Andre Chesne

Purification of waste waters containing heavy metals; by surfactant liquid membrane extraction

The aim of this work is to find a process for the purification of waste waters containing cadmium, lead and mercury.

Extraction of Uranium from Heap Leaching Solutions by Liquid Surfactant Membranes

ABSTRACT A pilot scale liquid surfactant membrane process, designed to purify and concentrate uranium from heap leaching solutions, has been developed. The process is based on a carrier-mediated transport of uranium by a tertiary amine, and stripping by a mixture of sodium carbonate and sodium hydroxide. During batch experiments, membrane composition had been previously adjusted in order to promote uranium transfer, using a volumetric ratio of external phase to internal phase of 40. In a laboratory pulsed column (with flowrates up to 10 l/h), operating parameters have been optimized, through hold-up measurements, by establishing a relationship between the emulsions residence time in the column and the depletion of uranium in the external phase. Pilot scale testing of the complete process has been performed using a 10 cm diameter by 1 m height pulsed column. Treatment of a leach solution containing 240 mg/l of uranium with a flowrate of 116 l/h, has yielded an extraction recovery of 97 %. Crud formation does not hinder uranium transfer. Small amounts of iron contaminating the internal phase are easily removed by filtration. A pure solution of uranyl carbonate containing over 5 g/l of uranium is recovered, which is ready for yellow-cake precipitation.