Regulation of the oil receptivity of the surface of diamonds and kimberlite minerals using various classes of regulating agents

The purpose of the research is to select appropriate agents for regulating the oil receptivity of diamond and kimberlite mineral surfaces in the conditioning of diamond-kimberlite products prior to their beneficiation by froth flotation and X-ray luminescence separation using phosphor-containing modifying agents and collecting agents, the basis of which is apolar collecting agents. The paper presents the results of comprehensive physicochemical studies of the influence of various classes of regulating agents on the attachment of apolar collecting agents on the surface of diamonds and kimberlite minerals (visiometric analysis, measurement of wetting contact angles in a mineral–organic collecting agent–aqueous phase system, measurement of surface tension at the organic collecting agent–aqueous phase–frothless flotation phase boundary). Based on the analysis of the data obtained, effective regulating agents have been identified and selected to ensure the selectivity of diamond beneficiation. Regulating agents belonging to the classes of alkylarylphosphonates (NTPA, OEDPA), aminopolycarboxylic acids (EDTA), cationic polymers (PEG-1500, Neonol AF-9-6), polyphosphates (STPP), bifunctionally modified carboxymethylcellulose derivatives (CMC 75-V and Kamcel-600), mixtures of alkyl phosphates, alkyl phosphonates, and anionic polymers (IS-3), ionogenic and non-ionogenic nitrogen-containing polymers (Emulsifier OP-4, Oxypav A1218.30), amino alcohols (TEA), hydroxy acids (lactic acid), and quaternary ammonium bases (ammonium sulfate) were tested. Talc, pyrite, calcite, muscovite, phlogopite, serpentine, and dolomite were selected as the main minerals of kimberlite prone to adhesion of apolar collecting agents. It has been established that the wetting contact angle is reduced most significantly by the agents Neonol AF-9-6, Emulsifier OP-4, and Oxypav A1218.30 that is associated with a significant decrease in the surface tension of the interface between an organic collecting agent and the aqueous phase. A thermodynamic assessment of the oil receptivity of kimberlite minerals conducted using the Dupré–Young equation and based on measurements of wetting contact angles and surface tension showed that the energy of adhesion of an organic collecting agent on kimberlite minerals with the addition of regulating agents decreases by 2–6 times and reaches values of 6–17 J/m2, approaching the adhesion energy of water (5 J/m2). On diamonds, the energy of adhesion of an apolar collecting agent at maximum concentrations decreases only to 17–27.5 J/m2 that determines its stable attachment. The results of flotation tests confirmed the depressing ability of the studied regulating agents in relation to the flotation-responsing minerals of kimberlite. Based on the analysis of the data obtained, effective regulating agents have been selected and recommended for testing in industrial froth separation modes, ensuring increased selectivity of apolar collecting agent attachment on the surface of diamonds and kimberlite minerals: NTPA, OEDPA, IS-3, OP-4.