GB662463A - Improvements in the recovery of diamonds - Google Patents

Abstract

662,463. Electrostatic separators. INDUSTRIAL DISTRIBUTORS (1946), Ltd. Feb. 25, 1949. [March 9, 1948] No. 5266/49 Class 72. In an electrostatic process for the separation of diamonds from gangue, the lower surface conductivity of the diamonds is utilized to bring about physical separation. In one form, Fig. 1, the diamondiferous material is fed through a vibrating feeder 11, heated (e.g., by infra-red elements) at 12, on to an earthed metal conveyer roller 13 which moves the material through an electrostatic field formed between the conveyer roller 13 and a pin-point electrode 14 preferably of positive polarity, A rionmetallic roller 15 which is charged to the same sense as roller 13 attracts the gangue, which has the higher surface conductivity, towards the roller so that it falls in the hopper 18, whilst the diamonds are repelled and fall in the hopper 19. The material may be treated with a mixture of sodium bichromate and sulphuric acid to clean the diamonds and may also be treated with an aqueous solution of “ to 2 per cent common salt to make the gangue more conductive. In a further process in which the round and flat diamonds are separated, Fig. 2, a charge is induced to the diamonds on the conveyer belt 23 by an electrode 26, and round diamonds (viz. those having the smallest contact area) fall into a bin 27, flat diamonds adhere to the belt and are knocked into the bin 31 by a brush 30, the remainder being removed by a scraper 29, falling into the bin 28.