Use of the pK Spectroscopy Method in the Study of Protolytic Properties of Humic Substances and Other Soil Polyelectrolytes

A common technique for the potentiometric analysis of complex protolytic systems is mathematical data processing. This approach allows for transforming the experimental titration curve into a function of the ionogenic group distribution of the titrated object by the values of the pK (−lgKa) acid dissociation. This distribution function is called the pK spectrum, and the approach itself is called pK spectroscopy. In this case, solutions are found not in the form of discrete dissociation constants but as a distribution function of the concentrations of ionogenic groups over a continuous spectrum of dissociation constants. The purpose of this work is to test the possibility of using the pK spectroscopy method for assessing the acid–base properties of humic substances, water-soluble fraction, and soils. The results of testing the pK spectroscopy method showed that this method is expressive and more informative than the traditional method of continuous potentiometric titration. The use of the pK spectroscopy method for studying the protolytic properties of humic substances and other environmental objects is justified. The content and values of pK of ionogenic groups of fulvic acids, water-soluble fraction, and soil suspensions were determined. In the objects, the presence of three to five ionogenic groups with pK values from 3.2 to 9.6 was revealed.

Organophosphorus Polyurethane Ionomers as Water Vapor Permeable and Pervaporation Membranes

Organophosphorus polyurethane ionomers (AEPA-PU) based on aminoethers of ortho-phosphoric acid (AEPA) were obtained and studied as pervaporation membrane materials for separating isopropanol/water mixtures. The regularities of the change in the water vapor permeability of AEPA-PU were also investigated. It has been established that an increase of solute content in the composition of the urethane-forming system and the content of ionogenic groups in AEPA leads to a noticeable increase in the vapor permeability of the resulting film materials. An increase in water vapor permeability values is accompanied by a significant increase in the pervaporation characteristics of AEPU-PU. It was shown that the conditions promoting clustering of phosphate anions cause an increase in the values of the vapor permeability coefficient of AEPA-PU obtained using polyoxypropylene glycol. However, the hydrophobicity of the polypropylene glycol surrounding the clusters makes it difficult for water to move through the polymer matrix. Due to the hydrophilicity of polyoxyethylene glycol, the highest values of water vapor permeability and pervaporation characteristics are achieved for AEPA-PU synthesized using PEG.

Sorption of Uranium (VI) Ions by a Sorbent Based on a Copolymer of Maleic Anhydride with Styrene Modified by N, Nand#39;-diphenylguanidine

In this paper the results of a study on the extraction and concentration of micro-quantities of uranium (VI) with a polymeric chelating sorbent with fragments of N, N and#39;diphenylguanidine is discussed. There was studied a static sorption capacity on K+ ions ((SSC = 9.3 mmol / g) and there were determined the ionization constants of ionogenic groups ( =3.97; =8.47) by potentiometric titration. The optimal conditions of the sorption of elements (pHopt, sorption time - τ, the influence of ionic strength - μ) were determined by the dependence of the sorption capacity (SC, mg/g) on the parameter being studied; the sorption capacity of the sorbent (SC) was determined from the saturation curve constructed under optimal sorption conditions. The maximum degree of extraction of uranium by sorbents is achieved from solutions with pH 5. Sorption equilibrium is achieved within 2 hours of contact of the solution with the sorbent. With an increase in the concentration of the uranyl ion in the solution, the amount of the sorbed metal increases, and at a concentration of 8•10–3 mol/l, it becomes maximal (pH = 5, = 8•10–3 mol/l, Vgen = 20 ml, msorb. = 0.05 g, SC = 1258 mg/g). Limits of detection (3, n=20) are 13.9 ng/ml. The effect of various mineral acids(HClО4, H2SО4, HNО3, HCl) with the same concentrations on the desorption of uranium (VI) from the sorbent was studied. The developed technique was applied to determine uranium in oil sludge.

Nanoreactor Effect in Bifunctional Cation Exchangers Based on Cis-Metacyclophanoctol

The nanoreactor effect consisting in sufficiently high rate increase of a cation diffusion flux in bifunctional cation exchangers based on cis-metacyclophanoctol has been found. The solutions of the fundamental differential equation of cation diffusion in bifunctional cation exchangers containing sulfonic acid and phenol ionogenic groups by means of the spherical layer and plane sheet models are presented for a variety of initial and boundary conditions with constant diffu-sion coefficient.