Determination of total cyanide in gold-mill effluents by an automated flow injection-spectrophotometric method

Abstract EN

An automated flow injection method has been developed for the determination of total cyanide in gold-mill effluents.

The system is based on the dissociation of metallocyanide complexes by ultraviolet (u.v.) irradiation-of the acidified sample solution, followed by separation of the resultant hydrogen cyanide by gas-diffusion throuh a porous Teflon membrane.

Cyanide is ultimately determined by the sodium barbiturate-sodium isonicotinate spectrophotometry method.

Photodecomposition of thiocyanate to cyanide was prevented by incorporating a Pyrex filter sleeve around the u.v.

lamp.

Results obtained for several gold-mill effluent samples by this flow system compared well with, and more precise than, those obtained by the American Society for Testing and Material, ASTM manual distillation method.

The detection limit is 0.003 ug ml"1 and the sample throughput is 9 per hour.