Liuyin Xia

Flotation of aluminosilicate minerals using alkylguanidine collectors

Abstract The flotation mechanism of aluminosilicate minerals using alkylguanidine collectors was studied through flotation experiments, Zeta potential measurements and FT-IR spectrum analysis. It is shown that kaolinite, illite and pyrophyllite all exhibit good floatability with alkylguanidines as collectors at pH 4–12. The flotation recoveries rise with the increase of the carbon chain length. Isoelectric point(IEP) is determined to be 3.5, 3.0 and 2.3 for kaolinite, illite and pyrophyllite, respectively. However, it is anomalous that the presence of cationic collectors has less influence on the negatively charged mineral surfaces. It is explained by the special structure of guanidine which is one of the strongest bases, having two —NH 2 groups. One of them maybe interacts with minerals by electrostatic forces, and the other maybe forms hydrogen bonding with OH − ions on the aluminosilicate surfaces or in the aqueous solution, increasing the density of negative charge on the aluminosilicate surface and leading unpronounced positive charge to increase on the aluminosilicate. By combining the flotation tests, Zeta potential and FTIR measurements above, the interaction mechanism can be concluded. The simultaneous presence of cationic and neutral amine groups makes it possible for SAG cation to bind on three aluminosilicate minerals by both electrostatic attraction and hydrogen bonding. While in acidic medium, the interaction of the alkylguanidines on the aluminosilicate surfaces is mainly by means of electrostatic force and hydrogen bond; in the alkaline medium, it is by the way of electrostatic effect and hydrogen bond.

Comparative studies on flotation of illite, pyrophyllite and kaolinite with Gemini and conventional cationic surfactants

Abstract To search a novel class of effective silicate mineral collectors, the Gemini quaternary ammonium salt surfactant (butane- α , ω -bis(dimethyl dodeculammonium bromide), 12-4-12) and its corresponding conventional monomeric surfactant (dedecyl trimethyl ammonium bromide, DTAB) were adopted to comparatively study the flotation behaviors of illite, pyrophyllite and kaolinite. Three silicate minerals with the Gemini surfactant as collector reveal floatability far better than with the corresponding traditional one. At pH 6, the best recoveries of illite, pyrophyllite and kaolinite with 3.5×10 −4 mol/L 12-4-12 are 99.2%, 91.7% and 99.6%, respectively. The fluorescence and contact angle measurement were also conducted for the further investigation of surfactants aggregation behavior and silicate mineral surface hydrophobic properties. FTIR spectra analysis and electrokinetic analysis show that the mechanism of adsorption of collector molecules on mineral surfaces is almost identical for the electronic attraction and hydrogen bonds effect. The superior collecting power of dimeric collector may be attributed primarily to its special structure and its essential properties.

Flotation techniques for separation of diaspore from bauxite using Gemini collector and starch depressant

The floatability of diaspore and three kinds of silicate minerals, including kaolinite, illite and pyrophyllite, by a cationic Gemini surfactant as collector and starch as depressant was investigated as function of reagents concentration and pulp pH. Further studies of artificially mixed minerals and bauxite ore were also detailedly conducted. At last, the pre-desliming reverse flotation separation process was adopted. It can be concluded that the combinational use of a Gemini cationic collector and the starch depressant is effective. The concentrates with Al2O3 to SiO2 mass ratio of 9.66 and the recovery of Al2O3 of 71.73% are obtained from natural bauxite ore (A/S=5.70) at pH value of around 10.

Comparative studies on flotation of aluminosilicate minerals with Gemini cationic surfactants BDDA and EDDA

Abstract Gemini quaternary ammonium salt surfactants, butane- α, ω -bis(dimethyl dodeculammonium bromide) (BDDA) and ethane- α, β -bis(dimethyl dodeculammonium bromide) (EDDA) were adopted to comparatively study the flotation behaviors of kaolinite, pyrophyllite and illite. It was found that three silicate minerals all exhibited good floatability with Gemini cationic surfactants as collectors over a wide pH range, while BDDA showed a stronger collecting power than EDDA. FTIR spectra and zeta potential analysis indicated that the mechanism of adsorption of Gemini collector molecules on three silicate minerals surfaces was almost identical for the electronic attraction and hydrogen bonds effect. The theoretically obtained results of density functional theory (DFT) at B3LYP/6-31G (d) level demonstrated the stronger collecting power of BDDA presented in the floatation test and zeta potential measurement.

Effect of N-substituents on performance of thiourea collectors by density functional theory calculations

Abstract Using density functional methods, some properties were studied such as the energies and compositions of frontier molecular orbitals and the atomic charges, which are related to the reactive behavior of thioureas containing different N-substituent groupings. The calculation results indicate that the N-substituent groupings have significant effect on the flotation performance of thiourea collectors. The order of electron-donating ability is N-propyl-N′-benzyl-thiourea (PBZYTU)>N-propyl-N′-ethyl-thiourea (PETU) >N-propyl-N′-allyl-thiourea (PALTU)≫ N-propyl-N′-acetyl-thiourea (PACTU) >N-propyl-N′-ethoxycarbonyl-thiourea (PECTU) >N-propyl-N′-benzoyl-thiourea (PBZOYTU), and the order of feedback-electron-accepting ability is PBZOYTU>PACTU>PECTU≫ PALTU>PETU>PBZYTU. This implies that PBZOYTU, PACTU or PECTU can react with copper atoms having (t 2g ) 6 (e g ) 3 Cu(II) or t 6 e 4 Cu(I) configuration on the surfaces of copper sulfide minerals through normal covalent bond and back donation covalent bond, and exhibit excellently collecting performance for copper sulfide minerals. These are consistent with the experimental data reported in the literatures.