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Structure-Performance Of Modified Polymers And The Mechanism For Flotation Of Aluminum And Silicate Minerals

Posted on:2003-05-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:H P LiFull Text:PDF
GTID:1101360125458087Subject:Mineral processing engineering
Abstract/Summary:PDF Full Text Request
The surface properties and flotation behavior of minerals, such as diaspore, kaolinite, pyrophyllite and illite, were investigated by flotation tests, the measurements of zeta potential, adsorption and the infrared spectrumthe, as well as the quantum chemistry calculations of mineral crystals and interaction between minerals and reagents. Several kinds of new high molecular modifiers were synthesized to investigate the effect of these reagents on the flotation of four minerals. Also the reaction mechanism and the structure -performance relationship of the reagents were studied. It has been shown that:(1) The broken surface of diaspore exhibits a good hydrophilic due to the fracture of AI-O bond. The C -potential of mineral surface depends on the selective adsorption of H+ and OH" on cleavage plane, which decreases with the increase of the pH value of media. The isoelectric point is around pH 6.0.Kaolinite, pyrophyllite and illite obtain two kinds of broken surfaces with great difference in properties for their sandwich structure when crushed. Built up by the fracture of Al-O bond and Si-O bond, their {010} surfaces are hydrophilic, which has similar charging mechanism to that of diaspore. Which kind of bonds breaks between layers is determined by the type of mineral crystal structure. As to kaolinite, it is hydrogen bond that breaks, which provides the broken surface with permanent negative charge because of the isomorphic exchange of lattice ion. In the case of pyrophyllite, molecular bond breaks. For illite, both ionic bond and molecular bond break. Moreover, the {001} and {00-1} surfaces of kaolinite, with different chemical constitutions and different charging properties, have different adsorption abilities to dodecyl amine (DDA), which produces impact factor of kaolinite flotation.(2) By oxidation and etherification of industrial starch, carboxymethyl starch, hydroxamic acid starch, cationic starch and dialdehyde starch are prepared. The flotation tests showed that all modified starches have evident depressing effects on diaspore. In acid pulp, the depressing abilities of reagents on diaspore are in the order of hydroxamic acid starch > dialdehyde starch > carboxymethyl starch > cationic starch> primary starch. In addition, hydroxamic acid starch and carboxymethyl starch can activate kaolinite without influence on the recoveries of pyrophyllite and illite, so the twoIVreagents have great potential and prospect to be the depressant of diaspore and the activator of kaolinite in bauxite reverse flotation.(3) By oximation of the copolymer of acrylamide and methyl acrylate, hydroxamic acid polyacrylamide is synthesized. The hydroxamic acid polyacrylamide, nonionic, anionic, cationic and amphoteric ones examined can activate the flotation of diaspore and illite, especially of kaolinite. Being above 80% in wide pH range, the recovery of kaolinite is even higher than that of diaspore at specific pH. At pH=4 about, anionic polyacrylamide exhibits an excellent depressing ability on diaspore, where the recovery of diaspore is 60% lower than that of kaolinite. The application of polyacrylamide greatly reinforces the flotation of kaolinite and shows positive action on bauxite reverse flotation.(4) Each starch reagent has its own mode of action on mineral surface, such as primary starch mainly by hydrogen bond, cationic starch by the co-action of hydrogen bond and electrostatic force (for minerals with negative charge on its surface), while carboxymethyl starch, hydroxamic acid starch and dialdehyde starch principally by chemical force accompanied with hydrogen bond and electrostatic force in part. Such*: chemical forces ensure the close adsorption of reagent on diaspore surface and enforcesthe hydrophilic of mineral surface. Also the branched chain enable the starch to cover the collector adsorbed on mineral surface, so as to depress diaspore furthermore. Among reagents examined, the modified starch that can interact with metallic ion on mineral surface by chemical...
Keywords/Search Tags:bauxite, flotation, organic polymer, modifier, structure-reactivity relationship
PDF Full Text Request
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