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This study investigates the electrochemical behavior of pyrite in collectorless and DTPI (sodium disobuthyldithiophosphinate) induced conditions to identify the nature of interactions between pyrite and DTPI with respect to pulp pH and pulp potential (Eh). Electrochemical investigation from acidic to alkaline (pH = 4.67- 11.0) conditions were performed using cyclic voltammetry technique in cathodic to anodic potential range (-505 to +595 mV SHE). DRIFT spectroscopy were also done after polarization at varying potentials and pH, to identify pyrite surface and to express adsorption mode of DTPI. Pyrite surface was seen to display characteristic electrochemical behavior according to pulp pH. Hydrophobic nature of pyrite in acidic condition turned into hydrophillic form with increase in solution pH with regard to the changes in pulp potential. In DTPI induced condition, intensity of redox reactions, related to S 0 formation, decreased at acidic pH due to surface passivation with DTPI adsorption. No apparent differences occurred in the pyrite volttamograms after DTPI addition in other pHs. Adsorbance of DTPI on pyrite relied mainly on chemical means, irrespective of pulp potential. DRIFT studies revealed that DTPI adsorbed in dimer form on pyrite and acidic pulp favored its adsorption. DRIFT patterns also confirmed that interaction among pyrite and DTPI relied mainly on chemical means.
Tailings issued from polymetallic ore flotation of Chaabat el-Hamra mine contain sulfides such as Galena (PbS), Pyrite (FeS2) and Chalcopyrite (CuFeS2). They present environmental threats such as the acid mine drainage. Chemical analysis showed that the major element of these tailings is Pyrite. The processing of the latter eliminates much of the sulfur. The flotation is based on the difference of the minerals surface properties such as hydrophobicity, hydrophility, addition of appropriate reagents and their adhesion to bubbles. In this work, we propose to use the method of thermodynamic analysis in view of studying and identifying the main physico-chemical parameters of flotation, such as the thermodynamic potential and pH, which play a main role in collector adsorption on the mineral surface. The obtained results show that the optimal pH value is 7, in this condition; we can get an optimal adsorption and maximum recovery of Pyrite up to 90%.
Dithiophosphatogen is the species responsible for flotation of pyrite when dithiophosphate is added as collector. Oxidation of collector apparently occurs by reaction with oxygen adsorbed on the pyrite surface. Oxidation of dithiophosphate and xanthate is also effected with CuUU, Cu hydroxide, and FeUUU, and rates of oxidation are presented as a function of pH. Reasons for the selectivity observed when dithiophosphate is added as collector in a natural ore system as compared to xanthate are presented and discussed.
Cadmium sometimes occurs as a minor impurity in cobalt–nickel solutions which are to be processed by solvent extraction for the recovery of cobalt. However, the organophosphorus reagents used for this purpose extract cadmium in preference to cobalt. Consequently, the feed solutions must be pretreated for the removal of cadmium in order to avoid contamination of the final product. This note describes a selective method of removing cadmium by precipitation as its diisobutyldithiophosphinate complex.
The fundamental mechanisms of dicresyl monothiophosphate (DCMTP) adsorption on gold, silver and gold-silver alloys have been investigated in the present work. The monothiophosphates are obtained by replacing one of the sulfur donors in the functional group of the corresponding dithio derivatives with oxygen. This substitution results in a true acid-circuit collector for bulk sulfide flotation that has also been found to increase gold recovery from primary gold ores. Voltammetric studies indicate that the adsorption of DCMTP is probably the result of a coupled chemical reaction involving an initial electron transfer step (E), followed immediately by a chemical reaction (C). Thus, the adsorption of DCMTP is controlled by both the Eh and pK of the system. FTIR spectroscopic and contact angle measurements conducted under controlled potential conditions showed that DCMTP adsorption is potential-dependent. There are no indications of DCMTP adsorption on gold observed in these measurements.
Interpretation and implications of pulp potentials in the flotation of sulfide minerals are presented. Mechanisms of sulfide flotation are reviewed in terms of the mixed potential model for both self-induced and collector-induced flotation. The effects of galvanic interactions among different minerals and grinding media on flotation are summarized.
Using the criteria of recovery and rate, the flotation of the principal copper sulfides and pyrite with sulfhydryl collectors was found to follow the pattern: xanthate > dithiophosphate = thionocarbamate = xanthogen ethyl formate > dixanthogen. Flotation rate was found to be a more sensitive parameter than recovery; especially as near-ultimate recovery is approached. The differing response of these five minerals to the anionic xanthate or dithiophosphate collectors was found to correspond to the mineral semiconductor type. As the pH increases from pH 5 to 10.5 both recovery and rate were generally found to decrease with all the sulphydryl collectors except dixanthogen.
The effect of sulphite and ferric species on the collector-induced flotation of chalcopyrite has been studied, while the effect of these species on the rate of dicresyl dithiophosphate (DCDTP) adsorption has been monitored in situ using UV spectroscopy.Chalcopyrite, which had been previously conditioned with Fe(III) species, exhibited decreased affinity for DCDTP adsorption. Under these conditions, the flotation rate and recovery of chalcopyrite was reduced. The extent of flotation depression by iron oxyhydroxide depended on pH, conditioning gas, and the presence of adsorbed collector on chalcopyrite.Prior interaction of the chalcopyrite surface with sulphite significantly increased both the adsorption rate as well as the surface coverage of DCDTP on chalcopyrite. Sulphite removes adsorbed iron oxyhydroxide, present due to its specific introduction or oxidation of chalcopyrite, from the chalcopyrite surface and promotes the formation of an iron-deficient chalcopyrite. The rate of DCDTP adsorption onto chalcopyrite was increased due to both removal of iron oxyhydroxide previously existing on the chalcopyrite surface and the formation of an iron-deficient chalcopyrite. Under these conditions, the flotation rate and recovery of chalcopyrite was increased. Reasons why the surface modified chalcopyrite exhibited enhanced DCDTP adsorption are discussed.