Refining of selenium-A review

Current developments in the semiconductor and radio electronic technique make continuously increasing demands on the purity of selenium as regards the impurity content. The selenium recovered from its raw materials which are usually the by products of some industry such as anode slimes from copper electrolysis and sulphuric acid sludge, etc, is usually 97 to 99% pure and is termed as technical or crude selenium. This grade of selenium contains a great number of elements as impurities, which must be removed, for getting ultra pure selenium required by electronic industry. This paper discusses various methods of purification so as to act as guide for selecting a combination of processes for purifying the crude selenium of a particular grade when purification of indigenously produced selenium from slimes obtained from the electrolytic refining plants of Indian Copper Industry or other raw materials will be initiated. (Narinder Singh, Scientist; S.B. Mathur, Senior Scientific Assistant and D.D. Akerkar, Scientist; National Metallurgical Laboratory)