Mirny Polytechnic Institute (branch), Ammosov North-Eastern Federal University, Yakutsk, Russia:

G. P. Dvoychenkova, Professor, Candidate of Engineering Sciences, dvoigp@mail.ru

One of the causes for the decline in the diamond ore processing performance is alteration of surface properties of diamonds under action of exogenous and supergene processes that lead to formation of mineral films on the surface of crystals. High variability of kimberlites associated with the content of secondary minerals results in reduced recovery of diamonds in sticky and foam separation to 80%, whereas extraction of diamonds from low metamorphic grade kimberlites makes 80–90%. The package of analytical and experimental investigations has proved that hydrophilic diamond crystals unrecoverable in sticky and foam separation have an impaired heterogeneous surface with widespread relief mineral formations caused by the rate of alteration of kimberlites and represented by magnesium silicates, calcium carbonates, magnesium and iron, that form a mechanically strong aggregate on the diamond surface. In some cases, the surface of diamonds is mosaically covered by micro- and macro-size mineral compounds of serpentine-talc type with the high mass fraction of iron. On the basis of thermodynamic calculations, dissolvability of the mineral formations on the diamond surface after modification of physicochemical properties of liquid phase of ore pulp is estimated. A promising way to increasing efficiency of diamond-bearing kimberlite processing is the combination of physical and physicochemical treatment of solid and liquid phase of the slurry in order to lower the rate of coating of the diamond surface with mineral formations, or to ensure the diamond surface clearing. The theoretical and experimental investigations have confirmed the effectiveness of the electrochemical conditioning of circulating water in sticky and foam separation circuits to increase the recovery of diamonds subjected to the intense surface changes. It is shown that the application of the electrochemical conditioning of circulating water in flotation of rebellious diamond ores allows clearing diamonds surface from hydrophilic mineral formations and, consequently, increasing diamond recovery in foam separation concentrate by 5.2% in case of weakly modified kimberlites and by 23.5% in case of heavily modified kimberlites.
This study has been accomplished in the framework of Project No. 0138-2014-002 under scientific guidance of Academician V. A. Chanturia.

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