Pilot-Scale Test Results of Electrodialysis Bipolar Membrane for Reverse-Osmosis Concentrate Recovery

In this study, it is aimed to investigate the potential of electrodialysis bipolar membrane (EDBM) systems for the recovery of the concentrate originating from an organized industrial estate (OIE) wastewater treatment system with reverse osmosis (RO). Acids and bases were obtained from a pilot-scale treatment plant as a result of the research. Furthermore, the sustainability and affordability of acids and bases obtained by EDBM systems were investigated. Six cycles were carried out in continuous-flow mode with the EDBM system as batch cycles in the disposal of the concentrate and the production of acids and bases with the EDBM system. For each cycle, the EDBM system was operated for 66, 48, 66, and 80 min, respectively, and the last two cycles were operated for a total of 165 min (70 + 90) with 5 min of waiting. In the EDBM system, a working method was determined such that the cycle flow rate was 180 L/hour, energy to be given to the system was 25 V, and the working pressure was in the range of 0.8–2.5 bar. In the six cycles with the EDBM system, the concentrate, acid and base, conductivity, pH, and pressure increase values were investigated depending on time. Throughout all these studies, the cycles were continued over the products formed in the acid and base chamber. As a result of all the cycles, acid (HCl) production at a level of 1.44% and base (NaOH) production at a level of 2% were obtained.

A simple theoretical, quantitative approach to help understand the titration of weak acids and bases

What happens at the very beginning of the titration of a weak acid or base is a question sometimes asked by undergraduate students when introduced to the concept of buffer solution. To attempt to answer this question, a simple quantitative approach is developed, which also allows explaining more general properties of the weak acid or weak base titration process, while serving as well as an introduction to the theoretical, quantitative treatment of this subject. Using this approach, it can be shown that, at the beginning of the titration, the reaction between a weak acid (base) and a strong base (acid) does not occur on a one to one ratio when very small amounts of the strong base (acid) are added.

Difficult Topics in the Chemistry Curriculum – Bulgarian Students‘ View

Chemistry is often considered a difficult subject, and the way students perceive learning affects their achievements. The research aims to identify: the topics in the secondary Chemistry curriculum perceived as difficult and as interesting by the Bulgarian students, the reasons for students’ difficulties and ways to overcome it. An inquiry was conducted with 321 students aged 16 – 17 years. According to them, the most difficult topics are Organic Chemistry and Chemical calculations (abstract and requiring specific skills). The most interesting topics are Organic Chemistry and Theory of Electrolytic Dissociation. Acids and bases. There is no significant correlation between levels of perceived difficulty and interest. Students relate difficulties to: information overload, emphasis on memorization, and lack of connections to everyday life. More lab activities and the practical application of the knowledge are recommended. Our research results can help improve Chemistry curricula and teaching practice.

Software development for calculating concentration in a buffer to the preparation of background electrolyte in the analytical method of capillary electrophoresis

pH buffers of weak organic acids and bases are essential in capillary electrophoresis (CE) analyses, primarily when contactless conductivity detectors (C4D) are used. However, the preparation of a buffer with a known concentration of one component for use as a background electrolyte (BGE) in CE-C4D usually requires a pH adjustment to the desired value and an approximate calculation to estimate the concentration of the second component. This study developed software that allowed determining the concentration of one component when knowing the concentration of another component and the pH of the solution, taking into account the influence of ionic strength. The software was built in C# language with Windows Form interface on Microsoft Visual Studio. With the concentrations calculated from the developed software, the differences (|ΔpH|) between pH values of the obtained BGEs in practice and the desired values were smaller than 0.07, corresponding to the errors of less than 2%.

Sensitivity of the phenoxy derivatives of 2,4-dihydro-5H-[1,2,3]triazolo[4,5-d]pyrimidin-5-ones to acidic and basic stimuli

Herein we report the research on the sensitivity of six hydroxy derivatives of dihydrotriazolopyrimidines (HO-DTP) to acids and bases. The UV/Vis and fluorescence spectra of these compounds were investigated with the addition of the acids and bases. Spectral data revealed the strong red shifts for emission and absorption maxima in the presence of KOH and NaOH. Moreover, two DTPs demonstrated strengthening of the emission intensity. The obtained results and data published in our previous paper demonstrated the strong and selective sensory response of DTPs to the acids and bases and elucidated relationships between the structure and sensitivity to the environment. This finding allowed us to manage these properties by introducing the combination of substituents and functionalities into the heterocyclic core. Thus, investigations demonstrated the potential of the application of DTPs as chemo- and fluorosensors for selective detection of acids and bases.

Cyclodextrin Multicomponent Complexes: Pharmaceutical Applications

Cyclodextrins (CDs) are naturally available water-soluble cyclic oligosaccharides widely used as carriers in the pharmaceutical industry for their ability to modulate several properties of drugs through the formation of drug–CD complexes. The addition of an auxiliary substance when forming multicomponent complexes is an adequate strategy to enhance complexation efficiency and to facilitate the therapeutic applicability of different drugs. This review discusses multicomponent complexation using amino acids; organic acids and bases; and water-soluble polymers as auxiliary excipients. Special attention is given to improved properties by including information on the solubility, dissolution, permeation, stability and bioavailability of several relevant drugs. In addition, the use of multicomponent CD complexes to enhance therapeutic drug effects is summarized.

Concept Inventories as a Complement to Learning Progressions

Concept inventories and learning progressions are both incomplete frameworks, but alignment between them allowed conclusions to be drawn about the validity of a learning progression. It also identified gaps in measuring student understanding about acids and bases in the various inventories.