Percolation leaching of clay mixed copper ores

Abstract

The present work addresses the problem of improving the percolation properties of heap leaching piles of clay, slime-oxidised and mixed ores. These ores are prone to colmatation, which hinders percolation of the solution through the ore layer. Laboratory tests on percolation leaching were carried out using a 2 m column having an internal diameter of 190 mm, loaded with 89.42 kg of ore material having a grain size of -55+0 mm. In order to eliminate colmatation, the ore layer was divided into two equal parts by a drainage layer of polystyrene foam. The research object was ore material extracted from the northern Nurkazgan deposit (Karaganda region, Republic of Kazakhstan), in which copper is present in the form of sulphide (53.48%) and oxidised minerals (46.52%), including 23.5% of chrysocolla. The mineral composition of a test sample determined by optical and electron microscopy, X-ray diffraction, local X-ray spectral, X-ray fluorescence and inductively coupled plasma mass spectrometry was characterised by 93.78% of rock-forming minerals, 53.23% of which comprised layered silicates, namely, mica, chlorite and kaolinite. Ore mineralisation was characterised by both sulphide (copper sulphides, pyrite) and oxide (malachite, iron hydroxides and manganese oxides) phases. The content of easy-sliming minerals equalled 56.30%. Prior to leaching, moisture saturation during the period of one day was carried out. The ore was top irrigated with a solution of sulphuric acid having a concentration of 60 g/dm3. Pregnant solutions were processed following a sorption method (sorption/desorption–electrolysis). The copper extraction into the solution yielded 60.04% with a sulphuric acid consumption of 50.0 kg/t ore at an average irrigation rate of 10.58 dm3/(m2h) or 0.1058 dm/h per clear opening. Therefore, heap leaching of ores at a layer height of lower than 1 m can be performed following the "leaching–extraction/re-extraction or sorption/desorption–electrolysis" scheme.