Research On Flotation Characteristic Of Micro-fine Dolomite

Magnesium removal as well as poor selectivity and low recovery for micro-fine particles are hard issues in flotation of middle-low grade calcium(magnesium) phosphate ore because phosphate resources is becoming poor, fine and complex as the rich ores run out in China.Research on separation behaviors and mechanism of collophanite and dolomite by flotation for normal particles at size of 75 ?m to 28 ?m has attached much attention but those on micro-fine particles less-than 28 ?m is relatively insufficient. Basic theories of microfine dolomite flotation is considered to be of great theoretical significance for supplement to flotation separation mechanism of collophanite and dolomite and thus can provide theoretical guide for efficient utilization of fine phosphate resources for magnesium removal by flotation.Effects of particle sizes on flotation kinetics and flotation reagents(anionic collector GJBW and sodium oleate, non-polar oil ZK) and calcium and magnesium ions addition on micro-fine pure dolomite flotation behavior were investigated. A series of analysis methods such as Zeta potential, adsorbing capacity, surface tension, induction time of bubble-particle, scan electric microscope, infrared spectrum and photoelectron spectrum as well as molecular simulation were applied to reveal the effect mechanism between flotation reagents and micro-fine dolomite. Results of pure mineral flotation were verified by flotation of artificial mixed minerals of micro-fine collophanite and fine phosphate ore. All above results reveal the separation for micro-fine dolomite and collophanite by flotation. Main conclusions are as follow:First-order kinetic equation showed the highest matched-degree in fitting analysis of flotation kinetics of dolomite. The fitting limitation recovery ?? and flotation rate constant k increase with collector GJBW concentration for all particle sizes. Particles at 45 ?m to 28 ?m shows better floatability with bigger fitting limitation recovery ?? while rougher particles at 150 ?m to 75 ?m and 75 ?m to 45 ?m reach flotation equilibrium quickly with larger flotation rate constant k. Fitting limitation recovery ?? and flotation rate constant k of particles less-than 20 ?m is minimum because of too small size.Effects of mixing time of hydrochloric acid and sulfuric acid on micro-fine dolomite flotation recovery with GJBW as collector were studied and the result showed that the more mixing time, the higher floating ratios. Addition of the collector prior to the acids was proved to be beneficial to the flotation performance. This may be because that the flotability of dolomite can be better when the collector concentration is higher.ZK addition can increase the flotation recovery of micro-fine dolomite and collophane using GJBW, and high intensity slurry mixing can also promote the micro-fine particles for hydrophobic flocculation flotation. But the selectivity of enchancing micro-fine dolomite andcollophane was poor so that it was difficult to promote the separation of the two.The separation selectivity of GJBW on artificial mixed minerals of micro-fine collophanite and dolomite is better than Sodium Oleate. A concentrate with P2O5 grade 30.22% and recovery 88.59% was obtained by reverse flotation using GJBW. The separation ability of GJBW on fine phosphorate ore is also better than Sodium Oleate as concentrate with P2O5 grade 30.66% and recovery 84.18% was obtained by reverse flotation using GJBW.Induction time of dolomite-bubble decreased along with size reduced for size of 150 ?m to 28 ?m and size of 45?m to 28 ?m was minimum. The size less-than 28 ?m reached the maximum indicated that few fine particles can be attached by air bubble. Induction time of dolomite-bubble decreased along with bubble size reduction showed that micro-bubble is more easily to attach on fine particles.The adsorbing capacity of GJBW on micro-fine dolomite increased along with acid consumption while that decreased on micro-fine collophanite. This was supposed to be the reason for effective separation of the two minerals. The difference of adsorbing capacity of GJBW is larger than that of sodium oleate, indicating that the separation selectivity of GJBW is better than sodium oleate. Langmuir single molecular layer adsorption model was found to fit the adsorption isotherm of GJBW on dolomite surface well under acidic condition and the heat of adsorption by calculation was less than the chemical bond energy. This indicated that GJBW adsorption on dolomite surface was physical absorption according to the analysis results of XPS and infrared spectrum.Oleic acid can overcome the hydration shell formed on mineral surface by hydrone and hydroxy to adsorb as the adsorption energy of oleic acid on dolomite and fluorapatite was higher than that of hydrone and hydroxy by molecular modeling calculations. The adsorption ability of oleic acid on dolomite was stronger than on fluorapatite.