Search results for "acid-base propertie"

Solubility and acid-base properties and activity coefficients of chitosan in different ionic media and at different ionic strengths, at T=25°C

2009

Studies on the acid-base properties and solubility of a polyammonium polyelectrolyte (chitosan) with different molecular weights (MW 310 and 50 kDa), were performed at T=25 °C, in the pH range 2.5–7. The protonation of chitosan was investigated by potentiometry ([H+]-glass electrode) in NaCl, NaNO3 and mixed NaNO3+Na2SO4 ionic media, at different ionic strengths. Protonation constants were calculated as a function of dissociation degree α by means of two different models, namely, a simple linear model and the modified Henderson–Hasselbalch equation. Experimental data were also fitted using a model independent of α (Diprotic-like model), according to which the acid-base properties can be sim…

Protonation Constants of Halloysite Clay Nanotubes

2015

Halloysite is one of the most interesting nano-structured clay materials. It is similar to kaolin but has a hollow tubular structure that can be attributable to particular crystallization conditions. Typically, halloysite nanotubes (HNTs) are formed by 15 – 20 aluminosilicate layers, has a length of 1 ± 0.5 μm and inner and outer diameters of 1 - 30 and 30 - 50 nm, respectively [1,2]. In each layer the SiOH and the AlOH groups are disposed on the external and the internal surfaces, respectively. The particular structure of HNTs makes this kind of material very useful for different purposes in several fields. Among the various applications, worth of mention are: i) their use as additive for …

Thermodynamics of Proton Binding of Halloysite Nanotubes

2016

In this paper, new information on physical and chemical properties of the widely used nanostructured Halloysite mineral are reported. Given that the Halloysite has a tubular structure formed by a variable number of wrapped layers containing Si-OH and Al-OH groups, their proton binding affinity was measured at different ionic strengths and ionic media by means of potentiometric measurements in heterogeneous phase. One protonation constant for the Si-OH groups and two for the Al-OH groups were determined. The protonation constant values increase with increasing of the ionic strength in all the ionic media. This suggests that the presence of a background electrolyte stabilizes the protonated s…

Acid-base properties of halloysite clay nanotubes in NaCl medium

2014

Modelling the dependence on medium and ionic strength of molybdate acidbase properties, and its interactions with phytate

2016

The importance of molybdenum from a biological, environmental and technological point of view is very well known since many decades [15]. In particular, it is mainly present in aqueous solutions as molybdate (MoO42), which is the biologically active form, entering in the cells by active transport systems. Though molybdate is the major species in neutral to basic pH conditions, at lower pH it undergoes protonation and, chiefly, polymerization, even at millimolar concentration levels [2]. Consequently, the modelling of its speciation and acidbase properties is not very simple, as demonstrated by the nonhomogeneity of available literature data. In this light, our group has started a systematic…

A study on the acid-base properties of pectin and poly-galacturonic acid

2008

Modelling the dependence on medium, ionic strength and temperature of N-acetyl-L-cysteine acid-base properties, and its interactions with Na+, Mg2+, …

2017

N-acetyl-L-cysteine (NAC) is the acetylated precursor of L-cysteine, and it is strictly related to glutathione activity. NAC is used in medicine since more than 30 years, primarily as a mucolytic, though its properties are exploited in the treatment of many diseases, such as acute poisoning by acetaminophen (restoring protective levels of glutathione), HIV, contrast-induced nephropathy, type-2 DM (diabetes mellitus), and it also looks promising in the treatment of several psychiatric disorders [1]. This resulted in a huge number of scientific contributions published during the years on NAC (searching in some scientific databases, more than 10000 papers appear). As expected, most of them are…