Search

Physicochemical Problems of Mineral Processing; ISSN 2084-4735

The effect of electrolyte on settling behavior of kaolinite was studied. Effects of hard water on selective flocculation of diasporic bauxite was tested and the measures were taken to eliminate the effects of Ca2+ and Mg2+ in hard water. The results indicated that, not only the concentration of electrolyte ions but also the ionic valence of the electrolyte ions affects the settling behavior of kaolinite; hard water significantly affects its selective flocculation owing to Ca2+ and Mg2+; general dispersants could not eliminate the effects of Ca2+ and Mg2+. Self-made softening agent in our lab could weaken or eliminate the effects of hard water on flocculation processes. The results of molecular dynamics simulation show that softening agent molecules could restrict Ca2+ and prevent them from playing their roles, so as to eliminate the effects. The continuous pilot experiment results of bauxite flocculation were even better than those obtained in laboratory.

Aluminum tri-polyphosphate was synthesized from bauxite tailings and phosphoric acid with a P/Al molar ratio of 3. This is highly advantageous from a waste recycling perspective as bauxite tailings are generally regarded as unusable waste. The acidity, whiteness and mean particle size of prepared aluminum tri-polyphosphate are all improved after modification. The possibility of using modified aluminum tri-polyphosphate as an anticorrosive pigment was also investigated by electrochemical impedance spectroscopy. The resistance of the coatings with modified aluminum tri-polyphosphate is 7×107 Ω for 40 d of immersion, which is superior or at least comparable to that of coatings containing APW-2, which exhibits a resistance of 5.7×107 Ω.

The flotation and adsorption behaviors of dodecyltrimethylammonium chloride(DTAC) and cetyltrimethylammonium chloride(CTAC) on diaspore and kaolinite were studied. Solution depletion methods were used to determine adsorption isotherms. Fluorescence probe test along with Zeta potential measurement was also conducted for further investigation into the adsorption of quaternary amines at the mineral-water interface. The results show that the flotation recovery of kaolinite decreases with an increase in pH when DTAC and CTAC are used as collectors, while diaspore is on the contrary. As the carbon chain length of the collectors increases, the flotation recoveries of minerals increase. However, the increment rate of kaolinite is significantly lower than that of diaspore. In the low surfactant concentration range, the cationic surfactants adsorb readily on diaspore surfaces just due to electrostatic interactions. As for kaolinite surfaces, ion exchange process also exists. With a further increase in surfactant concentration, the adsorption was ascribed to the hydrophobic association of chain-chain interactions. Micro-polarity of mineral surfaces study shows that CTAC has a better hydrophobic characteristic than DTAC. Larger aggregates are formed with CTAC on diaspore than on kaolinite in the same solution concentration. The results also indicate that the chain length of cationic surfactants has a greater influence on the adsorption of diaspore than on kaolinite, which is consistent with the flotation result.

The collecting power of tertiary amines (DRN, DEN and DPN) on kaolinite follows the order of DEN>DPN>DRN. After reacting with DRN, DEN and DPN, the surface potentials of kaolinite increase remarkably, and the recruitments caused by collectors also follow the order of DEN>DPN>DRN. The results of dynamics simulation show that the geometries of substituent groups bonding to N are deflected and twisted, and some of bond angles are changed when tertiary amines cations adsorb on kaolinite (001) surface. Based on the results of dynamics simulations and quantum chemistry calculations, the electrostatic forces between three tertiary amines cations and 4×4×3 (001) plane of kaolinite are 1.38×10 −7 N (DRN 12 H + ), 1.44×10 −6 N (DEN 12 H + ), 1.383×10 −6 N (DPN 12 H + ), respectively.

The flotation of diaspore and kaolinite by one of a series of tertiary amines (DRN, DEN, DPN and DBN) was investigated. The tertiary amines show better floating recovery for kaolinite compared to diaspore. The maximum recovery D-value is 45% over a pH range from 3 to 8. FT-IR spectra confirm the presence of hydroxyl groups on the surface of kaolinite and diaspore. Zeta potential measurements show that the mineral surfaces are negatively charged over a wide pH range. Ionization of hydroxyl groups mainly accounts for the surface charging mechanism. The adsorption of tertiary amines onto the mineral surface is due mainly to electrostatic effects and the difference in electrostatic effect between a collector and the two minerals can explain the flotation separation. Inductive electronic and steric effects from the substituent groups result in different collecting powers for the four tertiary amines.

FCLS (Ferric Chromium Lignin Sulfonate) was used to aid the separation of chalcopyrite from marmatite. Flotation, adsorption and zeta-potential tests of treated marmatite and chalcopyrite were performed. The flotation of marmatite was strongly depressed, while that of chalcopyrite was only slightly depressed, over a wide range of pH values when FCLS was used as depressant in the presence of Butyl Xanthate (BX). The adsorption of BX onto chalcopyrite or marmatite takes place over a wide pH range. The adsorption density of BX on chalcopyrite and marmatite decreases as the pH increases. The adsorption density of FCLS onto marmatite is greater than the adsorption density onto chalcopyrite. The zeta potentials of chalcopyrite and marmatite become more negative due to the addition of xanthate and FCLS.

The influence on fine particle aggregation and flotation behavior induced by high intensity conditioning (HIC) from saturated of the slurry with CO 2 saturation was investigated. Bubble size measurements were conducted. The effect of dissolved gas, xanthate addition and agitation speed on fine sphalerite particle aggregation- and flotation-behavior were studied. The results show that during HIC in air or CO 2 saturated water xanthate acts as a frother. The dissolved gas content in the pulp and HIC play a synergistic role in promoting fine particle aggregation and hence flotation; a significantly enhanced aggregation of fine sphalerite particles in a CO 2 saturated slurry by HIC is observed. The aggregate size increased when the agitation speed was increased from 700 r/min to 1500 r/min. Increasing the HIC speed to 1500 r/min caused a positive impact on flotation kinetics. Further increasing the speed to 2000 r/min resulted in an adverse effect on flotation kinetics.