Microwave synthesis of sulfanilic acid

Sulfanilic acid represents an important substance, which is frequently utilized in the industry of azo dyes as well as in drug development of antimicrobials (e.g. of sulfonamides). Students can also meet with such type of compounds in chemistry labs, for example, when they estimate pH by methyl orange indicator or prepare Orange II for textile colouring. Both of these dyes are products of azo coupling of sulfanilic acid as diazonium salt with N,N-dimethylaniline or 2-naphthol, respectively. In the article, we focus on the synthesis of sulfanilic acid as a well-known experiment in the organic chemistry education. The synthesis was modified as the solvent free and microwave assisted experiment under semimicroscale conditions. That experiment is very convenient for the organic chemistry courses in the university or the high school teaching.

Concrete and cement composites used for radioactive waste deposition

This review article presents the current state-of-knowledge of the use of cementitious materials for radioactive waste disposal. An overview of radwaste management processes with respect to the classification of the waste type is given. The application of cementitious materials for waste disposal is divided into two main lines: i) as a matrix for direct immobilization of treated waste form; and ii) as an engineered barrier of secondary protection in the form of concrete or grout. In the first part the immobilization mechanisms of the waste by cement hydration products is briefly described and an up-to date knowledge about the performance of different cementitious materials is given, including both traditional cements and alternative binder systems. The advantages, disadvantages as well as gaps in the base of information in relation to individual materials are stated. The following part of the article is aimed at description of multi-barrier systems for intermediate level waste repositories. It provides examples of proposed concepts by countries with advanced waste management programmes. In the paper summary, the good knowledge of the material durability due to its vast experience from civil engineering is highlighted however with the urge for specific approach during design and construction of a repository in terms of stringent safety requirements.