2-MERCAPTOBENZOTHIAZOLE AND DERIVATIVES IN THE FLOTATION OF GALENA, CHALCOCITE AND SPHALERITE - A STUDY OF FLOTATION, ADSORPTION AND MICROCALORIMETRY

The results of flotation, using 2-mercaptobenzothiazole (MET) and its derivatives, 6-methyl-MBT (MMBT), 6-methyloxy-MBT (MOMBT), 6-propyloxy -MBT (PrOMBT), and 6-pentyloxy-MBT (POMBT) on pure mineral samples sho wed some important advantages in the flotation of galena at neutral pH and low collector dosages. It has been found that MBT shows a high af finity towards surfaces containing lead and copper but no selectivity. The introduction of a pentyloxy ring substituent led to a change in t he adsorption kinetics, as shown by microcalorimetry, and an improveme nt of the affinity towards galena. The basic mechanism of adsorption o f MBT on galena and chalcocite has been studied by thermochemical meas urements, showing that the adsorption mechanisms of MBT on both minera ls are comparable in the initial step, involving the chemisorption of the collector. At concentrations above monolayer a second surface reac tion of MBT on galena has been observed and attributed to an oxidative dimerisation. Comparative experiments on adsorption properties of mer capto-benzo-oxazole (MBO) show the important role of the endocyclic el ement composition on the sorption process. The endocyclic O-atom in MB O prevents chemisorption on galena whereas strong coordinative bonds w ill be formed on Cu containing surfaces. (C) 1997 Published by Elsevie r Science Ltd.