Role of tannin pretreatment in flotation separation of magnesite and dolomite

Flotation separation of magnesite and its calcium-containing carbonate minerals is a difficult problem.Recently,new regulat-ors have been proposed for magnesite flotation decalcification,although traditional regulators such as tannin,water glass,sodium carbon-ate,and sodium hexametaphosphate are more widely used in industry.However,they are rarely used as the main regulators in research because they perform poorly in magnesite and dolomite single-mineral flotation tests.Inspired by the limonite presedimentation method and the addition of a regulator to magnesite slurry mixing,we used a tannin pretreatment method for separating magnesite and dolomite.Microflotation experiments confirmed that the tannin pretreatment method selectively and largely reduces the flotation recovery rate of dolomite without affecting the flotation recovery rate of magnesite.Moreover,the contact angles of the tannin-pretreated magnesite and dolomite increased and decreased,respectively,in the presence of NaOl.Zeta potential and Fourier transform infrared analyses showed that the tannin pretreatment method efficiently hinders NaOl adsorption on the dolomite surface but does not affect NaOl adsorption on the magnesite surface.X-ray photoelectron spectroscopy and density functional theory calculations confirmed that tannin interacts more strongly with dolomite than with magnesite.

Effect of acid corrosion on the surface roughness and floatability of magnesite and dolomite

To modify surface roughness and improve flotation performance,hydrochloric acid etching pretreatment was performed on magnesite and dolomite.Flotation tests disclosed that acid corrosion improved the flotation kinetics and flotation recovery rates of magnesite and dolomite.Under pulp pH 10 and sodium oleate(NaOl)concentration 20 mg·L^(-1),the flotation recovery rates of magnesite and dolomite after acid etching increased by 31.05%and 29.20%,respectively,compared with those before acid etching.Adsorption density tests proved that the adsorption density of NaOl on magnesite and dolomite was higher after acid etching than before acid etching,implying that acid etching drives Naol adsorption.Zeta potential analysis revealed that acid etching reduces the point of zero charge of magnesite and dolomite.Atomic force microscopy and X-ray photoelectron spectroscopy results demonstrated that acid corrosion modified the surface roughness of magnesite and dolomite,increasing the magnesium(Mg)content on the magnesite surface and the calcium and Mg contents on the dolomite surface.Contact angle measurements indicated that acid corrosion slightly reduced the contact angle between magnesite and dolomite.With Naol present on the surface,the contact angles of magnesite and dolomite after acid etching significantly increased compared with those before acid etching.Therefore,acid etching is effective in improving the floatability of magnesite and dolomite.

Investigation of the flotation behavior and interaction characteristics of micro-fine quartz and magnesite in a dodecylamine system under ultrasonic treatment

Ultrasonic treatment,as an important surface modification method,profoundly affects the flotation behavior of minerals.This study examined the impact of ultrasonic treatment on the surface properties and flotation performance of magnesite and quartz in a dodecylamine(DDA)flotation system.Atomic force microscope detection results revealed that the surface roughness and roughness size of both magnesite and quartz increased after ultrasonic treatment.Flotation tests indicated that the recovery rates of magnesite and quartz were lower after ultrasonic treatment.At pH of 10 and DDA of 75 mg/L,ultrasonic treatment led to a 0.66%,3.46%,and 0.33%decrease in the flotation recovery rates for three different magnesite particle sizes.Following ultrasonic processing,the flotation recovery rates for three different quartz particle sizes decreased by 8.48%,30.76%,and 43.69%,in that order.X-ray photoelectron spectroscopy detection results showed an increased presence of characteristic Mg and Si sites on the surfaces of magnesite and quartz following ultrasonic treatment.DDA acted on the surfaces of the two minerals through electrostatic adsorption and hydrogen bonding adsorption and repelled the flotation of minerals owing to the same charge as characteristic sites,thereby reducing flotation recovery.Adsorption capacity tests and contact angle measurements demonstrated a decrease in DDA adsorption and contact angle on the surfaces of magnesite and quartz after ultrasonic treatment,explaining the reduced floatability.Extended Derjaguin–Landau–Verwey–Overbeek theoretical calculations indicated that before ultrasonic treatment,there was a repulsive energy between magnesite and fine-grained quartz particles.After ultrasonic treatment,the interaction energy between magnesite and fine quartz particles is mutual attraction.