Studies On Preparation Of New Flotation Reagents And Structure-Activity Relationship

The studies relate to the discussion of several new flotation depressants as the following: the preparation, the flotation property, the depressing mechanism and the structure-activity relationship.A new type of little molecular weight flotation depressants, phenoxyl poly (acetic acid), was prepared by treating phenol or polyphenol with chloroacetic acid in an alkali solution. Controlling the reaction pH value and developing a new self-sealing method performed a good synthesizing result with high yield and selectivity. A new tert-amine salt, tributylethylammonium ethosulfate, is introduced as the phase transfer catalyst for the reaction, and it can greatly improve the yields of phenoxyl poly (acetic acid). The acidic dissociation constants of the synthesized reagents are determined.Three macromolecule organic depressants, carboxylmethylic poly (vinyl alcohol), carboxylmethylic polyethylene glycol, hydroxamic polyacrylamide, which are abbreviated as CPVA, CPEG, and HPAM respectively, were prepared from poly (vinyl alcohol)(PVA), polyethylene glycol (PEG), and polyacrylamide (PAM). The reaction conditions are optimized, which yield CPVA, CPEG, and HPAM with the degree of substitution (D.S.) 28.3%, 28.4%, and 5.78% respectively.Three pure minerals, i.e. calcite, diaspora and pyrite, are adopted for investigating the flotation properties of the synthesized reagents, which indicate that all the synthesized reagents behave as depressants in the flotation process. The phenoxyl poly (acetic acid) depressants show more effective depressing ability to calcite than to diaspore, and indicate much more weak depressing ability to pyrite. The flotation of manual blending mineral (fluorite with calcite) and some practical ores is consistent with the results. The depressing ability of the macromolecule organic depressants can be improved by the increase of their D.S.. The high D.S. CPVA and CPEG show strong depressing ability to calcite, while CPEG indicates strong depressing ability to diaspore, and HPAM to pyrite.The depressing mechanism of organic depressants was confirmed by the measurements of zeta potential, contact angles, adsorption capacity and IR spectrum. The little molecular weight depressants, phenoxyl poly (acetic acid) depressants, can formstrong chemical reaction on the calcite surface; therefore, they can be adsorbed prior to the collectors, and release the collectors adsorbed on the surface or hold back the adsorption of the collectors. Meanwhile, the macromolecule organic depressants can also be adsorbed on the minerals surface, but they cannot release the collectors adsorbed on the mineral surface or hold back the adsorption of the collectors, and their depressing abilities owe to their long hydrophilic chains.The structure-activity relationships of the organic depressants are discussed by the calculation of electronegativity, reagent specific exponent, hydrophilic lipophilic balance (HLB). It has been shown that the flotation properties of the reagents are identical with the properties affirmed by the classical flotation theories.Quantum chemistry calculation was operated with Zindo/2 Method, by Cerius 2 software on MSI workstation, and the structure-activity relationships of organic depressants were discussed. The ratio of bond charge density, p O-h/ p c-o, was proposed as a standard of the acid intensity for phenoxyl poly (acetic acid) reagents, which was verified by the acidic dissociation constants. The highest occupied molecular orbit (HOMO) and the lowest unoccupied molecular orbit (LUMO) are calculated, and the energy gap of the two orbits determines the activity of the reagents, and yet, in an alkaline solutions for flotation, the HOMOs of the corresponding ions decide the rigidity of the reagents and therefore determine the reaction activity with different rigidity metal cations in minerals, which vary flotation performance to different minerals, and the experimental results were verified.The energy changes of reaction between reagent and mineral reveal that phenoxyl poly (acetic acid) ca...