 in East Asia and the Americas, which would affect sensitive ecosystems. NH4+ is the dominant acidifying species in wet deposition, contributing 41 % of the global acid flux to continents under N-saturated conditions.


Sign in / Sign up

Export Citation Format

Share Document