Abstract: An account is given of the chemical and physical properties of polychlorinated biphenyls (PCB) and assessment of existing PCB destruction technologies. Information is provided on PCB treatment technologies and PCB non-incineration destruction technologies. Analysis of market technologies for PCB destruction in accordance with the Stockholm Convention (2001) is presented. A review of companies offering PCB removal from transformers, transformer liquids, capacitors, and capacitor liquids is also given. Principal methods of PCB destruction and elimination involve incineration, gas-phase chemical reduction, catalytic dehalogenation, reduction by sodium, indirect electrochemical oxidation, catalytic hydrogenation, etc. Most convenient technologies for PCB destruction and removal from transformers, capacitors and liquids for interested Bulgarian bodies and organizations are indicated.

Abstract: Different methods for synthesis of metal vanadates are described and critically evaluated. The method of precipitation has limited application, besides voluminous solutions should be used. Sol-gel methods ensure a high dispersity of the final products but they are rather expensive and complicated for wide application. Direct synthesis from oxide precursors is a simple approach; however, being limited by diffusion phenomena it requires much time and high temperature treatment. The melt quenching method demands a strict control of a number of parameters. Direct mechanochemical synthesis proved to be also a promising method, independent of energy consumption. Comparison of the advantages and disadvantages of the methods under consideration could be helpful in choosing the method of preparation of vanadates with desired final characteristic features.